Exhibit 10.3

CV Therapeutics, Inc.

requests that the marked portions of the exhibit be granted confidential
treatment

under Rule 24b-2 of the Securities Exchange Act of 1934, as amended.

AMENDMENT No. 1 TO COLLABORATION AND LICENSE AGREEMENT

This first amendment (“First Amendment”) to the Collaboration and License
Agreement is entered into as of the 12th day of June, 2007, by and between CV
Therapeutics, Inc. (“CVT”) and PTC Therapeutics, Inc. (“PTC”), with reference to
the following facts and circumstances.

WHEREAS CVT and PTC are parties to that certain Collaboration and License
Agreement dated as of June 7, 2006 (the “Agreement”);

WHEREAS, pursuant to Section 3.4 of the Agreement, the Parties have approved in
writing [*] Additional Targets;

WHEREAS, the Parties desire to modify certain terms of the Agreement with
respect to these Additional Targets, and also modify certain other terms, all as
set forth hereinbelow in this First Amendment.

NOW THEREFORE, in consideration of the premises and mutual covenants contained
in this First Amendment, the Parties agree as follows:

1. Definitions. Except as expressly set forth herein, all capitalized terms used
herein and not otherwise defined shall be as defined in the Agreement.

2. Additional Targets. Section 3.4 of the Agreement is amended to add the
following new subsections (c), (d), (e), (f), (g) and (h) as follows:

 

  “(c) Until [*] (the “Election Date”), CVT shall have the option to defer the
commencement of all research and development activity (including screening)
under the Research Plan on one or more or all of the Additional Targets (each,
an “Additional Target Deferral Option”) for up to [*] following the Election
Date (each, an “Additional Target Deferral Period”) with respect to one or more
or all of the Additional Targets. CVT shall notify PTC in writing of its
exercise of any Additional Target Deferral Option on or before the Election
Date. The exclusivity provisions of Section 3.11 of the Agreement shall continue
to apply to all Additional Targets, including any Additional Target as to which
CVT has exercised any Additional Target Deferral Option hereunder.

 

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[*] Certain information on this page has been redacted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.

 

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  (d) In the event that any research and development activity under the Research
Plan has been conducted by either Party with respect to an Additional Target
prior to exercise by CVT of an Additional Target Deferral Option with respect to
such Additional Target in accordance with Section 3.4(c), following CVT’s
written notification to PTC of CVT’s exercise of such Additional Target Deferral
Option, the Parties (acting through the JRC and JMC) shall determine in writing
the date by which all further research and discovery activity for such
Additional Target shall cease.

 

  (e) During any Additional Target Deferral Period, substitution of Targets
pursuant to Section 3.4(b) may only occur with respect to the Initial Targets or
any Additional Targets that remain active (i.e. for which CVT has not exercised
its Additional Target Deferral Option). In addition, any substitute Target(s)
must first be drawn from those Additional Targets for which CVT has exercised
its Additional Target Deferral Option and which are, at the time of the
substitution, subject to an Additional Target Deferral Period.

 

 

(f)

With respect to any Additional Target for which CVT has exercised an Additional
Target Deferral Option, CVT may elect to have research and development activity
(including screening) resume under a Research Plan to be developed for the
applicable Additional Target pursuant to Section 3.1, by providing written
notification to PCT that CVT intends to resume research and development activity
for such Additional Target. If CVT provides any such notice to PTC after the
first (1st) anniversary of the Election Date, then the provisions of
Section 3.10 shall apply except that CVT will be responsible for [*] Development
Costs incurred by or on behalf of either PTC or CVT for the applicable
Additional Target during all stages of the Research Collaboration through Lead
Identification.

 

  (g) Notwithstanding Section 3.11(a) of the Agreement, following [*] of the
Election Date, PTC may perform internal research and discovery efforts
pertaining to any Additional Target for which CVT has exercised an Additional
Target Deferral Option and which remains subject to an Additional Target
Deferral Period. In addition, following [*] of the Election Date, should PTC
receive an unsolicited inquiry from a Third Party with respect to a research and
discovery collaboration or license arrangement with respect to any Additional
Target for which CVT has exercised an Additional Target Deferral Option and
which remains subject to an Additional Target Deferral Period, if PTC is
interested in pursuing such potential Third Party

 

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[*] Certain information on this page has been redacted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.

 

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arrangement PTC shall first notify CVT in writing of PTC’s interest and request
that CVT decide whether or not to elect to resume research and development
activity pursuant to Section 3.4(f) with respect to such Additional Target. If
CVT does not respond within thirty (30) days after PTC’s written notice under
the preceding sentence with a written election to resume research and
development activity for such Additional Target under Section 3.4(f) (or if by
such thirty (30) day deadline CVT provides no response), then immediately with
respect to such Additional Target the Additional Target Deferral Period shall
end and the provisions of Section 3.4(h) shall apply.

