Document:

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                                                                     Exhibit 4.6

THIS WARRANT AND THE SHARES OF CAPITAL STOCK ISSUED UPON ANY EXERCISE HEREOF
HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
"SECURITIES ACT"), OR ANY APPLICABLE STATE SECURITIES LAWS AND MAY NOT BE SOLD
OR OTHERWISE TRANSFERRED BY ANY PERSON, INCLUDING A PLEDGEE, UNLESS (1) EITHER
(A) A REGISTRATION WITH RESPECT TO THERETO SHALL BE EFFECTIVE UNDER THE
SECURITIES ACT, OR (B) THE COMPANY SHALL HAVE RECEIVED AN OPINION OF COUNSEL
SATISFACTORY TO THE COMPANY THAT AN EXEMPTION FROM REGISTRATION UNDER THE
SECURITIES ACT IS AVAILABLE, AND (2) THERE SHALL HAVE BEEN COMPLIANCE WITH ALL
APPLICABLE STATE SECURITIES OR "BLUE SKY" LAWS.

                                     For the purchase of up to 107,096 shares of
                                 shares of Series D Convertible Preferred Stock,
                                                       par value $.001 per share

No. W-03                                                         August 28, 2001

      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., eastern time, on August 28, 2011 (the "Exercise
Period"), up to 107,096 fully-paid and non-assessable shares of Series D
Convertible Preferred Stock, par value $.001 per share, of the Company (the
"Series D 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 D Preferred Stock as provided in Section 3 hereof (the Series D 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
$3.25 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 August 28, 2001.

      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

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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 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 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.

      3. Adjustments Upon Mandatory Conversion of Series D Preferred Stock. Upon
any mandatory conversion of the Series D Preferred Stock pursuant to the
Company's Certificate of

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Incorporation, as amended or amended and restated from time to time, this
Warrant shall cease to be exercisable for shares of Series D Preferred Stock and
shall become exercisable for that number of shares of Common Stock into which
the shares of Series D 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 D 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 D Preferred Stock, or issues a
stock dividend on the outstanding shares of Series D 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 D 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 D Preferred Stock as provided in Section 3, each reference to Series
D Preferred Stock in this Section 4 shall be deemed to be Common Stock.

      5. Conversions; Reorganizations; Reclassification; 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, 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.

      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 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

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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.

      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 D Preferred Stock and Common Stock. The Company
covenants and agrees that the shares of Series D 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, with no personal liability attaching to the ownership thereof,
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 D 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 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 D 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 of the Purchase Agreement and the Registration Rights Agreement dated
as of the date hereof between the Company and the Investors (as defined therein)
with respect to such shares.

      11. No Impairment. The Company will not, by amendment of its Certificate
of Incorporation or through any reorganization, transfer of assets,
consolidation, merger, dissolution, or any other similar voluntary action, 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. Without limiting the generality of the foregoing,
the Company (a) will not increase the

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par value of any shares of stock receivable on the exercise of the Warrant above
the amount payable therefor on such exercise, (b) will take all action that may
be necessary or appropriate in order that the Company may validly and legally
issue fully paid and nonassessable shares of stock, free from all taxes, liens
and charges with respect to the issue thereof, on the exercise of all of the
Warrants from time to time outstanding and (c) will not consolidate with or
merge into any other person or permit any such person to consolidate with or
merge into the Company (if the Company is not the surviving person), unless such
other person shall expressly assume in writing and will be bound by all the
terms of this Warrant.

      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 may be 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

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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 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:

      "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
      UNDER THE SECURITIES ACT OF 1933 OR ANY OF THE 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."

      13. Transferability. Without the prior written consent of the Company, the
Warrant 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 the Warrant 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 or such rights, shall be null and void.

      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)

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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 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.
                                    Clarendon House
                                    PO Box HM 666
                                    2 Church Street
                                    Hamilton HM KX
                                    Bermuda
                                    441-292-4720 (Fax)
                                    Attention:  Peter Svennilson

With a copy to:                     Conyers Dill & Pearman
                                    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
                                    Attention:  Carter S. Boom, Jr.

If to the Company:                  PTC Therapeutics, Inc.
                                    Two Chestnut Street
                                    Grafton, MA 01519
                                    508-856-5920 (Fax)
                                    Attention:  President

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With a copy to:                     Mintz, Levin, Cohn, Ferris, Glovsky and
                                    Popeo, P.C.
                                    One Financial Center
                                    Boston, MA 02111
                                    617-542-6000
                                    617-542-2241 (Fax)
                                    Attention:  Jeffrey M. Wiesen, 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. 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.

      16.7. 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 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/ Stuart Peltz
                                       ________________________________
                                   Name:    Stuart W. Peltz, Ph.D.
                                   Title:   President

AGREED AND ACKNOWLEDGED:

THREE CROWNS CAPITAL (BERMUDA) LTD.

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                                    EXHIBIT A

                    NOTICE OF EXERCISE OR NET ISSUE EXERCISE

                                                Date:
                                                      __________________________

PTC Therapeutics, Inc.
100 Corporate Court
Middlesex Business Center
South Plainfield, NJ 07080
Attention:  President

Gentlemen:

      The undersigned hereby elects to exercise or Net Issue Exercise the
enclosed Warrant issued to it by PTC Therapeutics, Inc. (the "Company") and
dated as of _______, 20__.

      The undersigned elects to:

      [ ]   Exercise the Warrant and to purchase thereunder ______ shares of the
            Series D Preferred Stock of the Company (the "Shares") at an
            exercise price of ______ per Share for an aggregate purchase price
            of Dollars ($_______) (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,

                                                ________________________________

Receipt Acknowledged:

PTC Therapeutics, Inc.

By
   ________________________________
on
   ________________________________

                                       10<PAGE>
                                                                     Exhibit 4.7

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED HYPOTHECATED OR
OTHERWISE TRANSFERRED IN VIOLATION OF SUCH ACT, THE RULES AND REGULATIONS
THEREUNDER, OR THE PROVISIONS OF THIS WARRANT. THIS WARRANT HAS BEEN ACQUIRED
FOR INVESTMENT AND NOT WITH A VIEW TO DISTRIBUTION OR RESALE.

No. of Shares of Series D Convertible Preferred             Warrant No. W-GE-01D
Stock: 59,378

                                     WARRANT

               TO PURCHASE SERIES D CONVERTIBLE PREFERRED STOCK OF

                             PTC THERAPEUTICS, INC.

