<PAGE>
                                                                     EXHIBIT 4.3


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.

No. ___________                                                 For the Purchase
                                                                of 40,000 shares
                                                                 of Common Stock

                            WARRANT TO PURCHASE STOCK
                                       OF
                                 EXEGENICS INC.
                            (A DELAWARE CORPORATION)

      eXegenics Inc., a Delaware corporation (the "Company"), for value
received, hereby certifies that Petkevich & Partners, LLC (the "Holder"), is
entitled, subject to the vesting provisions and other terms set forth below, to
purchase from the Company, at any time or from time to time at or before the
earlier of 5:00 p.m. EST on March 5, 2008 (the "Expiration Date") and the
termination of this Warrant as provided in Section 8 hereof, Forty Thousand
(40,000) shares of Common Stock, par value $0.01 per share, of the Company (the
"Common Stock"), at a purchase price per share equal to fifty-eight cents
($0.58) per share (the "Base Price"), as adjusted upon the occurrence of certain
events as set forth in Section 3 of this Warrant. This Warrant shall vest and
become exercisable in quarterly increments as follows: (a) this Warrant shall
vest and become exercisable with respect to Ten Thousand (10,000) shares of
Common Stock on March 5, 2003; (b) this Warrant shall vest and become
exercisable with respect to another Ten Thousand (10,000) shares of Common Stock
on June 5, 2003; (c) this Warrant shall vest and become exercisable with respect
to another Ten Thousand (10,000) shares of Common Stock on September 5, 2003;
and (d) this Warrant shall vest and become exercisable with respect to the
remaining Ten Thousand (10,000) shares of Common Stock on December 5, 2003. The
shares of stock issuable upon exercise of this Wan-ant, and the purchase price
per share, are hereinafter referred to as the "Warrant Stock" and the "Purchase
Price," respectively.

l. Exercise.

      1.1 Manner of Exercise; Payment in Cash. This Warrant may be exercised by
the Holder, in whole or in part, by surrendering this Warrant, with the purchase
form appended hereto as Exhibit A duly executed by the Holder, at the principal
office of the Company, or at such other place as the Company may designate,
accompanied by payment in full of the Purchase Price payable in respect of the
number of shares of Warrant Stock purchased upon such exercise. Payment of the
Purchase Price shall be in cash or by certified or official bank check payable
to the order of the Company.

      1.2 Effectiveness. Each exercise of this Warrant shall be deemed to have
been effected immediately prior to the close of business on the day on which
this Wan-ant shall have been surrendered to the Company as provided in Section
1.1 above. At such time, the person or persons in whose name or names any
certificates for Warrant Stock shall be issuable upon such exercise as provided
in Section 1.3 below shall be deemed to have become the holder or holders of
record of the Warrant Stock represented by such certificates.
<PAGE>

      1.3. Delivery of Certificates. As soon as practicable after the exercise
of this Warrant in full or in part, and in any event within ten (10) business
days thereafter, the Company at its sole expense will cause to be issued in the
name of, and delivered to, the Holder, or, subject to the terms and conditions
hereof; as such Holder (upon payment by such Holder of any applicable transfer
taxes) may direct:

            (a) A certificate or certificates for the number of full shares of
Warrant Stock to which such Holder shall be entitled upon such exercise plus, in
lieu of any fractional share to which such Holder would otherwise be entitled,
cash in an amount determined pursuant to Section 2 hereof, and

            (b) In case such 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 of Warrant Stock (without giving effect
to any adjustment therein) equal to the number of such shares called for on the
face of this Warrant minus the number of such shares purchased by the Holder
upon such exercise as provided in Section 1.1 above.

2. Fractional Shares. The Company shall not be required upon the exercise of
this Warrant to issue any fractional shares, but shall make an adjustment
therefor in cash on the basis of the fair market value of the Warrant Stock
reasonably determined by the Board of Directors of the Company.

3. Certain Adjustments.

      3.1 Changes in Common Stock. If the Company shall (i) combine the
outstanding shares of Common Stock into a lesser number of shares, (ii)
subdivide the outstanding shares of Common Stock into a greater number of
shares, or (iii) issue additional shares of Common Stock as a dividend or other
distribution with respect to the Common Stock, the number of shares of Warrant
Stock shall be equal to the number of shares which the Holder would have been
entitled to receive after the happening of any of the events described above if
such shares had been issued immediately prior to the happening of such event,
such adjustment to become effective concurrently with the effectiveness of such
event. The Purchase Price in effect immediately prior to any such combination of
Common Stock shall, upon the effectiveness of such combination, be
proportionately increased. The Purchase Price in effect immediately prior to any
such subdivision of Common Stock or at the record date of such dividend shall
upon the effectiveness of such subdivision or immediately after the record date
of such dividend be proportionately reduced.

