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                                                                    Exhibit 10.1


                         REGISTRATION RIGHTS AGREEMENT

         THIS REGISTRATION RIGHTS AGREEMENT, dated as of January 21, 2004 (this
"Agreement"), is made by and between CALLISTO PHARMACEUTICALS, INC., a Delaware
corporation, having its principal place of business located at 420 Lexington
Avenue, Suite 601, New York, NY 10170 (the "Company"), and each entity named on
a signature page hereto (each, an "Initial Investor") (each agreement with an
Initial Investor being deemed a separate and independent agreement between the
Company and such Initial Investor, except that each Initial Investor
acknowledges and consents to the rights granted to each other Initial Investor
under such agreement).

                              W I T N E S S E T H:

         WHEREAS, upon the terms and subject to the conditions of the
Subscription Agreement between the Initial Investor and the Company, the Company
has agreed to issue and sell to the Initial Investor shares of the Common Stock
of the Company (the "Registrable Securities"); and

         WHEREAS, to induce the Initial Investor to execute and deliver the
Subscription Agreement, the Company has agreed to provide certain registration
rights under the Securities Act of 1933, as amended, and the rules and
regulations thereunder, or any similar successor statute (collectively, the
"Securities Act"), with respect to the Registrable Securities;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and the
Initial Investor hereby agree as follows:

         1.       Definitions. As used in this Agreement, the following terms
shall have the following meanings:

         (a)      "Investor" means the Initial Investor and any permitted
transferee or assignee who agrees to become bound by the provisions of this
Agreement in accordance with Section 9 hereof and who holds Registrable
Securities.

         (b)      "Potential Material Event" means any of the following: (i) the
possession by the Company of material information not ripe for disclosure in a
registration statement, which shall be evidenced by a determination in good
faith by the Board of Directors of the Company that disclosure of such
information in the registration statement would be detrimental to the business
and affairs of the Company or (ii) any material engagement or activity by the
Company which would, in the good faith determination of the Board of Directors
of the Company, be adversely affected by disclosure in a registration statement
at such time; in each case where such determination shall be accompanied by a
good faith determination by the Board of Directors of the Company that the
registration statement would be materially misleading absent the inclusion of
such information.

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         (c)      "Register," "Registered," and "Registration" refer to a
registration effected by preparing and filing a Registration Statement or
Statements in compliance with the Securities Act and pursuant to Rule 415 under
the Securities Act or any successor rule providing for offering securities on a
continuous basis ("Rule 415"), and the declaration or ordering of effectiveness
of such Registration Statement by the United States Securities and Exchange
Commission (the "SEC").

         (d)      "Registrable Securities" has the meaning ascribed to it in the
Agreement.

         (e)      "Registration Statement" means a registration statement of the
Company under the Securities Act covering Registrable Securities on Form S-3, if
the Company is then eligible to file using such form, and if not eligible, on
Form SB-2 or other appropriate form.

         (f)      "Effective Date" means the date the SEC declares a
Registration Statement covering Registrable Securities and otherwise meeting the
conditions contemplated hereby to be effective.

         2.       Registration.

         (a)      Mandatory Registration. The Company shall prepare and file
with the SEC, as soon as possible after the final Closing Date but no later than
ninety (90) days after the Closing Date (the "Required Filing Date"), either a
Registration Statement or an amendment to an existing Registration Statement, in
either event registering for resale by the Investor a sufficient number of
shares of Common Stock for the Initial Investors to sell the Registrable
Securities, but in no event less than the number of shares equal to the
Registrable Securities at the time of filing of such Registration Statement (or
such lesser number as may be required by the SEC). The Registration Statement
shall include only the Registrable Securities, and shall also state that, in
accordance with Rule 416 and 457 under the Securities Act, it also covers such
indeterminate number of additional shares of Common Stock as may become issuable
to prevent dilution resulting from stock splits, or stock dividends. The Company
will use its reasonable best efforts to cause such Registration Statement to be
declared effective on a date (the "Initial Effective Date") which is no later
than the earlier of five (5) days after oral or written notice by the SEC that
it may be declared effective or two hundred forty (240) days after the Closing
Date.

         (b)      Payments by the Company.