      GENERAL ELECTRIC CAPITAL CORPORATION, or registered assigns, in exchange
for consideration the receipt and sufficiency of which is hereby acknowledged,
is entitled, at any time during the Exercise Period (as hereinafter defined), to
purchase from PTC THERAPEUTICS, INC., a Delaware corporation ("Company"), 59,378
shares of Series D Convertible Preferred Stock (as hereinafter defined and
subject to adjustment as provided herein), in whole or in part, at a purchase
price of THREE and 25/00 Dollars ($3.25) per share (subject to adjustment as
provided in Article IV) (as so adjusted, the "Exercise Price") on the terms and
conditions set forth herein.

I. DEFINITIONS

      The following terms have the meanings set forth below:

      "Additional Shares of Series D Stock" means all shares of Series D Stock
issued by Company after the date of this Warrant other than Warrant Stock.

      "Additional Shares of Stock" has the same meaning ascribed to the term
"Additional Shares of Common Stock" set forth in the Certificate of
Incorporation.

      "Board" means the Board of Directors of Company.

      "Business Day" means any day that is not a Saturday, a Sunday or a day on
which commercial banks in the State of New York are required or permitted by law
or executive order to be closed.

      "Certificate of Incorporation" means the Restated Certificate of
Incorporation of the Company, as may be amended or amended and restated from
time to time.

<PAGE>

      "Common Stock" has the same meaning ascribed to the term "Common Stock"
set forth in the Certificate of Incorporation.

      "Company" has the meaning set forth in the recitals.

      "Convertible Security" means any option, warrant or share of preferred
stock of Company or any other security or instrument, including without
limitation any evidence of indebtedness, in any case, which is convertible
directly or indirectly into or exchangeable with or without payment of
additional consideration for Additional Shares of Stock, either immediately or
upon the occurrence of a specified date or a specified event.

      "Current Market Price" means, in respect of a share of Series D Preferred
Stock (or any other security for which this Warrant is then exercisable) on any
date of determination, either (a) if there shall then be a public market for the
trading of Series D Preferred Stock (or any other security for this Warrant is
then exercisable), the average of the daily market prices (determined as
provided below) for ten (10) consecutive trading days commencing 12 trading days
immediately before such date, or (b) if there shall not then be a public trading
market for the Series D Preferred Stock (or any other security for which this
Warrant is then exercisable), the fair market value (determined as provided
below) of a share of the Series D Preferred Stock (or any other security for
which this Warrant is then exercisable) as at such date. For purposes of clause
(a), the "daily market price" for any trading day shall be (i) the closing price
of the principal trading session on such day on the New York Stock Exchange or
other principal national stock exchange or, if none, the last sale price on the
National Market of the NASDAQ on which the Series D Preferred Stock (or any
other security for which this Warrant is then exercisable) is then listed or
admitted to trading, (ii) if no sale takes place on such day on any such
exchange or NASDAQ, the average of the last reported closing bid and ask prices
on such day as officially quoted on any such exchange or NASDAQ, (iii) if the
Series D Preferred Stock (or any other security for which this Warrant is then
exercisable) is not then listed or admitted to trading on any national stock
exchange or National Market of NASDAQ, the average of the last reported closing
bid and ask prices on such day in the over-the-counter market as furnished by
the National Quotation Bureau, Incorporated (or similar organization or agency
succeeding to its functions of reporting security prices), or (iv) if there is
no such firm, as furnished by any member of the NASD or the New York Stock
Exchange selected by the Required Holders and Company or, if they cannot agree
upon such selection, as selected by two such members of the NASD or New York
Stock Exchange, one of which shall be selected by the Required Holders and one
of which shall be selected by Company. For purposes of clause (b), "fair market
value" shall be the price that reflects the value of such shares on a fully
distributed basis (that is, as if such shares were traded on a free and active
market on an exchange or over-the-counter) in a sale by a willing seller under
no compulsion to sell and a willing buyer under no compulsion to buy, without
any premium or discount for any reason, including but not limited to any
discount related to the offering of such shares, any premium for control or any
discount for illiquidity, as agreed upon by Company and the Required Holders;
provided, however, that if Company and the Required Holders cannot agree on such
fair market value, then Company shall engage an investment banking firm of
nationally recognized standing mutually acceptable to and selected

                                      -2-
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by Company and the Required Holders within ten (10) days after the date of the
event or notice giving rise to the need to determine fair market value to
determine fair market value in accordance with the preceding provisions. If
Company and the Required Holders cannot agree on a mutually acceptable
investment banking firm within such ten (10) day period, or if a mutually
acceptable investment banking firm is unable or unwilling to perform the
valuation contemplated hereby, Company and the Required Holders shall, within
such ten (10) day period, each choose one investment banking firm of recognized
standing and the respective chosen firms shall, within five (5) days after the
later of such firms is chosen, agree on another investment banking firm which
shall be engaged to make the determination of the fair market value in
accordance with the preceding provisions. The determination by the engaged firm
shall be made as soon as practicable, but not later than thirty (30) days after
the date such firm is engaged. The cost of the investment banking firm or firms
selected shall be borne by Company.

      "Exchange Act" means the Securities Exchange Act of 1934, as amended, and
all rules and regulations promulgated thereunder.

      "Exercise Period" has the meaning set forth in Section 2.1.

      "Exercise Price" has the meaning set forth in the first paragraph of this
Warrant.

      "Expiration Date" means the last day of the Exercise Period on which the
Warrant may be exercised.

      "Governmental Authority" means any nation or government, any state or
other political subdivision thereof, and any agency, department or other entity
exercising executive, legislative, judicial, regulatory or administrative
functions of or pertaining to government.

      "Holder" means GENERAL ELECTRIC CAPITAL CORPORATION, a New York
corporation, any of its successors, or any of their registered assigns.

      "Investor Rights Agreement" means the Fourth Amended and Restated Investor
Rights Agreement made between the Company and the other signatories thereto,
dated December 17, 2003, as may be amended or amended and restated from time to
time.

      "NASD" means the National Association of Securities Dealers, Inc., or any
successor thereto.

      "NASDAQ" means the automated quotation system of the NASD.

