<PAGE>   1

         THE SECURITIES REPRESENTED HEREBY 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 WHICH, IN THE OPINION OF COUNSEL FOR THIS CORPORATION, IS AVAILABLE.

         VOID AFTER 5:00 P.M. NEW YORK TIME, ON MAY 4, 2005. WARRANT TO PURCHASE
283,887 SHARES OF COMMON STOCK.

PA-40                                                              May 5, 2000

                   WARRANT TO PURCHASE SHARES OF COMMON STOCK
                     OF INKINE PHARMACEUTICAL COMPANY, INC.

         This certifies that Leerink, Swann, Garrity, Sollami, Yaffe & Wynn,
Inc., 60 State St., 15th Floor, Boston, MA 02109, or any subsequent holder of
this Warrant (the "HOLDER"), for value received, is entitled, subject to the
adjustment and to the other terms set forth below, to purchase from InKine
Pharmaceutical Company, Inc., a New York corporation (the "COMPANY"), 283,887
fully paid and nonassessable shares of the Company's common stock, par value
$0.0001 per share (the "COMMON STOCK") at a price of $5.13 per share (the
"EXERCISE PRICE"). This Warrant shall be exercisable at any time on or after the
date first noted above, (the "COMMENCEMENT DATE") but not later than 5:00 p.m.
(New York Time) on the Expiration Date (as defined below). The Exercise Price
and, in some cases, the number of shares purchasable hereunder are subject to
adjustment as provided in Section 3 of this Warrant. This Warrant and all rights
hereunder, to the extent not exercised in the manner set forth herein shall
terminate and become null and void on the Expiration Date. "EXPIRATION DATE"
means 5:00 p.m. (New York time) on May 4, 2005. In the event that the Holder
does not exercise this Warrant pursuant to the terms of this Warrant, then this
Warrant shall expire, be cancelled, and be null and void. Pursuant to the letter
agreement, dated February 28, 2000, between the Company and the Holder, the
Holder has agreed to act as placement agent in connection with a certain private
placement of the Company's securities which closed on the date hereof (the
"OFFERING").

This Warrant is subject to the following terms and conditions:

1.       Exercise; Issuance of Certificates; Payment for Shares; Conversion
         Right.

         1.1 Duration of Exercise of Warrant. This Warrant is exercisable at the
option of the Holder at any time or from time to time but not earlier than on
the Commencement Date or later than 5:00 p.m. (New York Time) on the Expiration
Date for all or a portion of the shares of Common Stock which may be purchased
hereunder (the "WARRANT SHARES"). This Warrant may be exercised by presentation
and surrender hereof to the Company at its principal office, or at the office of
its stock transfer agent, with the Subscription Agreement attached hereto duly
<PAGE>   2
completed and executed and, unless the Conversion Right in Section 1.2 is
exercised, upon payment of the Exercise Price for the number of Warrant Shares
for which this Warrant is being exercised determined in accordance with the
provisions hereof. The Company agrees that the Warrant Shares shall be and are
deemed to be issued to the Holder as the record owner of such shares as of the
close of business on the date on which this Warrant shall have been surrendered
and payment made for such shares. Subject to the provisions of Section 2,
certificates for the shares of Common Stock so purchased, together with any
other securities or property to which the Holder is entitled upon such exercise,
shall be delivered to the Holder by the Company or its transfer agent at the
Company's expense within a reasonable time after the rights represented by this
Warrant have been exercised, but not later than ten (10) days from the date of
such exercise. Each stock certificate so delivered shall be in such
denominations of Common Stock as may be requested by the Holder and shall be
registered in the name of the Holder or such other name as shall be designated
by the Holder. If, upon exercise of this Warrant, fewer than all of the Warrant
Shares evidenced by this Warrant are purchased prior to the Expiration Date of
this Warrant, one or more new warrants substantially in the form of, and on the
terms in, this Warrant will be issued for the remaining number of shares of
Common Stock not purchased upon exercise of this Warrant. Upon receipt by the
Company of this Warrant at its office, or by the stock transfer agent of the
Company at its office, in proper form for exercise, the Holder shall be deemed
to be the holder of record of the shares of Common Stock issuable upon such
exercise, notwithstanding that the stock transfer books of the Company shall
then be closed or that certificates representing such shares of Common Stock
shall not then be physically delivered to the Holder.