                  (i)      If the Registration Statement covering the
Registrable Securities is not filed in accordance with the terms of this
Agreement with the SEC by the Required Filing Date, the Company will make
payment to the Initial Investor in such amounts and at such times as shall be
determined pursuant to this Section 2(b).

                  (ii)     The amount (the "Periodic Amount") to be paid by the
Company to the Initial Investor shall be determined as of each Computation Date
(as defined below) and such amount shall be equal to one eighth percent (1/8%)
of the Purchase Price for the period from the date following the Required Filing
Date to the first relevant Computation Date, and thereafter to each subsequent
Computation Date, in each case prorated on a daily basis. By way of illustration
and not in limitation of the foregoing, if the Registration Statement is not
filed until one hundred fifty (150) days after the final Closing Date, the
Periodic Amount will aggregate one-quarter percent (1/4%) of the Purchase Price
(1/8% for days 91-120, plus 1/8% for days 121-150).


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                  (iii)    Upon demand therefor by the Investor, each Periodic
Amount will be payable by the Company, at the Company's option, in cash or in
common stock of the Company (which if issued shall be deemed to be Registrable
Securities pursuant to this Agreement) to the Investor (1) on the earlier of the
thirty-first day after the Required Filing Date, and (2) on the earlier of (A)
each thirtieth day thereafter or, (B) the third business day after the date the
Registration Statement is filed. Any common stock of the Company issued pursuant
to this Section 2(b)(iii) shall be valued at the closing bid price of the
Company's common stock as reported by the OTC Bulletin Board (or Nasdaq if the
common stock is then quoted on Nasdaq) on the day preceding the Investor's
demand or if the common stock is not trading on the OTC Bulletin Board (or
Nasdaq) the common stock of the Company shall be valued at a price determined in
good faith by the Board of Directors of the Company.

                  (iv)     The parties acknowledge that the damages which may be
incurred by the Investor if the Registration Statement is not filed by the
Required Filing Date, including if the right to sell Registrable Securities
under a previously effective Registration Statement is suspended may be
difficult to ascertain. The parties agree that the Periodic Amounts represent a
reasonable estimate on the part of the parties, as of the date of this
Agreement, of the amount of such damages.

                  (v)      Notwithstanding the foregoing, the amounts payable by
the Company pursuant to this provision shall not be payable (A) to the extent
any delay in the filing of the Registration Statement occurs because of an act
of, or a failure to act or to act timely by the Initial Investor or its counsel,
or (B) in the event all of the Registrable Securities may be sold pursuant to
Rule 144 or another available exemption under the Act without volume or other
restrictions or limits.

                  (vi)     "Computation Date" means (A) the date which is the
earlier of (1) thirty (30) days after the Required Filing Date or (2) the date
after the Required Filing Date on which the Registration Statement is filed
(with respect to payments due as contemplated by Section 2(b)(i) hereof) and (B)
each date which is the earlier of (1) thirty (30) days after the previous
Computation Date or (2) the date after the previous Computation Date on which
the Registration Statement is filed (with respect to payments due as
contemplated by Section 2(b)(i) hereof).

         3.       Obligations of the Company. In connection with the
registration of the Registrable Securities, the Company shall do each of the
following:

         (a)      Prepare promptly, and file with the SEC by the Required Filing
Date a Registration Statement with respect to not less than the number of
Registrable Securities provided in Section 2(a) above, and thereafter use its
reasonable best efforts to cause such Registration Statement relating to
Registrable Securities to become effective by the Initial Effective Date and
keep the Registration Statement effective at all times during the period (the
"Registration Period") continuing until the earliest of (i) the date that is
three (3) years after the last day of the calendar month following the month in
which the relevant Effective Date occurs, (ii) the date when the Investors may
sell all Registrable Securities under Rule 144 without volume or other
restrictions or limits or (iii) the date the Investors no longer own any of the
Registrable Securities, which Registration Statement (including any amendments
or supplements thereto and prospectuses contained therein) shall not contain any
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein, in light of the
circumstances in which they were made, not misleading;


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         (b)      Prepare and file with the SEC such amendments (including
post-effective amendments) and supplements to the Registration Statement and the
prospectus used in connection with the Registration Statement as may be
necessary to keep the Registration Statement effective at all times during the
Registration Period, and, during the Registration Period, comply with the
provisions of the Securities Act with respect to the disposition of all
Registrable Securities of the Company covered by the Registration Statement
until such time as all of such Registrable Securities have been disposed of in
accordance with the intended methods of disposition by the seller or sellers
thereof as set forth in the Registration Statement;

