Document:

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                                                                    Exhibit 4.10

                             STOCK PURCHASE WARRANT

                                     For the purchase of up to 460,018 shares of
                                           Series E Convertible Preferred Stock,
                                                       par value $.001 per share

No. W-TCC-02E                                                     April 21, 2004

PTC Therapeutics, Inc., a Delaware corporation (the "Company"), hereby certifies
that, for good and valuable consideration, Three Crowns Capital (Bermuda) Ltd.
or its permitted assigns (the "Warrant Holder") is entitled, subject to the
terms set forth below, to purchase from the Company at any time on or before
5:00 p.m., Boston, Massachusetts time, on April 21, 2014 (the "Exercise
Period"), up to 460,018 fully-paid and non-assessable shares of Series E
Convertible Preferred Stock, par value $.001 per share, of the Company (the
"Series E Preferred Stock"), or shares of the Common Stock, par value $.001 per
share, of the Company (the "Common Stock") upon a mandatory conversion of the
Series E Preferred Stock as provided in Section 3 hereof (the Series E Preferred
Stock and the Common Stock are hereinafter collectively referred to as
"Shares"), at a price per share (the "Exercise Price") which shall initially be
$0.397644 per share and which shall be subject to adjustment as herein provided.

     1. Exercise of Warrants.

     1.1. Exercise. Subject to the terms and conditions of this Warrant, this
Warrant shall become exercisable by the Warrant Holder on April 21, 2004.

     1.2. Procedure to Exercise. This Warrant may be exercised by the Warrant
Holder, in whole or in part, by surrendering this Warrant, with the purchase
form appended hereto as Exhibit A duly executed by such Warrant Holder or by
such Warrant Holder's duly authorized attorney, at the principal office of the
Company, or at such other office or agency as the Company may designate,
accompanied by payment in full by cash, check or wire transfer of the amount
obtained by multiplying the number of Shares in the notice of exercise by the
Exercise Price (the "Purchase Price").

     1.3. Net Issue Exercise. In lieu of exercising this Warrant in the manner
provided above in Section 1.2, the Warrant Holder may elect to receive shares
equal to the value of this Warrant (or the portion thereof being converted) by
surrender of this Warrant, in whole or in part, at the principal office of the
Company together with the notice of exercise attached hereto as Exhibit A, in
which event the Company shall issue to the Warrant Holder the number of Shares
computed using the following formula (a "Net Issue Exercise"):

                                  X = Y (A - B)
                                      ---------
                                          A

Where: X = The number of Shares to be issued to the Warrant Holder.

       Y = The number of Shares purchasable under this Warrant (at the date of

                                      A-1

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           such calculation) that are being converted, in whole or in part,
           hereunder.

       A = The Fair Market Value of one Share (at the date of such calculation).

       B = The Exercise Price (as adjusted to the date of such calculation).

     For purposes of this Section 1.3, if any Shares of the Warrant Holder or
any other shareholder of the Company are registered or publicly traded, then the
Fair Market Value of one Share shall mean the average of the closing bid and
asked prices of the Common Stock quoted in the over the counter market summary
or the closing price quoted by the Nasdaq National Market or any exchange on
which the Common Stock is listed, whichever is applicable, as published in the
Western Edition of The Wall Street Journal (or the Financial Times (US Edition)
if not published in The Wall Street Journal) for the business day prior to the
date of determination of fair market value. If the Shares are not traded on the
Nasdaq National Market or on an exchange, the Fair Market Value of one Share
shall be determined in good faith by the Company's Board of Directors.

     1.4. Effectiveness. Each exercise or Net Issue Exercise of this Warrant
shall be deemed to have been effected immediately prior to the close of business
on the day on which this Warrant shall have been surrendered to the Company as
provided in Sections 1.2 or 1.3 above. At such time, the person or persons in
whose name or names any certificates for the Shares shall be issuable upon such
exercise or Net Issue Exercise as provided in Section 2 below shall be deemed to
have become the holder or holders of record of the Shares represented by such
certificates.

     2. Delivery of Stock Certificates, Etc. As soon as practicable after the
exercise or Net Issue Exercise of this Warrant in full or in part, and in any
event within 10 days thereafter, the Company at its expense will cause to be
issued in the name of, and delivered to, the Warrant Holder, or as such Warrant
Holder (upon payment by such Warrant Holder of any applicable transfer taxes)
may direct (i) a certificate or certificates for the number of fully paid and
non-assessable Shares to which the Warrant Holder shall be entitled upon such
exercise or Net Issue Exercise, and (ii) in case such exercise or Net Issue
Exercise is in part only, a new warrant or warrants (dated the date hereof) of
like tenor, calling in the aggregate on the face or faces thereof for the number
of Shares equal (without giving effect to any adjustment therein) to the number
of Shares called for on the face of this Warrant minus the number of Shares
purchased by the Warrant Holder upon such exercise or Net Issuance Exercise as
provided in Sections 1.2 or 1.3 herein.

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     3. Adjustments Upon Mandatory Conversion of Series E Preferred Stock. Upon
any mandatory conversion of the Series E Preferred Stock pursuant to the
Company's Certificate of Incorporation, as amended or amended and restated from
time to time, this Warrant shall cease to be exercisable for shares of Series E
Preferred Stock and shall become exercisable for that number of shares of Common
Stock into which the shares of Series E Preferred Stock purchasable hereunder
would have been convertible immediately prior to such mandatory conversion, and
such that payment of the Exercise Price, or any multiple thereof, shall entitle
the Warrant Holder to receive the number of shares of Common Stock as would have
been issued upon conversion of each share of Series E Preferred Stock
purchasable hereunder immediately prior to such mandatory conversion.

     4. Stock Splits, Stock Dividends and Combinations. If the Company at any
time subdivides the outstanding shares of Series E Preferred Stock, or issues a
stock dividend on the outstanding shares of Series E Preferred Stock, the
Exercise Price in effect immediately prior to such subdivision or the issuance
of such stock dividend shall be proportionately decreased, and the number of
Shares shall be proportionately increased, and if the Company at any time
combines the outstanding shares of Series E Preferred Stock, the Exercise Price
in effect immediately prior to such combination shall be proportionately
increased, and the number of shares shall be proportionately decreased,
effective at the close of business on the date of such subdivision, stock
dividend or combination, as the case may be. Upon any mandatory conversion of
the Series E Preferred Stock as provided in Section 3, each reference to Series
E Preferred Stock in this Section 4 shall be deemed to be Common Stock.

     5. Conversions; Reorganizations; Reclassifications; Merger; Sales. In case
of any capital reorganization or any reclassification of the capital stock of
the Company or in case of the consolidation or merger of the Company with or
into another corporation or the conveyance of all or substantially all of the
assets of the Company to another corporation (an "M&A Transaction"), this
Warrant shall thereafter be exercisable for the number of shares of stock or
other securities or property to which a holder of the number of Shares
deliverable upon exercise of the Warrant would have been entitled to upon such
conversion, reorganization, reclassification, consolidation, merger or
conveyance and, in any such case, appropriate adjustment as determined by the
Board of Directors of the Company shall be made in the application of the
provisions herein set forth with respect to the rights and interests thereafter
of the Warrant Holder to the end that the provisions set forth herein (including
provisions with respect to changes in and other adjustments of the Exercise
Price and the number of Shares) shall thereafter be applicable, as nearly as
reasonably may be, in relation to any shares of stock or other property
thereafter deliverable upon the exercise of the Warrant. Should the Board of
Directors make a good faith determination that compliance with the terms of this
Section will have a material adverse effect on the M&A Transaction, then the
Company may require that Warrant Holder exercise all or part of this Warrant on
the terms set forth herein.