         1.2 Conversion Right. At any time during the term of this Warrant, the
Holder may, at its option, convert this Warrant, in whole or in part (a
"CONVERSION RIGHT"), into the number of shares of Common Stock determined in
accordance with this Section 1.2, by surrendering this Warrant at the principal
office of the Company or at the office of its stock transfer agent, accompanied
by a notice, in the form attached, stating such Holder's intent to effect such
Conversion Right, the number of Warrant Shares to be exchanged and the date on
which the Holder requests that such Conversion Right occur (the "NOTICE OF
CONVERSION"). The Conversion Right shall take place on the date specified in the
Notice of Conversion or, if later, the date the Notice of Conversion is received
by the Company (the "CONVERSION DATE"). Certificates for the shares issuable
upon such Conversion Right and, if applicable, a new warrant of like tenor
evidencing the balance of the shares remaining subject to this Warrant, shall be
issued as of the Conversion Date and delivered to the Holder within seven (7)
days following the Conversion Date. In connection with any Conversion Right,
this Warrant shall represent the right to subscribe for and acquire the number
of Warrant Shares equal to (i) the number of Warrant Shares specified by the
Holder in its Notice of Conversion (the "CONVERSION AMOUNT") less (ii) the
number of Warrant Shares equal to the quotient obtained by dividing (a) the
product of the Conversion Amount and the then current Exercise Price by (b) the
then current Market Price (as defined in Section 3.2 hereafter) of a share of
Common Stock.


                                       2
<PAGE>   3
2.       Shares to Be Fully Paid; Reservation of Shares.

         The Company covenants and agrees that all Warrant Shares shall, upon
issuance and payment therefor, if any, be duly authorized, validly issued, fully
paid and nonassessable and free from all preemptive rights of any stockholder
and free of all taxes, liens and charges with respect to the issue thereof. The
Company covenants that it will reserve and keep available a sufficient number of
shares of its authorized but unissued Common Stock for such exercise. The
Company will take all such reasonable action as may be necessary to assure that
such Warrant Shares may be issued as provided herein without violation of any
applicable law or regulation, or of any requirements of the Nasdaq SmallCap
Market or any other domestic securities exchange or automated quotation system
upon which the Common Stock may be listed.

3.       Adjustment of Exercise Price and Number of Shares.

         The Exercise Price and, in some cases, the number of shares purchasable
upon the exercise of this Warrant shall be subject to adjustment from time to
time upon the occurrence of certain events described in this Section 3.

         3.1 Split or Combination of Common Stock and Stock Dividend. In case
the Company shall at any time subdivide, redivide, recapitalize, split or change
its outstanding shares of Common Stock into a greater number of shares or
declare a dividend upon its Common Stock payable solely in shares of Common
Stock, the Exercise Price in effect immediately prior to such subdivision or
declaration shall be proportionately reduced, and the number of Warrant Shares
issuable upon exercise of this Warrant shall be proportionately increased.
Conversely, in case the outstanding shares of Common Stock of the Company shall
be combined into a smaller number of shares, the Exercise Price in effect
immediately prior to such combination shall be proportionately increased, and
the number of Warrant Shares issuable upon exercise of this Warrant shall be
proportionately reduced.

         3.2 Definitions. For purposes of this Agreement, the following
definitions shall apply:

                  (a) "Market Price" shall mean: (i) if there is a ready public
         market of registered stock, the Market Price shall be the "Stock Price"
         (as defined in this Section 3.2) obtained by taking the average over a
         period of five (5) consecutive trading days ending on the second
         trading day prior to the date of determination; and (ii) if there is no
         ready public market, Market Price shall be the higher of the last bona
         fide sale made by the Company and the fair market value of the Common
         Stock as determined by the Board of Directors in its good faith
         judgment.

