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                                                                   EXHIBIT 10.2

                         REGISTRATION RIGHTS AGREEMENT

         Registration Rights Agreement dated as of January 22, 1999 (this
"Agreement"), among ILEX ONCOLOGY, INC., a Delaware corporation (the
"Company"), and ELI LILLY AND COMPANY, an Indiana corporation, and its
permitted assigns ("Lilly").

                             PRELIMINARY STATEMENT

         The Company and certain holders of its securities (the "Holders", or
if singular, a "Holder") are parties to the Fourth Amended and Restated
Registration Rights Agreement dated December 11, 1996 (the "Prior Agreement"),
and the Registration Rights Agreement dated as of July 9, 1997 ("the "PRN
Agreement")). The Company and Lilly are parties to a Stock Purchase Agreement
dated effective January 22, 1999 (the "Stock Purchase Agreement"), pursuant to
which PRN shall be issued shares of Common (as defined herein). The Company
desires to grant certain registration rights to Lilly in connection with such
issuance of shares. Therefore, in consideration of the mutual representations
and agreements set forth in this Agreement, the Company and Lilly agree as
follows:

                                   AGREEMENT

SECTION 1. DEFINITIONS.

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

         "Affiliate" means any entity controlling, controlled by or under
common control with a designated Person. For the purposes of this definition,
"control" shall have the meaning specified as of the date of this Agreement for
that word in Rule 405 promulgated by the Commission under the Securities Act.

         "Board" means the Board of Directors of the Company.

         "Commission" means the Securities and Exchange Commission, and any
successor thereto.

         "Common" means the Company's Common Stock, $.01 par value per share.

         "Exchange Act" means the Securities Exchange Act of 1934, as amended.

         "Immediate Family" shall mean spouses, descendants (including adopted
children) and spouses of descendants.

         "Person" means an individual, partnership, corporation, business
trust, limited liability company, joint stock company, trust, unincorporated
association, joint venture, or other entity of whatever nature.

         "PRN Stock" means, for purposes of this definition, the Registrable
Stock (as defined in the "PRN Agreement") of PRN under the PRN Agreement.



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         "Registrable Stock" means any shares of Common acquired by Lilly
pursuant to the terms and provisions of the Stock Purchase Agreement and any
and all shares of Common or other securities issued with respect to such shares
by way of stock splits, stock combinations and similar events affecting the
Registrable Stock. As to any particular Registrable Stock, such securities will
cease to be Registrable Stock when they shall have been (x) effectively
registered under the Securities Act and sold by the holder thereof in
accordance with such registration, or (y) sold to the public pursuant to Rule
144 or Rule 701 of the Commission, or any successor rules.

         "Rule 144" means Rule 144 promulgated by the Commission under the
Securities Act, as such rule may be amended from time to time, or any successor
rule thereto.

         "Rule 701" means Rule 701 promulgated by the Commission under the
Securities Act, as such rule may be amended from time to time, or any successor
rule thereto.

         "Securities" means any debt or equity securities of the Company,
whether now or hereafter authorized, and any instrument convertible into, or
exercisable or exchangeable for, Securities or a Security.

         "Securities Act" means the Securities Act of 1933, as amended prior to
or after the date of this Agreement, or any federal statute or statutes which
shall be enacted to take the place of such Act, together with all rules and
regulations promulgated thereunder.

         SECTION 2. INCIDENTAL/PIGGYBACK REGISTRATION. Each time the Company
proposes to register any of its Securities under the Securities Act for its own
account or for the account of other Security holders or both, it will give at
least 30 days advance written notice of its intention to do so to Lilly. Lilly
may then specify, by written notice to the Company within 25 days of the date
of the Company's notice, the number of shares of Registrable Stock held by it
that it wishes to include in the Company's proposed registration (a "Piggyback
Registration"). Subject to the market cutback limitations of SECTION 7 of this
Agreement, the Company will use its best efforts to effect the Piggyback
Registration under the Securities Act of Registrable Stock specified by Lilly
under this SECTION 2.