      3.2 Reorganizations and Reclassifications. If there shall occur any
capital reorganization or reclassification of the Common Stock (other than a
change in par value or a subdivision or combination as provided for in Section
3.1), then, as part of any such reorganization or reclassification, lawful
provision shall be made so that the Holder shall have the right thereafter to
receive upon the exercise hereof the kind and amount of shares of stock or other
securities or property which such Holder would have been entitled to receive it
immediately prior to any such reorganization or reclassification, such Holder
had held the number of shares of Common Stock which were then purchasable upon
the exercise of this Warrant. In any such case, appropriate adjustment (as
reasonably determined by the Board of Directors of the Company) shall be made in
the application of the provisions set forth herein with respect to the rights
and interests thereafter of the Holder such that the provisions set forth in
this Section 3 (including provisions with respect to adjustment of the Purchase
Price) shall thereafter be applicable, as nearly as is reasonably practicable,
in relation to any shares of stock or other securities or property thereafter
deliverable upon the exercise of this Warrant

      3.3 Certificate of Adjustment. When any adjustment is required to be made
in the Purchase Price, the Company shall promptly mail to the Holder a
certificate setting forth the Purchase Price after such adjustment and setting
forth a brief statement of the facts requiring such adjustment. Delivery of such
certificate shall be deemed to be a final and binding determination with respect
to such adjustment unless challenged by the Holder within ten (10) days of
receipt thereof. Such certificate shall also set forth the kind and amount of
stock or other securities or property into which this Warrant shall be
exercisable following the occurrence of any of the events specified in this
Section 3.
<PAGE>
4. Compliance with Securities Act.

      4.1 Unregistered Securities. The Holder acknowledges that this Wan-ant and
the Warrant Stock 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 Wan-ant Stock in the
absence of (i) an effective registration statement under the Securities Act
covering this Warrant or such Wan-ant Stock and registration or qualification of
this Warrant or such Wan-ant Stock 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 Warrant Stock 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).

      4.2 Investment Letter. Without limiting the generality of Section 4.1,
unless the offer and sale of any shares of Warrant Stock shall have been
effectively registered under the Securities Act, the Company shall be under no
obligation to issue the Warrant Stock unless and until the 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 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.

      4.3 Legend. Certificates delivered to the Holder pursuant to Section 1.3
shall bear the following legend or a legend in substantially similar form:

            "THE SHARES REPRESENTED BY THIS CERTMCATE HAVE BEEN TAKEN FOR
      INVESTMENT AND THEY MAY NOT BE SOLD OR OTHERWISE TRANSFERRED BY ANY
      PERSON, INCLUDING A PLEDGEE, IN THE ABSENCE OF AN EFFECTIVE REGISTRATION
      STATEMENT FOR THE SHARES UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR
      AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY, THAT AN EXEMPTION FROM
      REGISTRATION IS THEN AVAILABLE."

5. Reservation of Stock. The Company will at all times reserve and keep
available, solely for issuance and delivery upon the exercise of this Warrant,
such shares of Warrant Stock and other stock, securities and property, as from
time to time shall be issuable upon the exercise of this Warrant. The Company
covenants that all shares of Warrant Stock so issuable will, when issued, be
duly and validly issued and fully paid and nonassessable.

6. Registration Rights.

      6.1. "Piggy Back" Registration. If at any time the Company shall determine
to register under the Securities Act, any of its Common Stock, other than on
Form S-8, Form S-4 or their then equivalents, it shall send to the Holder
written notice of such determination and, if within thirty (30) days after
receipt of such notice, the: Holder shall so request in writing, the Company
shall use its best efforts to include in such registration statement all or any
part of the Warrant Stock except that if, in connection with any offering
involving an underwriting of Common Stock to be issued by the Company, the
managing underwriter shall impose a limitation on the number of shares of such
Common Stock which may be included in any such registration statement because,
in its judgment, such limitation is necessary to effect an orderly public
distribution, and such limitation is imposed pro rata among the holders of such
Common Stock having an incidental ("piggyback") right to include such Common
Stock in the registration statement according to the amount of such. Common
Stock which each holder had requested to be included pursuant to such right,
then the Company shall be obligated to include in such registration statement
only such limited portion of the Warrant Stock with respect to which the Holder
has requested inclusion hereunder.
<PAGE>
      6.2. Effectiveness. The Company will use its.best efforts to maintain the
effectiveness for up to six (6) months of any registration statement pursuant to
which any of the Warrant Stock is being offered, and from time to time will
amend or supplement such registration statement and the prospectus contained
therein as and to the extent necessary to comply with the Securities Act and any
applicable state securities statute or regulation. The Company will also provide
the Holder with as many copies of the prospectus contained in any such
registration statement as it may reasonably request.