                  (b) "Stock Price" shall mean (i) the last sales price, on each
         such trading day, of a share of Common Stock, or if no such sale takes
         place on any such trading day, the mean of the highest bid and lowest
         asked prices therefor on any such trading day, in each case as
         officially reported on all national securities

                                       3
<PAGE>   4
             exchanges on which the Common Stock is then listed or admitted to
             trading or as reported by the National Association of Securities
             Dealers Automated Quotation System ("NASDAQ"), or (ii) if the
             Common Stock is not then listed or admitted to trading on any
             national securities exchange or in the over-the-counter market, as
             reported by NASDAQ, the closing price of the Common Stock on such
             date, or (iii) if the Common Stock is not then quoted by NASDAQ,
             the mean between the highest and lowest bid prices reported by
             market makers and dealers for the Common Stock listed as such by
             the National Quotation Bureau, Incorporated, or any similar
             successor organization, or (iv) if there is no ready public market,
             then the Stock Price shall be the Market Price, as determined
             pursuant to 3.2(a)(ii) above.

         3.3 Notice of Adjustment. Promptly after adjustment of the Exercise
Price or any increase or decrease in the number of shares purchasable upon the
exercise of this Warrant, the Company shall give written notice thereof, by
first class mail, postage prepaid, addressed to the registered Holder of this
Warrant at the address of such Holder as shown on the books of the Company. The
notice shall be signed by the Company's Chairman or President and shall state
the effective date of the adjustment and the Exercise Price resulting from such
adjustment and the increase or decrease, if any, in the number of shares
purchasable at such price upon the exercise of this Warrant, setting forth in
reasonable detail the method of calculation and the facts upon which such
calculation is based.

         3.4 Notices. If at any time:

                  (a) the Company shall declare any cash dividend upon its
         Common Stock;

                  (b) the Company shall declare any dividend upon its Common
         Stock payable in securities (other than a dividend payable solely in
         shares of Common Stock) or make any special dividend or other
         distribution to the holders of its Common Stock;

                  (c) there shall be any consolidation or merger of the Company
         with another corporation, or a sale of all or substantially all of the
         Company's assets to another corporation; or

                  (d) there shall be a voluntary or involuntary dissolution,
         liquidation or winding-up of the Company;

then, in any one or more of said cases, the Company shall give, by certified or
registered mail, return receipt requested, postage prepaid, addressed to the
registered Holder of this Warrant at the address of such Holder as shown on the
books of the Company, (i) at least thirty (30) days' prior written notice of the
date on which the books of the Company shall close or a record shall be taken
for such dividend, distribution or subscription rights or for determining rights
to vote in respect of any such dissolution, liquidation or winding-up; (ii) at
least ten (10) days' prior written

                                       4
<PAGE>   5
notice of the date on which the books of the Company shall close or a record
shall be taken for determining rights to vote in respect of any such
reorganization, reclassification, consolidation, merger or sale, and (iii) in
the case of any such reorganization, reclassification, consolidation, merger,
sale, dissolution, liquidation or winding-up, at least thirty (30) days' written
notice of the date when the same shall take place. Any notice given in
accordance with clause (i) above shall also specify, in the case of any such
dividend, distribution or option rights, the date on which the holders of Common
Stock shall be entitled thereto. Any notice given in accordance with clause
(iii) above shall also specify the date on which the holders of Common Stock
shall be entitled to exchange their Common Stock for securities or other
property deliverable upon such reorganization, reclassification, consolidation,
merger, sale, dissolution, liquidation or winding- up, as the case may be. If
the registered Holder of this Warrant does not exercise this Warrant prior to
the occurrence of an event described above, except as provided in Sections 3.1
and 3.5, the Holder shall not be entitled to receive the benefits accruing to
existing holders of the Common Stock in such event. Notwithstanding anything
herein to the contrary, if and to the extent the Holder chooses to exercise this
Warrant within the ten (10) day period following receipt of the notice specified
in clause (ii) above, the Holder may elect to pay the aggregate Exercise Price
by delivering to the Company cash or a cashier's check in the amount of the
aggregate par value of the shares of Common Stock to be purchased and the
Holder's full recourse promissory note in the amount of the balance of the
aggregate Exercise Price, which promissory note shall be payable to the order of
the Company in a single sum on the 30th day following the date of receipt of
such notice and shall bear interest at the lowest applicable federal short term
rate (using monthly compounding) as established pursuant to Section 1274(d) of
the Internal Revenue Code of 1986, as amended, or any successor provision;
provided, however, that if the Holder elects to deliver such a promissory note
to the Company, the Holder will pledge to the Company all Common Stock issued in
connection with the exercise of this Warrant, and the Company shall retain
possession of the certificates evidencing such Common Stock, until such time as
the Note is paid in full.

