Exhibit 10.21

CONSENT, WAIVER AND AMENDMENT AGREEMENT

This Consent, Waiver and Amendment Agreement (this “Agreement”), entered into as
of March 28, 2013, is made by and among La Jolla Pharmaceutical Company, a
California corporation (the “Company”), and the undersigned holders of the
Company’s Preferred Stock (defined below) (each a “Holder” and collectively the
“Holders”).

WHEREAS, the Company and the Holders entered into a Securities Purchase
Agreement dated as of May 24, 2010 (the “Securities Purchase Agreement”);

WHEREAS, the Company and the Holders entered into a Consent and Amendment
Agreement dated as of March 29, 2011 (the “Consent and Amendment Agreement”),
amending certain of the rights and obligations of the parties arising under the
Securities Purchase Agreement;

WHEREAS, the Company and the Holders entered into an Amendment Agreement dated
as of June 30, 2011 (the “First Amendment Agreement”), amending certain of the
rights and obligations of the parties arising under the Securities Purchase
Agreement and the certificate of designations under which the preferred stock
held by the Holders was designated and issued (the “Prior Certificate of
Designations”);

WHEREAS, the Company and the Holders entered into an Amendment Agreement dated
as of August 24, 2011 (the “Second Amendment Agreement”), amending certain of
the rights and obligations of the parties arising under the Securities Purchase
Agreement and the Prior Certificate of Designations;

WHEREAS, the Company and the Holders entered into a Consent and Amendment
Agreement dated as of January 19, 2012 (the “Third Amendment Agreement”),
amending certain of the rights and obligations of the parties arising under the
Securities Purchase Agreement, approving the entry into the Asset Purchase
Agreement (as defined in the Third Amendment Agreement) between the Company and
Solana Therapeutics, Inc. and approving the adoption of a “New Certificate of
Designations” (as defined in the Third Amendment Agreement);

WHEREAS, subsequent to the closing of the transactions contemplated under the
Asset Purchase Agreement, the Company changed its corporate domicile from
Delaware to California, whereupon the Company filed Articles of Incorporation
with the California Secretary of State (the “Articles of Incorporation”), which
effectively replaced the New Certificate of Designations and established the
rights, preferences and privileges of the following series of preferred stock,
which, upon effectiveness of the Articles of Incorporation, was and is currently
the preferred stock held by the Holders: Series C-12 Convertible Preferred Stock
(the “Series C-12 Preferred”); Series C-22 Convertible Preferred Stock (the
“Series C-22 Preferred” and, together with the Series C-12 Preferred the “Series
C Preferred”); Series D-12 Convertible Preferred Stock (the “Series D-12
Preferred”); and Series D-22 Convertible Preferred Stock (the “Series D-22
Preferred” and, together with the Series D-12 Preferred, the “Series D
Preferred,” and the Series C Preferred, together with the Series D Preferred,
the “Preferred Stock”);

WHEREAS, the Company and the Holders entered into a Consent and Waiver
Agreement, dated as of December 7, 2012 (the “Fourth Amendment Agreement”),
whereby the Holders waived certain rights arising under the Articles of
Incorporation;

--------------------------------------------------------------------------------

WHEREAS, the Holders currently own warrants to purchase “Units,” with each Unit
consisting of: (i) one share Series C-22 Preferred; and (ii) a warrant to
purchase one share of Series D-22 Preferred (the “Series C-22 Warrants”);

WHEREAS, the Holders wish to waive certain other rights arising under the
Articles of Incorporation and also wish to amend the Series C-22 Warrants, with
such waiver and amendment being effective as of December 31, 2012, as set forth
below;

WHEREAS, the undersigned Holders represent the required threshold to effect such
a waiver under the Articles of Incorporation and to amend the Series C-22
Warrants; and

WHEREAS, the undersigned Holders wish to exercise a portion of the Series C-22
Warrants, as amended pursuant to this Agreement, with such exercise being
effective as of December 31, 2012.

NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained in this Agreement, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

1. Capitalized Terms. Capitalized terms used and not otherwise defined herein
shall have the meanings ascribed to such terms in the Fourth Amendment
Agreement.