         SECTION 3. LIMITATIONS ON REGISTRATION RIGHTS. Notwithstanding any
contrary provision of this Agreement, SECTION 2 of this Agreement shall not
apply to a registration effected solely to offer securities for sale pursuant
to, or in connection with, (i) an employee benefit plan or (ii) a transaction
subject to Rule 145 under the Securities Act or in an exchange offer registered
on Form S-4 or any successor form to Form S-4, or to any registration on a form
which does not permit inclusion of Registrable Stock pursuant to Commission
rule or practice.

         SECTION 4. REGISTRATION PROCEDURES.

                  4.1 Whenever the Company is required by this Agreement to
         include any Registrable Stock in a registration under the Securities
         Act, the Company will, as expeditiously as possible:

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                  (a) before filing each registration statement or prospectus
         or amendment or supplement thereto with the Commission, furnish
         counsel for Lilly with copies of all such documents proposed to be
         filed, which shall be subject to the reasonable approval of such
         counsel;

                  (b) prepare and file with the Commission a registration
         statement with respect to such Registrable Stock with respect to such
         securities including executing an undertaking to file post-effective
         amendments and use its best efforts to cause such registration
         statement to become and remain effective for the period of
         distribution contemplated thereby (subject to SECTION 4.2 below);

                  (c) prepare and file with the Commission such amendments and
         supplements to such registration statement and the prospectus used in
         connection therewith as may be necessary to keep such registration
         statement effective for the period of distribution contemplated
         thereby (subject to SECTION 4.2 below) and to comply with the
         provisions of the Securities Act with respect to the sale or other
         disposition of all Registrable Stock covered by such registration
         statement in accordance with the sellers' intended methods of
         disposition set forth in such registration statement for such period;

                  (d) promptly prepare and file with the Commission, and notify
         Lilly immediately after the filing of, such amendment or supplement to
         such registration statement or prospectus as may be necessary to
         correct any statements or omissions if, during such periods as a
         prospectus relating to such Securities is required to be delivered
         under the Securities Act, any event shall have occurred as the result
         of which any such prospectus or any other prospectus as then in effect
         would include an 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 in which they were made, not misleading,
         and notify Lilly and underwriter immediately after its discovery of
         such event;

                  (e) furnish to the underwriters and Lilly such numbers of
         copies of such registration statement, each amendment and supplement
         thereto (in each case, including all exhibits), the prospectus
         included in such registration statement (including each preliminary
         prospectus) and such other documents as such underwriters or Lilly may
         reasonably request in order to facilitate the disposition of the
         Registrable Stock in accordance with such registration statement;

                  (f) use its best efforts to register or qualify any
         Registrable Stock covered by such registration statement under the
         securities or blue sky laws of such jurisdictions within the United
         States of America as Lilly or the underwriters reasonably request, and
         to take any other acts which a seller or the underwriters may
         reasonably request under such securities or blue sky laws to enable
         the consummation of the disposition in such jurisdictions of such
         Registrable Stock (provided, however, that the Company shall not be
         required under this Agreement (i) to qualify generally to do business
         as a foreign corporation in any jurisdiction

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         in which it would not otherwise be required to qualify, or (ii) to
         consent to general service of process in any such jurisdiction unless
         the Company is already subject to service in such jurisdiction);

                  (g) provide a transfer agent and registrar for all
         Registrable Stock sold under the registration statement not later than
         the effective date of the registration statement;

                  (h) use its best efforts to cause all Registrable Stock sold
         under the registration statement to be listed on each securities
         exchange or to be qualified and eligible for trading in any automated
         quotation system, if any, on which similar Securities issued by the
         Company are then listed or traded or, if no such listing or
         qualification has then occurred, to use its best efforts to cause such
         Securities to be so listed or qualified on an exchange or in a trading
         system that is reasonably acceptable to the Company and the Holders of
         such Registrable Stock;

                  (i) enter into such customary agreements (including
         underwriting agreements in customary form) and take all such other
         actions as the underwriters, if any, or Lilly may reasonably request
         in order to expedite or facilitate the disposition of such Registrable
         Stock (including, without limitation, effecting a stock split or a
         combination of shares);

