Exhibit 10.10

CONFIDENTIAL TREATMENT REQUESTED

Redacted portions are indicated by [****]

Redacted portions filed separately

with Confidential Treatment Application.

FIRST AMENDMENT TO

STOCK PURCHASE AGREEMENT

THIS FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT (this “Amendment”) is effective
as of April 13, 2012 and amends that certain Stock Purchase Agreement, dated as
of February 4, 2010 (the “Agreement”), by and among BioMarin Pharmaceutical
Inc., a Delaware corporation (the “Buyer”), LEAD Therapeutics, Inc., a Delaware
corporation (the “Company”), the parties listed on Schedule A to the Agreement
(each a “Seller” and collectively the “Sellers”) and Arthur Pappas, acting in
his capacity as Equityholder Representative in connection with the transactions
contemplated by the Agreement (the “Equityholder Representative”). (Hereafter,
Buyer, the Company, each Seller and the Equityholder Representative shall
sometimes be referred to as the “Parties”).

RECITALS

A. WHEREAS, pursuant to the Agreement, the Sellers sold, assigned, transferred
and delivered to the Purchaser, and the Purchaser purchased and acquired from
the Sellers, all right, title and interest in and to all of the issued and
outstanding shares of capital stock of the Company;

B. WHEREAS, pursuant to Section 11.4 of the Agreement, the Agreement may not be
amended, modified or supplemented except by written agreement between the
Parties; and

C. WHEREAS, the Parties desire to modify the Agreement as set forth in this
Amendment.

NOW, THEREFORE, in consideration of the foregoing, the parties hereto hereby
agree as follows:

1. Each of the defined terms set forth below and in Section 1.1 of the Agreement
shall be deleted in their entirety and replace with the following new defined
terms:

“Milestone Payment Amounts” means the First PARP Subsequent Payment Amount, if
any, the Second PARP Subsequent Payment Amount, if any, the Third PARP
Subsequent Payment Amount, if any, the Fourth PARP Subsequent Payment Amount, if
any, each Non-PARP Phase 2 Payment Amount, if any, each Non-PARP Phase 3 Payment
Amount, if any, each Non-PARP Sublicensing Payment Amount, if any, the Dose
Escalation Study Subsequent Payment Amount, if any, and the Non-PARP
Sublicensing Clinical Payment Amount, if any.

 

[***]=Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 24b-2 of the Securities Exchange Act of 1934, as
amended.

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“Non-PARP Phase 2 Milestone” means [****]

“Non-PARP Phase 2 Payment Amount” means [****]

“Non-PARP Phase 3 Milestone” means [****]

“Non-PARP Phase 3 Payment Amount” means [****]

“Non-PARP Sublicensing Payment Amount” means [****]

“Non-PARP Sublicensing Payment Date” means the fifteenth (15th) Business Day
following the Buyer’s receipt of the Future Payment Allocation Schedule relating
to the distribution to Equityholders of any Non-PARP Sublicensing Payment Amount
in accordance with Section 2.1(l).

2. The following new defined terms shall be added to Section 1.1 of the
Agreement:

“Non-PARP Sublicensing Clinical Milestone” means [****]

“Non-PARP Sublicensing Clinical Payment Amount” means [****]

“Non-PARP Sublicensing Clinical Payment Date” means the fifteenth
(15th) Business Day following the Buyer’s receipt of the Future Payment
Allocation Schedule relating to the distribution to Equityholders of any
Non-PARP Sublicensing Clinical Payment Amount in accordance with Section 2.1(n).

3. Subsection (m) of Section 2.1 of the Agreement shall be deleted and replaced
with the subsection (m) set forth below and the following new subsection
(n) shall be added at the end of Section 2.1 of the Agreement:

(m) the Dose Escalation Study Subsequent Payment Amount, if any, payable on the
Dose Escalation Study Subsequent Payment Date (with the portion of the Dose
Escalation Study Subsequent Payment Amount that is payable to each Equityholder
determined as set forth on a Future Payment Allocation Schedule related to the
Dose Escalation Study Subsequent Payment Amount); plus

(n) the Non-PARP Sublicensing Clinical Payment Amount, if any, payable on the
Non-PARP Sublicensing Clinical Payment Date (with the portion of each Non-PARP
Sublicensing Clinical Payment Amount that is payable to each Equityholder
determined as set forth on a Future Payment Allocation Schedule related to such
Non-PARP Sublicensing Clinical Payment Amount).