2. Representations and Warranties of the Holders. Each of the Holders hereby
represents and warrants to the Company that, with respect solely to itself and
not with respect to any other Holder, each Holder has the requisite power and
authority to enter into the Agreement, and if the Holder is an entity, such
Holder is a corporation, limited liability company or partnership duly
incorporated or organized, validly existing and in good standing under the laws
of the jurisdiction of its incorporation or organization.

3. Waiver of Certain Rights. The Holders, constituting the Requisite Holders
under the Articles of Incorporation, hereby consent to the following actions and
hereby irrevocably waive the following rights arising under the Articles of
Incorporation, with such waiver being effective as of December 31, 2012:

(a) Pursuant to Article IV(d)(6)(E)(iii) of the Articles of Incorporation, the
holders of the Series C Preferred hereby irrevocably waive the provisions set
forth under Article IV(d)(6) of the Articles of Incorporation and, accordingly,
Article IV(d)(6) of the Articles of Incorporation shall hereafter be of no force
or effect.

(b) In light of the waiver of the provisions set forth under Article IV(d)(6) of
the Articles of Incorporation, pursuant to Article IV(d)(13)(G) of the Articles
of Incorporation, the Requisite Holders hereby irrevocably waive the provisions
set forth under Article IV(d)(9)(E) of the Articles of Incorporation.

(c) In light of the waiver of the provisions set forth under Article IV(d)(6) of
the Articles of Incorporation, pursuant to Article IV(d)(13)(G) of the Articles
of Incorporation, the Requisite Holders hereby irrevocably waive the provisions
set forth under Article IV(d)(9)(F) of the Articles of Incorporation.

 

-2-

--------------------------------------------------------------------------------

4. Amendment of Series C-22 Warrants. The Company and the Holders each
acknowledge and agree that the Series C-22 Warrants have previously been amended
such that, although the warrant refers to Series C-2 Preferred Stock, the term
Series C-2 Preferred Stock has been replaced with Series C-22 Preferred, and
nothing in this amendment, including referencing Series C-2 Preferred Stock
shall change the fact that Series C-2 Preferred Stock actually means Series C-22
Preferred. The Company and each Holder hereby agree to amend each of the Series
C-22 Warrants held by such Holders, with such amendment being effective as of
December 31, 2012, as follows:

(a) The first paragraph of the Series C-22 Warrant (appearing immediately prior
to Section 1 of the Series C-22 Warrants) held by each Holder shall be amended
and restated as follows:

“THIS SERIES C-2 PREFERRED STOCK PURCHASE WARRANT (the “Warrant”) certifies
that, for value received, [the Holder] (the “Holder”) is entitled, upon the
terms and subject to the limitations on exercise and the conditions hereinafter
set forth, at any time on or after the Issue Date set forth above and on or
prior to the close of business on January 19, 2015 (the “Termination Date”) but
not thereafter, to subscribe for and purchase from La Jolla Pharmaceutical
Company, a California corporation (the “Company”), up to [            ] shares
(the “Warrant Shares”) of the Company’s Series C-2 Preferred Stock (the “Series
C-2 Preferred Stock”). The purchase price of one share of the Series C-2
Preferred Stock shall be equal to the Exercise Price, as defined in
Section 1(b). This Warrant is one of a series of warrants of like tenor issuable
by the Company under that certain Securities Purchase Agreement by and among the
Company and the Purchasers named therein, dated as of May 24, 2010 (the
“Purchase Agreement”) and referred to therein as the Cash Warrants. As used
herein, “Warrants” means all such Cash Warrants.”