                  (j) advise Lilly, immediately after it shall receive notice
         or obtain knowledge thereof, of the issuance of any stop order by the
         Commission suspending the effectiveness of such registration statement
         or the initiation or threatening of any proceeding for such purpose
         and promptly use reasonable efforts to prevent the issuance of any
         stop order or to obtain its withdrawal if such stop order should be
         issued;

                  (k) make available for inspection by Lilly, any underwriter
         participating in any disposition pursuant to such registration
         statement, and any attorney, accountant or other agent retained by
         Lilly or underwriter, all financial and other records, pertinent
         corporate documents and properties of the Company, and cause the
         Company's officers, directors, employees and independent accountants
         to supply all information reasonably requested by any such seller or
         underwriter in connection with such registration statement, all
         subject to such limitations as the Company reasonably deems
         appropriate in order to protect the Company's confidential or
         proprietary information;

                  (l) comply with all applicable rules and regulations under
         the Securities Act and Exchange Act;

                  (m) if the offering is underwritten and at the request of
         Lilly, use its best efforts to furnish on the date that Registrable
         Stock are delivered to the underwriters for sale pursuant to such
         registration: (i) an opinion dated such date of counsel representing
         the Company for the purposes of such registration, addressed to the
         underwriters to such effects as reasonably may be requested by counsel
         for the underwriters and (ii) a letter dated such date from the
         independent public accountants retained by the Company, addressed to
         the underwriters stating that they are independent public accountants
         within the meaning of the

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         Securities Act and that, in the opinion of such accountants, the
         financial statements of the Company included in the registration
         statement or the prospectus, or any amendment or supplement thereof,
         comply as to form in all material respects with the applicable
         accounting requirements of the Securities Act, and such letter shall
         additionally cover such other financial matters (including information
         as to the period ending no more than five (5) business days prior to
         the date of such letter) with respect to such registration as such
         underwriters reasonably may request;

                  (n) make available for inspection by Lilly, any underwriter
         participating in any distribution pursuant to such registration
         statement, and any attorney, accountant or other agent retained by
         Lilly or underwriter, reasonable access to all financial and other
         records, pertinent corporate documents and properties of the Company,
         as such parties may reasonably request, and cause the Company's
         officers, directors and employees to supply all information reasonably
         requested by Lilly, underwriter, attorney, accountant or agent in
         connection with such registration statement;

                  (o) cooperate with Lilly and the managing underwriter, if
         any, to facilitate the timely preparation and delivery of certificates
         representing Registrable Stock to be sold, such certificates to be in
         such denominations and registered in such names as Lilly or the
         managing underwriter may request at least two (2) business days prior
         to any sale of Registrable Stock; and

                  (p) permit Lilly, if, in the sole and exclusive good faith
         judgment of the Company, Lilly might be deemed to be a controlling
         person of the Company, to participate in good faith in the preparation
         of such registration statement.

         4.2 For purposes of this Agreement, the period of distribution of
Registrable Stock in a firm commitment underwritten public offering shall be
deemed to extend until each underwriter has completed the distribution of all
securities purchased by it, and the period of distribution of Registrable Stock
in any other registration shall be deemed to extend until the earlier of the
sale of all Registrable Stock covered thereby or 180 days after the effective
date thereof, provided, however, in the case of any registration of Registrable
Stock on Form S-3 or a comparable or successor form which are intended to be
offered on a continuous or delayed basis, such 180-day period shall be
extended, if necessary, to keep the registration statement effective until all
such Registrable Stock are sold, provided that Rule 415, or any successor rule
under the Securities Act, permits an offering on a continuous or delayed basis,
and provided further that applicable rules under the Securities Act governing
the obligation to file a post-effective amendment, permit, in lieu of filing a
post-effective amendment which (y) includes any prospectus required by Section
10(a)(3) of the Securities Act or (z) reflects facts or events representing a
material or fundamental change in the information set forth in the registration
statement, the incorporation by reference of information required to be
included in (y) and (z) above contained in periodic reports filed pursuant to
Section 13 or 15(d) of the Exchange Act in the registration statement.