         3.5 Changes in Common Stock. In case at any time following the
Commencement Date hereof, the Company shall be a party to any transaction
(including, without limitation, a merger, consolidation, sale of all or
substantially all of the Company's assets or recapitalization of the Common
Stock) in which the previously outstanding Common Stock shall be changed into or
exchanged for different securities of the Company or common stock or other
securities of another corporation or interests in a noncorporate entity or other
property (including cash) or any combination of any of the foregoing (each such
transaction being herein called the "TRANSACTION" and the date of consummation
of the Transaction being herein called the "CONSUMMATION DATE"), then, as a
condition of the consummation of the Transaction, lawful and adequate provisions
shall be made so that the Holder, upon the exercise hereof at any time on or
after the Consummation Date, shall be entitled to receive, and this Warrant
shall thereafter represent the right to receive, in lieu of the Common Stock
issuable upon such exercise prior to the Consummation Date, the highest amount
of securities or other property to which such Holder would actually have been
entitled as a stockholder upon the consummation of the Transaction if such
Holder had exercised such Warrant immediately prior thereto. The provisions of
this Section 3.5 shall similarly apply to successive Transactions.


                                       5
<PAGE>   6
4.       Issue Tax.

         The issuance of certificates for shares of Common Stock upon the
exercise of this Warrant shall be made without charge to the Holder of this
Warrant for any issue tax in respect thereof; provided, however, that the
Company shall not be required to pay any tax 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 Holder of this Warrant.

5.       No Voting or Dividend Rights; Limitation of Liability.

         Nothing contained in this Warrant shall be construed as conferring upon
the Holder hereof the right to vote or to consent or to receive notice as a
stockholder in respect of meetings of stockholders for the election of directors
of the Company or any other matters or any rights whatsoever as a stockholder of
the Company. Except for the adjustment to the Exercise Price pursuant to Section
3.1 in the event of a dividend on the Common Stock payable in shares of Common
Stock, no dividends or interest shall be payable or accrued in respect of this
Warrant or the interest represented hereby or the shares purchasable hereunder
until, and only to the extent that, this Warrant shall have been exercised. No
provisions hereof, in the absence of affirmative action by the Holder to
purchase shares of Common Stock, and no mere enumeration herein of the rights or
privileges of the Holder hereof, shall give rise to any liability of such Holder
for the Exercise Price or as a stockholder of the Company whether such liability
is asserted by the Company or by its creditors.

6.       Restrictions on Transferability of Securities; Compliance With
         Securities Act.

         6.1 Restrictions on Transferability. This Warrant and the Warrant
Shares shall not be transferable in the absence of registration under the
Securities Act of 1933, as amended (the "SECURITIES ACT") or an applicable
exemption from registration thereunder.

         6.2 Restrictive Legend. Each certificate representing the Warrant
Shares or any other securities issued in respect of the Warrant Shares upon any
stock split, stock dividend, recapitalization, merger, consolidation or similar
event, shall be stamped or otherwise imprinted with a legend substantially in
the following form (in addition to any legend required under applicable state
securities laws):

         "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 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 WHICH, IN THE OPINION OF COUNSEL FOR
THE HOLDER, WHICH COUNSEL AND OPINION ARE REASONABLY SATISFACTORY TO COUNSEL FOR
THIS CORPORATION, IS AVAILABLE."


                                       6
<PAGE>   7
7.       Registration Rights.

         7.1 As used in this Warrant, the following terms shall have the
following meanings:

                           (a) "Affiliate" shall mean, with respect to any
                  Person (as defined below), any other Person controlling,
                  controlled by, or under direct or indirect common control
                  with, such Person (for the purposes of this definition
                  "control," when used with respect to any specified Person,
                  shall mean the power to direct the management and policies of
                  such person, directly or indirectly, whether through ownership
                  of voting securities, by contract or otherwise; and the terms
                  "controlling" and "controlled" shall have meanings correlative
                  to the foregoing).

