Patent Publication Number: US-2023145413-A1

Title: Fast-off rate serum albumin binding fibronectin type iii domains

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. Pat. Application No. 16/748,085, filed Jan. 21, 2020, which is a U.S. divisional of U.S. Pat. Application No. 15/760,413, filed Mar. 15, 2018 (now U.S. Pat. No. 10,766,946), which is a 35 U.S.C. 371 national stage filing of International Application No. PCT/US2016/053183, filed Sep. 22, 2016, which claims priority to U.S. Provisional Application No. 62/222,508, filed Sep. 23, 2015. The contents of the aforementioned applications are hereby incorporated by reference. 
    
    
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on Oct. 24, 2022, is named MXI-545USDV2_SequenceListing_2022-10-24.xml and is 226 kilobytes in size. 
     BACKGROUND 
     Inadequate half-lives of therapeutics often necessitate their administration at high frequencies and/or higher doses, or the use of sustained release formulations, in order to maintain serum levels necessary for therapeutic effects. However, this is often associated with negative side effects. One strategy for overcoming inadequate half-lives is to fuse the therapeutic to a half-life-extending polypeptide. Yet, while the extension of half-life may be beneficial, an overly stabilized therapeutic may also lead to negative side effects. Accordingly, the ability to fine tune the half-lives of therapeutics can be beneficial. This application provides compounds that fine tune the serum half-lives of various therapeutics and methods for generating the same. 
     SUMMARY 
     The invention is based, at least in part, on the development of novel human serum albumin (HSA) binding fibronectin type III tenth ( 10 Fn3) domains which provide versatility in controlling the half-lives of fusion partners (e.g., therapeutic polypeptides). 
     In one aspect, provided herein is a polypeptide comprising a  10 Fn3 domain, wherein the  10 Fn3 domain binds to HSA with a K D  of 1 µM or less and comprises AB, BC, CD, DE, EF, and FG loops, wherein the CD loop has 1, 2, or 3 amino acid substitutions, and the FG loop optionally has 1, 2, or 3 amino acid substitutions, relative to the CD and FG loops of a  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, and wherein the serum half-life of a moiety (e.g., polypeptide) that is linked to the  10 Fn3 domain is extended relative to that of the moiety that is not linked to the  10 Fn3 domain. 
     In certain embodiments, the polypeptide binds to HSA with an off-rate (kd) that is greater than the kd of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. In certain embodiments, the ratio of the off-rate of the polypeptide to the off-rate of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23 is at least about 3. In certain embodiments, the ratio is at least about 25. In certain embodiments, the ratio is at least about 25. In certain embodiments, the ratio is at least about 50. 
     In certain embodiments, the polypeptide binds to HSA with an on-rate (ka) that is within an order of magnitude (i.e., within 10-fold) of the ka of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop has 1 or 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. In certain embodiments, the FG loop has 1 amino acid substitution relative to the FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. In certain embodiments, the CD loop has 1 amino acid substitution and the FG loop has 1 substitution relative to the CD loop and FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop of the  10 Fn3 domain has 1 or 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the 1 or 2 substitutions are selected from the group consisting of:
     (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A.   

     In certain embodiments, the  10 Fn3 domain has 1 or 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, as described above, and/or the  10 Fn3 domain has 1 amino acid substitution relative to the corresponding FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. In certain embodiments, the lysine (K) at position 12 of the FG loop (SEQ ID NO: 29) is substituted with an amino acid selected from A, T, or S. 
     In certain embodiments, the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% identical to the non-CD loop regions of any one of SEQ ID NOs: 23-27, 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, optionally with the proviso that the sequence is not that of ADX_2629_E06. In certain embodiments, the polypeptide comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% identical to any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, optionally with the proviso that the sequence is not that of ADX_2629_E06. 
     In certain embodiments, the  10 Fn3 domain binds to domain I-II of HSA. 
     In certain embodiments, the polypeptides described herein further comprise a heterologous protein, such as a therapeutic moiety (e.g., a  10 Fn3 domain). 
     In certain aspects, provided herein is a composition (e.g., a pharmaceutical composition) comprising a polypeptide comprising any of the HSA binding  10 Fn3 domains or fusion polypeptides comprising such, as described herein, and a carrier (e.g., a pharmaceutically acceptable carrier). 
     In certain aspects, provided herein is an isolated nucleic acid encoding any one of the HSA binding  10 Fn3 domains (e.g., an isolated nucleic acid encoding any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118) or fusion polypeptides comprising such, as described herein, expression vectors comprising the same, and cells comprising the nucleic acid molecules. 
     In certain aspects, provided herein is a method of producing the HSA binding  10 Fn3 domains or fusion polypeptides comprising such, as described herein, comprising culturing the cell comprising the nucleic acid molecules encoding the same under conditions suitable for expressing the  10 Fn3 domains or fusion polypeptides, and purifying the same. 
     In certain aspects, provided herein is a method of enhancing the half-life of a moiety, comprising linking to the moiety a HSA binding  10 Fn3 domain described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS.  1  and  2    are SPR sensograms of Adnectins binding to HSA, normalized at start of dissociation phase to illustrate differences in off-rates of binding. 
         FIGS.  3 A- 3 D  show SPR sensograms of additional Adnectins binding to HSA and mouse serum albumin (MSA), normalized at start of dissociation phase to illustrate differences in off-rates of binding. 
         FIGS.  4 A- 4 D  are SPR kinetics data of the parent Adnectin (ADX_7016_A01; PKE2), and 7016_C03, 7016_E02, and 7016_G01 Adnectins for determining affinities to HSA, MSA, rat serum albumin (rat SA), and cynomolgus serum albumin (cyno SA). 
         FIG.  5    is a graph depicting the plasma half-lives in rats of the parent Adnectin (ADX_7016_A01; PKE2), and 7016_C03, 7016_E02, and 7016_G01 Adnectins. 
         FIG.  6    is a graph depicting the plasma half-lives in mice of the parent Adnectin (ADX_7016_A01; PKE2), and 7016_C03, 7016_E02, and 7016_G01 Adnectins. 
     
    
    
     DETAILED DESCRIPTION 
     Definitions 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by the skilled artisan. Although any methods and compositions similar or equivalent to those described herein can be used in practice or testing of the present invention, the preferred methods and compositions are described herein. 
     A “polypeptide,” as used herein, refers to any sequence of two or more amino acids, regardless of length, post-translation modification, or function. “Polypeptide” and “peptide,” are used interchangeably herein. Polypeptides can include natural amino acids and non-natural amino acids such as those described in U.S. Pat. No. 6,559,126, incorporated herein by reference. Polypeptides can also be modified in any of a variety of standard chemical ways (e.g., an amino acid can be modified with a protecting group; the carboxy-terminal amino acid can be made into a terminal amide group; the amino-terminal residue can be modified with groups to, e.g., enhance lipophilicity; or the polypeptide can be chemically glycosylated or otherwise modified to increase stability or in vivo half-life). Polypeptide modifications can include the attachment of another structure such as a cyclic compound or other molecule to the polypeptide and can also include polypeptides that contain one or more amino acids in an altered configuration (i.e., R or S; or, L or D). 
     A “polypeptide chain”, as used herein, refers to a polypeptide wherein each of the domains thereof is joined to other domain(s) by peptide bond(s), as opposed to non-covalent interactions or disulfide bonds. 
     An “isolated” polypeptide is one that has been identified and separated and/or recovered from a component of its natural environment. Contaminant components of its natural environment are materials that would interfere with diagnostic or therapeutic uses for the polypeptide, and may include enzymes, hormones, and other proteinaceous or nonproteinaceous solutes. In preferred embodiments, the polypeptide will be purified (1) to greater than 95% by weight of polypeptide as determined by the Lowry method, and most preferably more than 99% by weight, (2) to a degree sufficient to obtain at least residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator, or (3) to homogeneity by SDS-PAGE under reducing or nonreducing condition using Coomassie blue or, preferably, silver stain. Isolated polypeptide includes the polypeptide in situ within recombinant cells since at least one component of the polypeptide’s natural environment will not be present. Ordinarily, however, isolated polypeptide will be prepared by at least one purification step. 
     As used herein, a “ 10 Fn3 domain” or “ 10 Fn3 moiety” or “ 10 Fn3 molecule” refers to wild-type  10 Fn3 and biologically active variants thereof, e.g., biologically active variants that specifically bind to a target, such as a target protein. A wild-type human  10 Fn3 domain may comprise the amino acid sequence set forth in SEQ ID NO: 1. Biologically active variants of a wild-type human  10 Fn3 domain include  10 Fn3 domains that comprise at least, at most or about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30, 35, 40 or 45 amino acid changes, i.e., substitutions, additions or deletions, relative to a  10 Fn3 domain comprising SEQ ID NO: 1. 
     A “region” of a  10 Fn3 domain as used herein refers to either a loop (AB, BC, CD, DE, EF and FG), a β-strand (A, B, C, D, E, F and G), the N-terminus (corresponding to amino acid residues 1-8 of SEQ ID NO: 1), or the C-terminus (corresponding to amino acid residues 93-94 of SEQ ID NO: 1) of the human  10 Fn3 domain. 
     A “north pole loop” refers to any one of the BC, DE and FG loops of a fibronectin human fibronectin type 3 tenth ( 10 Fn3) domain. 
     A “south pole loop” refers to any one of the AB, CD and EF loops of a fibronectin human fibronectin type 3 tenth ( 10 Fn3) domain. 
     As used herein, “Adnectin” refers to a  10 Fn3 domain that is modified to specifically bind to a target of interest. 
     A “scaffold region” refers to any non-loop region of a human  10 Fn3 domain. The scaffold region includes the A, B, C, D, E, F and G β-strands as well as the N-terminal region (amino acids corresponding to residues 1-8 of SEQ ID NO: 1) and the C-terminal region (amino acids corresponding to residues 93-94 of SEQ ID NO: 1 and optionally comprising the 7 amino acids constituting the natural linker between the 10 th  and the 11 th  repeat of the Fn3 domain in human fibronectin). 
     “Percent (%) amino acid sequence identity” herein is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in a selected sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN, ALIGN-2 or Megalign (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full-length of the sequences being compared. For purposes herein, however, % amino acid sequence identity values are obtained as described below by using the sequence comparison computer program ALIGN-2. The ALIGN-2 sequence comparison computer program was authored by Genentech, Inc. has been filed with user documentation in the U.S. Copyright Office, Washington D.C., 20559, where it is registered under U.S. Copyright Registration No. TXU510087, and is publicly available through Genentech, Inc., South San Francisco, Calif. The ALIGN-2 program should be compiled for use on a UNIX operating system, preferably digital UNIX V4.0D. All sequence comparison parameters are set by the ALIGN-2 program and do not vary. 
     For purposes herein, the % amino acid sequence identity of a given amino acid sequence A to, with, or against a given amino acid sequence B (which can alternatively be phrased as a given amino acid sequence A that has or comprises a certain % amino acid sequence identity to, with, or against a given amino acid sequence B) is calculated as follows: 100 times the fraction X/Y where X is the number of amino acid residues scored as identical matches by the sequence alignment program ALIGN-2 in that program’s alignment of A and B, and where Y is the total number of amino acid residues in B. It will be appreciated that where the length of amino acid sequence A is not equal to the length of amino acid sequence B, the % amino acid sequence identity of A to B will not equal the % amino acid sequence identity of B to A. 
     The terms “specifically binds,” “specific binding,” “selective binding,” and “selectively binds,” as used interchangeably herein refers to an Adnectin that exhibits affinity for HSA, but does not significantly bind (e.g., less than about 10% binding) to a different polypeptide as measured by a technique available in the art such as, but not limited to, Scatchard analysis and/or competitive binding assays (e.g., competition ELISA, BIACORE assay). The term is also applicable where e.g., a binding domain of an Adnectin of the invention is specific for HSA. 
     The “half-life” of a polypeptide can generally be defined as the time taken for the serum concentration of the polypeptide to be reduced by 50%, in vivo, for example due to degradation of the polypeptide and/or clearance or sequestration of the polypeptide by natural mechanisms. The half-life can be determined in any manner known per se, such as by pharmacokinetic analysis. Suitable techniques will be clear to the person skilled in the art, and may, for example, generally involve the steps of administering a suitable dose of a polypeptide to a primate; collecting blood samples or other samples from said primate at regular intervals; determining the level or concentration of the polypeptide in said blood sample; and calculating, from (a plot of) the data thus obtained, the time until the level or concentration of the polypeptide has been reduced by 50% compared to the initial level upon dosing. Methods for determining half-life may be found, for example, in Kenneth et al., Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists (1986); Peters et al, Pharmacokinetic analysis: A Practical Approach (1996); and “Pharmacokinetics”, M Gibaldi &amp; D Perron, published by Marcel Dekker, 2nd Rev. edition (1982). 
     Half-life can be expressed using parameters such as the t ½ -alpha, t ½ -beta and the area under the curve (AUC). In the present specification, an “increase in half-life” refers to an increase in any one of these parameters, any two of these parameters, or in all three these parameters. In certain embodiments, an increase in half-life refers to an increase in the t1/2-beta, either with or without an increase in the t ½ -alpha and/or the AUC or both. 
     The term “K D ,” as used herein in the context of an Adnectin binding to a protein, refers to the dissociation equilibrium constant of a particular Adnectin-protein interaction or the affinity of an Adnectin for a protein (e.g., HSA), as measured using a surface plasmon resonance assay or a cell binding assay. A “desired K D ,” as used herein, refers to a K D  of an Adnectin that is sufficient for the purposes contemplated. For example, a desired K D  may refer to the K D  of an Adnectin required to elicit a functional effect in an in vitro assay, e.g., a cell-based luciferase assay. 
     The terms “k ass ”, “k on ”, and “ka” are used interchangeably herein, and refer to the association rate constant for the association of an Adnectin into the Adnectin/protein complex. 
     The terms “k diss ”, “k off ”, and “kd” are used interchangeably herein, and refer to the dissociation rate constant for the dissociation of an Adnectin from the Adnectin/protein complex. 
     The term “IC 50 ”, as used herein, refers to the concentration of an Adnectin that inhibits a response, either in an in vitro or an in vivo assay, to a level that is 50% of the maximal inhibitory response, i.e., halfway between the maximal inhibitory response and the untreated response. 
     The term “therapeutically effective amount” refers to an amount of a drug effective to treat a disease or disorder in a mammal and/or relieve to some extent one or more of the symptoms associated with the disorder. 
     As used herein, “preventing” a disease or disorder refers to reducing the probability of occurrence of a disease-state in a statistical sample relative to an untreated control sample, or delaying the onset or reducing the severity of one or more symptoms of the disease or disorder relative to the untreated control sample. Patients may be selected for preventative therapy based on factors that are known to increase risk of suffering a clinical disease state compared to the general population. 
     The term “treating” as used herein includes (a) inhibiting the disease-state, i.e., arresting its development; and/or (b) relieving the disease-state, i.e., causing regression of the disease state once it has been established. 
     As used herein, the term “about” means ±10% of the recited value. 
     Overview 
     The novel fibronectin-based scaffold polypeptides described herein bind to HSA and can be coupled to additional molecule(s), such as other  10 Fn3 domains that bind to different targets, or polypeptides for which increased half-life is beneficial. 
     A. Human Serum Albumin Binding  10 Fn3 domains 
     Fn3 refers to a type III domain from fibronectin. An Fn3 domain is small, monomeric, soluble, and stable. It lacks disulfide bonds and, therefore, is stable under reducing conditions. The overall structure of Fn3 resembles the immunoglobulin fold. Fn3 domains comprise, in order from N-terminus to C-terminus, a beta or beta-like strand, A; a loop, AB; a beta or beta-like strand, B; a loop, BC; a beta or beta-like strand, C; a loop, CD; a beta or beta-like strand, D; a loop, DE; a beta or beta-like strand, E; a loop, EF; a beta or beta-like strand, F; a loop, FG; and a beta or beta-like strand, G. The seven antiparallel β-strands are arranged as two beta sheets that form a stable core, while creating two “faces” composed of the loops that connect the beta or beta-like strands. Loops AB, CD, and EF are located at one face (“the south pole”) and loops BC, DE, and FG are located on the opposing face (“the north pole”). Any or all of loops AB, BC, CD, DE, EF and FG may participate in ligand binding. There are at least 15 different Fn3 modules in human Fibronectin, and while the sequence homology between the modules is low, they all share a high similarity in tertiary structure. 
     In certain embodiments, the Fn3 domain is an Fn3 domain derived from the wild-type tenth module of the human fibronectin type III domain ( 10 Fn3): 
     
       
         
           
               
            
               
                 VSDVPRDLEVVAA TPTS LLISWDAPAVTVRYYRITY GETGGNSPVQE FTVPGSKSTATIS 
               
               
                 GL KPGVD YTITVYAVTGRGDSPASSKPISINYRT (SEQ ID NO: 1) (AB, CD, and EF loops 
               
               
                 are underlined, and BC, DE, and FG loops are bolded). 
               
            
           
         
       
     
     In certain embodiments, the non-ligand binding sequences of  10 Fn3 may be altered provided that the  10 Fn3 retains ligand binding function and/or structural stability. A variety of mutant  10 Fn3 scaffolds have been reported. In one aspect, one or more of Asp 7, Glu 9, and Asp 23 is replaced by another amino acid, such as, for example, a non-negatively charged amino acid residue (e.g., Asn, Lys, etc.). These mutations have been reported to have the effect of promoting greater stability of the mutant  10 Fn3 at neutral pH as compared to the wild-type form (see, e.g., PCT Publication No. WO 02/04523). A variety of additional alterations in the  10 Fn3 scaffold that are either beneficial or neutral have been disclosed. See, for example, Batori et al., Protein Eng 2002;15:1015-20; Koide et al., Biochemistry, 2001;40:10326-33. 
     Both variant and wild-type  10 Fn3 proteins are characterized by the same structure, namely seven beta-strand domain sequences designated A through G and six loop regions (AB loop, BC loop, CD loop, DE loop, EF loop, and FG loop) which connect the seven beta-strand domain sequences. The beta strands positioned closest to the N- and C-termini may adopt a beta-like conformation in solution. In SEQ ID NO: 1, the AB loop corresponds to residues 14-17, the BC loop corresponds to residues 23-31, the CD loop corresponds to residues 37-47, the DE loop corresponds to residues 51-56, the EF loop corresponds to residues 63-67, and the FG loop corresponds to residues 75-87. Much of the variability will generally occur in one or more of the loops. However, it should be understood that not every residue within a loop region needs to be modified in order to achieve a  10 Fn3 binding domain having strong affinity for a desired target. In some embodiments, only residues in a loop, e.g., the CD loop are modified to produce high affinity target binding  10 Fn3 domains. 
     Each of the beta or beta-like strands of a  10 Fn3 polypeptide may consist essentially of an amino acid sequence that is at least 80%, 85%, 90%, 95% or 100% identical to the sequence of a corresponding beta or beta-like strand of any one of SEQ ID NOs: 1, 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, provided that such variation does not disrupt the stability of the polypeptide in physiological conditions. 
     Additionally, insertions and deletions in the loop regions may also be made while still producing HSA binding  10 Fn3 binding domains. Accordingly, in some embodiments, one or more loops selected from AB, BC, CD, DE, EF and FG may be extended or shortened in length relative to the corresponding loop in wild-type human  10 Fn3. In any given polypeptide, one or more loops may be extended in length, one or more loops may be reduced in length, or combinations thereof. In certain embodiments, the length of a given loop may be extended by 2-25, 2-20, 2-15, 2-10, 2-5, 5-25, 5-20, 5-15, 5-10, 10-25, 10-20, or 10-15 amino acids. In certain embodiments, the length of a given loop may be reduced by 1-15, 1-11, 1-10, 1-5, 1-3, 1-2, 2-10, or 2-5 amino acids. 
     In certain embodiments, provided herein are polypeptides comprising a  10 Fn3 domain that specifically binds to HSA with a K D  or 1µM or less, wherein the  10 Fn3 domain comprises AB, BC, CD, DE, and FG loops, and has at least one loop selected from CD and FG loops with an altered amino acid sequence relative to the sequence of the corresponding loop of the human  10 Fn3 domain of SEQ ID NO: 1 or HSA binding  10 Fn3 domain of SEQ ID NO: 23. In some embodiments, the CD and FG loops are altered. In certain embodiments, only the CD loop is altered. In certain embodiments, only the FG loop is altered. In certain embodiments, one or more specific scaffold alterations are combined with one or more loop alterations. By “altered” is meant one or more amino acid sequence alterations relative to a template sequence (i.e., the corresponding wild-type human fibronectin domain or  10 Fn3 domain set forth in SEQ ID NO: 23) and includes amino acid additions, deletions, and substitutions. 
     In certain embodiments, the  10 Fn3 domain has a combination of north and south pole loop alterations. For example, one or more of loops CD and FG, in combination with one or more of loops AB, BC, DE, and EF, can be altered relative to the corresponding loops of the human  10 Fn3 domain of SEQ ID NO: 1 or the HSA binding  10 Fn3 domain of SEQ ID NO: 23. 
     In certain embodiments, the polypeptide comprises a  10 Fn3 domain that comprises an amino acid sequence at least 80, 85, 90, 95, 98, 99, or 100% identical to the non-loop regions and/or non-modified loop regions of any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, wherein at least one loop selected from AB, BC, CD, DE, EF, or FG is altered. For example, in certain embodiments, the AB loop may have up to 4 amino acid substitutions, up to 10 amino acid insertions, up to 3 amino acid deletions, or a combination thereof; the BC loop may have up to 9 amino acid substitutions, up to 4 amino acid insertions, up to 3 amino acid deletions, or a combination thereof; the CD loop may have up to 6 amino acid substitutions, up to 10 amino acid insertions, up to 4 amino acid deletions, or a combination thereof; the DE loop may have up to 6 amino acid substitutions, up to 10 amino acid insertions, up to 4 amino acid deletions, or a combination thereof; the EF loop may have up to 5 amino acid substations, up to 10 amino acid insertions, up to 3 amino acid deletions, or a combination thereof; and/or the FG loop may have up to 12 amino acid substitutions, up to 11 amino acid deletions, up to 25 amino acid insertions, or a combination thereof, relative to the corresponding AB, BC, CD, DE, EF, and/or FG loops of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. 
     In some embodiments, one or more residues of the integrin-binding motif “arginine-glycine-aspartic acid” (RGD) (amino acids 78-80 of SEQ ID NO: 1) may be substituted so as to disrupt integrin binding. In some embodiments, the FG loop of the polypeptides provided herein does not contain an RGD integrin binding site. In certain embodiments, the RGD sequence is replaced by a polar amino acid-neutral amino acid-acidic amino acid sequence (in the N-terminal to C-terminal direction). In certain embodiments, the RGD sequence is replaced with SGE. In yet certain embodiments, the RGD sequence is replaced with RGE. 
     In certain embodiments, the fibronectin based scaffold protein comprises a  10 Fn3 domain that is defined generally by following the sequence: 
     
       
         
           
               
            
               
                 VSDVPRDLEVVAA(X) u LLISW(X) v YRITY(X) w FTV(X) x ATISGL(X) y YTITVYA(X) z ISI 
               
               
                 NYRT (SEQ ID NO: 2) 
               
            
           
         
       
     
     In SEQ ID NO: 2, the AB loop is represented by (X) u , the BC loop is represented by (X) v , the CD loop is represented by (X) w , the DE loop is represented by (X) x , the EF loop is represented by (X) y  and the FG loop is represented by X z . X represents any amino acid and the subscript following the X represents an integer of the number of amino acids. In particular, u, v, w, x, y and z may each independently be anywhere from 2-20, 2-15, 2-10, 2-8, 5-20, 5-15, 5-10, 5-8, 6-20, 6-15, 6-10, 6-8, 2-7, 5-7, or 6-7 amino acids. The sequences of the beta strands (underlined) may have anywhere from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 substitutions, deletions or additions across all 7 scaffold regions relative to the corresponding amino acids shown in SEQ ID NO: 2. In certain embodiments, the sequences of the beta strands may have anywhere from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 conservative substitutions across all 7 scaffold regions relative to the corresponding amino acids shown in SEQ ID NO: 2. In certain embodiments, the hydrophobic core amino acid residues (bolded residues in SEQ ID NO: 2 above) are fixed, and any substitutions, conservative substitutions, deletions or additions occur at residues other than the hydrophobic core amino acid residues. In some embodiments, the hydrophobic core residues of the polypeptides provided herein have not been modified relative to the wild-type human  10 Fn3 domain (SEQ ID NO: 1). 
     In certain aspects, the application provides  10 Fn3 domains with south pole and/or north pole modifications that bind specifically to HSA to prolong the t ½  of a moiety that is linked to the  10 Fn3 domain. 
     HSA has a serum concentration of 600 µM and a t ½  of 19 days in humans. The extended t ½  of HSA has been attributed, in part, to its recycling via the neonatal Fc receptor (FcRn). HSA binds FcRn in a pH-dependent manner after endosomal uptake into endothelial cells; this interaction recycles HSA back into the bloodstream, thereby shunting it away from lysosomal degradation. FcRn is widely expressed and the recycling pathway is thought to be constitutive. In the majority of cell types, most FcRn resides in the intracellular sorting endosome. HSA is readily internalized by a nonspecific mechanism of fluid-phase pinocytosis and rescued from degradation in the lysosome by FcRn. At the acidic pH found in the endosome, HSA’s affinity for FcRn increases (5 µM at pH 6.0). Once bound to FcRn, HSA is shunted away from the lysosomal degradation pathway, transcytosed to and released at the cell surface. 
     North pole-based HSA binding Adnectins are referred to as “first generation” serum albumin binding Adnectins, and are described in, e.g., WO2011140086. In order to improve upon first generation north pole-based serum albumin binding Adnectins (SABAs), of which some did not bind to mouse or rat serum albumin, did not have high affinity for serum albumins across species, and were not always compatible in a multivalent  10 Fn3-based platform, second generation south pole-based HSA binding Adnectins (PKE2 Adnectins) with modified south pole loops were developed (see PCT/US 15/21535, which is specifically incorporated by reference herein in its entirety). One such Adnectin is ADX_7016_A01 (a second generation PKE2 Adnectin), which binds to domain I-II of HSA and has the following core sequence: 
     
       
         
           
               
            
               
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FTVPGSKSTATISGLKPGVDYTIT 
               
               
                 VYA VTGSGESPASSKP ISINYRT (SEQ ID NO: 23; the CD and FG loops are 
               
               
                 underlined) 
               
            
           
         
       
     
     ADX_7016_A01 has low immunogenicity and binds to HSA with a K D  of about 3-6 nM. A fusion polypeptide comprising a heterologous  10 Fn3 domain fused to ADX_7016_A01 has a half-life of about 82 hours in mice. While ADX_7016_A01 substantially extends the half-life of fusion partners, certain situations may call for the fusion partner to have a shorter half-life than that conferred by ADX_7016_A01. 
     Thus, provided herein are polypeptides comprising a  10 Fn3 domain which binds to HSA, wherein the CD and/or FG loop of the  10 Fn3 domain has 1, 2, or 3 amino acid substitutions, and the FG loop optionally 1, 2, or 3 amino acid substitutions relative to the CD and FG loops of a  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the serum half-life of a moiety (e.g., polypeptide) that is linked to the  10 Fn3 domain is extended relative to that of the moiety that is not linked to the  10 Fn3 domain. 
     In certain embodiments, the CD loop has 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop has 1 amino acid substitution relative to the CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the FG loop has 1 amino acid substitution relative to the FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop has 1 amino acid substitution and the FG loop has 1 substitution relative to the CD loop and FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the polypeptide binds to HSA with an off-rate (kd) that is greater than the kd of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Polypeptides comprising a  10 Fn3 domain with an off-rate (kd) that is greater than the kd of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23 are herein referred to as “PKE3” Adnectins. 
     Accordingly, provided herein are polypeptides comprising a  10 Fn3 domain that binds to HSA with a K D  or 1 µM or less, wherein the CD and/or FG loop of the  10 Fn3 domain has 1, 2, or 3 amino acid substitutions, and the FG loop optionally 1, 2, or 3 amino acid substitutions relative to the CD and FG loops of a  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the  10 Fn3 domain binds to HSA with an off-rate (kd) that is greater than the kd of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, and wherein the serum half-life of the polypeptide is extended relative to the polypeptide which lacks the  10 Fn3 domain. 
     In certain embodiments, the ratio of the off-rate of the  10 Fn3 domain to the off-rate of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23 is at least about 2, such as at least about 3, at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 75, at least about 100 or higher. In certain embodiments, the ratio is about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, about 30, about 31, about 32, about 33, about 34, about 35, about 36, about 37, about 38, about 39, about 40, about 41, about 42, about 43, about 44, about 45, about 46, about 47, about 48, about 49, about 50, about 51, about 52, about 53, about 54, about 55, about 56, about 57, about 58, about 59, or about 60. In certain embodiments, the ratio is 1.0, 1.1, 1.2, 3.3, 3.9, 4.0, 4.1, 4.8, 5.0, 5.6, 6.5, 6.6, 8, 11, 14, 17, 20, 23, 28, 28.9, 30.3, 32.0, 34.0, 34.3, 37.3, 50.0, 52, 52.7, 53.0, 56.0, or 79.4. In certain embodiments, the ratio is in the range of 2-100, 2-75, 2-50, 2-45, 2-40, 2-35, 2-30, 2-25, 2-20, 2-15, 2-10, 2-5, 5-100, 5-75, 5-50, 5-45, 5-40, 5-35, 5-30, 5-25, 5-20, 5-15, 5-10, 10-100, 10-75, 10-50, 10-45, 10-40, 10-35, 10-30, 10-25, 10-20, 10-15, 20-100, 20-75, 20-50, 20-45, 20-40, 20-35, 20-30, 20-25, 30-100, 30-75, 30-50, 30-45, 30-40, 30-35, 40-100, 40-75, 40-50, 40-45, 50-100, 50-75, 60-100, 60-75, 70-100, 70-75, 80-100, 80-90, 90-100, 3-4, 3-5, 3-6, 3-7, 25-40, 30-40, 50-55, 75-85, 1-80, 1-70, 1-60, 1-50, 1-40, 1-30, 1-20, 1-10, or 1-5. 
     In certain embodiments, the off-rate of a  10 Fn3 domain binding to HSA is at least 2.5 × 10 -4  s -1 ; 2.5 × 10 -4  s -1 ; 3 × 10 -4  s -1 ; 5 × 10 -4  s -1 ; 10 -3  s -1 ; 3 × 10 -3  s -1 ; 5 × 10 -3  s -1 ; 7 × 10 -3  s -1 ; 10 -2  s -1 ; 3 × 10 -2  s -1 ; or 5 × 10 -2  s -1 . In certain embodiments, the off-rate of a  10 Fn3 domain binding to HSA is in the range of 2.5 × 10 -4  s -1  to 5 × 10 -4  s -1 ; 3 × 10 -4  s -1  to 10 × 10 -4  s -1 ; 5 × 10 -4  s -1  to 10 × 10 -4  s -1 ; 7 × 10 -4  s -1  to 10 × 10 -4  s -1 ; 3 × 10 -4  to 3 × 10 -3  s -1 ; 10 -3  s -1  to 10 -2  s -1 ; or 3 × 10 -4  s -1  to 10 -3  s -1 . 
     In certain embodiments, the polypeptide binds to HSA with an on-rate (ka) that is within about an order of magnitude (i.e., within about 10-fold) of the ka of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Accordingly, provided herein are polypeptides comprising a  10 Fn3 domain that binds to HSA with a K D  or 1 µM or less, wherein the CD and/or FG loop of the  10 Fn3 domain has 1, 2, or 3 amino acid substitutions, and the FG loop optionally 1, 2, or 3 amino acid substitutions relative to the CD and FG loops of a  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the polypeptide binds to HSA with an off-rate (kd) that is greater than the kd of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the polypeptide binds to HSA with an on-rate (ka) that is within about an order of magnitude (i.e., within about 10-fold) of the ka of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, and wherein the serum half-life of a moiety (e.g., polypeptide) that is linked to the  10 Fn3 domain is extended relative to that of the moiety that is not linked to the  10 Fn3 domain. 
     In certain embodiments, the CD loop of the  10 Fn3 domain has 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop of the  10 Fn3 domain has 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the 2 amino acid substitutions are selected from the group consisting of:
     (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A.   