     6. Statement of Adjustment. Whenever the Exercise Price shall be adjusted
as provided herein, the Company shall promptly file with the Secretary of the
Company or at such other place as shall be designated by the Company, a
statement, signed by its chief financial officer, showing in detail the facts
requiring such adjustment, the Exercise Price in effect before and after such
adjustment and the kind and amount of shares of capital stock, securities or
other property thereafter to be received upon the exercise of this Warrant. The
Company shall also

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cause a copy of such statement to be sent in the manner specified in Section
16.3 to the Warrant Holder.

     7. Notice of Adjustment. In the event the Company shall propose to take any
action of the types described in Sections 4 or 5, the Company shall give notice
to the Warrant Holder in the manner set forth in Section 16.3, which notice
shall specify the record date, if any, with respect to any such action and the
date on which such action is to take place. Such notice shall also set forth
such facts with respect thereto as shall be reasonably necessary to indicate the
effect of such action (to the extent such effect may be known at the date of
such notice) on the Exercise Price and the number, kind or class of shares or
other securities or property which shall be deliverable or purchasable upon the
occurrence of such action or deliverable upon the exercise hereof. In the case
of any action which would require the fixing of a record date, such notice shall
be given at least ten (10) days prior to the date so fixed, and in case of all
other actions, such notice shall be given at least twenty (20) days prior to the
taking of such proposed action. Failure to give such notice, or any defect
therein, shall not affect the legality or validity of any such action.

     8. Taxes. The Company shall pay all documentary, stamp or other
transactional taxes attributable to the issuance or delivery of shares of
capital stock of the Company upon the exercise or conversion hereof; provided,
however, Company shall have no obligation to pay any documentary, stamp or other
transactional taxes on transfers initiated by Warrant Holder.

     9. No Fractional Shares. Each adjustment in the number of Shares
purchasable hereunder shall be calculated, to the nearest whole share with
fractional shares disregarded.

     10. Covenants as to Series Preferred Stock and Common Stock. The Company
covenants and agrees that the shares of Series E Preferred Stock issuable
hereunder, and the Common Stock issuable upon conversion thereof, and the Common
Stock issuable hereunder, as the case may be, will, upon issuance in accordance
with the terms hereof, be validly issued and outstanding, fully paid and
nonassessable, and free from all taxes, liens and charges with respect to the
issuance thereof imposed by or through the Company. The Company further
covenants and agrees that the Company will at all times have authorized and
reserved, free from preemptive rights imposed by or through the Company, a
sufficient number of shares of Series E Preferred Stock and Common Stock to
provide for the exercise of the rights represented by this Warrant. The Company
further covenants and agrees that if any shares of capital stock to be reserved
for the purpose of the issuance of shares upon the exercise of this Warrant
require registration or qualification with or approval by the Securities and
Exchange Commission or any state regulatory agency under Federal or state law
(or by any analogous foreign regulatory body) before such shares may be validly
issued or delivered upon exercise, then the Company will in good faith and as
expeditiously as possible endeavor to secure such registration, qualification or
approval, as the case may be. Holders of Series E Preferred Stock and Common
Stock issuable upon exercise of this Warrant or conversion of any such shares,
as the case may be, shall be entitled to all the rights and privileges, and
bound by the obligations, of the Purchase Agreement, the Investor Rights
Agreement, and the Amended and Restated Voting Rights Agreement, all dated as of
the date hereof between the Company and the Investors (as defined therein) with
respect to such shares (the "Shareholder Agreements"). Upon exercise of the
Warrant, Warrant Holder at Company's request shall sign any counterpart
signature pages required in connection with becoming a party to such Shareholder
Agreements.

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     11. No Impairment. The Company will not voluntarily avoid or seek to avoid
the observance or performance of any of the terms of this Warrant, but will at
all times in good faith assist in the carrying out of all such terms and in the
taking of all such action as may be necessary or appropriate in order to protect
the rights of the Warrant Holder against impairment due to such event.

     12. Compliance with Securities Act.

     12.1 Unregistered Securities. The Warrant Holder acknowledges that this
Warrant and the Shares have not been registered under the Securities Act of
1933, as amended, and the rules and regulations thereunder, or any successor
legislation (the "Securities Act"), and agrees not to sell, pledge, distribute,
offer for sale, transfer or otherwise dispose of this Warrant or any Shares in
the absence of (i) an effective registration statement under the Securities Act
covering this Warrant or such Shares and registration or qualification of this
Warrant or such Shares under any applicable "blue sky" or state securities law
then in effect, or (ii) an opinion of counsel, satisfactory to the Company, that
such registration and qualification are not required. The Company may delay
issuance of the Shares until completion of any action or obtaining of any
consent, which the Company deems necessary under any applicable law (including
without limitation state securities or "blue sky" laws).

     12.2 Investment Representation. The Warrant Holder represents to the
Company that this Warrant is being acquired for the Warrant Holder's own account
and for the purpose of investment and not with a present view to, or for sale in
connection with, the distribution thereof, nor with any present intention of
distributing or selling the Warrant or Common Stock issuable upon exercise of
the Warrant. The Warrant Holder acknowledges that it has been afforded the
opportunity to meet with the management of the Company and to ask questions of,
and receive answers from, such management and the Company's counsel about the
business and affairs of the Company and concerning the terms and conditions of
the offering of this Warrant, and to obtain any additional information, to the
extent that the Company possessed such information or could acquire it without
unreasonable effort or expense, necessary to verify the accuracy of the
information otherwise obtained by or furnished to the Warrant Holder. The Holder
has received all information which the Warrant Holder considered necessary to
form a decision concerning the purchase of this Warrant, and no valid request to
the Company by the Warrant Holder hereof for information of any kind about the
Company has been refused or denied by the Company or remains unfulfilled as of
the date hereof. The Warrant Holder attests that it is considered to be a
sophisticated investor, is familiar with the risks inherent in speculative
investments such as in the Company, has such knowledge and experience in
financial business matters that he is capable of evaluating the merits and risk
of the investment in this Warrant and the Shares, and is able to bear the
economic risk of the investment. The Warrant Holder confirms that he is an
"accredited investor" as such term is defined in rule 501(a) of the Securities
Act.

     12.3 Investment Letter. Without limiting the generality of Section 12.1,
unless the offer and sale of any shares of Shares shall have been effectively
registered under the Securities Act, the Company shall be under no obligation to
issue the Shares unless and until the Warrant Holder shall have executed an
investment letter in form and substance satisfactory to the Company, including a
warranty at the time of such exercise that the Warrant Holder is acquiring such
shares for its own

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account, for investment and not with a view to, or for sale in connection with,
the distribution of any such shares.

     12.4 Legend. Certificates delivered to the Warrant Holder pursuant to
Section 2 shall bear the following legend or a legend in substantially similar
form (as well any such other legends as Company may reasonably require of its
shareholders generally):

     "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
     UNDER THE SECURITIES ACT OF 1933 OR ANY OTHER SECURITIES LAWS. THESE
     SECURITIES HAVE BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO
     DISTRIBUTION OR RESALE. SUCH SECURITIES MAY NOT BE OFFERED FOR SALE, SOLD,
     DELIVERED AFTER SALE, TRANSFERRED, PLEDGED OR HYPOTHECATED IN THE ABSENCE
     OF AN EFFECTIVE REGISTRATION STATEMENT COVERING SUCH SECURITIES UNDER THE
     SECURITIES ACT OF 1933 AND ANY OTHER APPLICABLE SECURITIES LAWS, UNLESS THE
     HOLDER SHALL HAVE OBTAINED AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO
     THE CORPORATION THAT SUCH REGISTRATION IS NOT REQUIRED."

