Document:

<PAGE>

                                                                     Exhibit 4.3

     THIS WARRANT AND ANY SECURITIES ACQUIRED UPON THE EXERCISE OF THIS WARRANT
HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED ("THE
SECURITIES ACT"), OR ANY STATE SECURITIES LAWS AND NEITHER THE SECURITIES NOR
ANY INTEREST THEREIN MAY BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR OTHERWISE
DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH
ACT OR SUCH LAWS OR AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT AND SUCH LAWS.

                     ______________________________________

                          DISCOVERY THERAPEUTICS, INC.

                          COMMON STOCK PURCHASE WARRANT

                     ______________________________________

     This certifies that, for good and valuable consideration, Discovery
Therapeutics, Inc., a Delaware corporation (the "Company"), grants to Gerard
Klauer Mattison & Co., Inc., or registered assigns (the "Warrantholder"), the
right to subscribe for and purchase from the Company 136,400 validly issued,
fully paid and nonassessable shares (the "Warrant Shares") of the Company's
Common Stock, par value $0.001 per share (the "Common Stock"), at the purchase
price per share of $6.00 (the "Exercise Price"), from time to time, prior to
5:00 PM Eastern Standard Time on March 30, 2006 (the "Expiration Date"), all
subject to the terms, conditions and adjustments herein set forth.

Certificate No. CW-1
                ------

Number of Shares: 136,400
                  -------

Name of Warrantholder: Gerard Klauer Mattison & Co., Inc.

<PAGE>

     1.   Duration and Exercise of Warrant; Limitation on Exercise; Payment of
          --------------------------------------------------------------------
Taxes.
-----

          1.1. Duration and Exercise of Warrant. Subject to the terms and
               --------------------------------
conditions set forth herein, the Warrant may be exercised, in whole or in part,
by the Warrantholder by:

               1.1.1. the surrender of this Warrant to the Company, with a duly
executed Exercise Form specifying the number of Warrant Shares to be purchased,
during normal business hours on any Business Day prior to the Expiration Date;
and

               1.1.2. the delivery of payment to the Company, for the account
of the Company, by cash or by certified or bank cashier's check, of the Exercise
Price for the number of Warrant Shares specified in the Exercise Form in lawful
money of the United States of America. The Company agrees that such Warrant
Shares shall be deemed to be issued to the Warrantholder as the record holder of
such Warrant Shares as of the close of business on the date on which this
Warrant shall have been surrendered and payment made for the Warrant Shares as
aforesaid (or as provided in Section 1.2 below).

          1.2. Conversion Right.
               ----------------

               1.2.1. In lieu of the payment of the Exercise Price, the
Warrantholder shall have the right (but not the obligation), to require the
Company to convert this Warrant, in whole or in part, into shares of Common
Stock (the "Conversion Right") as provided for in this Section 1.2. Upon
exercise of the Conversion Right, the Company shall deliver to the Warrantholder
(without payment by the Warrantholder of any of the Exercise Price; provided,
                                                                    --------
however, that the Warrantholder shall be required to pay the par value for any
-------
shares of Common Stock so delivered) that number of shares of Common Stock equal
to the quotient obtained by dividing (x) the value of the Warrant at the time
the Conversion Right is exercised (determined by subtracting the aggregate
Exercise Price in effect immediately prior to the exercise of the Conversion
Right from the aggregate Fair Market Value for the shares of Common Stock
issuable upon exercise of the Warrant immediately prior to the exercise of the
Conversion Right) by (y) the Fair Market Value of one share of Common Stock
immediately prior to the exercise of the Conversion Right.

               1.2.2. The Conversion Right may be exercised by the Warrantholder
on any Business Day prior to the Expiration Date by delivering the Warrant
Certificate, together with a duly executed Exercise Form (with the conversion
section completed) and the par value for any shares of Common Stock deliverable
pursuant to such conversion, to the Company, exercising the Conversion Right and
specifying the total number of shares of Common Stock the Warrantholder will be
issued pursuant to such conversion.

               1.2.3. Fair Market Value of a share of Common Stock as of a
particular date (the "Determination Date") shall mean:

               1.2.3.1.  If the Common Stock is listed on a national securities
exchange, then the Fair Market Value shall be the average of the last ten "daily
sales prices" of the Common Stock on the principal national securities exchange
on which the Common Stock is listed or admitted for trading on the last ten
Business Days prior to the Determination Date, or if

                                        3

<PAGE>

not listed or traded on any such exchange, then the Fair Market Value shall be
the average of the last ten "daily sales prices" of the Common Stock on the
National Market (the "National Market") of the National Association of
Securities Dealers Automated Quotations System ("Nasdaq") on the last ten
Business Days prior to the Determination Date. The "daily sales price" shall be
the closing price of the Common Stock at the end of each day; or

          1.2.3.2. If the Common Stock is not so listed or admitted to unlisted
trading privileges or if no such sale is made on at least nine of such days,
then the Fair Market Value shall be the fair value as reasonably determined in
good faith by the Company's Board of Directors or a duly appointed committee of
the Board (which determination shall be reasonably described in the written
notice delivered to the Warrantholder together with the Common Stock
certificates).

     1.3. Limitations on Exercise. Notwithstanding anything to the contrary
          -----------------------
herein, this Warrant may be exercised only upon the delivery to the Company of
any certificates, legal opinions, or other documents reasonably requested by the
Company to satisfy the Company that the proposed exercise of this Warrant may be
effected without registration under the Securities Act. The Warrantholder shall
not be entitled to exercise this Warrant, or any part thereof, unless and until
such certificates, legal opinions or other documents are reasonably acceptable
to the Company.

     1.4. Warrant Shares Certificate. A stock certificate or certificates
          --------------------------
for the Warrant Shares specified in the Exercise Form shall be delivered to the
Warrantholder within ten Business Days after receipt of the Exercise Form and
receipt of payment of the purchase price if the Conversion Right is not
exercised. If this Warrant shall have been exercised only in part, the Company
shall, at the time of delivery of the stock certificate or certificates, deliver
to the Warrantholder a new Warrant evidencing the rights to purchase the
remaining Warrant Shares, which new Warrant shall in all other respects be
identical with this Warrant.

     1.5. Payment of Taxes. The issuance of certificates for Warrant Shares
          ----------------
shall be made without charge to the Warrantholder for any stock transfer or
other issuance tax in respect thereto; provided, however, that the Warrantholder
                                       --------  -------
shall be required to pay any and all taxes which may be payable in respect of
any transfer involved in the issuance and delivery of any certificate in a name
other than that of the then Warrantholder as reflected upon the books of the
Company.

