Patent Publication Number: US-2021186960-A1

Title: Modulators of indoleamine 2,3-dioxygenase

Description:
FIELD OF THE INVENTION 
     Compounds, methods and pharmaceutical compositions for the prevention and/or treatment of HIV; including the prevention of the progression of AIDS and general immunosuppression, by administering certain indoleamine 2,3-dioxygenase compounds in therapeutically effective amounts are disclosed. Methods for preparing such compounds and methods of using the compounds and pharmaceutical compositions thereof are also disclosed. 
     BACKGROUND OF THE INVENTION 
     Indoleamine-2,3-dioxygenase 1 (IDO1) is a heme-containing enzyme that catalyzes the oxidation of the indole ring of tryptophan to produce N-formyl kynurenine, which is rapidly and constitutively converted to kynurenine (Kyn) and a series of downstream metabolites. IDO1 is the rate limiting step of this kynurenine pathway of tryptophan metabolism and expression of IDO1 is inducible in the context of inflammation. Stimuli that induce IDO1 include viral or bacterial products, or inflammatory cytokines associated with infection, tumors, or sterile tissue damage. Kyn and several downstream metabolites are immunosuppressive: Kyn is antiproliferative and proapoptotic to T cells and NK cells (Munn, Shafizadeh et al. 1999, Frumento, Rotondo et al. 2002) while metabolites such as 3-hydroxy anthranilic acid (3-HAA) or the 3-HAA oxidative dimerization product cinnabarinic acid (CA) inhibit phagocyte function (Sekkai, Guittet et al. 1997), and induce the differentiation of immunosuppressive regulatory T cells (Treg) while inhibiting the differentiation of gut-protective IL-17 or IL-22 -producing CD4+ T cells (Th17 and Th22)(Favre, Mold et al. 2010). IDO1 induction, among other mechanisms, is likely important in limiting immunopathology during active immune responses, in promoting the resolution of immune responses, and in promoting fetal tolerance. However in chronic settings, such as cancer, or chronic viral or bacterial infection, IDO1 activity prevents clearance of tumor or pathogen and if activity is systemic, IDO1 activity may result in systemic immune dysfunction (Boasso and Shearer 2008, Li, Huang et al. 2012). In addition to these immunomodulatory effects, metabolites of IDO1 such as Kyn and quinolinic acid are also known to be neurotoxic and are observed to be elevated in several conditions of neurological dysfunction and depression. As such, IDO1 is a therapeutic target for inhibition in a broad array of indications, such as to promote tumor clearance, enable clearance of intractable viral or bacterial infections, decrease systemic immune dysfunction manifest as persistent inflammation during HIV infection or immunosuppression during sepsis, and prevent or reverse neurological conditions. 
     IDO1 and Persistent Inflammation in HIV Infection: 
     Despite the success of antiretroviral therapy (ART) in suppressing HIV replication and decreasing the incidence of AIDS-related conditions, HIV-infected patients on ART have a higher incidence of non-AIDS morbidities and mortality than their uninfected peers. These non-AIDS conditions include cancer, cardiovascular disease, osteoporosis, liver disease, kidney disease, frailty, and neurocognitive dysfunction (Deeks 2011). Several studies indicate that non-AIDS morbidity/mortality is associated with persistent inflammation, which remains elevated in HIV-infected patients on ART as compared to peers (Deeks 2011). As such, it is hypothesized that persistent inflammation and immune dysfunction despite virologic suppression with ART is a cause of these non-AIDS-defining events (NADEs). 
     HIV infects and kills CD4+ T cells, with particular preference for cells like those CD4+ T cells that reside in the lymphoid tissues of the mucosal surfaces (Mattapallil, Douek et al. 2005). The loss of these cells combined with the inflammatory response to infection result in a perturbed relationship between the host and all pathogens, including HIV itself, but extending to pre-existing or acquired viral infections, fungal infections, and resident bacteria in the skin and mucosal surfaces. This dysfunctional host:pathogen relationship results in the over-reaction of the host to what would typically be minor problems as well as permitting the outgrowth of pathogens among the microbiota. The dysfunctional host:pathogen interaction therefore results in increased inflammation, which in turn leads to deeper dysfunction, driving a vicious cycle. As inflammation is thought to drive non-AIDS morbidity/mortality, the mechanisms governing the altered host:pathogen interaction are therapeutic targets. 
     IDO1 expression and activity are increased during untreated and treated HIV infection as well as in primate models of SIV infection (Boasso, Vaccari et al. 2007, Favre, Lederer et al. 2009, Byakwaga, Boum et al. 2014, Hunt, Sinclair et al. 2014, Tenorio, Zheng et al. 2014). IDO1 activity, as indicated by the ratio of plasma levels of enzyme substrate and product (Kyn/Tryp or K:T ratio), is associated with other markers of inflammation and is one of the strongest predictors of non-AIDS morbidity/mortality (Byakwaga, Bourn et al. 2014, Hunt, Sinclair et al. 2014, Tenorio, Zheng et al. 2014). In addition, features consistent with the expected impact of increased IDO1 activity on the immune system are major features of HIV and SIV induced immune dysfunction, such as decreased T cell proliferative response to antigen and imbalance of Treg:Th17 in systemic and intestinal compartments (Favre, Lederer et al. 2009, Favre, Mold et al. 2010). As such, we and others hypothesize that IDO1 plays a role in driving the vicious cycle of immune dysfunction and inflammation associated with non-AIDS morbidity/mortality. Thus, we propose that inhibiting IDO1 will reduce inflammation and decrease the risk of NADEs in ART-suppressed HIV-infected persons. 
     IDO1 and Persistent Inflammation beyond HIV 
     As described above, inflammation associated with treated chronic HIV infection is a likely driver of multiple end organ diseases [Deeks 2011]. However, these end organ diseases are not unique to HIV infection and are in fact the common diseases of aging that occur at earlier ages in the HIV-infected population. In the uninfected general population inflammation of unknown etiology is a major correlate of morbidity and mortality [Pinti, 2016 #88]. Indeed many of the markers of inflammation are shared, such as IL-6 and CRP. If, as hypothesized above, IDO1 contributes to persistent inflammation in the HIV-infected population by inducing immune dysfunction in the GI tract or systemic tissues, then IDO1 may also contribute to inflammation and therefore end organ diseases in the broader population. These inflammation associated end organ diseases are exemplified by cardiovascular diseases, metabolic syndrome, liver disease (NAFLD, NASH), kidney disease, osteoporosis, and neurocognitive impairment. Indeed, the IDO1 pathway has links in the literature to liver disease (Vivoli abstracts at Italian Assoc. for the Study of the Liver Conference 2015], diabetes [Baban, 2010 #89], chronic kidney disease [Schefold, 2009 #90], cardiovascular disease [Mangge, 2014 #92; Mangge, 2014 #91], as well as general aging and all cause mortality [Pertovaara, 2006 #93]. As such, inhibition of IDO1 may have application in decreasing inflammation in the general population to decrease the incidence of specific end organ diseases associated with inflammation and aging. 
     IDO1 and Oncology 
     IDO expression can be detected in a number of human cancers (for example; melanoma, pancreatic, ovarian, AML, CRC, prostate and endometrial) and correlates with poor prognosis (Munn 2011). Multiple immunosuppressive roles have been ascribed to the action of IDO, including the induction of Treg differentiation and hyper-activation, suppression of Teff immune response, and decreased DC function, all of which impair immune recognition and promote tumor growth (Munn 2011). IDO expression in human brain tumors is correlated with reduced survival. Orthotropic and transgenic glioma mouse models demonstrate a correlation between reduced IDO expression and reduced Treg infiltration and an increased long term survival (Wainwright, Balyasnikova et al. 2012). In human melanoma a high proportion of tumors (33 of 36 cases) displayed elevated IDO suggesting an important role in establishing an immunosuppressive tumor microenvironment (TME) characterized by the expansion, activation and recruitment of MDSCs in a Treg-dependent manner (Holmgaard, Zamarin et al. 2015). Additionally, host IDO expressing immune cells have been identified in the draining lymph nodes and in the tumors themselves (Mellor and Munn 2004). Hence, both tumor and host-derived IDO are believed to contribute to the immune suppressed state of the TME. 
     The inhibition of IDO was one of the first small molecule drug strategies proposed for re-establishment of an immunogenic response to cancer (Mellor and Munn 2004). The d-enantiomer of 1-methyl tryptophan (D-1 MTor indoximod) was the first IDO inhibitor to enter clinical trials. While this compound clearly does inhibit the activity of IDO, it is a very weak inhibitor of the isolated enzyme and the in vivo mechanism(s) of action for this compound are still being elucidated. Investigators at Incyte optimized a hit compound obtained from a screening process into a potent and selective inhibitor with sufficient oral exposure to demonstrate a delay in tumor growth in a mouse melanoma model (Yue, Douty et al. 2009). Further development of this series led to INCB204360 which is a highly selective for inhibition of IDO-1 over IDO-2 and TDO in cell lines transiently transfected with either human or mouse enzymes (Liu, Shin et al. 2010). Similar potency was seen for cell lines and primary human tumors which endogenously express IDO1 (IC50s˜3-20 nM). When tested in co-culture of DCs and naïve CD4 + CD25 −  T cells, INCB204360 blocked the conversion of these T cells into CD4 + FoxP3 +  Tregs. Finally, when tested in a syngeneic model (PANO2 pancreatic cells) in immunocompetent mice, orally dosed INCB204360 provided a significant dose-dependent inhibition of tumor growth, but was without effect against the same tumor implanted in immune-deficient mice. Additional studies by the same investigators have shown a correlation of the inhibition of IDO1 with the suppression of systemic kynurenine levels and inhibition of tumor growth in an additional syngeneic tumor model in immunocompetent mice. Based upon these preclinical studies, INCB24360 entered clinical trials for the treatment of metastatic melanoma (Beatty, O′Dwyer et al. 2013). 
     In light of the importance of the catabolism of tryptophan in the maintenance of immune suppression, it is not surprising that overexpression of a second tryptophan metabolizing enzyme, TDO2, by multiple solid tumors (for example, bladder and liver carcinomas, melanomas) has also been detected. A survey of 104 human cell lines revealed 20/104 with TDO expression, 17/104 with IDO1 and 16/104 expressing both (Pilotte, Larrieu et al. 2012). Similar to the inhibition of IDO1, the selective inhibition of TDO2 is effective in reversing immune resistance in tumors overexpressing TDO2 (Pilotte, Larrieu et al. 2012). These results support TDO2 inhibition and/or dual TDO2/IDO1 inhibition as a viable therapeutic strategy to improve immune function. 
     Multiple pre-clinical studies have demonstrated significant, even synergistic, value in combining IDO-1 inhibitors in combination with T cell checkpoint modulating mAbs to CTLA-4, PD-1, and GITR. In each case, both efficacy and related PD aspects of improved immune activity/function were observed in these studies across a variety of murine models (Balachandran, Cavnar et al. 2011, Holmgaard, Zamarin et al. 2013, M. Mautino 2014, Wainwright, Chang et al. 2014). The Incyte IDO1 inhibitor (INCB204360, epacadostat) has been clinically tested in combination with a CTLA4 blocker (ipilimumab), but it is unclear that an effective dose was achieved due to dose-limited adverse events seen with the combination. In contrast recently released data for an on-going trial combining epacadostat with Merck&#39;s PD-1 mAb (pembrolizumab) demonstrated improved tolerability of the combination allowing for higher doses of the IDO1 inhibitor. There have been several clinical responses across various tumor types which is encouraging. However, it is not yet known if this combination is an improvement over the single agent activity of pembrolizumab (Gangadhar, Hamid et al. 2015). Similarly, Roche/Genentech are advancing NGL919/GDC-0919 in combination with both mAbs for PD-L1 (MPDL3280A, Atezo) and OX-40 following the recent completion of a phase 1a safety and PK/PD study in patients with advanced tumors. 
     IDO1 and Chronic Infections 
     IDO1 activity generates kynurenine pathway metabolites such as Kyn and 3-HAA that impair at least T cell, NK cell, and macrophage activity (Munn, Shafizadeh et al. 1999, Frumento, Rotondo et al. 2002) (Sekkai, Guittet et al. 1997, Favre, Mold et al. 2010). Kyn levels or the Kyn/Tryp ratio are elevated in the setting of chronic HIV infection (Byakwaga, Bourn et al. 2014, Hunt, Sinclair et al. 2014, Tenorio, Zheng et al. 2014), HBV infection (Chen, Li et al. 2009), HCV infection (Larrea, Riezu-Boj et al. 2007, Asghar, Ashiq et al. 2015), and TB infection(Suzuki, Suda et al. 2012) and are associated with antigen-specific T cell dysfunction (Boasso, Herbeuval et al. 2007, Boasso, Hardy et al. 2008, Loughman and Hunstad 2012, Ito, Ando et al. 2014, Lepiller, Soulier et al. 2015). As such, it is thought that in these cases of chronic infection, IDO1-mediated inhibition of the pathogen-specific T cell response plays a role in the persistence of infection, and that inhibition of IDO1 may have a benefit in promoting clearance and resolution of infection. 
     IDO1 and Sepsis 
     IDO1 expression and activity are observed to be elevated during sepsis and the degree of Kyn or Kyn/Tryp elevation corresponded to increased disease severity, including mortality (Tattevin, Monnier et al. 2010, Darcy, Davis et al. 2011). In animal models, blockade of IDO1 or IDO1 genetic knockouts protected mice from lethal doses of LPS or from mortality in the cecal ligation/puncture model (Jung, Lee et al. 2009, Hoshi, Osawa et al. 2014). Sepsis is characterized by an immunosuppressive phase in severe cases (Hotchkiss, Monneret et al. 2013), potentially indicating a role for IDO1 as a mediator of immune dysfunction, and indicating that pharmacologic inhibition of IDO1 may provide a clinical benefit in sepsis. 
     IDO1 and Neurological Disorders 
     In addition to immunologic settings, IDO1 activity is also linked to disease in neurological settings (reviewed in Lovelace Neuropharmacology 2016(Lovelace, Varney et al. 2016)). Kynurenine pathway metabolites such as 3-hydroxykynurenine and quinolinic acid are neurotoxic, but are balanced by alternative metabolites kynurenic acid or picolinic acid, which are neuroprotective. Neurodegenerative and psychiatric disorders in which kynurenine pathway metabolites have been demonstrated to be associated with disease include multiple sclerosis, motor neuron disorders such as amyotrophic lateral sclerosis, Huntington&#39;s disease, Parkinson&#39;s disease, Alzheimer&#39;s disease, major depressive disorder, schizophrenia, anorexia (Lovelace, Varney et al. 2016). Animal models of neurological disease have shown some impact of weak IDO1 inhibitors such as 1-methyltryptophan on disease, indicating that IDO1 inhibition may provide clinical benefit in prevention or treatment of neurological and psychiatric disorders. 
     It would therefore be an advance in the art to discover IDO inhibitors that effective the balance of the aforementioned properties as a disease modifying therapy in chronic HIV infections to decrease the incidence of non-AIDS morbidity/mortality; and/or a disease modifying therapy to prevent mortality in sepsis; and/or an immunotherapy to enhance the immune response to HIV, HBV, HCV and other chronic viral infections, chronic bacterial infections, chronic fungal infections, and to tumors; and/or for the treatment of depression or other neurological/neuropsychiatric disorders.
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     Certain IDO1 inhibitors are disclosed in U.S. provisional applications 62/481,743 and 62/436,672 (GSK docket number PR66234). 
     SUMMARY OF THE INVENTION 
     Briefly, in one aspect, the present invention discloses compounds of Formula I 
     