     THE CORPORATION IS AUTHORIZED TO ISSUE MORE THAN ONE CLASS OR SERIES OF
     STOCK. THE CORPORATION WILL FURNISH WITHOUT CHARGE TO EACH STOCKHOLDER WHO
     SO REQUESTS THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE,
     PARTICIPATING, OPTIONAL, OR OTHER SPECIAL RIGHTS OF EACH CLASS OF STOCK OR
     SERIES THEREOF AND THE QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH
     PREFERENCES AND/OR RIGHTS.

     THE SHARES REPRESENTED HEREBY ARE ALSO SUBJECT TO RESTRICTIONS ON TRANSFER
     CONTAINED IN CERTAIN SUBSCRIPTION AND INVESTOR RIGHTS AGREEMENTS, AND MAY
     NOT BE SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT COMPLIANCE WITH THE
     TERMS THEREOF. THE COMPANY WILL FURNISH A COPY OF THE FULL TEXT OF SUCH
     RESTRICTIONS TO THE HOLDER OF THIS CERTIFICATE UPON WRHTEN REQUEST AND
     WITHOUT CHARGE.

     THE SHARES EVIDENCED BY THIS CERTIFICATE ARE SUBJECT TO A CERTAIN AMENDED
     AND RESTATED VOTING AGREEMENT DATED AS OF ______, 20__ BY AND AMONG THE
     COMPANY AND THE STOCKHOLDERS OF THE COMPANY, A COPY OF WHICH AGREEMENT IS
     AVAILABLE FOR INSPECTION AT THE OFFICES OF THE COMPANY OR MAY BE OBTAINED
     FROM THE COMPANY UPON REQUEST AND WITHOUT CHARGE.

     13. Transferability. Without the prior written consent of the Company,
neither the Warrant nor the shares issuable upon exercise thereof (the "Warrant
Shares") shall be assigned, pledged or hypothecated in any way (whether by
operation of law or otherwise) or be subject to execution, attachment or similar
process. Any attempted transfer, assignment, pledge,

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hypothecation or other disposition of the Warrant, Warrant Shares, or of any
rights granted hereunder contrary to the provisions of this Section 13, or the
levy of any attachment or similar process upon the Warrant, Warrant Shares, or
such rights, shall be null and void. If, in connection with a registration
statement filed by the Company pursuant to the Securities Act of 1933, the
Company or its underwriter so requests, the Warrant Holder will agree not to
sell any Warrant Shares for a period not to exceed 180 days following the
effectiveness of such registration.

     14. Lost, Stolen, Mutilated or Destroyed Warrant. If this Warrant is lost,
stolen, mutilated or destroyed, the Company may, on such terms as to indemnity
or otherwise as it may reasonably in its discretion impose (which shall in the
case of a mutilated Warrant, include the surrender thereof), issue a new Warrant
of like denomination and tenor as the Warrant so lost, stolen, mutilated or
destroyed.

     15. Register of Warrants. The Company shall maintain, at the principal
office of the Company (or such other office as it may designate by notice to the
Warrant Holder), a register for the Warrants in which the Company shall record
the name and address of the person in whose name a Warrant has been issued, as
well as the name and address of each transferee and each prior owner of such
Warrant.

     16. Miscellaneous.

     16.1 Waivers and Amendments. This Warrant or any provisions hereof may be
changed, waived, discharged or terminated only by a statement in writing signed
by the Company and by Warrant Holders who hold or have the right to acquire at
least two-thirds of the Shares at such time issued or issuable upon exercise of
the Warrants, provided that no change, addition, omission or waiver shall be
made without the written consent of the Warrant Holder(s) which affects (i) the
number of Shares issuable on exercise of this Warrant, (ii) the Exercise Price
or (iii) any other provision other than in a manner in which all the Warrants
are affected.

     16.2 Governing Law. This Agreement shall be governed by and construed and
enforced in accordance with the laws of the State of Delaware (US) without
giving effect to the conflicts of laws principles thereof.

     16.3 Notices. All notices or other communications required or permitted
hereunder shall be in writing and shall be hand delivered, sent by facsimile or
other electronic medium, or mailed, postage prepaid, or sent by reputable
overnight courier, delivery charges prepaid, addressed as follows or to such
other address as may be furnished in writing to the other parties hereto:

If to the Warrant Holder: Three Crowns Capital (Bermuda) Ltd.
                          Suite 1139
                          48 Par-La-Ville Road
                          Hamilton HM11
                          Bermuda
                          441-293 7107 (Fax)
                          Attention: Peter Svennilson

With a copy to:           Conyers Dill & Pearman

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                          Clarendon House
                          2 Church Street
                          Hamilton HM 11
                          Bermuda
                          441-292-4720 (Fax)
                          Attention: Peter A. S. Pearman

And:                      Nixon Peabody LLP
                          101 Federal Street
                          Boston, MA 02110
                          617-345-1300 (Fax)
                          Attention: Carter S. Bacon, Esq.

If to the Company:        PTC Therapeutics, Inc.
                          Attention: Legal Department
                          100 Corporate Court
                          Middlesex Business Center
                          South Plainfield, NJ 07080

                          with an email copy to: legal@ptcbio.com

With a copy to:           Wilmer Cutler Pickering Hale and Dorr LLP
                          60 State Street
                          Boston, Massachusetts 02109
                          Attn: David E. Redlick, Esq.

     All such notices and communications shall be deemed to have been duly given
(i) five (5) business days after being deposited in the mail, postage prepaid if
mailed, (ii) one (1) business day after being sent by overnight courier, (iii)
when receipt acknowledged if telecopied and (iv) upon receipt if delivered by
hand.

     16.4 Headings. The headings in this Warrant are for convenience of
reference only and shall not limit or otherwise affect the terms hereof.

     16.5 Remedies. The Company stipulates that the remedies at law of the
holder of this Warrant in the event of any default or threatened default by the
Company in the performance of or compliance with any of the terms of this
Warrant are not and will not be adequate, and that such terms may be
specifically enforced by a decree for the specific performance of any agreement
contained herein or by an injunction against a violation of any of the terms
hereof or otherwise.

     16.6 Currency. All currency references herein are to United States Dollars.

     16.7 Closing of Books. The Company will at no time close its transfer books
against the transfer of any Warrant or of any Shares issued or issuable upon the
exercise of the Warrant in a manner which interferes with the timely exercise of
this Warrant.

     16.8 No Rights or Liabilities as a Stockholder. This Warrant shall not
entitle the Warrant Holder to any voting rights or other rights as a stockholder
of the Company prior to the

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exercise or conversion of the Warrant, provided that nothing herein shall be
construed to limit or impair other rights that the Warrant Holder may have under
this Warrant or otherwise. No provision of this Warrant, in the absence of
affirmative action by the Warrant Holder to purchase the Shares, and no mere
enumeration herein of the rights or privileges of the Warrant Holder, shall give
rise to any liability of such Warrant Holder for the Exercise Price or as a
stockholder of the Company, whether such liability is asserted by the Company or
by creditors of the Company.

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     IN WITNESS WHEREOF, the undersigned has caused this Warrant to be executed
as an instrument under seal.

                                      PTC Therapeutics, Inc.

                                      By: /s/ MARK E. BOULDING
                                          ------------------------------------
                                      Name: Mark E. Boulding
                                            ----------------------------------
                                      Title: SVP, Business Development and Legal
                                             ---------------------------------

AGREED AND ACKNOWLEDGED:

THREE CROWNS CAPITAL (BERMUDA) LTD.

By: /s/ HARALD EKMAN
    ---------------------------------
Name: Harald Ekman
      -------------------------------
Title: President
       ------------------------------

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                                    EXHIBIT A

                    NOTICE OF EXERCISE OR NET ISSUE EXERCISE

                                                         Date: ________ __, 20__

YY

Gentlemen:

The undersigned hereby elects to exercise or Net Issue Exercise the enclosed
Warrant issued by YY (the "Company") and dated as of ____ __, 2003.