     1.6. Divisibility of Warrant; Transfer of Warrant.
          --------------------------------------------

          1.6.1. Subject to the provisions of this Section 1.6, this Warrant may
be divided into warrants of one thousand shares or multiples thereof, upon
surrender at the principal office of the Company, without charge to any
Warrantholder. Upon such division, the Warrants may be transferred of record as
the then Warrantholder may specify without charge to such Warrantholder (other
than any applicable transfer taxes). In addition, subject to the provisions of
this Section 1.6, the Warrantholder shall also have the right to transfer this
Warrant in its entirety to any person or entity.

                                        4

<PAGE>

               1.6.2. Upon surrender of this Warrant to the Company with a duly
executed Assignment Form and funds sufficient to pay any transfer tax, the
Company shall, without charge, execute and deliver a new Warrant or Warrants of
like tenor in the name of the assignee named in such Assignment Form, and this
Warrant shall promptly be canceled. Each Warrantholder agrees that prior to any
proposed transfer (whether as the result of a division or otherwise) of this
Warrant, such Warrantholder shall give advance written notice to the Company of
such Warrantholder's intention to effect such transfer. Each such notice shall
describe the manner and circumstances of the proposed transfer in reasonably
sufficient detail, and, if reasonably requested by the Company, shall be
accompanied by a written opinion of legal counsel, which opinion shall be
addressed to the Company and be reasonably satisfactory in form and substance to
the Company's counsel, to the effect that the proposed transfer of this Warrant
may be effected without registration under the Securities Act. In addition, the
Warrantholder and the transferee shall execute any documentation reasonably
required by the Company to ensure compliance with the Securities Act. The
Warrantholder shall not be entitled to transfer this Warrant, or any part
thereof, if such legal opinion is not reasonably acceptable to the Company or if
such documentation is not provided. The term "Warrant" as used in this Agreement
shall be deemed to include any Warrants issued in substitution or exchange for
this Warrant.

          1.7. Fractional Shares. No fractional shares or script representing
               -----------------
fractional shares shall be issued upon the exercise of this Warrant. With
respect to any fraction of a share called for upon exercise hereof, the Company
shall pay to the Warrantholder an amount in cash equal to such fraction
multiplied by the current Fair Market Value of a share.

     2.   Restrictions on Transfer; Restrictive Legends.
          ---------------------------------------------

     Except as otherwise permitted by this Section 2, each Warrant shall (and
each Warrant issued upon direct or indirect transfer or in substitution for any
Warrant pursuant to Section 1.6 or Section 4 shall) be stamped or otherwise
imprinted with a legend in substantially the following form:

               THIS WARRANT AND ANY SECURITIES ACQUIRED UPON THE EXERCISE OF
          THIS WARRANT HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
          1933, AS AMENDED, OR ANY STATE SECURITIES LAWS AND NEITHER THE
          SECURITIES NOR ANY INTEREST THEREIN MAY BE OFFERED, SOLD, TRANSFERRED,
          PLEDGED OR OTHERWISE DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE
          REGISTRATION STATEMENT UNDER SUCH ACT OR SUCH LAWS OR AN EXEMPTION
          FROM REGISTRATION UNDER SUCH ACT AND SUCH LAWS.

Except as otherwise permitted by this Section 2, each stock certificate for
Warrant Shares issued upon the exercise of any Warrant and each stock
certificate issued upon the direct or indirect transfer of any such Warrant
Shares shall be stamped or otherwise imprinted with a legend in substantially
the following form:

               THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
          REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE
          SECURITIES LAWS AND NEITHER THE SECURITIES NOR ANY

                                        5

<PAGE>

     INTEREST THEREIN MAY BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR OTHERWISE
     DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER
     SUCH ACT OR SUCH LAWS OR AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT AND
     SUCH LAWS.

          THE WARRANT SHARES ARE SUBJECT TO A RIGHT OF FIRST REFUSAL OPTION IN
     FAVOR OF THE COMPANY AND ITS OTHER STOCKHOLDERS, AS PROVIDED IN THE BYLAWS
     OF THE COMPANY.

          INFORMATION REGARDING THE DESIGNATIONS, RELATIVE RIGHTS, PREFERENCES
     AND LIMITATIONS APPLICABLE TO EACH CLASS OR SERIES OF CAPITAL STOCK OF THE
     COMPANY, THE VARIATIONS THEREIN AND THE AUTHORITY OF THE BOARD OF DIRECTORS
     TO DETERMINE VARIATIONS FOR FUTURE CLASSES OR SERIES MAY BE OBTAINED AT NO
     COST BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD HEREOF TO THE
     SECRETARY OF THE COMPANY AT THE PRINCIPAL EXECUTIVE OFFICE OF THE COMPANY.

     Notwithstanding the foregoing, the Warrantholder may require the Company to
issue a Warrant or a stock certificate for Warrant Shares, in each case without
a legend, if either (i) such Warrant or such Warrant Shares, as the case may be,
have been registered for resale under the Securities Act or (ii) the
Warrantholder has delivered to the Company an opinion of legal counsel, which
opinion shall be addressed to the Company and be reasonably satisfactory in form
and substance to the Company's counsel, to the effect that such registration is
not required with respect to such Warrant or such Warrant Shares, as the case
may be.

     3.   Reservation and Registration of Shares, Etc.  The Company covenants
          --------------------------------------------
and agrees as follows:

          3.1. all Warrant Shares which are issued upon the exercise of this
Warrant will, upon issuance, be validly issued, fully paid, and nonassessable,
not subject to any preemptive rights, and free from all taxes, liens, security
interests, charges, and other encumbrances with respect to the issue thereof,
other than taxes with respect to any transfer occurring contemporaneously with
such issue;

          3.2. during the period within which this Warrant may be exercised, the
Company will at all times have authorized and reserved, and keep available free
from preemptive rights, a sufficient number of shares of Common Stock to provide
for the exercise of the rights represented by this Warrant; and

          3.3. the Company will, from time to time, take all such action as may
be required to assure that the par value per share of the Warrant Shares is at
all times equal to or less than the then effective Exercise Price.