       
         
         
             
             
         
       
     
     or a pharmaceutically acceptable salt thereof wherein:
     R 1  is a group having Formula II   

     
       
         
         
             
             
         
       
     
     wherein R 5  and R 6  are independently H or CH 3 , or R 5  and R 6  may join together with the carbon atom to which they are bonded to form a 3-6 membered cycloalkyl; 
     R 7  is a 5 or 6-membered heterocycle or heteroaryl containing 1 to 3 heteroatoms selected from N, and S, and is optionally substituted with 1 or 2 substituents selected from the group consisting of F, CI, CN, OCH 3 , CF 3 , cyclopropyl, CONH 2 , CH 2 CH 2 OCH 3 , and CH 2 OCH 3 ; 
     R 8  is a 5, or 6-membered cycloalkyl or a 5 or 6-membered heterocycle containing an O or a N and R 8  may optionally be substituted by a substituent selected from halogen, OH, C 1-3 alkyl, and OCH 3 ; 
     one X is hydrogen and the other represents the point of attachment to Q; 
     Q is a bond, CH 2 , or 
     
       
         
         
             
             
         
       
     
     where Y 1  represents the point of attachment to R 1  and Y 2  represents the point of attachment to the rest of the compound; 
     R 2  and R 3  are independently C 10-20 alkyl; and 
     R 4  is hydrogen or C 1-4 alkyl. 
     In another aspect, the present invention discloses a method for treating diseases or conditions that would benefit from inhibition of IDO. 
     In another aspect, the present invention discloses pharmaceutical compositions comprising a compound of Formula I or a pharmaceutically acceptable salt thereof. 
     In another aspect, the present invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof for use in therapy. 
     In another aspect, the present invention provides a compound of Formula I or a pharmaceutically acceptable salt thereof for use in treating diseases or condition that would benefit from inhibition of IDO. 
     In another aspect, the present invention provides use of a compound of Formula I or a pharmaceutically acceptable salt thereof in the manufacture of a medicament for use in treating diseases or conditions that would benefit from inhibition of IDO. 
     In another aspect, the present invention discloses a method for treating a viral infection in a patient mediated at least in part by a virus in the retrovirus family of viruses, comprising administering to said patient a composition comprising a compound of Formula I, or a pharmaceutically acceptable salt thereof. In some embodiments, the viral infection is mediated by the HIV virus. 
     In another aspect, a particular embodiment of the present invention provides a method of treating a subject infected with HIV comprising administering to the subject a therapeutically effective amount of a compound of Formula I, or a pharmaceutically acceptable salt thereof. 
     In yet another aspect, a particular embodiment of the present invention provides a method of inhibiting progression of HIV infection in a subject at risk for infection with HIV comprising administering to the subject a therapeutically effective amount of a compound of Formula I, or a pharmaceutically acceptable salt thereof. Those and other embodiments are further described in the text that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1 . Concentration of INTERMEDIATE C4 from oral dosing (3 mg/kg) of INTERMEDIATE C4 in rats 
         FIG. 2 . Concentration of INTERMEDIATE C4 from oral dosing (5 mg/kg) of prodrug EXAMPLE 7 in rats 
         FIG. 3 . Comparison of the tissue distribution of INTERMEDIATE C4 from its oral dosing and of INTERMEDIATE C4 from oral dosing of its prodrug EXAMPLE 7 in rats 
     
    
    
     DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS 
     Preferably one of R 5  and R 6  is H and the other is CH 3 . 
     Preferably R 7  is a pyridine, thiadiazole, pyrimidine, pyrazine, pyridazine, triazol, or thiazol. optionally substituted with 1 or 2 substituents selected from the group consisting of F, CI, CN, OCH 3 , CF 3 , cyclopropyl, CONH 2 , CH 2 CH 2 OCH 3 , and CH 2 OCH 3 . More preferably R 7  is pyridine or pyrazine optionally substituted with a Cl. 
     Preferably R 8  is cyclohexyl or 6-membered heterocycle containing an oxygen. 
     Most preferably R 1  is selected from the group consisting of 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein the X indicates the point of attachment to the rest of the compound. 
     Preferably R 4  is H or methyl. 
     Preferred pharmaceutical compositions include unit dosage forms. Preferred unit dosage forms include tablets. 
     It is expected that the compounds and composition of this invention will be useful for prevention and/or treatment of HIV; including the prevention of the progression of AIDS and general immunosuppression. It is expected that in many cases such prevention and/or treatment will involve treating with the compounds of this invention in combination with at least one other drug thought to be useful for such prevention and/or treatment. For example, the IDO inhibitors of this invention may be used in combination with other immune therapies such as immune checkpoints (PD1, CTLA4, ICOS, etc.) and possibly in combination with growth factors or cytokine therapies (IL21, IL-7, etc.). 
     In is common practice in treatment of HIV to employ more than one effective agent. Therefore, in accordance with another embodiment of the present invention, there is provided a method for preventing or treating a viral infection in a mammal mediated at least in part by a virus in the retrovirus family of viruses which method comprises administering to a mammal, that has been diagnosed with said viral infection or is at risk of developing said viral infection, a compound as defined in Formula I, wherein said virus is an HIV virus and further comprising administration of a therapeutically effective amount of one or more agents active against an HIV virus, wherein said agent active against the HIV virus is selected from the group consisting of Nucleotide reverse transcriptase inhibitors; Non-nucleotide reverse transcriptase inhibitors; Protease inhibitors; Entry, attachment and fusion inhibitors; Integrase inhibitors; Maturation inhibitors; CXCR4 inhibitors; and CCR5 inhibitors. Examples of such additional agents are Dolutegravir, Bictegravir, and Cabotegravir. 
     “Pharmaceutically acceptable salt” refers to pharmaceutically acceptable salts derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example only, sodium, potassium, calcium, magnesium, ammonium, and tetraalkylammonium, and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, and oxalate. Suitable salts include those described in P. Heinrich Stahl, Camille G. Wermuth (Eds.), Handbook of Pharmaceutical Salts Properties, Selection, and Use; 2002. 
     The present invention also includes pharmaceutically acceptable salts of the compounds described herein. As used herein, “pharmaceutically acceptable salts” refers to derivatives of the disclosed compounds wherein the parent compound is modified by converting an existing acid or base moiety to its salt form. Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines; alkali or organic salts of acidic residues such as carboxylic acids; and the like. The pharmaceutically acceptable salts of the present invention include the conventional non-toxic salts of the parent compound formed, for example, from non-toxic inorganic or organic acids. The pharmaceutically acceptable salts of the present invention can be synthesized from the parent compound which contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid in water or in an organic solvent, or in a mixture of the two; generally, nonaqueous media like ether, ethyl acetate, ethanol, isopropanol, or ACN are preferred. 
     The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. 
     In one embodiment, the pharmaceutical formulation containing a compound of Formula I or a salt thereof is a formulation adapted for oral or parenteral administration. In another embodiment, the formulation is a long-acting parenteral formulation. In a further embodiment, the formulation is a nano-particle formulation. 
     The present invention is directed to compounds, compositions and pharmaceutical compositions that have utility as novel treatments for immunosuppression. While not wanting to be bound by any particular theory, it is thought that the present compounds are able to inhibit the enzyme that catalyzes the oxidative pyrrole ring cleavage reaction of I-Trp to N-formylkynurenine utilizing molecular oxygen or reactive oxygen species. 
     Therefore, in another embodiment of the present invention, there is provided a method for the prevention and/or treatment of HIV; including the prevention of the progression of AIDS and general immunosuppression. 
     EXAMPLES 
     The following examples serve to more fully describe the manner of making and using the above-described invention. It is understood that these examples in no way serve to limit the true scope of the invention, but rather are presented for illustrative purposes. In the examples and the synthetic schemes below, the following abbreviations have the following meanings. If an abbreviation is not defined, it has its generally accepted meaning.
     CAN=Acetonitrile   AIBN=Azobisisobutyronitrile   aq.=Aqueous   μL or uL=Microliters   μM or uM=Micromolar   NMR=nuclear magnetic resonance   boc=tert-butoxycarbonyl   br=Broad   Cbz=Benzyloxycarbonyl   CDI=1,1′-carbonyldiimidazole   d=Doublet   δ=chemical shift   ° C.=degrees celcius   DCM=Dichloromethane   dd=doublet of doublets   DHP=Dihydropyran   DIAD=diisopropyl azodicarboxylate   DIEA or DIPEA=N,N-diisopropylethylamine   DMAP=4-(dimethylamino)pyridine   DMEM=Dulbeco&#39;s Modified Eagle&#39;s Medium   EtOAc=ethyl acetate   h or hr=Hours   HATU=1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxid hexafluorophosphate   HCV=hepatitis C virus   HPLC=high performance liquid chromatography   Hz=Hertz   IU=International Units   IC 50 =inhibitory concentration at 50% inhibition   J=coupling constant (given in Hz unless otherwise indicated)   LCMS=liquid chromatography-mass spectrometry   m=Multiplet   M=Molar   M+H + =parent mass spectrum peak plus H +     MeOH=Methanol   mg=Milligram   min=Minutes   mL=Milliliter   mM=Millimolar   mmol=Millimole   MS=mass spectrum   MTBE=methyl tert-butyl ether   N=Normal   NFK=N-formylkynurenine   NBS=N-bromosuccinimide   nm=Nanomolar   PE=petroleum ether   ppm=parts per million   q.s.=sufficient amount   s=Singlet   RT=room temperature   Rf=retardation factor   sat.=Saturated   t=Triplet   TEA=Triethylamine   TFA=trifluoroacetic acid   TFAA=trifluoroacetic anhydride   THF=Tetrahydrofuran   

     Equipment Description 
       1 H NMR spectra were recorded on a Bruker Ascend 400 spectrometer or a Varian 400 spectrometer. Chemical shifts are expressed in parts per million (ppm, δ units). Coupling constants are in units of hertz (Hz). Splitting patterns describe apparent multiplicities and are designated as s (singlet), d (doublet), t (triplet), q (quartet), quint (quintet), m (multiplet), br (broad). 
     The analytical low-resolution mass spectra (MS) were recorded on Waters ACQUITY UPLC with SQ Detectors using a Waters BEH C18, 2.1×50 mm, 1.7 μm using a gradient elution method. 
     Solvent A: 0.1% formic acid (FA) in water; 
     Solvent B: 0.1% FA in acetonitrile;
     30% B for 0.5 min followed by 30-100% B over 2.5 min.   

     Synthesis of Intermediate A 
     
       
         
         
             
             
         
       
     
     Preparation of 2-hydroxypropane-1,3-diyl dipalmitate 
     
       
         
         
             
             
         
       
     
     To a solution of glycerin (1.0 g, 0.132 mmol), pyridine (16.1 mg, 0.132 mmol) in THF (20 mL), was added palmitoyl chloride (63.1 mg, 0.329 mmol) and the mixture was stirred at rt for 17 hours. The reaction mixture was diluted with DCM (5 mL), acidified with 1 N aq. HCl to pH 4˜5. The layers were separated and the organic layer was concentrated and purified by silica gel chromatography (5% to 30% ethyl acetate/hexanes) to give the title compound (1.7 g, 27%) as a white solid.  1 H NMR (400 MHz, CDCl 3 ) δ 4.21-4.07 (m, 5H), 2.44 (d, J=4.7 Hz, 1H), 2.35 (t, J=7.6 Hz, 4H), 1.67-1.58 (m, 4H), 1.30-1.23 (m, J=13.4 Hz, 48H), 0.88 (t, J=6.8 Hz, 6H). MS (ESI) m/z calcd for C 35 H 68 O 5 : 568.51. Found: 569.65 (M+1) + . 
     Intermediate A 
     5((1,3-Bis(palmitoyloxy)propan-2-yl)oxy)-5-oxopentanoic acid 
     
       
         
         
             
             
         
       
     
     A mixture of 2-hydroxypropane-1,3-diyldipalmitate (500 mg, 0.879 mmol) and glutaric anhydride (100 mg, 0.879 mmol) was stirred at 100° C. overnight. The crude product was purified by Silica gel chromatography (0˜15% EtOAc in PE) to afford the title compound (510 mg, 85%) as a white solid, which was used without purification.  1 H NMR (400 MHz, CDCl 3 ): δ 5.26 (m, 1H), 4.31 (dd, J=11.9, 4.3 Hz, 2H), 4.14 (dd, J=11.9, 5.9 Hz, 2H), 2.44 (t, J=7.4 Hz, 2H), 2.42 (t, J=7.4 Hz, 2H), 2.31 (t, J=7.6 Hz, 4H), 1.96 (m, 2H), 1.67-1.54 (m, 4H), 1.49-1.18 (m, 48H), 0.88 (t, J=6.8 Hz, 6H). Proton of the carboxy group was not found. 
     Synthesis of Intermediate B 
     
       
         
         
             
             
         
       
     
     Preparation of 4-methyldihydro-2H-pyran-2, 6(3H)-dione 
     
       
         
         
             
             
         
       
     
     A mixture of 3-methylpentanedioic acid (6.0 g, 41 mmol) and acetyl chloride (50 mL) was stirred at 70° C. for 30 hours. The reaction mixture was concentrated under reduced pressure to give a residue, which was purified by recrystallization in Et 2 O to afford the title product (2.9 g, 55% yield) as a white solid.  1 H NMR (400 MHz, CDCl 3 ) δ 2.91-2.87 (m, 1H), 2.86-2.83 (m, 1H), 2.46-2.37 (m, 2H), 2.36-2.27 (m, 1H), 1.14 (d, J=6.4 Hz, 3H). 
     Intermediate B 
     Preparation of 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoic acid 
     
       
         
         
             
             
         
       
     
     A mixture of 2-hydroxypropane-1,3-diyl dipalmitate (9.5 g, 16.75 mmol) and 4-methyldihydro-2H-pyran-2,6(3H)-dione (2.14 g, 16.75 mmol) was stirred at 100° C. overnight. The crude product was purified by silica gel chromatography (0˜30% EtOAc in PE) to afford the title compound (7.67 g, 66%) as a white solid. MS (ESI) m/z calcd for C 41  H76O 8 : 696.55. Found: 695.41 (M-1) − . 
     Synthesis of Intermediate C 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Preparation of trans-4((4-bromo-2-nitrophenyl)(isobutyl)amino)cyclohexan-1-ol 
     
       
         
         
             
             
         
       
     
     A mixture of 4-bromo-1-fluoro-2-nitrobenzene (7.4 g, 33.5 mmol), trans-4-(isobutyl amino)cyclohexan-1-ol (6.7 g, 40.2 mmol) and DIPEA (11.7 mL, 67.0 mmol) in NMP (80 mL) was stirred at 140° C. under N 2  atmosphere for 6 hr. The resulting mixture was partitioned between EtOAc and H 2 O. The layers were separated and the organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-20% EtOAc in PE) to afford the title compound (8.4 g, 67% yield) as a red oil. LCMS (ESI) m/z calcd for C 16 H 23 BrN 2 O 3 : 370.09. Found: 371.46/373.45 (M/M+2) + . 
     Preparation of 4-bromo-N-(trans-4-((tert-butyldimethylsilyl)oxy)cyclohexyl)-N- isobutyl-2-nitroaniline 
     
       
         
         
             
             
         
       
     
     To a solution of trans-4-((4-bromo-2-nitrophenyl)(isobutyl)amino)-cyclohexan-1-ol (16.2 g, 43.7 mmol) in DCM (100 mL) was added imidazole (5.9 g, 87.4 mmol) and TBSOTf (17.3 g, 65.6 mmol). After stirred at r.t. for 5 hr, the resulting mixture was quenched with H 2 O and extracted with DCM. The organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-20% EtOAc in PE) to afford the title compound (20.5 g, 96% yield). LCMS (ESI) m/z calcd for C 22 H 37 BrN 2 O 3 Si: 484.18. Found: 485.52/487.51 (M/M+2) + . 
     Preparation of methyl (E)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy)cyclohexyl) (isobutyl)amino)-3-nitrophenyl)but-2-enoate 
     
       
         
         
             
             
         
       
     