     In certain embodiments, the CD loop of the  10 Fn3 domain has 1 amino acid substitution relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop of the  10 Fn3 domain has 1 amino acid substitution relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the 1 amino acid substitution is selected from the group consisting of:
     (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A.   

     In certain embodiments, the FG loop of the  10 Fn3 domain has 1 amino acid substitution relative to the FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the FG loop of the  10 Fn3 domain has 1 amino acid substitution relative to the FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein the lysine (K) at position 12 of the FG loop (SEQ ID NO: 29) is substituted with an amino acid selected from A, T, or S. 
     In certain embodiments, the CD loop of the  10 Fn3 domain has 1 amino acid substitution and the FG loop has 1 substitution relative to the CD loop and FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, the CD loop of the  10 Fn3 domain has 1 amino acid substitution and the FG loop has 1 substitution relative to the CD loop and FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, wherein
     a) the 1 amino acid substitution in the CD loop selected from the group consisting of 
   (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A; and   
   b) the lysine at position 12 of the FG loop (SEQ ID NO: 29) is substituted with an amino acid selected from A, T, or S.   

     In certain embodiments, the HSA binding  10 Fn3 domains comprises a sequence having at least 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identity to the  10 Fn3 domain comprising the amino acid sequence set forth in any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, or comprise at most 1, 2, 3, 1-2, or 1-3 amino acid difference (i.e., substitution, e.g., deletion, addition or conservative substitution), such as one or more of the amino acid substitutions described herein. In certain embodiments, the HSA binding molecules comprise an amino acid sequence at least 80%, 85%, 90%, 95%, 98%, 99% or 100% identical to the non-CD loop region of SEQ ID NOs: 23-27, 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. 
     In a certain embodiments, the CD loop of the HSA binding  10 Fn3 domains described herein comprises an amino acid sequence selected from the group consisting of: 
     
       
         
           
               
            
               
                 GREVQKYSDLGPLYIYQE (SEQ ID NO: 28), 
               
               
                 GREVQKYSDLGPLYISQE (SEQ ID NO: 35), 
               
               
                 GREVQKYSDTGPLYIYQE (SEQ ID NO: 41), 
               
               
                 GREVQKYSDLGPLYIQQE (SEQ ID NO: 47), 
               
               
                 GREVQKSSDLGPLYIYQE (SEQ ID NO: 59), 
               
               
                 GAEVQKYSDLGPLYIYQE (SEQ ID NO: 64), 
               
               
                 GNEVQKYSDLGPLYIYQE (SEQ ID NO: 69), 
               
               
                 GREVQKYSDLGPAYIYQE (SEQ ID NO: 72), 
               
               
                 GREVQKYSDLGPLYAYQE (SEQ ID NO: 77), 
               
               
                 GREVQKYSDLGPLYIAQE (SEQ ID NO: 80), 
               
               
                 GREVQKYSDLGPLYSYQE (SEQ ID NO: 85), 
               
               
                 GREVDKYSDLGPLYIYQE (SEQ ID NO: 88), 
               
               
                 GREVQKASDLGPLYIYQE (SEQ ID NO: 99), 
               
               
                 GREVQKYSDLGPSYIYQE (SEQ ID NO: 110), and 
               
               
                 GREVQKYSDLGPLYAEQE (SEQ ID NO: 119). 
               
            
           
         
       
     
     In a certain embodiments, the FG loop of the HSA binding  10 Fn3 domains described herein comprises an amino acid sequence selected from the group consisting of:  
     
       
         
           
               
            
               
                 VTGSGESPASSKP (SEQ ID NO: 29), 
               
               
                 VTGSGESPASSAP (SEQ ID NO: 50), 
               
               
                 VTGSGESPASSTP (SEQ ID NO: 53), and 
               
               
                 VTGSGESPASSSP (SEQ ID NO: 56). 
               
            
           
         
       
     
     In certain embodiments, additional regions in the  10 Fn3 domain, such as the β-strand, N-terminal and/or C-terminal regions, may also be modified in sequence relative to SEQ ID NO: 23, 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, and such additional modifications may also contribute to binding to the target. 
     The non binding regions of the HSA binding  10 Fn3 domains described herein may have anywhere from 0 to 20, from 0 to 15, from 0 to 10, from 0 to 8, from 0 to 6, from 0 to 5, from 0 to 4, from 0 to 3, from 0 to 2, or from 0 to 1 substitutions, conservative substitutions, deletions, or additions relative to the scaffold amino acids residues of SEQ ID NO: 1, 23, 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. Such scaffold modifications may be made, so long as the HSA binding  10 Fn3 domain is capable of binding HSA with a desired K D . 
     In certain embodiments, the amino acid sequences of the N-terminal and/or C-terminal regions of the polypeptides provided herein may be modified by deletion, substitution, or insertion relative to the amino acid sequences of the corresponding regions of the wild-type human  10 Fn3 domain (SEQ ID NO: 1). The  10 Fn3 domains generally begin with amino acid number 1 of SEQ ID NO: 1. However, domains with amino acid deletions are also encompassed. 
     Additional sequences may also be added to the N- or C-terminus of a  10 Fn3 domain having the amino acid sequence of any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. For example, in some embodiments, the N-terminal extension consists of an amino acid sequence selected from the group consisting of: M, MG, and G, which may be added to  10 Fn3 domains starting with “VSD” as, e.g., in SEQ ID NO: 1. In exemplary embodiments, an alternative N-terminal region having from 1-20, 1-15, 1-10, 1-8, 1-5, 1-4, 1-3, 1-2, or 1 amino acids in length can be added to the N-terminal region of any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. Exemplary alternative N-terminal regions include (represented by the single letter amino acid code) M, MG, G, MGVSDVPRDL (SEQ ID NO: 3) and GVSDVPRDL (SEQ ID NO: 4). Other suitable alternative N-terminal regions include, for example, X n SDVPRDL (SEQ ID NO: 5), X n DVPRDL (SEQ ID NO: 6), X n VPRDL (SEQ ID NO: 7), X n PRDL (SEQ ID NO: 8) X n RDL (SEQ ID NO: 9), X n DL (SEQ ID NO: 10), or X n L, wherein n = 0, 1 or 2 amino acids, wherein when n = 1, X is Met or Gly, and when n = 2, X is Met-Gly. When a Met-Gly sequence is added to the N-terminus of a  10 Fn3 domain, the M will usually be cleaved off, leaving a G at the N-terminus. In certain embodiments, the alternative N-terminal region comprises the amino acid sequence MASTSG (SEQ ID NO: 11). 
     In exemplary embodiments, an alternative C-terminal region having from 1-20, 1-15, 1-10, 1-8, 1-5, 1-4, 1-3, 1-2, or 1 amino acids in length can be added to the C-terminal region of any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. Specific examples of alternative C-terminal sequences include, for example, polypeptides comprising, consisting essentially of, or consisting of, EIEK (SEQ ID NO: 12), EGSGC (SEQ ID NO: 13), EIEKPCQ (SEQ ID NO: 14), EIEKPSQ (SEQ ID NO: 15), EIEKP (SEQ ID NO: 16), EIEKPS (SEQ ID NO: 17), or EIEKPC (SEQ ID NO: 18). In certain embodiments, the alternative C-terminal region comprises EIDK (SEQ ID NO: 19), and in particular embodiments, the alternative C-terminal region is either EIDKPCQ (SEQ ID NO: 20) or EIDKPSQ (SEQ ID NO: 21). Additional suitable alternative C-terminal regions include those set forth in SEQ ID NOs: 148-172. 
     In certain embodiments, the C-terminal extension sequences comprise E and D residues, and may be between 8 and 50, 10 and 30, 10 and 20, 5 and 10, and 2 and 4 amino acids in length. In certain embodiments, tail sequences include ED-based linkers in which the sequence comprises tandem repeats of ED. In certain embodiments, the tail sequence comprises 2-10, 2-7, 2-5, 3-10, 3-7, 3-5, 3, 4 or 5 ED repeats. In certain embodiments, the ED-based tail sequences may also include additional amino acid residues, such as, for example: EI, EID, ES, EC, EGS, and EGC. Such sequences are based, in part, on known Adnectin tail sequences, such as EIDKPSQ (SEQ ID NO: 21), in which residues D and K have been removed. In certain embodiments, the ED-based tail comprises an E, I or EI residues before the ED repeats. 
     In certain embodiments, an alternative C-terminal moiety, which can be linked to the C-terminal amino acids RT (i.e., corresponding to amino acid 93-94 of SEQ ID NO: 1) of any of the  10 Fn3 domains provided herein comprises the amino acids P m X n , wherein P is proline, X is any amino acid, m is an integer that is at least 1 and n is 0 or an integer that is at least 1. In certain embodiments, the alternative C-terminal moiety comprises the amino acids PC. In certain embodiments, the alternative C-terminal moiety comprises the amino acids PI, PC, PID, PIE, PIDK (SEQ ID NO: 159), PIEK (SEQ ID NO: 160), PIDKP (SEQ ID NO: 161), PIEKP (SEQ ID NO: 162), PIDKPS (SEQ ID NO: 163), PIEKPS (SEQ ID NO: 164), PIDKPC (SEQ ID NO: 165), PIEKPC (SEQ ID NO: 166), PIDKPSQ (SEQ ID NO: 167), PIEKPSQ (SEQ ID NO: 168), PIDKPCQ (SEQ ID NO: 169), PIEKPCQ (SEQ ID NO: 170), PHHHHHH (SEQ ID NO: 171), and PCHHHHHH (SEQ ID NO: 172). 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein comprise, or alternatively lack a 6× his tail. 
     In certain embodiments, the HSA binding  10 Fn3 domains correspond to core  10 Fn3 domains which lack the N-terminal leader and C-terminal tail, as set forth in SEQ ID NOs: 30, 36, 42, 48, 51, 54, 57, 60, 62, 65, 67, 70, 73, 75, 78, 81, 83, 86, 89, 91, 93, 95, 97, 100, 102, 104, 106, 108, 111, 113, 115, and 117. 
     In some embodiments, provided herein are mutant HSA binding  10 Fn3 domains which have a cysteine residue introduced at a specific position to allow or, e.g., chemical conjugation to heterologous moieties (e.g., a heterologous polypeptide such as a  10 Fn3 domain). In preferred embodiments, the cysteine mutations do not substantially alter the binding of the HSA binding  10 Fn3 domain to HSA. 
     In certain embodiments, a proline residue is introduced at the C-terminus of the  10 Fn3 domain, for example, as shown, e.g., in SEQ ID NOs: 33, 34, 39, 40, 45, and 46. The other HSA binding 10Fn3 domains described herein, e.g., those with a core sequence of SEQ ID NOs: 48, 51, 54, 57, 60, 62, 65, 67, 70, 73, 75, 78, 81, 83, 86, 89, 91, 93, 95, 97, 100, 102, 104, 106, 108, 111, 113, 115, and 117, can be modified in a similar manner. In certain embodiments, the proline residue is introduced at the C-terminus of a tandem HSA binding Adnectin. Addition of the proline residue does not preclude the addition of additional amino acid sequences to the C-terminus of an HSA binding  10 Fn3 domain or tandem HSA binding Adnectin. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein bind to HSA with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein may also bind serum albumin from one or more of cynomolgus monkey, rhesus monkey, rat, or mouse. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein bind to rhesus serum albumin (RhSA) or cynomolgus monkey serum albumin (CySA) with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein bind to rhesus serum albumin (RhSA), cynomolgus monkey serum albumin (CySA), and mouse serum albumin (MSA) with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein bind to rhesus serum albumin (RhSA), cynomolgus monkey serum albumin (CySA), mouse serum albumin (MSA), and rat serum albumin (RSA) with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein bind to HSA at a pH range of 5.5 to 7.4. 
     In certain embodiments, the HSA binding  10 Fn3 domains described herein bind to domain I-II of HSA. 
     In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domains described herein or the serum half-life of the HSA binding  10 Fn3 domain linked to a heterologous moiety (e.g., a second  10 Fn3 domain) is at least 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours, 120 hours, 130 hours, 135 hours, 140 hours, 150 hours, 160 hours, or 200 hours. In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domains or the serum half-life of the HSA binding  10 Fn3 domain linked to a heterologous moiety (e.g., a second  10 Fn3 domain) is 2-200 hours, 5-200 hours, 10-200 hours, 25-200 hours, 50-200 hours, 100-200 hours, 150-200 hours, 2-150 hours, 2-100 hours, 2-50 hours, 2-25 hours, 2-10 hours, 2-5 hours, 5-150 hours, 10-100 hours, or 25-50 hours. 
     B. Cross-Competing Adnectins and/or Adnectins That Bind to the Same Adnectin Binding Site 
     Provided herein are proteins, such as Adnectins, antibodies or antigen binding fragments thereof, small molecules, peptides, and the like that compete (e.g., cross-compete) for binding to HSA with the particular HSA binding  10 Fn3 domains described herein, e.g., the HSA binding  10 Fn3 domains (Adnectins) comprising the amino acid sequence set forth in any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. Such competing proteins can be identified based on their ability to competitively inhibit binding to HSA of the serum albumin binding  10 Fn3 domains described herein in standard serum albumin binding assays. For example, standard ELISA assays can be used in which recombinant HSA is immobilized on the plate, one of the proteins is fluorescently labeled and the ability of non-labeled protein to compete off the binding of the labeled protein is evaluated. 
     The following exemplary competition assays are provided in the context of HSA binding  10 Fn3 domains competing for binding to HSA with one of the HSA binding  10 Fn3 domains described herein. The same assays can be performed where a non-Adnectin protein is tested for competition. In one embodiment, a competitive ELISA format can be performed to determine whether two HSA binding Adnectins bind overlapping Adnectin binding sites (epitopes) on HSA. In one format, Adnectin #1 is coated on a plate, which is then blocked and washed. To this plate is added either HSA alone, or HSA pre-incubated with a saturating concentration of Adnectin #2. After a suitable incubation period, the plate is washed and probed with a polyclonal anti-HSA antibody, followed by detection with streptavidin-HRP conjugate and standard tetramethylbenzidine development procedures. If the OD signal is the same with or without preincubation with Adnectin #2, then the two Adnectins bind independently of one another, and their Adnectin binding sites do not overlap. If, however, the OD signal for wells that received serum albumin/Adnectin#2 mixtures is lower than for those that received HSA alone, then binding of Adnectin #2 is confirmed to block binding of Adnectin #1 to HSA. 
     Alternatively, a similar experiment is conducted by surface plasmon resonance (SPR, e.g., BIAcore). Adnectin #1 is immobilized on an SPR chip surface, followed by injections of either HSA alone or HSA pre-incubated with a saturating concentration of Adnectin #2. If the binding signal for HSA/Adnectin#2 mixtures is the same or higher than that of HSA alone, then the two Adnectins bind independently of one another, and their Adnectin binding sites do not overlap. If, however, the binding signal for HSA/Adnectin#2 mixtures is lower than the binding signal for HSA alone, then binding of Adnectin #2 is confirmed to block binding of Adnectin #1 to HSA. A feature of these experiments is the use of saturating concentrations of Adnectin #2. If HSA is not saturated with Adnectin #2, then the conclusions above do not hold. Similar experiments can be used to determine if any two HSA binding proteins bind to overlapping Adnectin binding sites. 
     Both assays exemplified above may also be performed in the reverse order where Adnectin#2 is immobilized and HSA-Adnectin#1 are added to the plate. Alternatively, Adnectin #1 and/or #2 can be replaced with a monoclonal antibody and/or soluble receptor-Fc fusion protein. 
     In certain embodiments, competition can be determined using a HTRF sandwich assay. 
     Candidate competing HSA binding proteins, e.g., Adnectins, can inhibit the binding of the Adnectins described herein to HSA by at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98%, or at least 99%. The % competition can be determined using the methods described above. 
     In certain embodiments, provided herein are Adnectins which bind to the same Adnectin binding site as the HSA binding  10 Fn3 domains described herein. The epitope bound by a particular Adnectin can be determined using art-recognized epitope mapping methods, such as x-ray analyses of crystals of antigen:Adnectin complexes (which provides atomic resolution of the epitope), protease mapping, hydrogen/deuterium exchange mass spectrometry (HDX-MS), 2-dimensional nuclear magnetic resonance, alanine scanning, and deep mutational scanning (see, e.g., Epitope Mapping Protocols in Methods in Molecular Biology, Vol. 66, G. E. Morris, Ed. (1996)). 
     C. Multivalent/Tandem Adnectins 
     Provided herein are multivalent proteins that comprise two or more  10 Fn3 domains, at least one of which binds specifically to HSA. For example, a multivalent protein may comprise 2, 3 or more  10 Fn3 domains that are covalently associated. In certain embodiments, multivalent protein is a bispecific or dimeric protein comprising two  10 Fn3 domains. In certain embodiments, a multivalent protein comprises a first  10 Fn3 domain that binds to HSA (e.g., a  10 Fn3 domain described supra in Section A) and a second  10 Fn3 domain that binds to a second target molecule. When both the first and second target molecules are HSA, the first and second  10 Fn3 domains may bind to the same or different epitopes. Additionally, when the first and second target molecules are the same, the regions of modification in the  10 Fn3 domain that are associated with target binding may be the same or different. 
     In certain embodiments, each  10 Fn3 domain of a multivalent fibronectin-based protein scaffold binds to HSA with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. In exemplary embodiments, each  10 Fn3 domain of a multivalent fibronectin based protein scaffold binds specifically to HSA, i.e., a target not bound by a wild-type  10 Fn3 domain, particularly the wild-type human  10 Fn3 domain. 
     The  10 Fn3 domains in a multivalent fibronectin based scaffold protein may be connected by a polypeptide linker. Exemplary polypeptide linkers include polypeptides having from 1-20, 1-15, 1-10, 1-8, 1-5, 1-4, 1-3, or 1-2 amino acids. Suitable linkers for joining the  10 Fn3 domains are those which allow the separate domains to fold independently of each other forming a three dimensional structure that permits high affinity binding to a target molecule. Specific examples of suitable linkers include glycine-serine based linkers, glycine-proline based linkers, proline-alanine based linkers as well as linkers having the amino acid sequence PSTPPTPSPSTPPTPSPS (SEQ ID NO: 120). In certain embodiments, the linker is a glycine-serine based linker. In certain embodiments, the linker is a glycine-serine based linker. These linkers comprise glycine and serine residues and may be between 8 and 50, 10 and 30, and 10 and 20 amino acids in length. Examples include linkers having an amino acid sequence (GS) 7  (SEQ ID NO: 121), G(GS) 6  (SEQ ID NO: 122), and G(GS) 7 G (SEQ ID NO: 123). Other linkers contain glutamic acid, and include, for example, (GSE) 5  (SEQ ID NO: 124) and GGSEGGSE (SEQ ID NO: 125). Other exemplary glycine-serine linkers include (GS) 4  (SEQ ID NO: 126), (GGGGS) 7  (SEQ ID NO: 127), (GGGGS) 5  (SEQ ID NO: 128), and (GGGGS) 3 G (SEQ ID NO: 129). In some embodiments, the linker is a glycine-proline based linker. These linkers comprise glycine and proline residues and may be between 3 and 30, 10 and 30, and 3 and 20 amino acids in length. Examples include linkers having an amino acid sequence (GP) 3 G (SEQ ID NO: 130), (GP) 5 G (SEQ ID NO: 131), and GPG. In certain embodiments, the linker may be a proline-alanine based linker having between 3 and 30, 10 and 30, and 3 and 20 amino acids in length. Examples of proline alanine based linkers include, for example, (PA) 3  (SEQ ID NO: 132), (PA) 6  (SEQ ID NO: 133) and (PA) 9  (SEQ ID NO: 134). It is contemplated, that the optimal linker length and amino acid composition may be determined by routine experimentation by methods well known in the art. In exemplary embodiments, the linker does not contain any Asp—Lys (DK) pairs. 
     In certain embodiments, the linker has the amino acid sequence PSPEPPTPEP (SEQ ID NO: 135), PSPEPPTPEPPSPEPPTPEP (SEQ ID NO: 136), PSPEPPTPEPPSPEPPTPEPPSPEPPTPEP (SEQ ID NO: 137), or PSPEPPTPEPPSPEPPTPEPPSPEPPTPEPPSPEPPTPEP (SEQ ID NO: 138). Generally a linker may comprise the amino acid sequence (PSPEPPTPEP) n  (SEQ ID NO: 144), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1-5 or 1-10. In certain embodiments, the linker has the amino acid sequence EEEEDE (SEQ ID NO: 139), EEEEDEEEEDE (SEQ ID NO: 140), EEEEDEEEEDEEEEDEEEEDE (SEQ ID NO: 141), EEEEDEEEEDEEEEDEEEEDEEEEDEEEEDE (SEQ ID NO: 142). Generally, a linker may comprise the sequence (EEEEDE) n E (SEQ ID NO: 145), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1-5 or 1-10. In certain embodiments, the linker has the amino acid sequence RGGEEKKKEKEKEEQEERETKTP (SEQ ID NO: 143). Such linkers may be used to connect the HSA binding Adnectin to another polypeptide (e.g., another Adnectin). Exemplary uses of the PSPEPPTPEP (SEQ ID NO: 135) linker is shown below (the “G” after YRTP in SEQ ID NO: 74 and TPEP in SEQ ID NO: 75 is optional). 
     N-terminal Adnectin connected to C-terminal polypeptide:  
     
       
         
           
               
            
               
                 ...NYRTPGPSPEPPTPEP-polypeptide (SEQ ID NO: 146) 
               
            
           
         
       
     
     N-terminal polypeptide connected to C-terminal Adnectin:  
     
       
         
           
               
            
               
                 polypeptide-PSPEPPTPEPGVSDV... (SEQ ID NO: 147) 
               
            
           
         
       