                                        6

<PAGE>

     4. Loss or Destruction of Warrant.
        ------------------------------

     Subject to the terms and conditions hereof, upon receipt by the Company of
evidence reasonably satisfactory to it of the loss, theft, destruction or
mutilation of this Warrant (including, but not limited to, an affidavit of the
Warrantholder) and, in the case of loss, theft or destruction, of such bond or
indemnification as the Company may reasonably require, and, in the case of such
mutilation, upon surrender and cancellation of this Warrant, the Company will
execute and deliver a new Warrant of like tenor.

     5. Ownership of Warrant.
        --------------------

     The Company may deem and treat the person in whose name this Warrant is
registered as the holder and owner hereof (notwithstanding any notations of
ownership or writing hereon made by anyone other than the Company) for all
purposes and shall not be affected by any notice to the contrary, until
presentation of this Warrant for registration of transfer.

     6. Company Representations. The Company hereby represents and warrants to
        -----------------------
the Warrantholder that:

        6.1. This Warrant has been duly authorized and executed by the Company
and is a valid and binding obligation of the Company enforceable in accordance
with its terms, subject to applicable bankruptcy, insolvency, reorganization,
moratorium or other laws of general application affecting the enforcement of
creditors' rights.

        6.2. The execution and delivery of this Warrant are not, and the
issuance of the Warrant Shares upon exercise of this Warrant in accordance with
the terms hereof will not be, inconsistent with the Company's Certificate of
Incorporation or Bylaws, do not and will not contravene any law, governmental
rule or regulation, judgment or order applicable to the Company, and do not and
will not conflict with or contravene any provision of, or constitute a material
default under, any material indenture, mortgage, contract or other instrument of
which the Company is a party or by which it is bound or require the consent or
approval of, the giving of notice to, the registration or filing with or the
taking of any action in respect of or by, any federal, state or local government
authority or agency (other than such consents, approvals, notices, actions,
filings, etc., as have already been obtained or made, as the case may be).

     7. Adjustment of Exercise Price and Number of Warrant Shares; Record Date.
        ----------------------------------------------------------------------
The number of Warrant Shares issuable upon the exercise of this Warrant and the
Exercise Price shall be subject to adjustment from time to time upon the
occurrence of certain events, as follows:

        7.1. Adjustment for Dividends in Stock. In case at any time or from time
             ---------------------------------
to time the holders of shares of the Common Stock shall have received or, on or
after the record date fixed for the determination of eligible stockholders,
shall have become entitled to receive, without payment therefor, other or
additional stock of the Company by way of dividend then, and in each case, the
Warrantholder shall, upon the exercise hereof, be entitled to receive, in
addition to the number of Warrant Shares receivable thereupon, and without
payment of any additional consideration therefor, the amount of such other or
additional stock of the Company which such Warrantholder would hold on the date
of such exercise had it been the holder of

                                       7

<PAGE>

record of shares of the Common Stock on the date hereof and had thereafter,
during the period from the date hereof to and including the date of such
exercise, retained such shares and/or all other additional stock receivable by
it as aforesaid during such period, giving effect to all adjustments called for
during such period by Sections 7.2 and 7.3.

          7.2. Reclassification, Reorganization or Merger. In case of any
               ------------------------------------------
reclassification, capital reorganization or other change of outstanding shares
of the Common Stock, or in the case of any consolidation or merger of the
Company with or into another corporation (other than a merger with a subsidiary
in which merger the Company is the continuing corporation and which does not
result in any reclassification, capital reorganization or other change of
outstanding shares of Common Stock or a change of more than 25% of the voting
power of the Common Stock) or in the case of any sale, lease or conveyance to
another corporation of the property of the Company as an entirety, the Company
shall, as a condition precedent to such transaction, cause effective provisions
to be made so that the Warrantholder shall have the right thereafter by
exercising this Warrant at any time prior to the expiration of the Warrant, to
purchase the kind and amount of shares of stock and other securities and
property receivable upon such reclassification, capital reorganization and other
change, consolidation, merger, sale or conveyance by a holder of the number of
shares of Common Stock that might have been purchased upon exercise of this
Warrant immediately prior to such reclassification, change, consolidation,
merger, sale or conveyance. Any such provision shall include provision for
adjustments that shall be as nearly equivalent as may be practicable to the
adjustments provided for in this Warrant. The foregoing provisions of this
Section 7.2 shall similarly apply to successive reclassifications, capital
reorganizations and changes of shares of Common Stock and to successive
consolidations, mergers, sales or conveyances. In the event that in connection
with any such capital reorganization or reclassification, consolidation, merger,
sale or conveyance, additional shares of Common Stock shall be issued in
exchange, conversion, substitution or payment, in whole or in part, for
securities of the Company other than Common Stock, any such issue shall be
treated as an issue of Common Stock covered by the provisions of Section 7.1.

          7.3. Stock Splits and Reverse Stock Splits. If the Company shall
               -------------------------------------
subdivide its outstanding shares of Common Stock into a greater number of
shares, the Exercise Price in effect immediately prior to such subdivision shall
thereby be proportionately reduced and the number of Warrant Shares receivable
upon exercise of this Warrant shall thereby be proportionately increased; and,
conversely, if the outstanding number of shares of Common Stock shall be
combined into a smaller number of shares, the Exercise Price in effect
immediately prior to such combination shall thereby be proportionately increased
and the number of Warrant Shares receivable upon exercise of the Warrant shall
be proportionately decreased.

          7.4. Notices of Record Date, Etc. In the event of (a) any taking by
               ---------------------------
the Company of a record of the holders of any class of securities for the
purpose of determining the holders thereof who are entitled to receive any
dividend or other distribution (the "Distribution"), (b) any capital
reorganization or reclassification of the stated capital of the Company or any
consolidation or merger of the Company with any other corporation or
corporations (other than a wholly-owned subsidiary), or the sale or distribution
of all or substantially all of the Company's property and assets (the
"Reorganization Event"), or (c) any proposed filing of a registration statement
under the Act in connection with a primary public offering of the Company's
Common

                                        8

<PAGE>

Stock (the "Registration Event"), the Company will mail or cause to be mailed to
the Warrantholder a notice specifying (i) the date of any such Distribution
stating the amount and character of such Distribution, (ii) the date on which
any such Reorganization Event or Registration Event is expected to become
effective, and (iii) the time, if any, that is to be fixed as to when the
holders of record of the Company's securities shall be entitled to exchange
their shares of the Company's securities for securities or other property
deliverable upon such Reorganization Event. Such notice shall be mailed at least
thirty (30) days prior to the date therein specified.