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         SECTION 5. EXPENSES. The Company will pay all Registration Expenses
(as defined below) in connection with each Piggyback Registration of
Registrable Stock permitted pursuant to SECTION 2 of this Agreement. For
purposes of this SECTION 5, "Registration Expenses" means all expenses incident
to the Company's performance of or compliance with SECTION 2 of this Agreement,
including, without limitation, all registration, filing and National
Association of Securities Dealers, Inc. fees, all fees and expenses of
complying with securities or blue sky laws, all word processing, duplicating
and printing expenses, messenger and delivery expenses, the reasonable fees and
disbursements of counsel for the Company and of its independent public
accountants, including the expenses of any special audits or "cold comfort"
letters required by or incident to such performance and compliance, the
reasonable fees and disbursements of one law firm retained by the holders of
Registrable Stock being registered, premiums and other costs of policies of
insurance obtained by the Company against liabilities arising out of the public
offering of the Registrable Stock being registered but excluding all agency
fees and commissions, underwriting discounts and commissions and transfer
taxes, if any.

         SECTION 6. INDEMNIFICATION.

         6.1 In the event of any registration of any of its Registrable Stock
under the Securities Act pursuant to this Agreement, the Company agrees, to the
fullest extent permitted by law, to indemnify and hold harmless Lilly, and each
officer, partner, director and Affiliate of such seller, against any losses,
claims, damages or liabilities, joint or several, arising out of or based upon:

                  (a) any untrue statement or alleged untrue statement of any
         material fact contained, on the effective date thereof, in any
         registration statement under which such Securities were registered
         under the Securities Act, any preliminary prospectus or final
         prospectus contained in any registration statement, or any other
         materials deemed to be a prospectus pursuant to the Securities Act, or
         any Securities being registered, or any amendment or supplement
         thereto, or any blue sky application or other document executed by the
         Company specifically for that purpose or based upon written
         information furnished by the Company filed in any state or other
         jurisdiction in order to qualify any or all of the Registrable Stock
         under the securities laws thereof (any such application, document or
         information herein called a "Blue Sky Application"), or

                  (b) any omission or any alleged omission to state in any such
         document a material fact required to be stated therein or necessary to
         make the statements therein not misleading, or

                  (c) any violation by the Company or its agents (other than by
         the indemnitee claiming indemnification hereunder) of the Securities
         Act or any rule or regulation promulgated under the Securities Act
         applicable to the Company or its agents (other than by the indemnitee
         claiming indemnification hereunder) and relating to action or inaction
         required of the Company in connection with such registration,

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         except insofar as any such loss, claim, damage or liability is:

                           (i) caused by or contained in any information
                  furnished in writing to the Company by Lilly expressly for
                  use in connection with such registration; or

                           (ii) caused by Lilly's failure to deliver a copy of
                  the registration statement or prospectus or any amendment or
                  supplement thereto as required by the Securities Act or the
                  rules or regulations thereunder to be delivered by such
                  seller, if such delivery would have cured the defect giving
                  rise to such loss, claim, damage or liability; or

                           (iii) caused by the delivery by Lilly of a
                  prospectus or preliminary prospectus or any amendment or
                  supplement thereto after receipt of notice from the Company
                  that it should no longer be used.

         In connection with an underwritten offering, the Company will
         indemnify such underwriters, their officers and directors and each
         Person who controls (within the meaning of the Securities Act) such
         underwriters to the same extent as provided above with respect to
         Lilly. The Company shall reimburse each Person indemnified pursuant to
         this SECTION 6.1 for any reasonable legal or other expenses incurred
         in connection with investigating or defending any loss, claim, damage,
         liability or action indemnified against. The reimbursements required
         by this SECTION 6.1 shall be made by periodic payments during the
         course of the investigation or defense, as and when bills are received
         or expenses incurred. The indemnities provided pursuant to this
         SECTION 6.1 shall remain in force and effect regardless of any
         investigation made by or on behalf of the indemnified party and shall
         survive any transfer of Registrable Stock by Lilly.

         6.2 In the event of any registration of any Registrable Stock under
the Securities Act pursuant to this Agreement, Lilly agrees to furnish to the
Company in writing such information and affidavits as the Company reasonably
requests for use in connection with any registration statement, prospectus and
any amendment or supplement thereto in connection with the registration.