      "Organic Change" means (a) any sale, lease, exchange or other transfer of
all or substantially all of the property, assets or business of Company, (b) any
liquidation, dissolution or winding up of Company, whether voluntary or
involuntary, (c) any merger or consolidation to which Company is a party and
pursuant to which either (i) the holders of the voting

                                      -3-
<PAGE>

securities of Company immediately prior thereto own less than a majority of the
outstanding voting securities of the surviving entity immediately following such
transaction or (ii) the holders of the voting securities of Company immediately
prior thereto do not have the ability to elect a majority of the members of the
board of directors (or Persons performing similar functions) of the surviving
entity immediately following such transaction, or (d) any Person or group (as
such term is used in Section 13(d) of the Exchange Act) of Persons, other than
any current shareholder owning 10% of the Common Stock Outstanding as of the
date of issuance of this Warrant, shall either (i) beneficially own (as defined
in Rule 13d-3 under the Exchange Act) securities of Company representing 50% or
more of the voting securities of Company then outstanding or (ii) have the
ability to elect a majority of the members of the board of directors (or Persons
performing similar functions) of the surviving entity. For purposes of the
preceding sentence, "voting securities" shall mean securities, the holders of
which are ordinarily entitled to elect the members of the board of directors (or
Persons performing similar functions).

      "Outstanding" means, (i) when used with reference to Common Stock, on any
date, all issued shares of Common Stock on such date, except shares then owned
or held by or for the account of Company or any Subsidiary thereof (or any
successors or acquiring corporation), including shares of the Common Stock
issuable upon exercise or conversion of any outstanding Rights or Convertible
Securities, and shall include all shares issuable in respect of outstanding
scrip or any certificates representing fractional interests in shares of Common
Stock; and (ii) when used with reference to Series D Preferred Stock, on any
date, all issued shares of Series D Preferred Stock on such date, except shares
then owned or held by or for the account of Company or any Subsidiary thereof
(or any successors or acquiring corporation), including shares of the Series D
Preferred Stock issuable upon exercise or conversion of any outstanding Rights
or Convertible Securities, and shall include all shares issuable in respect of
outstanding scrip or any certificates representing fractional interests in
shares of Series D Preferred Stock.

      "Permitted Issuances" has the same meaning ascribed to the term "Excluded
Securities" set forth in the Certificate of Incorporation.

      "Qualified Initial Public Offering" has the meaning ascribed to the term
"Initial Public Offering" set forth in the Investor Rights Agreement.

      "Required Holders" means the holders of Warrants exercisable for in excess
of 50% of the aggregate number of Warrant Stock then purchasable upon exercise
of all Warrants.

      "Rights" means any warrants, options or other rights to purchase Series D
Preferred Stock.

      "SEC" means the U.S. Securities and Exchange Commission, or any successor
thereto.

      "Securities Act" means the Securities Act of 1933, as amended, and all
rules and regulations promulgated thereunder.

      "Series D Preferred Stock" has the meaning ascribed to the term "Series D
Preferred Stock" set forth in the Certificate of Incorporation.

                                     - 4 -

<PAGE>

      "Stock" means any shares of capital stock of the Company.

      "Subsidiary" has the meaning ascribed to the term "Subsidiary" set forth
in the Investor Rights Agreement.

      "Transfer" means any disposition of any Warrant or Warrant Stock or of any
interest in either thereof, which would constitute a sale thereof within the
meaning of the Securities Act.

      "Warrant" means this Warrant and all warrants issued upon transfer,
division or combination of, or in substitution for, this Warrant. All Warrants
shall at all times be identical as to terms and conditions and date, except as
to the number of shares of Series D Preferred Stock for which they may be
exercised.

      "Warrant Price" means an amount equal to (i) the number of shares of
Series D Preferred Stock being purchased upon exercise of this Warrant pursuant
to Section 2.1, multiplied by (i) the Exercise Price as of the date of such
exercise.

      "Warrant Stock" means the shares of Series D Preferred Stock issued or
issuable upon the exercise of this Warrant.

II. EXERCISE OF WARRANT

      2.1. Exercise Period. From and after the date hereof and until 5:00 P.M.,
New York time, on APRIL 30, 2009 (the "Expiration Date"), subject to extension
pursuant to Section 2.2(e) (the "Exercise Period"), Holder may exercise this
Warrant, on any Business Day, for all or any part of the Warrant Stock.

      2.2. Exercise Notice; Delivery of Certificates.

      (a) In order to exercise this Warrant, Holder shall deliver (which such
delivery may, at Holder's option, be by facsimile) to Company at its principal
office designated by Company in Section 14.2, a duly executed written notice of
Holder's election to exercise this Warrant, specifying the number of shares of
Warrant Stock to be purchased, in substantially the form attached hereto as
Exhibit A (the "Subscription Notice").

      (b) Upon receipt of a Subscription Notice, Company shall, as promptly as
practicable, and in any event within five (5) Business Days, subject to receipt
of any necessary regulatory approvals (including expiration of any applicable
waiting period), thereafter, deliver to Holder a duly executed certificate or
certificates representing the aggregate number of full shares of Warrant Stock
issuable upon such exercise, together with cash in lieu of any fraction of a
share, as hereinafter provided. Such stock certificate or certificates shall be
in such denominations and registered in the name designated in the Subscription
Notice, subject to Article IX.

                                     - 5 -

<PAGE>

      (c) In addition, as soon as practicable after the delivery of a
Subscription Notice, but subject to the receipt of any necessary regulatory
approvals (including expiration of any applicable waiting period), Holder shall
deliver in person, by certified mail or courier, to Company at the
aforementioned address, (i) if Holder has elected pursuant to the applicable
Subscription Notice to make payment of the Warrant Price pursuant to Section
2.3(a), such payment and (ii) this Warrant.

      (d) Upon the date required for issuance of the applicable shares of
Warrant Stock pursuant to Section 2.2(b) and receipt of any payment required
pursuant to Section 2.2(c), Holder or any other Person so designated in the
applicable Subscription Notice shall be deemed to have become a holder of record
of the applicable Warrant Stock for all purposes. If this Warrant shall have
been exercised in part, Company shall deliver to Holder a new Warrant evidencing
the rights of Holder to purchase the remaining shares of Warrant Stock issuable
upon exercise of this Warrant, which new Warrant shall in all other respects be
identical with this Warrant, or appropriate notation may be made on this Warrant
and the same returned to Holder.

      (e) If in connection with the exercise of a Warrant or acquisition of
Warrant Stock by Holder, any regulatory approval shall be required, including
expiration of any applicable waiting period, then, if the Warrant is exercised
prior to such approval, the Expiration Date shall be extended while any such
regulatory approval or waiting period is pending. Without limiting the
foregoing, Company hereby acknowledges that the exercise of this Warrant by
Holder may subject Company and/or Holder to the filing requirements of the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (the "HSR
Act"). If on or before the expiration Date, Holder has sent the Subscription
Notice to Company and Holder has not been able to complete the exercise of this
Warrant prior to the Expiration Date because of restrictions under the HSR Act,
Holder shall be entitled to complete the process of exercising this Warrant in
accordance with the procedures contained herein notwithstanding the fact that
completion of the exercise of this Warrant would take place after the Expiration
Date.