      6.3. Indemnification of Company. In the event that the Company registers
any of the Warrant Stock under the Securities Act, the Holder will indemnify and
hold harmless the Company, each of its directors, each of its officers who have
signed the registration statement, each underwriter of the shares so registered
(including any broker or dealer through whom such of the shares may be sold) and
each person, if any, who controls the Company within the meaning of Section 15
of the Securities Act from and against any and all losses, claims, damages,
expenses or liabilities, joint or several, to which they or any of them may
become subject under the Securities Act or under any other statute or at common
law or otherwise, and, except as hereinafter provided, will reimburse the
Company and each such director, officer, underwriter or controlling person for
any legal or other expenses reasonably incurred by them or any of them in
connection with investigating or defending any actions whether or not resulting
in any liability, insofar as such losses, claims, damages, expenses, liabilities
or actions arise out of or are based upon any untrue statement or alleged untrue
statement of a material fact contained in the registration statement, in any
preliminary or amended preliminary prospectus or in the prospectus (or in the
registration statement or prospectus as from time to time amended or
supplemented) or arise out of or are based upon the omission or alleged omission
to state therein a material fact required to be stated therein or necessary in
order to make the statements therein not misleading, but only insofar as any
such statement or omission was made in reliance upon and in conformity with
information furnished in writing to the Company in connection therewith by the
Holder expressly for use therein. Promptly after receipt of notice of the
commencement of any action in respect of which indemnity may-be sought against
the Holder, the Company will notify the Holder in writing of the commencement
thereof and the Holder shall, subject to the provisions hereinafter stated,
assume the defense of such action (including the employment of counsel, who
shall be counsel reasonably satisfactory to the Company) and the payment of
expenses insofar as such action shall relate to the alleged liability in respect
of which indemnity may be sought against the Holder. The Company and each such
director, officer, underwriter or controlling person shall have the right to
employ separate counsel in any such action and to participate in the defense
thereof but the fees and expenses of such counsel shall not be at the expense of
the Holder unless employment of such counsel has been specifically authorized by
the Holder. The Holder shall not be liable to indemnify any person for any
settlement of any such action effected without the Holder's consent.

7. Replacement of Warrants. Upon 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) upon delivery of an indemnity
agreement (with surety if reasonably required) in an amount reasonably
satisfactory to the Company, or (in the case of mutilation) upon surrender and
cancellation of this Warrant, the Company will issue, in lieu thereof, a new
Warrant of lice tenor.

8. Termination Upon Certain Events. If there shall be a merger or consolidation
of the Company with or into another corporation (other than a merger or
reorganization involving only a change in the state of incorporation of the
Company or the acquisition by the Company of other businesses where the Company
survives as a going concern), or the sale of all or substantially all of the
Company's capital stock or assets to any other person, or the liquidation or
dissolution of the Company, then as a part of such transaction, at the Company's
option, either:

      (a) provision shall be made so that the Holder shall thereafter be
entitled to receive the number of shares of stock or other securities or
property of the Company, or of the successor corporation resulting from the
merger, consolidation or sale, to which the Holder would have been entitled if
the Holder had exercised its rights pursuant to the Warrant immediately prior
thereto (and, in such case, appropriate adjustment shall be made in the
application of the provisions of this Section 8(a) to the end that


<PAGE>
the provisions of this Section 3 shall be applicable after that event in as
nearly equivalent a manner as may be practicable); or

      (b) this Warrant shall terminate: on the effective date of such merger,
consolidation or sale (the "Termination Date") and become null and void,
provided that if this Warrant shall not have otherwise terminated or expired,
(1) the Company shall have given the Holder written notice of such Termination
Date at least twenty (20) business days prior to the occurrence thereof and (2)
the Holder shall have the right until 5:00 p.m., Eastern Standard Time, on the
day immediately prior to the Termination Date to exercise its rights hereunder
to the extent not previously exercised.

9. 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 9, or the levy of any attachment or similar
process upon the Warrant or such rights, shall be null and void.