          7.5.  Notice of Adjustments. Notice of any adjustment in this Warrant
                ---------------------
shall be given by the Company to the Warrantholder, and such adjustment (whether
or not such notice is given) shall be effective and binding for all purposes.

     8.   Registration Rights. The Warrantholder shall have the same
          -------------------
registration rights with respect to Registrable Shares as the Holders (as
defined in the Investor Rights Agreement (as defined below)) of Registrable
Securities (as defined in the Investor Rights Agreement) under Article 3 of that
certain Restated Investor Rights Agreement dated as of March 31, 1995, among the
Company, the Founders and the Investors named therein, as such agreement was
amended as of November 3, 1995, as of June 21, 1999, and as of February 21, 2001
(and as the same may be amended from time to time, the "Investor Rights
Agreement"); and all of the terms and provisions of such Article 3 (a copy of
which is attached as Exhibit C hereto), including without limitation Section
3.11 therein, shall apply to the Warrantholder and its Registrable Shares. The
Warrantholder agrees that it may include its Registrable Shares in any such
registration only to the extent that the inclusion of such Registrable Shares
will not diminish the amount of Registrable Securities (as defined in the
Investor Rights Agreement) which are included in such registration.

     9.   Amendments. Any provision of this Warrant (including registration
          ----------
rights) 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 the Warrantholders who hold a
majority in interest of the Registrable Shares. Any amendment or waiver effected
in accordance with this Section 9 shall be binding upon each Warrantholder and
the Company.

     10.  Expiration of the Warrant. Except with respect to the indemnification
          -------------------------
and contribution provisions set forth in Article 3 of the Investor Rights
Agreement and applicable pursuant to Section 8 hereof, the obligations of the
Company pursuant to this Warrant shall terminate on the Expiration Date.

     11.  Definitions.
          -----------

     As used herein, unless the context otherwise requires, the following terms
have the following respective meanings:

     Assignment Form: an Assignment Form in the form annexed hereto as Exhibit
     ---------------                                                   -------
B.
-

     Business Day: any day other than a Saturday, Sunday or a day on which
     ------------
national banks are authorized by law to close in The City of New York, State of
New York.

                                        9

<PAGE>

     Common Stock: the meaning specified on the cover of this Warrant.
     ------------

     Company: the meaning specified on the cover of this Warrant.
     -------

     Exercise Form: an Exercise Form in the form annexed hereto as Exhibit A.
     -------------                                                 ---------

     Exercise Price: the meaning specified on the cover of this Warrant.
     --------------

     Expiration Date:  the meaning specified on the cover of this Warrant.
     ---------------

     Fair Market Value:  the meaning specified in Section 1.2.3.
     -----------------

     Investor Rights Agreement:  the meaning specified in Section 8.
     -------------------------

     Nasdaq:  the meaning specified in Section 1.2.3.1.
     ------

     National Market:  the meaning specified in Section 1.2.3.1.
     ---------------

     Registrable Shares: (i) the shares of the Company's Common Stock issued or
     ------------------
issuable upon exercise of the Warrants and (ii) any securities issued or
issuable with respect to any securities referred to in subdivision (i) by way of
stock split, stock dividend, recapitalization, or similar event, which have not
been sold to the public.

     SEC: the Securities and Exchange Commission or any other Federal agency at
     ---
the time administering the Securities Act or the Securities Exchange Act of
1934, as amended, whichever is the relevant statute for the particular purpose.

     Securities Act: the meaning specified on the cover of this Warrant, or any
     --------------
similar Federal statute, and the rules and regulations of the SEC thereunder,
all as the same shall be in effect at the time. Reference to a particular
section of the Securities Act shall include a reference to the comparable
section, if any, of any such similar Federal statute.

     Warrantholder:  the meaning specified on the cover of this Warrant.
     -------------

     Warrant Shares:  the meaning specified on the cover of this Warrant.
     --------------

     12.  Miscellaneous.
          -------------

          12.1.  Entire Agreement. This Warrant constitutes the entire agreement
                 ----------------
between the Company and the Warrantholder with respect to the Warrants.

          12.2.  Binding Effects; Benefits. This Warrant shall inure to the
                 -------------------------
benefit of and shall be binding upon the Company and the Warrantholder and their
respective heirs, legal representatives, successors and assigns. Nothing in this
Warrant, expressed or implied, is intended to or shall confer on any person
other than the Company and the Warrantholder, or their respective heirs, legal
representatives, successors or assigns, any rights, remedies, obligations or
liabilities under or by reason of this Warrant.

          12.3.  Section and Other Headings. The section and other headings
                 --------------------------
contained in this Warrant are for reference purposes only and shall not be
deemed to be a part of this Warrant or to affect the meaning or interpretation
of this Warrant.

          12.4.  Pronouns. All pronouns and any variations thereof refer to the
                 --------
masculine, feminine or neuter, singular or plural, as the context may require.

                                       10

<PAGE>

          12.5. Further Assurances. Each of the Company and the Warrantholder
                ------------------
shall do and perform all such further acts and things and execute and deliver
all such other certificates, instruments and documents as the Company or the
Warrantholder may, at any time and from time to time, reasonably request in
connection with the performance of any of the provisions of this Warrant.

          12.6. Notices. All notices and other communications required or
                -------
permitted to be given under this Warrant shall be in writing and shall be deemed
to have been duly given if delivered personally or sent by United States mail,
postage prepaid, to the parties hereto at the following addresses or to such
other address as any party hereto shall hereafter specify by notice to the other
party hereto:

                12.6.1.   if to the Company, addressed to:

                          Discovery Therapeutics, Inc.
                          2028 Dabney Road, Suite E-17
                          Richmond, VA 23230
                          Attention: President

                12.6.2.   if to the Warrantholder, addressed to:
                          the address of such Warrantholder
                          appearing on the books of the Company.

Except as otherwise provided herein, all such notices and communications shall
be deemed to have been received on the date of delivery thereof, if delivered
personally, or on the third Business Day after the mailing thereof.

          12.7. Separability. Any term or provision of this Warrant which is
                ------------
invalid or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such invalidity or unenforceability without
rendering invalid or unenforceable the terms and provisions of this Warrant or
affecting the validity or enforceability of any of the terms or provisions of
this Warrant in any other jurisdiction.

          12.8. Governing Law. This Warrant shall be deemed to be a contract
                -------------
made under the laws of the State of Delaware and for all purposes shall be
governed by and construed in accordance with the laws of such State applicable
to such agreements made and to be performed entirely within such State.

