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                                                                     Exhibit 4.1


THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
"ACT"), OR ANY APPLICABLE STATE SECURITIES OR "BLUE SKY" LAWS. THESE SECURITIES
MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN
EXEMPTION THEREFROM UNDER SAID ACT OR LAWS.


                                                  January 21, 2004          W-__

                         CALLISTO PHARMACEUTICALS, INC.

                              COMMON STOCK WARRANT

                  THIS CERTIFIES that, for value received, ________ and its
permitted transferees hereunder (the "Holder"), is entitled to subscribe for and
purchase from CALLISTO PHARMACEUTICALS, INC., a Delaware corporation (the
"Company"), up to ______ fully paid and nonassessable shares (the "Warrant
Shares") of common stock, $.0001 par value, of the Company (the "Common Stock")
at $1.90 per share (the "Warrant Price") subject to adjustment as provided in
Section 2 hereof, at any time or from time to time during the period (the
"Exercise Period") commencing on the date hereof and ending on January 21, 2009.

SECTION 1.     Exercise of Warrant.

         (a)      General. This Warrant may be exercised by the Holder as to the
whole or any lesser number of the Warrant Shares covered hereby, upon surrender
of this Warrant to the Company at its principal executive office together with
the Notice of Exercise attached hereto as Exhibit A, duly completed and executed
by the Holder, and payment to the Company of the aggregate Exercise Price for
the Warrant Shares to be purchased in the form of (i) a check made payable to
the Company, (ii) wire transfer according to the Company's instructions or (iii)
any combination of (i) and (ii). The exercise of this Warrant shall be deemed to
have been effected on the day on which the Holder surrenders this Warrant to the
Company and satisfies all of the requirements of this Section 1. Upon such
exercise, the Holder will be deemed a shareholder of record of those Warrant
Shares for which the warrant has been exercised with all rights of a shareholder
(including, without limitation, all voting rights with respect to such Warrant
Shares and all rights to receive any dividends with respect to such Warrant
Shares). If this Warrant is to be exercised in respect of less than all of the
Warrant Shares covered hereby, the Holder shall be entitled to receive a new
warrant covering the number of Warrant Shares in respect of which this Warrant
shall not have been exercised and for which it remains subject to exercise. Such
new warrant shall be in all other respects identical to this Warrant.

         (b)      Net Issue Exercise. In lieu of exercising this Warrant via
cash payment, the Holder may elect to receive shares equal to the value of this
Warrant (or the portion thereof being canceled) by surrender of this Warrant at
the principal office of the Company together with a Notice of Exercise duly
executed and completed indicating payment pursuant to this Section 1(b), in
which event the Company shall issue to the Holder a number of shares of Common
Stock of the Company computed using the following formula:

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


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

         Y        =        the number of Warrant Shares purchasable under this
                           Warrant or, if only a portion of the Warrant is being
                           exercised, the portion of the Warrant being cancelled
                           (at the date of such calculation).

         A        =        the Fair Market Value (as defined below) of one
                           Warrant Share (at the date of such calculation).

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

                  If the above calculation results in a negative number, then no
shares of Common Stock shall be issued or issuable upon conversion of this
Warrant.

         (c)      Fair Market Value. For purposes of this Section 1, the Fair
Market Value of one Warrant Share shall be determined by the Company's Board of
Directors in good faith; provided, however, that where there exists a public
market for the Common Stock at the time of such exercise, the fair market value
per Warrant Share shall be the average of the closing bid and asked prices of
the Common Stock quoted in the Over-The-Counter Market Summary or the last
reported sale price of the Common Stock or the closing price quoted on the
Nasdaq National Market or on any exchange on which the Common Stock is listed,
whichever is applicable, as published in The Wall Street Journal for the five
trading days prior to the date of determination of Fair Market Value.

SECTION 2.     Adjustment of Warrant Price. If, at any time during the Exercise
Period, the number of outstanding shares of Common Stock is (i) increased by a
stock dividend payable in shares of Common Stock or by a subdivision or split of
shares of such class of Common Stock, or (ii) decreased by a combination or
reverse split of shares of Common Stock, then, following the record date fixed
for the determination of holders of Common Stock entitled to receive the
benefits of such stock dividend, subdivision, split-up, reverse split-up or
combination, the Warrant Price shall be proportionately reduced, in the case of
an increase in shares of Common Stock outstanding, or proportionately increased,
in the case of a decrease in shares of Common Stock outstanding, in both cases
by the ratio which the total number of shares of Common Stock to be outstanding
immediately after such event bears to the total number of shares of Common Stock
outstanding immediately prior to such event.