                           (b) "Business Day" shall mean a day, Monday through
                  Friday, on which banks are generally open for business in each
                  of New York, New York; Boston, Massachusetts; and
                  Philadelphia, Pennsylvania;

                           (c) "Person" shall mean any person, individual,
                  corporation, limited liability company, partnership, trust or
                  other nongovernmental entity or any governmental agency,
                  court, authority or other body (whether foreign, federal,
                  state, local or otherwise).

                           (d) The terms "register," "registered" and
                  "registration" refer to the registration effected by preparing
                  and filing with the SEC a registration statement in compliance
                  with the Act, and the declaration or ordering by the SEC of
                  the effectiveness of such registration statement.

                           (e) "Registrable Securities" shall mean the shares of
                  Common Stock issuable upon the exercise of this Warrant;
                  provided, however, that securities shall only be treated as
                  Registrable Securities if and only for so long as they (A)
                  have not been disposed of pursuant to a registration statement
                  declared effective by the SEC, (B) have not been sold in a
                  transaction exempt from the registration and prospectus
                  delivery requirements of the Act so that all transfer
                  restrictions and restrictive legends with respect thereto are
                  removed upon the consummation of such sale, and (C) are held
                  by the Holder.

                           (f) "Registration Expenses" shall mean all expenses
                  incurred by the Company in complying with this Section 7
                  including, without limitation, all registration, qualification
                  and filing fees, printing expenses, escrow fees, fees and
                  expenses of counsel for the Company, blue sky fees and
                  expenses and the expense of any special audits incident to, or
                  required by, any such registration (but excluding the fees of
                  legal counsel for the Holder).

                           (g) "Registration Statement" shall have the meaning
                  ascribed to such term in Section 7.2 (a).


                                       7
<PAGE>   8
                           (h) "Registration Period" shall have the meaning
                  ascribed to such term in Section 7.4(a).

                           (i) "Selling Expenses" shall mean all underwriting
                  discounts and selling commissions applicable to the sale of
                  Registrable Securities and the aggregate fees and expenses of
                  legal counsel for the Holder.

         7.2 The Company shall, as soon as practicable, but not later than ten
(10) business days after the date hereof (such tenth business day herein
referred to as the "Filing Date"), (i) use its best efforts to file with the SEC
a registration statement (the "Registration Statement") with respect to the
resale of the Registerable Securities and use its best efforts to have such
Registration Statement declared effective by the SEC as soon thereafter as is
practical and (ii) cause such Registration Statement to remain effective until
the earlier of such date as the Holder has completed the distribution described
in the Registration Statement and such time as such Shares are no longer, by
reason of Rule 144 (k) under the Act, required to be registered for the sale
thereof by the Holder. If requested by the Holder, and in accordance with
applicable securities laws, the Registration Statement shall cover the direct
sale of such Registrable Securities to the Holder of such securities.

         7.3 All Registration Expenses incurred in connection with any
registration, qualification, exemption or compliance pursuant to Section 7.2
shall be borne by the Company. All Selling Expenses relating to the sale of
securities registered by or on behalf of the Holder shall be borne by the
Holder.

         7.4 In the case of the registration, qualification, exemption or
compliance effected by the Company pursuant to this Agreement, the Company
shall, upon reasonable request, inform the Holder as to the status of such
registration, qualification, exemption and compliance. At its expense the
Company shall:

                           (a) use its best efforts to keep such registration,
                  and any qualification, exemption or compliance under state
                  securities laws which the Holder reasonably requests the
                  Company to obtain, continuously effective until the Holder has
                  completed the distribution described in the registration
                  statement relating thereto. The period of time during which
                  the Company is required hereunder to keep the Registration
                  Statement effective is referred to herein as "the Registration
                  Period."