          12.9. No Rights or Liabilities as Stockholder. Nothing contained in
                ---------------------------------------
this Warrant shall be determined as conferring upon the Warrantholder any rights
as a stockholder of the Company or as imposing any liabilities on the
Warrantholder to purchase any securities whether such liabilities are asserted
by the Company or by creditors or stockholders of the Company or otherwise.

                                       11

<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by its
duly authorized officer.

                        DISCOVERY THERAPEUTICS, INC.

                        By:   /s/ PETER G. SAVAS
                           ---------------------------------
                              Name:  Peter G. Savas
                              Title: President

Dated: July 18, 2001

                                       12

<PAGE>

                                    EXHIBIT A

                                  EXERCISE FORM
                                  -------------

                 (To be executed upon exercise of this Warrant)

           The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant, to purchase __________ of the Warrant Shares and
herewith tenders (i) payment for such Warrant Shares to the order of Discovery
Therapeutics, Inc. (the "Company") in the amount of $__________ or (ii) Warrants
to purchase __________ shares of Common Stock of the Company in order to
exercise the Conversion Right (as defined in Section 1.2 of this Warrant) and
payment of the par value for _________ of the Warrant Shares, in either case, in
accordance with the terms of this Warrant. The undersigned requests that a
certificate for such Warrant Shares be registered in the name of _______________
and that such certificates be delivered to __________________ whose address is
________________________________________________________________. (If this is a
partial exercise of the Warrant, a new Warrant for the remaining number of
unexercised Warrants shall be issued by the Company.)

Dated:___________

                     Signature_____________________________

                              _____________________________
                                      (Print Name)

                              _____________________________
                                      (Street Address)

                              _____________________________
                              (City) (State) (Zip Code)

Signed in the Presence of:

____________________________

<PAGE>
                                    EXHIBIT B

                                 ASSIGNMENT FORM
                                 ---------------

               (To be executed only upon transfer of this Warrant)

           For value received, the undersigned registered holder of the within
Warrant hereby sells, assigns and transfers unto ______________________ the
right represented by such Warrant to purchase ________________ shares of Common
Stock of Discovery Therapeutics, Inc. (the "Company") to which such Warrant
relates and all other rights of the Warrantholder under the within Warrant
(including, without limitation, the registration rights provided in Section 8 of
the within Warrant), and appoints _______________________ Attorney to make such
transfer on the books of the Company maintained for such purpose, with full
power of substitution in the premises.

Dated:______________

                         Signature_____________________________

                                  ______________________________
                                           (Print Name)

                                  ______________________________
                                           (Street Address)

                                  ______________________________
                                  (City) (State) (Zip Code)

Signed in the presence of:

_____________________________

<PAGE>

                                    EXHIBIT C

   Article 3 of the Restated Investor Rights Agreement dated as of March 31,
   ------------------------------------------------------------------------
    1995, among the Company, the Founders and the Investors named therein, as
    -------------------------------------------------------------------------
    such agreement was amended as of November 3, 1995, as of June 21, 1999, and
    ---------------------------------------------------------------------------
    as of February 21, 2001
    -----------------------<PAGE>
                                                                    Exhibit 10.1

                            INDEMNIFICATION AGREEMENT
                            -------------------------

                  This Indemnification Agreement is made as of this ___ day of
__________, ____, by and between Aderis Pharmaceuticals, Inc., a Delaware
corporation (the "Company") and _______________ ("Indemnitee").

                              W I T N E S S E T H:
                              -------------------

                  WHEREAS, the Company, in order to induce Indemnitee to serve
the Company as a _________, has agreed to provide Indemnitee with the benefits
contemplated by this Agreement;

                  WHEREAS, as a result of the provision of such benefits
Indemnitee has agreed to serve as a director of the Company;

                  WHEREAS, the By-laws of the Company and the Certificate of
Incorporation of the Company require the Company to indemnify its directors and
officers and others to the full extent permitted by law, and the Indemnitee has
agreed to serve as a director of the Company in part in reliance on such By-laws
and Certificate of Incorporation; and

                  WHEREAS, (x) in recognition of (A) Indemnitee's need for
protection against personal liability, in order to enhance Indemnitee's service
to the Company in an effective manner, and (B) Indemnitee's reliance on the
Company's By-laws and Certificate of Incorporation, and (y) in part to provide
Indemnitee with specific contractual assurance that the protection promised by
such By-laws and Certificate of Incorporation will be available to Indemnitee
(regardless of, among other things, any amendment to or revocation of such
By-laws or Certificate of Incorporation or any change in the composition of the
Board of Directors of the Company (the "Board") or Change of Control (as defined
in Section 1) of the Company), the Company wishes to provide in this Agreement
for the indemnification of and the advancing of expenses to Indemnitee to the
fullest extent (whether partial or complete) permitted by law and as set forth
in this Agreement, and, to the extent insurance is maintained, for the continued
coverage of Indemnitee under the Company's directors' and officers' liability
insurance policies;

                  NOW, THEREFORE, in consideration of these premises and of
Indemnitee's intention to serve the Company directly or, at the Company's
request (and with the Indemnitee's agreement), another enterprise, and,
intending to be legally bound hereby, the parties hereto agree as follows:

                  1.   Certain Definitions. The following terms shall have the
                       -------------------
meanings set forth below when such terms are used in this Agreement.

                       (a)    "Beneficial Owner" shall have the meaning given to
such term in Rule 13d-3 under the Exchange Act (as hereinafter defined);
provided, however, that Beneficial Owner shall exclude any Person (as
hereinafter defined) otherwise becoming a Beneficial Owner by reason of the
shareholders of the Company approving a merger of the Company with another
entity.

