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                                                                     EXHIBIT 4.2

The following is a form of warrant that ArQule assumed in connection with its
acquisition of Camitro Corporation, a California corporation, on January 29,
2001. ArQule has assumed warrants to purchase a total of 14,585 shares of its
common stock at an exercise price of $4.70 per share. Silicon Valley Bank is the
holder of these warrants. The last of these warrants expire on May 2, 2007.

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THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT
OR PURSUANT TO RULE 144 OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE
CORPORATION AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.

                            WARRANT TO PURCHASE STOCK

Corporation:  CAMITRO CORPORATION, a California corporation
              -------------------    ----------
Number of Shares:
Class of Stock: Series B Preferred
Initial Exercise Price: $________per share
Issue Date:
Expiration Date:

     THIS WARRANT CERTIFIES THAT, for the agreed upon value of $1.00 and for
other good and valuable consideration, SILICON VALLEY BANK ("Holder") is
entitled to purchase the number of fully paid and nonassessable shares of the
class of securities (the "Shares") of the corporation (the "Company") at the
initial exercise price per Share (the "Warrant Price") all as set forth above
and as adjusted pursuant to Article 2 of this Warrant, subject to the provisions
and upon the terms and conditions set forth in this Warrant.

ARTICLE 1. EXERCISE.

     1.1 METHOD OF EXERCISE. Holder may exercise this Warrant by delivering a
duly executed Notice of Exercise in substantially the form attached as Appendix
1 to the principal office of the Company. Unless Holder is exercising the
conversion right set forth in Section 1.2, Holder shall also deliver to the
Company a check for the aggregate Warrant Price for the Shares being purchased.

     1.2 CONVERSION RIGHT. In lieu of exercising this Warrant as specified in
Section 1.1, Holder may from time to time convert this Warrant, in whole or in
part, into a number of Shares determined by dividing (a) the aggregate fair
market value of the Shares or other securities otherwise issuable upon exercise
of this Warrant minus the aggregate Warrant Price of such Shares by (b) the fair
market value of one Share. The fair market value of the Shares shall be
determined pursuant to Section 1.3.

     1.3 FAIR MARKET VALUE. If the Shares are traded in a public market, the
fair market value of the Shares shall be the closing price of the Shares (or the
closing price of the Company's stock into which the Shares are convertible)
reported for the business day immediately before Holder delivers its Notice of
Exercise to the Company. If the Shares are not traded in a public market, the
Board of Directors of the Company shall determine fair market value in its
reasonable good faith judgment. The foregoing notwithstanding, if Holder advises
the Board of Directors in writing that Holder disagrees with such determination,
then the Company and Holder shall promptly agree upon a reputable investment
banking firm to undertake such valuation. If the valuation of such investment
banking firm is greater than that determined by the


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Board of Directors, then all fees and expenses of such investment banking firm
shall be paid by the Company. In all other circumstances, such fees and expenses
shall be paid by Holder.

     1.4 DELIVERY OF CERTIFICATE AND NEW WARRANT. Promptly after Holder
exercises or converts this Warrant, the Company shall deliver to Holder
certificates for the Shares acquired and, if this Warrant has not been fully
exercised or converted and has not expired, a new Warrant representing the
Shares not so acquired.

     1.5 REPLACEMENT OF WARRANTS. On receipt of evidence reasonably satisfactory
to the Company of the loss, theft, destruction or mutilation of this Warrant
and, in the case of loss, theft or destruction, on delivery of an indemnity
agreement reasonably satisfactory in form and amount to the Company or, in the
case of mutilation, on surrender and cancellation of this Warrant, the Company
shall execute and deliver, in lieu of this Warrant, a new warrant of like tenor.

     1.6 ASSUMPTION UPON SALE, MERGER, OR CONSOLIDATION OF THE COMPANY.

          1.6.1. "ACQUISITION." For the purpose of this Warrant, "Acquisition"
means any sale, license, or other disposition of all or substantially all of the
assets of the Company, or any reorganization, consolidation, or merger of the
Company where the holders of the Company's securities before the transaction
beneficially own less than 50% of the outstanding voting securities of the
surviving entity after the transaction.