                           (b) advise the Holder:

                                    (i) when the Registration Statement or any
                           amendment thereto has been filed with the SEC and
                           when the Registration Statement or any post-effective
                           amendment thereto has become effective;


                                       8
<PAGE>   9
                                    (ii) of any request by the SEC for
                           amendments or supplements to the Registration
                           Statement or the prospectus included therein or for
                           additional information;

                                    (iii) of the issuance by the SEC of any stop
                           order suspending the effectiveness of the
                           Registration Statement or the initiation of any
                           proceedings for such purpose;

                                    (iv) of the receipt by the Company of any
                           notification with respect to the suspension of the
                           qualification of the Registrable Securities included
                           therein for sale in any jurisdiction or the
                           initiation or threatening of any proceeding for such
                           purpose; and

                                    (v) of the happening of any event that
                           requires the making of any changes in the
                           Registration Statement or the prospectus so that, as
                           of such date, the statements therein are not
                           misleading and do not omit to state a material fact
                           required to be stated therein or necessary to make
                           the statements therein (in the case of the
                           prospectus, in the light of the circumstances under
                           which they were made) not misleading;

                           (c) make every reasonable effort to obtain the
                  withdrawal of any order suspending the effectiveness of any
                  Registration Statement at the earliest possible time;

                           (d) furnish to the Holder, without charge, at least
                  one copy of such Registration Statement and any post-effective
                  amendment or supplement thereto, including financial
                  statements and schedules, and, if the Holder so requests in
                  writing, all exhibits (excluding those incorporated by
                  reference) in the form filed with the SEC;

                           (e) during the Registration Period, deliver to the
                  Holder, without charge, a reasonable number of copies of the
                  prospectus included in such Registration Statement and any
                  amendment or supplement thereto as the Holder may reasonably
                  request; and the Company consents to the use, consistent with
                  the provisions hereof, of the prospectus and any amendment or
                  supplement thereto by the Holder of Registrable Securities in
                  connection with the offering and sale of the Registrable
                  Securities covered by the prospectus and any amendment or
                  supplement thereto;

                           (f) cooperate with the Holder to facilitate the
                  timely preparation and delivery of certificates representing
                  Registrable Securities to be sold pursuant to any Registration
                  Statement free of any restrictive legends to the extent not
                  required at such time and in such denominations and registered
                  in such names as the Holder may request at least five (5)
                  business days prior to sales of Registrable Securities
                  pursuant to such Registration Statement;


                                       9
<PAGE>   10
                           (g) upon the occurrence of any event contemplated by
                  Section 7.4(b)(v) above, the Company shall promptly prepare a
                  post-effective amendment to the Registration Statement or a
                  supplement to the related prospectus, or file any other
                  required document so that, as thereafter delivered to
                  purchasers of the Registrable Securities included therein, the
                  prospectus will not include any untrue statement of a material
                  fact or omit to state any material fact necessary to make the
                  statements therein, in the light of the circumstances under
                  which they were made, not misleading.

         7.5 The Holder shall have no right to take any action to restrain,
enjoin or otherwise delay any registration pursuant to Section 7.2 hereof as a
result of any controversy that may arise with respect to the interpretation or
implementation of this Agreement.


         7.6              (a) Upon receipt of any notice from the Company
                  of the happening of any event requiring the preparation of a
                  supplement or amendment to a prospectus relating to
                  Registrable Securities so that, as thereafter delivered to THE
                  Holder, such prospectus will not contain an 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 not misleading, each Holder shall forthwith
                  discontinue disposition of Registrable Securities pursuant to
                  the registration statement contemplated by Section 7.2 until
                  its receipt of copies of the supplemented or amended
                  prospectus from the Company and, if so directed by the
                  Company, each Holder shall deliver to the Company all copies,
                  other than permanent file copies then in such Holder's
                  possession, of the prospectus covering such Registrable
                  Securities current at the time of receipt of such notice.

                           (b) As a condition to the inclusion of its
                  Registrable Securities, the Holder shall furnish to the
                  Company such information regarding the Holder, the securities
                  of the Company owned beneficially or of record by the Holder
                  and the distribution proposed by the Holder as the Company may
                  request in writing or as shall be required in connection with
                  any registration, qualification or compliance referred to in
                  this Section 7.