SECTION 3.     Adjustment of Warrant Shares. Upon each adjustment of the Warrant
Price as provided in Section 2, the Holder shall thereafter be entitled to
subscribe for and purchase, at the Warrant Price resulting from such adjustment,
the number of Warrant Shares equal to the product of (i) the number of Warrant
Shares existing prior to such adjustment and (ii) the quotient obtained by
dividing (A) the Warrant Price existing prior to such adjustment by (B) the new
Warrant Price resulting from such adjustment. No fractional shares of capital
stock of the Company shall be issued as a result of any such adjustment, and any
fractional shares resulting from the computations pursuant to this paragraph
shall be eliminated without consideration.


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SECTION 4.     No Shareholder Rights. This Warrant shall not entitle the holder
hereof to any voting rights or other rights as a shareholder of the Company.

SECTION 5.     Covenant of the Company. The Company covenants and agrees that
the Company shall at all times have authorized and reserved or shall authorize
and reserve, free from preemptive rights, a sufficient number of shares of its
Common Stock to provide for the exercise of the rights represented by this
Warrant.

SECTION 6.     Investment Representations and Warranties. The Holder hereby
represents and warrants to the Company as follows:

         (a)      The Holder is acquiring the Warrant, and it will acquire the
Common Stock issuable upon exercise thereof, for its own account, for investment
and not with a view to the distribution thereof, nor with any present intention
of distributing the same. The Holder understands that the Warrant and Common
Stock issuable upon exercise thereof, will not be registered under the Act or
registered or qualified under any state securities or "blue-sky" laws, by reason
of their issuance in a transaction exempt from the registration and/or
qualification requirements thereof, and that they must be held indefinitely
unless a subsequent disposition thereof is registered under the Act or
registered or qualified under any applicable state securities or "blue-sky" laws
or is exempt from registration and/or qualification.

         (b)      The Holder understands that the exemption from registration
afforded by Rule 144 (the provisions of which are known to the Holder)
promulgated under the Act depends on the satisfaction of various conditions and
that, if applicable, Rule 144 may only afford the basis for sales under certain
circumstances only in limited amounts.

         (c)      The Holder has no need for liquidity in its investment in the
Company, and is able to bear the economic risk of such investment for an
indefinite period and to afford a complete loss thereof.

         (d)      The Holder is an "accredited purchaser" as such term is
defined in Rule 501 (the provisions of which are known to the Holder)
promulgated under the Act.

SECTION 7.     Restrictions on Transfer. The Holder of this Warrant by
acceptance hereof agrees that the transfer of this Warrant and the shares of
Common Stock issuable upon exercise of this Warrant are subject to the following
provisions:

         (a)      General. Subject to the requirements of the Act or any
applicable state securities laws, the Holder may sell, assign, transfer or
otherwise dispose of all or any portion of the Warrants or the Warrant Shares
acquired upon any exercise hereof at any time and from time to time. Upon the
sale, assignment, transfer or other disposition of all or any portion of the
Warrants, Holder shall deliver to the Company a written notice of such in the
form attached hereto as Exhibit B, duly executed by Holder, which includes the
identity and address of any purchaser, assignor or transferee.


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         (b)      Restrictive Legend. Each certificate for Warrant Shares held
by the Holder and each certificate for any such securities issued to subsequent
transferees of any such certificate shall be stamped or otherwise imprinted with
legends in substantially the following form:

         "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR
         INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
         1933, AS AMENDED (THE "ACT") OR ANY RELEVANT STATE SECURITIES LAWS.
         THESE SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH
         REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND APPLICABLE
         STATE SECURITIES LAWS".

         (c)      Indemnification. Holder acknowledges that he, she or it
understands the meaning and legal consequences of the representations,
warranties and acknowledgments he, she or it has made in Section 7 and elsewhere
in this Warrant and he, she or it understands that the Company is relying upon
the truth and accuracy thereof. Accordingly, the Holder hereby agrees to
indemnify and hold harmless the Company, its officers, agents and
representatives, from and against any and all loss, damage or liability due to
or arising out of a breach of any representation or warranty of Holder contained
in this Warrant.

SECTION 8.     Amendment. The terms and provisions of this Warrant may not be
modified or amended, except with the written consent of the Company and the
Holder.

SECTION 9.     Reorganizations, Etc. In case, at any time during the Exercise
Period, of any capital reorganization, of any reclassification of the stock of
the Company (other than a change in par value or from par value to no par value
or from no par value to par value or as a result of a stock dividend or
subdivision, split-up or combination of shares), or the consolidation or merger
of the Company with or into another corporation (other than a consolidation or
merger in which the Company is the continuing operation and which does not
result in any change or reclassification in the Warrant Shares) or of the sale
of all or substantially all the properties and assets of the Company as an
entirety to any other corporation, the Company, at its sole discretion, shall
have the right and option to (A) provide 10 days prior written notice of such
event to the Holder and this Warrant shall terminate and be of no further force
and effect on and after the effective date of such capital reorganization or
reclassification or the consummation of such consolidation, sale or merger; or
(B) provide that this Warrant shall, after such reorganization,
reclassification, consolidation, merger or sale, be exercisable for the kind and
number of shares of stock or other securities or property of the Company or of
the corporation resulting from such consolidation or surviving such merger or to
which such properties and assets shall have been sold to which such holder would
have been entitled if he, she or it had held the Warrant Shares issuable upon
the exercise hereof immediately prior to such reorganization, reclassification,
consolidation, merger or sale.