          1.6.2. ASSUMPTION OF WARRANT. Upon the closing of any Acquisition the
successor entity shall assume the obligations of this Warrant and this Warrant
shall be exercisable for the same securities, cash, and property as would be
payable for the Shares issuable upon exercise of the unexercised portion of this
Warrant as if such Shares were outstanding on the record date for the
Acquisition and subsequent closing. The Warrant Price shall be adjusted
accordingly.

ARTICLE 2. ADJUSTMENTS TO THE SHARES.

     2.1 STOCK DIVIDENDS, SPLITS, ETC. If the Company (i) declares or pays a
dividend on its common stock (or the Shares if the Shares are securities other
than common stock) payable in common stock, or other securities, or (ii)
subdivides the outstanding common stock into a greater amount of common stock,
or, if the Shares are securities other than common stock, subdivides the Shares
in a transaction that increases the amount of common stock into which the Shares
are convertible, then upon exercise of this Warrant, for each Share acquired,
Holder shall receive, without cost to Holder, the total number and kind of
securities to which Holder would have been entitled had Holder owned the Shares
of record as of the date the dividend or subdivision occurred.

     2.2 RECLASSIFICATION, EXCHANGE OR SUBSTITUTION. Upon any reclassification,
exchange, substitution, or other event that results in a change of the number
and/or class of the securities issuable upon exercise or conversion of this
Warrant, Holder shall be entitled to receive, upon exercise or conversion of
this Warrant, the number and kind of securities and property that Holder would
have received for the Shares if this Warrant had been exercised immediately
before such reclassification, exchange, substitution, or other event. Such an
event shall include


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any automatic conversion of the outstanding or issuable securities of the
Company of the same class or series as the Shares to common stock pursuant to
the terms of the Company's Articles of Incorporation upon the closing of a
registered public offering of the Company's common stock. The Company or its
successor shall promptly issue to Holder a new Warrant for such new securities
or other property. The new Warrant shall provide for adjustments which shall be
as nearly equivalent as may be practicable to the adjustments provided for in
this Article 2 including, without limitation, adjustments to the Warrant Price
and to the number of securities or property issuable upon exercise of the new
Warrant. The provisions of this Section 2.2 shall similarly apply to successive
reclassifications, exchanges, substitutions, or other events.

     2.3 ADJUSTMENTS FOR COMBINATIONS, ETC. If the outstanding shares are
combined or consolidated, by reclassification or otherwise, into a lesser number
of shares, the Warrant Price shall be proportionately increased.

     2.4 ADJUSTMENTS FOR DILUTING ISSUANCE. The Warrant Price and the number of
Shares issuable upon exercise of this Warrant or, if the Shares are Preferred
Stock, the number of shares of common stock issuable upon conversion of the
Shares, shall be subject to adjustment, from time to time in the manner set
forth in the Company's Articles (Certificate) of Incorporation. The provisions
set forth for the Shares in the Company's Articles (Certificate) of
Incorporation relating to the above in effect as of the Issue Date may not be
amended, modified or waived, without the prior written consent of Holder unless
such amendment, modification or waiver effects Holder in the same manner as they
effect all other shareholders of the Shares.

     2.5 NO IMPAIRMENT. The Company shall not, by amendment of its Articles of
Incorporation or through a reorganization, transfer of assets, consolidation,
merger, dissolution, issue, or sale of securities or any other voluntary action,
avoid or seek to avoid the observance or performance of any of the terms to be
observed or performed under this Warrant by the Company, but shall at all times
in good faith assist in carrying out of all the provisions of this Article 2 and
in taking all such action as may be necessary or appropriate to protect Holder's
rights under this Article against impairment. If the Company takes any action
affecting the Shares or its common stock other than as described above that
adversely affects Holder's rights under this Warrant, the Warrant Price shall be
adjusted upward in such a manner that the aggregate Warrant Price of this
Warrant is unchanged.

     2.6 FRACTIONAL SHARES. No fractional shares shall be issuable upon exercise
or conversion of the Warrant and the number of Shares to be issued shall be
rounded down to the nearest whole Share. If a fractional share interest arises
upon any exercise or conversion of the Warrant, the Company shall eliminate such
fractional share interest by paying Holder an amount computed by multiplying the
fractional interest by the fair market value of a full Share.