 

  (h) If an Additional Target Deferral Period relating to a particular
Additional Target ends immediately in accordance with the last sentence of
Section 3.4(g), or ends because [*] have elapsed since the Election Date without
CVT electing to have research and development activity resume for the applicable
Additional Target pursuant to Section 3.4(f), the Parties agree that such
Additional Target shall be removed from the Research Collaboration, any and all
obligations of the Parties with respect to such Additional Target under the
Research Collaboration shall terminate, and the provisions of Section 3.11, 4.4,
and 4.6 shall no longer apply with respect to such Additional Target. In the
event of such removal of an Additional Target from the Research Collaboration,
(i) PTC shall solely own all rights, title and interest in and to any and all
Know-How and Patent Rights which were developed by or on behalf of the Parties
or their Affiliates as a result of research and development activity for such
Additional Target prior to its removal from the Research Collaboration, (ii) CVT
hereby assigns to PTC all of CVT’s rights, title and interest in such Know-How
and Patent Rights, and agrees to execute all further documents reasonably
necessary or desirable to more fully effectuate such assignment, at PTC’s sole
expense, and (iii) CVT shall have no right to use such Know-How and Patent
Rights resulting from the Parties’ research and development activities for such
Target.”

3. Amendment to Note; Subordination. CVT and PTC agree to enter into the
amendment to the Convertible Promissory Note attached as Exhibit A
simultaneously with entering into this First Amendment. In addition, CVT agrees,
if requested by PTC in writing, to negotiate in good faith with any potential
lenders to PTC with regard to the subordination of the Convertible Promissory
Note and the Promissory Note to such lenders on commercially reasonable terms.

4. No Other Modifications. In all other respects, the terms and conditions of
the Agreement shall remain unchanged and in full force and effect. In the event
of any conflict between the terms of this First Amendment and the terms of the
Agreement, the terms of this First Amendment shall govern.

 

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[*] Certain information on this page has been redacted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.

 

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IN WITNESS WHEREOF, the Parties have executed this First Amendment by their duly
authorized officers as of the date set forth above.

 

PTC THERAPEUTICS, INC.     CV THERAPEUTICS, INC. By:  

/s/ STUART PELTZ

    By:  

/s/ LOUIS G. LANGE, M.D., PH.D.

Title:   President and CEO     Title:   CEO and Chairman of the Board

 

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EXHIBIT A

Convertible Promissory Note Amendment No. 1

This Convertible Promissory Note Amendment No. 1 (the “First Amendment to Note”)
is entered into as of June 12, 2007 (the “Amendment Date”) by and between PTC
Therapeutics, Inc., a Delaware corporation (“PTC”), and CV Therapeutics, Inc., a
Delaware corporation (“CVT”), for the purpose of amending the Convertible
Promissory Note between the same parties dated June 7, 2006 (hereinafter
referred to as the “Convertible Note”), with reference to the following facts
and circumstances.

WHEREAS, PTC and CVT entered into the Convertible Note in connection with the
Collaboration and License Agreement (the “Collaboration Agreement”) dated as of
June 7th, 2006; and

WHEREAS, the parties now wish to amend the terms of Convertible Note as set
forth in this First Amendment to Note;

NOW, THEREFORE, IN consideration of the mutual covenants and conditions
contained herein, and for other good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, the Parties hereby agree as follows:

A. CVT Representations. Each Party represents and warrants that as of the
Amendment Date it has not assigned or otherwise pledged the Convertible Note and
that is has the full power and authority to enter into this First Amendment to
Note.

B. Amendment to Convertible Note. Section 1.7 of the Convertible Note is amended
and restated in its entirety as follows:

“1.7 “Maturity Date” means January 31, 2011.”

C. Remainder Unchanged. Except as expressly amended by this First Amendment to
Note, the Convertible Note shall be unchanged and shall remain in full force and
effect and in accordance with its terms. In the event of any conflict between
the terms of this First Amendment to Note and the terms of the Convertible Note,
the terms of this First Amendment to Note shall govern.

 

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IN WITNESS WHEREOF, the parties hereto have caused this First Amendment to Note
to be executed by their duly authorized officers as of the first date set forth
above.

 

PTC Therapeutics, Inc.     CV Therapeutics, Inc. By:  

 

    By:  

 

Title:  

 

    Title:  

 

Date:  

 

    Date:  

 

 

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