                           (c) With respect to any sale of Registrable
                  Securities pursuant to a Registration Statement filed pursuant
                  to this Section 7, the Holder hereby covenants with the
                  Company (i) not to make any sale of the Registrable Securities
                  without effectively causing the prospectus delivery
                  requirements under the Act to be satisfied, and (ii) if such
                  Registrable Securities are to be sold by any method or in any
                  transaction other than on a national securities exchange, the
                  Nasdaq National Market, the Nasdaq SmallCap Market or in the
                  over-the-counter market, in privately negotiated transactions,
                  or in a combination of such methods, or as otherwise described
                  in the prospectus contemplated by Section 7.2, to notify the


                                       10
<PAGE>   11
                  Company at least five (5) business days prior to the date on
                  which the Holder first offers to sell any such Registrable
                  Securities.

                           (d) The Holder acknowledges and agrees that the
                  Registrable Securities sold pursuant to the Registration
                  Statement described in this Section are not transferable on
                  the books of the Company unless the stock certificate
                  submitted to the transfer agent evidencing such Registrable
                  Securities is accompanied by a certificate reasonably
                  satisfactory to the Company to the effect that (i) the
                  Registrable Securities have been sold in accordance with such
                  Registration Statement and (ii) the requirement of delivering
                  a current prospectus has been satisfied.

                           (e) The Holder shall not take any action with respect
                  to any distribution deemed to be made pursuant to such
                  registration statement, which would constitute a violation of
                  Regulation M under the Exchange Act or any other applicable
                  rule, regulation or law.

                           (f) At the end of the period during which the Company
                  is obligated to keep the Registration Statement current and
                  effective as described above, the Holder of Registrable
                  Securities included in the Registration Statement and the
                  shares underlying the Warrants shall discontinue sales of
                  shares pursuant to such Registration Statement upon receipt of
                  notice from the Company of its intention to remove from
                  registration the shares covered by such Registration Statement
                  which remain unsold, and such Holder shall notify the Company
                  of the number of shares registered which remain unsold
                  immediately upon receipt of such notice from the Company.

         7.7 With the written consent of the Company and the Holder, any
provision of this Section 7 may be waived (either generally or in a particular
instance, either retroactively or prospectively and either for a specified
period of time or indefinitely) or amended.

8.       Modification and Waiver.

         This Warrant and any provision hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of the same is sought.

9.       Notices.

         Except as otherwise provided herein, any notice, request or other
document required or permitted to be given or delivered to the Holder hereof or
the Company shall be delivered personally or by nationally recognized overnight
courier service or sent by registered or certified mail, return receipt
requested, to such Holder at its address as shown on the books of the Company or
to the Company at its principal office. Notices delivered personally shall be
effective upon receipt, notices sent by overnight courier service shall be
deemed to have been

                                       11
<PAGE>   12
received one (1) day after deposit with such courier and notices sent by United
States mail shall be deemed to have been received three (3) days after deposit
with the U.S. Postal Service.

10.      Descriptive Headings and Governing Law.

         The descriptive headings of the several sections and paragraphs of this
Warrant are inserted for convenience only and do not constitute a part of this
Warrant. This Warrant shall be construed and enforced in accordance with, and
the rights of the parties shall be governed by, the laws of the State of New
York without giving effect to conflict of laws. The parties hereby submit to the
exclusive jurisdiction of the courts of the State of New York located in New
York County and the federal courts located in the Southern District of New York,
with respect to any action or legal proceeding commenced by either party with
respect to this Agreement. Each party irrevocably waives any objection it now
has or hereafter may have respecting the venue of any such action or proceeding
or the inconvenience of such forum, and each party consents to the service of
process in any such action or proceeding in the manner set forth for the
delivery of notices herein.

11.      Lost Warrants or Stock Certificate.

         The Company represents and warrants to the Holder that upon receipt of
evidence reasonably satisfactory to the Company of the loss, theft, destruction
or mutilation of any Warrant or stock certificate and, in the case of any such
loss, theft or destruction, and if requested, upon receipt of an indemnity bond
reasonably satisfactory to the Company, or in the case of any such mutilation,
upon surrender and cancellation of such Warrant or stock certificate, the
Company at its expense will make and deliver a new Warrant or stock certificate,
of like tenor, in lieu of the lost, stolen, destroyed or mutilated Warrant or
stock certificate.