      2.3. Payment of Warrant Price: Net Issue Exercise

      (a) Payment of the Warrant Price shall be made at the option of Holder by
(i) cash, by check or by wire transfer or (ii) cancellation by Holder of
indebtedness of Company to Holder; or (iii) any combination thereof.

      (b) In lieu of the payment methods set forth in Section 2.3(a) above,
Holder may elect to exchange all or part of the Warrant for shares of Warrant
Stock equal to the value of the amount of the Warrant being exchanged on the
date of exchange. All references in this Warrant to an "exercise" of the Warrant
shall include a net issue exercise pursuant to this Section 2.3(b). If Holder
elects to exchange all or part of the Warrant as provided in this Section
2.3(b), Holder shall tender to Company the Warrant for the amount being
exchanged, along with a Subscription Notice indicating Holder's election to
exchange all or part of the Warrant, and Company shall issue to Holder the
number of shares of Warrant Stock computed using the following formula:

                                     - 6 -

<PAGE>

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

      Where

      X = number of shares of Warrant Stock to be issued to Holder upon
exercise;

      Y= total number of shares of Warrant Stock purchasable under the Warrant
(or, if only a portion, the amount of Warrant Stock for which the Warrant is
being exchanged);

      A = Current Market Price of one share of Warrant Stock; and

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

      2.4. Payment of Taxes. Company shall pay all expenses, taxes and other
governmental charges with respect to the issue or delivery of the Warrant Stock.
Company shall not be required, however, to pay any transfer tax imposed in
connection with the issue of any certificate for shares of Warrant Stock in any
name other than that of Holder.

      2.5. Fractional Shares. Company shall not be required to issue a
fractional share of Warrant Stock upon exercise of any Warrant. As to any
fraction of a share which Holder of one or more Warrants would otherwise be
entitled to purchase upon such exercise, Company shall pay a cash adjustment in
respect of such fractional share in an amount equal to the same fraction of the
Current Market Price per share of Warrant Stock on the date of exercise.

III. TRANSFER, DIVISION AND COMBINATION

      3.1. Transfer. Subject to compliance with Article IX of this Warrant,
Company shall register any Transfer of this Warrant and all rights hereunder, in
whole or in part, on the books of Company to be maintained for such purpose,
upon surrender by Holder of this Warrant at the principal office of Company
referred to in Section 14.2, together with a duly executed written assignment of
this Warrant substantially in the form of Exhibit B hereto and funds sufficient
to pay any transfer taxes payable upon the making of such Transfer. Promptly
following such surrender and, if required, such payment, Company shall at its
expense, subject to Article IX, execute and deliver a new Warrant or Warrants in
the name of the assignee or assignees and in the denomination specified in such
instrument of assignment, and shall issue to the assignor a new Warrant
evidencing the portion of this Warrant not so assigned, and this Warrant shall
promptly be cancelled. A Warrant, if properly assigned in compliance with
Article IX, may be exercised by a new Holder for the purchase of shares of
Series D Preferred Stock without having a new Warrant issued.

      3.2. Division and Combination. Subject to Article IX, this Warrant may be
divided or combined with other Warrants upon presentation hereof at the
aforesaid office or agency of Company, together with a duly executed written
notice specifying the names and denominations in which new Warrants are to be
issued. Subject to compliance with Section 3.1

                                     - 7 -

<PAGE>

and with Article IX as to any Transfer which may be involved in such division or
combination, Company shall execute and deliver a new Warrant or Warrants in
exchange for the Warrant or Warrants to be divided or combined in accordance
with such notice.

      3.3. Maintenance of Books. Company agrees to maintain, at its office
referred to in Section 14.2, books for the registration of Transfer of the
Warrants.

IV. ADJUSTMENTS

      The number of shares of Warrant Stock for which this Warrant is
exercisable, and the Exercise Price at which such shares may be purchased upon
exercise of this Warrant, shall be subject to adjustment from time to time as
set forth in this Article IV.

      4.1. Adjustments Upon Mandatory Conversion of Series D Preferred Stock.
Upon any mandatory conversion of the Series D Preferred Stock pursuant to the
Company's Certificate of Incorporation, this Warrant shall cease to be
exercisable for shares of Series D Preferred Stock and shall become exercisable
for that number of shares of Common Stock into which the shares of Series D
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 D Preferred Stock purchasable hereunder immediately prior to
such mandatory conversion.

      4.2. Stock Dividends, Stock Splits, Subdivisions and Combinations. If at
any time Company shall:

      (a) take a record of the holders of Series D Preferred Stock for the
purpose of entitling them to receive a dividend payable in, or other
distribution of, Series D Preferred Stock,

      (b) subdivide or split its Outstanding shares of Series D Preferred Stock
into a larger number of shares of Series D Preferred Stock, or

      (c) combine or reclassify its Outstanding shares of Series D Preferred
Stock into a smaller number of shares of Series D Preferred Stock;

then, in each of cases (a), (b) and (c) above, (i) the number of shares of
Warrant Stock for which this Warrant is exercisable immediately after the
occurrence of any such event shall be adjusted to equal the number of shares of
Warrant Stock which a record holder of the same number of shares of Warrant
Stock for which this Warrant is exercisable immediately prior to the occurrence
of such event or the record date therefor, whichever is earlier, would own or be
entitled to receive after the happening of such event, and (ii) the Exercise
Price shall be adjusted to equal (A) the Exercise Price multiplied by the number
of shares of Warrant Stock for which this Warrant is exercisable immediately
prior to the adjustment divided by (B) the number of shares of Warrant Stock for
which this Warrant is exercisable immediately after such adjustment.

                                     - 8 -

<PAGE>

Upon any mandatory conversion of the Series D Preferred Stock as provided in
Section 4.1, each reference to Series D Preferred Stock in this Section 4.2
shall be deemed to be Common Stock.

      4.3. Certain Other Distributions and Adjustments. If at any time Company
shall take a record of the holders of its Series D Preferred Stock for the
purpose of entitling them to receive a dividend or other distribution, or shall
in any manner declare, order, pay or make a dividend or other distribution
(including, without limitation, any distribution of stock or other securities,
debt or property or rights or warrants to subscribe for securities of Company or
any of its Subsidiaries by way of dividend or spin-off or any other assets) on
its Series D Preferred Stock, other than dividends or distributions of shares of
Series D Preferred Stock which are referred to in Section 4.2, then and in each
such case, (a) the number of shares of Warrant Stock for which this Warrant is
exercisable shall be adjusted to equal the number of shares of Series D
Preferred Stock which a record holder of the same number of shares of Warrant
Stock for which this Warrant is exercisable immediately prior to the occurrence
of such event would own or be entitled to receive after the happening of such
event, and (b) the Exercise Price to be in effect after such record date shall
be determined by multiplying (1) the Exercise Price in effect immediately prior
to such record date by (2) a fraction, the numerator of which shall be the
Exercise Price in effect immediately prior to such record date less the fair
market value (as determined in good faith by the Company's Board) of such
dividend or distribution per share of Series D Preferred Stock and the
denominator of which shall be such the Exercise Price in effect immediately
prior to such record date.