         (c)      Permit a single firm of counsel designated by the Initial
Investors to review the Registration Statement and all amendments and
supplements thereto a reasonable period of time (but not less than three (3)
business days) prior to their filing with the SEC, and not file any document in
a form to which such counsel reasonably objects;

         (d)      Notify each Investor and such Investor's legal counsel
identified to the Company and which has requested by written notice to the
Company that it receive such notification ("Investor's Counsel") and any
managing underwriters immediately (and, in the case of(i)(A) below, not less
than three (3) business days prior to such filing) and (if requested by any such
person) confirm such notice in writing no later than one (1) business day
following the day (i)(A) when a Prospectus or any Prospectus supplement or
post-effective amendment to the Registration Statement is proposed to be filed;
(B) whenever the SEC notifies the Company whether there will be a "review" of
such Registration Statement; (C) whenever the Company receives (or a
representative of the Company receives on its behalf) any oral or written
comments from the SEC in respect of a Registration Statement (copies or, in the
case of oral comments, summaries of such comments shall be promptly furnished by
the Company to the Investors); and (D) with respect to the Registration
Statement or any post-effective amendment, when the same has become effective;
(ii) of any request by the SEC or any other Federal or state governmental
authority for amendments or supplements to the Registration Statement or
Prospectus or for additional information; (iii) of the issuance by the SEC of
any stop order suspending the effectiveness of the Registration Statement
covering any or all of the Registrable Securities or the initiation of any
proceedings for that purpose; (iv) of the receipt by the Company of any
notification with respect to the suspension of the qualification or exemption
from qualification of any of the Registrable Securities for sale in any
jurisdiction, or the initiation or threatening of any proceeding for such
purpose; and (v) of the occurrence of any event that to the best knowledge of
the Company makes any statement made in the Registration Statement or Prospectus
or any document incorporated or deemed to be incorporated therein by reference
untrue in any material respect or that requires any revisions to the
Registration Statement, Prospectus or other documents so that, in the case of
the Registration Statement or the Prospectus, as the case may be, it will not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary to make the statements therein,
in light of the circumstances under which they were made, not misleading. In
addition, the Company shall furnish the Investor's Counsel with copies of all
intended written responses to the comments contemplated in clause (C) of this
Section 3(d) not later than one (1) business day in advance of the filing of
such responses with the SEC so that the Investors shall have the opportunity to
comment thereon;


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         (e)      Furnish to each Investor and such Investor's Counsel (i)
promptly after the same is prepared and publicly distributed, filed with the
SEC, or received by the Company, one (1) copy of the Registration Statement,
each preliminary prospectus and prospectus, and each amendment or supplement
thereto, and (ii) such number of copies of a prospectus, and all amendments and
supplements thereto and such other documents, as such Investor may reasonably
request in order to facilitate the disposition of the Registrable Securities
owned by such Investor;

         (f)      As promptly as practicable after becoming aware thereof,
notify each Investor of the happening of any event of which the Company has
knowledge, as a result of which the prospectus included in the Registration
Statement, as then in effect, includes an untrue statement of a material fact or
omits to state a material fact required to be stated therein or necessary to
make the statements therein, in light of the circumstances under which they were
made, not misleading, and use its best efforts promptly to prepare a supplement
or amendment to the Registration Statement or other appropriate filing with the
SEC to correct such untrue statement or omission, and deliver a number of copies
of such supplement or amendment to each Investor as such Investor may reasonably
request;

         (g)      As promptly as practicable after becoming aware thereof,
notify each Investor who holds Registrable Securities being sold (or, in the
event of an underwritten offering, the managing underwriters) of the issuance by
the SEC of a Notice of Effectiveness or any notice of effectiveness or any stop
order or other suspension of the effectiveness of the Registration Statement at
the earliest possible time;

         (h)      Notwithstanding the foregoing, if at any time or from time to
time after the date of effectiveness of the Registration Statement, the Company
notifies the Investors in writing of the existence of a Potential Material
Event, the Investors shall not offer or sell any Registrable Securities, or
engage in any other transaction involving or relating to the Registrable
Securities, from the time of the giving of notice with respect to a Potential
Material Event until such Investor receives written notice from the Company that
such Potential Material Event either has been disclosed to the public or no
longer constitutes a Potential Material Event.