     2.7 CERTIFICATE AS TO ADJUSTMENTS. Upon each adjustment of the Warrant
Price, the Company at its expense shall promptly compute such adjustment, and
furnish Holder with a certificate of its Chief Financial Officer setting forth
such adjustment and the fact upon which such adjustment is based. The Company
shall, upon written request, furnish Holder a certificate setting forth the
Warrant Price in effect upon the date thereof and the series of adjustments
leading to such Warrant Price.


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ARTICLE 3. REPRESENTATIONS AND COVENANTS OF THE COMPANY.

     3.1 REPRESENTATIONS AND WARRANTIES. The Company hereby represents and
warrants to the Holder as follows:

          (a) The initial Warrant Price referenced on the first page of this
Warrant is not greater than the price per share at which the Shares were last
issued in an arms-length transaction in which at least $500,000 Shares were
sold.

          (b) All Shares which may be issued upon the exercise of the purchase
right represented by this Warrant, and all securities, if any, issuable upon
conversion of the Shares, shall, upon issuance, be duly authorized, validly
issued, fully paid and nonassessable, and free of any liens and encumbrances
except for restrictions on transfer provided for herein or under applicable
federal and state securities laws.

          (c) The Capitalization table attached hereto is true and correct.

     3.2 NOTICE OF CERTAIN EVENTS. If the Company proposes at any time (a) to
declare any dividend or distribution upon its common stock, whether in cash,
property, stock, or other securities and whether or not a regular cash dividend;
(b) to offer for subscription pro rata to the holders of any class or series of
its stock any additional shares of stock of any class or series or other rights;
(c) to effect any reclassification or recapitalization of common stock; (d) to
merge or consolidate with or into any other corporation, or sell, lease,
license, or convey all or substantially all of its assets, or to liquidate,
dissolve or wind up; or (e) offer holders of registration rights the opportunity
to participate in an underwritten public offering of the Company's securities
for cash, then, in connection with each such event, the Company shall give
Holder (1) at least 20 days prior written notice of the date on which a record
will be taken for such dividend, distribution, or subscription rights (and
specifying the date on which the holders of common stock will be entitled
thereto) or for determining rights to vote, if any, in respect of the matters
referred to in (c) and (d) above; (2) in the case of the matters referred to in
(c) and (d) above at least 20 days prior written notice of the date when the
same will take place (and specifying the date on which the holders of the common
stock will be entitled to exchange their common stock for securities or other
property deliverable upon the occurrence of such event); and (3) in the case of
the matter referred to in (e) above, the same notice as is given the holders of
such registration rights.

     3.3 INFORMATION RIGHTS. So long as the Holder holds this Warrant and/or any
of the Shares, the Company shall deliver to the Holder (a) promptly after
mailing, copies of all notices or other written communications to the
shareholders of the Company, (b) within 90 days after the end of each fiscal
year of the Company, the annual audited financial statements of the Company
certified by independent public accountants of recognized standing and (c) such
other financial statements required under and in accordance with any loan
documents between Holder and the Company (or if there are no such requirements
or if the subject loan(s) no longer are outstanding), then within 45 days after
the end of each of the first three quarters of each fiscal year, the Company's
quarterly, unaudited financial statements.


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     3.4 REGISTRATION UNDER SECURITIES ACT OF 1933, AS AMENDED. The Company
agrees that the Shares or, if the Shares are convertible into common stock of
the Company, such common stock, shall be subject to the registration rights set
forth in the Company's Investors' Rights Agreement or similar agreement. The
provisions set forth in Company's Investors' Rights Agreement or similar
agreement relating to the above in effect as of the Issue Date may not be
amended, modified or waived without the prior written consent of Holder unless
such amendment, modification or waiver effects Holder in the same manner as they
effect all other shareholders of the Shares.

ARTICLE 4. MISCELLANEOUS.

     4.1 TERM. This Warrant is exercisable, in whole or in part, at any time and
from time to time on or before the Expiration Date set forth above.