     The undersigned elects to:

[ ]  Exercise the Warrant and to purchase thereunder _____ shares of the Series
     __ Preferred Stock of the Company (the "Shares") at an exercise price of
     _____ per Share for an aggregate purchase price of _________ (the "Purchase
     Price"). Pursuant to the terms of the Warrant, the undersigned has
     delivered the Purchase Price herewith in full.

[ ]  Net Issue Exercise ____% of the value of the Warrant at the current
     Exercise Price (as defined in the Warrant) of ____ per Share.

                                        Very truly yours,

                                        ----------------------------------------<PAGE>
                                                                    Exhibit 10.1
                             PTC THERAPEUTICS, INC.
                           SIXTH AMENDED AND RESTATED
            1998 EMPLOYEE, DIRECTOR AND CONSULTANT STOCK OPTION PLAN

1.   DEFINITIONS. Unless otherwise specified or unless the context otherwise
     requires, the following terms, as used in this Sixth Amended and Restated
     PTC Therapeutics, Inc. 1998 Employee, Director and Consultant Stock Option
     Plan, have the following meanings:
          Administrator means the Board of Directors, unless it has delegated
          power to act on its behalf to the Committee, in which case the
          Administrator means the Committee.

          Affiliate means a corporation which, for purposes of Section 424 of
          the Code, is a parent or subsidiary of the Company, direct or
          indirect.

          Board of Directors means the Board of Directors of the Company.
          Certificate means an Option Certificate.

          Code means the United States Internal Revenue Code of 1986, as
          amended.

          Committee means the committee of the Board of Directors to which the
          Board of Directors has delegated power to act under or pursuant to the
          provisions of the Plan.

          Common Stock means shares of the Company's common stock, $.001 par
          value per share.

          Company means PTC Therapeutics, Inc., a Delaware corporation.

          Disability or Disabled means permanent and total disability as defined
          in Section 22(e)(3) of the Code.

          Fair Market Value of a Share of Common Stock means:
          (a) If the Common Stock is listed on a national securities exchange or
          traded in the over-the-counter market and sales prices are regularly
          reported for the Common Stock, the closing or last price of the Common
          Stock on the Composite Tape or other comparable reporting system for
          the trading day immediately preceding the applicable date;
          (b) If the Common Stock is not traded on a national securities
          exchange but is traded on the over-the-counter market, if sales prices
          are not regularly reported for the Common Stock for the trading day
          referred to in clause (a), and if bid and asked prices for the Common
          Stock are regularly reported, the mean between the bid and the asked
          price for the Common Stock at the close of trading in the
          over-the-counter market for the trading day on which Common Stock was
          traded immediately preceding the applicable date; and
          (c) If the Common Stock is neither listed on a national securities
          exchange nor traded in the over-the-counter market, such value as the
          Administrator, in good faith, shall determine.
          ISO means an option meant to qualify as an incentive stock option
          under Section 422 of the Code.

          Key Employee means any employee of the Company or of an Affiliate
          (including, without limitation, an employee who is also serving as an
          officer or director of the Company or of an Affiliate), or otherwise
          designated by the Administrator to be eligible to be granted one or
          more Options under the Plan.

          Non-Qualified Option means an option which is not intended to qualify
          as an ISO.

          Option means an ISO or Non-Qualified Option granted under the Plan.
          Option Certificate means a certificate delivered to the Participant by
          the Company pursuant to the Plan, in such form as the Administrator
          shall approve, which sets forth the terms and conditions of a Stock
          Option Grant.

          Participant means a Key Employee, director or consultant to whom one
          or more Options are granted under the Plan. As used herein,
          "Participant" shall include "Participant's Survivors" where the
          context requires.

          Plan means this Sixth Amended and Restated PTC Therapeutics, Inc. 1998
          Employee, Director and Consultant Stock Option Plan.

          Shares means shares of the Common Stock as to which Options have been
          or may be granted under the Plan or any shares of capital stock into
          which the Shares are changed or for which they are exchanged within
          the provisions of Paragraph 3 of the Plan. The Shares issued upon
          exercise of Options granted under the Plan may be authorized and
          unissued shares or shares held by the Company in its treasury, or
          both.

          Stock Option Grant means a grant of an option to purchase Shares under
          the Plan in either the form of an ISO or Non-Qualified Option.

          Survivors means a deceased Participant's legal representatives and/or
          any person or persons who acquired the Participant's rights to an
          Option by will or by the laws of descent and distribution.

2.   PURPOSES OF THE PLAN. The Plan is intended to encourage ownership of Shares
     by Key Employees and directors of and certain consultants to the Company in
     order to attract such people, to induce them to work for the benefit of the
     Company or of an Affiliate and to provide additional incentive for them to
     promote the success of the Company or of an Affiliate. The Plan provides
     for the granting of Stock Option Grants.

3.   SHARES SUBJECT TO THE PLAN.
            a.  The number of Shares which may be issued from time to time
                pursuant to this Plan shall be equal to Two Million Four Hundred
                Twenty-six Thousand Eight (2,426,008), or the equivalent of such
                numbers of Shares after the Administrator, in its sole
                discretion, has interpreted the effect of any stock split, stock
                dividend, combination, recapitalization or similar transaction
                in accordance with Paragraph 16 of the Plan;

            b.  The maximum number of Shares that may be issued as ISOs pursuant
                to this Plan shall be equal to Two Million Three Hundred
                Twenty-six Thousand Eight (2,326,008), or the equivalent of such
                numbers of Shares after the Administrator, in its sole
                discretion, has interpreted the effect of any stock split, stock
                dividend, combination, recapitalization or similar transaction
                in accordance with Paragraph 16 of the Plan; and

            c.  If an Option ceases to be "outstanding", in whole or in part,
                the Shares which were subject to such Option shall be available
                for the granting of other Options under the Plan. Any Option
                shall be treated as "outstanding" until such Option is exercised
                in full, or terminates or expires under the provisions of the
                Plan, or by agreement of the parties to the pertinent Option
                Certificate.

4.   ADMINISTRATION OF THE PLAN. The Administrator of the Plan will be the Board
     of Directors, except to the extent the Board of Directors delegates its
     authority to the Committee, in which case the Committee shall be the
     Administrator. Subject to the provisions of the Plan, the Administrator is
     authorized to:

          a.   Interpret the provisions of the Plan or of any Stock Option Grant
               or Option Certificate and to make all rules and determinations
               which it deems necessary or advisable for the administration of
               the Plan;
          b.   Determine which employees of the Company or of an Affiliate shall
               be designated as Key Employees and which of the Key Employees,
               directors and consultants shall be granted Options;
          c.   Determine the number of Shares for which an Option or Options
               shall be granted, provided, however, that in no event shall
               Options to purchase more than 700,000 Shares be granted to any
               Participant in any fiscal year; and
          d.   Specify the terms and conditions upon which an Option or Options
               may be granted
<PAGE>

     provided, however, that all such interpretations, rules, determinations,
     terms and conditions shall be made and prescribed in the context of
     preserving the tax status under Section 422 of the Code of those Options
     which are designated as ISOs. Subject to the foregoing, the interpretation
     and construction by the Administrator of any provisions of the Plan or of
     any Option granted under it shall be final, unless otherwise determined by
     the Board of Directors, if the Administrator is the Committee.

5.   ELIGIBILITY FOR PARTICIPATION. The Administrator will, in its sole
     discretion, name the Participants in the Plan, provided, however, that each
     Participant must be a Key Employee, director or consultant of the Company
     or of an Affiliate at the time an Option is granted. Notwithstanding the
     foregoing, the Administrator may authorize the grant of an Option to a
     person not then an employee, director or consultant of the Company or of an
     Affiliate; provided, however, that the actual grant of such Option shall be
     conditioned upon such person becoming eligible to become a Participant at
     or prior to the time of the delivery of the Option Certificate evidencing
     such Option. ISOs may be granted only to Key Employees. Non-Qualified
     Options may be granted to any Key Employee, director or consultant of the
     Company or an Affiliate. The granting of any Option to any individual shall
     neither entitle that individual to, nor disqualify him or her from,
     participation in any other grant of Options.