         (i)      Use its reasonable efforts to secure and maintain the
designation of all the Registrable Securities covered by the Registration
Statement on the OTC Bulletin Board.

         (j)      Provide a transfer agent and registrar, which may be a single
entity, for the Registrable Securities not later than the Initial Effective
Date.


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         (k)      Cooperate with the Investors who hold Registrable Securities
being offered to facilitate the timely preparation and delivery of certificates
for the Registrable Securities to be offered pursuant to the Registration
Statement and enable such certificates for the Registrable Securities to be in
such denominations or amounts as the case may be, as the Investors may
reasonably request, and, within five (5) business days after a Registration
Statement which includes Registrable Securities is ordered effective by the SEC,
the Company shall deliver, and shall cause legal counsel selected by the Company
to deliver, to the transfer agent for the Registrable Securities (with copies to
the Investors whose Registrable Securities are included in such Registration
Statement) an appropriate instruction and, if necessary, an opinion of such
counsel; and

         (l)      Take all other reasonable actions necessary to expedite and
facilitate disposition by the Investor of the Registrable Securities pursuant to
the Registration Statement.

         4.       Obligations of the Investors. In connection with the
registration of the Registrable Securities, the Investors shall have the
following obligations:

         (a)      It shall be a condition precedent to the obligations of the
Company to complete the registration pursuant to this Agreement with respect to
the Registrable Securities of a particular Investor that such Investor shall
furnish to the Company such information regarding itself, the Registrable
Securities held by it, and the intended method of disposition of the Registrable
Securities held by it, as shall be reasonably required to effect the
registration of such Registrable Securities and shall execute such documents in
connection with such registration as the Company may reasonably request. At
least ten (10) days prior to the first anticipated filing date of the
Registration Statement, the Company shall notify each Investor of the
information the Company requires from each such Investor (the "Requested
Information") if such Investor has any Registrable Securities included in the
Registration Statement. If at least two (2) business days prior to the filing
date the Company has not received the Requested Information from an Investor (a
"Non-Responsive Investor"), then the Company may file the Registration Statement
without including Registrable Securities of such Non-Responsive Investor;

         (b)      Each Investor, by such Investor's acceptance of the
Registrable Securities, agrees to cooperate with the Company as reasonably
requested by the Company in connection with the preparation and filing of the
Registration Statement hereunder, unless such Investor has notified the Company
in writing of such Investor's election to exclude all of such Investor's
Registrable Securities from the Registration Statement; and

         (c)      Each Investor agrees that, upon receipt of any notice from the
Company of the happening of any event of the kind described in Section 3(f) or
3(g), above, such Investor will immediately discontinue disposition of
Registrable Securities pursuant to the Registration Statement covering such
Registrable Securities until such Investor's receipt of the copies of the
supplemented or amended prospectus contemplated by Section 3(f) or 3(g) and, if
so directed by the Company, such Investor shall deliver to the Company (at the
expense of the Company) or destroy (and deliver to the Company a certificate of
destruction) all copies in such Investor's possession, of the prospectus
covering such Registrable Securities current at the time of receipt of such
notice.

         5.       Expenses of Registration. All reasonable expenses (other than
underwriting discounts and commissions of the Investor) incurred in connection
with registrations, filings or qualifications pursuant to Section 3, but
including, without limitation, all registration, listing, and qualifications
fees, printers and accounting fees, the fees and disbursements of counsel for
the Company shall be borne by the Company.


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         6.       Indemnification. In the event any Registrable Securities are
included in a Registration Statement under this Agreement:

         (a)      To the extent permitted by law, the Company will indemnify and
hold harmless each Investor who holds such Registrable Securities, the
directors, if any, of such Investor, the officers, if any, of such Investor,
each person, if any, who controls any Investor within the meaning of the
Securities Act or the Exchange Act (each, an "Indemnified Person" or
"Indemnified Party"), against any losses, claims, damages, liabilities or
expenses (joint or several) incurred (collectively, "Claims") to which any of
them may become subject under the Securities Act, the Exchange Act or otherwise,
insofar as such Claims (or actions or proceedings, whether commenced or
threatened, in respect thereof) arise out of or are based upon any of the
following statements, omissions or violations in the Registration Statement, or
any post-effective amendment thereof, or any prospectus included therein: (i)
any untrue statement or alleged untrue statement of a material fact contained in
the Registration Statement or any post-effective amendment thereof or the
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, (ii)
any untrue statement or alleged untrue statement of a material fact contained in
the final prospectus (as amended or supplemented, if the Company files any
amendment thereof or supplement thereto with the SEC) or the omission or alleged
omission to state therein any material fact necessary to make the statements
made therein, in light of the circumstances under which the statements therein
were made, not misleading or (iii) any violation or alleged violation by the
Company of the Securities Act, the Exchange Act, any state securities law or any
rule or regulation under the Securities Act, the Exchange Act or any state
securities law (the matters in the foregoing clauses (i) through (iii) being,
collectively, "Violations"). Subject to clause (b) of this Section 6, the
Company shall reimburse the Investors, promptly as such expenses are incurred
and are due and payable, for any legal fees or other reasonable expenses
incurred by them in connection with investigating or defending any such Claim.
Notwithstanding anything to the contrary contained herein, the indemnification
agreement contained in this Section 6(a) shall not (I) apply to a Claim arising
out of or based upon a Violation which occurs in reliance upon and in conformity
with information furnished in writing to the Company by or on behalf of any
Indemnified Person expressly for use in connection with the preparation of the
Registration Statement or any such amendment thereof or supplement thereto,
after such prospectus was made available by the Company pursuant to Section 3(c)
hereof; (II) be available to the extent such Claim is based on a failure of the
Investor to deliver or cause to be delivered the prospectus made available by
the Company or the amendment or supplement thereto made available by the
Company; (III) be available to the extent such Claim is based on the delivery of
a prospectus by the Investor after receiving notice from the Company under
Section 3(f), (g) or (h) hereof (other than a notice regarding the effectiveness
of the Registration Statement or any amendment or supplement thereto), or (IV)
apply to amounts paid in settlement of any Claim if such settlement is effected
without the prior written consent of the Company, which consent shall not be
unreasonably withheld or delayed. Each Investor will indemnify the Company and
its officers, directors and agents (each, an "Indemnified Person" or
"Indemnified Party") against any claims arising out of or based upon a Violation
which occurs in reliance upon and in conformity with information furnished in
writing to the Company, by or on behalf of such Investor, expressly for use in
connection with the preparation of the Registration Statement or the amendment
or supplement thereto, subject to such limitations and conditions as are
applicable to the Indemnification provided by the Company to this Section 6.
Such indemnity shall remain in full force and effect regardless of any
investigation made by or on behalf of the Indemnified Person and shall survive
the transfer of the Registrable Securities by the Investors pursuant to Section
9.


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         (b)      Promptly after receipt by an Indemnified Person or Indemnified
Party under this Section 6 of notice of the commencement of any action
(including any governmental action), such Indemnified Person or Indemnified
Party shall, if a Claim in respect thereof is to be made against any
indemnifying party under this Section 6, deliver to the indemnifying party a
written notice of the commencement thereof and the indemnifying party shall have
the right to participate in, and, to the extent the indemnifying party so
desires, jointly with any other indemnifying party similarly noticed, to assume
control of the defense thereof with counsel mutually satisfactory to the
indemnifying party and the Indemnified Person or the Indemnified Party, as the
case may be. In case any such action is brought against any Indemnified Person
or Indemnified Party, and it notifies the indemnifying party of the commencement
thereof, the indemnifying party will be entitled to participate in, and, to the
extent that it may wish, jointly with any other indemnifying party similarly
notified, assume the defense thereof, subject to the provisions herein stated
and after notice from the indemnifying party to such Indemnified Person or
Indemnified Party of its election so to assume the defense thereof, the
indemnifying party will not be liable to such Indemnified Person or Indemnified
Party under this Section 6 for any legal or other reasonable out-of-pocket
expenses subsequently incurred by such Indemnified Person or Indemnified Party
in connection with the defense thereof other than reasonable costs of
investigation, unless the indemnifying party shall not pursue the action to its
final conclusion. The Indemnified Person or Indemnified Party shall have the
right to employ separate counsel in any such action and to participate in the
defense thereof, but the fees and reasonable out-of-pocket expenses of such
counsel shall not be at the expense of the indemnifying party if the
indemnifying party has assumed the defense of the action with counsel reasonably
satisfactory to the Indemnified Person or Indemnified Party provided such
counsel is of the opinion that all defenses available to the Indemnified Party
can be maintained without prejudicing the rights of the indemnifying party. The
failure to deliver written notice to the indemnifying party within a reasonable
time of the commencement of any such action shall not relieve such indemnifying
party of any liability to the Indemnified Person or Indemnified Party under this
Section 6, except to the extent that the indemnifying party is prejudiced in its
ability to defend such action. The indemnification required by this Section 6
shall be made by periodic payments of the amount thereof during the course of
the investigation or defense, as such expense, loss, damage or liability is
incurred and is due and payable.