     A mixture of 4-bromo-N-(trans-4-((tert-butyldimethylsilyl)oxy)cyclohexyl)-N-isobutyl-2-nitroaniline (18.5 g, 38.14 mmol), methyl (E)-but-2-enoate (11.4 g, 114.4 mmol), TBAB (2.46 g, 7.6 mmol), Pd(o-MePh 3 P) 4  (1.5 g, 1.91 mmol) and TEA (10.6 mL, 76.28 mmol) in DMF (200 mL) was stirred at 100° C. under N 2  atmosphere overnight. The resulting mixture was partitioned between EtOAc and H 2 O. The layers were separated and the organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-10% EtOAc in PE) to afford the title compound (9.67 g, 50% yield) as a yellow oil. LCMS (ESI) m/z calcd for C 27 H 44 N 2 O 5 Si: 504.30. Found: 505.69 (M+1) + . 
     Preparation of methyl 3-(4-((trans-4-((tent-butyldimethylsilyl)oxy)cyclo hexyl)(isobutyl)amino)-3-nitrophenyl)butanoate 
     
       
         
         
             
             
         
       
     
     At −5° C., to a mixture of (CuHPh 3 P) 6  (288 mg, 0.147 mmol) and (R,S)-PPF-P(tBu) 2  (289 mg, 0.535 mmol) in toluene (90 mL) was added PMHS (2.9 mL) and t-BuOH (2.3 mL) before the introduction of methyl (E)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy) cyclohexyl)(isobutyl)amino)-3-nitrophenyl)but-2-enoate (9.67 g, 19.1 mmol). After stirred at r.t. for 2 h, the resulting mixture was quenched with aq. NaHCO 3  and extracted with EtOAc. The organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-10% EtOAc in PE) to afford the title compound (8.16 g, 88% yield) as a yellow oil. LCMS (ESI) m/z calcd for C 27 H 46 N 2 O 5 Si: 506.32. Found: 507.82 (M+1) + . 
     Preparation of (R)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy)cyclohexyl)(isobutyl) amino)-3-nitrophenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of methyl (R)-3-(3-((5-chloropyrazin-2-yl)amino)-4-((trans-4-hydroxyl cyclohexyl)(isobutyl)amino)phenyl)butanoate (3.6 g, 7.09 mmol) in MeOH (30 mL) was added 1N aq. NaOH (20 mL). After stirred at r.t for 8 h, the resulting mixture was neutralized with 1N HCl and extracted with EtOAc. The organic layer was washed with brine, dried over Na 2 SO 4  and concentrated to afford the title compound (3.3 g, 94% yield) which was used in the following step without purification. LCMS (ESI) m/z calcd for C 26 H 44 N 2 O 5 Si: 492.30. Found: 493.47 (M+1) + . 
     Preparation of tert-butyl (R)-3-(4-((trans-4-((tent-butyldimethylsilyl)oxy)cyclohexyl) (isobutyl)amino)-3-nitrophenyl)butanoate 
     
       
         
         
             
             
         
       
     
     To a solution of (R)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy)-cyclohexyl)(isobutyl) amino)-3-nitrophenyl)butanoic acid (3.3 g, 6.70 mmol) in DCM (30 mL) was added tert-butyl 2,2,2-trichloroacetimidate (2.48 g, 11.38 mmol), followed by addition of BF3.Et 2 O (0.13 mL, 1.0 mmol). After stirred at r.t for 40 h, the reaction mixture was neutralized with aq. NaHCO 3 . The layers were separated and the aqueous phase was extracted with DCM. The combined organic layers were washed with brine, dried over Na 2 SO 4  and concentrated to give the crude product, which was purified by flash chromatography (silica gel, 0-20% EtOAc in PE) to afford the title compound (2.82 g, 77% yield). LCMS (ESI) m/z calcd for C 30 H 52 N 2 O 5 Si: 548.36. Found: 549.60 (M+1) + . 
     Intermediate C 
     Preparation of tert-butyl 3-(3-amino-4-((trans-4-((tent-butyldimethylsilyl)oxy) cyclohexyl)(isobutyl)amino)phenyl)butanoate 
     
       
         
         
             
             
         
       
     
     A mixture of tert-butyl (R)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy)-cyclohexyl) (isobutyl)amino)-3-nitrophenyl)butanoate (2.82 g, 5.13 mmol) and 10% Pd/C (846 mg) in EtOAc (30 mL) was stirred at 50° C. under H 2  atmosphere for 6 h. The resulting mixture was filtered through a pad of Celite and the filtrate was concentrated under reduced pressure to give the crude product, which was purified by flash chromatography (silica gel, 0-20% EtOAc in PE) to afford the title compound (1.88 g, 71% yield) as a yellow oil. LCMS (ESI) m/z calcd for C 30 H 54 N 2 O 3 Si: 518.39. Found: 519.55 (M+1) + . 
     Synthesis of Example 1 
     
       
         
         
             
             
         
       
     
     Preparation of tert-butyl (R)-3-(4-((trans-4-((tent-butyldimethylsilyl)oxy)cyclohexyl) (isobutyl)amino)-3((6-chloropyridin-3-yl)amino)phenyl)butanoate 
     
       
         
         
             
             
         
       
     
     A mixture of tert-butyl 3-(3-amino-4-((trans-4-((tert-butyldimethylsilyl)oxy) cyclohexyl) (isobutyl)amino)phenyl)butanoate (500 mg, 0.97 mmol), 5-bromo-2-chloropyridine (374 mg, 1.94 mmol), Pd 2 (dba) 3  (170 mg, 0.194 mmol), Xantphos (225 mg, 0.388 mmol) and Cs 2 CO 3  (630 mg, 1.94 mmol) in toluene (5 mL) was stirred at 100° C. under N 2  atmosphere overnight. The resulting mixture was partitioned between EtOAc and H 2 O. The organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-10% EtOAc in PE) to afford the title compound (570 mg, 93% yield). LCMS (ESI) m/z calcd for C 35 H 56 CIN 3 O 3 Si: 629.38. Found: 630.62/632.61 (M/M+2) + . 
     Preparation of tert-butyl (R)-3-(3-((6-chloropyridin-3-yl)amino)-4-((trans-4-hydroxycyclohexyl)(isobutyl)amino)phenyl)butanoate 
     
       
         
         
             
             
         
       
     
     To a solution of tert-butyl (R)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy)-cyclohexyl) (isobutyl)amino)-3-((6-chloropyridin-3-yl)amino)phenyl)butanoate (650 mg, 1.03 mmol) in THF (5 mL) was added TBAF (1 N in THF, 5 mL). After stirred at r.t. overnight, the resulting mixture was partitioned between EtOAc and H 2 O. The organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-20% EtOAc in PE) to afford the title compound (450 mg, 84% yield). LCMS (ESI) m/z calcd for C 29 H 42 CIN 3 O 3 : 515.29. Found: 516.67/518.63 (M/M+2) + . 
     Intermediate C2 
     (R)-3-(3-((6-chloropyridin-3-yl)amino)-4-(((1r,4R)-4 hydroxycyclohexyl)(isobutyl)amino)-phenyl)butanoic acid was obtained by treatment of tert-butyl (R)-3-(3-((6-chloropyridin-3-yl)amino)-4-((trans-4-hydroxy cyclohexyl)(isobutyl)amino)phenyl)butanoate with excess 4N HCl in dioxane and solvent removal. 
     
       
         
         
             
             
         
       
     
     Preparation of 1,3-bis(palmitoyloxy)propan-2-yl (trans-4-((4(R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((6-chloropyridin-3-yl)amino)phenyl)(isobutyl)amino)cyclohexyl) glutarate 
     
       
         
         
             
             
         
       
     
     To a solution of 1,3-bis(palmitoyloxy)propan-2-yl (trans-4-((4-((R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((6-chloropyridin-3-yl)amino)phenyl)(isobutyl)amino)-cyclohexyl) glutarate (150 mg, 0.29 mmol), 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-5-oxopentanoic acid (397 mg, 0.58 mmol) and DMAP (35 mg, 0.29 mmol) in DMF (5 mL), was added EDCI (112 mg, 0.58 mmol). After stirred at 60° C. for 17 hours, the reaction mixture was partitioned between EtOAc and water and the layers were separated. The organic layer was washed with brine, dried over Na 2 SO 4 , concentrated under reduced pressure and 3 the title compound (70 mg, 20%) as a yellow oil. MS (ESI) m/z calcd for C 69 H 114 ClN 3 O 10 : 1179.82. Found: 1181.27/1183.29 (M/M+2) + . 
     EXAMPLE 1 
     Preparation of (R)-3-(4-((trans-4-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-5-oxopentanoyl)oxy)cyclohexyl) (isobutyl)amino)-3-((6-chloropyridin-3-yl)amino) phenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of 1,3-bis(palmitoyloxy)propan-2-yl (trans-4-((4-((R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((6-chloropyridin-3-yl)amino)phenyl)(isobutyl)amino)-cyclohexyl) glutarate (70 mg, 0.1059 mmol) in DCM (3 mL), was added TFA (1 mL) and the mixture was stirred at rt for 2 hours. The reaction mixture was concentrated under reduced pressure. Purification by preparative TLC (5% to 10% ethyl acetate/hexanes) gave the title compound (37 mg, 55%) as a light yellow oil. MS (ESI) m/z calcd for C 65 H 106 ClN 3 O 10 : 1123.76. Found: 1124.79/1126.82 (M/M+2) + . 
     Synthesis of Example 2 
     
       
         
         
             
             
         
       
     
     Preparation of tert-butyl (R)-3-(4-((trans-4-((tent-butyldimethylsilyl)oxy)cyclohexyl) (isobutyl)amino)-3-((5-chloropyrazin-2-yl)amino)phenyl)butanoate 
     
       
         
         
             
             
         
       
     
     A mixture of tert-butyl (R)-3-(3-amino-4-((trans-4-((tert-butyldimethylsilyl)oxy)cyclohexyl) (isobutyl)amino)phenyl)butanoate (500 mg, 0.97 mmol), 2,5-dichloropyrazine (290 mg, 1.94 mmol), Pd 2 (dba) 3  (178 mg, 0.194 mmol), Xantphos (225 mg, 0.388 mmol) and Cs 2 CO 3  (630 mg, 1.94 mmol) in toluene (5 mL) was stirred at 100° C. under N 2  atmosphere overnight. The resulting mixture was partitioned between EtOAc and H 2 O. After the layers were separated, the organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-30% EtOAc in PE) to afford the title compound (410 mg, 67% yield). LCMS (ESI) m/z calcd for C 34 H 55 ClN 4 O 3 Si: 630.37. Found: 631.39/633.40 (M/M+2) + . 
     Preparation of tert-butyl (R)-3-(3-((5-chloropyrazin-2-yl)amino)-4-((trans-4-hydroxy cyclohexyl)(isobutyl)amino)phenyl)butanoate 
     