         6.3 To the fullest extent permitted by law, and subject to the
limitation set forth in the last sentence of this SECTION 6.3, Lilly agrees to
indemnify and hold harmless the Company, its directors and officers, and each
Affiliate of the Company, against:

                  (a) any losses, claims, damages or liabilities, joint or
         several, arising out of or based upon:

                           (i) any alleged untrue statement of any material
                  fact contained on the effective date thereof, in any
                  registration statement under which such Securities were
                  registered under the Securities Act, any preliminary
                  prospectus or final prospectus contained therein, or any
                  summary prospectus contained therein, or any amendment or
                  supplement thereto, or

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                           (ii) any alleged omission to state in any such
                  document a material fact required to be stated therein or
                  necessary to make the statements therein not misleading,

         but only insofar as any such loss, claim, damage or liability is
         caused by any information furnished in writing to the Company by Lilly
         expressly for use in connection with such registration, and excluding
         any such loss, claim, damage or liability which is caused by such
         statements, or caused by such omissions, based upon the authority of
         an expert as defined in the Securities Act (but only if Lilly had no
         grounds to believe, and did not believe, that the statements made on
         the authority of an expert were untrue or that there was an omission
         to state a material fact); and

                  (b) any losses, claims, damages or liabilities, joint or
         several, arising out of or based upon any failure by Lilly to deliver
         a copy of the registration statement or prospectus or any amendment or
         supplement thereto if required by the Securities Act or the rules or
         regulations thereunder to be delivered by Lilly, if such delivery
         would have cured the defect giving rise to such loss, claim, damage or
         liability. In connection with an underwritten offering, Lilly will
         indemnify such underwriters, their officers and directors and each
         Person who controls (within the meaning of the Securities Act) such
         underwriters to the same extent as provided above with respect to the
         Company and other sellers. Lilly shall reimburse each Person
         indemnified pursuant to this SECTION 6.3 in connection with
         investigating or defending any loss, claim, damage, liability or
         action indemnified against. The reimbursements required by this
         SECTION 6.3 shall be made by periodic payments during the course of
         the investigation or defense, as and when bills are received or
         expenses incurred. The indemnities provided pursuant to this SECTION
         6.3 shall remain in force and effect regardless of any investigation
         made by or on behalf of the indemnified party and shall survive any
         transfer of Registrable Stock by Lilly. Notwithstanding any contrary
         provision of this Agreement, however, the liability under this SECTION
         6 of Lilly shall be limited in the aggregate, with respect to the
         claims of all indemnified Persons taken as a whole, to the amount of
         proceeds received by Lilly from the sale of the Registrable Stock sold
         by Lilly pursuant to such registration statement.

         6.4 Each party entitled to indemnification under this SECTION 6 (the
"Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified
Party has actual knowledge of any claim as to which indemnity may be sought,
and shall permit the Indemnifying Party to assume the defense of any such claim
or any litigation resulting therefrom; provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or any
litigation resulting therefrom, shall be approved by the Indemnified Party
(whose approval shall not unreasonably be withheld, denied or delayed) and the
Indemnified Party may participate in such defense at such party's expense other
than reasonable costs of investigation and of liaison with counsel so selected
(unless the Indemnified Party shall have reasonably concluded that there may be
reasonable defenses available to it which are different from or additional to
those available to the Indemnifying Party or that the interests of the
Indemnified Party reasonably may be deemed to conflict with the interests of
the Indemnifying Party, in which case the Indemnified Party shall have the
right to select one separate counsel and to assume such legal defenses and
otherwise

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to participate in the defense of such action, with the reasonable expenses and
fees of such separate counsel and other reasonable expenses related to such
participation to be reimbursed by the Indemnifying Party as incurred), and
provided further that the failure of any Indemnified Party to give notice as
provided herein shall not relieve the Indemnifying Party of its obligations
under this SECTION 6 unless and to the extent the Indemnifying Party is
materially prejudiced thereby. No Indemnifying Party, in the defense of any
such claim or litigation, shall, except with the consent of each Indemnified
Party, consent to entry of any judgment or enter into any settlement which does
not include as an unconditional term thereof the giving by the claimant or
plaintiff to such Indemnified Party of a release from all liability in respect
to such claim or litigation. Each Indemnified Party shall furnish such
information regarding itself or the claim in question as an Indemnifying Party
may reasonably request in writing and as shall be reasonably required in
connection with the defense of such claim and litigation resulting therefrom.