     4.2 LEGENDS. This Warrant and the Shares (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) shall be
imprinted with a legend in substantially the following form:

     THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
     AMENDED, AND MAY NOT BE SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN
     EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN
     OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE CORPORATION AND ITS
     COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED.

     4.3 COMPLIANCE WITH SECURITIES LAWS ON TRANSFER. This Warrant and the
Shares issuable upon exercise of this Warrant (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) may not be
transferred or assigned in whole or in part without compliance with applicable
federal and state securities laws by the transferor and the transferee
(including, without limitation, the delivery of investment representation
letters and legal opinions reasonably satisfactory to the Company, as reasonably
requested by the Company). The Company shall not require Holder to provide an
opinion of counsel if the transfer is to an affiliate of Holder or if there is
no material question as to the availability of current information as referenced
in Rule 144(c), Holder represents that it has complied with Rule 144(d) and (e)
in reasonable detail, the selling broker represents that it has complied with
Rule 144 (f), and the Company is provided with a copy of Holder's notice of
proposed sale.

     4.4 TRANSFER PROCEDURE. Subject to the provisions of Section 4.3, Holder
may transfer all or part of this Warrant or the Shares issuable upon exercise of
this Warrant (or the securities issuable, directly or indirectly, upon
conversion of the Shares, if any) at any time to Silicon Valley Bancshares or
The Silicon Valley Bank Foundation, or, to any other transferee by giving the
Company notice of the portion of the Warrant being transferred setting forth the
name, address and taxpayer identification number of the transferee and
surrendering this Warrant to the Company for reissuance to the transferee(s)
(and Holder if applicable). Unless Company is filing financial information with
the SEC pursuant to the Securities Exchange Act of 1933, the


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Company shall have the right to refuse to transfer any portion of this Warrant
to any person who directly competes with the Company.

     4.5 NOTICES. All notices and other communications from the Company to the
Holder, or vice versa, shall be deemed delivered and effective when given
personally or mailed by first-class registered or certified mail, at such
address as may have been furnished to the Company or the Holder, as the case may
be, in writing by the Company or such holder from time to time. All notices to
be provided under this Warrant shall be sent to the following address:

         Silicon Valley Bank
         Attn:  Treasury Department HG100
         3003 Tasman Drive
         Santa Clara, CA  95054

     4.6 WAIVER. This Warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of such change, waiver, discharge or termination is
sought.

     4.7 ATTORNEYS FEES. In the event of any dispute between the parties
concerning the terms and provisions of this Warrant, the party prevailing in
such dispute shall be entitled to collect from the other party all costs
incurred in such dispute, including reasonable attorneys' fees.

     4.8 GOVERNING LAW. This Warrant shall be governed by and construed in
accordance with the laws of the State of California, without giving effect to
its principles regarding conflicts of law.

                               COMPANY

                               CAMITRO CORPORATION

                               By: /s/ Harold E. Selick
                                   -------------------------------------
                               Name: Harold E. Selick
                               Title: President


                               By: /s/  Janet I. Swearson
                                   -------------------------------------
                               Name: Janet I Swearson
                               Title: Chief Financial Officer, Assistant
                                      Secretary


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                                   APPENDIX 1
                               NOTICE OF EXERCISE
                               ------------------


     1. The undersigned hereby elects to purchase___________shares of the
Common/Preferred Series________[Strike one] Stock of CAMITRO CORPORATION
pursuant to the terms of the attached Warrant, and tenders herewith payment of
the purchase price of such shares in full.

or

     1. The undersigned hereby elects to convert the attached Warrant into
Shares/Cash [Strike one] in the manner specified in the Warrant. This conversion
is exercised with respect to __________ of the Shares covered by the Warrant.

     2. Please issue a certificate or certificates representing said shares in
the name of the undersigned or in such other name as is specified below:


                       ---------------------------------
                              (Name)


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

                       ---------------------------------
                             (Address)


     3. The undersigned represents it is acquiring the shares solely for its own
account and not as a nominee for any other party and not with a view toward the
resale or distribution thereof except in compliance with applicable securities
laws.


                                      ---------------------------------
                                          (Signature)

--------------------------
      (Date)