     
     In certain embodiments, the multivalent Adnectin is a tandem Adnectin comprising a first  10 Fn3 domain which binds to HSA (e.g., a PKE3 Adnectin), and a second  10 Fn3 domain that binds to a specific target. Tandem Adnectins may have the configuration HSA binding Adnectin-X and X-HSA binding Adnectin, wherein X is a target specific  10 Fn3 domain. The skilled artisan would be familiar with methods for testing the functional activity and assessing the biophysical properties of such tandem Adnectin molecules. 
     In one aspect, the invention provides a fusion polypeptide comprising a first fibronectin type III tenth ( 10 Fn3) domain and a second  10 Fn3 domain, wherein the first  10 Fn3 domain binds to HSA and comprises AB, BC, CD, DE, EF, and FG loops, wherein the CD loop has 1, 2, or 3 amino acid substitutions, and the FG loop optionally has 1, 2, or 3 amino acid substitutions, relative to the CD and FG loops of a  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23 (e.g., the amino acid substitutions to the CD and/or FG loops described supra in Section A), and wherein the serum half-life of a moiety (e.g., polypeptide) that is linked to the  10 Fn3 domain is extended relative to that of the moiety that is not linked to the  10 Fn3 domain. A “first” domain and a second “domain” may be in the N- to C-terminal or C- to N-terminal orientation. 
     In certain embodiments, the ratio of the off-rate of the first  10 Fn3 domain to the off-rate of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23 is at least about 2, such as at least about 3, at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 75, at least about 100 or higher. In certain embodiments, the ratio is about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, about 30, about 31, about 32, about 33, about 34, about 35, about 36, about 37, about 38, about 39, about 40, about 41, about 42, about 43, about 44, about 45, about 46, about 47, about 48, about 49, about 50, about 51, about 52, about 53, about 54, about 55, about 56, about 57, about 58, about 59, or about 60. In certain embodiments, the ratio is 1.0, 1.1, 1.2, 3.3, 3.9, 4.0, 4.1, 4.8, 5.0, 5.6, 6.5, 6.6, 8, 11, 14, 17, 20, 23, 28, 28.9, 30.3, 32.0, 34.0, 34.3, 37.3, 50.0, 52, 52.7, 53.0, 56.0, or 79.4. In certain embodiments, the ratio is in the range of 2-100, 2-75, 2-50, 2-45, 2-40, 2-35, 2-30, 2-25, 2-20, 2-15, 2-10, 2-5, 5-100, 5-75, 5-50, 5-45, 5-40, 5-35, 5-30, 5-25, 5-20, 5-15, 5-10, 10-100, 10-75, 10-50, 10-45, 10-40, 10-35, 10-30, 10-25, 10-20, 10-15, 20-100, 20-75, 20-50, 20-45, 20-40, 20-35, 20-30, 20-25, 30-100, 30-75, 30-50, 30-45, 30-40, 30-35, 40-100, 40-75, 40-50, 40-45, 50-100, 50-75, 60-100, 60-75, 70-100, 70-75, 80-100, 80-90, 90-100, 3-4, 3-5, 3-6, 3-7, 25-40, 30-40, 50-55, 75-85, 1-80, 1-70, 1-60, 1-50, 1-40, 1-30, 1-20, 1-10, or 1-5. 
     In certain embodiments, the first  10 Fn3 domain binds to HSA with an on-rate (ka) that is within an order of magnitude (i.e., within 10-fold) of the ka of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     In certain embodiments, e.g., of multivalent Adnectins, the first  10 Fn3 domain comprises an amino acid sequence at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identical to any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, or differs therefrom in at most 1, 1-2, 1-5, 1-10 or 1-20 amino acids (e.g., amino acid deletions, additions or substitutions (e.g., conservative amino acid substitutions), such as one or more of the amino acid substitutions described herein). 
     In certain embodiments, the first  10 Fn3 domain comprises the amino acid sequence of any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. 
     In some embodiments, the multivalent Adnectin comprises a second  10 Fn3 domain that is a  10 Fn3 domain that specifically binds to a target protein other than HSA, e.g., a target protein (e.g., therapeutic moiety) described infra in Section D. 
     In one aspect, the HSA binding tandem Adnectins described hererin bind to HSA with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding tandem Adnectins described herein may also bind serum albumin from one or more of cynomolgus monkey, rhesus monkey, rat, or mouse. 
     In certain embodiments, the HSA binding tandem Adnectins described herein bind to rhesus serum albumin (RhSA) or cynomolgus monkey serum albumin (CySA) with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding tandem Adnectins described herein bind to rhesus serum albumin (RhSA), cynomolgus monkey serum albumin (CySA), and mouse serum albumin (MSA) with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding tandem Adnectins described herein bind to rhesus serum albumin (RhSA), cynomolgus monkey serum albumin (CySA), mouse serum albumin (MSA), and rat serum albumin (RSA) with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM, or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM, 1 nM to 1 µM, 50 nM to 3 µM, 50 nM to 2 µM, 50 nM to 1 µM, 50 nM to 500 nM, 50 nM to 100 nM, 100 nM to 3 µM, 100 nM to 2 µM, 100 nM to 1 µM, 250 nM to 3 µM, 250 nM to 2 µM, 250 nM to 1 µM, 250 nM to 500 nM, 500 nM to 3 µM, 500 nM to 2 µM, 500 nM to 1 µM, 1 µM to 3 µM, or 1 µM to 2 µM. 
     In certain embodiments, the HSA binding tandem Adnectins described herein bind to serum albumin at a pH range of 5.5 to 7.4. 
     In certain embodiments, the HSA binding tandem Adnectins described herein bind to domain I-II of HSA. 
     In certain embodiments, the HSA binding tandem Adnectins described herein has a serum half-life in the presence of HSA, cynomolgus monkey serum albumin, rhesus monkey serum albumin, mouse serum albumin, and/or rat serum albumin of at least 1 hour, 2 hours, 5 hours, 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 150 hours, 200 hours, or at least about 300 hours. 
     In certain embodiments, the HSA binding tandem Adnectins described herein has a serum half-life in the presence of HSA, cynomolgus monkey serum albumin, rhesus monkey serum albumin, mouse serum albumin, and/or rat serum albumin of 1-300 hours, such as 1-250 hours, 1-200 hours, 1-150 hours, 1-100 hours, 1-90 hours, 1-80 hours, 1-70 hours, 1-60 hours, 1-50 hours, 1-40 hours, 1-30 hours, 1-20 hours, 1-10 hours, 1-5 hours, 5-300 hours, 10-300 hours, 20-300 hours, 30-300 hours, 40-300 hours, 50-300 hours, 60-300 hours, 70-300 hours, 80-300 hours, 90-300 hours, 100-300 hours, 150-300 hours, 200-300 hours, 250-300 hours, 5-250 hours, 10-200 hours, 50-150 hours, or 80-120 hours. 
     In certain embodiments, the serum half-life of the partner Adnectin in the HSA binding tandem Adnectin is increased relative to the serum half-life of the partner Adnectin when not conjugated to the HSA binding Adnectin. 
     In certain embodiments, the serum half-life of the HSA binding tandem Adnectin is at least 20, 40, 60, 80, 100, 120, 150, 180, 200, 400, 600, 800, 1000, 1200, 1500, 1800, 1900, 2000, 2500, or 3000% longer relative to the serum half-life of the partner Adnectin when not fused to the HSA binding Adnectin. 
     In certain embodiments, the serum half-life of the HSA binding tandem Adnectin is 20-3000%, such as 40-3000%, 60-3000%, 80-3000%, 100-3000%, 120-3000%, 150-3000%, 180-3000%, 200-3000%, 400-3000%, 600-3000%, 800-3000%, 1000-3000%, 1200-3000%, 1500-3000%, 1800-3000%, 1900-3000%, 2000-3000%, 2500-3000%, 20-2500%, 20-2000%, 20-1900%, 20-1800%, 20-1500%, 20-1200%, 20-1000%, 20-800%, 20-600%, 20-400%, 20-200%, 20-180%, 20-150%, 20-120%, 20-100%, 20-80%, 20-60%, 20-40%, 50-2500%, 100-2000%, 150-1500%, 200-1000%, 400-800%, or 500-700% longer relative to the serum half-life of the partner Adnectin when not fused to the HSA binding Adnectin. 
     In certain embodiments, the serum half-life of the HSA binding tandem Adnectin is at least 1.5-fold, 2-fold, 2.5-fold, 3-fold, 3.5 fold, 4-fold, 4.5- fold, 5-fold, 6-fold, 7-fold, 8-fold, 10-fold, 12-fold, 13-fold, 15-fold, 17-fold, 20-fold, 22-fold, 25 -fold, 27-fold, 30-fold, 35 -fold, 40-fold, or 50-fold greater than the serum half-life of the partner Adnectin when not fused to the HSA binding Adnectin. 
     In certain embodiments, the serum half-life of the HSA binding tandem Adnectin is 1.5-50 fold, such as 1.5-40 fold, 1.5-35 fold, 1.5-30 fold, 1.5-27 fold, 1.5-25 fold, 1.5-22 fold, 1.5-20 fold, 1.5-17 fold, 1.5-15 fold, 1.5-13 fold, 1.5-12 fold, 1.5-10 fold, 1.5-9 fold, 1.5-8 fold, 1.5-7 fold, 1.5-6 fold, 1.5-5 fold, 1.5-4.5 fold, 1.5-4 fold, 1.5-3.5 fold, 1.5-3 fold, 1.5-2.5 fold, 1.5-2 fold, 2-50 fold, 2.5-50 fold, 3-50 fold, 3.5-50 fold, 4-50 fold, 4.5-50 fold, 5-50 fold, 6-50 fold, 7-50 fold, 8-50 fold, 10-50 fold, 12-50 fold, 13-50 fold, 15-50 fold, 17-50 fold, 20-50 fold, 22-50 fold, 25-50 fold, 27-50 fold, 30-50 fold, 40-50 fold, 2-40 fold, 5-35 fold, 10-20 fold, or 10-15 fold greater than the serum half-life of the partner Adnectin when not fused to the HSA binding Adnectin. 
     In certain embodiments, the serum half-life of the HSA binding tandem Adnectin is at least 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours, 120 hours, 130 hours, 135 hours, 140 hours, 150 hours, 160 hours, or 200 hours. 
     In certain embodiments, the serum half-life of the HSA binding tandem Adnectin is 2-200 hours, 2.5-200 hours, 3-200 hours, 4-200 hours, 5-200 hours, 6-200 hours, 7-200 hours, 8-200 hours, 9-200 hours, 10-200 hours, 15-200 hours, 20-200 hours, 25-200 hours, 30-200 hours, 35-200 hours, 40-200 hours, 50-200 hours, 60-200 hours, 70-200 hours, 80-200 hours, 90-200 hours, 100-200 hours, 125-200 hours, 150-200 hours, 175-200 hours, 190-200 hours, 2-190 hours, 2-175 hours, 2-150 hours, 2-125 hours, 2-100 hours, 2-90 hours, 2-80 hours, 2-70 hours, 2-60 hours, 2-50 hours, 2-40 hours, 2-35 hours, 2-30 hours, 2-25 hours, 2-20 hours, 2-15 hours, 2-10 hours, 2-9 hours, 2-8 hours, 2-7 hours, 2-6 hours, 2-5 hours, 2-4 hours, 2-3 hours, 5-175 hours, 10-150 hours, 15-125 hours, 20-100 hours, 25-75 hours, or 30-60 hours. 
     D. Conjugates of HSA Binding Adnectins 
     Certain aspects of the present invention provide for conjugates comprising a HSA binding  10 Fn3 domain (e.g., as described supra in Sections A and B) and at least one additional moiety (e.g., a therapeutic moiety). The additional moiety may be useful for any diagnostic, imaging, or therapeutic purpose. 
     In some embodiments, the HSA binding  10 Fn3 domain is fused to a second moiety that is a small organic molecule, a nucleic acid, a peptide, or a protein. 
     In certain embodiments, the HSA binding  10 Fn3 domain is fused to a therapeutic moiety that targets receptors, receptor ligands, viral coat proteins, immune system proteins, hormones, enzymes, antigens, or cell signaling proteins. The fusion may be formed by attaching the second moiety to either end of the HSA binding  10 Fn3 domain, i.e., HSA binding  10 Fn3 domain-therapeutic molecule or therapeutic molecule-HSA binding  10 Fn3 domain arrangements. 
     In certain embodiments, the serum half-life of a moiety (e.g., polypeptide) that is linked to the  10 Fn3 domain is extended relative to that of the moiety that is not linked to the  10 Fn3 domain. In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domain fusion is at least 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 150, 180, 200, 400, 600, 800, 1000, 1200, 1500, 1800, 1900, 2000, 2500, or 3000% longer relative to the serum half-life of the moiety when not fused to the  10 Fn3 domain. In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domain fusion is 5-3000%, such as 10-3000%, 15-3000%, 20-3000%, 30-3000%, 40-3000%, 50-3000%, 60-3000%, 70-3000%, 80-3000%, 90-3000%, 100-3000%, 120-3000%, 150-3000%, 180-3000%, 200-3000%, 400-3000%, 600-3000%, 800-3000%, 1000-3000%, 1200-3000%, 1500-3000%, 1800-3000%, 1900-3000%, 2000-3000%, 2500-3000%, 20-2500%, 20-2000%, 20-1900%, 20-1800%, 20-1500%, 20-1200%, 20-1000%, 20-800%, 20-600%, 20-400%, 20-200%, 20-180%, 20-150%, 20-120%, 20-100%, 20-80%, 20-60%, 20-40%, 10-2000%, 10-1900%, 10-1800%, 10-1500%, 10-1200%, 10-1000%, 10-800%, 10-600%, 10-400%, 10-200%, 10-180%, 10-150%, 10-120%, 10-100%, 10-80%, 10-60%, 10-40%, 10-20%, 5-2000%, 5-1900%, 5-1800%, 5-1500%, 5-1200%, 5-1000%, 5-800%, 5-600%, 5-400%, 5-200%, 5-180%, 5-150%, 5-120%, 5-100%, 5-80%, 5-60%, 5-40%, 5-20%, 5-15%, 5-10%, 50-2500%, 100-2000%, 150-1500%, 200-1000%, 400-800%, or 500-700% longer relative to the serum half-life of the moiety when not fused to the  10 Fn3 domain. 
     In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domain fusion is at least 1.1-fold, 1.2-fold, 1.3-fold, 1.4-fold, 1.5-fold, 1.6-fold, 1.7-fold, 1.8-fold, 1.9-fold, 2-fold, 2.5-fold, 3-fold, 3.5 fold, 4-fold, 4.5-fold, 5-fold, 6-fold, 7-fold, 8-fold, 10-fold, 12-fold, 13-fold, 15-fold, 17-fold, 20-fold, 22-fold, 25-fold, 27-fold, 30-fold, 35-fold, 40-fold, or 50-fold greater than the serum half-life of the moiety when not fused to the  10 Fn3 domain. 
     In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domain fusion is 1.5-50 fold, such as 1.5-40 fold, 1.5-35 fold, 1.5-30 fold, 1.5-27 fold, 1.5-25 fold, 1.5-22 fold, 1.5-20 fold, 1.5-17 fold, 1.5-15 fold, 1.5-13 fold, 1.5-12 fold, 1.5-10 fold, 1.5-9 fold, 1.5-8 fold, 1.5-7 fold, 1.5-6 fold, 1.5-5 fold, 1.5-4.5 fold, 1.5-4 fold, 1.5-3.5 fold, 1.5-3 fold, 1.5-2.5 fold, 1.5-2 fold, 2-50 fold, 2.5-50 fold, 3-50 fold, 3.5-50 fold, 4-50 fold, 4.5-50 fold, 5-50 fold, 6-50 fold, 7-50 fold, 8-50 fold, 10-50 fold, 12-50 fold, 13-50 fold, 15-50 fold, 17-50 fold, 20-50 fold, 22-50 fold, 25-50 fold, 27-50 fold, 30-50 fold, 40-50 fold, 2-40 fold, 5-35 fold, 10-20 fold, or 10-15 fold greater than the serum half-life of the moiety when not fused to the  10 Fn3 domain. 
     In certain embodiments, the serum half-life of the HSA binding  10 Fn3 domain fusion is at least 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours, 120 hours, 130 hours, 135 hours, 140 hours, 150 hours, 160 hours, or 200 hours. In certain embodiments, the serum half-life of the HSA binding Adnectin fusion is 2-200 hours, 2.5-200 hours, 3-200 hours, 4-200 hours, 5-200 hours, 6-200 hours, 7-200 hours, 8-200 hours, 9-200 hours, 10-200 hours, 15-200 hours, 20-200 hours, 25-200 hours, 30-200 hours, 35-200 hours, 40-200 hours, 50-200 hours, 60-200 hours, 70-200 hours, 80-200 hours, 90-200 hours, 100-200 hours, 125-200 hours, 150-200 hours, 175-200 hours, 190-200 hours, 2-190 hours, 2-175 hours, 2-150 hours, 2-125 hours, 2-100 hours, 2-90 hours, 2-80 hours, 2-70 hours, 2-60 hours, 2-50 hours, 2-40 hours, 2-35 hours, 2-30 hours, 2-25 hours, 2-20 hours, 2-15 hours, 2-10 hours, 2-9 hours, 2-8 hours, 2-7 hours, 2-6 hours, 2-5 hours, 2-4 hours, 2-3 hours, 5-175 hours, 10-150 hours, 15-125 hours, 20-100 hours, 25-75 hours, or 30-60 hours. 
     In certain embodiments, the HSA binding  10 Fn3 domain fusion proteins bind to HSA with a K D  of less than 3 µM, 2.5 µM, 2 µM, 1.5 µM, 1 µM, 500 nM, 100 nM, 50 nM, 10 nM, 1 nM, 500 pM, 100 pM, 100 pM, 50 pM or 10 pM. The K D  may be, e.g., in the range of 0.1 nM to 50 nM, 0.1 nM to 100 nM, 0.1 nM to 1 µM, 0.5 nM to 50 nM, 0.5 nM to 100 nM, 0.5 nM to 1 µM, 1 nM to 50 nM, 1 nM to 100 nM or 1 nM to 1 µM. 
     In certain embodiments, a therapeutic moiety may be directly or indirectly linked to a HSA binding  10 Fn3 domain, e.g., via a polymeric linker, as described herein (e.g., a linker as described supra in Section C). Polymeric linkers can be used to optimally vary the distance between each component of the fusion to create a protein fusion with one or more of the following characteristics: 1) reduced or increased steric hindrance of binding of one or more protein domains when binding to a protein of interest, 2) increased protein stability or solubility, 3) decreased protein aggregation, and 4) increased overall avidity or affinity of the protein. 
     Any of the linkers for linking two Adnectins, e.g., those described in Section C herein, may be used for linking an Adnectin to a heterologous moiety, such as a polypeptide. 
     In certain embodiments, a moiety, e.g., a polypeptide, is linked to a HSA binding Adnectin via a polypeptide linker having a protease site that is cleavable by a protease in the blood or target tissue. Such embodiments can be used to release a therapeutic protein for better delivery or therapeutic properties or more efficient production. 
     Additional linkers or spacers may be introduced at the C-terminus of a  10 Fn3 domain between the  10 Fn3 domain and the polypeptide linker. 
     In certain embodiments, a therapeutic moiety is linked to a HSA binding  10 Fn3 domain via a biocompatible polymer such as a polymeric sugar. The polymeric sugar can include an enzymatic cleavage site that is cleavable by an enzyme in the blood or target tissue. Such embodiments can be used to release therapeutic proteins for better delivery or therapeutic properties or more efficient production. 
     The HSA binding  10 Fn3 domain fusion molecules described herein are useful for increasing the half-life of a therapeutic moiety by creating a fusion between the therapeutic moiety and the HSA binding  10 Fn3 domain. Such fusion molecules may be used to treat conditions which respond to the biological activity of the therapeutic moiety contained in the fusion. Thus, provided herein is the use of the HSA binding  10 Fn3 domain fusion molecules in diseases caused by the disregulation of any of the following proteins or molecules. 
     In certain embodiments, the therapeutic moiety that is linked (either C-terminal or N-terminal) to the HSA binding  10 Fn3 domain is VEGF, VEGF-R1, VEGF-R2, VEGF-R3, Her-1, Her-2, Her-3, EGF-I, EGF-2, EGF-3, Alpha3, cMet, ICOS, CD40L, LFA-I, c-Met, ICOS, LFA-I, IL-6, B7.1, W1.2, OX40, IL-1b, TACI, IgE, BAFF or BLys, TPO-R, CD19, CD20, CD22, CD33, CD28, IL-I-R1, TNF-alpha, TRAIL-R1, Complement Receptor 1, FGFa, Osteopontin, Vitronectin, Ephrin A1-A5, Ephrin B1-B3, alpha-2-macroglobulin, CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CXCL8, CXCL9, CXCL10, CXCL11, CXCL12, CCL13, CCL14, CCL15, CXCL16, CCL16, CCL17, CCL18, CCL19, CCL20, CCL21, CCL22, PDGF, TGFb, GMCSF, SCF, p40 (IL12/IL23), IL1b, IL1a, IL1ra, IL2, IL3, IL4, IL5, IL6, IL8, IL1O, IL12, IL15, IL23, Fas, FasL, Flt3 ligand, 41BB, ACE, ACE-2, KGF, FGF-7, SCF, Netrin1,2, IFNa,b,g, Caspase-2,3,7,8,10, ADAM S1,S5,8,9,15,TS1,TS5; Adiponectin, ALCAM, ALK-I, APRIL, Annexin V, Angiogenin, Amphiregulin, Angiopoietin-1,2,4, B7-⅟CD80, B7-2/CD86, B7-H1, B7-H2, B7-H3, Bcl-2, BACE-I, BAK, BCAM, BDNF, bNGF, bECGF, BMP2,3,4,5,6,7,8; CRP, Cadherin 6, 8, 11; Cathepsin A,B,C,D,E,L,S,V,X; CD1 1a/LFA-1, LFA-3, GP2b3a, GH receptor, RSV F protein, IL-23 (p40, p19), IL-12, CD80, CD86, CD28, CTLA-4, alpha4-beta1, alpha4-beta7, TNF/Lymphotoxin, IgE, CD3, CD20, IL-6, IL-6R, BLYS/BAFF, IL-2R, HER2, EGFR, CD33, CD52, Digoxin, Rho (D), Varicella, Hepatitis, CMV, Tetanus, Vaccinia, Antivenom, Botulinum, Trail-R1, Trail-R2, cMet, TNF-R family, such as LA NGF-R, CD27, CD30, CD40, CD95, Lymphotoxin a/b receptor, WsI-I, TL1A/TNFSF15, BAFF, BAFF-R/TNFRSF13C, TRAIL R2/TNFRSF10B, TRAIL R2/TNFRSF10B, Fas/TNFRSF6 CD27/TNFRSF7, DR3/TNFRSF25, HVEM/TNFRSF14, TROY/TNFRSF19, CD40 Ligand/TNFSF5, BCMA/TNFRSF17, CD30/TNFRSF8, LIGHT/TNFSF14, 4-1BB/TNFRSF9, CD40/TNFRSF5, GITR/[Gamma]NFRSF 18, Osteoprotegerin/TNFRSF1 IB, RANK/TNFRSF1 IA, TRAIL R3/TNFRSF10C, TRAIL/TNFSFIO, TRANCE/RANK L/TNFSF11, 4-1BB Ligand/TNFSF9, TWEAK/TNFSF12, CD40 Ligand/TNFSFS, Fas Ligand/TNFSF6, RELT/TNFRSF19L, APRIL/TNFSF13, DcR3/TNFRSF6B, TNF RI/TNFRSFIA, TRAIL R1/TNFRSFIOA, TRAIL R4/TNFRSF10D, CD30 Ligand/TNFSF8, GITR Ligand/TNFSF18, TNFSF18, TACI/TNFRSF13B, NGF R/TNFRSF16, OX40 Ligand/TNFSF4, TRAIL R2/TNFRSF10B, TRAIL R3/TNFRSF10C, TWEAK R/TNFRSF12, BAFF/BLyS/TNFSF13, DR6/TNFRSF21, TNF-alpha/TNFSF1 A, Pro-TNF-alpha/TNFSF1A, Lymphotoxin beta R/TNFRSF3, Lymphotoxin beta R (LTbR)/Fc Chimera, TNF RI/TNFRSFIA, TNF-beta/TNFSF1B, PGRP-S, TNF RI/TNFRSFIA, TNF RII/TNFRSFIB, EDA-A2, TNF-alpha/TNFSFIA, EDAR, XEDAR, TNF RI/TNFRSFIA. 
     In certain embodiments, the therapeutic moiety that is linked (either C-terminal or N-terminal) to the HSA binding  10 Fn3 domain is any of the following proteins or proteins binding thereto: 4EBP1, 14-3-3 zeta, 53BP1, 2B4/SLAMF4, CCL21/6Ckine, 4-1BB/TNFRSF9, 8D6A, 4-1BB Ligand/TNFSF9, 8-oxo-dG, 4-Amino-1,8-naphthalimide, A2B5, Aminopeptidase LRAP/ERAP2, A33, Aminopeptidase N/ANPEP, Aag, Aminopeptidase P2/XPNPEP2, ABCG2, Aminopeptidase P1/XPNPEP1, ACE, Aminopeptidase PILS/ARTS1, ACE-2, Amnionless, Actin, Amphiregulin, beta-Actin, AMPK alpha ½, Activin A, AMPK alpha 1, Activin AB, AMPK alpha 2, Activin B, AMPK beta 1, Activin C, AMPK beta 2, Activin RIA/ALK-2, Androgen R/NR3C4, Activin RIB/ALK-4, Angiogenin, Activin RIIA, Angiopoietin-1, Activin RIIB, Angiopoietin-2, ADAMS, Angiopoietin-3, ADAM9, Angiopoietin-4, ADAM1O, Angiopoietin-like 1, ADAM12, Angiopoietin-like 2, ADAM15, Angiopoietin-like 3, TACE/ADAM17, Angiopoietin-like 4, ADAM19, Angiopoietin-like 7/CDT6, ADAM33, Angiostatin, ADAMTS4, Annexin A1/Annexin I, ADAMTS5, Annexin A7, ADAMTS1, Annexin A10, ADAMTSL-1/Punctin, Annexin V, Adiponectin/Acrp30, ANP, AEBSF, AP Site, Aggrecan, APAF-I, Agrin, APC, AgRP, APE, AGTR-2, APJ, AIF, APLP-I, Akt, APLP-2, Akt1, Apolipoprotein AI, Akt2, Apolipoprotein B, Akt3, APP, Serum Albumin, APRIL/TNFSF13, ALCAM, ARC, ALK-I, Artemin, ALK-7, Arylsulfatase AJARSA, Alkaline Phosphatase, ASAH2/N-acylsphingosine Amidohydrolase-2, alpha 2u-Globulin, ASC, alpha-1-Acid Glycoprotein, ASGR1, alpha-Fetoprotein, ASK1, ALS, ATM, Ameloblastic ATRIP, AMICA/JAML, Aurora A, AMIGO, Aurora B, AMIG02, Axin-1, AMIG03, AxI, Aminoacylase/ACY1, Azurocidin/CAP37/HBP, Aminopeptidase A/ENPEP, B4GALT1, BIM, B7-1/CD80, 6-Biotin-17-NAD, B7-2/CD86, BLAME/SLAMF8, B7-H1/PD-L1, CXCL13/BLC/BCA-1, B7-H2, BLIMP1, B7-H3, BIk, B7-H4, BMI-I, BACE-I, BMP-1/PCP, BACE-2, BMP-2, Bad, BMP-3, BAFF/TNFSF13B, BMP-3b/GDF-10, BAFF R/TNFRSF 13C, BMP-4, Bag-1, BMP-5, BAK, BMP-6, BAMBI/NMA, BMP-7, BARD 1, BMP-8, Bax, BMP-9, BCAM, BMP-10, Bcl-10, BMP-15/GDF-9B, Bcl-2, BMPR-IA/ALK-3, Bcl-2 related protein A1, BMPR-IB/ALK-6, Bcl-w, BMPR-II, Bcl-x, BNIP3L, Bcl-xL, BOC, BCMA/TNFRSF17, BOK, BDNF, BPDE, Benzamide, Brachyury, Common beta Chain, B-Raf, beta IG-H3, CXCL14/BRAK, Betacellulin, BRCA1, beta-Defensin 2, BRCA2, BID, BTLA, Biglycan, Bub-1, Bik-like Killer Protein, c-jun, CD90/Thyl, c-Rel, CD94, CCL6/C10, CD97, CIq R1/CD93, CD151, CIqTNF1, CD160, ClqTNF4, CD163, ClqTNF5, CD164, Complement Component CIr, CD200, Complement Component CIs, CD200 R1, Complement Component C2, CD229/SLAMF3, Complement Component C3a, CD23/Fc epsilon R11, Complement Component C3d, CD2F-10/SLAMF9, Complement Component C5a, CD5L, Cadherin-4/R-Cadherin, CD69, Cadherin-6, CDC2, Cadherin-8, CDC25A, Cadherin-11, CDC25B, Cadherin-12, CDCP1, Cadherin-13, CDO, Cadherin-17, CDX4, E-Cadherin, CEACAM-1/CD66a, N-Cadherin, CEACAM-6, P-Cadherin, Cerberus 1, VE-Cadherin, CFTR, Calbindin D, cGMP, Calcineurin A, Chem R23, Calcineurin B, Chemerin, Calreticulin-2, Chemokine Sampler Packs, CaM Kinase II, Chitinase 3-like 1, cAMP, Chitotriosidase/CHIT1, Cannabinoid R1, Chk1, Cannabinoid R2/CB2/CNR2, Chk2, CAR/NR1I3, CHL-1/L1CAM-2, Carbonic Anhydrase I, Choline Acetyltransferase/CbAT, Carbonic Anhydrase II, Chondrolectin, Carbonic Anhydrase III, Chordin, Carbonic Anhydrase IV, Chordin-Like 1, Carbonic Anhydrase VA, Chordin-Like 2, Carbonic Anhydrase VB, CINC-I, Carbonic Anhydrase VI, CINC-2, Carbonic Anhydrase VII, CINC-3, Carbonic Anhydrase VIII, Claspin, Carbonic Anhydrase IX, Claudin-6, Carbonic Anhydrase X, CLC, Carbonic Anhydrase XII, CLEC-I, Carbonic Anhydrase XIII, CLEC-2, Carbonic Anhydrase XIV, CLECSF 13/CLEC4F, Carboxymethyl Lysine, CLECSF8, Carboxypeptidase A1/CPA1, CLF-I, Carboxypeptidase A2, CL-P1/COLEC12, Carboxypeptidase A4, Clusterin, Carboxypeptidase B1, Clusterin-like 1, Carboxypeptidase E/CPE, CMG-2, Carboxypeptidase X1, CMV UL146, Cardiotrophin-1, CMV UL147, Carnosine Dipeptidase 1, CNP, Caronte, CNTF, CART, CNTF R alpha, Caspase, Coagulation Factor II/Thrombin, Caspase-1, Coagulation Factor I11/Tissue Factor, Caspase-2, Coagulation Factor VII, Caspase-3, Coagulation Factor X, Caspase-4, Coagulation Factor XI, Caspase-6, Coagulation Factor XIV/Protein C, Caspase-7, COCO, Caspase-8, Cohesin, Caspase-9, Collagen I, Caspase-10, Collagen II, Caspase-12, Collagen IV, Caspase-13, Common gamma Chain/IL-2 R gamma, Caspase Peptide Inhibitors, COMP/Thrombospondin-5, Catalase, Complement Component CIrLP, beta-Catenin, Complement Component CIqA, Cathepsin 1, Complement Component CIqC, Cathepsin 3, Complement Factor D, Cathepsin 6, Complement Factor I, Cathepsin A, Complement MASP3, Cathepsin B, Connexin 43, Cathepsin C/DPPI, Contactin-1, Cathepsin D, Contactin-2/TAG1, Cathepsin E, Contactin-4, Cathepsin F, Contactin-5, Cathepsin H, Corin, Cathepsin L, Cornulin, Cathepsin O, CORS26/ClqTNF,3, Cathepsin S, Rat Cortical Stem Cells, Cathepsin V, Cortisol, Cathepsin XITJ?, COUP-TF I/NR2F1, CBP, COUP-TF II/NR2F2, CCI, COX-I, CCK-A R, COX-2, CCL28, CRACC/SLAMF7, CCR1, C-Reactive Protein, CCR2, Creatine Kinase, Muscle/CKMM, CCR3, Creatinine, CCR4, CREB, CCR5, CREG, CCR6, CRELD1, CCR7, CRELD2, CCR8, CRHBP, CCR9, CRHR-I, CCR1O, CRIM1, CD155/PVR, Cripto, CD2, CRISP-2, CD3, CRISP-3, CD4, Crossveinless-2, CD4+/45RA-, CRTAM, CD4+/45RO, CRTH-2, CD4+/CD62L-/CD44, CRY1, CD4+/CD62L+/CD44, Cryptic, CD5, CSB/ERCC6, CD6, CCL27/CTACK, CD8, CTGF/CCN2, CD8+/45RA-, CTLA-4, CD8+/45RO-, Cubilin, CD9, CX3CR1, CD14, CXADR, CD27/TNFRSF7, CXCL16, CD27 Ligand/TNFSF7, CXCR3, CD28, CXCR4, CD30/TNFRSF8, CXCR5, CD30 Ligand/TNFSF8, CXCR6, CD31/PECAM-1, Cyclophilin A, CD34, Cyr61/CCN1, CD36/SR-B3, Cystatin A, CD38, Cystatin B, CD40/TNFRSF5, Cystatin C, CD40 Ligand/TNFSF5, Cystatin D, CD43, Cystatin E/M, CD44, Cystatin F, CD45, Cystatin H, CD46, Cystatin H2, CD47, Cystatin S, CD48/SLAMF2, Cystatin SA, CD55/DAF, Cystatin SN, CD58/LFA-3, Cytochrome c, CD59, Apocytochrome c, CD68, Holocytochrome c, CD72, Cytokeratin 8, CD74, Cytokeratin 14, CD83, Cytokeratin 19, CD84/SLAMF5, Cytonin, D6, DISP1, DAN, Dkk-1, DANCE, Dkk-2, DARPP-32, Dkk-3, DAX1/NROB1, Dkk-4, DCC, DLEC, DCIR/CLEC4A, DLL1, DCAR, DLL4, DcR3/TNFRSF6B, d-Luciferin, DC-SIGN, DNA Ligase IV, DC-SIGNR/CD299, DNA Polymerase beta, DcTRAIL R1/TNFRSF23, DNAM-I, DcTRAIL R2/TNFRSF22, DNA-PKcs, DDR1, DNER, DDR2, Dopa Decarboxylase/DDC, DEC-205, DPCR-I, Decapentaplegic, DPP6, Decorin, DPP A4, Dectin-1/CLEC7A, DPPA5/ESG1, Dectin-2/CLEC6A, DPPII/QPP/DPP7, DEP-1/CD148, DPPIV/CD26, Desert Hedgehog, DR3/TNFRSF25, Desmin, DR6/TNFRSF21, Desmoglein-1, DSCAM, Desmoglein-2, DSCAM-L1, Desmoglein-3, DSPG3, Dishevelled-1, Dtk, Dishevelled-3, Dynamin, EAR2/NR2F6, EphA5, ECE-I, EphA6, ECE-2, EphA7, ECF-L/CHI3L3, EphA8, ECM-I, EphB1, Ecotin, EphB2, EDA, EphB3, EDA-A2, EphB4, EDAR, EphB6, EDG-I, Ephrin, EDG-5, Ephrin-A1, EDG-8, Ephrin-A2, eEF-2, Ephrin-A3, EGF, Ephrin-A4, EGF R, Ephrin-A5, EGR1, Ephrin-B, EG-VEGF/PK1, Ephrin-B1, eIF2 alpha, Ephrin-B2, eIF4E, Ephrin-B3, Elk-I, Epigen, EMAP-II, Epimorphin/Syntaxin 2, EMMPRIN/CD147, Epiregulin, CXCL5/ENA, EPR-1/Xa Receptor, Endocan, ErbB2, Endoglin/CD105, ErbB3, Endoglycan, ErbB4, Endonuclease III, ERCC1, Endonuclease IV, ERCC3, Endonuclease V, ERK1/ERK2, Endonuclease VIII, ERK1, Endorepellin/Perlecan, ERK2, Endostatin, ERK3, Endothelin-1, ERK5/BMK1, Engrailed-2, ERR alpha/NR3B1, EN-RAGE, ERR beta/NR3B2, Enteropeptidase/Enterokinase, ERR gamma/NR3B3, CCL1 1/Eotaxin, Erythropoietin, CCL24/Eotaxin-2, Erythropoietin R, CCL26/Eotaxin-3, ESAM, EpCAM/TROP-1, ER alpha/NR3A1, EPCR, ER beta/NR3A2, Eph, Exonuclease III, EphA1, Exostosin-like 2/EXTL2, EphA2, Exostosin-like 3/EXTL3, EphA3, FABP1, FGF-BP, FABP2, FGF R1-4, FABP3, FGF R1, FABP4, FGF R2, FABP5, FGF R3, FABP7, FGF R4, FABP9, FGF R5, Complement Factor B, Fgr, FADD, FHR5, FAM3A, Fibronectin, FAM3B, Ficolin-2, FAM3C, Ficolin-3, FAM3D, FITC, Fibroblast Activation Protein alpha/FAP, FKBP38, Fas/TNFRSF6, Flap, Fas Ligand/TNFSF6, FLIP, FATP1, FLRG, FATP4, FLRT1, FATP5, FLRT2, Fc gamma R1/CD64, FLRT3, Fc gamma RIIB/CD32b, Flt-3, Fc gamma RIIC/CD32c, Flt-3 Ligand, Fc gamma RIIA/CD32a, Follistatin, Fc gamma RIII/CD16, Follistatin-like 1, FcRH1/IRTA5, FosB/GOS3, FcRH2/IRTA4, FoxD3, FcRH4/IRTA1, FoxJ1, FcRH5/IRTA2, FoxP3, Fc Receptor-like 3/CD16-2, Fpg, FEN-I, FPR1, Fetuin A, FPRL1, Fetuin B, FPRL2, FGF acidic, CX3CL1/Fractalkine, FGF basic, Frizzled-1, FGF-3, Frizzled-2, FGF-4, Frizzled-3, FGF-5, Frizzled-4, FGF-6, Frizzled-5, FGF-8, Frizzled-6, FGF-9, Frizzled-7, FGF-IO, Frizzled-8, FGF-11, Frizzled-9, FGF-12, Frk, FGF-13, sFRP-1, FGF-16, sFRP-2, FGF-17, sFRP-3, FGF-19, sFRP-4, FGF-20, Furin, FGF-21, FXR/NR1H4, FGF-22, Fyn, FGF-23, G9a/EHMT2, GFR alpha-3/GDNF R alpha-3, GABA-A-R alpha 1, GFR alpha-4/GDNF R alpha-4, GABA-A-R alpha 2, GITR/TNFRSF18, GABA-A-R alpha 4, GITR Ligand/TNFSF18, GABA-A-R alpha 5, GLI-I, GABA-A-R alpha 6, GLI-2, GABA-A-R beta 1, GLP/EHMT1, GABA-A-R beta 2, GLP-I R, GABA-A-R beta 3, Glucagon, GABA-A-R gamma 2, Glucosamine (N-acetyl)-6-Sulfatase/GNS, GABA-B-R2, GIuR1, GAD1/GAD67, GluR2/3, GAD2/GAD65, GluR2, GADD45 alpha, GluR3, GADD45 beta, Glut1, GADD45 gamma, Glut2, Galectin-1, Glut3, Galectin-2, Glut4, Galectin-3, Glut5, Galectin-3 BP, Glutaredoxin 1, Galectin-4, Glycine R, Galectin-7, Glycophorin A, Galectin-8, Glypican 2, Galectin-9, Glypican 3, GalNAc4S-6ST, Glypican 5, GAP-43, Glypican 6, GAPDH, GM-CSF, Gas1, GM-CSF R alpha, Gas6, GMF-beta, GASP-1/WFIKKNRP, gpl30, GASP-2/WFIKKN, Glycogen Phosphorylase BB/GPBB, GATA-I, GPR15, GATA-2, GPR39, GATA-3, GPVI, GATA-4, GR/NR3C1, GATA-5, Gr-1/4Ly-6G, GATA-6, Granulysin, GBL, Granzyme A, GCNF/NR6A1, Granzyme B, CXCL6/GCP-2, Granzyme D, G-CSF, Granzyme G, G-CSF R, Granzyme H, GDF-I, GRASP, GDF-3 GRB2, GDF-5, Gremlin, GDF-6, GRO, GDF-7, CXCL1/GRO alpha, GDF-8, CXCL2/GRO beta, GDF-9, CXCL3/GRO gamma, GDF-11, Growth Hormone, GDF-15, Growth Hormone R, GDNF, GRP75/HSPA9B, GFAP, GSK-3 alpha/beta, GFI-I, GSK-3 alpha, GFR alpha-1/GDNF R alpha-1, GSK-3 beta, GFR alpha-2/GDNF R alpha-2, EZFIT, H2AX, Histidine, H60, HM74A, HAI-I, HMGA2, HAI-2, HMGB1, HAI-2A, TCF-2/HNF-1 beta, HAI-2B, HNF-3 beta/FoxA2, HAND1, HNF-4 alpha/NR2A1, HAPLN1, HNF-4 gamma/NR2A2, Airway Trypsin-like Protease/HAT, HO-1/HMOX1/HSP32, HB-EGF, HO-2/HMOX2, CCL 14a/HCC-1, HPRG, CCL14b/HCC-3, Hrk, CCL16/HCC-4, HRP-I, alpha HCG, HS6ST2, Hck, HSD-I, HCR/CRAM-A/B, HSD-2, HDGF, HSP 10/EPF, Hemoglobin, HSP27, Hepassocin, HSP60, HES-1, HSP70, HES-4, HSP90, HGF, HTRA/Protease Do, HGF Activator, HTRA1/PRSS11, HGF R, HTRA2/0 ml, HIF-I alpha, HVEM/TNFRSF14, HIF-2 alpha, Hyaluronan, HIN-1/Secretoglobulin 3A1, 4-Hydroxynonenal, Hip, CCL1/I-309/TCA-3, IL-IO, cIAP (pan), IL-IO R alpha, cIAP-1/HIAP-2, IL-10 R beta, cIAP-2/HIAP-1, IL-11, IBSP/Sialoprotein II, EL-11 R alpha, ICAM-1/CD54, IL-12, ICAM-2/CD102, IL-12/IL-23 p40, ICAM-3/CD50, IL-12 R beta 1, ICAM-5, IL-12 R beta 2, ICAT, IL-13, ICOS, IL-13 R alpha 1, Iduronate 2-Sulfatase/EOS, IL-13 R alpha 2, EFN, IL-15, IFN-alpha, IL-15 R alpha, IFN-alpha 1, IL-16, IFN-alpha 2, IL-17, IFN-alpha 4b, IL-17 R, IFN-alpha A, IL-17 RC, IFN-alpha B2, IL-17 RD, IFN-alpha C, IL-17B, IFN-alpha D, IL-17B R, IFN-alpha F, IL-17C, IFN-alpha G, IL-17D, IFN-alpha H2, IL-17E, IFN-alpha I, IL-17F, IFN-alpha J1, IL-18/IL-1F4, IFN-alpha K, IL-18 BPa, IFN-alpha WA, IL-18 BPc, IFN-alpha/beta R1, IL-18 BPd, IFN-alpha/beta R2, IL-18 R alpha/IL-1 R5, IFN-beta, IL-18 R beta/IL-1 R7, IFN-gamma, IL-19, IFN-gamma R1, IL-20, IFN-gamma R2, IL-20 R alpha, IFN-omega, IL-20 R beta, IgE, IL-21, IGFBP-I, IL-21 R, IGFBP-2, IL-22, IGFBP-3, IL-22 R, IGFBP-4, IL-22BP, IGFBP-5, IL-23, IGFBP-6, IL-23 R, IGFBP-L1, IL-24, IGFBP-rp1/IGFBP-7, IL-26/AK155, IGFBP-rPIO, IL-27, IGF-I, EL-28A, IGF-I R, IL-28B, IGF-II, IL-29/EFN-lambda 1, IGF-II R, IL-31, IgG, EL-31 RA, IgM, IL-32 alpha, IGSF2, IL-33, IGSF4A/SynCAM, ILT2/CD85J, IGSF4B, ILT3/CD85k, IGSF8, ILT4/CD85d, IgY, ILT5/CD85a, IkB-beta, ILT6/CD85e, IKK alpha, Indian Hedgehog, IKK epsilon, INSRR, EKK gamma, Insulin, IL-1 alpha/IL-IF1, Insulin R/CD220, IL-1 beta/IL-1F2, Proinsulin, IL-1ra/IL-1F3, Insulysin/EDE, IL-1F5/FIL1 delta, Integrin alpha 2/CD49b, IL-1F6/FIL1 epsilon, Integrin alpha 3/CD49c, IL-1F7/FIL1 zeta, Integrin alpha 3 beta 1/VLA-3, IL-1F8/FIL1 eta, Integrin alpha 4/CD49d, IL-1F9/IL-1 H1, Integrin alpha 5/CD49e, IL-1F10/IL-1HY2, Integrin alpha 5 beta 1, IL-I RI, Integrin alpha 6/CD49f, IL-I RII, Integrin alpha 7, IL-I R3/IL-1 R AcP, Integrin alpha 9, IL-I R4/ST2, Integrin alpha E/CD103, IL-I R6/IL-1 R rp2, Integrin alpha L/CD1 Ia, IL-I R8, Integrin alpha L beta 2, IL-I R9, Integrin alpha M/CD1 Ib, IL-2, Integrin alpha M beta 2, IL-2 R alpha, Integrin alpha V/CD51, IL-2 R beta, Integrin alpha V beta 5, IL-3, Integrin alpha V beta 3, IL-3 R alpha, Integrin alpha V beta 6, IL-3 R beta, Integrin alpha XJCD1 Ic, IL-4, Integrin beta 1/CD29, IL-4 R, Integrin beta 2/CD18, IL-5, Integrin beta 3/CD61, IL-5 R alpha, Integrin beta 5, IL-6, Integrin beta 6, IL-6 R, Integrin beta 7, IL-7, CXCL10/EP-10/CRG-2, IL-7 R alpha/CD127, IRAKI, CXCR1/IL-8 RA, IRAK4, CXCR2/IL-8 RB, ERS-I, CXCL8/IL-8, Islet-1, IL-9, CXCL1 1/I-TAC, IL-9 R, Jagged 1, JAM-4/IGSF5, Jagged 2, JNK, JAM-A, JNK1/JNK2, JAM-B/VE-JAM, JNK1, JAM-C, JNK2, Kininogen, Kallikrein 3/PSA, Kininostatin, Kallikrein 4, KER/CD158, Kallikrein 5, KER2D1, Kallikrein 6/Neurosin, KIR2DL3, Kallikrein 7, KIR2DL4/CD158d, Kallikrein 8/Neuropsin, KIR2DS4, Kallikrein 9, KIR3DL1, Plasma Kallikrein/KLKB1, KER3DL2, Kallikrein 10, Kirrel2, Kallikrein 11, KLF4, Kallikrein 12, KLF5, Kallikrein 13, KLF6, Kallikrein 14, Klotho, Kallikrein 15, Klotho beta, KC, KOR, Keap1, Kremen-1, KeI1, Kremen-2, KGF/FGF-7, LAG-3, LINGO-2, LAIR1, Lipin 2, LAIR2, Lipocalin-1, Laminin alpha 4, Lipocalin-2/NGAL, Laminin gamma 1,5-Lipoxygenase, Laminin I, LXR alpha/NR1H3, Laminin S, LXR beta/NR1H2, Laminin-1, Livin, Laminin-5, LEX, LAMP, LMIR1/CD300A, Langerin, LMIR2/CD300c, LAR, LMIR3/CD300LF, Latexin, LMIR5/CD300LB, Layilin, LMIR6/CD300LE, LBP, LMO2, LDL R, LOX-1/SR-E1, LECT2, LRH-1/NR5A2, LEDGF, LRIG1, Lefty, LRIG3, Lefty-1, LRP-I, Lefty-A, LRP-6, Legumain, LSECtin/CLEC4G, Leptin, Lumican, Leptin R, CXCL15/Lungkine, Leukotriene B4, XCL1/Lymphotactin, Leukotriene B4 R1, Lymphotoxin, LEF, Lymphotoxin beta/TNFSF3, LIF R alpha, Lymphotoxin beta R/TNFRSF3, LIGHT/TNFSF14, Lyn, Limitin, Lyp, LIMPII/SR-B2, Lysyl Oxidase Homolog 2, LIN-28, LYVE-I, LINGO-I, alpha 2-Macroglobulin, CXCL9/MIG, MAD2L1, Mimecan, MAdCAM-1, Mindin, MafB, Mineralocorticoid R/NR3C2, MafF, CCL3L1/MIP-1 alpha Isoform LD78 beta, MafG, CCL3/MIP-1 alpha, MafK, CCL4L1/LAG-1, MAG/Siglec-4-a, CCL4/MIP-1 beta, MANF, CCL15/MEP-1 delta, MAP2, CCL9/10/MIP-1 gamma, MAPK, MIP-2, Marapsin/Pancreasin, CCL19/MIP-3 beta, MARCKS, CCL20/MIP-3 alpha, MARCO, MIP-I, Mash1, MIP-II, Matrilin-2, MIP-III, Matrilin-3, MIS/AMH, Matrilin-4, MIS RII, Matriptase/ST14, MIXL1, MBL, MKK3/MKK6, MBL-2, MKK3, Melanocortin 3R/MC3R, MKK4, MCAM/CD146, MKK6, MCK-2, MKK7, McI-I, MKP-3, MCP-6, MLH-I, CCL2/MCP-1, MLK4 alpha, MCP-11, MMP, CCL8/MCP-2, MMP-1, CCL7/MCP-3/MARC, MMP-2, CCL13/MCP-4, MMP-3, CCL12/MCP-5, MMP-7, M-CSF, MMP-8, M-CSF R, MMP-9, MCV-type II, MMP-IO, MD-I, MMP-I 1, MD-2, MMP-12, CCL22/MDC, MMP-13, MDL-1/CLEC5A, MMP-14, MDM2, MMP-15, MEA-I, MMP-16/MT3-MMP, MEK1/MEK2, MMP-24/MT5-MMP, MEK1, MMP-25/MT6-MMP, MEK2, MMP-26, Melusin, MMR, MEPE, MOG, Meprin alpha, CCL23/MPIF-1, Meprin beta, M-Ras/R-Ras3, Mer, Mrel 1, Mesothelin, MRP1 Meteorin, MSK1/MSK2, Methionine Aminopeptidase 1, MSK1, Methionine Aminopeptidase, MSK2, Methionine Aminopeptidase 2, MSP, MFG-E8, MSP R/Ron, MFRP, Mug, MgcRacGAP, MULT-I, MGL2, Musashi-1, MGMT, Musashi-2, MIA, MuSK, MICA, MutY DNA Glycosylase, MICB, MyD88, MICL/CLEC12A, Myeloperoxidase, beta 2 Microglobulin, Myocardin, Midkine, Myocilin, MIF, Myoglobin, NAIP NGFI-B gamma/NR4A3, Nanog, NgR2/NgRH1, CXCL7/NAP-2, NgR3/NgRH2, Nbsl, Nidogen-1/Entactin, NCAM-1/CD56, Nidogen-2, NCAM-L1, Nitric Oxide, Nectin-1, Nitrotyrosine, Nectin-2/CD1 12, NKG2A, Nectin-3, NKG2C, Nectin-4, NKG2D, Neogenin, NKp30, Neprilysin/CDIO, NKp44, Neprilysin-2/MMEL1/MMEL2, NKp46/NCR1, Nestin, NKp80/KLRF1, NETO2, NKX2.5, Netrin-1, NMDA R, NR1 Subunit, Netrin-2, NMDA R, NR2A Subunit, Netrin-4, NMDA R, NR2B Subunit, Netrin-Gla, NMDA R, NR2C Subunit, Netrin-G2a, N-Me-6,7-diOH-TIQ, Neuregulin-1/NRG1, Nodal, Neuregulin-3/NRG3, Noggin, Neuritin, Nogo Receptor, NeuroD1, Nogo-A, Neurofascin, NOMO, Neurogenin-1, Nope, Neurogenin-2, Norrin, Neurogenin-3, eNOS, Neurolysin, iNOS, Neurophysin II, nNOS, Neuropilin-1, Notch-1, Neuropilin-2, Notch-2, Neuropoietin, Notch-3, Neurotrimin, Notch-4, Neurturin, NOV/CCN3, NFAM1, NRAGE, NF-H, NrCAM, NFkB1, NRL, NFkB2, NT-3, NF-L, NT-4, NF-M, NTB-A/SLAMF6, NG2/MCSP, NTH1, NGF R/TNFRSF16, Nucleostemin, beta-NGF, Nurr-⅟NR4A2, NGFI-B alpha/NR4A1, OAS2, Orexin B, OBCAM, OSCAR, OCAM, OSF-2/Periostin, OCIL/CLEC2d, Oncostatin M/OSM, OCILRP2/CLEC21, OSM R beta, Oct-¾, Osteoactivin/GPNMB, OGG1, Osteoadherin, Olig 1, 2, 3, Osteocalcin, Olig1, Osteocrin, Olig2, Osteopontin, Olig3, Osteoprotegerin/TNFRSF1 IB, Oligodendrocyte Marker 01, Otx2, Oligodendrocyte Marker 04, OV-6, OMgp, OX40/TNFRSF4, Opticin, OX40 Ligand/TNFSF4, Orexin A, OAS2, Orexin B, OBCAM, OSCAR, OCAM, OSF-2/Periostin, OCIL/CLEC2d, Oncostatin M/OSM, OCILRP2/CLEC2i, OSM R beta, Oct-¾, Osteoactivin/GPNMB, OGG1, Osteoadherin, Olig 1, 2, 3, Osteocalcin, Olig1, Osteocrin, Olig2, Osteopontin, Olig3, Osteoprotegerin/TNFRSF1 IB, Oligodendrocyte Marker 01, Otx2, Oligodendrocyte Marker 04, OV-6, OMgp, OX40/TNFRSF4, Opticin, OX40 Ligand/TNFSF4, Orexin A, RACK1, Ret, Rad1, REV-ERB alpha/NR1D1, Rad17, REV-ERB beta/NR1D2, Rad51, Rex-1, Rae-1, RGM-A, Rae-1 alpha, RGM-B, Rae-1 beta, RGM-C, Rae-1 delta, Rheb, Rae-1 epsilon, Ribosomal Protein S6, Rae-1 gamma, RIP1, Raf-1, ROBO1, RAGE, ROBO2, Ra1A/Ra1B, R0B03, RaIA, ROBO4, RaIB, ROR/NR1F1-3 (pan), RANK/TNFRSF1 1A, ROR alpha/NR1F1, CCL5/RANTES, ROR gamma/NR1F3, Rap1A/B, RTK-like Orphan Receptor 1/ROR1, RAR alpha/NR1B1, RTK-like Orphan Receptor 2/ROR2, RAR beta/NR1B2, RP105, RAR gamma/NR1B3, RP A2, Ras, RSK (pan), RBP4, RSK1/RSK2, RECK, RSK1, Reg 2/PAP, RSK2, Reg I, RSK3, Reg II, RSK4, Reg III, R-Spondin 1, Reg I1ia, R-Spondin 2, Reg IV, R-Spondin 3, Relaxin-1, RUNX1/CBFA2, Relaxin-2, RUNX2/CBFA1, Relaxin-3, RUNX3/CBFA3, RELM alpha, RXR alpha/NR2B1, RELM beta, RXR beta/NR2B2, RELT/TNFRSF19L, RXR gamma/NR2B3, Resistin, S1OOA1O, SLITRK5, S100A8, SLPI, S100A9, SMAC/Diablo, S1OOB, Smad1, S1OOP, Smad2, SALL1, Smad3, delta-Sarcoglycan, Smad4, Sca-1/Ly6, Smad5, SCD-I, Smad7, SCF, Smad8, SCF R/c-kit, SMC1, SCGF, alpha-Smooth Muscle Actin, SCL/Tall, SMUG1, SCP3/SYCP3, Snail, CXCL12/SDF-1, Sodium Calcium Exchanger 1, SDNSF/MCFD2, Soggy-1, alpha-Secretase, Sonic Hedgehog, gamma-Secretase, S or CS1, beta-Secretase, S or CS3, E-Selectin, Sortilin, L-Selectin, SOST, P-Selectin, SOX1, Semaphorin 3A, SOX2, Semaphorin 3C, SOX3, Semaphorin 3E, SOX7, Semaphorin 3F, SOX9, Semaphorin 6A, SOX10, Semaphorin 6B, SOX 17, Semaphorin 6C, SOX21 Semaphorin 6D, SPARC, Semaphorin 7 A, SPARC-like 1, Separase, SP-D, Serine/Threonine Phosphatase Substrate I, Spinesin, Serpin A1, F-Spondin, Serpin A3, SR-AI/MSR, Serpin A4/Kallistatin, Src, Serpin A5/Protein C Inhibitor, SREC-I/SR-F1, Serpin A8/Angiotensinogen, SREC-II, Serpin B5, SSEA-I, Serpin C1/Antithrombin-III, SSEA-3, Serpin D1/Heparin Cofactor II, SSEA-4, Serpin E1/PAI-1, ST7/LRP12, Serpin E2, Stabilin-1, Serpin F1, Stabilin-2, Serpin F2, Stanniocalcin 1, Serpin G1/C1 Inhibitor, Stanniocalcin 2, Serpin 12, STAT1, Serum Amyloid A1, STAT2, SF-1/NR5A1, STAT3, SGK, STAT4, SHBG, STAT5a/b, SHIP, STAT5a, SHP/NROB2, STAT5b, SHP-I, STATE, SHP-2, VE-Statin, SIGIRR, Stella/Dppa3, Siglec-2/CD22, STRO-I, Siglec-3/CD33, Substance P, Siglec-5, Sulfamidase/SGSH, Siglec-6, Sulfatase Modifying Factor 1/SUMF1, Siglec-7, Sulfatase Modifying Factor 2/SUMF2, Siglec-9, SUM01, Siglec-10, SUM02/¾, Siglec-11, SUM03, Siglec-F, Superoxide Dismutase, SIGNR1/CD209, Superoxide Dismutase-1/Cu[0099]--Zn SOD, SIGNR4, Superoxide Dismutase-2/Mn-SOD, SIRP beta 1, Superoxide Dismutase-3/EC-SOD, SKI, Survivin, SLAM/CD150, Synapsin I, Sleeping Beauty Transposase, Syndecan-I/CD 138, Slit3, Syndecan-2, SLITRK1, Syndecan-3, SLITRK2, Syndecan-4, SLITRK4, TACI/TNFRSF13B, TMEFF 1/Tomoregulin-1, TAO2, TMEFF2, TAPP1, TNF-alpha/TNFSF IA, CCL17/TARC, TNF-beta/TNFSF1B, Tau, TNF R1/TNFRSFIA, TC21/R-Ras2, TNF RII/TNFRSF1B, TCAM-I, TOR, TCCR/WSX-1, TP-I, TC-PTP, TP63/TP73L, TDG, TR, CCL25/TECK, TR alpha/NR1A1, Tenascin C, TR beta 1/NR1A2, Tenascin R, TR2/NR2C1, TER-119, TR4/NR2C2, TERT, TRA-1-85, Testican 1/SPOCK1, TRADD, Testican 2/SPOCK2,TRAF-1, Testican 3/SPOCK3, TRAF-2, TFPI, TRAF-3, TFPI-2, TRAF-4, TGF-alpha, TRAF-6, TGF-beta, TRAIL/TNFSF10, TGF-beta 1, TRAIL R1/TNFRSFIOA, LAP (TGF-beta 1), TRAIL R2/TNFRSF10B, Latent TGF-beta 1, TRAIL R3/TNFRSF10C, TGF-beta 1.2, TRAIL R4/TNFRSF10D, TGF-beta 2, TRANCE/TNFSF1 1, TGF-beta 3, TfR (Transferrin R), TGF-beta 5, Apo-Transferrin, Latent TGF-beta by 1, Holo-Transferrin, Latent TGF-beta bp2, Trappin-2/Elafin, Latent TGF-beta bp4, TREM-1, TGF-beta R1/ALK-5, TREM-2, TGF-beta R11, TREM-3, TGF-beta RIIb, TREML1/TLT-1, TGF-beta RIII, TRF-I, Thermolysin, TRF-2, Thioredoxin-1, TRH-degrading Ectoenzyme/TRHDE, Thioredoxin-2, TRIMS, Thioredoxin-80, Tripeptidyl-Peptidase I, Thioredoxin-like 5/TRP14, TrkA, THOP1, TrkB, Thrombomodulin/CD141, TrkC, Thrombopoietin, TROP-2, Thrombopoietin R, Troponin I Peptide 3, Thrombospondin-1, Troponin T, Thrombospondin-2, TROY/TNFRSF 19, Thrombospondin-4, Trypsin 1, Thymopoietin, Trypsin 2/PRSS2, Thymus Chemokine-1, Trypsin 3/PRSS3, Tie-1, Tryptase-5/Prss32, Tie-2, Tryptase alpha/TPS1, TIM-I/KIM-I/HAVCR, Tryptase beta-1/MCPT-7, TIM-2, Tryptase beta-2/TPSB2, TIM-3, Tryptase epsilon/BSSP-4, TIM-4, Tryptase gamma-1/TPSG1, TIM-5, Tryptophan Hydroxylase, TIM-6, TSC22, TIMP-I, TSG, TIMP-2, TSG-6, TIMP-3, TSK, TIMP-4, TSLP, TL1A/TNFSF15, TSLP R, TLR1, TSP50, TLR2, beta-III Tubulin, TLR3, TWEAK/TNFSF12, TLR4, TWEAK R/TNFRSF 12, TLR5, Tyk2, TLR6, Phospho-Tyrosine, TLR9, Tyrosine Hydroxylase, TLX/NR2E1, Tyrosine Phosphatase Substrate I, Ubiquitin, UNC5H3, Ugi, UNC5H4, UGRP1, UNG, ULBP-I, uPA, ULBP-2, uPAR, ULBP-3, URB, UNC5H1, UVDE, UNC5H2, Vanilloid R1, VEGF R, VASA, VEGF R1/Flt-1, Vasohibin, VEGF R2/KDR/Flk-1, Vasorin, VEGF R3/FU-4, Vasostatin, Versican, Vav-1, VG5Q, VCAM-1, VHR, VDR/NR1I1, Vimentin, VEGF, Vitronectin, VEGF-B, VLDLR, VEGF-C, vWF-A2, VEGF-D, Synuclein-alpha, Ku70, WASP, Wnt-7b, WIF-I, Wnt-8a WISP-1/CCN4, Wnt-8b, WNK1, Wnt-9a, Wnt-1, Wnt-9b, Wnt-3a, Wnt-10a, Wnt-4, Wnt-10b, Wnt-5a, Wnt-11, Wnt-5b, wnvNS3, Wnt7a, XCR1, XPE/DDB1, XEDAR, XPE/DDB2, Xg, XPF, XIAP, XPG, XPA, XPV, XPD, XRCC1, Yes, YY1, EphA4. 
     Numerous human ion channels are targets of particular interest. Non-limiting examples include 5-hydroxytryptamine 3 receptor B subunit, 5-hydroxytryptamine 3 receptor precursor, 5-hydroxytryptamine receptor 3 subunit C, AAD 14 protein, Acetylcholine receptor protein, alpha subunit precursor, Acetylcholine receptor protein, beta subunit precursor, Acetylcholine receptor protein, delta subunit precursor, Acetylcholine receptor protein, epsilon subunit precursor, Acetylcholine receptor protein, gamma subunit precursor, Acid sensing ion channel 3 splice variant b, Acid sensing ion channel 3 splice variant c, Acid sensing ion channel 4, ADP-ribose pyrophosphatase, mitochondrial precursor, Alpha1 A-voltage-dependent calcium channel, Amiloride-sensitive cation channel 1, neuronal, Amiloride-sensitive cation channel 2, neuronal Amiloride-sensitive cation channel 4, isoform 2, Amiloride-sensitive sodium channel, Amiloride-sensitive sodium channel alpha-subunit, Amiloride-sensitive sodium channel beta-subunit, Amiloride-sensitive sodium channel delta-subunit, Amiloride-sensitive sodium channel gamma-subunit, Annexin A7, Apical-like protein, ATP-sensitive inward rectifier potassium channel 1, ATP-sensitive inward rectifier potassium channel 10, ATP-sensitive inward rectifier potassium channel 11, ATP-sensitive inward rectifier potassium channel 14, ATP-sensitive inward rectifier potassium channel 15, ATP-sensitive inward rectifier potassium channel 8, Calcium channel alpha12.2 subunit, Calcium channel alpha12.2 subunit, Calcium channel alphalE subunit, delta19 delta40 delta46 splice variant, Calcium-activated potassium channel alpha subunit 1, Calcium-activated potassium channel beta subunit 1, Calcium-activated potassium channel beta subunit 2, Calcium-activated potassium channel beta subunit 3, Calcium-dependent chloride channel-1, Cation channel TRPM4B, CDNA FLJ90453 fis, clone NT2RP3001542, highly similar to Potassium channel tetramerisation domain containing 6, CDNA FLJ90663 fis, clone PLACE 1005031, highly similar to Chloride intracellular channel protein 5, CGMP-gated cation channel beta subunit, Chloride channel protein, Chloride channel protein 2, Chloride channel protein 3, Chloride channel protein 4, Chloride channel protein 5, Chloride channel protein 6, Chloride channel protein C1C-Ka, Chloride channel protein C1C-Kb, Chloride channel protein, skeletal muscle, Chloride intracellular channel 6, Chloride intracellular channel protein 3, Chloride intracellular channel protein 4, Chloride intracellular channel protein 5, CHRNA3 protein, Clcn3e protein, CLCNKB protein, CNGA4 protein, Cullin-5, Cyclic GMP gated potassium channel, Cyclic-nucleotide-gated cation channel 4, Cyclic-nucleotide-gated cation channel alpha 3, Cyclic-nucleotide-gated cation channel beta 3, Cyclic-nucleotide-gated olfactory channel, Cystic fibrosis transmembrane conductance regulator, Cytochrome B-245 heavy chain, Dihydropyridine-sensitive L-type, calcium channel alpha-2/delta subunits precursor, FXYD domain-containing ion transport regulator 3 precursor, FXYD domain-containing ion transport regulator 5 precursor, FXYD domain-containing ion transport regulator 6 precursor, FXYD domain-containing ion transport regulator 7, FXYD domain-containing ion transport regulator 8 precursor, G protein-activated inward rectifier potassium channel 1, G protein-activated inward rectifier potassium channel 2, G protein-activated inward rectifier potassium channel 3, G protein-activated inward rectifier potassium channel 4, Gamma-aminobutyric-acid receptor alpha-1 subunit precursor, Gamma-aminobutyric-acid receptor alpha-2 subunit precursor, Gamma-aminobutyric-acid receptor alpha-3 subunit precursor, Gamma-aminobutyric-acid receptor alpha-4 subunit precursor, Gamma-aminobutyric-acid receptor alpha-5 subunit precursor, Gamma-aminobutyric-acid receptor alpha-6 subunit precursor, Gamma-aminobutyric-acid receptor beta-1 subunit precursor, Gamma-aminobutyric-acid receptor beta-2 subunit precursor, Gamma-aminobutyric-acid receptor beta-3 subunit precursor, Gamma-aminobutyric-acid receptor delta subunit precursor, Gamma-aminobutyric-acid receptor epsilon subunit precursor, Gamma-aminobutyric-acid receptor gamma-1 subunit precursor, Gamma-aminobutyric-acid receptor gamma-3 subunit precursor, Gamma-aminobutyric-acid receptor pi subunit precursor, Gamma-aminobutyric-acid receptor rho-1 subunit precursor, Gamma-aminobutyric-acid receptor rho-2 subunit precursor, Gamma-aminobutyric-acid receptor theta subunit precursor, GluR6 kainate receptor, Glutamate receptor 1 precursor, Glutamate receptor 2 precursor, Glutamate receptor 3 precursor, Glutamate receptor 4 precursor, Glutamate receptor 7, Glutamate receptor B, Glutamate receptor delta-1 subunit precursor, Glutamate receptor, ionotropic kainate 1 precursor, Glutamate receptor, ionotropic kainate 2 precursor, Glutamate receptor, ionotropic kainate 3 precursor, Glutamate receptor, ionotropic kainate 4 precursor, Glutamate receptor, ionotropic kainate 5 precursor, Glutamate [NMDA] receptor subunit 3A precursor, Glutamate [NMDA] receptor subunit 3B precursor, Glutamate [NMDA] receptor subunit epsilon 1 precursor, Glutamate [NMDA] receptor subunit epsilon 2 precursor, Glutamate [NMDA] receptor subunit epsilon 4 precursor, Glutamate [NMDA] receptor subunit zeta 1 precursor, Glycine receptor alpha-1 chain precursor, Glycine receptor alpha-2 chain precursor, Glycine receptor alpha-3 chain precursor, Glycine receptor beta chain precursor, H/ACA ribonucleoprotein complex subunit 1, High affinity immunoglobulin epsilon receptor beta-subunit, Hypothetical protein DKFZp31310334, Hypothetical protein DKFZp761M1724, Hypothetical protein FLJ12242, Hypothetical protein FLJ14389, Hypothetical protein FLJ14798, Hypothetical protein FLJ14995, Hypothetical protein FLJ16180, Hypothetical protein FLJ16802, Hypothetical protein FLJ32069, Hypothetical protein FLJ37401, Hypothetical protein FLJ38750, Hypothetical protein FLJ40162, Hypothetical protein FLJ41415, Hypothetical protein FLJ90576, Hypothetical protein FLJ90590, Hypothetical protein FLJ90622, Hypothetical protein KCTD15, Hypothetical protein MGC15619, Inositol 1,4,5-trisphosphate receptor type 1, Inositol 1,4,5-trisphosphate receptor type 2, Inositol 1,4,5-trisphosphate receptor type 3, Intermediate conductance calcium-activated potassium channel protein 4, Inward rectifier potassium channel 13, Inward rectifier potassium channel 16, Inward rectifier potassium channel 4, Inward rectifying K(+) channel negative regulator Kir2.2v, Kainate receptor subunit KA2a, KCNH5 protein, KCTD 17 protein, KCTD2 protein, Keratinocytes associated transmembrane protein 1, Kv channel-interacting protein 4, Melastatin 1, Membrane protein MLC1, MGC 15619 protein, Mucolipin-1, Mucolipin-2, Mucolipin-3, Multidrug resistance-associated protein 4, N-methyl-D-aspartate receptor 2C subunit precursor, NADPH oxidase homolog 1, Nav1.5, Neuronal acetylcholine receptor protein, alpha-10 subunit precursor, Neuronal acetylcholine receptor protein, alpha-2 subunit precursor, Neuronal acetylcholine receptor protein, alpha-3 subunit precursor, Neuronal acetylcholine receptor protein, alpha-4 subunit precursor, Neuronal acetylcholine receptor protein, alpha-5 subunit precursor, Neuronal acetylcholine receptor protein, alpha-6 subunit precursor, Neuronal acetylcholine receptor protein, alpha-7 subunit precursor, Neuronal acetylcholine receptor protein, alpha-9 subunit precursor, Neuronal acetylcholine receptor protein, beta-2 subunit precursor, Neuronal acetylcholine receptor protein, beta-3 subunit precursor, Neuronal acetylcholine receptor protein, beta-4 subunit precursor, Neuronal voltage-dependent calcium channel alpha 2D subunit, P2X purinoceptor 1, P2X purinoceptor 2, P2X purinoceptor 3, P2X purinoceptor 4, P2X purinoceptor 5, P2X purinoceptor 6, P2X purinoceptor 7, Pancreatic potassium channel TALK-Ib, Pancreatic potassium channel TALK-Ic, Pancreatic potassium channel TALK-Id, Phospholemman precursor, Plasmolipin, Polycystic kidney disease 2 related protein, Polycystic kidney disease 2-like 1 protein, Polycystic kidney disease 2-like 2 protein, Polycystic kidney disease and receptor for egg jelly related protein precursor, Polycystin-2, Potassium channel regulator, Potassium channel subfamily K member 1, Potassium channel subfamily K member 10, Potassium channel subfamily K member 12, Potassium channel subfamily K member 13, Potassium channel subfamily K member 15, Potassium channel subfamily K member 16, Potassium channel subfamily K member 17, Potassium channel subfamily K member 2, Potassium channel subfamily K member 3, Potassium channel subfamily K member 4, Potassium channel subfamily K member 5, Potassium channel subfamily K member 6, Potassium channel subfamily K member 7, Potassium channel subfamily K member 9, Potassium channel tetramerisation domain containing 3, Potassium channel tetramerisation domain containing protein 12, Potassium channel tetramerisation domain containing protein 14, Potassium channel tetramerisation domain containing protein 2, Potassium channel tetramerisation domain containing protein 4, Potassium channel tetramerisation domain containing protein 5, Potassium channel tetramerization domain containing 10, Potassium channel tetramerization domain containing protein 13, Potassium channel tetramerization domain-containing 1, Potassium voltage-gated channel subfamily A member 1, Potassium voltage-gated channel subfamily A member 2, Potassium voltage-gated channel subfamily A member 4, Potassium voltage-gated channel subfamily A member 5, Potassium voltage-gated channel subfamily A member 6, Potassium voltage-gated channel subfamily B member 1, Potassium voltage-gated channel subfamily B member 2, Potassium voltage-gated channel subfamily C member 1, Potassium voltage-gated channel subfamily C member 3, Potassium voltage-gated channel subfamily C member 4, Potassium voltage-gated channel subfamily D member 1, Potassium voltage-gated channel subfamily D member 2, Potassium voltage-gated channel subfamily D member 3, Potassium voltage-gated channel subfamily E member 1, Potassium voltage-gated channel subfamily E member 2, Potassium voltage-gated channel subfamily E member 3, Potassium voltage-gated channel subfamily E member 4, Potassium voltage-gated channel subfamily F member 1, Potassium voltage-gated channel subfamily G member 1, Potassium voltage-gated channel subfamily G member 2, Potassium voltage-gated channel subfamily G member 3, Potassium voltage-gated channel subfamily G member 4, Potassium voltage-gated channel subfamily H member 1, Potassium voltage-gated channel subfamily H member 2, Potassium voltage-gated channel subfamily H member 3, Potassium voltage-gated channel subfamily H member 4, Potassium voltage-gated channel subfamily H member 5, Potassium voltage-gated channel subfamily H member 6, Potassium voltage-gated channel subfamily H member 7, Potassium voltage-gated channel subfamily H member 8, Potassium voltage-gated channel subfamily KQT member 1, Potassium voltage-gated channel subfamily KQT member 2, Potassium voltage-gated channel subfamily KQT member 3, Potassium voltage-gated channel subfamily KQT member 4, Potassium voltage-gated channel subfamily KQT member 5, Potassium voltage-gated channel subfamily S member 1, Potassium voltage-gated channel subfamily S member 2, Potassium voltage-gated channel subfamily S member 3, Potassium voltage-gated channel subfamily V member 2, Potassium voltage-gated channel, subfamily H, member 7, isoform 2, Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 1, Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 2, Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 3, Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 4, Probable mitochondrial import receptor subunit TOM40 homolog, Purinergic receptor P2X5, isoform A, Putative 4 repeat voltage-gated ion channel, Putative chloride channel protein 7, Putative GluR6 kainate receptor, Putative ion channel protein CATSPER2 variant 1, Putative ion channel protein CATSPER2 variant 2, Putative ion channel protein CATSPER2 variant 3, Putative regulator of potassium channels protein variant 1, Putative tyrosine-protein phosphatase TPTE, Ryanodine receptor 1, Ryanodine receptor 2, Ryanodine receptor 3, SH3 KBP1 binding protein 1, Short transient receptor potential channel 1, Short transient receptor potential channel 4, Short transient receptor potential channel 5, Short transient receptor potential channel 6, Short transient receptor potential channel 7, Small conductance calcium-activated potassium channel protein 1, Small conductance calcium-activated potassium channel protein 2, isoform b, Small conductance calcium-activated potassium channel protein 3, isoform b, Small-conductance calcium-activated potassium channel SK2, Small-conductance calcium-activated potassium channel SK3, Sodium channel, Sodium channel beta-1 subunit precursor, Sodium channel protein type II alpha subunit, Sodium channel protein type III alpha subunit, Sodium channel protein type IV alpha subunit, Sodium channel protein type IX alpha subunit, Sodium channel protein type V alpha subunit, Sodium channel protein type VII alpha subunit, Sodium channel protein type VIII alpha subunit, Sodium channel protein type X alpha subunit, Sodium channel protein type XI alpha subunit, Sodium- and chloride-activated ATP-sensitive potassium channel, Sodium/potassium-transporting ATPase gamma chain, Sperm-associated cation channel 1, Sperm-associated cation channel 2, isoform 4, Syntaxin-1B1, Transient receptor potential cation channel subfamily A member 1, Transient receptor potential cation channel subfamily M member 2, Transient receptor potential cation channel subfamily M member 3, Transient receptor potential cation channel subfamily M member 6, Transient receptor potential cation channel subfamily M member 7, Transient receptor potential cation channel subfamily V member 1, Transient receptor potential cation channel subfamily V member 2, Transient receptor potential cation channel subfamily V member 3, Transient receptor potential cation channel subfamily V member 4, Transient receptor potential cation channel subfamily V member 5, Transient receptor potential cation channel subfamily V member 6, Transient receptor potential channel 4 epsilon splice variant, Transient receptor potential channel 4 zeta splice variant, Transient receptor potential channel 7 gamma splice variant, Tumor necrosis factor, alpha-induced protein 1, endothelial, Two-pore calcium channel protein 2, VDAC4 protein, Voltage gated potassium channel Kv3.2b, Voltage gated sodium channel beta1B subunit, Voltage-dependent anion channel, Voltage-dependent anion channel 2, Voltage-dependent anion-selective channel protein 1, Voltage-dependent anion-selective channel protein 2, Voltage-dependent anion-selective channel protein 3, Voltage-dependent calcium channel gamma-1 subunit, Voltage-dependent calcium channel gamma-2 subunit, Voltage-dependent calcium channel gamma-3 subunit, Voltage-dependent calcium channel gamma-4 subunit, Voltage-dependent calcium channel gamma-5 subunit, Voltage-dependent calcium channel gamma-6 subunit, Voltage-dependent calcium channel gamma-7 subunit, Voltage-dependent calcium channel gamma-8 subunit, Voltage-dependent L-type calcium channel alpha-1C subunit, Voltage-dependent L-type calcium channel alpha-1D subunit, Voltage-dependent L-type calcium channel alpha-IS subunit, Voltage-dependent L-type calcium channel beta-1 subunit, Voltage-dependent L-type calcium channel beta-2 subunit, Voltage-dependent L-type calcium channel beta-3 subunit, Voltage-dependent L-type calcium channel beta-4 subunit, Voltage-dependent N-type calcium channel alpha-1B subunit, Voltage-dependent P/Q-type calcium channel alpha-1A subunit, Voltage-dependent R-type calcium channel alpha-1E subunit, Voltage-dependent T-type calcium channel alpha-1G subunit, Voltage-dependent T-type calcium channel alpha-1H subunit, Voltage-dependent T-type calcium channel alpha-1I subunit, Voltage-gated L-type calcium channel alpha-1 subunit, Voltage-gated potassium channel beta-1 subunit, Voltage-gated potassium channel beta-2 subunit, Voltage-gated potassium channel beta-3 subunit, Voltage-gated potassium channel KCNA7. The Nav1.x family of human voltage-gated sodium channels is also a particularly promising target. This family includes, for example, channels Nav1.6 and Nav1.8. 