10. No Rights as Stockholder. Until the exercise of this Warrant, the Holder
shall not have or exercise any rights by virtue hereof as a stockholder of the
Company.

11. Notices. All notices, requests and other communications hereunder shall be
in writing, shall be either (i) delivered by hand, (ii) made by telex, telecopy
or facsimile transmission, (iii) sent by overnight courier, or (iv) sent by
registered mail, postage prepaid, return receipt requested. In the case of
notices from the Company to the Holder, they shall be sent to the address
furnished to the Company in writing by the last Holder who shall have furnished
an address to the Company in writing. All notices from the Holder to the Company
shall be delivered to the Company at its offices at 2110 Research Row, Dallas,
Texas 75235 or such other address as the Company shall so notify the Holder. All
notices, requests and other communications hereunder shall be deemed to have
been given (i) by hand, at the: time of the delivery thereof to the receiving
party at the address of such party described above, (ii) if made by telex,
telecopy or facsimile transmission, at the time that receipt thereof has been
acknowledged by electronic confirmation or otherwise, (iii) if sent by overnight
courier, on the next business day following the day such notices is delivered to
the courier service, or (iv) if sent by registered mail, on the fifth business
day following the day such mailing is made.

12. Waivers and Modifications. Any term or provision of this Warrant may be
waived only by written document executed by the party entitled to the benefits
of such terms or provisions. The terms and provisions of this Warrant may be
modified or amended only by written agreement executed by the parties hereto.

13. Headings. The headings in this Warrant are for convenience of reference only
and shall in no way modify -------- or affect the meaning or construction of any
of the terms or provisions of this Warrant.

14. Governing Law. This Warrant will be governed by and construed in accordance
with and governed by the laws of Delaware, without giving effect to the conflict
of law principles thereof.


                                              eXegenics Inc.


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

<PAGE>
EXHIBIT A
PURCHASE FORM

To: eXegenics Inc.

      The undersigned pursuant to the provisions set forth in the attached
Warrant (No. W-_________), hereby irrevocably elects to purchase ___________
shares of the Common Stock, par value $0.01 per share (the "Common Stock") of
eXegenics Inc., covered by such Warrant and herewith makes payment of
$______________, representing the full purchase price for such shares at the
price per share provided for in such Warrant.

The Common Stock for which the Warrant may be exercised shall be known herein as
the "Warrant Stock".

      The undersigned is aware that the Warrant Stock has not been and will not
be registered under the Securities Act of 1933, as amended (the "Securities
Act") or any state securities laws. The undersigned understands that reliance by
the Company on exemptions under the Securities Act is predicated in part upon
the truth and accuracy of the statements of the undersigned in this Purchase
Form.

      The undersigned represents and warrants that (1) it has been furnished
with all information which it deems necessary to evaluate the merits and risks
of the purchase of the Warrant Stock, (2) it has had the opportunity to ask
questions concerning the Warrant Stock and the Company and all questions posed
have been answered to its satisfaction, (3) it has been given the opportunity to
obtain any additional information it deems necessary to verify the accuracy of
any information obtained concerning the Warrant Stock and the Company and (4) it
has such knowledge and experience in financial and business matters that it is
able to evaluate the merits and risks of purchasing the Warrant Stock and to
make an informed investment decision relating thereto.

      The undersigned hereby represents and warrant that it is purchasing the
Warrant Stock for its own account for investment and not with a view to the sale
or distribution of all or any part of the Warrant Stock.

      The undersigned understands that because the Warrant Stock has not been
registered under the Securities Act, it must continue to bear the economic risk
of the investment for an indefinite period of time and the Warrant Stock cannot
be sold unless it is subsequently registered under applicable federal and state
securities laws or an exemption from such registration is available.

      The undersigned agrees that it will in no event sell or distribute or
otherwise dispose of all or any part of the Warrant Stock unless (1) there is an
effective registration statement under the Securities Act and applicable state
securities laws covering any such transaction involving the Warrant Stock, or
(2) the Company receives an opinion satisfactory to the Company of the
undersigned's legal counsel stating that such transaction is exempt from
registration. The undersigned consents to the placing of a legend on its
certificate for the Warrant Stock stating that the Warrant Stock has not been
registered and setting forth the restriction on transfer contemplated hereby and
to the placing of a stop transfer order on the books of the Company and with any
transfer agents against the Warrant Stock until the Warrant Stock may be legally
resold or distributed without restriction.

      The undersigned has considered the federal and state income tax
implications of the exercise of the Warrant and the purchase and subsequent sale
of the Warrant Stock.

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

                                                Dated:
                                                       -------------------------