(b) Section 1(a) shall be amended and restated as follows:

“(a) Exercise of Warrant. Exercise of the purchase rights represented by this
Warrant may be made, in whole or in part, at any time or times on or after the
Issue Date and on or before the Termination Date by delivery to the Company (the
date of such delivery, the “Exercise Date”) of both: (i) a duly executed
electronic mail copy of the Notice of Exercise annexed hereto (or such other
office or agency of the Company as it may designate by notice in writing to the
registered Holder at the address of the Holder appearing on the books of the
Company); and (ii) sufficient funds representing the Exercise Price, delivered
by wire transfer. Notwithstanding anything herein to the contrary, the Holder
shall not be required to physically surrender this Warrant to the Company until
the Holder has purchased all of the Warrant Shares available hereunder and the
Warrant has been exercised in full, in which case, the Holder shall surrender
this Warrant to the Company for cancellation within three (3) Trading Days (as
defined in the Certificate of Designations, Preferences and Rights of Series C-1
Convertible Preferred Stock, Series C-2 Convertible Preferred Stock, Series D-1
Convertible Preferred Stock and Series D-2 Convertible Preferred Stock of the
Company (the “Certificate of Designations”)) of the date the final Notice of
Exercise is delivered to the Company.

 

-3-

--------------------------------------------------------------------------------

Partial exercises of this Warrant resulting in purchases of a portion of the
total number of Warrant Shares available hereunder shall have the effect of
lowering the outstanding number of Warrant Shares purchasable hereunder in an
amount equal to the applicable number of Warrant Shares purchased. The Holder
and the Company shall maintain records showing the number of Warrant Shares
purchased and the date of such purchases. The Company shall deliver any
objection to any Notice of Exercise within two (2) Trading Days of receipt of
such notice. In the event of any dispute or discrepancy, the records of the
Holder shall be controlling and determinative in the absence of manifest error.
The Holder may provide this Warrant, or an affidavit of lost security, to the
Company within a reasonable period after the delivery of any Notice of Exercise
related to any partial exercise of this Warrant, and the Company, at its
expense, will promptly thereafter issue and deliver to the Holder a new Warrant
of like tenor, registered in the name of the Holder and exercisable, in the
aggregate, for the remaining Warrant Shares available for purchase under this
Warrant. The Holder and any assignee, by acceptance of this Warrant, acknowledge
and agree that, by reason of the provisions of this paragraph, following the
purchase of a portion of the Warrant Shares hereunder, the number of Warrant
Shares available for purchase hereunder at any given time may be less than the
amount stated on the face hereof.”

(c) Section 1(b) shall be amended and restated as follows:

“(b) Exercise Price. The exercise price of the Warrant Shares under this Warrant
shall be $1,000.00 per share, subject to adjustment hereunder (the “Exercise
Price”).”

(d) Section 1(c) shall be deleted in its entirety and replaced with the
following: “Reserved.”

(e) Section 1(e)(ii) shall be deleted in its entirety and replaced with the
following: “Reserved.”

(f) Section 1(e)(iv) shall be amended and restated as follows:

“(iv) Rescission Rights. If the Company fails to cause its transfer agent to
transmit to the Holder a certificate or certificates representing the Warrant
Shares pursuant to this Section 1(e) by the third (3rd) Trading Day immediately
following the Warrant Share Delivery Date and the payment of the Exercise Price,
then the Holder will have the right to rescind such exercise at any time until
delivery of such securities.”

(g) Section 1(e)(vi) shall be amended and restated as follows:

“(vi) Charges, Taxes and Expenses. Issuance of certificates for Warrant Shares
shall be made without charge to the Holder for any issue or transfer tax or
other incidental expense in respect of the issuance of such certificate, all of
which taxes and expenses shall be paid by the Company, and such certificates
shall be issued in the name of the Holder or in such name or names as may be
directed by the Holder; provided, however, that in the event certificates for
Warrant Shares are to be issued in a name other than the name of the Holder,
this Warrant when surrendered for exercise shall be accompanied by the
Assignment Form attached hereto duly executed by the Holder; and the Company may
require, as a condition thereto, the payment of a sum sufficient to reimburse it
for any transfer tax incidental thereto.”