         7.       Contribution. To the extent any indemnification by an
indemnifying party is prohibited or limited by law, the indemnifying party
agrees to make the maximum contribution with respect to any amounts for which it
would otherwise be liable under Section 6 to the fullest extent permitted by
law; provided, however, that (a) no contribution shall be made under
circumstances where the maker would not have been liable for indemnification
under the fault standards set forth in Section 6; (b) no seller of Registrable
Securities guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any seller
of Registrable Securities who was not guilty of such fraudulent
misrepresentation; and (c) except where the seller has committed fraud (other
than a fraud by reason of the information included or omitted from the
Registration Statement as to which the Company has not given notice as
contemplated under Section 3 hereof) or intentional misconduct, contribution by
any seller of Registrable Securities shall be limited in amount to the net
amount of proceeds received by such seller from the sale of such Registrable
Securities.


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         8.       Reports under Securities Act and Exchange Act. With a view to
making available to Investor the benefits of Rule 144 promulgated under the
Securities Act or any other similar rule or regulation of the SEC that may at
any time permit Investor to sell securities of the Company to the public without
Registration ("Rule 144"), the Company agrees to:

         (a)      make and keep public information available, as those terms are
understood and defined in Rule 144;

         (b)      file with the SEC in a timely manner all reports and other
documents required of the Company under the Securities Act and the Exchange Act;
and

         (c)      furnish to Investor so long as Investor owns Registrable
Securities, promptly upon request, (i) a written statement by the Company that
it has complied with the reporting requirements of the Securities Act and the
Exchange Act, and (ii) such other information as may be reasonably requested to
permit Investor to sell such securities pursuant to Rule 144 without
Registration.

         (d)      The Company will, at the request of any Holder of Registrable
Securities, upon receipt from such Holder of a certificate certifying (i) that
such Holder has held such Registrable Securities for a period of not less than
one (1) year, (ii) that such Holder has not been an affiliate (as defined in
Rule 144) of the company for more than the ninety (90) preceding days, and (iii)
as to such other matters as may be appropriate in accordance with such Rule,
remove from the stock certificate representing such Registrable Securities that
portion of any restrictive legend which relates to the registration provisions
of the Securities Act, provided, however, counsel to Investor may provide such
instructions and opinion to the transfer agent regarding the removal of the
restrictive legend.

         9.       Assignment of the Registration Rights. The rights to have the
Company register Registrable Securities pursuant to this Agreement shall be
automatically assigned by the Investors to any transferee of the Registrable
Securities only if: (a) the Investor agrees in writing with the transferee or
assignee to assign such rights, and a copy of such agreement is furnished to the
Company within a reasonable time after such assignment, (b) the Company is,
within a reasonable time after such transfer or assignment, furnished with
written notice of (i) the name and address of such transferee or assignee and
(ii) the securities with respect to which such registration rights are being
transferred or assigned, (c) immediately following such transfer or assignment
the further disposition of such securities by the transferee or assignee is
restricted under the Securities Act and applicable state securities laws, (d) at
or before the time the Company received the written notice contemplated by
clause (b) of this sentence the transferee or assignee agrees in writing with
the Company to be bound by all of the provisions contained herein, and (e) such
transfer of Registrable Securities is completed and disclosed to the Company
prior to the Initial Effective Date. In the event of any delay in filing or
effectiveness of the Registration Statement as a result of such assignment, the
Company shall not be liable for any damages arising from such delay, or the
payments set forth in Section 2(b) hereof arising from such delay.