     In certain embodiments, the therapeutic protein may be a G-Protein Coupled Receptor (GPCR). Exemplary GPCRs include, but are not limited to, Class A Rhodopsin like receptors such as Muscatinic (Muse.) acetylcholine Vertebrate type 1, Muse, acetylcholine Vertebrate type 2, Muse, acetylcholine Vertebrate type 3, Muse, acetylcholine Vertebrate type 4; Adrenoceptors (Alpha Adrenoceptors type 1, Alpha Adrenoceptors type 2, Beta Adrenoceptors type 1, Beta Adrenoceptors type 2, Beta Adrenoceptors type 3, Dopamine Vertebrate type 1, Dopamine Vertebrate type 2, Dopamine Vertebrate type 3, Dopamine Vertebrate type 4, Histamine type 1, Histamine type 2, Histamine type 3, Histamine type 4, Serotonin type 1, Serotonin type 2, Serotonin type 3, Serotonin type 4, Serotonin type 5, Serotonin type 6, Serotonin type 7, Serotonin type 8, other Serotonin types, Trace amine, Angiotensin type 1, Angiotensin type 2, Bombesin, Bradykinin, C5a anaphylatoxin, Fmet-leu-phe, APJ like, Interleukin-8 type A, Interleukin-8 type B, Interleukin-8 type others, C--C Chemokine type 1 through type 11 and other types, C--X--C Chemokine (types 2 through 6 and others), C--X3-C Chemokine, Cholecystokinin CCK, CCK type A, CCK type B, CCK others, Endothelin, Melanocortin (Melanocyte stimulating hormone, Adrenocorticotropic hormone, Melanocortin hormone), Duffy antigen, Prolactin-releasing peptide (GPR10), Neuropeptide Y (type 1 through 7), Neuropeptide Y, Neuropeptide Y other, Neurotensin, Opioid (type D, K, M, X), Somatostatin (type 1 through 5), Tachykinin (Substance P (NK1), Substance K (NK2), Neuromedin K (NK3), Tachykinin like 1, Tachykinin like 2, Vasopressin/vasotocin (type 1 through 2), Vasotocin, Oxytocin/mesotocin, Conopressin, Galanin like, Proteinase-activated like, Orexin &amp; neuropeptides FF.QRFP, Chemokine receptor-like, Neuromedin U like (Neuromedin U, PRXamide), hormone protein (Follicle stimulating hormone, Lutropin-choriogonadotropic hormone, Thyrotropin, Gonadotropin type I, Gonadotropin type II), (Rhod)opsin, Rhodopsin Vertebrate (types 1-5), Rhodopsin Vertebrate type 5, Rhodopsin Arthropod, Rhodopsin Arthropod type 1, Rhodopsin Arthropod type 2, Rhodopsin Arthropod type 3, Rhodopsin Mollusc, Rhodopsin, Olfactory (Olfactory II fam 1 through 13), Prostaglandin (prostaglandin E2 subtype EP1, Prostaglandin E2/D2 subtype EP2, prostaglandin E2 subtype EP3, Prostaglandin E2 subtype EP4, Prostaglandin F2-alpha, Prostacyclin, Thromboxane, Adenosine type 1 through 3, Purinoceptors, Purinoceptor P2RY1-4,6,1 1 GPR91, Purinoceptor P2RY5,8,9,10 GPR35,92,174, Purinoceptor P2RY12-14 GPR87 (UDP-Glucose), Cannabinoid, Platelet activating factor, Gonadotropin-releasing hormone, Gonadotropin-releasing hormone type I, Gonadotropin-releasing hormone type II, Adipokinetic hormone like, Corazonin, Thyrotropin-releasing hormone &amp; Secretagogue, Thyrotropin-releasing hormone, Growth hormone secretagogue, Growth hormone secretagogue like, Ecdysis-triggering hormone (ETHR), Melatonin, Lysosphingolipid &amp; LPA (EDG), Sphingosine 1-phosphate Edg-1, Lysophosphatidic acid Edg-2, Sphingosine 1-phosphate Edg-3, Lysophosphatidic acid Edg-4, Sphingosine 1-phosphate Edg-5, Sphingosine 1-phosphate Edg-6, Lysophosphatidic acid Edg-7, Sphingosine 1-phosphate Edg-8, Edg Other Leukotriene B4 receptor, Leukotriene B4 receptor BLT1, Leukotriene B4 receptor BLT2, Class A Orphan/other, Putative neurotransmitters, SREB, Mas proto-oncogene &amp; Mas-related (MRGs), GPR45 like, Cysteinyl leukotriene, G-protein coupled bile acid receptor, Free fatty acid receptor (GP40, GP41, GP43), Class B Secretin like, Calcitonin, Corticotropin releasing factor, Gastric inhibitory peptide, Glucagon, Growth hormone-releasing hormone, Parathyroid hormone, PACAP, Secretin, Vasoactive intestinal polypeptide, Latrophilin, Latrophilin type 1, Latrophilin type 2, Latrophilin type 3, ETL receptors, Brain-specific angiogenesis inhibitor (BAI), Methuselah-like proteins (MTH), Cadherin EGF LAG (CELSR), Very large G-protein coupled receptor, Class C Metabotropic glutamate/pheromone, Metabotropic glutamate group I through III, Calcium-sensing like, Extracellular calcium-sensing, Pheromone, calcium-sensing like other, Putative pheromone receptors, GABA-B, GABA-B subtype 1, GABA-B subtype 2, GABA-B like, Orphan GPRC5, Orphan GPCR6, Bride of sevenless proteins (BOSS), Taste receptors (T1R), Class D Fungal pheromone, Fungal pheromone A-Factor like (STE2.STE3), Fungal pheromone B like (BAR,BBR,RCB,PRA), Class E cAMP receptors, Ocular albinism proteins, Frizzled/Smoothened family, frizzled Group A (Fz 1&amp;2&amp;4&amp;5&amp;7-9), frizzled Group B (Fz 3 &amp; 6), frizzled Group C (other), Vomeronasal receptors, Nematode chemoreceptors, Insect odorant receptors, and Class Z Archaeal/bacterial/fiingal opsins. 
     In certain embodiments, the HSA binding  10 Fn3 domain fusions described herein may comprise any of the following active polypeptides: BOTOX, Myobloc, Neurobloc, Dysport (or other serotypes of botulinum neurotoxins), alglucosidase alfa, daptomycin, YH-16, choriogonadotropin alfa, filgrastim, cetrorelix, interleukin-2, aldesleukin, teceleukin, denileukin diftitox, interferon alfa-n3 (injection), interferon alfa-n1, DL-8234, interferon, Suntory (gamma-Ia), interferon gamma, thymosin alpha 1, tasonermin, DigiFab, ViperaTAb, EchiTAb, CroFab, nesiritide, abatacept, alefacept, Rebif, eptoterminalfa, teriparatide (osteoporosis), calcitonin injectable (bone disease), calcitonin (nasal, osteoporosis), etanercept, hemoglobin glutamer 250 (bovine), drotrecogin alfa, collagenase, carperitide, recombinant human epidermal growth factor (topical gel, wound healing), DWP-401, darbepoetin alfa, epoetin omega, epoetin beta, epoetin alfa, desirudin, lepirudin, bivalirudin, nonacog alpha, Mononine, eptacog alfa (activated), recombinant Factor VIII+VWF, Recombinate, recombinant Factor VIII, Factor VIII (recombinant), Alphanate, octocog alfa, Factor VIII, palifermin, Indikinase, tenecteplase, alteplase, pamiteplase, reteplase, nateplase.monteplase, follitropin alfa, rFSH, hpFSH, micafungin, pegfilgrastim, lenograstim, nartograstim, sermorelin, glucagon, exenatide, pramlintide, imiglucerase, galsulfase, Leucotropin, molgramostim, triptorelin acetate, histrelin (subcutaneous implant, Hydron), deslorelin, histrelin, nafarelin, leuprolide sustained release depot (ATRIGEL), leuprolide implant (DUROS), goserelin, somatropin, Eutropin, KP-102 program, somatropin, somatropin, mecasermin (growth failure), enfuvirtide, Org-33408, insulin glargine, insulin glulisine, insulin (inhaled), insulin lispro, insulin detemir, insulin (buccal, RapidMist), mecasermin rinfabate, anakinra, celmoleukin, 99 mTc-apcitide injection, myelopid, Betaseron, glatiramer acetate, Gepon, sargramostim, oprelvekin, human leukocyte-derived alpha interferons, Bilive, insulin (recombinant), recombinant human insulin, insulin aspart, mecasermin, Roferon-A, interferon-alpha 2, Alfaferone, interferon alfacon-1, interferon alpha, Avonex recombinant human luteinizing hormone, dornase alfa, trafermin, ziconotide, taltirelin, diboterminalfa, atosiban, becaplermin, eptifibatide, Zemaira, CTC-111, Shanvac-B, HPV vaccine (quadrivalent), NOV-002, octreotide, lanreotide, ancestim, agalsidase beta, agalsidase alfa, laronidase, prezatide copper acetate (topical gel), rasburicase, ranibizumab, Actimmune, PEG-Intron, Tricomin, recombinant house dust mite allergy desensitization injection, recombinant human parathyroid hormone (PTH) 1-84 (sc, osteoporosis), epoetin delta, transgenic antithrombin III, Granditropin, Vitrase, recombinant insulin, interferon-alpha (oral lozenge), GEM-2 IS, vapreotide, idursulfase, omapatrilat, recombinant serum albumin, certolizumab pegol, glucarpidase, human recombinant C1 esterase inhibitor (angioedema), lanoteplase, recombinant human growth hormone, enfuvirtide (needle-free injection, Biojector 2000), VGV-I, interferon (alpha), lucinactant, aviptadil (inhaled, pulmonary disease), icatibant, ecallantide, omiganan, Aurograb, pexiganan acetate, ADI-PEG-20, LDI-200, degarelix, cintredekin besudotox, FavId, MDX-1379, ISAtx-247, liraglutide, teriparatide (osteoporosis), tifacogin, AA-4500, T4N5 liposome lotion, catumaxomab, DWP-413, ART-123, Chrysalin, desmoteplase, amediplase, corifollitropin alpha, TH-9507, teduglutide, Diamyd, DWP-412, growth hormone (sustained release injection), recombinant G-CSF, insulin (inhaled, AIR), insulin (inhaled, Technosphere), insulin (inhaled, AERx), RGN-303, DiaPep277, interferon beta (hepatitis C viral infection (HCV)), interferon alfa-n3 (oral), belatacept, transdermal insulin patches, AMG-531, MBP-8298, Xerecept, opebacan, AIDSVAX, GV-1001, LymphoScan, ranpirnase, Lipoxysan, lusupultide, MP52 (beta-tricalciumphosphate carrier, bone regeneration), melanoma vaccine, sipuleucel-T, CTP-37, Insegia, vitespen, human thrombin (frozen, surgical bleeding), thrombin, TransMID, alfimeprase, Puricase, terlipressin (intravenous, hepatorenal syndrome), EUR-1008M, recombinant FGF-I (injectable, vascular disease), BDM-E, rotigaptide, ETC-216, P-113, MBI-594AN, duramycin (inhaled, cystic fibrosis), SCV-07, OPI-45, Endostatin, Angiostatin, ABT-510, Bowman Birk Inhibitor Concentrate, XMP-629, 99 mTc-Hynic-Annexin V, kahalalide F, CTCE-9908, teverelix (extended release), ozarelix, romidepsin, BAY-50-4798, interleukin-4, PRX-321, Pepscan, iboctadekin, rh lactoferrin, TRU-015, IL-21, ATN-161, cilengitide, Albuferon, Biphasix, IRX-2, omega interferon, PCK-3145, CAP-232, pasireotide, huN901-DM1, ovarian cancer immunotherapeutic vaccine, SB-249553, Oncovax-CL, OncoVax-P, BLP-25, CerVax-16, multi-epitope peptide melanoma vaccine (MART-I, gp100, tyrosinase), nemifitide, rAAT (inhaled), rAAT (dermatological), CGRP (inhaled, asthma), pegsunercept, thymosin beta-4, plitidepsin, GTP-200, ramoplanin, GRASPA, OBI-I, AC-100, salmon calcitonin (oral, eligen), calcitonin (oral, osteoporosis), examorelin, capromorelin, Cardeva, velafermin, 131I-TM-601, KK-220, TP-10, ularitide, depelestat, hematide, Chrysalin (topical), rNAPc2, recombinant Factor VIII (PEGylated liposomal), bFGF, PEGylated recombinant staphylokinase variant, V-10153, SonoLysis Prolyse, NeuroVax, CZEN-002, islet cell neogenesis therapy, rGLP-1, BIM-51077, LY-548806, exenatide (controlled release, Medisorb), AVE-0010, GA-GCB, avorelin, AOD-9604, linaclotide acetate, CETi-I, Hemospan, VAL (injectable), fast-acting insulin (injectable, Viadel), intranasal insulin, insulin (inhaled), insulin (oral, eligen), recombinant methionyl human leptin, pitrakinra subcutaneous injection, eczema), pitrakinra (inhaled dry powder, asthma), Multikine, RG-1068, MM-093, NBI-6024, AT-001, PI-0824, Org-39141, Cpn10 (autoimmune diseases/inflammation), talactoferrin (topical), rEV-131 (ophthalmic), rEV-131 (respiratory disease), oral recombinant human insulin (diabetes), RPI-78M, oprelvekin (oral), CYT-99007 CTLA4-Ig, DTY-001, valategrast, interferon alfa-n3 (topical), IRX-3, RDP-58, Tauferon, bile salt stimulated lipase, Merispase, alkaline phosphatase, EP-2104R, Melanotan-II, bremelanotide, ATL-104, recombinant human microplasmin, AX-200, SEMAX, ACV-I, Xen-2174, CJC-1008, dynorphin A, SI-6603, LAB GHRH, AER-002, BGC-728, malaria vaccine (virosomes, PeviPRO), ALTU-135, parvovirus B 19 vaccine, influenza vaccine (recombinant neuraminidase), malaria/HBV vaccine, anthrax vaccine, Vacc-5q, Vacc-4x, HIV vaccine (oral), HPV vaccine, Tat Toxoid, YSPSL, CHS-13340, PTH(1-34) liposomal cream (Novasome), Ostabolin-C, PTH analog (topical, psoriasis), MBRI-93.02, MTB72F vaccine (tuberculosis), MVA-Ag85 A vaccine (tuberculosis), FAR-404, BA-210, recombinant plague F1V vaccine, AG-702, OxSODro1, rBetV1, Der-p1/Der-p2/Der-p7 allergen-targeting vaccine (dust mite allergy), PR1 peptide antigen (leukemia), mutant ras vaccine, HPV-16 E7 lipopeptide vaccine, labyrinthin vaccine (adenocarcinoma), CML vaccine, WT1-peptide vaccine (cancer), IDD-5, CDX-110, Pentrys, Norelin, CytoFab, P-9808, VT-111, icrocaptide, telbermin (dermatological, diabetic foot ulcer), rupintrivir, reticulose, rGRF, P1A, alpha-galactosidase A, ACE-011, ALTU-140, CGX-1160, angiotensin therapeutic vaccine, D-4F, ETC-642, APP-018, rhMBL, SCV-07 (oral, tuberculosis), DRF-7295, ABT-828, ErbB2-specific immunotoxin (anticancer), DT388IL-3, TST-10088, PRO-1762, Combotox, cholecystokinin-B/gastrin-receptor binding peptides, 1 1 1ln-hEGF, AE-37, trastuzumab-DM1, Antagonist G, IL-12 (recombinant), PM-02734, IMP-321, rhIGF-BP3, BLX-883, CUV-1647 (topical), L-19 based radioimmunotherapeutics (cancer), Re-188-P-2045, AMG-386, DC/I540/KLH vaccine (cancer), VX-001, AVE-9633, AC-9301, NY—ESO—I vaccine (peptides), NA17.A2 peptides, melanoma vaccine (pulsed antigen therapeutic), prostate cancer vaccine, CBP-501, recombinant human lactoferrin (dry eye), FX-06, AP-214, WAP-8294A2 (injectable), ACP-HIP, SUN-11031, peptide YY [3-36] (obesity, intranasal), FGLL, atacicept, BR3-Fc, BN-003, BA-058, human parathyroid hormone 1-34 (nasal, osteoporosis), F-18-CCR1, AT-1001 (celiac disease/diabetes), JPD-003, PTH(7-34) liposomal cream (Novasome), duramycin (ophthalmic, dry eye), CAB-2, CTCE-0214, GlycoPEGylated erythropoietin, EPO-Fc, CNTO-528, AMG-114, JR-013, Factor XIII, aminocandin, PN-951, 716155, SUN-E7001, TH-0318, BAY-73-7977, teverelix (immediate release), EP-51216, hGH (controlled release, Biosphere), OGP-I, sifuvirtide, TV-4710, ALG-889, Org-41259, rhCCIO, F-991, thymopentin (pulmonary diseases), r(m)CRP, hepatoselective insulin, subalin, L 19-IL-2 fusion protein, elafin, NMK-150, ALTU-139, EN-122004, rhTPO, thrombopoietin receptor agonist (thrombocytopenic disorders), AL-108, AL-208, nerve growth factor antagonists (pain), SLV-317, CGX-1007, INNO-105, oral teriparatide (eligen), GEM-OS1, AC-162352, PRX-302, LFn-p24 fusion vaccine (Therapore), EP-1043, S. pneumoniae pediatric vaccine, malaria vaccine, Neisseria meningitidis Group B vaccine, neonatal group B streptococcal vaccine, anthrax vaccine, HCV vaccine (gpE1+gpE2+MF-59), otitis media therapy, HCV vaccine (core antigen+ISCOMATRIX), hPTH(1-34) (transdermal, ViaDerm), 768974, SYN-101, PGN-0052, aviscumine, BIM-23190, tuberculosis vaccine, multi-epitope tyrosinase peptide, cancer vaccine, enkastim, APC-8024, G1-5005, ACC-001, TTS-CD3, vascular-targeted TNF (solid tumors), desmopressin (buccal controlled-release), onercept, TP-9201. 
     Additional Modifications 
     In certain embodiments, the HSA binding  10 Fn3 domains and their fusions may further comprise post-translational modifications. Exemplary post-translational protein modifications include phosphorylation, acetylation, methylation, ADP-ribosylation, ubiquitination, glycosylation, carbonylation, sumoylation, biotinylation or addition of a polypeptide side chain or of a hydrophobic group. As a result, the HSA binding  10 Fn3 domains and their fusions may contain non-amino acid elements, such as lipids, poly- or mono-saccharide, and phosphates. A preferred form of glycosylation is sialylation, which conjugates one or more sialic acid moieties to the polypeptide. Sialic acid moieties improve solubility and serum half-life while also reducing the possible immunogenicity of the protein. See, e.g., Raju et al.  Biochemistry  2001;40:8868-76. Effects of such non-amino acid elements on the functionality of the HSA binding  10 Fn3 domains and their fusions may be tested for their ability to bind a particular HSA binding  10 Fn3 domains and/or the functional role conferred by a specific non- 10 Fn3 moiety in the context of a fusion. 
     E. Vectors &amp; Polynucleotides Embodiments 
     Also provided herein are nucleic acids encoding any of the polypeptides (e.g., polypeptides comprising HSA binding  10 Fn3 domains and fusions thereof) described herein. Accordingly, in certain embodiments, provided herein are nucleic acids encoding any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118, the nucleic acid sequences of which can be readily determined by one skilled in the art from the parent 7016_A01 nucleic acid sequence (SEQ ID NO: 173). 
     As appreciated by those skilled in the art, because of third base degeneracy, almost every amino acid can be represented by more than one triplet codon in a coding nucleotide sequence. In addition, minor base pair changes may result in a conservative substitution in the amino acid sequence encoded but are not expected to substantially alter the biological activity of the gene product. Therefore, a nucleic acid sequence encoding a polypeptide described herein may be modified slightly in sequence and yet still encode its respective gene product. In some embodiments, nucleotide substitutions are introduced so as not to alter the resulting translated amino acid sequence. In certain embodiments, the nucleic acids encoding the HSA binding  10 Fn3 domains and fusions thereof have nucleic acid sequences that encode the amino acid substitutions (relative to SEQ ID NO: 23) described herein. 
     Nucleic acids encoding any of the various proteins or polypeptides disclosed herein may be synthesized chemically. Codon usage may be selected so as to improve expression in a cell. Such codon usage will depend on the cell type selected. Specialized codon usage patterns have been developed for E. coli and other bacteria, as well as mammalian cells, plant cells, yeast cells and insect cells. See for example: Mayfield et al., PNAS 2003;100:438-42; Sinclair et al.  Protein Expr Purif  2002;26::96-105; Connell.,  Curr Opin Biotechnol  2001;12:446-9; Makrides et al. Microbiol Rev 1996;60:512-38; and Sharp et al. Yeast 1991;7:657-78. 
     General techniques for nucleic acid manipulation are within the purview of one skilled in the art and are also described for example in Sambrook et al., Molecular Cloning: A Laboratory Manual, Vols. 1-3, Cold Spring Harbor Laboratory Press, 2 ed., 1989, or F. Ausubel et al., Current Protocols in Molecular Biology (Green Publishing and Wiley-Interscience: New York, 1987) and periodic updates, herein incorporated by reference. The DNA encoding a protein is operably linked to suitable transcriptional or translational regulatory elements derived from mammalian, viral, or insect genes. Such regulatory elements include a transcriptional promoter, an optional operator sequence to control transcription, a sequence encoding suitable mRNA ribosomal binding sites, and sequences that control the termination of transcription and translation. The ability to replicate in a host, usually conferred by an origin of replication, and a selection gene to facilitate recognition of transformants are additionally incorporated. Suitable regulatory elements are well-known in the art. 
     The polypeptides and fusions thereof described herein may be produced as a fusion protein with a heterologous polypeptide, which is preferably a signal sequence or other polypeptide having a specific cleavage site at the N-terminus of the mature protein or polypeptide. The heterologous signal sequence selected preferably is one that is recognized and processed (i.e., cleaved by a signal peptidase) by the host cell. For prokaryotic host cells that do not recognize and process a native signal sequence, the signal sequence is substituted by a prokaryotic signal sequence selected, for example, from the group of the alkaline phosphatase, penicillinase, 1 pp, or heat-stable enterotoxin II leaders. For yeast secretion, the native signal sequence may be substituted by, e.g., the yeast invertase leader, a factor leader (including Saccharomyces and Kluyveromyces alpha-factor leaders), or acid phosphatase leader, the C. albicans glucoamylase leader, or the signal described in PCT Publication No. WO 90/13646. In mammalian cell expression, mammalian signal sequences as well as viral secretory leaders, for example, the herpes simplex gD signal, are available. The DNA for such precursor regions may be ligated in reading frame to DNA encoding the protein. 
     Expression vectors used in eukaryotic host cells (e.g., yeast, fungi, insect, plant, animal, human, or nucleated cells from other multicellular organisms) will also contain sequences necessary for the termination of transcription and for stabilizing the mRNA. Such sequences are commonly available from the 5&#39; and, occasionally 3&#39;, untranslated regions of eukaryotic or viral DNAs or cDNAs. These regions contain nucleotide segments transcribed as polyadenylated fragments in the untranslated portion of the mRNA encoding the multivalent antibody. One useful transcription termination component is the bovine growth hormone polyadenylation region. See PCT Publication No. WO 94/11026 and the expression vector disclosed therein. 
     The recombinant DNA can also include any type of protein tag sequence that may be useful for purifying the protein. Examples of protein tags include but are not limited to a histidine tag, a FLAG tag, a myc tag, an HA tag, or a GST tag. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts can be found in Cloning Vectors: A Laboratory Manual, (Elsevier, New York, 1985), the relevant disclosure of which is hereby incorporated by reference. 
     The expression construct is introduced into the host cell using a method appropriate to the host cell, as will be apparent to one of skill in the art. A variety of methods for introducing nucleic acids into host cells are known in the art, including, but not limited to, electroporation; transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; microprojectile bombardment; lipofection; and infection (where the vector is an infectious agent). 
     Suitable host cells include prokaryotes, yeast, mammalian cells, or bacterial cells. Suitable bacteria include gram negative or gram positive organisms, for example,  E. coli  or  Bacillus spp . Yeast, preferably from the Saccharomyces species, such as  S. cerevisiae , may also be used for production of polypeptides. Various mammalian or insect cell culture systems can also be employed to express recombinant proteins. Baculovirus systems for production of heterologous proteins in insect cells are reviewed by Luckow and Summers, (Bio/Technology, 6:47, 1988). In some instance it will be desired to produce proteins in vertebrate cells, such as for glycosylation, and the propagation of vertebrate cells in culture (tissue culture) has become a routine procedure. Examples of suitable mammalian host cell lines include endothelial cells, COS-7 monkey kidney cells, CV-1, L cells, C127, 3T3, Chinese hamster ovary (CHO), human embryonic kidney cells, HeLa, 293, 293T, and BHK cell lines. For many applications, the small size of the protein multimers described herein would make  E. coli  the preferred method for expression. 
     F. Protein Production 
     Host cells are transformed with the herein-described expression or cloning vectors for protein production and cultured in conventional nutrient media modified as appropriate for inducing promoters, selecting transformants, or amplifying the genes encoding the desired sequences. 
     The host cells used to produce the HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, may be cultured in a variety of media. Commercially available media such as Ham’s F10 (Sigma), Minimal Essential Medium ((MEM), (Sigma)), RPMI-1640 (Sigma), and Dulbecco’s Modified Eagle’s Medium ((DMEM), (Sigma)) are suitable for culturing the host cells. In addition, any of the media described in Ham et al.,  Meth Enz  58:44 (1979), Barnes et al.,  Anal Biochem  102:255 (1980), U.S. Patent Nos. 4,767,704; 4,657,866; 4,927,762; 4,560,655; or 5,122,469; WO90/03430; WO87/00195; or U.S. Patent No. Re. 30,985 may be used as culture media for the host cells. Any of these media may be supplemented as necessary with hormones and/or other growth factors (such as insulin, transferrin, or epidermal growth factor), salts (such as sodium chloride, calcium, magnesium, and phosphate), buffers (such as HEPES), nucleotides (such as adenosine and thymidine), antibiotics (such as GENTAMYCIN™ drug), trace elements (defined as inorganic compounds usually present at final concentrations in the micromolar range), and glucose or an equivalent energy source. Any other necessary supplements may also be included at appropriate concentrations that would be known to those skilled in the art. The culture conditions, such as temperature, pH, and the like, are those previously used with the host cell selected for expression, and will be apparent to the ordinarily skilled artisan. 
     HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, can also be produced using cell-free translation systems. For such purposes the nucleic acids encoding the fibronectin based scaffold protein must be modified to allow in vitro transcription to produce mRNA and to allow cell-free translation of the mRNA in the particular cell-free system being utilized (eukaryotic such as a mammalian or yeast cell-free translation system or prokaryotic such as a bacterial cell-free translation system). 
     The HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, can also be produced by chemical synthesis (e.g., by the methods described in Solid Phase Peptide Synthesis, 2nd ed., 1984, The Pierce Chemical Co., Rockford, IL). Modifications to the fibronectin based scaffold protein can also be produced by chemical synthesis. 
     The HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, can be purified by isolation/purification methods for proteins generally known in the field of protein chemistry. Non-limiting examples include extraction, recrystallization, salting out (e.g., with ammonium sulfate or sodium sulfate), centrifugation, dialysis, ultrafiltration, adsorption chromatography, ion exchange chromatography, hydrophobic chromatography, normal phase chromatography, reversed-phase chromatography, gel filtration, gel permeation chromatography, affinity chromatography, electrophoresis, countercurrent distribution or any combinations of these. After purification, serum albumin binders and fusion molecules described herein may be exchanged into different buffers and/or concentrated by any of a variety of methods known to the art, including, but not limited to, filtration and dialysis. 
     The purified HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, are preferably at least 85% pure, more preferably at least 95% pure, and most preferably at least 98% pure. Regardless of the exact numerical value of the purity, the HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, are sufficiently pure for use as a pharmaceutical product. 
     The HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, may also be produced using the following protocols. 
     An Adnectin may be cloned into the PET9d vector upstream of a HIS 6 tag and transformed into  E. coli  BL21 DE3 plysS cells are inoculated in 5 ml LB medium containing 50 µg/mL kanamycin in a 24-well format and grown at 37° C. overnight. Fresh 5 ml LB medium (50 µg/mL kanamycin) cultures are prepared for inducible expression by aspiration of 200 µl from the overnight culture and dispensing it into the appropriate well. The cultures are grown at 37° C. until A 600  0.6-0.9. After induction with 1 mM isopropyl-β-thiogalactoside (IPTG), the culture is expressed for 6 hours at 30° C. and harvested by centrifugation for 10 minutes at 2750 g at 4° C. 
     Cell pellets (in 24-well format) are lysed by resuspension in 450 µl of Lysis buffer (50 mM NaH 2 PO 4 , 0.5 M NaCl, 1x Complete™ Protease Inhibitor Cocktail-EDTA free (Roche), 1 mM PMSF, 10 mM CHAPS, 40 mM imidazole, 1 mg/ml lysozyme, 30 µg/ml DNAse, 2 µg/ml aprotonin, pH 8.0) and shaken at room temperature for 1-3 hours. Lysates are cleared and re-racked into a 96-well format by transfer into a 96-well Whatman GF/D Unifilter fitted with a 96-well, 1.2 ml catch plate and filtered by positive pressure. The cleared lysates are transferred to a 96-well Nickel or Cobalt-Chelating Plate that had been equilibrated with equilibration buffer (50 mM NaH 2 PO 4 , 0.5 M NaCl, 40 mM imidazole, pH 8.0) and are incubated for 5 min. Unbound material is removed by positive pressure. The resin is washed twice with 0.3 ml/well with Wash buffer #1 (50 mM NaH 2 PO 4 , 0.5 M NaCl, 5 mM CHAPS, 40 mM imidazole, pH 8.0). Each wash is removed by positive pressure. Prior to elution, each well is washed with 50 µl Elution buffer (PBS + 20 mM EDTA), incubated for 5 min, and this wash is discarded by positive pressure. Protein is eluted by applying an additional 100 µl of Elution buffer to each well. After a 30 minute incubation at room temperature, the plate(s) are centrifuged for 5 minutes at 200 g and eluted protein collected in 96-well catch plates containing 5 µl of 0.5 M MgCl2 added to the bottom of elution catch plate prior to elution. Eluted protein is quantified using a total protein assay with wild-type  10 Fn3 domain as the protein standard. 
     For expression of insoluble Adnectins, the nucleic acid encoding the Adnectin(s), followed by the HIS 6 tag, are cloned into a pET9d (EMD Bioscience, San Diego, CA) vector and are expressed in E. coli HMS 174 cells. Twenty ml of an inoculum culture (generated from a single plated colony) is used to inoculate 1 liter of LB medium containing 50 µg/ml carbenicillin and 34 µg/ml chloramphenicol. The culture is grown at 37° C. until A 600  0.6-1.0. After induction with 1 mM isopropyl-β-thiogalactoside (IPTG) the culture is grown for 4 hours at 30° C. and is harvested by centrifugation for 30 minutes at &gt; 10,000 g at 4° C. Cell pellets are frozen at -80° C. The cell pellet is resuspended in 25 ml of lysis buffer (20 mM aH2PO 4 , 0.5 M NaCl, 1x Complete Protease Inhibitor Cocktail-EDTA free (Roche), 1 mM PMSF, pH 7.4) using an ULTRA-TURRAX® homogenizer (IKA works) on ice. Cell lysis is achieved by high pressure homogenization (&gt;18,000 psi) using a Model M-1 10S MICROFLUIDIZER® (Microfluidics). The insoluble fraction is separated by centrifugation for 30 minutes at 23,300 g at 4° C. The insoluble pellet recovered from centrifugation of the lysate is washed with 20 mM sodium phosphate/500 mM NaCl, pH7.4. The pellet is resolubilized in 6.0 M guanidine hydrochloride in 20 mM sodium phosphate/500 M NaCl pH 7.4 with sonication followed by incubation at 37° C. for 1- 2 hours. The resolubilized pellet is filtered to 0.45 µm and loaded onto a Histrap column equilibrated with the 20 mM sodium phosphate/500 M NaCl/6.0 M guanidine pH 7.4 buffer. After loading, the column is washed for an additional 25 CV with the same buffer. Bound protein is eluted with 50 mM Imidazole in 20 mM sodium phosphate/500 mM NaCl/6.0 M guan-HCl pH7.4. The purified protein is refolded by dialysis against 50 mM sodium acetate/150 mM NaCl pH 4.5. 
     For expression of soluble Adnectins, the nucleic acid encoding the Adnectin(s), followed by the HIS 6 tag, are cloned into a pET9d (EMD Bioscience, San Diego, CA) vector and are expressed in  E. coli  HMS 174 cells. Twenty ml of an inoculum culture (generated from a single plated colony) is used to inoculate 1 liter of LB medium containing 50 µg/ml carbenicillin and 34 µg/ml chloramphenicol. The culture is grown at 37° C. until A 600  0.6-1.0. After induction with 1 mM isopropyl-β-thiogalactoside (IPTG), the culture is grown for 4 hours at 30° C. and harvested by centrifugation for 30 minutes at &gt;10,000 g at 4° C. Cell pellets are frozen at -80° C. The cell pellet is resuspended in 25 ml of lysis buffer (20 mM NaH 2 PO 4 , 0.5 M NaCl, 1x Complete Protease Inhibitor Cocktail-EDTA free (Roche), 1 mM PMSF, pH 7.4) using an ULTRA-TURRAX® homogenizer (IKA works) on ice. Cell lysis is achieved by high pressure homogenization (&gt; 18,000 psi) using a Model M-1 10S MICROFLUIDIZER® (Microfluidics). The soluble fraction is separated by centrifugation for 30 minutes at 23,300 g at 4° C. The supernatant is clarified via 0.45 µm filter. The clarified lysate is loaded onto a Histrap column (GE) pre-equilibrated with 20 mM sodium phosphate/500 M NaCl pH 7.4. The column is then washed with 25 column volumes of the same buffer, followed by 20 column volumes of 20 mM sodium phosphate/500 M NaCl/ 25 mM Imidazole, pH 7.4 and then 35 column volumes of 20 mM sodium phosphate/500 M NaCl/40 mM Imidazole, pH 7.4. Protein is eluted with 15 column volumes of 20 mM sodium phosphate/500 M NaCl/500 mM Imidazole, pH 7.4, fractions are pooled based on absorbance at A 2 so and dialyzed against 1x PBS, 50 mM Tris, 150 mM NaCl; pH 8.5 or 50 mM NaOAc; 150 mM NaCl; pH4.5. Any precipitate is removed by filtering at 0.22 µm. 
     G. Imaging, Diagnostic, and Other Applications 
     The HSA binding  10 Fn3 fusions provided herein may be used to treat a variety of diseases and disorders, based on the identity of the heterologous molecule fused to the HSA binding  10 Fn3 domain. The applications for the HSA binding  10 Fn3 fusions may be determined by the skilled artisan based on the knowledge in the art and the information provided herein. Uses for various HSA binding  10 Fn3 fusion proteins are described in detail herein. HSA binding  10 Fn3fusions may be administered to any mammalian subject or patient, including both human and non-human organisms. 
     The HSA binding  10 Fn3 domains and fusion molecules described herein can be detectably labeled and used to contact cells expressing, e.g., a protein bound by the fusion molecule for imaging or diagnostic applications. Any method known in the art for conjugating a protein to the detectable moiety may be employed, including those methods described by Hunter et al.,  Nature  1962;144:945; David et al.,  Biochemistry  1974;13:1014; Pain et al.,  J Immunol Meth  1981;40:219; and Nygren,  Histochem and Cytochem  1982;30:407. 
     In certain embodiments, the HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, are further attached to a label that is able to be detected (e.g., the label can be a radioisotope, fluorescent compound, enzyme or enzyme co-factor). The label may be a radioactive agent, such as: radioactive heavy metals such as iron chelates, radioactive chelates of gadolinium or manganese, positron emitters of oxygen, nitrogen, iron, carbon, or gallium,  43 K,  52 Fe,  57 Co,  67 Cu,  67 Ga,  68 Ga,  123 I,  125 I,  131 I,  132 I, or  99 Tc. In certain embodiments, the label can be a fluorescent or chemiluminescent compound, such as fluorescein isothiocyanate, rhodamine, or luciferin; or an enzyme, such as alkaline phosphatase, beta-galactosidase or horseradish peroxidase. The HSA binding  10 Fn3 domain or fusion molecule affixed to such a moiety may be used as an imaging agent and is administered in an amount effective for diagnostic use in a mammal such as a human and the localization and accumulation of the imaging agent is then detected. The localization and accumulation of the imaging agent may be detected by radioscintigraphy, nuclear magnetic resonance imaging, computed tomography or positron emission tomography. As will be evident to the skilled artisan, the amount of radioisotope to be administered is dependent upon the radioisotope. Those having ordinary skill in the art can readily formulate the amount of the imaging agent to be administered based upon the specific activity and energy of a given radionuclide used as the active moiety. 
     The HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, also are useful as affinity purification agents. In this process, the proteins are immobilized on a suitable support, such a Sephadex resin or filter paper, using methods well known in the art. The proteins can be employed in any known assay method, such as competitive binding assays, direct and indirect sandwich assays, and immunoprecipitation assays (Zola, Monoclonal Antibodies: A Manual of Techniques, pp. 147-158 (CRC Press, Inc., 1987)). 
     H. Biophysical and Biochemical Characterization 
     In Vitro Assays for Binding Affinity 
     Adnectins that bind to HSA can be identified using various in vitro assays. In certain embodiments, the assays are high-throughput assays that allow for screening multiple candidate Adnectins simultaneously. 
     Exemplary assays for determining the binding affinity of an Adnectin to its target includes, but is not limited to, solution phase methods such as the kinetic exclusion assay (KinExA) (Blake et al., JBC 1996; 271:27677-85; Drake et al.,  Anal Biochem  2004; 328:35-43), surface plasmon resonance (SPR) with the Biacore® system (Uppsala, Sweden) (Welford et al.,  Opt. Quant. Elect  1991; 23:1; Morton and Myszka,  Methods in Enzymology  1998; 295:268) and homogeneous time resolved fluorescence (HTRF) assays (Newton et al.,  J Biomol Screen  2008; 13:674-82; Patel et al.,  Assay Drug Dev Technol  2008; 6:55-68). 
     In certain embodiments, biomolecular interactions can be monitored in real time with the Biacore® system, which uses SPR to detect changes in the resonance angle of light at the surface of a thin gold film on a glass support due to changes in the refractive index of the surface up to 300 nm away. Biacore analysis generates association rate constants, dissociation rate constants, equilibrium dissociation constants, and affinity constants. Binding affinity is obtained by assessing the association and dissociation rate constants using a Biacore surface plasmon resonance system (Biacore, Inc.). A biosensor chip is activated for covalent coupling of the target. The target is then diluted and injected over the chip to obtain a signal in response units of immobilized material. Since the signal in resonance units (RU) is proportional to the mass of immobilized material, this represents a range of immobilized target densities on the matrix. Association and dissociation data are fit simultaneously in a global analysis to solve the net rate expression for a 1:1 bimolecular interaction, yielding best fit values for k on , k off,  and R max  (maximal response at saturation). Equilibrium dissociation constants for binding, K D , are calculated from SPR measurements as k off /k on . 
     The off-rates (kd), on-rates (ka), and dissociation equilibrium constants (K D ) of the HSA binding  10 Fn3 domains described herein for binding to serum albumin from human, cynomolgus monkey, rat, mouse can be determined using SPR Biacore analysis. In certain embodiments, the respective serum albumins are mobilized on a Biacore CM5 chip to a surface density of ~1200 RU using standard NHS/EDC coupling. A concentration range (0.25 nM - 5 uM) of the HSA binding  10 Fn3 domain to be tested is applied in HBS-P+ (0.01 M HEPES pH 7.4, 0.15 M NaCl, 0.05% v/v surfactant P-20) or Acetate (0.02 mM sodium acetate pH 5.5, 0.15 M NaCl, 0.05% v/v surfactant P-20) running buffers to the immobilized albumins. Kinetic measurements are carried out using a 3 min association and 6-10 min dissociation phase. Kinetic traces of reference-subtracted sensograms are fit to a 1:1 binding model using Biaevaluation software. 
     It should be understood that the assays described herein above are exemplary, and that any method known in the art for determining the binding affinity between proteins (e.g., fluorescence based-transfer (FRET), enzyme-linked immunosorbent assay, and competitive binding assays (e.g., radioimmunoassays)) can be used to assess the binding affinities of the rum albumin binding  10 Fn3 domains described herein. 
     In certain embodiments, the melting temperature (T m ) of HSA binding  10 Fn3 domains described herein, of fusion proteins comprising such, is at least 50° C., such as at least 51° C., at least 52° C., at least 53° C., at least 54° C., at least 55° C., at least 56° C., at least 57° C., at least 58° C., at least 59° C., at least 60° C., at least 61° C., at least 62° C., at least 63° C., at least 64° C., at least 65° C., at least 66° C., at least 67° C., at least 68° C., at least 69° C., at least 70° C., at least 71° C., at least 72° C., at least 73° C., at least 74° C., or at least 75° C., when measured using differential scanning calorimetry (DSC) or thermal scanning fluorescence (TSF). 
     In certain embodiments, the melting temperature (T m ) of HSA binding  10 Fn3 domains described herein, or fusion proteins comprising such, is 50-75° C., such as 51-75° C., 52-75° C., 53-75° C., 54-75° C., 55-75° C., 56-75° C., 57-75° C., 58-75° C., 59-75° C., 60-75° C., 61-75° C., 62-75° C., 63-75° C., 64-75° C., 65-75° C., 66-75° C., 67-75° C., 68-75° C., 69-75° C., 70-75° C., 50-74° C., 50-73° C., 50-72° C., 50-71° C., 50-70° C., 50-69° C., 50-68° C., 50-67° C., 50-66° C., 50-65° C., 50-64° C., 50-63° C., 50-62° C., 50-61° C., 50-60° C., 50-59° C., 50-58° C., 50-57° C., 50-56° C., 50-55° C., 51-74° C., 52-73° C., 53-71° C., 54-70° C., or 55-65° C., when measured using differential scanning calorimetry (DSC) or thermal scanning fluorescence (TSF). 
     I. Therapeutic In Vivo Uses 
     Provided herein are HSA binding  10 Fn3 domains and fusion molecules comprising such that are useful in the treatment of disorders. In the case of fusion proteins comprising a HSA binding  10 Fn3 domain, the diseases or disorders that may be treated will be dictated by the binding specificity of the moiety, e.g., a second  10 Fn3 domain that is linked to the Adnectin. As described herein, fibronectin based scaffold proteins may be designed to bind to any target of interest. In one embodiment, the target is PCSK9. Fibronectin based scaffold proteins that bind to PSCK9 and the fusion proteins comprising such can be used to treat atherosclerosis, hypercholesterolemia and other cholesterol related diseases. 
     The application also provides methods for administering fibronectin based scaffold proteins to a subject. In certain embodiments, the subject is a human. In certain embodiments, the fibronectin based scaffold proteins are pharmaceutically acceptable to a mammal, in particular a human. A “pharmaceutically acceptable” composition refers to a composition that is administered to an animal without significant adverse medical consequences. Examples of pharmaceutically acceptable compositions include compositions comprising polypeptides comprising  10 Fn3 domains that lack the integrin-binding domain (RGD) and compositions that are essentially endotoxin or pyrogen free or have very low endotoxin or pyrogen levels. 
     J. Formulations and Administration 
     Provided herein are methods for administering a moiety (e.g., a therapeutic moiety) fused to a HSA binding  10 Fn3 domain, wherein the half-life of the moiety is extended when fused to the HSA binding  10 Fn3 domain. Techniques and dosages for administration of the fusion constructs will vary depending on the type of therapeutic moiety fused to the HSA binding  10 Fn3 domain and the specific condition being treated but can be readily determined by the skilled artisan. In general, regulatory agencies require that a protein reagent to be used as a therapeutic is formulated so as to have acceptably low levels of pyrogens. Accordingly, therapeutic formulations will generally be distinguished from other formulations in that they are substantially pyrogen free, or at least contain no more than acceptable levels of pyrogen as determined by the appropriate regulatory agency (e.g., FDA). 
     In certain embodiments, pharmaceutical formulations of HSA binding  10 Fn3 domains and fusion molecules comprising such, as described herein, comprise, e.g., 1-20 mM succinic acid, 2-10% sorbitol, and 1-10% glycine at pH 4.0-7.0. In an exemplary embodiment, pharmaceutical formulations of HSA binding  10 Fn3 domains and their fusion molecules comprise, e.g., 10 mM succinic acid, 8% sorbitol, and 5% glycine at pH 6.0. 
     In certain embodiments, the HSA binding  10 Fn3 domains and fusions comprising such, as described herein, are pharmaceutically acceptable to a mammal, in particular a human. A “pharmaceutically acceptable” polypeptide refers to a polypeptide that is administered to an animal without significant adverse medical consequences. Examples of pharmaceutically acceptable HSA binding  10 Fn3 domain and fusions comprising such, as described herein, include  10 Fn3 domains that lack the integrin-binding domain (RGD) and compositions of HSA binding  10 Fn3 domains or HSA binding  10 Fn3 domain fusions that are essentially endotoxin free or have very low endotoxin levels. 
     Compositions (e.g., therapeutic compositions) may be administered with a carrier (e.g., a pharmaceutically acceptable diluent, carrier, or excipient), in unit dosage form. Administration may be parenteral (e.g., intravenous, subcutaneous), oral, or topical, as non-limiting examples. The composition can be in the form of a pill, tablet, capsule, liquid, or sustained release tablet for oral administration; a liquid for intravenous, subcutaneous or parenteral administration; or a gel, lotion, ointment, cream, or a polymer or other sustained release vehicle for local administration. 
     Methods well known in the art for making formulations are found, for example, in “Remington: The Science and Practice of Pharmacy” (20th ed., ed. A. R. Gennaro A R., 2000, Lippincott Williams &amp; Wilkins, Philadelphia, Pa.). Formulations for parenteral administration may, for example, contain excipients, sterile water, saline, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, or hydrogenated napthalenes. Biocompatible, biodegradable lactide polymer, lactide/glycolide copolymer, or polyoxyethylene-polyoxypropylene copolymers may be used to control the release of the compounds. Nanoparticulate formulations (e.g., biodegradable nanoparticles, solid lipid nanoparticles, liposomes) may be used to control the biodistribution of the compounds. Other potentially useful parenteral delivery systems include ethylene-vinyl acetate copolymer particles, osmotic pumps, implantable infusion systems, and liposomes. The concentration of the compound in the formulation varies depending upon a number of factors, including the dosage of the drug to be administered, and the route of administration. 
     The polypeptide may be optionally administered as a pharmaceutically acceptable salt, such as non-toxic acid addition salts or metal complexes that are commonly used in the pharmaceutical industry. Examples of acid addition salts include organic acids such as acetic, lactic, pamoic, maleic, citric, malic, ascorbic, succinic, benzoic, palmitic, suberic, salicylic, tartaric, methanesulfonic, toluenesulfonic, or trifluoroacetic acids or the like; polymeric acids such as tannic acid, carboxymethyl cellulose, or the like; and inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid phosphoric acid, or the like. Metal complexes include zinc, iron, and the like. In one example, the polypeptide is formulated in the presence of sodium acetate to increase thermal stability. 
     Formulations for oral use include tablets containing the active ingredient(s) in a mixture with non-toxic pharmaceutically acceptable excipients. These excipients may be, for example, inert diluents or fillers (e.g., sucrose and sorbitol), lubricating agents, glidants, and anti-adhesives (e.g., magnesium stearate, zinc stearate, stearic acid, silicas, hydrogenated vegetable oils, or talc). 
     Formulations for oral use may also be provided as chewable tablets, or as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium. 
     A therapeutically effective dose refers to a dose that produces the therapeutic effects for which it is administered. The exact dose will depend on the disorder to be treated, and may be ascertained by one skilled in the art using known techniques. In general, the HSA binding  10 Fn3 domain or HSA binding  10 Fn3 domain fusion is administered at about 0.01 µg/kg to about 50 mg/kg per day, preferably 0.01 mg/kg to about 30 mg/kg per day, most preferably 0.1 mg/kg to about 20 mg/kg per day. The polypeptide may be given daily (e.g., once, twice, three times, or four times daily) or less frequently (e.g., once every other day, once or twice weekly, once every two weeks, or monthly). In addition, as is known in the art, adjustments for age as well as the body weight, general health, sex, diet, time of administration, drug interaction, and the severity of the disease may be necessary, and will be ascertainable with routine experimentation by those skilled in the art. 
     K. Exemplary Embodiments 
     Embodiment 1. A polypeptide comprising a fibronectin type III tenth ( 10 Fn3) domain, wherein the  10 Fn3 domain binds to human serum albumin (HSA) with a K D  or 1 µM or less and comprises AB, BC, CD, DE, EF, and FG loops, wherein the CD loop has 1, 2, or 3 amino acid substitutions, and the FG loop optionally has 1, 2, or 3 amino acid substitutions, relative to the CD and FG loops of a  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23, and wherein the serum half-life of a moiety (e.g., polypeptide) that is linked to the  10 Fn3 domain is extended relative to that of the moiety that is not linked to the  10 Fn3 domain. 
     Embodiment 2. The polypeptide of embodiment 1, wherein the polypeptide binds to HSA with an off-rate (kd) that is greater than the kd of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Embodiment 3. The polypeptide of embodiment 1 or 2, wherein the polypeptide binds to HSA with an on-rate (ka) that is within an order of magnitude (i.e., within 10-fold) of the ka of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Embodiment 4. The polypeptide of any one of embodiments 1-3, wherein the CD loop has 2 amino acid substitutions relative to the corresponding CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Embodiment 5. The polypeptide of any one of embodiments 1-3, wherein the CD loop has 1 amino acid substitution relative to the CD loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Embodiment 6. The polypeptide of any one of embodiments 1-3, wherein the FG loop has 1 amino acid substitution relative to the FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Embodiment 7. The polypeptide of any one of embodiments 1-3, wherein the CD loop has 1 amino acid substitution and the FG loop has 1 substitution relative to the CD loop and FG loop of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23. 
     Embodiment 8. The polypeptide of embodiment 4, wherein the 2 amino acid substitutions are selected from the group consisting of:
     (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A.   