 

-4-

--------------------------------------------------------------------------------

(h) Section 3(a) shall be amended and restated as follows:

“(a) Transferability. Subject to compliance with any applicable securities laws,
the conditions set forth in Section 3(d) hereof and the conditions set forth in
the Purchase Agreement, this Warrant and all rights hereunder are transferable,
in whole (not in part), upon surrender of this Warrant at the principal office
of the Company or its designated agent, together with a written assignment of
this Warrant substantially in the form attached hereto duly executed by the
Holder or its agent or attorney and funds sufficient to pay any transfer taxes
payable upon the making of such transfer. Upon such surrender and, if required,
such payment, the Company shall execute and deliver a new Warrant or Warrants in
the name of the assignee or assignees and in the denomination or denominations
specified in such instrument of assignment and this Warrant shall promptly be
cancelled. A Warrant, if properly assigned, may be exercised by a new holder for
the purchase of Warrant Shares without having a new Warrant issued.”

(i) Section 3(b) shall be amended and restated as follows:

“(b) New Warrants. This Warrant may be divided or combined with other Warrants
upon presentation hereof at the aforesaid office of the Company, together with a
written notice specifying the names and denominations in which new Warrants are
to be issued, signed by the Holder or its agent or attorney. Subject to
compliance with Section 3(a), as to any transfer which may be involved in such
division or combination, the Company shall execute and deliver a new Warrant or
Warrants in exchange for the Warrant or Warrants to be divided or combined in
accordance with such notice. All Warrants issued on transfers or exchanges shall
be dated the original Issue Date and shall be identical with this Warrant except
as to the number of Warrant Shares issuable pursuant thereto.”

(j) Section 5(a) shall be amended and restated as follows:

“(a) No Rights as Stockholder Until Exercise. This Warrant does not entitle the
Holder to any voting rights or other rights as a stockholder of the Company
prior to the exercise hereof. Upon the surrender of this Warrant and the payment
of the aggregate Exercise Price, the Warrant Shares so purchased shall be and be
deemed to be issued to such Holder as the record owner of such shares as of the
close of business on the later of the date of such surrender and payment.”

 

-5-

--------------------------------------------------------------------------------

(k) The first paragraph of Section 5(d) shall be amended and restated as
follows:

“The Company covenants that its issuance of this Warrant shall constitute full
authority to its officers who are charged with the duty of executing stock
certificates to execute and issue the necessary certificates for the Warrant
Shares upon the exercise of the purchase rights under this Warrant. The Company
will take all such reasonable action as may be necessary to assure that all
Warrant Shares shall be issued as provided herein without violation of any
applicable law or regulation, or of any requirements of the Trading Market (as
defined in the Certificate of Designations). The Company covenants that all
Warrant Shares that are required to be issued upon the exercise of the purchase
rights represented by this Warrant will, upon exercise of the purchase rights
represented by this Warrant, be duly authorized, validly issued, fully paid and
nonassessable and free from all taxes, liens and charges created by the Company
in respect of the issue thereof (other than taxes in respect of any transfer
occurring contemporaneously with such issue).”

(l) Section 5(l) shall be amended and restated as follows:

“(l) Amendment; Waiver. No provision of this Warrant may be waived or amended on
behalf of all holders of Warrants other than by a written instrument signed by
the Company and the holders of Warrants entitling such holders to acquire at
least 80% of the shares of Series C-2 Preferred Stock of the Company that may be
acquired upon exercise in full of all then outstanding Warrants. In addition to
the foregoing, no provision of this Warrant may be amended to increase the
financial obligations of Holder under this Warrant other than by a written
instrument signed by Holder. Nothing provided in this Section 5(l) shall limit
an individual holder’s right to waive or amend any provision of any Warrant on
its own behalf. The Holder acknowledges that any amendment or waiver effected in
accordance with this Section 5(l) shall be binding upon the Holder (and its
permitted assigns) and the Company, including, without limitation, an amendment
or waiver that is not agreed to by the Holder or that has an adverse effect on
any or all holders of Warrants.”