      4.4. Antidilution. It is understood and agreed that in the event of an
antidilution adjustment affecting any Warrant Shares after the date hereof, the
Holder will be entitled to the benefits of such adjustment upon exercise of this
Warrant.

      4.5. Organic Change. In case of any Organic Change, Holder shall have the
right thereafter to receive, upon exercise of the Warrant, in lieu of the
Warrant Stock issuable upon such exercise prior to consummation of such Organic
Change, the kind and amount of shares of stock, other securities, cash and
property receivable (including cash, and including any right to select the
consideration so receivable) upon the consummation of such Organic Change by a
holder of that number of shares of Warrant Stock into which the Warrant was
exercisable immediately prior to such Organic Change (including, on a pro rata
basis, the cash, securities or property received by holders of Series D
Preferred Stock in any tender or exchange offer that is a step in such Organic
Change), assuming such holder of Series D Preferred Stock is not a Person with
which Company consolidated or into which Company merged or which merged into
Company or to which such sale or transfer was made, as the case may be, or an
affiliate of such a Person. In case securities or property other than Series D
Preferred Stock shall be issuable or deliverable upon conversion as aforesaid,
then all references in this Article IV shall be deemed to apply, so far as
appropriate and nearly as may be, to such other securities or property. In case
of any Organic Change, the successor or acquiring corporation (if other than
Company) shall expressly assume the due and punctual observance and performance
of each covenant and condition of this Warrant to be performed and observed by
Company and all the obligations and liabilities hereunder, subject to such
modifications as may be deemed appropriate (as determined

                                     - 9 -

<PAGE>

by resolution of the Board) in order to provide for adjustments of shares of
Warrant Stock for which this Warrant is exercisable which shall be as nearly
equivalent as practicable to the adjustments provided for in this Article IV.
The foregoing provisions of this Section 4.5 shall similarly apply to successive
Organic Changes.

      4.6. Qualified Initial Public Offering. Upon the completion of any
Qualified Initial Public Offering, the provisions of this Section IV shall be
extinguished and of no further force or effect.

V. NOTICES TO WARRANT HOLDERS

      5.1. Notice of Adjustments. Whenever an adjustment to this Warrant is made
pursuant to Article IV, Company shall promptly deliver to Holder (by facsimile
and by either first class mail, postage prepaid or overnight delivery) a
certificate from the Company setting forth, in reasonable detail, the event
requiring the adjustment and the method by which such adjustment was calculated,
specifying the number of shares of Warrant Stock for which this Warrant is
exercisable and (if such adjustment was made pursuant to Section 4.5) describing
the number and kind of any other shares of stock or other securities or property
for which this Warrant is exercisable, and any change in Exercise Price, after
giving effect to such adjustment or change. Company shall keep in the office or
agency designated pursuant to Section 14.2 copies of all such certificates and
cause the same to be available for inspection at said office during normal
business hours by any Holder or any prospective purchaser of a Warrant
designated by a Holder thereof. Any adjustment to this Warrant pursuant to
Article IV shall be automatic and shall occur without any action on the part of
Company or Holder, and any failure by Company to comply with the terms of this
Section 5.1 (including any error made by Company in the calculations described
above) shall have no effect on such automatic adjustment. Notwithstanding any
other provision of this Section 5.1, Holder shall retain the right to contest
the adjustment calculations provided by Company described above, and such
calculations shall not be entitled to any presumption of accuracy in any case,
action or other proceeding to determine the actual amount of adjustment required
by Article IV.

      5.2. Notice of Corporate Action. If at any time

      (a) Company shall take a record of the holders of its Series D Preferred
Stock for the purpose of entitling them to receive a dividend or other
distribution, or any right to subscribe for or purchase any evidences of its
indebtedness, any shares of stock of any class or any other securities or
property, or to receive any other right; or

      (b) there shall be approved by the Board any capital reorganization of
Company, any reclassification or recapitalization of the capital stock of
Company or any consolidation or merger of Company with, or any sale, transfer or
other disposition of all or substantially all the property, assets or business
of Company to, another corporation, including without limitation any such event
constituting an Organic Change; or

                                     - 10 -

<PAGE>

      (c) there shall be a voluntary or involuntary dissolution, liquidation or
winding up of Company;

then, in any one or more of such cases, Company shall give to Holder (i) at
least twenty (20) days' prior written notice of the date on which a record date
shall be selected in respect of such event and (ii) in the case of any such
event, at least sixty (60) days' prior written notice of the date when the same
shall take place; provided that in the case of an Organic Change to which
Section 4.5 applies, Company shall give at least thirty (30) days' written
notice as aforesaid. Such notice shall also specify (i) the date on which the
holders of Series D Preferred Stock shall be entitled to any such dividend,
distribution or right, and the amount and character thereof and (ii) the date on
which any such reorganization, reclassification, merger, consolidation, sale,
transfer, disposition, dissolution, liquidation or winding up is to take place
and the time, if any such time is to be fixed, as of which the holders of Series
D Preferred Stock shall be entitled to exchange their shares of Series D
Preferred Stock for securities or other property deliverable upon such event.

VI. NO IMPAIRMENT

      Company shall not by any action, including, without limitation, amending
its Certificate of Incorporation or through any reorganization, transfer of
assets, consolidation, merger, dissolution, issuance or sale of securities or
any other voluntary action, 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 actions as
may be necessary or appropriate to protect the rights of Holder against
impairment. Without limiting the generality of the foregoing, Company will take
all such action as may be necessary or appropriate in order that Company may
upon the exercise of this Warrant validly and legally issue fully paid and
nonassessable shares of Series D Preferred Stock that are not subject to
preemptive rights, including taking such action as is necessary for the Exercise
Price to be not less than the par value of the shares of Series D Preferred
Stock issuable upon exercise of this Warrant. Company will obtain all such
authorizations, exemptions or consents from any Governmental Authority having
jurisdiction thereof, or any other Person, as may be necessary to enable Company
to perform its obligations under this Warrant. Without limiting the foregoing,
Company will make any filings under the HSR Act required in order to perform its
obligations under this Warrant.