         6.5 If the indemnification provided for in this SECTION 6 is held by a
court of competent jurisdiction (by the entry of a final judgment or decree by
such court and the expiration of time to appeal or the denial of the last right
of appeal) to be unavailable to an Indemnified Party with respect to any loss,
liability, claim, damage or expense referred to herein, then the Indemnifying
Party, in lieu of indemnifying such Indemnified Party hereunder, shall
contribute to the amount paid or payable by such Indemnified Party as a result
of such loss, liability, claim, damage or expense in such proportion as is
appropriate to reflect the relative fault of the Indemnifying Party on the one
hand and of the Indemnified Party on the other in connection with the
statements or omissions which resulted in such loss, liability, claim, damage
or expense, as well as any other relevant equitable considerations. The
relative fault of the Indemnifying Party and of the Indemnified Party shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission to state a material fact
relates to information supplied by the Indemnifying Party or by the Indemnified
Party and the parties' relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission. Notwithstanding
any contrary provision of this Agreement, however, the liability under this
SECTION 6.5 of each Holder and Lilly which is a seller of Registrable Stock
shall be limited in the aggregate, with respect to the claims of all
indemnified Persons taken as a whole, to the amount of proceeds received by the
indemnifying seller from the sale of the Registrable Stock sold by the
indemnifying seller pursuant to such registration statement.

         6.6 Notwithstanding the foregoing, to the extent that the provisions
on indemnification and contribution contained in the underwriting agreement
entered into in connection with any underwritten public offering contemplated
by this Agreement are in conflict with the foregoing provisions, the provisions
in such underwriting agreement shall be controlling, except that under no
circumstances should Lilly's indemnification obligations pursuant to any such
underwriting agreement exceed its obligations under SECTIONS 6.3 AND 6.5 of
this Agreement.

         6.7 The foregoing indemnity agreement of the Company and Lilly is
subject to the condition that, insofar as they relate to any loss, claim,
liability or damage made in a preliminary prospectus but eliminated or remedied
in the amended prospectus on file with the Commission at the time the
registration statement in question becomes effective or the amended prospectus
filed with the Commission pursuant to Commission Rule 424(b) (the "Final
Prospectus"), such indemnity agreement shall not inure to the benefit of any
underwriter if a copy of the Final Prospectus was

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furnished to the underwriter and was not sent or furnished to the person if
required by law so to have been delivered asserting the loss, liability, claim
or damage at or prior to the time such action is required by the Securities
Act, and if the Final Prospectus would have cured the defect giving rise to
such loss, liability, claim or damage.

         6.8 The indemnities and obligations provided in this SECTION 6 shall
survive the transfer of any Registrable Stock by Lilly.

         SECTION 7. MARKETING RESTRICTIONS.

         7.1      If:

                  (a) Lilly requests registration of Common under SECTION 2 of
         this Agreement, and

                  (b) the offering proposed to be made is to be an underwritten
         public offering, and

                  (c) the managing underwriters of such public offering furnish
         a written opinion that the total amount of Securities to be included
         in such offering would exceed the maximum number of shares of Common
         (as specified in such opinion) which can be marketed at a price
         reasonably related to the current market value of such Common and
         without otherwise materially and adversely affecting such offering
         (the "Underwriter Maximum"),

then the rights of (i) Lilly, (ii) the Holders, (iii) the holders of other
Securities having the right to include such Securities in such registration and
(iv) of the Company to participate in such offering shall be in the following
order of priority:

                           (i) FIRST, (1) if such registration was not
                  initiated by the Company as a primary registration, then the
                  Person or Persons requesting such registration pursuant to a
                  Demand Registration of such Person or Persons shall be
                  entitled to participate in accordance with the relative
                  priorities, if any, that shall exist among them, subject to
                  the limitation that a number of shares of Investor
                  Registrable Stock (as such term is defined in the Prior
                  Agreement) equal to 35% of the Underwriter Maximum shall also
                  be entitled to participate therein, with such shares of
                  Investor Registrable Stock being allocated pro rata among the
                  Holders of Investor Registrable Stock owned by such Holders,
                  and (2) if the Company has initiated such registration as a
                  primary registration, then the Company shall be entitled to
                  participate up to the full number of shares of stock which
                  the Company deems necessary or advisable to fulfill its
                  strategic capital requirements;