6.   TERMS AND CONDITIONS OF OPTIONS. Each Stock Option Grant shall be set forth
     in writing in an Option Certificate, duly executed by the Company and, to
     the extent required by law or requested by the Company, by the Participant.
     The Administrator may provide that Options be granted subject to such terms
     and conditions, consistent with the terms and conditions specifically
     required under this Plan, as the Administrator may deem appropriate
     including, without limitation, subsequent approval by the shareholders of
     the Company of this Plan or any amendments thereto.

          A. Non-Qualified Options: Each Option intended to be a Non-Qualified
          Option shall be subject to the terms and conditions which the
          Administrator determines to be appropriate and in the best interest of
          the Company, subject to the following minimum standards for any such
          Non-Qualified Option:

               a.   Option Price: Each Option Certificate shall state the option
                    price (per share) of the Shares covered by each Stock Option
                    Grant, which option price shall be determined by the
                    Administrator but shall not be less than 85% of the Fair
                    Market Value per share of Common Stock;

               b.   Each Option Certificate shall state the number of Shares to
                    which it pertains;

               c.   Each Option Certificate shall state the date or dates on
                    which it first is exercisable and the date after which it
                    may no longer be exercised, and may provide that the Option
                    rights accrue or become exercisable in installments over a
                    period of months or years, or upon the occurrence of certain
                    conditions or the attainment of stated goals or events, or
                    through other circumstances or programs approved by the
                    Administrator (the "Vesting Provisions");

               d.   The provisions of Paragraph 6(A)(c) above notwithstanding,
                    with the consent of the Administrator, the vesting
                    provisions specified in a Participant's employment agreement
                    shall be the Vesting Provisions that apply to the relevant
                    Non-Qualified Options; and

               e.   Exercise of any Option may be conditioned upon the
                    Participant's execution of a Share purchase agreement in
                    form satisfactory to the Administrator providing for certain
                    protections for the Company and its other shareholders,
                    including requirements that:

                    i.   The Participant's or the Participant's Survivors' right
                         to sell or transfer the Shares may be restricted; and

                    ii.  The Participant or the Participant's Survivors may be
                         required to execute letters of investment intent and
                         must also acknowledge that the Shares will bear legends
                         noting any applicable restrictions.

          B. ISOs: Each Option intended to be an ISO, in accordance with Section
          422 of the Code, shall be issued only to a Key Employee and be subject
          to the following terms and conditions, with such additional
          restrictions or changes as the Administrator determines are
          appropriate but not in conflict with Section 422 of the Code and
          relevant regulations and rulings of the Internal Revenue Service:

               a.   Minimum standards: The ISO shall meet the minimum standards
                    required of Non-Qualified Options, as described in Paragraph
                    6(A) above, except clause (a) thereunder;

               b.   Option Price: Immediately before the ISO is granted, if the
                    Participant owns, directly or by reason of the applicable
                    attribution rules in Section 424(d) of the Code:

                    i.   Ten percent (10%) or less of the total combined voting
                         power of all classes of stock of the Company or an
                         Affiliate, the Option price per share of the Shares
                         covered by each ISO shall not be less than one hundred
                         percent (100%) of the Fair Market Value per share of
                         the Shares on the date of the Stock Option Grant; or

                    ii.  More than ten percent (10%) of the total combined
                         voting power of all classes of stock of the Company or
                         an Affiliate, the Option price per share of the Shares
                         covered by each ISO shall not be less than one hundred
                         ten percent (110%) of the said Fair Market Value on the
                         date of the Stock Option Grant;

               c.   Term of Option: For Participants who own:

                    i.   Ten percent (10%) or less of the total combined voting
                         power of all classes of stock of the Company or an
                         Affiliate, each ISO shall terminate not more than ten
                         (10) years from the date of the Stock Option Grant or
                         at such earlier time as the Option Certificate may
                         provide; or

                    ii.  More than ten percent (10%) of the total combined
                         voting power of all classes of stock of the Company or
                         an Affiliate, each ISO shall terminate not more than
                         five (5) years from the date of the Stock Option Grant
                         or at such earlier time as the Option Certificate may
                         provide;

               d.   Limitation on Yearly Exercise: The Option Certificates shall
                    restrict the amount of ISOs which may be exercisable in any
                    calendar year (under this or any other ISO plan of the
                    Company or an Affiliate) so that the aggregate Fair Market
                    Value (determined at the time each ISO is granted) of the
                    stock with respect to which ISOs are exercisable for the
                    first time by the Participant in any calendar year does not
                    exceed one hundred thousand dollars ($100,000), provided
                    that this subparagraph (d) shall have no force or effect if
                    its inclusion in the Plan is not necessary for Options
                    issued as ISOs to qualify as ISOs pursuant to Section 422(d)
                    of the Code; and

               e.   Intention to be Treated as an ISO: It is the Company's
                    intent that an ISO qualify for the favorable tax treatment
                    provided to holders of Options that meet the standards of
                    Section 422 of the Code. Any provision of this Plan, an
                    Option Certificate or any other relevant document which
                    conflicts with the Code so that an Option intended to be an
                    ISO would not be deemed an ISO is null and void and any
                    ambiguities shall be resolved so that the Option qualifies
                    as an ISO. Nonetheless, if the Option is determined not to
                    be an ISO, the Participant shall be deemed to acknowledge
                    and agree that neither the Company nor any Affiliate is
                    responsible to compensate him or her or otherwise make up
                    for the treatment of the Option as a Non-

<PAGE>

                    Qualified Option and not as an ISO. The Participant is
                    deemed to have been advised to consult with his or her own
                    tax advisors regarding the tax effects of the Option and the
                    requirements necessary to obtain favorable tax treatment
                    under Section 422 of the Code, including, but not limited
                    to, holding period requirements.

7.   EXERCISE OF OPTIONS AND ISSUE OF SHARES. An Option (or any part or
     installment thereof) shall be exercised by giving written notice to the
     Company at its principal executive office address, together with provision
     for payment of the full purchase price in accordance with this Paragraph
     for the Shares as to which the Option is being exercised, and upon
     compliance with any other condition(s) set forth in the Option Certificate.
     Such written notice shall be signed by the person exercising the Option,
     shall state the number of Shares with respect to which the Option is being
     exercised and shall contain any representation required by the Plan or the
     Option Certificate. Payment of the purchase price for the Shares as to
     which such Option is being exercised shall be made (a) in United States
     dollars in cash or by check, or (b) at the discretion of the Administrator,
     through delivery of shares of Common Stock having a Fair Market Value equal
     as of the date of the exercise to the cash exercise price of the Option, or
     (c) at the discretion of the Administrator, by having the Company retain
     from the shares otherwise issuable upon exercise of the Option, a number of
     shares having a Fair Market Value equal as of the date of exercise to the
     exercise price of the Option, or (d) at the discretion of the
     Administrator, by delivery of the grantee's personal recourse note bearing
     interest payable not less than annually at no less than 100% of the
     applicable Federal rate, as defined in Section 1274(d) of the Code, or (e)
     at the discretion of the Administrator, in accordance with a cashless
     exercise program established with a securities brokerage firm, and as
     approved by the Administrator, or (f) at the discretion of the
     Administrator, by any combination of (a), (b), (c), (d) and (e) above.
     Notwithstanding the foregoing, the Administrator shall accept only such
     payment on exercise of an ISO as is permitted by Section 422 of the Code.