VII. RESERVATION AND AUTHORIZATION OF SERIES D PREFERRED STOCK AND COMMON STOCK

      From and after the date of this Warrant, Company shall at all times
reserve and keep available for issue upon the exercise of this Warrant such
number of its authorized but unissued shares of Series D Preferred Stock and the
Common Stock issuable upon the conversion thereof, and the Common Stock issuable
hereunder, as the case may be, as will be sufficient to permit the exercise in
full of this Warrant. All shares of Warrant Stock which shall be so issuable,
when issued upon exercise of this Warrant and payment therefor in accordance
with the

                                     - 11 -

<PAGE>

terms of this Warrant, shall be duly and validly issued and fully paid and
nonassessable, and not subject to preemptive rights.

VIII. TAKING OF RECORD; STOCK AND WARRANT TRANSFER OF BOOKS

      In the case of all dividends or other distributions by Company to the
holders of its Series D Preferred Stock with respect to which any provision of
Article IV refers to the taking of a record of such holders, Company will take
such record as of the close of business on a Business Day. Company will not at
any time, except upon dissolution, liquidation or winding up of Company, close
its stock transfer books or Warrant transfer books so as to prevent or delay the
exercise or transfer of this Warrant.

IX. RESTRICTIONS ON TRANSFERABILITY

      The Warrant and the Warrant Stock shall not be transferred, hypothecated
or assigned before satisfaction of the conditions specified in this Article IX.
Holder, by acceptance of this Warrant, agrees to be bound by the provisions of
this Article IX.

      9.1. Restrictive Legends.

      (a) Except as otherwise provided in this Article IX, each certificate for
Warrant Stock initially issued upon the exercise of this Warrant shall be
stamped or otherwise imprinted with a legend in substantially the following
form:

      "THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
      THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, OFFERED FOR
      SALE, PLEDGED HYPOTHECATED OR OTHERWISE TRANSFERRED IN VIOLATION OF SUCH
      ACT OR THE RULES AND REGULATIONS THEREUNDER."

      (b) Except as otherwise provided in this Article IX, each Warrant shall be
stamped or otherwise imprinted with a legend in substantially the following
form:

      "THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
      AMENDED, AND MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED HYPOTHECATED OR
      OTHERWISE TRANSFERRED IN VIOLATION OF SUCH ACT, THE RULES AND REGULATIONS
      THEREUNDER OR THE PROVISIONS OF THIS WARRANT."

      9.2. Notice of Proposed Transfers. Prior to or promptly following any
Transfer of any Warrants or any shares of restricted Warrant Stock, the holder
of such Warrants or restricted Warrant Stock shall give written notice to
Company of such Transfer. Each certificate,

                                     - 12 -

<PAGE>

if any, evidencing such shares of restricted Warrant Stock issued upon such
Transfer shall bear the restrictive legend set forth in Section 9.1(a), and each
Warrant issued upon such Transfer shall bear the restrictive legend set forth in
Section 9.1(b), unless such restrictive legend is not required pursuant to
Section 9.3.

      9.3. Termination of Restrictions. The restrictions and requirements
imposed by this Article IX shall terminate as to any particular Warrant or share
of Warrant Stock (a) when and so long as such security shall have been
effectively registered under the Securities Act, (b) when Company shall have
received an opinion of counsel (which may be Holder's inside corporate counsel)
that such security may be transferred without registration thereof under the
Securities Act or (c) a sale of such security is made pursuant to SEC Rule 144.
Whenever the restrictions imposed by Article IX shall terminate as to this
Warrant, as hereinabove provided, Holder shall be entitled to receive from
Company, at the expense of Company, a new Warrant without the restrictive legend
set forth in Section 9.1(b). Whenever the restrictions imposed by this Article
IX shall terminate as to any share of Warrant Stock, as hereinabove provided,
the holder thereof shall be entitled to receive from Company, at the expense of
Company, a new certificate representing such Series D Preferred Stock not
bearing the restrictive legend set forth in Section 9.1(a).

X. SUPPLYING INFORMATION

      Company shall cooperate with each Holder of a Warrant and each holder of
Warrant Stock in supplying such information as may be reasonably requested with
respect to the Company and its businesses and operations (including reasonable
access to management and operational personnel): (i) in connection with such
Holder evaluating if, and to what extent, it shall exercise the Warrant, and
(ii) in order for such Holder to complete and file any information reporting
forms presently or hereafter required by the SEC or any other governmental
entity as a condition to the availability of an exemption from the registration
requirements of the Securities Act for the sale of any Warrant or share of
Warrant Stock. Company shall also supply such information as may be reasonably
necessary for such Holder to comply with tax and other applicable laws and
applicable financial reporting and accounting rules standards.

XI. LOSS OR MUTILATION

      Upon receipt by Company from any Holder of evidence reasonably
satisfactory to it of the ownership of and the loss, theft, destruction or
mutilation of this Warrant and indemnity reasonably satisfactory to it (it being
understood that the written agreement of Holder shall be sufficient indemnity),
and in case of mutilation upon surrender and cancellation hereof, Company will
execute and deliver in lieu hereof a new Warrant of like tenor to such Holder;
provided, in the case of mutilation, no indemnity shall be required if this
Warrant in identifiable form is surrendered to Company for cancellation.

                                     - 13 -

<PAGE>

XII. NO STOCKHOLDER RIGHTS; LIMITATION OF LIABILITY

      No provision hereof shall be deemed to impose any rights or obligations
upon Holder as a stockholder in Company prior to Holder's exercise of this
Warrant and the issuance to Holder of Warrant Shares. Without limiting the
foregoing, no provision hereof and no enumeration herein of the rights or
privileges of Holder hereof, shall give rise to any liability of such Holder for
the purchase price of any Warrant Stock or as a stockholder of Company, whether
such liability is asserted by Company, by creditors of Company or by any third
party.

XIII. REPRESENTATIONS AND WARRANTIES OF COMPANY

      Company hereby represents and warrants to Holder that the statements in
the following paragraphs of this Article XIII are true and correct (a) as of the
date hereof and (b) except where any such representation and warranty relates
specifically to an earlier date, as of the date of any exercise of this Warrant.

      13.1. Corporate Organization and Authority. Company (a) is a corporation
duly organized, validly existing, and in good standing in its jurisdiction of
incorporation, (b) has the corporate power and authority to own and operate its
properties and to carry on its business as now conducted and as proposed to be
conducted; and (c) is qualified as a foreign corporation in all jurisdictions
where such qualification is required.