                                        1

<PAGE>
                     (b)    "Change of Control" means a change in control of the
Company of a nature that would be required to be reported in response to Item
6(e) of Schedule 14A of Regulation 14A promulgated under the Exchange Act,
whether or not the Company is in fact required to comply therewith; provided,
that, without limitation, a change in control shall be deemed to have occurred
if:

                            (i)   any Person or group of Persons, other than (A)

          a trustee or other fiduciary holding securities under an employee
          benefit plan of the Company, or (B) a corporation owned directly or
          indirectly by the stockholders of the Company in substantially the
          same proportions as their ownership of stock of the Company is or
          becomes the Beneficial Owner, directly or indirectly, of securities of
          the Company representing 15% or more of the combined voting power,

                            (ii)  during any period of two consecutive years
          (not including any period prior to the execution of this Agreement),
          individuals who at the beginning of such period constitute the Board
          and any new director whose election by the Board or nomination for
          election by the Company's stockholders was approved by a vote of at
          least 2/3 of the directors then still in office who either were
          directors at the beginning of the period or whose election or
          nomination for election was previously so approved, cease for any
          reason to constitute a majority thereof,

                            (iii) the effective date of a merger or
          consolidation of the Company with any other entity, other than a
          merger or consolidation which would result in the Voting Securities
          (as hereinafter defined) of the Company outstanding immediately prior
          to such merger or consolidation continuing to represent (either by
          remaining outstanding or by being converted into Voting Securities of
          the surviving entity) more than fifty-one percent (51%) of the
          combined voting power of the Voting Securities of the surviving entity
          outstanding immediately after such merger or consolidation and with
          the power to elect at least a majority of the board of directors or
          other governing body of such surviving entity,

                            (iv)  the stockholders of the Company approve or

          authorize a plan of complete liquidation of the Company or an
          agreement for the sale, lease, exchange, transfer or other disposition
          by the Company of (in one transaction or a series of transactions) all
          or substantially all of the Company's assets.

                     (c)    "Exchange Act" shall mean the Securities Act of
1934, as amended.

                     (d)    "Expenses" means all expenses, liabilities and
losses (including, without limitation, attorneys' and experts' fees and
expenses, costs, obligations, judgments, fines, interest, ERISA excise taxes,
penalties or assessments and amounts paid in settlement) incurred or suffered by
Indemnitee in connection with any Indemnifiable Event (as hereinafter defined)
(including, without limitation, in connection with, investigating, defending,
being a witness in or participating in (including on appeal), or preparing to
defend, be a witness in or participate in, any Proceeding (as hereinafter
defined) relating to any Indemnifiable Event.

                                        2

<PAGE>
                           (e)      "Independent Legal Counsel" means any
attorney or firm of attorneys, selected in accordance with the provisions of
Section 10, who shall not have otherwise performed services for the Company or
Indemnitee within the last five years (other than with respect to matters
concerning the rights of Indemnitee under this Agreement, or of other
Indemnitees under similar indemnity agreements).

                           (f)      "Person" shall have the meaning set forth in
Sections 13(d) and 14(d) of the Exchange Act; provided, however, that Person
shall exclude (i) the Company, (ii) any trustee or other fiduciary holding
securities under an employee benefit plan of the Company, and (iii) any
corporation owned, directly or indirectly, by the shareholders of the Company in
substantially the same proportions as their ownership of stock of the Company.

                           (g)      "Potential Change of Control" shall be
deemed to have occurred if:

                                    (i)     the Company enters into an
         agreement, the consummation of which would result in the occurrence of
         a Change of Control;

                                    (ii)    any Person, including the Company,
         publicly announces an intention to take or consider taking actions
         which if consummated would constitute a Change of Control;

                                    (iii)   any Person, other than the Company,

         any trustee or other fiduciary holding securities under an employee
         benefit plan of the Company or an corporation owned, directly or
         indirectly, by the stockholders of the Company in substantially the
         same proportions as their ownership of stock of the Company (A) is or
         becomes the Beneficial Owner, (B) discloses directly or indirectly to
         the Company or publicly a plan or intention to become the Beneficial
         Owner, or (C) makes a filing under the Hart-Scott-Rodino Antitrust
         Improvements Act of 1976, as amended, with respect to securities to
         become the Beneficial Owner, directly or indirectly, of securities
         representing 9.9% or more of the combined voting power of the
         outstanding Voting Securities of the Company; or

                                    (iv)    the Board adopts a resolution to the
         effect that, for purposes of this Agreement, a Potential Change of
         Control of the Company has occurred.

                           (h)      "Proceeding" means any threatened, pending
or completed (x) action, suit or proceeding, or (y) inquiry or investigation
that Indemnitee in good faith believes might lead to the institution of an
action, suit or proceeding, in each case, whether instituted by the Company or
any other party and whether civil, criminal, administrative, investigative or
other.

                           (i)      "Voting Securities" means any securities of
the Company which vote generally in the election of directors.

                  2.       Right to Indemnification. The Company shall indemnify
                           ------------------------
and hold harmless Indemnitee, as soon as practicable but in any event no later
than thirty days after written demand, in connection with any Proceeding to
which Indemnitee is a party or witness or

                                       3

<PAGE>

in which Indemnitee is otherwise involved, by reason of the fact that Indemnitee
is to become, is or was a director, officer, employee, consultant, agent or
fiduciary of the Company, or is to serve or is or was serving at the request of
the Company as a director, officer, employee, consultant, agent or fiduciary of
another corporation or of a partnership, joint venture, trust or other
enterprise, including, without limitation, service with respect to an employee
benefit plan, or by reason of anything done or not done by Indemnitee in any
such capacity (each such event, occurrence or circumstance in which Indemnitee
is entitled to indemnification pursuant to this Agreement, an "Indemnifiable
Event"), in each case to the fullest extent permitted by applicable law, as the
same exists or may hereafter be amended (but, in the case of any such amendment,
only to the extent that such amendment permits the Company to provide broader
indemnification rights than permitted prior thereto), against all Expenses,
incurred, suffered or paid by Indemnitee in connection therewith, and such
indemnification shall continue after Indemnitee has ceased to be a director,
officer, employee, consultant, agent or fiduciary of the Company and shall inure
to the benefit of Indemnitee's heirs, executors and administrators; provided,
                                                                    --------
however, that, except as provided in Section 5 hereof with respect to
-------
Proceedings to enforce rights to indemnification, the Company shall indemnify
Indemnitee in connection with a Proceeding (or part thereof) initiated by
Indemnitee only if such Proceeding (or part thereof) was authorized by the
Board.

                3. Right to Advancement of Expenses. The right to
                   --------------------------------
indemnification conferred in Section 2 hereof shall include the right to be paid
by the Company (within 2 business days of a request by Indemnitee) the Expenses
incurred or suffered by Indemnitee in connection with defending any Proceeding
for which such right to indemnification is applicable in advance of its final
disposition (an "Advancement of Expenses"); provided, however, that, if, but
                                            --------  -------
only if, the Delaware General Corporation Law ("DGCL") so requires, an
Advancement of Expenses for Indemnitee in his capacity as a director or officer
(and not in any other capacity in which service was or is rendered by
Indemnitee, including, without limitation, service to an employee benefit plan)
shall be made only upon delivery to the Company of an undertaking (an
"Undertaking"), by or on behalf of Indemnitee, to repay all amounts so advanced
if it shall ultimately be determined by final judicial decision from which there
is no further right to appeal (a "Final Adjudication") that Indemnitee is not
entitled to be indemnified for such Expenses under this Agreement or otherwise.