     The Company shall then reasonably promptly deliver the Shares as to which
     such Option was exercised to the Participant (or to the Participant's
     Survivors, as the case may be). In determining what constitutes "reasonably
     promptly," it is expressly understood that the issuance and delivery of the
     Shares may be delayed by the Company in order to comply with any law or
     regulation (including, without limitation, state securities or "blue sky"
     laws) which requires the Company to take any action with respect to the
     Shares prior to their issuance. The Shares shall, upon delivery, be
     evidenced by an appropriate certificate or certificates for fully paid,
     non-assessable Shares.

     The Administrator shall have the right to accelerate the date of exercise
     of any installment of any Option; provided that the Administrator shall not
     accelerate the exercise date of any installment of any Option granted to
     any Key Employee as an ISO (and not previously converted into a
     Non-Qualified Option pursuant to Paragraph 19) if such acceleration would
     violate the annual vesting limitation contained in Section 422(d) of the
     Code, as described in Paragraph 6.B.d.

     The Administrator may, in its discretion, amend any term or condition of an
     outstanding Stock Option Grant provided (i) such term or condition as
     amended is permitted by the Plan, (ii) any such amendment shall be made
     only with the consent of the Participant to whom the Option was granted, or
     in the event of the death of the Participant, the Participant's Survivors,
     if the amendment is adverse to the Participant, and (iii) any such
     amendment of any ISO shall be made only after the Administrator, after
     consulting the counsel for the Company, determines whether such amendment
     would constitute a "modification" of any Option which is an ISO (as that
     term is defined in Section 424(h) of the Code) or would cause any adverse
     tax consequences for the holder of such ISO.

8.   RIGHTS AS A SHAREHOLDER. No Participant to whom an Option has been granted
     shall have rights as a shareholder with respect to any Shares covered by
     such Option, except after due exercise of the Option and tender of the full
     purchase price, if any, for the Shares being purchased pursuant to such
     exercise and registration of the Shares in the Company's share register in
     the name of the Participant.

9.   ASSIGNABILITY AND TRANSFERABILITY OF OPTIONS. By its terms, an Option
     granted to a Participant shall not be transferable by the Participant other
     than (i) by will or by the laws of descent and distribution, (ii) as
     approved by the Administrator in its sole discretion and set forth in the
     applicable Option Certificate, (iii) if approved by the Administrator in
     its sole discretion, through establishment of blind trusts, family limited
     partnerships, or other estate planning vehicles wherein the Participant or
     his direct descendants are the primary beneficiary, (iv) if approved by the
     Administrator in its sole discretion, in accordance with the division of
     property rights set forth in an authorized settlement agreement arising
     from the Participant's divorce, or (v) under any other circumstances that
     are approved by the Administrator in its sole discretion. Notwithstanding
     the foregoing, an ISO transferred in accordance with subsections 9(ii)-(v)
     above shall no longer qualify as an incentive stock option under Section
     422 of the Code. The designation of a beneficiary of an Option by a
     Participant, with the prior approval of the Administrator and in such form
     as the Administrator shall prescribe, shall not be deemed a transfer
     prohibited by this Paragraph. Except as provided above, during the
     Participant's lifetime, an Option shall only be exercisable by such
     Participant (or by his or her legal representative) and shall not be
     assigned, pledged or hypothecated in any way (whether by operation of law
     or otherwise) and shall not be subject to execution, attachment or similar
     process. Any attempted transfer, assignment, pledge, hypothecation or other
     disposition of any Option or of any rights granted thereunder contrary to
     the provisions of this Plan, or the levy of any attachment or similar
     process upon an Option, shall be null and void.

     The Participant is required to notify the Company in writing immediately
     after the Participant makes a Disqualifying Disposition of any of the
     Shares acquired pursuant to the exercise of the Option. A Disqualifying
     Disposition is defined in Section 424(c) of the Code and includes any
     disposition (including any sale) of such Shares before the later of (a) two
     years after the date the Participant was granted the Option or (b) one year
     after the date the Participant acquired Shares by exercising the Option,
     except as otherwise provided in Section 424(c) of the Code. If the
     Participant has died before the Shares are sold, these holding period
     requirements do not apply and no Disqualifying Disposition can occur
     thereafter.

10.  EFFECT OF TERMINATION OF SERVICE OTHER THAN "FOR CAUSE" OR DEATH OR
     DISABILITY. Except as otherwise provided in the pertinent Option
     Certificate, in the event of a termination of service (whether as an
     employee, director or consultant) with the Company or an Affiliate before
     the Participant has exercised an Option, the following rules apply:

          a.   A Participant who ceases to be an employee, director or
               consultant of the Company or of an Affiliate (for any reason
               other than termination "for cause", Disability, or death for
               which events there are special rules in Paragraphs 11, 12, and
               13, respectively), may exercise any Option granted to him or her
               (i) within three (3) months of such termination to the extent
               that the Option is exercisable on the date of such termination of
               service, but only if the Administrator has so designated in the
               pertinent Option Certificate, or (ii) over such other term as the
               Administrator shall determine in its sole discretion;

          b.   Except as provided in Subparagraph (c) below, or Paragraph 12 or
               13, in no event may an Option Certificate provide, if an Option
               is intended to be an ISO, that the time for exercise be later
               than three (3) months after the Participant's termination of
               employment;

<PAGE>

          c.   The provisions of this Paragraph, and not the provisions of
               Paragraph 12 or 13, shall apply to a Participant who subsequently
               becomes Disabled or dies after the termination of employment,
               director status or consultancy in all cases with the Company or
               an Affiliate, provided, however, in the case of a Participant's
               Disability or death within three (3) months after the termination
               of employment, director status or consultancy, the Participant or
               the Participant's Survivors may exercise the Option within one
               (1) year after the date of the Participant's termination of
               employment, but in no event after the date of expiration of the
               term of the Option;

          d.   Notwithstanding anything herein to the contrary, if subsequent to
               a Participant's termination of employment, termination of
               director status or termination of consultancy, but prior to the
               exercise of an Option, the Board of Directors determines that,
               either prior or subsequent to the Participant's termination, the
               Participant engaged in conduct which would constitute "cause",
               then such Participant shall forthwith cease to have any right to
               exercise any Option;

          e.   A Participant to whom an Option has been granted under the Plan
               who is absent from work with the Company or with an Affiliate
               because of temporary disability (any disability other than a
               permanent and total Disability as defined in Paragraph 1 hereof),
               or who is on leave of absence for any purpose, shall not, during
               the period of any such absence, be deemed, by virtue of such
               absence alone, to have terminated such Participant's employment,
               director status or consultancy with the Company or with an
               Affiliate, except as the Administrator may otherwise expressly
               provide; and

          f.   Except as required by law or as set forth in the pertinent Option
               Certificate, Options granted under the Plan shall not be affected
               by any change of a Participant's status within or among the
               Company and any Affiliates, so long as the Participant continues
               to be an employee, director or consultant of the Company or any
               Affiliate.