     Embodiment 9. The polypeptide of embodiment 5, wherein the 1 amino acid substitution is selected from the group consisting of:
     (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A.   

     Embodiment 10. The polypeptide of embodiment 9, wherein the tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with serine (S). 
     Embodiment 11. The polypeptide of embodiment 9, wherein the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with threonine (T). 
     Embodiment 12. The polypeptide of embodiment 9, wherein the tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with glutamine (Q). 
     Embodiment 13. The polypeptide of embodiment 6, wherein the lysine (K) at position 12 of the FG loop (SEQ ID NO: 29) is substituted with an amino acid selected from A, T, or S. 
     Embodiment 14. The polypeptide of embodiment 7, wherein
     a) the 1 amino acid substitution in the CD loop selected from the group consisting of 
   (i) the arginine (R) at position 2 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, E, A, Q, or N;   (ii) the glutamine (Q) at position 5 of the CD loop (SEQ ID NO: 28) is substituted with D;   (iii) the tyrosine (Y) at position 7 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S or A;   (iv) the leucine (L) at position 10 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from S, T, or A;   (v) the leucine (L) at position 13 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A;   (vi) the tyrosine (Y) at position 14 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from A or T;   (vii) the isoleucine (I) at position 15 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from D, S, or A; and   (viii) The tyrosine (Y) at position 16 of the CD loop (SEQ ID NO: 28) is substituted with an amino acid selected from Q, E, S, or A; and   
   b) the lysine at position 12 of the FG loop (SEQ ID NO: 29) is substituted with an amino acid selected from A, T, or S.   