                4. Partial Indemnity, Etc. If Indemnitee is entitled under any
                   ----------------------
provision of this Agreement to indemnification by the Company for some or a
portion of any Expenses incurred or suffered by Indemnitee in connection with
any Proceeding but not, however, for all of the total amount thereof, the
Company shall nevertheless indemnify Indemnitee for the portion thereof to which
Indemnitee is entitled. Moreover, notwithstanding any other provision of this
Agreement, to the extent that Indemnitee has been successful on the merits or
otherwise in defense of any or all Proceedings relating in whole or in part to
an Indemnifiable Event or in defense of any issue or matter therein, including
dismissal without prejudice, Indemnitee shall be indemnified against all
Expenses incurred in connection therewith.

                5. Right of Indemnitee to Bring Suit.
                   ---------------------------------

                   (a)     If a claim under Section 2, 3 or 4 of this Agreement
is not paid in full by the Company within thirty days after a written claim has
been received by the Company,

                                        4

<PAGE>

except in the case of a claim for an Advancement of Expenses, in which case the
applicable period shall be two days after a written request has been received by
the Company, Indemnitee may at any time thereafter bring suit against the
Company to recover the unpaid amount of such claim.

                        (b)    The Company shall indemnify and hold harmless
Indemnitee from and against any and all Expenses and, if requested by
Indemnitee, shall (within two business days of any such request) advance funds
to Indemnitee to cover such Expenses, which are incurred by Indemnitee in
connection with any action brought by Indemnitee for (i) indemnification or
advance payment of Expenses by the Company under this Agreement or any other
agreement or Company By-law now or hereafter in effect relating to Indemnifiable
Events and/or (ii) recovery under any directors' and officers' liability
insurance policies maintained by the Company, regardless of whether Indemnitee
ultimately is determined to be entitled to such indemnification, advance expense
payment or insurance recovery, as the case may be.

                        (c)    In any suit brought by Indemnitee to enforce a
right to indemnification hereunder (but not in a suit brought by Indemnitee to
enforce a right to an Advancement of Expenses) it shall be a defense that, and
(ii) in any suit brought by the Company to recover an Advancement of Expenses
pursuant to the terms of an Undertaking the Company shall be entitled to recover
such Expenses upon a Final Adjudication that, Indemnitee has not met any
applicable standard for indemnification required to be met pursuant to the DGCL.
Neither the failure of the Company (including its directors, Independent Legal
Counsel, or its stockholders) to have made a determination prior to the
commencement of such suit that indemnification of Indemnitee is proper in the
circumstances because Indemnitee has met the applicable standard of conduct set
forth in the DGCL, nor an actual determination by the Company (including its
directors, Independent Legal Counsel, or its stockholders) that Indemnitee has
not met such applicable standard of conduct, shall create a presumption that
Indemnitee has not met the applicable standard of conduct or, in the case of
such a suit brought by Indemnitee, be a defense to such suit.

                        (d)    In any suit brought by Indemnitee to enforce a
right to indemnification or to an Advancement of Expenses hereunder, or by the
Company to recover an Advancement of Expenses pursuant to the terms of an
Undertaking, the burden of proving that Indemnitee is not entitled to be
indemnified, or to such Advancement of Expenses, under this Agreement or
otherwise, shall be on the Company.

                  6.    Settlement. The Company shall have no obligation to
                        ----------
indemnify Indemnitee under this Agreement for any amounts paid in settlement of
any Proceeding effected without the Company's prior written consent. The Company
shall not settle any Proceeding in any manner that would impose any fine or any
obligation on Indemnitee without Indemnitee's prior written consent and no
settlement of any Proceeding shall be entered into unless, if applicable, in
Indemnitee's discretion, such settlement includes, as an unconditional term
thereof, the delivery by the claimant or plaintiff in such Proceeding to
Indemnitee of a duly executed written release of Indemnitee from all liability
or obligation in respect of such Proceeding, which release shall be reasonably
satisfactory in form and substance to Indemnitee and Indemnitee's counsel. The
Company shall not unreasonably withhold its consent to any proposed settlement.

                                        5

<PAGE>

                  7.    Rights Not Exclusive. The rights provided under this
                        --------------------
Agreement shall not be deemed exclusive of any other rights which Indemnitee may
be entitled under the Company's By-laws, the Company's Certificate of
Incorporation, the DGCL, any Agreement, any vote of stockholders or of
disinterested directors or otherwise, both as to action in his official capacity
and as to action in any other capacity, and shall continue after Indemnitee
ceases to serve the Company as a director, officer, employee, consultant, agent
or fiduciary (or person named as a prospective director) of the Company. To the
extent that a change in the DGCL (whether by statute or judicial decision)
permits greater indemnification by agreement than would be afforded currently
under the Company's By-laws, the Company's Certificate of Incorporation and this
Agreement, it is the intent of the parties hereto that Indemnitee shall enjoy by
this Agreement the greater benefits so afforded by such change. Unless otherwise
required by law, the Company shall not adopt any amendment to its By-laws or
Certificate of Incorporation the effect of which would be to deny, diminish or
encumber the Indemnitee's rights to indemnification pursuant to this Agreement,
the Company's Certificate of Incorporation, the Company's By-laws, the DGCL or
any other applicable law as applied to any act or failure to act occurring in
whole or in part.

                  8.    Severability. The provisions of this Agreement shall be
                        ------------
severable in the event that any of the provisions hereof (including any
provision within a single section, paragraph or sentence) are held by a court of
competent jurisdiction to be invalid, void or otherwise unenforceable in any
respect, and the validity and enforceability of any such provision in every
other respect and of the remaining provisions hereof shall not be in any way
impaired and shall remain enforceable to the fullest extent permitted by law.

                  9.    Choice of Law. This Agreement shall be governed by and
                        -------------
construed and enforced in accordance with the laws of the State of Delaware,
without giving effect to any conflict of laws, provisions or principles.