5. Exercise of Series C-22 Warrants. Each Holder hereby agrees to exercise,
effective December 31, 2012, a portion of the Series C-22 Warrant held by such
Holder as set forth on Schedule A hereto. The signing of this Agreement shall
constitute the exercise of such Series C-22 Warrants and no exercise notice
shall need to be sent to the Company to exercise such Series C-22 Warrants, as
this Agreement shall constitute such notice. The Holders further agree to
transfer to the Company the Exercise Price for each such Holder’s partial
exercise of the Series C-22 Warrants, which such amounts of the aggregate
Exercise Price for each Holder is set forth on Schedule A hereto, no later
March 27, 2013.

6. Entire Agreement; Amendment. This Agreement contains the entire understanding
and agreement of the parties with respect to the matters covered hereby and,
except as specifically set forth herein, neither the Company nor any Holder make
any representation, warranty, covenant or undertaking with respect to such
matters, and they supersede all prior understandings and agreements with respect
to said subject matter, all of which are merged herein. No provision of this
Agreement may be waived or amended on behalf of all Holders other than by a
written instrument signed by the Company and the Requisite Holders. In addition
to the foregoing, no provision of this Agreement may be amended to increase the
financial obligations of any Holder under this Agreement other than by a written
instrument signed by such Holder. Nothing provided in this Section 6 shall limit
an individual Holder’s right to waive or amend any provision of this Agreement
on its own behalf. The Holders acknowledge that any waiver effected in
accordance with this Section 6 shall be binding upon each Holder (and their
permitted assigns) and the Company, including, without limitation, a waiver that
has an adverse effect on any or all Holders.

 

-6-

--------------------------------------------------------------------------------

7. Notices. Any notice, demand, request, waiver or other communication required
or permitted to be given hereunder shall be in writing and shall be delivered in
the manner and to the attention of the parties as set forth in the Fourth
Amendment Agreement.

8. Waivers. No waiver by any party of any default with respect to any provision,
condition or requirement of this Agreement shall be deemed to be a continuing
waiver in the future or a waiver of any other provision, condition or
requirement hereof, nor shall any delay or omission of any party to exercise any
right hereunder in any manner impair the exercise of any such right accruing to
it thereafter.

9. Headings. The article, section and subsection headings in this Agreement are
for convenience only and shall not constitute a part of this Agreement for any
other purpose and shall not be deemed to limit or affect any of the provisions
hereof.

10. Successors and Assigns. This Agreement shall be binding upon and inure to
the benefit of the parties and their successors and assigns.

11. Governing Law. To the fullest extent permitted by law, this Agreement shall
be governed by and construed in accordance with the internal laws of the State
of California, without giving effect to any of the conflicts of law principles
which would result in the application of the substantive law of another
jurisdiction. This Agreement shall not be interpreted or construed with any
presumption against the party causing this Agreement to be drafted.

12. Counterparts. This Agreement may be executed in any number of counterparts,
all of which taken together shall constitute one and the same instrument and
shall become effective when counterparts have been signed by each party and
delivered to the other parties hereto, it being understood that all parties need
not sign the same counterpart.

13. Disclosure of Transaction. The Company shall, in its Annual Report on Form
10-K, describe the material terms of the transactions contemplated hereby and
thereby, with the filing of the Form 10-K and a press release to be made no
later than April 1, 2013. The Company will provide representatives from Tang
Capital Partners, LP and Boxer Capital, LLC with the opportunity to review and
approve the language describing the transactions to be used in the 10-K and
press release prior to issuance and filing, respectively, which approval will
not be unreasonably withheld.

14. Severability. The provisions of this Agreement are severable and, in the
event that any court of competent jurisdiction shall determine that any one or
more of the provisions or part of the provisions contained in this Agreement
shall, for any reason, be held to be invalid, illegal or unenforceable in any
respect, such invalidity, illegality or unenforceability shall not affect any
other provision or part of a provision of this Agreement and this Agreement
shall be reformed and construed as if such invalid or illegal or unenforceable
provision, or part of such provision, had never been contained herein, so that
such provisions would be valid, legal and enforceable to the maximum extent
possible.

 

-7-

--------------------------------------------------------------------------------

15. Further Assurances. From and after the date of this Agreement, upon the
request of the Holders or the Company, the Company and each Holder shall execute
and deliver such instruments, documents and other writings as may be reasonably
necessary or desirable to confirm and carry out and to effectuate fully the
intent and purposes of this Agreement.