       
         
         
             
             
         
       
     
     To a solution of tert-butyl (R)-3-(4-((trans-4-((tert-butyldimethylsilyl)oxy)-cyclohexyl) (isobutyl)amino)-3-((5-chloropyrazin-2-yl)amino)phenyl)butanoate (410 mg, 0.65 mmol) in THF (3 mL) was added TBAF (1 N in THF, 3 mL). After stirred at r.t. overnight, the resulting mixture was partitioned between EtOAc and H 2 O. The organic layer was washed with brine, dried over Na 2 SO 4 , filtered and concentrated to give the crude product which was purified by flash chromatography (silica gel, 0-30% EtOAc in PE) to afford the title compound (310 mg, 92% yield). LCMS (ESI) m/z calcd for C 28 H 41 ClN 4 O 3 : 516.29. Found: 517.65/519.62 (M/M+2) + .
     Intermediate C3 was obtained analogously to the synthesis of intermediate C2   

     (R)-3-(3((5-chloropyrazin-2-yl)amino)-44(1r,4R)-4 hydroxycyclohexyl)(isobutyl)amino)phenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     Preparation of 1,3-bis(palmitoyloxy)propan-2-yl (trans-4-((4-(R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((5-chloropyrazin-2-yl)amino)phenyl)(isobutyl)amino)cyclohexyl) glutarate 
     
       
         
         
             
             
         
       
     
     To a solution of tert-butyl (R)-3-(3-((5-chloropyrazin-2-yl)amino)-4-((trans-4-hydroxy cyclohexyl)(isobutyl)amino)phenyl)butanoate (120 mg, 0.233 mmol), 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-5-oxopentanoic acid (318 mg, 0.466 mmol) and DMAP (614 mg, 0.932 mmol) in DMF (3 mL), was added EDCI (89 mg, 0.466 mmol) and the mixture was stirred at 40° C. for 8 h. the resulting mixture was partitioned between EtOAc and H 2 O. The organic layer was washed with brine, dried over Na 2 SO 4 , and concentrated to give the crude product, which was purified by flash chromatography (silica gel, 5% to 10% ethyl acetate/hexanes) to afford the title compound (50 mg, 18%) as a yellow oil. MS (ESI) m/z calcd for C 68 H 113 ClN 4 O 10 : 1180.81. Found: 1182.28/1184.30 (M+1) + . 
     EXAMPLE 2 
     Preparation of (R)-3-(4-((trans-4-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-5-oxopentanoyl)oxy)cyclohexyl) (isobutyl)amino)-3-((5-chloropyrazin-2-yl)amino) phenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of 1,3-bis(palmitoyloxy)propan-2-yl (trans-4-((4-((R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((5-chloropyrazin-2-yl)amino)phenyl)-(isobutyl)amino)cyclohexyl) glutarate (50 mg, 0.042 mmol) in DCM (3 mL), was added TFA (1 mL) and the mixture was stirred at rt for 3 h. The reaction mixture was concentrated under reduced pressure. Purification by flash chromatography (silica gel, 5% to 30% ethyl acetate/hexanes) afforded the title compound (30 mg, 63%) as a light yellow oil. MS (ESI) m/z calcd for C 64 H 105 ClN 4 O 10 : 1124.75. Found: 1126.24/1128.26 (M/M+2) + . 
     Synthesis of Example 3 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(trans-4-((4-(R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((6-chloropyridin-3-yl)amino)phenyl)(isobutyl)amino) cyclohexyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a solution of 1,3-bis(palmitoyloxy)propan-2-yl (trans-4-((4-((R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((6-chloropyridin-3-yl)amino)phenyl)(isobutyl)amino)-cyclohexyl) glutarate (100 mg, 0.194 mmol), 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoic acid (149 mg, 0.213 mmol) and DMAP (24 mg, 0.194 mmol) in DCM (5 mL), was added EDCI (75 mg, 0.388 mmol) and the mixture was stirred at 40° C. overnight. The reaction mixture was diluted with DCM (5 mL), silica gel was added and the mixture concentrated under reduced pressure. Purification by silica gel chromatography (5% to 10% ethyl acetate/hexanes) gave the title compound (190 mg, 82%) as a colorless oil; MS (ESI) m/z calcd for C 70 H 116 ClN 3 O 10 : 1193.83. 
     EXAMPLE 3 
     Preparation of (3R)-3-(4-((trans-4-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoyl)oxy)cyclohexyl) (isobutyl)amino)-3-((6-chloropyridin-3-yl)amino)phenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoic acid (190 mg, 0.159 mmol) in DCM (4 mL), was added TFA (2 mL) and the mixture was stirred at rt for 5 h. The reaction mixture was concentrated under reduced pressure. Purification by preparative TLC (5% to 10% ethyl acetate/hexanes) gave the title compound (138 mg, 76%) as a light yellow solid. H NMR (400 MHz, CDCl 3 ) δ 8.24 (d, J=2.9 Hz, 1H), 7.42 (dd, J=8.6, 3.0 Hz, 1H), 7.22 (d, J=8.6 Hz, 1H), 7.09 (d, J=8.1 Hz, 2H), 6.77 (dd, J=8.2, 1.8 Hz, 1H), 5.29-5.20 (m, 1H), 4.62-4.53 (m, 1H), 4.33-4.24 (m, 2H), 4.17-4.09 (m, 2H), 3.27-3.17 (m, 1H), 2.93-2.70 (m, 2H), 2.67-2.53 (m, 3H), 2.43-2.27 (m, 7H), 2.24-2.12 (m, 2H), 2.00-1.83 (m, 4H), 1.59 (dd, J=14.1, 7.1 Hz, 4H), 1.50-1.38 (m, 3H), 1.31-1.19 (m, 54H), 0.97 (d, J=6.5 Hz, 3H), 0.90-0.82 (m, 12H). The proton of the carboxy group was not observed. MS (ESI) m/z calcd for C 66 H 108 ClN 3 O 10 : 1137.77. Found: 1138.57/1140.57 (M/M+2) + . 
     Synthesis of Example 4 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(trans-4-((4-(R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((5-chloropyrazin-2-yl)amino)phenyl)(isobutyl)amino) cyclohexyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a solution of tert-butyl (R)-3-(3-((5-chloropyrazin-2-yl)amino)-4-((trans-4-hydroxy cyclohexyl)(isobutyl)amino)phenyl)butanoate (80.0 mg, 0.154 mmol), 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoic acid (119 mg, 0.17 mmol) and DMAP (19 mg, 0.154 mmol) in DCM (3 mL), was added EDCI (58 mg, 0.308 mmol) and the mixture was stirred 40° C. rt overnight. The reaction mixture was diluted with DCM (5 mL), silica gel was added and the mixture concentrated under reduced pressure. Purification by silica gel chromatography (5% to 10% ethyl acetate/hexanes) gave the title compound (160 mg, 87%) as a colorless oil; MS (ESI) m/z calcd for C 69 H 115 ClN 4 O 10 : 1194.83. Found: 1196.21/1198.19 (M+1) + . 
     EXAMPLE 4 
     Preparation of (3R)-3-(4-((trans-4-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoyl)oxy)cyclohexyl) (isobutyl)amino)-3-((5-chloropyrazin-2-yl)amino)phenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(trans-4-((4-((R)-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((5-chloropyrazin-2-yl)amino)phenyl)-(isobutyl)amino) cyclohexyl) 3-methylpentanedioate (160 mg, 0.133 mmol) in DCM (5 mL), was added TFA (3 mL) and the mixture was stirred at rt for 5 h. The reaction mixture was concentrated under reduced pressure. Purification by flash chromatography (silica gel, 5% to 40% ethyl acetate/hexanes) gave the title compound (68 mg, 44%) as a light yellow oil. MS (ESI) m/z calcd for C 65 H 107 ClN 4 O 10 : 1138.77. Found: 1139.63/1140.63 (M/M+2) + . 
     Synthesis of Intermediate D 
     
       
         
         
             
             
         
       
     
     Preparation of 3,3,5,7-tetramethylchroman-2-one 
     
       
         
         
             
             
         
       
     
     A solution of 3,5-dimethylphenol (5.0 g, 40.93 mmol) and methyl 3-methylbut-2-enoate (5.14 g, 45.02 mmol) in methanesulfonic acid (10 mL) was stirred at 70° C. overnight. The reaction mixture was poured into water and extracted with EtOAc. The organic layers were combined and washed sequentially with water, and brine, and dried over MgSO 4 . Solvent was removed under vacuum and the residue was purified by flash chromatography (silica gel, 0˜60% ethyl acetate in petroleum ether) to afford the title compound (8.0 g, 96% yield) as a white solid. LCMS (ESI) m/z calcd for C 13 H 16 O 2 : 204.12. Found: 205.24 (M+1) + . 
     Preparation of 2-(4-hydroxy-2-methylbutan-2-yl)-3,5-dimethylphenol 
     
       
         
         
             
             
         
       
     
     At 0° C., a mixture of 3,3,5,7-tetramethylchroman-2-one (4.0 g, 19.60 mmol) in THF (180 mL) was added LiAlH 4  portion wise. After stirred at r.t. for 1.5 h, the reaction was quenched with saturated aq. NH 4 Cl solution and the solid was removed by filtration. The filtrate was concentrated in vacuum and the residue was purified by flash chromatography (silica gel, 0˜60% ethyl acetate in petroleum ether) to afford the title compound (900 mg, 23% yield) as a white solid. LCMS (ESI) m/z calcd for C 13 H 20 O 2 : 208.15. Found: 209.2 (M+1) + . 
     Preparation of 2-(4-((tent-butyldimethylsilyl)oxy)-2-methylbutan-2-yl)-3,5-dimethylphenol 
     
       
         
         
             
             
         
       
     