11.  EFFECT OF TERMINATION OF SERVICE "FOR CAUSE". Except as otherwise provided
     in the pertinent Option Certificate, the following rules apply if the
     Participant's service (whether as an employee, director or consultant) with
     the Company or an Affiliate is terminated "for cause" prior to the time
     that all his or her outstanding Options have been exercised:

          a.   All outstanding and unexercised Options as of the time the
               Participant is notified his or her service is terminated "for
               cause" will immediately be forfeited;

          b.   In addition to any definition of the term "for cause" set forth
               in any employment agreement between the Company and the
               Participant, for purposes of this Plan, the term "cause" shall
               include, without limitation (i) the failure of the Participant to
               perform any of his material duties to the Company or any of its
               Affiliates, (ii) the conviction of the Participant of any felony
               involving moral turpitude, (iii) any acts of fraud or
               embezzlement by the Participant involving the Company or any of
               its Affiliates, (iv) violation of any federal, state or local
               law, or administrative regulation related to the business of the
               Company or any of its Affiliates, (v) a conflict of interest,
               (vi) conduct that could result in publicity reflecting
               unfavorably on the Company or any of its Affiliates in a material
               way, (vii) failure to comply with the policies of the Company or
               any of its Affiliates, (viii) the unauthorized disclosure of
               confidential information, or (ix) a breach of the terms of any
               employment agreement, confidentiality agreement, non-competition
               and non-solicitation agreement or any other agreement between the
               Participant and the Company or any of its Affiliates, after
               giving effect to the notification provisions, if any, and the
               mechanisms to remedy or cure a breach, if appropriate, as
               described in any such agreement. The determination of the
               Administrator as to the existence of "cause" will be conclusive
               on the Participant and the Company; and

          c.   "Cause" is not limited to events which have occurred prior to a
               Participant's termination of service, nor is it necessary that
               the Administrator's finding of "cause" occur prior to
               termination. If the Administrator determines, subsequent to a
               Participant's termination of service but prior to the exercise of
               an Option, that either prior or subsequent to the Participant's
               termination the Participant engaged in conduct which would
               constitute "cause," then the right to exercise any Option is
               forfeited.

12.  EFFECT OF TERMINATION OF SERVICE FOR DISABILITY. Except as otherwise
     provided in the pertinent Option Certificate, a Participant who ceases to
     be an employee, director or consultant of the Company or of an Affiliate by
     reason of Disability may exercise any Option granted to such Participant:

          a.   To the extent that the Option has become exercisable according to
               the vesting period of such Option as of the date of Disability;
               and

          b.   To the extent of a pro rata portion through the date of
               Disability of any additional Options that would have become
               exercisable on the next vesting date had the Participant not
               become Disabled. The proration shall be based upon the number of
               days accrued in the current vesting period prior to the date of
               Disability.

     A Disabled Participant may exercise such rights only within the period
     ending one (1) year after the date of the Participant's termination of
     employment, directorship or consultancy, as the case may be,
     notwithstanding that the Participant might have been able to exercise the
     Option as to some or all of the Shares on a later date if the Participant
     had not become disabled and had continued to be an employee, director or
     consultant or, if earlier, within the originally prescribed term of the
     Option.

     The Administrator shall make the determination both of whether Disability
     has occurred and the date of its occurrence (unless a procedure for such
     determination is set forth in another agreement between the Company and
     such Participant, in which case such procedure shall be used for such
     determination). If requested, the Participant shall be examined by a
     physician selected or approved by the Administrator, the cost of which
     examination shall be paid for by the Company.

13.  EFFECT OF DEATH WHILE AN EMPLOYEE, DIRECTOR OR CONSULTANT. Except as
     otherwise provided in the pertinent Option Certificate, in the event of the
     death of a Participant while the Participant is an employee, director or
     consultant of the Company or of an Affiliate, the Participant's Survivors
     may exercise any outstanding Option granted to the Participant:

          a.   To the extent that the Option has become exercisable according to
               the vesting period of such Option as of the date of death; and

          b.   To the extent of a pro rata portion through the date of death of
               any additional Options that would have become exercisable on the
               next vesting date had the Participant not died. The proration
               shall be based upon the number of days accrued in the current
               vesting period prior to the date of death.
     If the Participant's Survivors wish to exercise the Option, they must take
     all necessary steps to exercise the Option within one (1) year after the
     date of death of such Participant, notwithstanding that the decedent might
     have been able to exercise the Option as to some or all of the Shares on a
     later date if he or she had not died and had continued to be an employee,
     director or consultant or, if earlier, within the originally prescribed
     term of the Option.

<PAGE>

14.  PURCHASE FOR INVESTMENT. Unless the offering and sale of the Shares to be
     issued upon the particular exercise of an Option shall have been
     effectively registered under the Securities Act of 1933, as now in force or
     hereafter amended (the "1933 Act"), the Company shall be under no
     obligation to issue the Shares covered by such exercise unless and until
     the following conditions have been fulfilled:

          a.   The person(s) who exercise(s) such Option shall warrant to the
               Company, prior to the receipt of such Shares, that such person(s)
               are acquiring such Shares for their own respective accounts, for
               investment, and not with a view to, or for sale in connection
               with, the distribution of any such Shares, in which event the
               person(s) acquiring such Shares shall be bound by the provisions
               of the following legend which shall be endorsed upon the
               certificate(s) evidencing their Shares issued pursuant to such
               exercise or such grant:

               "The shares represented by this certificate have been taken for
               investment, and they may not be sold or otherwise transferred by
               any person, including a pledgee, unless (1) either (a) a
               Registration Statement with respect to such shares shall be
               effective under the Securities Act of 1933, as amended, or (b)
               the Company shall have received an opinion of counsel
               satisfactory to it that an exemption from registration under such
               Act is then available, and (2) there shall have been compliance
               with all applicable state securities laws."; and

          b.   At the discretion of the Administrator, the Company shall have
               received an opinion of its counsel that the Shares may be issued
               upon such particular exercise in compliance with the 1933 Act
               without registration thereunder.

15.  DISSOLUTION OR LIQUIDATION OF THE COMPANY. Upon the dissolution or
     liquidation of the Company, all Options granted under this Plan which as of
     such date shall not have been exercised will terminate and become null and
     void; provided, however, that if the rights of a Participant or a
     Participant's Survivors have not otherwise terminated and expired, the
     Participant or the Participant's Survivors will have the right immediately
     prior to such dissolution or liquidation to exercise any Option to the
     extent that the Option is exercisable as of the date immediately prior to
     such dissolution or liquidation.

16.  ADJUSTMENTS. Upon the occurrence of any of the following events, a
     Participant's rights with respect to any Option granted to him or her
     hereunder which has not previously been exercised in full shall be adjusted
     as hereinafter provided, unless otherwise specifically provided in the
     pertinent Option Certificate or, subject to the consent of the
     Administrator, as otherwise specified in an employment or other agreement
     between the Company and the Participant:

                    A. Stock Dividends and Stock Splits. If (i) the shares of
                    Common Stock shall be subdivided or combined into a greater
                    or smaller number of shares or if the Company shall issue
                    any shares of Common Stock as a stock dividend on its
                    outstanding Common Stock, or (ii) additional shares or new
                    or different shares or other securities of the Company or
                    other non-cash assets are distributed with respect to such
                    shares of Common Stock, the number of shares of Common Stock
                    deliverable upon the exercise of such Option may be
                    appropriately increased or decreased proportionately, and
                    appropriate adjustments may be made in the purchase price
                    per share to reflect such events. The number of Shares
                    subject to the limitation in Paragraph 4(c) shall also be
                    proportionately adjusted upon the occurrence of such events.

                    B. Consolidations or Mergers. If the Company is to be
                    consolidated with or acquired by another entity in a merger,
                    sale of all or substantially all of the Company's assets or
                    otherwise (an "Acquisition"), the Administrator or the board
                    of directors of any entity assuming the obligations of the
                    Company hereunder (the "Successor Board"), shall, as to
                    outstanding Options, either (i) make appropriate provision
                    for the continuation of such Options by substituting on an
                    equitable basis for the Shares then subject to such Options,
                    including without limitation any provisions relating to the
                    acceleration of vesting, either the consideration payable
                    with respect to the outstanding shares of Common Stock in
                    connection with the Acquisition or securities of any
                    successor or acquiring entity; or (ii) upon written notice
                    to the Participants, provide that all vested Options must be
                    exercised (either to the extent then exercisable, including
                    Options subject to accelerated vesting provisions, or, at
                    the discretion of the Administrator, all Options being made
                    fully exercisable for purposes of this Subparagraph), at the
                    end of which period the Options shall terminate; or (iii)
                    terminate all Options in exchange for a cash payment equal
                    to the excess of the Fair Market Value of the Shares subject
                    to such Options (either to the extent then exercisable or,
                    at the discretion of the Administrator, all Options being
                    made fully exercisable, including Options subject to
                    accelerated vesting provisions, for purposes of this
                    Subparagraph) over the exercise price thereof.