     Embodiment 15. The polypeptide of any one of the preceding embodiments, wherein the polypeptide comprises an amino acid sequence at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% identical to the non-CD loop regions of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. 
     Embodiment 16. The polypeptide of any one of the preceding embodiments, wherein the polypeptide comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% identical to any one of SEQ ID NOs: 30-34, 36-40, 42-46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 61, 62, 63, 65-68, 70, 71, 73-76, 78, 79, 81-84, 86, 87, 89-98, 100-109, and 111-118. 
     Embodiment 17. The polypeptide of any one of the preceding embodiments, wherein the  10 Fn3 domain binds to domain I-II of HSA. 
     Embodiment 18. The polypeptide of any one of the preceding embodiments, wherein the off-rate of the polypeptide to the off-rate of the  10 Fn3 domain comprising the amino acid sequence set forth in SEQ ID NO: 23 has a ratio of at least about 3. 
     Embodiment 19. The polypeptide of embodiment 17, wherein the ratio is at least about 25. 
     Embodiment 20. The polypeptide of embodiment 17, wherein the ratio is at least about 50. 
     Embodiment 21. The polypeptide of any one of the preceding embodiments, wherein the polypeptide comprises a heterologous protein. 
     Embodiment 22. The polypeptide of embodiment 20, wherein the heterologous protein is a therapeutic moiety. 
     Embodiment 23. The polypeptide of embodiment 21 or 22, wherein the heterologous protein is a polypeptide comprising a  10 Fn3 domain. 
     Embodiment 24. A composition comprising the polypeptide or fusion polypeptide of any one of the preceding embodiments, and a carrier. 
     Embodiment 25. An isolated nucleic acid molecule encoding the polypeptide of any one of embodiments 1-23. 
     Embodiment 26. An expression vector comprising the nucleotide sequence encoding the polypeptide of any one of embodiments 1-23. 
     Embodiment 27. A cell comprising the nucleic acid molecule of embodiment 25 or expression vector of embodiment 26. 
     Embodiment 28. A method of producing the polypeptide of any one of embodiments 1-23 comprising culturing the cell of embodiment 27 under conditions suitable for expressing the polypeptide, and purifying the polypeptide. 
     Embodiment 29. A method of enhancing the half-life of a moiety, comprising linking to the moiety a human serum albumin binding polypeptide of any one of embodiments 1-23. 
     The contents of all figures and all references, Genbank sequences, patents and published patent applications cited throughout this application are expressly incorporated herein by reference. In particular, the disclosure of PCT Application No. PCT/US2015/021535 and WO2011/140086 are expressly incorporated herein by reference. 
     The above disclosure generally describes the present disclosure, which is further exemplified by the following examples. These specific examples are described solely for purposes of illustration, and are not intended to limit the scope of this disclosure. Although specific targets, terms, and values have been employed herein, such targets, terms, and values will likewise be understood as exemplary and non-limiting to the scope of this disclosure. 
     EXAMPLES 
     Example 1: Generation of Human Serum Albumin Binding ADX_2629_E06-Based Variant  10 Fn3 Domains 
     The Adnectin ADX_7016_A01 (also referred to as a PKE2 Adnectin herein) was isolated as a polypeptide that binds to domain I-II of HSA with the following core sequence: 
     