     At 0° C., to a solution of 2-(4-hydroxy-2-methylbutan-2-yl)-3,5-dimethylphenol (900 mg, 4.33 mmol) and imidazole (737 mg, 10.82) in DMF was added TBSCl (974 mg, 6.490). After stirred at r.t. for 2 h, the mixture reaction was poured into water and extracted with EtOAc. The organic layers were combined and washed sequentially with water, and brine, and dried over MgSO 4 . Solvent was removed under vacuum and the residue was purified by flash chromatography (silica gel, 0˜80% ethyl acetate in petroleum ether) to afford the title compound (1.12 g, 81% yield) as a white solid. LCMS (ESI) m/z calcd for C 19 H 34 O 2 Si: 322.23. Found: 323.41 (M+1) + . 
     Synthesis of Intermediate E 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(2-(4-((tent-butyldimethylsilyl) oxy)-2-methylbutan-2-yl)-3,5-dimethylphenyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a solution of 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoic acid (1.2 g, 1.72 mmol), 2-(4-((tert-butyldimethylsilyl)oxy)-2-methylbutan-2-yl)-3,5-dimethylphenol (665 mg, 2.07 mmol) and DMAP (210 mg, 1.72 mmol) in DCM (12 mL), was added EDCI (658 mg, 3.44 mmol) and the mixture was stirred at rt for 17 h. The reaction mixture was concentrated under reduced pressure to give a residue, which was purified by silica gel chromatography (5% to 10% EtOAc in PE) to afford the title compound (1.46 g, 85%). MS (ESI) m/z calcd for C 60 H 108 O 9 Si: 1000.78. Found: 1001.82 (M+1) + . 
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(2-(4-hydroxy-2-methylbutan-2-yl)-3,5-dimethylphenyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a solution of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(2-(4-((tert-butyldimethylsilyl) oxy)-2-methylbutan-2-yl)-3,5-dimethylphenyl) 3-methylpentanedioate (1.3 g, 1.3 mmol) in DCM (10 mL) and MeOH (10 mL) was added 10-Camphorsulfonic acid (91 mg, 0.39 mmol) and the mixture was stirred at rt for 6 h. The reaction was diluted with DCM and the organic phase washed with sat. aq. NaHCO3 and brine, dried over Na 2 SO 4  and concentrated under reduced pressure to give the crude product, which was purified by silica gel chromatography (5% to 20% EtOAc in PE) to afford the title compound (1.1 g, 95%) as a colorless oil. MS (ESI) m/z calcd for C 54 H 94 O 9 : 886.69. Found: 887.83 (M+1) + . 
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(3,5-dimethyl-2-(2-methyl-4-oxobutan-2-yl)phenyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a suspension of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(2-(4-hydroxy-2-methylbutan-2-yl)-3,5-dimethylphenyl) 3-methylpentanedioate (1.0 g, 1.13 mmol) and Celite (625 mg) in DCM (10 mL) was added PCC (485 mg, 2.25 mmol) and the mixture was stirred at rt for 4 hours. The reaction was filtered through a short pad of silica gel, eluting with 50% ethyl acetate/hexanes, and the filtrate was concentrated under reduced pressure to give the title compound (640 mg, 64% yield) as a yellow oil, which was used in the following step without purification. 
     Preparation of 3-(2-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoyl)oxy)-4,6-dimethylphenyl)-3-methylbutanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(3,5-dimethyl-2-(2-methyl-4-oxobutan-2-yl)phenyl) 3-methylpentanedioate (449 mg, 0.52 mmol) in acetone (12 mL) was added KMnO 4  (122 mg, 0.77 mmol) in 1:1 acetone/water (12 mL total) and the mixture was stirred at rt for 15 hours. The reaction was diluted with water (100 mL), acidified to pH ˜2 with 1 M HCl, and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with brine, dried over Na 2 SO 4  and concentrated under reduced pressure to give the crude product, which was purified by silica gel chromatography (10% to 30% ethyl acetate/hexanes) to afford the title compound (216 mg, 46%). MS (ESI) m/z calcd for C 54 H 92 O 10 : 900.67. Found: 901.83 (M+1) + . 
     Synthesis of Example 5 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(2-(4-(trans-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((5-chloropyrazin-2-yl)amino)phenyl)(isobutyl) amino)cyclohexyl) oxy)-2-methyl-4-oxobutan-2-yl)-3,5-dimethylphenyl) 3-methyl pentanedioate 
     
       
         
         
             
             
         
       
     
     To a solution of 3-(2-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoyl)oxy)-4,6-dimethylphenyl)-3-methylbutanoic acid (156 mg, 0.165 mmol), 2-(4-((tert-butyldimethylsilyl)oxy)-2-methylbutan-2-yl)-3,5-dimethylphenol (60 mg, 0.11 mmol) and DMAP (13 mg, 0.11 mmol) in DCM (3 mL), was added EDCl (42 mg, 0.22 mmol) and the mixture was stirred at rt overnight. The reaction mixture was concentrated under reduced pressure and purified by silica gel chromatography (5% to 20% ethyl acetate/hexanes) gave the title compound (120 mg, 52%) as a colorless oil; MS (ESI) m/z calcd for C 82 H 131 ClN 4 O 12 : 1398.95. Found: 1400.41/1402. 42(M+1) + . 
     EXAMPLE 5 
     Preparation of (3R)-3-(4-((trans-4-((3-(2-((5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoyl)oxy)-4,6-dimethylphenyl)-3-methylbutanoyl)oxy) cyclohexyl)(isobutyl)amino)-3-((5-chloropyrazin-2-yl)amino)phenyl)butanoic acid 
     
       
         
         
             
             
         
       
     
     To a solution of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(2-(4-(trans-4-(tert-butoxy)-4-oxobutan-2-yl)-2-((5-chloropyrazin-2-yl)amino)phenyl)(isobutyl) amino)cyclohexyl) oxy)-2-methyl-4-oxobutan-2-yl)-3,5-dimethylphenyl) 3-methyl pentanedioate (30 mg, 0.021 mmol) in DCM (2 mL), was added TFA (1 mL) and the mixture was stirred at rt for 3 hours. The reaction mixture was concentrated under reduced pressure. Purification by preparative TLC gave the title compound (25 mg, 86%) as a light yellow oil.  1 H NMR (400 MHz, CDCl 3 ) δ 8.25-8.16 (m, 1H), 8.11 (d, J=1.2 Hz, 1H), 8.07-8.02 (m, 1H), 7.89-7.84 (m, 1H), 7.05-7.00 (m, 1H), 6.79-6.73 (m, 1H), 6.69 (s, 1H), 6.46 (s, 1H), 5.24-5.14 (m, 1H), 4.42-4.30 (m, 1H), 4.28-4.19 (m, 2H), 4.13-4.03 (m, 2H), 3.25-3.17 (m, 1H), 2.70-2.63 (m, 3H), 2.58-2.38 (m, 9H), 2.26-2.20 (m, 5H), 2.15-2.09 (m, 3H), 1.79-1.68 (m, 3H), 1.57-1.49 (m, 5H), 1.44 (s, 6H), 1.23-1.15 (m, 59H), 1.03 (d, J=6.2 Hz, 3H), 0.82-0.74 (m, 12H). The proton of the carboxy group was not observed. MS (ESI) m/z calcd for C 78 H 123 ClN 4 O 12 : 1342.88. Found: 1344.60/1346.65 (M+1) + . 
     Synthesis of Intermediate E 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(chloromethyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a suspension of 5-((1,3-bis(palmitoyloxy)propan-2-yl)oxy)-3-methyl-5-oxopentanoic acid (2.5 g, 3.59 mmol), water (15 mL), DCM (15 mL), NaHCO 3  (1.17 g, 14.3 mmol) and n-tetrabutyl ammonium hydrogen sulfate (165 mg, 0.359 mmol) was added chloromethyl chlorosulfate (580 mg, 3.59 mmol. The reaction was stirred at room temperature for 16 h. The layers were separated, the organic layer was washed with brine, dried over Na 2 SO 4  and concentrated to give a residue, which was purified to give the title compound (1.65 g, 62%). MS (ESI) m/z calcd for C 42 H 77 ClO 8 : 744.53. Found: 745.61/747.57 (M/M+2) + . 
     Synthesis of Example 6 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-((((R)-3-(3-((6-chloropyridin-3-yl)amino)-4-(isobutyl(tetrahydro-2H-pyran-4-yl)amino)phenyl)butanoyl)oxy)methyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a suspension of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(chloromethyl) 3-methylpentanedioate (200 mg, 0.269 mmol), K 2 CO 3  (74 mg, 0.538 mmol), NaI (4 mg, 0.0269 mmol) in DMSO (5.0 mL) was added (R)-3-(3-((6-chloropyridin-3-yl)amino)-4-(isobutyl(tetrahydro-2H-pyran-4-yl)amino)phenyl)butanoic acid (120 mg, 0.269 mmol). 
     After stirred at 40° C. for 16 h, the reaction mixture was partitioned between EtOAc and water, and the layers were separated. The organic layer was washed with brine, dried over anhydrous sodium sulfate and concentrated to give a residue, which was purified by preparative HPLC to give the title compound (122 mg, 40% yield) as a yellow solid.  1 H NMR (400 MHz, CDCl 3 ) δ 8.20 (d, J=2.9 Hz, 1H), 7.44 (dd, J=8.6, 3.0 Hz, 1H), 7.23 (d, J=8.6 Hz, 1H), 7.15-7.01 (m, 3H), 6.73 (dd, J=8.1, 1.9 Hz, 1H), 5.74 (d, J=5.6 Hz, 1H), 5.71 (d, J=5.6 Hz, 1H), 5.31-5.19 (m, 1H), 4.38-4.22 (m, 2H), 4.22-4.07 (m, 2H), 4.02-3.86 (m, 2H), 3.36-3.11 (m, 3H), 2.79 (d, J=4.9 Hz, 3H), 2.65 (dd, J=15.5, 6.4 Hz, 1H), 2.55 (dd, J=15.5, 8.5 Hz, 1H), 2.49-2.36 (m, 3H), 2.34-2.24 (m, 6H), 1.71-1.62 (m, 5H), 1.50-1.39 (m, 1H), 1.32-1.20 (m, 54H), 1.02 (d, J=6.3 Hz, 3H), 0.90-0.84 (m, 12H). MS (ESI) m/z calcd for C 66 H 108 ClN 3 O 11 : 1153.77. Found: 1154.61/1156.61 (M/M+2) + .
     intermediate C4 was obtained analogously to the synthesis of intermediate C2   

     
       
         
         
             
             
         
       
     
     Synthesis of Example 7 
     
       
         
         
             
             
         
       
     
     Preparation of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-((((R)-3-(3-((5-chloropyrazin-2-yl)amino)-4-(isobutyl(tetrahydro-2H-pyran-4-yl)amino)phenyl)butanoyl)oxy) methyl) 3-methylpentanedioate 
     
       
         
         
             
             
         
       
     