                    C. Recapitalization or Reorganization. In the event of a
                    recapitalization or reorganization of the Company (other
                    than a transaction described in Subparagraph B above)
                    pursuant to which securities of the Company or of another
                    corporation are issued with respect to the outstanding
                    shares of Common Stock, a Participant upon exercising an
                    Option shall be entitled to receive for the purchase price,
                    if any, paid upon such exercise the securities which would
                    have been received if such Option had been exercised prior
                    to such recapitalization or reorganization.

                    D. Modification of ISOs. Notwithstanding the foregoing, any
                    adjustments made pursuant to Subparagraph A, B or C above
                    with respect to ISOs shall be made only after the
                    Administrator, after consulting with counsel for the
                    Company, determines whether such adjustments would
                    constitute a "modification" of such ISOs (as that term is
                    defined in Section 424(h) of the Code) or would cause any
                    adverse tax consequences for the holders of such ISOs. If
                    the Administrator determines that such adjustments made with
                    respect to ISOs would constitute a modification of such
                    ISOs, it may refrain from making such adjustments, unless
                    the holder of an ISO specifically requests in writing that
                    such adjustment be made and such writing indicates that the
                    holder has full knowledge of the consequences of such
                    "modification" on his or her income tax treatment with
                    respect to the ISO.

17.  ISSUANCES OF SECURITIES. Except as expressly provided herein, no issuance
     by the Company of shares of stock of any class, or securities convertible
     into shares of stock of any class, shall affect, and no adjustment by
     reason thereof shall be made with respect to, the number or price of shares
     subject to Options. Except as expressly provided herein, no adjustments
     shall be made for dividends paid in cash or in property (including without
     limitation, securities) of the Company prior to any issuance of Shares
     pursuant to a Stock Option Grant.

18.  FRACTIONAL SHARES. No fractional shares shall be issued under the Plan and
     the person exercising such right shall receive from the Company cash in
     lieu of such fractional shares equal to the Fair Market Value thereof.

19.  CONVERSION OF ISOs INTO NON-QUALIFIED OPTIONS; TERMINATION OF ISOs. The
     Administrator, at the written request of any Participant, may in its
     discretion take such actions as may be necessary to convert such
     Participant's ISOs (or any portions thereof) that have not been exercised
     on the date of conversion into Non-Qualified Options at any time prior to
     the expiration of such ISOs, regardless of whether the Participant is an
     employee of the Company or an Affiliate at the time of such conversion.
     Such actions may include, but not be limited to,

<PAGE>

     extending the exercise period or reducing the exercise price of the
     appropriate installments of such Options. At the time of such conversion,
     the Administrator (with the consent of the Participant) may impose such
     conditions on the exercise of the resulting Non-Qualified Options as the
     Administrator in its discretion may determine, provided that such
     conditions shall not be inconsistent with this Plan. Nothing in the Plan
     shall be deemed to give any Participant the right to have such
     Participant's ISOs converted into Non-Qualified Options, and no such
     conversion shall occur until and unless the Administrator takes appropriate
     action. The Administrator, with the consent of the Participant, may also
     terminate any portion of any ISO that has not been exercised at the time of
     such conversion.

20.  WITHHOLDING. In the event that any federal, state, or local income taxes,
     employment taxes, Federal Insurance Contributions Act ("F.I.C.A.")
     withholdings or other amounts are required by applicable law or
     governmental regulation to be withheld from the Participant's salary, wages
     or other remuneration in connection with the exercise of an Option or a
     Disqualifying Disposition (as defined in Paragraphs 9 and 21), the Company
     may withhold from the Participant's compensation, if any, or may require
     that the Participant advance in cash to the Company, or to any Affiliate of
     the Company which employs or employed the Participant, the statutory
     minimum amount of such withholdings unless a different withholding
     arrangement, including the use of shares of the Company's Common Stock or a
     promissory note, is authorized by the Administrator (and permitted by law).
     For purposes hereof, the fair market value of the shares withheld for
     purposes of payroll withholding shall be determined in the manner provided
     in Paragraph 1 above, as of the most recent practicable date prior to the
     date of exercise. If the fair market value of the shares withheld is less
     than the amount of payroll withholdings required, the Participant may be
     required to advance the difference in cash to the Company or the Affiliate
     employer. The Administrator in its discretion may condition the exercise of
     an Option for less than the then Fair Market Value on the Participant's
     payment of such additional withholding.

21.  NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION. Each Key Employee who
     receives an ISO must agree to notify the Company in writing immediately
     after the Key Employee makes a Disqualifying Disposition of any shares
     acquired pursuant to the exercise of an ISO. A Disqualifying Disposition is
     any disposition (including any sale) of such shares before the later of (a)
     two years after the date the Key Employee was granted the ISO, or (b) one
     year after the date the Key Employee acquired Shares by exercising the ISO.
     If the Key Employee has died before such stock is sold, these holding
     period requirements do not apply and no Disqualifying Disposition can occur
     thereafter.

22.  TERMINATION OF THE PLAN. The Plan will terminate on August 12, 2008, the
     date which is ten (10) years from the earlier of the date of its adoption
     and the date of its approval by the shareholders of the Company. The Plan
     may be terminated at an earlier date by vote of the shareholders of the
     Company; provided, however, that any such earlier termination shall not
     affect any Option Certificates executed prior to the effective date of such
     termination.

23.  AMENDMENT OF THE PLAN AND CERTIFICATES. The Plan may be amended by the
     shareholders of the Company. The Plan may also be amended by the
     Administrator, including, without limitation, to the extent necessary to
     qualify any or all outstanding Options granted under the Plan or Options to
     be granted under the Plan for favorable federal income tax treatment
     (including deferral of taxation upon exercise) as may be afforded incentive
     stock options under Section 422 of the Code, and to the extent necessary to
     qualify the shares issuable upon exercise of any outstanding Options
     granted, or Options to be granted, under the Plan for listing on any
     national securities exchange or quotation in any national automated
     quotation system of securities dealers. Any amendment approved by the
     Administrator which the Administrator determines is of a scope that
     requires shareholder approval shall be subject to obtaining such
     shareholder approval. Any modification or amendment of the Plan shall not,
     without the consent of a Participant, adversely affect his or her rights
     under an Option previously granted to him or her. With the consent of the
     Participant affected, the Administrator may amend outstanding Option
     Certificates in a manner which may be adverse to the Participant but which
     is not inconsistent with the Plan. In the discretion of the Administrator,
     outstanding Option Certificates may be amended by the Administrator in a
     manner which is not adverse to the Participant. Except as provided herein,
     the terms and provisions of any Option Certificate may be waived, or
     consent for the departure therefrom granted, only by written document
     executed by the party entitled to the benefits of such terms or provisions.
     No such waiver or consent shall be deemed to be or shall constitute a
     waiver or consent with respect to any other terms or provisions of such
     Option Certificate, whether or not similar. Each such waiver or consent
     shall be effective only in the specific instance and for the purpose for
     which it was given, and shall not constitute a continuing waiver or
     consent.

24.  EMPLOYMENT OR OTHER RELATIONSHIP. Nothing in this Plan or any Option
     Certificates shall be deemed to prevent the Company or an Affiliate from
     terminating the employment, consultancy or director status of a
     Participant, nor to prevent a Participant from terminating his or her own
     employment, consultancy or director status or to give any Participant a
     right to be retained in employment or other service by the Company or any
     Affiliate for any period of time.

25.  GOVERNING LAW. This Plan shall be construed and enforced in accordance with
     the law of the State of Delaware.

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