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

 

-8-

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the parties hereto have caused this Consent, Waiver and
Amendment Agreement to be duly executed by their respective authorized officers
as of the date first above written.

 

LA JOLLA PHARMACEUTICAL COMPANY By:   /s/ George Tidmarsh   Name: George
Tidmarsh, M.D. Ph.D.   Title: President and Chief Executive Officer

[SIGNATURE PAGES CONTINUE]

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the undersigned have caused this Consent, Waiver and
Amendment Agreement to be duly executed by their respective authorized
signatories as of the date first indicated above.

 

Name of Holder: Tang Capital Partners, LP     Signature of Authorized Signatory
of Holder:   /s/ Kevin Tang   Name of Authorized Signatory: Kevin Tang     Title
of Authorized Signatory: Managing Director     Email Address of Holder:
kevin@tangcapital.com     Fax Number of Holder: 858 200 3837     Address for
Notice of Holder:     4747 Executive Drive, Suite 510     San Diego, CA 92121  
 

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the undersigned have caused this Consent, Waiver and
Amendment Agreement to be duly executed by their respective authorized
signatories as of the date first indicated above.

 

Name of Holder: The Haeyoung and Kevin Tang Foundation, Inc.   Signature of
Authorized Signatory of Holder:   /s/ Kevin Tang   Name of Authorized Signatory:
Kevin Tang     Title of Authorized Signatory: President     Email Address of
Holder: kevin@tangcapital.com     Fax Number of Holder: 858 200 3837     Address
for Notice of Holder:     4747 Executive Drive, Suite 510     San Diego, CA
92121    

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the undersigned have caused this Consent, Waiver and
Amendment Agreement to be duly executed by their respective authorized
signatories as of the date first indicated above.

 

Name of Holder: Boxer Capital, LLC     Signature of Authorized Signatory of
Holder:   /s/ Chris Fuglesang   Name of Authorized Signatory: Chris Fuglesang  
  Title of Authorized Signatory: Member     Email Address of Holder:
cfuglesang@tavistock.com     Fax Number of Holder: 858 400 3101     Address for
Notice of Holder:     440 Stevens Ave., Suite 100     Solana Beach, CA 92075    

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the undersigned have caused this Consent, Waiver and
Amendment Agreement to be duly executed by their respective authorized
signatories as of the date first indicated above.

 

Name of Holder: MVA Investors, LLC     Signature of Authorized Signatory of
Holder:   /s/ Chris Fuglesang   Name of Authorized Signatory: Chris Fuglesang  
  Title of Authorized Signatory: President     Email Address of Holder:
cfuglesang@tavistock.com     Fax Number of Holder: 858 400 3101     Address for
Notice of Holder:     440 Stevens Ave, Suite 100     Solana Beach, CA 92075    

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the undersigned have caused this Consent, Waiver and
Amendment Agreement to be duly executed by their respective authorized
signatories as of the date first indicated above.

 

Name of Holder: RTW Investments, LLC     Signature of Authorized Signatory of
Holder:   /s/ Roderick Wong   Name of Authorized Signatory: Roderick Wong    
Title of Authorized Signatory: Managing Member     Email Address of Holder:
rwong@rtwfunds.com     Fax Number of Holder: 646 597 6998     Address for Notice
of Holder:     1350 Avenue of the Americas, 28th Floor     New York, NY 10019  
 

--------------------------------------------------------------------------------

Schedule A

 

Holder

   Number of Series  C-22
Warrants to Be Exercised      Aggregate Exercise Price
of Partial Series C-22
Warrant Exercise  

Tang Capital Partners, LP

     324       $ 324,000.00   

The Haeyoung and Kevin Tang Foundation, Inc.

     15       $ 15,000.00   

Boxer Capital, LLC

     98       $ 98,000.00   

MVA Investors, LLC

     14       $ 14,000.00   

RTW Investments, LLC

     49       $ 49,000.00