       
         
           
               
            
               
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FTVPGSKSTATISGLKPGVDYTIT 
               
               
                 VYA VTGSGESPASSKP ISINYRT (SEQ ID NO: 23; the CD and FG loops are 
               
               
                 underlined) 
               
            
           
         
       
     
     ADX_7016_A01 has low immunogenicity and binds to HSA with a K D  of about 3-6 nM. A polypeptide comprising a PCSK9-binding Adnectin fused to ADX_7016_A01 has a half-life of about 82 hours in mice. In order to increase the versatility of half-live ranges of fusion partners (e.g., in certain situations, a shorter half life than that conferred by ADX_7016_A01 may be preferred), the CD and/or FG loop of ADX_7016_A01 was subjected to mutagenesis (single or double substitutions) and Adnectins that exhibited a lower off-rate (kd) than ADX_7016_A01 were identified. These Adnectins are herein referred to as “PKE3” Adnectins. 
     Single amino acid substitutions in the CD or FG loop (relative to the CD or FG loop of ADX_7016_A01) that retain the low immunogenicity of the polypeptide were generated in order to identify a series of molecules with a range of different affinities for HSA (K D  expected in the low nM to µM range). 
     A homology model was produced for ADX_7016_A01 (based on its parent Adnectin) using standard homology modeling tools within Molecular Operating Environment (MOE), Chemical Computing Group Inc., Montreal, QC, Canada). The modeled binding site of ADX_7016_A01 in complex with HSA showed that there were two regions of the Adnectin in contact. Select residues from the FG loop form weak interactions with HSA, while the major contact residues are found in the CD loop (located on the “south pole”). Using the CalculateInteractionEnergy protocol from DISCOVERY STUDIO (Dassault Systèmes BIOVIA, Discovery Studio Modeling Environment, San Diego), the interaction energies were calculated for Adnectin bound to HSA. All of the residues that are predicted to contribute the most to binding HSA are located in the CD loop. A table showing the explicit residues interactions was generated using the Protein Interaction Analysis protocol from BIOLUMINATE. By combining the interaction energies with the type and quantity of interaction, the residues in the CD and FG loops of the Adnectin were ranked for mutational studies. 
     Based upon the results of the binding site analysis, positions were selected for mutagenesis. These amino acids were selected to be small and polar and would be predicted to decrease surface contact with amino acids in HSA when used in the mutational study. Computational mutation studies were performed in which each of the positions was substituted and interaction energies calculated for Adnectin bound to HSA. Specific positions were identified where the calculated interactions would predict a decrease in Adnectin-HSA affinity. Mutants were also designed so as not to increase the predicted risk for T-cell epitopes. Mutants were selected on the basis that they did not increase the predicted risk of T-cell epitopes and had the lowest possible immunogenicity scores (iDAB scores). 
     The iDAB immunogenicity score is based upon IEDB (as described in Vita et al.,  Nucleic Acids Res  2015;43(Database issue):D405-12), and is proportional to the fraction of 15-mers in the protein sequence that are predicted to show high binding affinity to at least 4 of the 8 commonly found alleles in the world population. The score is obtained through a linear regression fit of the fraction of strong-binding 15-mers to experimental binding affinities. For the positions identified in the binding site analysis, single mutants that were predicted to have low immunogenicity scores were identified and combined into double mutants. 
     The resulting single and double mutants are summarized in Tables 1-3 (the substitutions listed are in relation to positions in the core 7016_A01 sequence set forth in SEQ ID NO: 23). 
     
       
         
          TABLE 1
           
               
               
               
               
               
               
             
               
                 Adnectin ID 
                 Position in core 7016_A01 sequence (SEQ ID NO: 23) 
                 Residue in 7016_A01 
                 Residue in variant 
                 Loop with substitution 
                 iDAB immunogenicity score 
               
             
            
               
                 Wt  10 Fn3 
                   
                   
                   
                   
                 -37.8 
               
               
                 SGE 
                   
                   
                   
                   
                 -37.8 
               
               
                 ADX_7016_A 01 
                   
                   
                   
                   
                 -0.3 
               
               
                 1 
                 44 
                 Y 
                 Q 
                 CD 
                 -23.2 
               
               
                 2 
                 44 
                 Y 
                 E 
                 CD 
                 -30.8 
               
               
                 3 
                 44 
                 Y 
                 S 
                 CD 
                 -23.2 
               
               
                 4 
                 44 
                 Y 
                 A 
                 CD 
                 -27.0 
               
               
                 5 
                 41 
                 L 
                 D 
                 CD 
                 -11.7 
               
               
                 6 
                 41 
                 L 
                 S 
                 CD 
                 -11.7 
               
               
                 7 
                 41 
                 L 
                 A 
                 CD 
                 -11.7 
               
               
                 8 
                 38 
                 L 
                 S 
                 CD 
                 -0.3 
               
               
                 9 
                 38 
                 L 
                 T 
                 CD 
                 -0.3 
               
               
                 10 
                 38 
                 L 
                 A 
                 CD 
                 -0.3 
               
               
                 11 
                 33 
                 Q 
                 D 
                 CD 
                 -0.3 
               
               
                 12 
                 30 
                 R 
                 D 
                 CD 
                 -23.2 
               
               
                 13 
                 30 
                 R 
                 E 
                 CD 
                 -11.7 
               
               
                 14 
                 30 
                 R 
                 A 
                 CD 
                 -0.3 
               
               
                 15 
                 30 
                 R 
                 Q 
                 CD 
                 -11.7 
               
               
                 16 
                 30 
                 R 
                 N 
                 CD 
                 -4.1 
               
               
                 17 
                 42 
                 Y 
                 A 
                 CD 
                 -0.3 
               
               
                 18 
                 42 
                 Y 
                 T 
                 CD 
                 -0.3 
               
               
                 19 
                 43 
                 I 
                 D 
                 CD 
                 -15.5 
               
               
                 20 
                 43 
                 I 
                 S 
                 CD 
                 -7.9 
               
               
                 21 
                 43 
                 I 
                 A 
                 CD 
                 -7.9 
               
               
                 22 
                 35 
                 Y 
                 S 
                 CD 
                 -0.3 
               
               
                 23 
                 35 
                 Y 
                 A 
                 CD 
                 -0.3 
               
               
                 24 
                 85 
                 K 
                 A 
                 FG 
                 -0.3 
               
               
                 25 
                 85 
                 K 
                 T 
                 FG 
                 -0.3 
               
               
                 26 
                 85 
                 K 
                 S 
                 FG 
                 -0.3 
               
            
           
         
       
     
     Double amino acid substitutions in the CD loop (i.e., CD/CD mutations), relative to the CD loop of ADX_7016_A01, were made as shown in Table 2. 
     
       
         
          TABLE 2
           
               
               
               
               
               
               
               
               
             
               
                 Substitution Position 
                 Y44E 
                 Y44A 
                 Y44S 
                 Y44Q 
                 L41A 
                 L41S 
                 L41D 
               
             
            
               
                 L41A 
                 L41A/Y44E 
                 L41A/Y44A 
                 L41A/Y44S 
                 L41A/Y44Q 
                   
               
               
                 L41S 
                 L41S/Y44E 
                 L41S/Y44A 
                 L41S/Y44S 
                 L41S/Y44Q 
               
               
                 L41D 
                 L41D/Y44E 
                 L41D/Y44A 
                 L41D/Y44S 
                 L41D/Y44Q 
               
               
                 l43A 
                 l43A/Y44E 
                 l43A/Y44A 
                 l43A/Y44S 
                 l43A/Y44Q 
                 l43A/L41A 
                 l43A/L41S 
                 l43A/L41D 
               
               
                 I43S 
                 I43S/Y44E 
                 143S /Y44A 
                 I43S/Y44S 
                 I43S/Y44Q 
                 I43S/L41A 
                 I43S/L41S 
                 I43S/L41D 
               
               
                 L38A 
                 L38A/Y44E 
                 L38A/Y44A 
                 L38A/Y44S 
                 L38A/Y44Q 
                 L38A/L41A 
                 L38A/L41S 
                 L38A/L41D 
               
               
                 L38S 
                 L38S/Y44E 
                 L38S/Y44A 
                 L38S/Y44S 
                 L38S/Y44Q 
                 L38S/L41A 
                 L38S/L41S 
                 L38S/L41D 
               
               
                 L38T 
                 L38T/Y44E 
                 L38T/Y44A 
                 L38T/Y44S 
                 L38T/Y44Q 
                 L38T/L41A 
                 L38T/L41S 
                 L38T/L41D 
               
               
                 Q33D 
                 Q33D/Y44E 
                 Q33D/Y44A 
                 Q33D/Y44S 
                 Q33D/Y44Q 
                   
               
               
                 R30E 
                 R30E/Y44E 
                 R30E/Y44A 
                 R30E/Y44S 
                 R30E/Y44Q 
                 R30E/L41A 
                 R30E/L41S 
                 R30E/L41D 
               
               
                 R30D 
                 R30D/Y44E 
                 R30D/Y44A 
                 R30D/Y44S 
                 R30D/Y44Q 
                 R30D/L41A 
                 R30D/L41S 
                 R30D/L41D 
               
               
                 R30A 
                   
                   
               
               
                 R30Q 
                 R30Q/L41A 
                 R30Q/L41S 
                 R30Q/L41D 
               
               
                 R30N 
                 R30N/L41A 
                 R30N/L41S 
                 R30N/L41D 
               
               
                 Y35A 
                 Y35A/Y44E 
                 Y35A/Y44A 
                 Y35A/Y44S 
                 Y35A/Y44Q 
                 Y35A/L41A 
                 Y35A/L41S 
                 Y35A/L41D 
               
               
                 Y35S 
                 Y35S/Y44E 
                 Y35S/Y44A 
                 Y35S/Y44S 
                 Y35S/Y44Q 
                 Y35S/L41A 
                 Y35S/L41S 
                 Y35S/L41D 
               
            
           
         
       
     
     Double amino acid substitutions in the CD and FG loops (CD/FG mutations), relative to the CD and FG loops of ADX_7016_A01, were made as shown in Table 3. 
     
       
         
          TABLE 3
           
               
               
               
               
             
               
                 Substitution Position 
                 K85A 
                 K85T 
                 K85S 
               
             
            
               
                 Y44Q 
                 Y44Q/K85A 
                 Y44Q/K85T 
                 Y44Q/K85S 
               
               
                 Y44E 
                 Y44E/K85A 
                 Y44E/K85T 
                 Y44E/K85S 
               
               
                 Y44S 
                 Y44S/K85A 
                 Y44S/K85T 
                 Y44S/K85S 
               
               
                 Y44A 
                 Y44A/K85A 
                 Y44A/K85T 
                 Y44A/K85S 
               
               
                 L41D 
                 L41D/K85A 
                 L41D/K85T 
                 L41D/K85S 
               
               
                 L41S 
                 L41S/K85A 
                 L41S/K85T 
                 L41S/K85S 
               
               
                 L41A 
                 L41A/K85A 
                 L41A/K85T 
                 L41A/K85S 
               
               
                 L38S 
                 L38S/K85A 
                 L38S/K85T 
                 L38S/K85S 
               
               
                 L38T 
                 L38T/K85A 
                 L38T/K85T 
                 L38T/K85S 
               
               
                 L38A 
                 L38A/K85A 
                 L38A/K85T 
                 L38A/K85S 
               
               
                 Q33D 
                 Q33D/K85A 
                 Q33D/K85T 
                 Q33D/K85S 
               
               
                 R30D 
                 R30D/K85A 
                 R30D/K85T 
                 R30D/K85S 
               
               
                 R30E 
                 R30E/K85A 
                 R30E/K85T 
                 R30E/K85S 
               
               
                 R30A 
                 R30A/K85A 
                 R30A/K85T 
                 R30A/K85S 
               
               
                 R30Q 
                 R30Q/K85A 
                 R30Q/K85T 
                 R30Q/K85S 
               
               
                 R30N 
                 R30N/K85A 
                 R30N/K85T 
                 R30N/K85S 
               
               
                 Y42A 
                 Y42A/K85A 
                 Y42A/K85T 
                 Y42A/K85S 
               
               
                 Y42T 
                 Y42T/K85A 
                 Y42T/K85T 
                 Y42T/K85S 
               
               
                 I43D 
                 I43D/K85A 
                 I43D/K85T 
                 I43D/K85S 
               
               
                 I43A 
                 I43A/K85A 
                 I43A/K85T 
                 I43A/K85S 
               
               
                 Y35S 
                 Y35S/K85A 
                 Y35S/K85T 
                 Y35S/K85S 
               
               
                 Y35A 
                 Y35A/K85A 
                 Y35A/K85T 
                 Y35A/K85S 
               
            
           
         
       
     
     The mutants exhibited favorable biophysical properties, with only two mutants having an SEC of 2. The remaining mutants had an SEC of 1. All mutants were also highly expressed, at ≥1 mg/mL. 
     Example 2: Screening for Fast Off-Rate Human Serum Albumin Binding Adnectins 
     The mutant HSA binding Adnectins were screened for binding affinity to HSA in order to identify Adnectins that had a higher off-rate than the wild type parent Adnectin (i.e., ADX_7016_A01). 
     Screening of the mutant Adnectins generated in Example 1 identified four classes of Adnectins: those that bound with similar affinity as the parent Adnectin, those that had high binding affinity (reaches 100% binding), those with medium binding affinity (&lt;100% binding relative to parent Adnectin), and those with low binding affinity (&lt;50% binding relative to parent Adnectin). 
     Measurements were conducted by SPR and ELISA. SPR was conducted as follows. Full length HSA or mouse albumin was immobilized on a Biacore T series CM5 chip at 15 ug/mL in 10 mM acetate buffer (pH 5.0) buffer using standard NHS/EDC coupling, to a surface density of approximately 1000-1100 RU. For off-rate measurements at 25° C., PKE Adnectins were applied as analytes at 500nM in HBS-P+ (0.01 M HEPES pH 7.4, 0.15 M NaCl, 0.005% v/v Surfactant P20) running buffer at a flow rate of 20 ul/min for 120 s over the immobilized albumins, followed by 800 s for dissociation. For kinetic affinity measurements carried out at 37° C., a concentration series of the PKE Adnectins (0.05 - 333 nM) was applied in HBS-P+ running buffer at a flow rate of 40 ul/min for 180 s followed by dissociation for 240 s or 600 s. Regeneration of the chip surface between cycles was accomplished with two 30 second pulses of 10 mM Glycine, pH 2.0. Kinetic traces of reference-subtracted sensorgrams were fit to a 1:1 binding model for affinity using the Biaevaluation software. Only the dissociation phase was fit for determinatio of off-rates. 
     Direct binding ELISA assays were conducted as follows. Full length human and murine serum albumin at 10 ug/ml in PBS were coated on Nunc Maxisorp plates overnight at 4° C. Plates were blocked in casein/PBS buffer. PKE Adnectins were allowed to bind over a 4-point concentration range of 0.032 - 4 uM for HSA and 0.008 - 1 uM for MSA. Bound Adnectin was detected by anti-His antibody conjugated with HRP (horseradish peroxidase) diluted 1:1500 in casein/PBS. Plates were developed with TMB substrate and absorbance read at 450 nm. Adnectins were binned as high, medium and low affinity binders based on the observed Ymax of the concentration response curves. 
     The results for a subset of the variant Adnectins, including SPR analysis and ELISA data for both binding to HSA and mouse serum albumin (MSA) are provided in Table 4. 
     
       
         
          TABLE 4
           
               
               
               
               
               
               
               
               
               
             
               
                 DB ELISA Bins 
                 HSA DB ELISA (OD450) 
                 HSA kd (s-1) 
                 HSA kd/ Parent kd 
                 MSA DB ELISA (OD450) 
                 MSA kd (s-1) 
                 MSA kd/ Parent kd 
               
               
                 BEST (Close to Parent) 
                 Ymin obs 
                 Ymax obs 
                   
                   
                 Ymin obs 
                 Ymax obs 
                   
                   
               
             
            
               
                 ADX_6727_C01 (K85A) 
                 88 
                 98 
                 2.97E-04 
                 1.1 
                 90 
                 93 
                 5.09E-04 
                 1.2 
               
               
                 ADX_6727_D01 (K85T) 
                 88 
                 97 
                 2.59E-04 
                 1.0 
                 88 
                 91 
                 4.33E-04 
                 1.0 
               
               
                 ADX_6727_B01 (K85S) 
                 94 
                 97 
                 3.21E-04 
                 1.2 
                 88 
                 91 
                 5.01E-04 
                 1.2 
               
               
                 ADX_6727_B04 (Y35S/K85S) 
                 62 
                 99 
                 1.10E-03 
                 4.1 
                 74 
                 95 
                 1.42E-03 
                 3.3 
               
               
                 ADX_6727_G10 (Y35S/K85A) 
                 54 
                 96 
                 8.92E-04 
                 3.3 
                 54 
                 100 
                 1.38E-03 
                 3.2 
               
            
           
           
               
               
               
               
               
               
               
               
               
             
               
                 HIGH (Reaches 100% binding) 
                   
                   
                   
                   
                   
                   
                   
                   
               
             
            
               
                 ADX_6727_C07 
                 44 
                 100 
                 2.18E-03 
                 8 
                 6 
                 94 
                 3.34E-03 
                 7.8 
               
               
                 (R30A/K85S) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 ADX_6727_C03 (Y35S) 
                 31 
                 99 
                 1.07E-03 
                 4 
                 23 
                 95 
                 1.21E-03 
                 2.8 
               
               
                 ADX_6727_D02 (R30N) 
                 20 
                 99 
                 1.35E-03 
                 5 
                 17 
                 93 
                 1.18E-03 
                 2.8 
               
               
                 ADX_6727_F06 (L41A/K85T) 
                 19 
                 90 
                 2.98E-03 
                 11 
                 4 
                 91 
                 5.50E-03 
                 12.8 
               
               
                 ADX_6734_A02 (I43A/Y44E) 
                 4 
                 100 
                 NB 
                 NB 
                 3 
                 100 
                 NB 
                 NB 
               
               
                 MEDIUM (&lt;100% binding) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 ADX_6727_G01 (L41A) 
                 12 
                 79 
                 3.70E-03 
                 14 
                 3 
                 87 
                 6.39E-03 
                 14.9 
               
               
                 ADX_6727_F03 (I43Y) 
                 9 
                 89 
                 4.68E-03 
                 17 
                 2 
                 67 
                 3.80E-03 
                 8.9 
               
               
                 ADX_6727_D06 (Y44A/K85S) 
                 8 
                 67 
                 5.46E-03 
                 20 
                 1 
                 85 
                 6.22E-03 
                 14.5 
               
               
                 ADX_6727_F04 (Y44A/K85A) 
                 6 
                 56 
                 6.24E-03 
                 23 
                 2 
                 77 
                 6.94E-03 
                 16.2 
               
               
                 ADX_6727_B05 (I43S/K85T) 
                 4 
                 60 
                 7.49E-03 
                 28 
                 2 
                 63 
                 7.81E-03 
                 18.2 
               
               
                 LOW (&lt;50% binding) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 ADX_6727_B11 (Q33D/K85S) 
                 1 
                 12 
                 1.51E-02 
                 56 
                 1 
                 11 
                 NB 
                 NB 
               
               
                 ADX_6727_D10 (Q33D/K85T) 
                 2 
                 19 
                 1.34E-02 
                 50 
                 1 
                 42 
                 6.08E-02 
                 142.1 
               
               
                 ADX_6727_B09 (L38T/K85T) 
                 2 
                 16 
                 9.21E-03 
                 34 
                 1 
                 27 
                 2.62E-02 
                 61.2 
               
               
                 ADX_6727_H02 (I43S) 
                 2 
                 37 
                 1.39E-02 
                 52 
                 1 
                 39 
                 9.77E-03 
                 22.8 
               
               
                 ADX_6727_G05 (I43S/K85A) 
                 2 
                 38 
                 1.43E-02 
                 53 
                 1 
                 32 
                 1.16E-02 
                 27.0 
               
               
                 *Note: Off-rates for HTTP proteins measured at 25° C. The numbering of the amino acid substitutions listed in parentheses under the name of the Adnectins is based on the core amino acid sequence of ADX_7016_A01 (SEQ ID NO: 23). 
               