     To a suspension of 1-(1,3-bis(palmitoyloxy)propan-2-yl) 5-(chloromethyl) 3-methylpentanedioate (150 mg, 0.201 mmol), K 2 CO 3  (55 mg, 0.402 mmol), NaI (3 mg, 0.02 mmol) in DMSO (5.0 mL) was added (R)-3-(3-((5-chloropyrazin-2-yl)amino)-4-(isobutyl(tetrahydro-2H-pyran-4-yl)amino)phenyl)butanoic acid (90 mg, 0.201 mmol). After stirred at 40° C. for 16 h, the reaction mixture was partitioned between EtOAc and water, and the layers were separated. The organic layer was washed with brine, dried over anhydrous sodium sulfate and concentrated to give a residue, which was purified by preparative HPLC to give the title compound (108 mg, 46% yield) as a yellow solid. 1H NMR (400 MHz, CDCl3) δ 8.40 (s, 1H), 8.18 (dd, J=11.8, 1.6 Hz, 2H), 7.93 (d, J=1.3 Hz, 1H), 7.13 (d, J=8.1 Hz, 1H), 6.83 (dd, J=8.1, 2.0 Hz, 1H), 5.76 (d, J=5.6 Hz, 1H), 5.72 (d, J=5.6 Hz, 1H), 5.30-5.22 (m, 1H), 4.35-4.26 (m, 2H), 4.18-4.10 (m, 2H), 3.99-3.90 (m, 2H), 3.34-3.23 (m, 3H), 2.93-2.76 (m, 3H), 2.71 (dd, J=15.5, 6.0 Hz, 1H), 2.60 (dd, J=15.5, 8.9 Hz, 1H), 2.48-2.36 (m, 3H), 2.34-2.24 (m, 6H), 1.77-1.61 (m, 5H), 1.49-1.42 (m, 1H), 1.37-1.16 (m, 54H), 1.02 (d, J=6.3 Hz, 3H), 0.91-0.84 (m, 12H). MS (ESI) m/z calcd for C 65 H 107 ClN 4 O 11 : 1154.76. Found: 1155.60/1157.59 (M/M+2) + .
     intermediate C5 was obtained analogously to the synthesis of intermediate C2   

     
       
         
         
             
             
         
       
     
     IDO1 PBMC RapidFire MS Assay 
     Compounds of the present invention were tested via high-throughput cellular assays utilizing detection of kynurenine via mass spectrometry and cytotoxicity as end-points. For the mass spectrometry and cytotoxicity assays, human peripheral blood mononuclear cells (PBMC) (PB003F; AllCells®, Alameda, Calif.) were stimulated with human interferon-γ (IFN-γ) (Sigma-Aldrich Corporation, St. Louis, Mo.) and lipopolysaccharide from Salmonella minnesota (LPS) (Invivogen, San Diego, Calif.) to induce the expression of indoleamine 2, 3-dioxygenase (IDO1). Compounds with IDO1 inhibitory properties decreased the amount of kynurenine produced by the cells via the tryptophan catabolic pathway. Cellular toxicity due to the effect of compound treatment was measured using CellTiter-Glo® reagent (CTG) (Promega Corporation, Madison, Wis.), which is based on luminescent detection of ATP, an indicator of metabolically active cells. 
     In preparation for the assays, test compounds were serially diluted 3-fold in 
     DMSO from a typical top concentration of 1 mM or 5 mM and plated at 0.5 μL in 384-well, polystyrene, clear bottom, tissue culture treated plates with lids (Greiner Bio-One, Kremsmünster, Austria) to generate 11-point dose response curves. Low control wells (0% kynurenine or 100% cytotoxicity) contained either 0.5 μL of DMSO in the presence of unstimulated (−IFN-γ/−LPS) PBMCs for the mass spectrometry assay or 0.5 μL of DMSO in the absence of cells for the cytotoxicity assay, and high control wells (100% kynurenine or 0% cytotoxicity) contained 0.5 μL of DMSO in the presence of stimulated (+IFN-γ/+LPS) PBMCs for both the mass spectrometry and cytotoxicity assays. 
     Frozen stocks of PBMCs were washed and recovered in RPMI 1640 medium (Thermo Fisher Scientific, Inc., Waltham, Mass.) supplemented with 10% v/v heat-inactivated fetal bovine serum (FBS) (Thermo Fisher Scientific, Inc., Waltham, Mass.), and 1× penicillin-streptomycin antibiotic solution (Thermo Fisher Scientific, Inc., Waltham, Mass.). The cells were diluted to 1,000,000 cells/mL in the supplemented RPMI 1640 medium. 50 μL of either the cell suspension, for the mass spectrometry assay, or medium alone, for the cytotoxicity assay, were added to the low control wells, on the previously prepared 384-well compound plates, resulting in 50,000 cells/well or 0 cells/well respectively. IFN- y and LPS were added to the remaining cell suspension at final concentrations of 100 ng/ml and 50 ng/ml respectively, and 50 μL of the stimulated cells were added to all remaining wells on the 384-well compound plates. The plates, with lids, were then placed in a 37oC, 5% CO2 humidified incubator for 2 days. 
     Following incubation, the 384-well plates were removed from the incubator and allowed to equilibrate to room temperature for 30 minutes. For the cytotoxicity assay, CellTiter-Glo® was prepared according to the manufacturer&#39;s instructions, and 40 μL were added to each plate well. After a twenty minute incubation at room temperature, luminescence was read on an EnVision® Multilabel Reader (Perkin Elmer Inc., Waltham, Mass.). For the mass spectrometry assay, 10 μL of supernatant from each well of the compound-treated plates were added to 40 μL of acetonitrile, containing 10 μM of an internal standard for normalization, in 384-well, polypropylene, V-bottom plates (Greiner Bio-One, Kremsmunster, Austria) to extract the organic analytes. Following centrifugation at 2000 rpm for 10 minutes, 10 μL from each well of the acetonitrile extraction plates were added to 90 μL of sterile, distilled H 2 O in 384-well, polypropylene, V-bottom plates for analysis of kynurenine and the internal standard on the RapidFire 300 (Agilent Technologies, Santa Clara, Calif.) and 4000 QTRAP MS (SCIEX, Framingham, Mass.). MS data were integrated using Agilent Technologies&#39; RapidFire Integrator software, and data were normalized for analysis as a ratio of kynurenine to the internal standard. 
     The data for dose responses in the mass spectrometry assay were plotted as % IDO1 inhibition versus compound concentration following normalization using the formula 100-(100*((U-C2)/(C1-C2))), where U was the unknown value, C1 was the average of the high (100% kynurenine; 0% inhibition) control wells and C2 was the average of the low (0% kynurenine; 100% inhibition) control wells. The data for dose responses in the cytotoxicity assay were plotted as % cytotoxicity versus compound concentration following normalization using the formula 100-(100*((U-C2)/(C1-C2))), where U was the unknown value, C1 was the average of the high (0% cytotoxicity) control wells and C2 was the average of the low (100% cytotoxicity) control wells. Curve fitting was performed with the equation y=A+((B−A)/(1+(10×/10C)D)), where A was the minimum response, B was the maximum response, C was the log(XC50) and D was the Hill slope. The results for each test compound were recorded as pIC50 values for the mass spectrometry assay and as pCC50 values for the cytoxicity assay (-C in the above equation). 
                                                     PBMC PXC50   PBMC TOX PXC50                                                        example 1   6.8   &lt;5           example 2   6.6   &lt;5           example 3   5.9   &lt;5           example 4   5.1   &lt;5           example 5   6.2   &lt;5           example 6   5.5   &lt;5           example 7   6   &lt;5           intermediate C2   8.7   &lt;5           intermediate C3   8.9   &lt;5           intermediate C4   9   &lt;5           intermediate C5   9.2   &lt;5                        
Rat oral PK studies of prodrugs at 5 mg/kg dose (solution in 100% (40 mg oleic acid+25mg Tween 80+2 mL of PBS/fresh) at 0.5 mg/mL).
 
                                            DNAUC0_20 [hr*ng/mL] after PO dose of 5 mg/kg            example 2 in male Wistar Han rat                             prodrug example 2   intermediate C3                       not detected   4.25                                     DNAUC0_20 [hr*ng/mL] after PO dose of 5 mg/kg            example 5 in male Wistar Han rat                             prodrug example 5   intermediate C3                       not detected   4.3                                     DNAUC0_20 [hr*ng/mL] after PO dose of 5 mg/kg            example 6 in male Wistar Han rat                             prodrug example 6   intermediate C5                       not detected   75                                     DNAUC0_20 [hr*ng/mL] after PO dose of 5 mg/kg            example 7 in male Wistar Han rat                             prodrug example 7   intermediate C4                       not detected   126.6                        
Tissue Distribution of drug intermediate C4 from oral dosing of C4 and of intermediate C4 from oral dosing of example 7 in rats
 
     EXAMPLE 7 
     
         
         Wistar Han rat, 185-197 g, male, N=8, purchased from Beijing Vital River Co. LTD. Qualification No.: SCXK(J) 2016-0011 11400700240027. Fasted overnight and fed 4 hr post dose. PO: 5 mg/kg (10 mL/kg) via oral gavage(N=8). Sampling at 1, 4, 8 and 24 hr , 4 time points, terminal bleeding for plasma, liver, lymph nodes and spleen collected at each time point 
       
    
     Intermediate C4 
     
         
         Wistar Han rat, 185-197 g, male, N=8, purchased from Beijing Vital River Co. LTD. Qualification No.: SCXK(J) 2016-0011 11400700240027. Fasted overnight and fed 4 hr post dose. PO: 3 mg/kg (10 mL/kg) via oral gavage(N=8). Sampling at 1, 4, 8 and 24 hr , 4 time points, terminal bleeding for plasma, liver, lymph nodes and spleen collected at each time point. 
       