                           (ii) SECOND, the number of shares of Investor
                  Registrable Stock requested to be included therein, up to the
                  remainder of such Underwriter Maximum (after taking into
                  account the number of shares to be sold pursuant to clause
                  (i) above) allocated pro rata among the Holders of such
                  Investor Registrable Stock on the basis of the number of
                  shares of Investor Registrable Stock owned by such Holders,
                  with further successive pro rata allocations among the
                  Holders of Investor Registrable

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                  Stock if any such Holder of Investor Registrable Stock has
                  requested the registration of fewer than all of such shares
                  of Investor Registrable Stock it is entitled to register;

                           (iii) THIRD, the number of shares of CTRC
                  Registrable Stock ( as such term is defined in the Prior
                  Agreement) requested to be included therein, up to such
                  Underwriter Maximum (after taking into account the number of
                  shares to be sold pursuant to clauses (i) and (ii) above)
                  allocated pro rata among the Holders of such CTRC Registrable
                  Stock on the basis of the number of shares of CTRC
                  Registrable Stock owned by such Holders, with further
                  successive pro rata allocations among the Holders of CTRC
                  Registrable Stock if any such Holder of CTRC Registrable
                  Stock has requested the registration of fewer than all of
                  such shares of CTRC Registrable Stock it is entitled to
                  register.

                           (iv) FOURTH, the number of shares of Management
                  Registrable Stock (as defined in the Prior Agreement) and
                  Vector Registrable Stock (as such term is defined in the
                  Prior Agreement) requested to be included therein, up to such
                  Underwriter Maximum (after taking into account the number of
                  shares of securities to be sold pursuant to clauses (i), (ii)
                  and (iii) above) allocated pro rata among the Holders of such
                  Management Registrable Stock and Vector Registrable Stock on
                  the basis of the number of shares of Management Registrable
                  Stock and Vector Registrable Stock owned by such Holders,
                  with further successive pro rata allocations among the
                  Holders of Management Registrable Stock and Vector
                  Registrable Stock if any such Holder has requested the
                  registration of fewer than all of such shares of Management
                  Registrable Stock or Vector Registrable Stock he is entitled
                  to register;

                           (v) FIFTH, the number of shares of PRN Stock
                  requested to be included therein, up to the Underwriter
                  Maximum (after taking into account the number of shares of
                  securities to be sold pursuant to clauses (i), (ii), (iii)
                  and (iv) above) allocated pro rata among the PRN of such PRN
                  Stock on the basis of the number of shares of PRN Stock owned
                  by such Holders shall be entitled to participate, with
                  further successive pro rata allocations among the Holders of
                  PRN Stock if any such Holder has requested the registration
                  of fewer than all of such shares of PRN Stock it is entitled
                  to register;

                           (vi) SIXTH, the number of shares of Registrable
                  Stock requested to be included therein, up to the Underwriter
                  Maximum (after taking into account the number of shares of
                  securities to be sold pursuant to clauses (i), (ii), (iii),
                  (iv) and (v) above allocated pro rata among the holders of
                  such Registrable Stock on the basis of the number of shares
                  of Registrable Stock owned by such holders shall be entitled
                  to participate, with further successive pro rata allocations
                  among the holders of Registrable Stock if any such holder has
                  requested the registration of fewer than all of such shares
                  of Registrable Stock it is entitled to register; and

                                      -11-

<PAGE>   12


                           (vii) SEVENTH, other securities requested to be
                  included in such registration up to the Underwriter Maximum
                  (after taking into account the securities to be sold pursuant
                  to clauses (i), (ii), (iii), (iv), (v) and (vi) above).