12.      Fractional Shares.

         No fractional shares shall be issued upon exercise of this Warrant. The
Company shall, in lieu of issuing any fractional share pay the Holder entitled
to such fraction a sum in cash equal to the fair market value of any such
fractional interest as it shall appear on the public market, or if there is no
public market for such shares, then as shall be reasonably determined by the
Company.


                                       12
<PAGE>   13
         IN WITNESS WHEREOF, the Company has caused this Warrant to be executed
by its officer, thereunto duly authorized as of this 5th day of May, 2000.


                                     INKINE PHARMACEUTICAL COMPANY, INC.




                                     By:      /s/Robert F. Apple
                                         --------------------------------------
                                              Robert F. Apple
                                              Senior Vice President and
                                              Chief Financial Officer
<PAGE>   14
                                SUBSCRIPTION FORM

                     To Be Executed by the Registered Holder
                          in Order to Exercise Warrants

[DATE]

InKine Pharmaceutical Company, Inc.
Sentry Park East
1720 Walton Road
Blue Bell, Pennsylvania  19422

Attention:

                  The undersigned, the holder of the within Warrant, hereby
irrevocably elects to exercise the purchase right represented by such Warrant
for, and to purchase thereunder, ____________ shares of Common Stock, par value
$.0001 per share (the "Common Stock") of InKine Pharmaceutical Company, Inc.
and, subject to the following paragraph, herewith makes payment of
_________________ Dollars ($__________) therefor and requests that the
certificates for such shares be issued in the name of, and delivered to
_______________________________________, whose address is
_______________________________________, ______________________________________
and if such number of shares of Common Stock shall not represent all of the
shares of Common Stock which may be exercised pursuant to the Warrant, a new
Warrant for the balance of such shares of Common Stock shall be registered in
the name of, and delivered to, the Registered Holder at the address set forth
below.

         If the exercise of this Warrant is not covered by a registration
statement effective under the Securities Act of 1933, as amended (the
"Securities Act"), the undersigned represents that it is acquiring such Common
Stock for investment for its own account, not as nominee or agent, and not with
a view to the distribution thereof and the undersigned has not signed or
otherwise arranged for the selling, granting any participation in, or otherwise
distributing the same.

                            Leerink, Swann, Garrity, Sollami, Yaffe & Wynn, Inc.

DATED:_______________       By:_______________________________________
                                        Authorized Signature

                            Name:_____________________________________
                            Title:______________________________________
<PAGE>   15
                         CONVERSION RIGHT EXERCISE FORM

                     To Be Executed by the Registered Holder
                    in Order to Exercise the Conversion Right


         The undersigned hereby irrevocably elects to surrender its Warrant for
such shares of Common Stock pursuant to the Conversion Right of the within
Warrant, as provided for in Section 1.2 of such Warrant.

         Please issue a certificate or certificates for such Common Stock in the
name of


            PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER

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

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

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

                    ----------------------------------------
                     [please print or type name and address]

and deliver to

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

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

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

                    ----------------------------------------
                     [please print or type name and address]

and if such number of Warrants shall not be all the Warrants evidenced by the
attached Warrant a new Warrant for the balance of such Warrants shall be
registered in the name of, and delivered to, the Registered Holder at the
address stated below.

Dated:
       ----------------------------     X
                                          ------------------------------------

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

                                          ------------------------------------
                                          Address


                                          ------------------------------------
                                          Taxpayer Identification Number
<PAGE>   16
                                   ASSIGNMENT

                     To Be Executed by the Registered Holder
                           in Order to Assign Warrants


FOR VALUE RECEIVED,                        hereby sells, assigns and transfers
unto

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

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

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

                    ----------------------------------------
                     [please print or type name and address]

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

            PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER

                        of the Warrants represented by the attached Warrant, and
hereby irrevocably constitutes and appoints                 attorney to transfer
the attached Warrant and the Warrants represented thereby on the books of the
Company, with full power of substitution in the premises.

Dated:                     Leerink, Swann, Garrity, Sollami, Yaffe & Wynn, Inc.


                           By:
                              -------------------------------------------------
                                        Authorized Signature

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