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         10.      Amendment of Registration Rights. Any provision of this
Agreement may be amended and the observance thereof may be waived (either
generally or in a particular instance and either retroactively or
prospectively), only with the written consent of the Company and Investors who
hold a sixty-seven percent (67%) interest of the Registrable Securities. Any
amendment or waiver effected in accordance with this Section 10 shall be binding
upon each Investor and the Company.

         11.      Miscellaneous.

         (a)      A person or entity is deemed to be a holder of Registrable
Securities whenever such person or entity owns of record such Registrable
Securities. If the Company receives conflicting instructions, notices or
elections from two or more persons or entities with respect to the same
Registrable Securities, the Company shall act upon the basis of instructions,
notice or election received from the registered owner of such Registrable
Securities.

         (b)      Notices required or permitted to be given hereunder shall be
given in the manner contemplated by the Securities Purchase Agreement, (i) if to
the Company or to the Initial Investor, to their respective address contemplated
by the Securities Purchase Agreement, and (ii) if to any other Investor, at such
address as such Investor shall have provided in writing to the Company, or at
such other address as each such party furnishes by notice given in accordance
with this Section 11(b).

         (c)      Failure of any party to exercise any right or remedy under
this Agreement or otherwise, or delay by a party in exercising such right or
remedy, shall not operate as a waiver thereof.

         (d)      This Agreement shall be governed by and interpreted in
accordance with the laws of the State of New York for contracts to be wholly
performed in such state and without giving effect to the principles thereof
regarding the conflict of laws. Each of the parties consents to the jurisdiction
of the federal courts whose districts encompass any part of the City of New York
or the state courts of the State of New York sitting in the City of New York in
connection with any dispute arising under this Agreement and hereby waives, to
the maximum extent permitted by law, any objection, including any objection
based on forum non coveniens, to the bringing of any such proceeding in such
jurisdictions. To the extent determined by such court, either party hereto shall
reimburse the other party for any reasonable legal fees and disbursements
incurred by such party in enforcement of or protection of any of its rights
under this Agreement.

         (e)      If any provision of this Agreement shall be invalid or
unenforceable in any jurisdiction, such invalidity or unenforceability shall not
affect the validity or enforceability of the remainder of this Agreement or the
validity or enforceability of this Agreement in any other jurisdiction.


                                       10
<PAGE>

         (f)      Subject to the requirements of Section 9 hereof, this
Agreement shall inure to the benefit of and be binding upon the successors and
assigns of each of the parties hereto.

         (g)      All pronouns and any variations thereof refer to the
masculine, feminine or neuter, singular or plural, as the context may require.

         (h)      The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning thereof.

         (i)      This Agreement may be executed in one or more counterparts,
each of which shall be deemed an original but all of which shall constitute one
and the same agreement. This Agreement, once executed by a party, may be
delivered to the other party hereto by telephone line facsimile transmission of
a copy of this Agreement bearing the signature of the party so delivering this
Agreement.

         (j)      The Company acknowledges that any failure by the Company to
perform its obligations under Section 3(a) hereof, or any delay in such
performance could result in loss to the Investors, and the Company agrees that,
in addition to any other liability the Company may have by reason of such
failure or delay, the Company shall be liable for all direct damages caused by
any such failure or delay, unless the same is the result of force majeure.
Neither party shall be liable for consequential damages.

         (k)      This Agreement constitutes the entire agreement among the
parties hereto with respect to the subject matter hereof There are no
restrictions, promises, warranties or undertakings, other than those set forth
or referred to herein. This Agreement supersedes all prior agreements and
understandings among the parties hereto with respect to the subject matter
hereof This Agreement may be amended only by an instrument in writing signed by
the party to be charged with enforcement thereof.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


                                       11
<PAGE>

         IN WITNESS WHEREOF, the parties have caused this Agreement to be duly
executed by their respective officers thereunto duly authorized as of the day
and year first above written.

                                        COMPANY:
                                        CALLISTO PHARMACEUTICALS, INC.



                                        By:
                                               ---------------------------------
                                        Name:
                                               ---------------------------------
                                        Title:
                                               ---------------------------------


                                        INITIAL INVESTOR:



                                        ----------------------------------------
                                            [Print Name of Initial Investor]


                                        By:
                                               ---------------------------------
                                        Name:
                                               ---------------------------------
                                        Title:
                                               ---------------------------------


                                       12