4. Capitalized terms used in this Amendment but not otherwise defined herein
shall have the meanings set forth in the Agreement.

5. Except as expressly set forth in this Amendment, all other terms of the
Agreement shall remain in full force and effect and once this Amendment is
executed by the parties hereto, all references in the Agreement to “the
Agreement” or “this Agreement,” as applicable, shall refer to the Agreement, as
modified by this Amendment.

 

[***]=Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 24b-2 of the Securities Exchange Act of 1934, as
amended.

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8. This Amendment shall be construed, interpreted and the rights of the Parties
determined in accordance with the laws of the State of Delaware, as applied to
agreements among Delaware residents entered into and wholly to be performed
within the State of Delaware (without reference to any choice of law rules that
would require the application of the laws of any other jurisdiction).

9. This Amendment will apply to, be binding in all respects upon and inure to
the benefit of the successors and permitted assigns of the parties.

10. This Amendment may be executed in several counterparts, each of which shall
be deemed an original and all of which shall constitute one and the same
instrument, and shall become effective when counterparts have been signed by
each of the parties and delivered to the other parties; it being understood that
all parties need not sign the same counterparts. The exchange of copies of this
Amendment and of signature pages by facsimile transmission (whether directly
from one facsimile device to another by means of a dial-up connection or whether
mediated by the worldwide web), by electronic mail in “portable document format”
(“.pdf”) form, or by any other electronic means intended to preserve the
original graphic and pictorial appearance of a document, or by combination of
such means, shall constitute effective execution and delivery of this Amendment
as to the parties and may be used in lieu of the original Amendment for all
purposes. Signatures of the parties transmitted by facsimile or other electronic
means shall be deemed to be their original signatures for all purposes.

[Signature Page Follows]

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IN WITNESS WHEREOF, the parties hereto have executed and delivered this
Amendment as of the date first above written.

 

BIOMARIN PHARMACEUTICAL INC. By:   /S/ G. Eric Davis   Name: G. Eric Davis  
Title: S.V.P., General Counsel

 

LEAD THERAPEUTICS, INC. By:   /S/ G. Eric Davis   Name: G. Eric Davis   Title:
Vice President

 

EQUITYHOLDER REPRESENTATIVE: By:   /S/_Arthur Pappas   Arthur Pappas, as
Equityholder Representative

 

SIGNATURE PAGE TO FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT

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SELLERS   PROQUEST INVESTMENTS IV, L.P.

By:

  ProQuest Associates IV LLC, its General Partner

By:

  /S/ Pasquale DeAngelis

Name:

  Pasquale DeAngelis

Title:

  Managing Member

 

  PROQUEST MANAGEMENT LLC

By:

  /S/ Pasquale DeAngelis

Name:

  Pasquale DeAngelis

Title:

  Chief Financial Officer and Administrative Partner

 

SIGNATURE PAGE TO FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT

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SELLERS   A. M. PAPPAS LIFE SCIENCE VENTURES III, LP

By:

  AMP&A Management III, LLC, its General Partner

By:

  /S/ Ford S. Worthy

Name:

  Ford S. Worthy

Title:

  Partner

 

  PV III CEO FUND, LP

By:

  AMP&A Management III, LLC, its General Partner

By:

  /S/ Ford S. Worthy

Name:

  Ford S. Worthy

Title:

  Partner

 

SIGNATURE PAGE TO FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT

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SELLERS   MUSTANG VENTURES I, L.P.

By:

 

By:

  /S/ Robert C. McCormack, Jr.

Name:

  Robert C. McCormack, Jr.

Title:

  Managing Director

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SELLERS CHINA GATEWAY LIFE SCIENCE (HOLDINGS) LTD. (HK) Print Name:     Michael
Hui Title:     CEO Signature:     /S/ Michael Hui

Address:

Attn: Mr. Michael Hui

Chief Executive Officer

No. 3 Building, 720 Cailun Road

Zhangjiang High Tech Park, Pu Dong New Area

Shanghai China

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SELLERS

/S/ Sofie Qiao

Shuang (Sofie) Qiao

/S/ Leonard Post

Leonard Post

/S/ Peter Myers

Peter Myers

/S/ Daniel Chu

Daniel Chu

/S/ Charles Hsu

Charles Hsu

/S/ Zhengying Pan

Zhengying Pan

/S/ Xiaoyi Xiao

Xiaoyi Xiao

/S/ David Hanabusa

David Hanabusa