                  10.   Change of Control. The Company agrees that if there is a
                        -----------------
Change of Control of the Company, then with respect to all matters thereafter
arising concerning the rights of Indemnitee to indemnity payments and
Advancement of Expenses under this Agreement or any other agreement or Company
By-law now or hereafter in effect relating to Indemnifiable Events, the Company
shall seek legal advice only from Independent Legal Counsel selected by
Indemnitee and approved by the Company (which approval shall not be unreasonably
withheld). Such counsel, among other things, shall render its written opinion to
the Company and Indemnitee as to whether and to what extent the Indemnitee would
be permitted to be indemnified under applicable law. The Company agrees to pay
the reasonable fees of the Independent Legal Counsel referred to above and to
indemnify fully such counsel against any and all expenses (including attorneys'
fees), claims, liabilities and damages arising out of or relating to this
Agreement or its engagement pursuant thereto.

                  11.   Establishment of Trust. In the event of a Potential
                        ----------------------
Change in Control, the Company may create a trust for the benefit of the
Indemnitee (either alone or together with one or more other indemnitees) and
from time to time fund such trust in such amounts as the Board may determine to
satisfy Expenses reasonably anticipated to be incurred in connection with
investigating, preparing for and defending any claim relating to an
Indemnifiable Event, and all judgments, fees, fines, penalties and settlement
amounts of all claims relating to an Indemnifiable Event from time to time paid
or claimed, reasonably anticipated or proposed to be

                                        6

<PAGE>

paid. The terms of any trust established pursuant hereto shall provide that upon
a Change in Control (i) the trust shall not be revoked or the principal thereof
invaded, without the written consent of the Indemnitee, (ii) the trustee shall
advance, within ten business days of a request by the Indemnitee, all Expenses
to the Indemnitee, (iii) the trustee shall promptly pay to the Indemnitee all
amounts for which the Indemnitee shall be entitled to indemnification pursuant
to this Agreement or otherwise, and (iv) all unexpended funds in such trust
shall revert to the Company upon a final determination by a court of competent
jurisdiction, as the case may be, that the Indemnitee has been fully indemnified
under the terms of this Agreement. The trustee shall be a person or entity
satisfactory to the Indemnitee. Nothing in this Section 11 shall relieve the
Company of any of its obligations under this Agreement.

                  12. Burden of Proof. In connection with any determination as
                      ---------------
to whether Indemnitee is entitled to be indemnified hereunder the burden of
proof shall be on the Company to establish that Indemnitee is not so entitled.

                  13. No Presumptions. For purposes of this Agreement, the
                      ---------------
termination of any Proceeding, by judgment, order, settlement (whether with or
without court approval) or conviction, or upon a plea of nolo contendere, or its
equivalent, shall not create a presumption that Indemnitee did not meet any
particular standard of conduct or have any particular belief or that a court has
determined that indemnification is not permitted by applicable law.

                  14. Liability Insurance. The Company is maintaining (pursuant
                      -------------------
to a policy or policies, true and complete copies of which have been made
available to Indemnitee), and shall maintain, an insurance policy or policies
providing directors' and officers' liability insurance. Indemnitee shall be
covered by such policy or policies, for proposing to become, serving as or
having served as a director, officer, employee, consultant, agent or fiduciary
(or person named as a prospective director) of the Company, or, at the request
of the Company, of another corporation or of a partnership, joint venture, trust
or other enterprise, to the maximum extent of the coverage available for any
person in such capacity. The Company shall maintain the Company's insurance
policy providing directors' and officers' liability insurance that is in place
as of the date hereof for a period from the date hereof until six years after
the last date on which Indemnitee ceases to be a director, officer, employee,
consultant, agent or fiduciary of the Company (or person named as a prospective
director) or, at the request of the Company, of another corporation,
partnership, joint venture, employee benefit plan, trust or other enterprise;
provided, however, that the Company may substitute therefor policies of
--------  -------
substantially similar coverage and amounts containing material terms no less
advantageous to the Indemnitee.

                  15. Subrogation. In the event of any payment under this
                      -----------
Agreement, the Company shall be subrogated to the extent of such payment to all
of the rights of recovery of Indemnitee, who shall execute all papers required
and take all action necessary to secure such rights, including execution of such
documents as are necessary to enable the Company to bring suit to enforce such
rights.

                  16. Period of Limitations. No legal action shall be brought
                      ---------------------
and no cause of action shall be asserted by or in the right of the Company
against Indemnitee, Indemnitee's spouse, heirs, executors or personal or legal
representatives after the expiration of two years from the date of accrual of
such cause of action, and any claim or cause of action of the Company

                                        7

<PAGE>

shall be extinguished and deemed released unless asserted by the timely filing
of a legal action within such two-year period; provided, however, that if any
shorter period of limitations is otherwise applicable to any such cause of
action such shorter period shall govern.

                  17.   Successor and Assignments; Effectiveness of Agreement.
                        -----------------------------------------------------
This Agreement shall be (i) binding upon all successors and assigns of the
Company (including any transferee of all or substantially all of its assets and
any successor by merger or otherwise by operation of law) and (ii) shall be
binding on and inure to the benefit of the heirs, personal representatives and
estate of Indemnitee. This Agreement shall continue in effect regardless of
whether Indemnitee becomes a director, officer, employee, consultant, agent or
fiduciary (or person named as a prospective director) of the Company, or
continues to serve as a director, officer, employee, consultant, agent or
fiduciary (or person named as a prospective director) of the Company or of any
other corporation, partnership, joint venture or other enterprise at the request
of the Company.

                  18.   Amendment. No amendment, modification, termination or
                        ---------
cancellation of this Agreement shall be effective unless made in a writing
signed by each of the parties hereto.

                  19.   Notices. All notices, requests, demands and other
                        -------
communications under this Agreement shall be in writing and shall be deemed to
have been duly given (a) if delivered by hand and receipted for by the party to
whom said notice or other communication shall have been directed, or (b) mailed
by certified or registered mail with postage prepaid, on the third business day
after the date on which it is so mailed:

                        (a)      If to Indemnitee:

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

or such other address as Indemnitee shall provide to the Company.

                        (b)      If to the Company to:

                                 Aderis Pharmaceuticals, Inc.
                                 85 Main Street
                                 Hopkinton, MA 01748
                                 Attention:  Chief Executive Officer

or such other address as may have been furnished to Indemnitee by the Company.

               [Remainder of this page intentionally left blank.]

                                        8

<PAGE>
                  IN WITNESS WHEREOF, the Company and Indemnitee have executed
this Agreement as of the day and year first above written.

                                                 ADERIS PHARMACEUTICALS, INC.,
                                                 a Delaware corporation

                                                 By:____________________________
                                                 Name:__________________________
                                                 Title:_________________________

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

                                       9

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