      13.2. Corporate Power. Company has all requisite legal and corporate power
and authority to execute, issue and deliver the Warrant, to issue the Series D
Preferred Stock issuable upon exercise or conversion of the Warrant, to issue
the Common Stock issuable upon the conversion of the Series D Preferred Stock,
and to carry out and perform its obligations under the Warrant and any related
agreements.

      13.3. Authorization; Enforceability. All corporate action on the part of
Company, its officers, directors and shareholders necessary for the
authorization, execution, delivery and performance of its obligations under this
Warrant and for the authorization, issuance and delivery of the Warrant and the
Warrant Stock issuable upon exercise of the Warrant has been taken and this
Warrant constitutes the legally binding and valid obligation of Company
enforceable in accordance with its terms.

      13.4. Valid Issuance of Warrant and Warrant Stock. The Warrant has been
validly issued and is free of restrictions on transfer other than restrictions
on transfer set forth herein, in the Investor Rights Agreement and under
applicable state and federal securities laws. The Warrant Stock issuable upon
conversion of this Warrant, when issued, sold and delivered in accordance with
the terms of this Warrant for the consideration expressed herein, will be duly
and validly issued, fully paid and nonassessable, and will be free of
restrictions on transfer other than restrictions on transfer under this Warrant,
in the Investor Rights Agreement and under applicable state and federal
securities laws. Subject to applicable restrictions on transfer, the issuance
and delivery of the Warrant and the Warrant Stock issuable upon conversion of
the Warrant are not subject to any preemptive or other similar rights or any
liens or encumbrances

                                     - 14 -

<PAGE>

except as specifically set forth in the Certificate of Incorporation, the
Investor Rights Agreement or this Warrant. The offer, sale and issuance of the
Warrant and Warrant Stock, as contemplated by this Warrant, are exempt, from the
prospectus and registration requirements of applicable United States federal and
state security laws, and neither Company nor any authorized agent acting on its
behalf has or will take any action hereafter that would cause the loss of such
exemption.

      13.5. No Conflict with Other Instruments. The execution, delivery, and
performance of this Warrant will not result in any violation of, be in conflict
with, or constitute a default under, with or without the passage of time or the
giving of notice (a) any provision of the Certificate of Incorporation or
by-laws; (b) any provision of any judgment, decree, or order to which Company is
a party or by which it is bound or an event which results in the creation of any
material lien, charge or encumbrance upon any material assets of Company; (c)
any contract, obligation, or commitment to which Company is a party or by which
it is bound; or (d) any statute, rule, or governmental regulation applicable to
Company.

      13.6. Capitalization. As of recent date, the authorized capital stock of
Company consists of 546,992,837,337 shares of Common Stock, $0.001 par value, of
which 2,135,312 were issued and outstanding, and 149,275,350 shares of Preferred
Stock, $0.001 par value, of which 145,773,877 were issued and outstanding. The
outstanding shares have been duly authorized and validly issued (including,
without limitation, issued in compliance with applicable federal and state
securities laws), are fully paid and nonassessable. Company has reserved
455,655,829,025 shares of Common Stock for issuance upon conversion of the
Preferred Stock. Company has delivered to Holder a capitalization table showing
all outstanding warrants, options, conversion privileges, preemptive rights or
other rights or agreements to purchase or otherwise acquire or issue any equity
securities or Convertible Securities of Company. Except as set forth on such
capitalization table, the Company has not authorized the issuance of any of the
aforesaid rights to acquire securities of Company as of the date hereof.

      13.7. Governmental Consents. No consent, approval, order or authorization
of, or registration, qualification, designation, declaration or filing with, any
federal, state or local governmental authority on the part of Company is
required in connection with the offer, sale or issuance of the Warrant (and the
Warrant Stock issuable upon conversion of the Shares), or the consummation of
any other transaction contemplated hereby, except for the following: (a) the
filing of a notice on Form D under the Securities Act and (b) the compliance
with other applicable state securities laws, which compliance will have occurred
within the appropriate time periods therefor. The offer, sale and issuance of
the Warrant and the shares of Warrant Stock in conformity with the terms of this
Warrant are exempt from the registration requirements of the Securities Act and
any applicable state laws.

      13.8. Registration Rights. Attached hereto as Annex I is the current
version of the Investor Rights Agreement which lists all rights (including
piggyback registration rights) to have any transaction or proposed transaction
involving securities of Company registered with the SEC or any other
governmental authority as of the date of issuance of this Warrant.

                                     - 15 -

<PAGE>

XIV. MISCELLANEOUS

      14.1. Nonwaiver and Expenses. No course of dealing or any delay or failure
to exercise any right hereunder on the part of Holder shall operate as a waiver
of such right or otherwise prejudice Holder's rights, powers or remedies. If
Company fails to make, when due, any payments provided for under this Warrant,
or fails to comply with any other provision of this Warrant, Company shall pay
to Holder such amounts as shall be sufficient to cover any costs and expenses
including, but not limited to, reasonable attorneys' fees, including those of
appellate proceedings, incurred by Holder in collecting any amounts due pursuant
hereto or in otherwise enforcing any of its rights, powers or remedies
hereunder.

      14.2. Notices. All notices and communications to be given or made under
this Warrant shall be in writing and delivered by hand-delivery, registered
first class mail (return receipt requested), facsimile, or air courier
guaranteeing overnight delivery, addressed as follows, or to such other Person
or address as the party named below may designate by notice:

      (a) If to any Holder or holder of Warrant Stock, at its last known address
appearing on the books of Company maintained for such purpose and any other
address sent by such Holder to Company in compliance with this Section 14.2.

      (b) If to Company at

          PTC THERAPEUTICS, INC.
          100 CORPORATE CT.
          MIDDLESEX BUSINESS CENTER
          SOUTH PLAINFIELD, NJ 07080
          ATTN:  MARK E. BOULDING

Each such notice or other communication shall be deemed to have been duly given
or served on the date on which personally delivered, with receipt acknowledged,
or confirmed by telecopy answerback with respect to notice by telecopy, or three
Business Days after the same shall have been deposited in the United States
mail.

      14.3. Successors and Assigns. Subject to the provisions of Section 3.1 and
Article IX, this Warrant and the rights evidenced hereby shall inure to the
benefit of and be binding upon the successors of Company and the successors and
assigns of Holder. The provisions of this Warrant are intended to be for the
benefit of all Holders from time to time of this Warrant and shall be
enforceable by any such Holder. No other Person shall have any right, benefit or
obligation under this Warrant.