    
     
       
         
           
               
             
               
                   
               
             
            
               
                 Individual and mean plasma concentration-time data of  
               
               
                 INTERMEDIATE C4 after a PO dose of 3 mg/kg in male  
               
               
                 Wistar Han rat 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Sampling 
                 Concentration 
                   
               
               
                 Dose 
                 Dose 
                 time 
                 (ng/mL) 
                 Mean 
               
               
                 (mg/kg) 
                 route 
                 (hr) 
                 individual 
                 (ng/mL) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 3 
                 PO 
                 1 
                 351 
                 317 
                 334 
               
               
                   
                   
                 4 
                 68.2 
                 61.2 
                 64.7 
               
               
                   
                   
                 8 
                 33.7 
                 22.7 
                 28.2 
               
               
                   
                   
                 24 
                 BQL 
                 BQL 
                 BQL 
               
               
                   
               
            
           
           
               
               
               
            
               
                 PK parameters 
                 Unit 
                 Mean 
               
               
                   
               
               
                 Tmax 
                 hr 
                 1.00 
               
               
                 Cmax 
                 ng/mL 
                 334 
               
               
                 Terminal t1 /2   
                 hr 
                 2.01 
               
               
                 Regression  
                 hr 
                 1~8 
               
               
                 Points 
                   
                   
               
               
                 AUClast 
                 hr*ng/mL 
                 951 
               
               
                 AUCINF 
                 hr*ng/mL 
                 1033 
               
               
                   
               
            
           
           
               
            
               
                 Individual and mean lymph node concentration-time data of  
               
               
                 INTERMEDIATE C4 after a PO dose of 3 mg/kg in male  
               
               
                 Wistar Han rat 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Sampling 
                 Concentration 
                   
               
               
                 Dose 
                 Dose 
                 time 
                 (ng/g) 
                 Mean 
               
               
                 (mg/kg) 
                 route 
                 (hr) 
                 individual 
                 (ng/g) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 3 
                 PO 
                 1 
                 117 
                 80.4 
                 98.7 
               
               
                   
                   
                 4 
                 35.9 
                 55.4 
                 45.7 
               
               
                   
                   
                 8 
                 11.9 
                 BQL 
                 11.9 
               
               
                   
                   
                 24 
                 BQL 
                 BQL 
                 BQL 
               
            
           
           
               
               
               
            
               
                   
                   
                 Lymph node to plasma ratio 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 1 
                 0.333 
                 0.254 
                 0.293 
               
               
                   
                   
                 4 
                 0.526 
                 0.905 
                 0.716 
               
               
                   
                   
                 8 
                 0.353 
                 NA 
                 0.353 
               
               
                   
                   
                 24 
                 NA 
                 NA 
                 NA 
               
            
           
           
               
               
               
            
               
                 AUClast 
                 hr*ng/mL 
                 381 
               
               
                 AUClimph node / 
                 % 
                 40.1 
               
            
           
           
               
               
               
               
               
            
               
                 AUCplasma 
                   
                   
                   
                   
               
               
                   
               
            
           
           
               
            
               
                 Individual and mean liver concentration-time data of  
               
               
                 INTERMEDIATE C4 after a PO dose of 3 mg/kg in male  
               
               
                 Wistar Han rat 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Sampling 
                 Concentration 
                   
               
               
                 Dose 
                 Dose 
                 time 
                 (ng/g) 
                 Mean 
               
               
                 (mg/kg) 
                 route 
                 (hr) 
                 individual 
                 (ng/g) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 3 
                 PO 
                 1 
                 3690 
                 2570 
                 3130 
               
               
                   
                   
                 4 
                 868 
                 898 
                 883 
               
               
                   
                   
                 8 
                 540 
                 299 
                 420 
               
               
                   
                   
                 24 
                 BQL 
                 BQL 
                 BQL 
               
            
           
           
               
               
               
            
               
                   
                   
                 Liver to plasma ratio 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 1 
                 10.5 
                 8.11 
                 9.31 
               
               
                   
                   
                 4 
                 12.7 
                 14.7 
                 13.7 
               
               
                   
                   
                 8 
                 16.0 
                 13.2 
                 14.6 
               
               
                   
                   
                 24 
                 NA 
                 NA 
                 NA 
               
            
           
           
               
               
               
            
               
                 AUClast 
                 hr*ng/mL 
                 10190 
               
               
                 AUCliver/ 
                 % 
                 1072 
               
               
                 AUCplasma 
               
               
                   
               
            
           
           
               
            
               
                 Individual and mean spleen concentration-time data of  
               
               
                 INTERMEDIATE C4 after a PO dose of 3 mg/kg in male  
               
               
                 Wistar Han rat 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Sampling 
                 Concentration 
                   
               
               
                 Dose 
                 Dose 
                 time 
                 (ng/g) 
                 Mean 
               
               
                 (mg/kg) 
                 route 
                 (hr) 
                 individual 
                 (ng/g) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 3 
                 PO 
                 1 
                 65.3 
                 62.4 
                 63.9 
               
               
                   
                   
                 4 
                 19.3 
                 20.4 
                 19.9 
               
               
                   
                   
                 8 
                 BQL 
                 BQL 
                 BQL 
               
               
                   
                   
                 24 
                 BQL 
                 BQL 
                 BQL 
               
            
           
           
               
               
               
            
               
                   
                   
                 Spleen to plasma ratio 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 1 
                 0.186 
                 0.197 
                 0.191 
               
               
                   
                   
                 4 
                 0.283 
                 0.333 
                 0.308 
               
               
                   
                   
                 8 
                 NA 
                 NA 
                 NA 
               
               
                   
                   
                 24 
                 NA 
                 NA 
                 NA 
               
            
           
           
               
               
               
            
               
                 AUClast 
                 hr*ng/mL 
                 157 
               
               
                 AUCspleen/ 
                 % 
                 16.6 
               
               
                 AUCplasma 
               
               
                   
               
            
           
         
       
     
     Prodrug PO PK Study in Rat 
       
                                Individual and mean plasma concentration-time data of EXAMPLE       7(prodrug) after a PO dose of 5 mg/kg in male Wistar Han rat                                                 Sampling   Concentration           Dose   Dose   time   (ng/mL)   Mean       (mg/kg)   route   (hr)   individual   (ng/mL)                                             5   PO   1   BQL   BQL   BQL               4   BQL   BQL   BQL               8   BQL   BQL   BQL               24   BQL   BQL   BQL                                 PK parameters   Unit   Mean               Tmax   hr   NA       Cmax   ng/mL   NA       Terminal t1 /2     hr   NA       Regression   hr   NA       Points               AUClast   hr*ng/mL   NA       AUCINF   hr*ng/mL   NA                         Individual and mean plasma concentration-time data of        INTERMEDIATE C4(parent drug) after a PO dose of 5 mg/kg        EXAMPLE 7 (prodrug) in male Wistar Han rat                                                 Sampling   Concentration   Mean       Dose   Dose   time   (ng/mL)   (ng/mL)       (mg/kg)   route   (hr)   individual                                             5   PO   1   196   229   213               4   72.5   29.4   51.0               8   16.4   13.1   14.8               24   BQL   BQL   BQL                                 PK parameters   Unit   Mean               Tmax   hr   1.00       Cmax   ng/mL   213       Terminal t1 /2     hr   1.84       Regression   hr   1~8       Points               AUClast   hr*ng/mL   633       AUCINF   hr*ng/mL   672                         Individual and mean liver concentration-time data of EXAMPLE 7       (prodrug) after a PO dose of 5 mg/kg in male Wistar Han rat                                         Sampling   Concentration           Dose   Dose   time   (ng/g)   Mean       (mg/kg)   route   (hr)   individual   (ng/g)                                             5   PO   1   BQL   BQL   BQL               4   BQL   BQL   BQL               8   BQL   BQL   BQL               24   BQL   BQL   BQL                                 Liver to plasma ratio                                             1   NA   NA   NA               4   NA   NA   NA               8   NA   NA   NA               24   NA   NA   NA                         AUClast   hr*ng/mL   NA       AUCliver/   %   NA       AUCplasma                                 Individual and mean liver concentration-time data of INTERMEDIATE        C4(parent drug) after a PO dose of 5 mg/kg EXAMPLE 7 (prodrug) in        male Wistar Han rat                                         Sampling   Concentration           Dose   Dose   time   (ng/g)   Mean       (mg/kg)   route   (hr)   individual   (ng/g)                                             5   PO   1   2180   3790   2985               4   1080   527   804               8   235   216   226               24   BQL   BQL   BQL                                 Liver to plasma ratio                                             1   11.1   16.6   13.8               4   14.9   17.9   16.4               8   14.3   16.5   15.4               24   NA   NA   NA                         AUClast   hr*ng/mL   9233       AUCliver/   %   1459       AUCplasma                                 Individual and mean lymph node concentration-time data of        EXAMPLE 7 (prodrug) after a PO dose of 5 mg/kg example 7        in male Wistar Han rat                                         Sampling   Concentration           Dose   Dose   time   (ng/g)   Mean       (mg/kg)   route   (hr)   individual   (ng/g)                                             5   PO   1   BQL   BQL   BQL               4   BQL   BQL   BQL               8   BQL   BQL   BQL               24   BQL   BQL   BQL                                 Lymph node to plasma ratio                                             1   NA   NA   NA               4   NA   NA   NA               8   NA   NA   NA               24   NA   NA   NA                         AUC last     hr*ng/mL   NA       AUC limphnode /   %   NA                                 AUCplasma                                         Individual and mean lymph node concentration-time data of       INTERMEDIATE C4 (parent drug) after a PO dose of 5 mg/kg        EXAMPLE 7 (prodrug) in male Wistar Han rat                                         Sampling   Concentration           Dose   Dose   time   (ng/g)   Mean       (mg/kg)   route   (hr)   individual   (ng/g)                                             5   PO   1   928   685   807               4   84.4   63.1   73.8               8   16.3   6.17   11.2               24   BQL   BQL   BQL                                 Lymph node to plasma ratio                                             1   4.73   2.99   3.86               4   1.16   2.15   1.66               8   0.994   NA   0.994               24   NA   NA   NA                         AUC last     hr*ng/mL   1894       AUC limphnode /   %   299                                 AUCplasma                                         Individual and mean spleen concentration-time data of       EXAMPLE 7 (prodrug) after a PO dose of 5 mg/kg example       7 in male Wistar Han rat                                         Sampling   Concentration           Dose   Dose   time   (ng/g)   Mean       (mg/kg)   route   (hr)   individual   (ng/g)                                             5   PO   1   BQL   BQL   BQL               4   BQL   BQL   BQL               8   BQL   BQL   BQL               24   BQL   BQL   BQL                                 Spleen to plasma ratio                                             1   NA   NA   NA               4   NA   NA   NA               8   NA   NA   NA               24   NA   NA   NA                         AUC last     hr*ng/mL   NA       AUC spleen /   %   NA       AUCplasma                                 Individual and mean spleen concentration-time data of       INTERMEDIATE C4 (parent drug) after a PO dose of 5       mg/kg EXAMPLE 7 (prodrug) in male Wistar Han rat                                         Sampling   Concentration           Dose   Dose   time   (ng/g)   Mean       (mg/kg)   route   (hr)   individual   (ng/g)                                             5   PO   1   175   155   165               4   23.1   7.65   15.4               8   BQL   BQL   BQL               24   BQL   BQL   BQL                                 Spleen to plasma ratio                                             1   0.893    0.677   0.785               4   0.319    0.260   0.289               8   NA   NA   NA               24   NA   NA   NA                         AUC last     hr*ng/mL   353       AUC spleen /   %   55.8       AUCplasma                            
Tissue Distribution of drug INTERMEDIATE C4 from oral dosing and of INTERMEDIATE C4 from oral dosing of prodrug EXAMPLE 7 in rats-summary