SECTION 10.    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 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. Any such new Warrant shall constitute an original contractual
obligation of the Company, whether or not the allegedly lost, stolen, mutilated
or destroyed Warrant shall be at any time enforceable by anyone.


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SECTION 11.    Notices. All notices, advices and communications to be given or
otherwise made to any party to this Agreement shall be deemed to be sufficient
if contained in a written instrument delivered in person or by telecopier or
duly sent by first class registered or certified mail, return receipt requested,
postage prepaid, or by overnight courier, or by electronic mail, with a copy
thereof to be sent by mail (as aforesaid) within 24 hours of such electronic
mail, addressed to such party at the address set forth below or at such other
address as may hereafter be designated in writing by the addressee to the
addresser listing all parties:

         (a)      If to the Company, to:

                           Callisto Pharmaceuticals, Inc.
                           420 Lexington Avenue, Suite 2500
                           New York, New York 10170
                           Attention: Gary S Jacob
                                      Chief Executive Officer


                                      and



         (b)      If to the Holder, to:




or to such other address as the party to whom notice is to be given may have
furnished to the other parties hereto in writing in accordance herewith. Any
such notice or communication shall be deemed to have been delivered and received
(i) in the case of personal delivery or delivery by telecopier, on the date of
such deliver, (ii) in the case of nationally-recognized overnight courier, on
the next business day after the date when sent and (ii) in the case of mailing,
on the third business day following that on which the piece of mail containing
such communication is posted. As used in this Section 11, "business day" shall
mean any day other than a day on which banking institutions in the State of New
York are legally closed for business.

SECTION 12.    Binding Effect on Successors. Subject to Section 9 hereof, this
Warrant shall be binding upon any corporation succeeding the Company by merger,
consolidation or acquisition of all or substantially all of the Company's
assets.

SECTION 13.    Descriptive Headings and Governing Law. The description headings
of the several sections and paragraphs of this Warrant are inserted for
convenience only and do not constitute a part of this Warrant. This Warrant
shall be construed and enforced in accordance with, and the rights of the
parties shall be governed by, the laws of the State of New York (without giving
effect to conflicts of law principles thereunder).


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SECTION 14.    Fractional Shares. No fractional shares shall be issued upon
exercise of this Warrant. The Company shall, in lieu of issuing any fractional
share, pay the holder entitled to such fraction a sum in cash equal to such
fraction multiplied by the then effective Warrant Price.

                                     * * *


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         IN WITNESS WHEREOF, the undersigned has caused this Common Stock
Warrant to be executed by its duly authorized officer as of the date first above
written.

                                        CALLISTO PHARMACEUTICALS, INC.



                                        By:
                                             -----------------------------------
                                             Name:  Gary S. Jacob
                                             Title: Chief Executive Officer


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                                                                       Exhibit A


                              Form of Subscription
--------------------------------------------------------------------------------


                               NOTICE OF EXERCISE
                              COMMON STOCK WARRANT

To:      Callisto Pharmaceuticals, Inc.

                  The undersigned hereby:

         1.       (a)      elects to purchase _______ shares of Common Stock
("Common Stock") of Callisto Pharmaceuticals, Inc., a Delaware corporation, (the
"Company") pursuant to the terms of the attached Warrant, and tenders herewith
payment of the aggregate exercise price therefor and any transfer taxes payable
pursuant to the terms of the Warrant; or

         2.       (b)      elects to exercise this Warrant for the purchase of
________ shares of the Common Stock pursuant to the provisions of Section 1(b)
of the attached Warrant.

         Please issue a certificate or certificates representing said shares of
Common Stock in the name of the undersigned or in such other name or names as
are specified below:

         Name:
                  -------------------------------------------------
         Address:
                  -------------------------------------------------

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

         IN WITNESS WHEREOF, the Warrant Holder has executed this Notice of
Exercise effective this ___ day of _____________, ____.



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


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                                                                       Exhibit B

                               Form of Assignment
                  [To be signed only upon transfer of Warrant]

         For value received, the undersigned hereby sells, assigns and transfers
unto the right represented by the within Warrant to purchase _______ shares of
Common Stock of CALLISTO PHARMACEUTICALS, INC., to which the within Warrant
relates, and appoints Attorney to transfer such right on the books of CALLISTO
PHARMACEUTICALS, INC., with full power of substitution in the premises.


Dated:                   _____________________________
                                  (Signature)



Signed in the presence of:


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


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