      14.4. Amendment. No amendment or waiver of any provision of this Warrant
or any other Warrant shall be effective without the written consent of Company
and all Holders,

      14.5. Severability. If one or more provisions of this Warrant are held to
be unenforceable to any extent under applicable law, such provision shall be
interpreted as if it were

                                     - 16 -

<PAGE>

written so as to be enforceable to the maximum extent permitted by law so as to
effectuate the parties' intent to the maximum extent, and the balance of this
Warrant shall be interpreted as if such provision were so excluded and shall be
enforceable in accordance with its terms to the maximum extent permitted by law.

      14.6. Section and Other Headings. The section and headings contained in
this Warrant are for the convenience only and shall not affect the meaning or
interpretation of this Warrant.

      14.7. Governing Law. This Warrant shall be governed by, construed and
enforced in accordance with the laws of the State of New York, without regard to
the conflict of law principles of such state.

      14.8. WAIVER OF JURY TRIAL. EACH OF THE PARTIES HERETO HEREBY WAIVES TO
THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY RIGHT IT MAY HAVE TO A TRIAL
BY JURY IN RESPECT OF ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING OUT OF,
UNDER OR IN CONNECTION WITH THIS WARRANT OR THE WARRANT SHARES.

      14.9. CHOICE OF FORUM. EACH OF THE PARTIES HERETO IRREVOCABLE SUBMITS TO
THE EXCLUSIVE JURISDICTION OF (A) THE SUPREME COURT OF THE STATE OF NEW YORK,
NEW YORK COUNTY, AND (B) THE UNITED STATES DISTRICT COURT FOR THE SOUTHERN
DISTRICT OF NEW YORK, FOR THE PURPOSES OF ANY SUIT, ACTION OR OTHER PROCEEDING
ARISING OUT OF THIS WARRANT OR ANY TRANSACTION CONTEMPLATED HEREBY (AND EACH
AGREES THAT NO SUCH ACTION, SUIT OR PROCEEDING RELATING TO THIS WARRANT SHALL BE
BROUGHT BY IT IN SUCH COURTS). EACH OF THE PARTIES HERETO IRREVOCABLE AND
UNCONDITIONALLY WAIVE (AND AGREES NOT TO PLEAD OR CLAIM), ANY OBJECTION TO THE
LAYING OF VENUE OF ANY ACTION, SUIT OR PROCEEDING ARISING OUT OF THIS WARRANT OR
THE WARRANT SHARES IN (A) THE SUPREME COURT OF THE STATE OF NEW YORK, NEW YORK
COUNTY, AND (B) THE UNITED STATES DISTRICT COURT FOR THE SOUTHERN DISTRICT OF
NEW YORK OR THAT ANY SUCH ACTION, SUIT OR PROCEEDING BROUGHT IN ANY SUCH COURT
HAS BEEN BROUGHT IN AN INCONVENIENT FORUM.

      14.10. Remedies. Each Holder, in addition to being entitled to exercise
all rights granted by law, including recovery of damages, will be entitled to
specific performance of its rights under this Warrant. Company agrees that
monetary damages would not be adequate compensation for any loss incurred by
reason of a breach by it of the provisions of this Warrant and hereby agrees to
waive the defense in any action for specific performance that a remedy at law
would be adequate. In any action or proceeding brought to enforce any provision
of this Warrant or where any provision hereof is validly asserted as a defense,
the successful party shall be entitled to recover reasonable attorneys' fees in
addition to any other available remedy.

      14.11. Counterparts. For the convenience of the parties, any number of
counterparts of this Warrant may be executed by the parties hereto and each such
executed counterpart shall be, and shall be deemed to be, an original
instrument.

                         [SIGNATURES BEGIN ON NEXT PAGE]

                                     - 17 -

<PAGE>

      IN WITNESS WHEREOF, Company has caused this Warrant to be duly executed by
an authorized officer.

Dated:

                             PTC THERAPEUTICS, INC.

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

ACKNOWLEDGED AND ACCEPTED BY:

GENERAL ELECTRIC CAPITAL CORPORATION

By: DIANE EARLE
    _____________________
    Name:  Diane Earle
    Title: Senior Vice President

                                     - 18 -

<PAGE>

                                                                     Exhibit 4.7

                                    EXHIBIT A

                               SUBSCRIPTION NOTICE

                 [To be executed only upon exercise of Warrant]

      The undersigned registered owner of this Warrant irrevocably exercises
this Warrant for the purchase of ________ Shares of Series D Preferred Stock of
PTC THERAPEUTICS, INC. and herewith makes payment therefor, all at the price and
on the terms and conditions specified in this Warrant (including without
limitation the conditions set forth in Section 2.1 hereof relating to required
regulatory approvals) and requests that certificates for the shares of Warrant
Stock hereby purchased (and any securities or other property issuable upon such
exercise, including any cash in lieu of fractional shares) be issued in the name
of and delivered to ______________ whose address is __________________ and, if
such shares of Warrant Stock shall not include all of the shares of Warrant
Stock issuable as provided in this Warrant, that a new Warrant of like tenor and
date for the balance of the shares of Warrant Stock issuable hereunder be
delivered to the undersigned.

      [_____] The undersigned shall tender payment in the following
form:_________________________.

      [_____] The undersigned hereby elects the net issue exercise option
pursuant to Section 2.3(b) of the Warrant, and accordingly requests delivery of
a net of____________ shares of Series D Preferred Stock.

                             _________________________
                             (Name of Registered Owner)

                             _________________________
                             (Signature of Registered Owner)

                             _________________________
                             (Street Address)

                             _________________________
                             (City) (State) (Zip Code)

NOTICE: The signature on this subscription must correspond with the name as
        written upon the face of the Warrant in every particular, without
        alteration or enlargement or any change whatsoever.

<PAGE>

                                                                     Exhibit 4.7

                                    EXHIBIT B

                                 ASSIGNMENT FORM

      FOR VALUE RECEIVED the undersigned registered owner of this Warrant hereby
sells, assigns and transfers unto the Assignee named below the rights of the
undersigned under this Warrant, with respect to the number of shares of Warrant
Stock set forth below:

Name and Address of Assignee                      No. of Shares of Warrant Stock

and does hereby irrevocably constitute and appoint ___________________________
attorney-in-fact to register such transfer on the books of PTC THERAPEUTICS,
INC. maintained for the purpose, with full power of substitution in the
premises.

Dated:                             Print Name:
                                               _______________________

                                   Signature:
                                               _______________________
                                   Witness:
                                               _______________________

NOTICE: The signature on this assignment must correspond with the name as
        written upon the face of the Warrant in every particular, without
        alteration or enlargement or any change whatsoever.

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