            
           
         
       
     
     As shown in  FIGS.  1  and  2   , HSA off-rate sensograms (obtained by SPR analysis) correlated with DB ELISA binning. 
     An additional 15 variant HSA binding Adnectins were selected for further analysis. A summary of SPR and ELISA data for these variants, including both HSA and MSA binding data, are provided in Table 5, and off-rate sensograms for these variants are provided in  FIG.  3   . 
     
       
         
          TABLE 5
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
                   
                 HSA DB ELISA 
                   
                 MSA DB ELISA 
               
               
                 ADX ID 
                 HSA kd (s-1) 
                 HSA kd/ Parent kd 
                 HSA Binding (RU) 
                 YMIN OBS (OD450) 
                 YMAX OBS (OD450) 
                 MSA kd (s-1) 
                 MSA kd/ Parent kd 
                 MSA Binding (RU) 
                 YMIN OBS (OD450) 
                 YMAX OBS (OD450) 
               
             
            
               
                 7016_A01 (parent) 
                 2.69E-04 
                   
                 54 
                 90 
                 94 
                 4.28E-04 
                   
                 95 
                 95 
                 98 
               
               
                 6727_G10 (Y35S/K85A) 
                 8.92E-04 
                 3.3 
                 27 
                 54 
                 96 
                 1.38E-03 
                 3.2 
                 63 
                 54 
                 100 
               
               
                 6727_G06 (Y35A/K85S) 
                 1.05E-03 
                 3.9 
                 26 
                 69 
                 98 
                 1.43E-03 
                 3.3 
                 66 
                 40 
                 95 
               
               
                 6727_F10 (Y35A/K85T) 
                 1.09E-03 
                 4.0 
                 22 
                 61 
                 98 
                 1.56E-03 
                 3.6 
                 55 
                 39 
                 98 
               
               
                 6727_B04 (Y35S/K85S) 
                 1.10E-03 
                 4.1 
                 23 
                 62 
                 99 
                 1.42E-03 
                 3.3 
                 62 
                 74 
                 95 
               
               
                 6727_A07 (Y44S/K85T) 
                 1.29E-03 
                 4.8 
                 28 
                 60 
                 98 
                 2.22E-03 
                 5.2 
                 56 
                 31 
                 94 
               
               
                 6727_G02 (Y44S) 
                 1.50E-03 
                 5.6 
                 33 
                 38 
                 95 
                 2.13E-03 
                 5.0 
                 64 
                 15 
                 91 
               
               
                 6727_F07 (Y44S/K85A) 
                 1.76E-03 
                 6.5 
                 35 
                 44 
                 96 
                 2.77E-03 
                 6.5 
                 62 
                 20 
                 96 
               
               
                 6727_G04 (Y44S/K85S) 
                 1.77E-03 
                 6.6 
                 28 
                 75 
                 99 
                 2.59E-03 
                 6.0 
                 56 
                 46 
                 94 
               
               
                 6727_D03 (L41S) 
                 7.77E-03 
                 28.9 
                 24 
                 3 
                 33 
                 1.34E-02 
                 31.3 
                 43 
                 1 
                 54 
               
               
                 6727_E08 (L38T) 
                 8.15E-03 
                 30.3 
                 25 
                 2 
                 12 
                 2.48E-02 
                 57.8 
                 30 
                 1 
                 12 
               
               
                 6727 H10 (L41S/K85S) 
                 8.60E-03 
                 32.0 
                 19 
                 5 
                 39 
                 1.46E-02 
                 34.0 
                 35 
                 1 
                 59 
               
               
                 6727_B09 (L38T/K85T) 
                 9.21E-03 
                 34.3 
                 19 
                 2 
                 16 
                 2.62E-02 
                 61.2 
                 26 
                 1 
                 27 
               
               
                 6727_H08 (L38T/K85T) 
                 1.00E-02 
                 37.3 
                 18 
                 2 
                 17 
                 2.84E-02 
                 66.3 
                 23 
                 1 
                 21 
               
               
                 6727_H06 (Y44Q/K85T) 
                 1.42E-02 
                 52.7 
                 24 
                 1 
                 12 
                 1.43E-02 
                 33.5 
                 43 
                 1 
                 33 
               
               
                 6727_B03 (Y44Q) 
                 2.14E-02 
                 79.4 
                 14 
                 2 
                 18 
                 1.79E-02 
                 41.9 
                 33 
                 1 
                 23 
               
               
                 *Note: Off-rates for HTTP proteins measured at 25° C. The numbering of the amino acid substitutions listed in parentheses under the name of the Adnectins is based on the core amino acid sequence of ADX_7016_A01 (SEQ ID NO: 23). 
               
            
           
         
       
     
     Collectively, the data show that the 4pt DB HSA/MSA ELISA data correlated well with the off-rate screen, i.e., HSA binding Adnectins with slower off-rates were better binders in ELISA (with a few exceptions). 
     Example 3: Binding Affinity of Fast Off-Rate PKE3 Variants for Serum Albumins 
     Three variant HSA binding Adnectins were tested for binding affinity to HSA, MSA, rat serum albumin (rat SA), and cynomolgus monkey serum albumin (cynoSA) using SPR analysis. 
     The SPR was conducted as follows. Full length human, mouse, rat and cynomolgus monkey serum albumin were immobilized on a Biacore T series CM5 chip at 15 ug/mL in 10 mM acetate buffer (pH 5.0) buffer using standard NHS/EDC coupling, to a surface density of approximately 1000-1100 RU. For off-rate measurements at 25° C., PKE Adnectins were applied as analytes at 500 nM in HBS-P+ (0.01 M HEPES pH 7.4, 0.15 M NaCl, 0.005% v/v Surfactant P20) running buffer at a flow rate of 20 ul/min for 120 s over the immobilized albumins, followed by 800 s for dissociation. For kinetic affinity measurements carried out at 37° C., a concentration series of the PKE Adnectins (0.05 - 333 nM) was applied in HBS-P+ running buffer at a flow rate of 40 ul/min for 180 s followed by dissociation for 240 s or 600 s. Regeneration of the chip surface between cycles was accomplished with two 30 second pulses of 10 mM Glycine, pH 2.0. Kinetic traces of reference-subtracted sensorgrams were fit to a 1:1 binding model for affinity using the Biaevaluation software. Only the dissociation phase was fit for determinatio of off-rates. 
     The results are summarized in Table 6, and the sensograms are provided in  FIGS.  4 A- 4 D . 
     
       
         
          TABLE 6
           
               
               
               
               
               
               
             
               
                 Adnectin ID 
                 Ligand 
                 ka (1/Ms) 
                 kd (1/s) 
                 KD (nM) 
                 Rmax (RU) 
               
             
            
               
                 ADX_7016_A01 (PKE2) 
                 HSA 
                 6.12E+04 
                 3.78E-04 
                 6.2 
                 140 
               
               
                 cynoSA 
                 8.94E+04 
                 3.91E-04 
                 4.4 
                 140 
               
               
                 MSA 
                 2.37E+05 
                 6.68E-04 
                 2.8 
                 115 
               
               
                 Rat SA 
                 1.80E+05 
                 1.43E-03 
                 8.0 
                 120 
               
               
                 ADX_7016_G01 (Y44S) 
                 HSA 
                 3.82E+04 
                 3.20E-03 
                 83.7 
                 110 
               
               
                 cynoSA 
                 6.25E+04 
                 4.26E-03 
                 68.1 
                 125 
               
               
                 MSA 
                 2.35E+05 
                 6.29E-03 
                 26.8 
                 100 
               
               
                 Rat SA 
                 3.31E+05 
                 3.46E-02 
                 104 
                 40 
               
               
                 ADX_7016_E02 (L38T) 
                 HSA 
                 2.42E+04 
                 1.61E-02 
                 666 
                 50 
               
               
                 cynoSA 
                 1.19E+05 
                 1.71E-01 
                 1430 
                 45 
               
               
                 MSA 
                 6.84E+04 
                 3.43E-02 
                 502 
                 75 
               
               
                 Rat SA 
                 4.94E+04 
                 5.58E-02 
                 1130 
                 45 
               
               
                 ADX_7016_C03 (Y44Q) 
                 HSA 
                 3.21E+04 
                 2.85E-02 
                 889 
                 50 
               
               
                 cynoSA 
                 4.12E+04 
                 4.44E-02 
                 1080 
                 60 
               
               
                 MSA 
                 1.15E+05 
                 3.05E-02 
                 265 
                 90 
               
               
                 Rat SA 
                 8.91E+04 
                 1.19E-01 
                 1340 
                 35 
               
               
                 Note: The cynoSA experiment was performed using a different Biacore chip 
               
            
           
         
       
     
     Example 4: Fast Off-Rate PKE3 Adnectins Exhibit Faster Clearance Than Wild-type Parent PKE2 Adnectin 
     The clearance of the three PKE3 Adnectins from Example 3 were tested in vivo in Sprague Dawley rats (n=2/group). Rats were administered a single IV dose of each PKE3 Adnectin (2 mg/kg), and plasma was collected at the following time points: 5 min, 1 hr, 2 hrs, 4 hrs, 8 hrs, 1 day, 2 days, 3 days, 5 days, and 7 days. 
     As shown in  FIG.  5   , the parent PKE2 Adnectin (ADX_7016_A01) exhibited the longest half-life, whereas the three PKE3 Adnectins had shorter half-lives. Similar results were observed in mice ( FIG.  6   ). 
     
       
         
          TABLE 7
           
               
               
               
             
               
                 SUMMARY OF SEQUENCES 
               
               
                 SEQ ID 
                 Description 
                 Sequence 
               
             
            
               
                 1 
                 Wild-type human  10 Fn3 domain 
                 VSDVPRDLEVVAA TPTS LLISWDAPAVTVRYYRITY GETGGNSPVQE F TVPGSKSTATISGL KPGVD YTITVYAVTGRGDSPASSKPISINYRT 
               
               
                 2 
                 Wild-type human  10 Fn3 domain w/loop sequences generically defined 
                 VSDVPRDLEVVAA (X)  u LLISW (X)  V YRITY (X)  W FTV (X)  X ATISGL (X)  y YTITVYA (X)  Z ISINYRT 
               
               
                 3 
                 N-terminal leader 
                 MGVSDVPRDL 
               
               
                 4 
                 N-terminal leader 
                 GVSDVPRDL 
               
               
                 5 
                 N-terminal leader 
                 X n SDVPRDL 
               
               
                 6 
                 N-terminal leader 
                 X n DVPRDL 
               
               
                 7 
                 N-terminal leader 
                 X n VPRDL 
               
               
                 8 
                 N-terminal leader 
                 X n PRDL 
               
               
                 9 
                 N-terminal leader 
                 X n RDL 
               
               
                 10 
                 N-terminal leader 
                 X n DL 
               
               
                 11 
                 N-terminal leader 
                 MASTSG 
               
               
                 12 
                 C-terminal tail 
                 EIEK 
               
               
                 13 
                 C-terminal tail 
                 EGSGC 
               
               
                 14 
                 C-terminal tail 
                 EIEKPCQ 
               
               
                 15 
                 C-terminal tail 
                 EIEKPSQ 
               
               
                 16 
                 C-terminal tail 
                 EIEKP 
               
               
                 17 
                 C-terminal tail 
                 EIEKPS 
               
               
                 18 
                 C-terminal tail 
                 EIEKPC 
               
               
                 19 
                 C-terminal tail 
                 EIDK 
               
               
                 20 
                 C-terminal tail 
                 EIDKPCQ 
               
               
                 21 
                 C-terminal tail 
                 EIDKPSQ 
               
               
                 22 
                 6X His tail 
                 HHHHHH 
               
               
                 23 
                 7016_A01 core (aka 2629_E06; parent PKE2 Adnectin); CD and FG loops are underlined 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 24 
                 7016_A01 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 25 
                 7016_A01 w/o his tag, C-terminal tail, and N-terminal MG 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGP   LYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRT 
               
               
                 26 
                 7016_A01 core with C-terminal proline 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRTP 
               
               
                 27 
                 7016_A01 w/o his tag, C-terminail tail, and N-terminal MG and w/ C-terminal proline 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGP   LYIYQEF TVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRTP 
               
               
                 28 
                 7016_A01 CD loop 
                 GREVQKYSDLGPLYIYQE 
               
               
                 29 
                 7016_A01 FG loop 
                 VTGSGESPASSKP 
               
               
                 30 
                 7016_G01 (Y44S) core (aka 6727_G02) 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYISQEF T VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 31 
                 7016_G01 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYISQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 32 
                 7016_G01 w/o his tag, C-terminal tail, and N-terminal MG 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGP   LYISQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRT 
               
               
                 33 
                 7016_G01 core with C-terminal proline 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYISQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRTP 
               
               
                 34 
                 7016_G01 w/o his tag, C-terminail tail, and N-terminal MG and w/ C-terminal proline 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGP   LYISQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRTP 
               
               
                 35 
                 7016_G01 CD loop 
                 GREVQKYSDLGPLYISQE 
               
               
                 36 
                 7016_E02 (L38T) core (aka 6727_E08) 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDTGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 37 
                 7016_E02 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDT   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 38 
                 7016_E02 w/o his tag, C-terminal tail, and N-terminal MG 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDTGP   LYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRT 
               
               
                 39 
                 7016_E02 core with C-terminal proline 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDTGPLYIYQE FT VPGSKSTATISGLKPGVDYTIT VYAVTGSGESPASSKP ISINYRTP 
               
               
                 40 
                 7016_E02 w/o his tag, C-terminail tail, and N-terminal MG and w/ C-terminal proline 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDTGP   LYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRTP 
               
               
                 41 
                 7016_E02 CD loop 
                 GREVQKYSDTGPLYIYQE 
               
               
                 42 
                 7016_C03 (Y44Q) core (aka 6727_B03) 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIQQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 43 
                 7016_C03 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIQQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 44 
                 7016_C03 w/o his tag, C-terminal tail, and N-terminal MG 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGP   LYIQQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRT 
               
               
                 45 
                 7016_C03 core with C-terminal proline 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIQQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRTP 
               
               
                 46 
                 7016_C03 w/o his tag, C-terminail tail, and N-terminal MG and w/ C-terminal proline 
                 VSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGP   LYIQQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP IS INYRTP 
               
               
                 47 
                 7016_C03 CD loop 
                 GREVQKYSDLGPLYIQQE 
               
               
                 48 
                 ADX_6727_C01 (K85A) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP ISINYRT 
               
               
                 49 
                 ADX_6727_C01 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP  ISINYRTEIDKPSQHHHHHH 
               
               
                 50 
                 ADX_6727_C01 FG loop 
                 VTGSGESPASSAP 
               
               
                 51 
                 ADX_6727_D01 (K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 52 
                 ADX_6727_D01 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 53 
                 ADX_6727_D01 FG loop 
                 VTGSGESPASSTP 
               
               
                 54 
                 ADX_6727_B01 (K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 55 
                 ADX_6727_B01 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 56 
                 ADX_6727_B01 FG loop 
                 VTGSGESPASSSP 
               
               
                 57 
                 ADX_6727_B04 (Y35S/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKSSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 58 
                 ADX_6727_B04 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKSSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 59 
                 ADX_6727_B04 CD loop 
                 GREVQKSSDLGPLYIYQE 
               
               
                 56 
                 ADX_6727_B04 FG loop 
                 VTGSGESPASSSP 
               
               
                 60 
                 ADX_6727_G10 (Y35S/K85A) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKSSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP ISINYRT 
               
               
                 61 
                 ADX_6727_G10 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKSSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP  ISINYRTEIDKPSQHHHHHH 
               
               
                 59 
                 ADX_6727_G10 CD loop 
                 GREVQKSSDLGPLYIYQE 
               
               
                 50 
                 ADX_6727_G10 FG loop 
                 VTGSGESPASSAP 
               
               
                 62 
                 ADX_6727_C07 (R30A/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GAEVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 63 
                 ADX_6727_C07 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GAEVQKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 64 
                 ADX_6727_C07 CD loop 
                 GAEVQKYSDLGPLYIYQE 
               
               
                 56 
                 ADX_6727_C07 FG loop 
                 VTGSGESPASSSP 
               
               
                 65 
                 ADX_6727_C03 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKSSDLGPLYIYQE FT 
               
               
                   
                 (Y35S) core 
                 VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 66 
                 ADX_6727_C03 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKSSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 59 
                 ADX_6727_C03 CD loop 
                 GREVQKSSDLGPLYIYQE 
               
               
                 67 
                 ADX_6727_D02 (R30N) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GNEVQKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 68 
                 ADX_6727_D02 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GNEVQKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 69 
                 ADX_6727_D02 CD loop 
                 GNEVQKYSDLGPLYIYQE 
               
               
                 70 
                 ADX_6727_F06 (L41A/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPAYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 71 
                 ADX_6727_F06 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPAYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 72 
                 ADX_6727_F06 CD loop 
                 GREVQKYSDLGPAYIYQE 
               
               
                 53 
                 ADX_6727_F06 FG loop 
                 VTGSGESPASSTP 
               
               
                 73 
                 ADX_6727_G01 (L41A) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPAYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 74 
                 ADX_6727_G01 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPAYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 72 
                 ADX_6727_G01 CD loop 
                 GREVQKYSDLGPAYIYQE 
               
               
                 75 
                 ADX_6727_F03 (I43A) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYAYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 76 
                 ADX_6727_F03 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYAYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 77 
                 ADX_6727_F03 CD loop 
                 GREVQKYSDLGPLYAYQE 
               
               
                 78 
                 ADX_6727_D06 (Y44A/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIAQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 79 
                 ADX_6727_D06 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIAQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 80 
                 ADX_6727_D06 CD loop 
                 GREVQKYSDLGPLYIAQE 
               
               
                 56 
                 ADX_6727_D06 FG loop 
                 VTGSGESPASSSP 
               
               
                 81 
                 ADX_6727_F04 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIAQE FT 
               
               
                   
                 (Y44A/K85A) core 
                 VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP ISINYRT 
               
               
                 82 
                 ADX_6727_F04 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIAQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP  ISINYRTEIDKPSQHHHHHH 
               
               
                 80 
                 ADX_6727_F04 CD loop 
                 GREVQKYSDLGPLYIAQE 
               
               
                 50 
                 ADX_6727_F04 FG loop 
                 VTGSGESPASSAP 
               
               
                 83 
                 ADX_6727_B05 (I43S/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYSYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 84 
                 ADX_6727_B05 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYSYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 85 
                 ADX_6727_B05 CD loop 
                 GREVQKYSDLGPLYSYQE 
               
               
                 53 
                 ADX_6727_B05 FG loop 
                 VTGSGESPASSTP 
               
               
                 86 
                 ADX_6727_B11 (Q33D/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVDKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 87 
                 ADX_6727_B11 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVDKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 88 
                 ADX_6727_B11 CD loop 
                 GREVDKYSDLGPLYIYQE 
               
               
                 56 
                 ADX_6727_B11 FG loop 
                 VTGSGESPASSSP 
               
               
                 89 
                 ADX_6727_D10 (Q33D/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVDKYSDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 90 
                 ADX_6727_D10 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVDKYSDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 88 
                 ADX_6727_D10 CD loop 
                 GREVDKYSDLGPLYIYQE 
               
               
                 53 
                 ADX_6727_D10 FG loop 
                 VTGSGESPASSTP 
               
               
                 91 
                 ADX_6727_B09 (L38T/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDTGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 92 
                 ADX_6727_B09 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDT   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 41 
                 ADX_6727_B09 CD loop 
                 GREVQKYSDTGPLYIYQE 
               
               
                 53 
                 ADX_6727_B09 FG loop 
                 VTGSGESPASSTP 
               
               
                 93 
                 ADX_6727_H02 (I43S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYSYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 94 
                 ADX_6727_H02 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYSYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 85 
                 ADX_6727_H02 CD loop 
                 GREVQKYSDLGPLYSYQE 
               
               
                 95 
                 ADX_6727_G05 (I43S/K85A) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYSYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP ISINYRT 
               
               
                 96 
                 ADX_6727_G05 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYSYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP  ISINYRTEIDKPSQHHHHHH 
               
               
                 85 
                 ADX_6727_G05 CD loop 
                 GREVQKYSDLGPLYSYQE 
               
               
                 50 
                 ADX_6727_G05 FG loop 
                 VTGSGESPASSAP 
               
               
                 97 
                 ADX_6727_G06 (Y35A/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKASDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 98 
                 ADX_6727_G06 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKASDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 99 
                 ADX_6727_G06 CD loop 
                 GREVQKASDLGPLYIYQE 
               
               
                 56 
                 ADX_6727_G06 FG loop 
                 VTGSGESPASSSP 
               
               
                 100 
                 ADX_6727_F10 (Y35A/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKASDLGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 101 
                 ADX_6727_F10 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKASDL   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 99 
                 ADX_6727_F10 CD loop 
                 GREVQKASDLGPLYIYQE 
               
               
                 53 
                 ADX_6727_F10 FG loop 
                 VTGSGESPASSTP 
               
               
                 102 
                 ADX_6727_A07 (Y44S/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYISQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 103 
                 ADX_6727_A07 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYISQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 35 
                 ADX_6727_A07 CD loop 
                 GREVQKYSDLGPLYISQE 
               
               
                 53 
                 ADX_6727_A07 FG loop 
                 VTGSGESPASSTP 
               
               
                 104 
                 ADX_6727_F07 (Y44S/K85A) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYISQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP ISINYRT 
               
               
                 105 
                 ADX_6727_F07 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYISQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSAP  ISINYRTEIDKPSQHHHHHH 
               
               
                 35 
                 ADX_6727_F07 CD loop 
                 GREVQKYSDLGPLYISQE 
               
               
                 50 
                 ADX_6727_F07 FG loop 
                 VTGSGESPASSAP 
               
               
                 106 
                 ADX_6727_G04 (Y44S/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYISQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 107 
                 ADX_6727_G04 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYISQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 35 
                 ADX_6727_G04 CD loop 
                 GREVQKYSDLGPLYISQE 
               
               
                 56 
                 ADX_6727_G04 FG loop 
                 VTGSGESPASSSP 
               
               
                 108 
                 ADX_6727_D03 (L41S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPSYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 109 
                 ADX_6727_D03 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPSYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 110 
                 ADX_6727_D03 CD loop 
                 GREVQKYSDLGPSYIYQE 
               
               
                 111 
                 ADX_6727_H10 (L41S/K85S) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPSYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP ISINYRT 
               
               
                 112 
                 ADX_6727_H10 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPSYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSSP  ISINYRTEIDKPSQHHHHHH 
               
               
                 110 
                 ADX_6727_H10 CD loop 
                 GREVQKYSDLGPSYIYQE 
               
               
                 56 
                 ADX_6727_H10 FG loop 
                 VTGSGESPASSSP 
               
               
                 113 
                 ADX_6727_H08 (L38T/K85T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDTGPLYIYQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 114 
                 ADX_6727_H08 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDT   GPLYIYQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP  ISINYRTEIDKPSQHHHHHH 
               
               
                 41 
                 ADX_6727_H08 CD loop 
                 GREVQKYSDTGPLYIYQE 
               
               
                 53 
                 ADX_6727_H08 FG loop 
                 VTGSGESPASSTP 
               
               
                 115 
                 ADX_6727_H06 (Y44Q/K95T) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYIQQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP ISINYRT 
               
               
                 116 
                 ADX_6727_H06 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYIQQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSTP 
 
               
               
                   
                   
                 ISINYRTEIDKPSQHHHHHH 
               
               
                 47 
                 ADX_6727_H06 CD loop 
                 GREVQKYSDLGPLYIQQE 
               
               
                 53 
                 ADX_6727_H06 FG loop 
                 VTGSGESPASSTP 
               
               
                 117 
                 ADX_6734_A02 (I43A/Y44E) core 
                 EVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDLGPLYAEQE FT VPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP ISINYRT 
               
               
                 118 
                 ADX_6734_A02 
                 MGVSDVPRDLEVVAATPTSLLISWDAPAVTVRYYRITY GREVQKYSDL   GPLYAEQE FTVPGSKSTATISGLKPGVDYTITVYA VTGSGESPASSKP  ISINYRTEIDKPSQHHHHHH 
               
               
                 119 
                 ADX_6734_A02 CD loop 
                 GREVQKYSDLGPLYAEQE 
               
               
                 120 
                 Linker 
                 PSTPPTPSPSTPPTPSPS 
               
               
                 121 
                 Linker 
                 GSGSGSGSGSGSGS 
               
               
                 122 
                 Linker 
                 GGSGSGSGSGSGS 
               
               
                 123 
                 Linker 
                 GGSGSGSGSGSGSGSG 
               
               
                 124 
                 Linker 
                 GSEGSEGSEGSEGSE 
               
               
                 125 
                 Linker 
                 GGSEGGSE 
               
               
                 126 
                 Linker 
                 GSGSGSGS 
               
               
                 127 
                 Linker 
                 GGGGSGGGGSGGGGSGGGGSGGGGSGGGGSGGGGS 
               
               
                 128 
                 Linker 
                 GGGGSGGGGSGGGGSGGGGSGGGGS 
               
               
                 129 
                 Linker 
                 GGGGSGGGGSGGGGSG 
               
               
                 130 
                 Linker 
                 GPGPGPG 
               
               
                 131 
                 Linker 
                 GPGPGPGPGPG 
               
               
                 132 
                 Linker 
                 PAPAPA 
               
               
                 133 
                 Linker 
                 PAPAPAPAPAPA 
               
               
                 134 
                 Linker 
                 PAPAPAPAPAPAPAPAPA 
               
               
                 135 
                 Linker 
                 PSPEPPTPEP 
               
               
                 136 
                 Linker 
                 PSPEPPTPEPPSPEPPTPEP 
               
               
                 137 
                 Linker 
                 PSPEPPTPEPPSPEPPTPEPPSPEPPTPEP 
               
               
                 138 
                 Linker 
                 PSPEPPTPEPPSPEPPTPEPPSPEPPTPEPPSPEPPTPEP 
               
               
                 139 
                 Linker 
                 EEEEDE 
               
               
                 140 
                 Linker 
                 EEEEDEEEEDE 
               
               
                 141 
                 Linker 
                 EEEEDEEEEDEEEEDEEEEDE 
               
               
                 142 
                 Linker 
                 EEEEDEEEEDEEEEDEEEEDEEEEDEEEEDE 
               
               
                 143 
                 Linker 
                 RGGEEKKKEKEKEEQEERETKTP 
               
               
                 144 
                 Linker 
                 (PSPEPPTPEP)  n  n=1-10 
               
               
                 145 
                 Linker 
                 (EEEEDE)  n E n=1-10 
               
               
                 146 
                 Exemplary use of linker 
                 NYRTPGPSPEPPTPEP 
               
               
                 147 
                 Exemplary use of linker 
                 PSPEPPTPEPGVSDV 
               
               
                 148 
                 C-terminal tail 
                 EIEPKSS 
               
               
                 149 
                 C-terminal tail 
                 EIDKPC 
               
               
                 150 
                 C-terminal tail 
                 EIDKP 
               
               
                 151 
                 C-terminal tail 
                 EIDKPS 
               
               
                 152 
                 C-terminal tail 
                 EIDKPSQLE 
               
               
                 153 
                 C-terminal tail 
                 EIEDEDEDEDED 
               
               
                 154 
                 C-terminal tail 
                 EGSGS 
               
               
                 155 
                 C-terminal tail 
                 EIDKPCQLE 
               
               
                 156 
                 C-terminal tail 
                 EIDKPSQHHHHHH 
               
               
                 157 
                 C-terminal tail 
                 GSGCHHHHHH 
               
               
                 158 
                 C-terminal tail 
                 EGSGCHHHHHH 
               
               
                 159 
                 C-terminal tail 
                 PIDK 
               
               
                 160 
                 C-terminal tail 
                 PIEK 
               
               
                 161 
                 C-terminal tail 
                 PIDKP 
               
               
                 162 
                 C-terminal tail 
                 PIEKP 
               
               
                 163 
                 C-terminal tail 
                 PIDKPS 
               
               
                 164 
                 C-terminal tail 
                 PIEKPS 
               
               
                 165 
                 C-terminal tail 
                 PIDKPC 
               
               
                 166 
                 C-terminal tail 
                 PIEKPC 
               
               
                 167 
                 C-terminal tail 
                 PIDKPSQ 
               
               
                 168 
                 C-terminal tail 
                 PIEKPSQ 
               
               
                 169 
                 C-terminal tail 
                 PIDKPCQ 
               
               
                 170 
                 C-terminal tail 
                 PIEKPCQ 
               
               
                 171 
                 C-terminal tail 
                 PHHHHHH 
               
               
                 172 
                 C-terminal tail 
                 PCHHHHHH 
               
               
                 173 
                 7016_A01 (nucleic acid sequence) 
                 ATGGGAGTTTCTGATGTGCCGCGCGACCTGGAAGTGGTTGCTGCCACC CCCACCAGCCTGCTGATCAGCTGGGATGCACCTGCCGTCACAGTGCGA TATTACCGCATCACTTACGGCAGGGAGGTTCAGAAGTACTCGGACTTG GGTCCGTTGTACATCTACCAAGAGTTCACTGTGCCTGGGAGCAAGTCC ACAGCTACCATCAGCGGCCTTAAACCTGGCGTTGATTATACCATCACT GTGTATGCTGTCACTGGCTCTGGAGAGAGCCCCGCAAGCAGCAAGCCA ATTTCCATTAATTACCGCACAGAAATTGACAAACCATCCCAGCACCAT CACCACCACCACTGA 
               
            
           
         
       
     
     Equivalents 
     Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents of the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.