         7.2 In connection with any offering involving an underwriting of
Registrable Stock pursuant to SECTION 2 of this Agreement, the Company shall
not be required to include any of the Registrable Stock of a holder in such
offering unless such holder agrees to the terms of the underwriting agreed to
between the Company and the underwriter or underwriters selected by the
Company.

         SECTION 8. LOCKUP AGREEMENT. Lilly agrees in connection with the
registration of any Registrable Stock in a public offering that, upon the
request of the Company or the underwriters managing such underwritten offering
of the Company's Securities, it will not sell, make any short sale of, loan,
grant any option for the purchase of, or otherwise dispose of any Securities of
the Company (other than the securities included in the registration and other
than a transfer by Lilly to an Affiliate of Lilly) without the prior written
consent of the Company or such underwriters, as the case may be, for such
period of time (not to exceed 120 days) from the effective date of such
registration as the Company or the underwriters may specify, subject to the
Company obtaining similar agreements from the Company's executive officers and
directors, any holders of five (5) percent or more of the Company's then issued
and outstanding Common, and any other holders of Securities participating in
such registration.

         SECTION 9. COMPLIANCE WITH RULE 144. With a view to making available
the benefits of certain rules and regulations of the Commission which may
permit the sale of restricted securities to the public without registration,
the Company agrees to:

                  (a) make and keep public information available as those terms
         are understood and defined in Rule 144, at all times from and after
         ninety (90) days following the effective date of the first
         registration under the Securities Act filed by the Company for an
         offering of its Securities to the general public and for so long as
         the Company is subject to the reporting requirements of Section 13 or
         15(d) of the Exchange Act;

                  (b) use its best efforts to file with the Commission in a
         timely manner all reports and other documents required of the Company
         under the Securities Act and the Exchange Act at any time after it has
         become subject to such reporting requirements; and

                  (c) so long as Lilly owns any Securities, and is not eligible
         to sell all such Securities under paragraph (k) of Rule 144, furnish
         to Lilly upon request, a written statement by the Company as to its
         compliance with the reporting requirements of Rule 144 (at any time
         from and after ninety (90) days following the effective date of the
         first registration statement filed by the Company for an offering of
         its securities to the general public), and of the Securities Act and
         the Exchange Act (at any time after it has become subject to such
         reporting requirements), a copy of the most recent annual or quarterly
         report of the Company, and such other reports and documents so filed
         as Lilly may reasonably request in availing itself of any

                                      -12-

<PAGE>   13


         rule or regulation of the Commission allowing Lilly to sell any such
         securities without registration.

         SECTION 10. ASSIGNABILITY OF REGISTRATION RIGHTS. The rights set forth
in this Agreement shall accrue to each subsequent holder of Registrable Stock
who (i) shall have executed a written consent agreeing to be bound by the terms
and conditions of this Agreement, and (ii) owns greater than 12,500 shares of
Registrable Stock (subject to appropriate adjustment for stock splits, stock
combinations and similar events affecting the Registrable Stock).

         SECTION 11. DESIGNATION OF UNDERWRITER. The Company shall select the
managing underwriter(s) and all other investment banking advisers to the
Company for all other registrations that may be effected from time to time by
the Company.

         SECTION 12. PARTICIPATION IN UNDERWRITTEN REGISTRATIONS.

                  (a) No Person may participate in any registration hereunder
         which is underwritten unless such Person (i) agrees to sell such
         Person's securities on the basis provided in any underwriting
         arrangements approved by the Person or Persons entitled hereunder to
         approve such arrangements (including, without limitation, pursuant to
         the terms of any over allotment or "green shoe" option requested by
         the managing underwriter(s)), (ii) furnishes to the Company such
         information regarding such Person, the Registrable Stock of such
         Person to be registered and the intended method of disposition of such
         Registrable Stock, and (iii) completes and executes all
         questionnaires, powers of attorney, indemnities, underwriting
         agreements and other documents reasonably required under the terms of
         such underwriting arrangements.

                  (b) If Lilly disapproves of the terms of the underwriting,
         Lilly may elect to withdraw therefrom by written notice to the Company
         and the managing underwriter; provided that if Lilly withdraws, (i) if
         such withdrawal occurs prior to the registration statement being filed
         with the Commission, Lilly shall not be responsible for the
         Registration Expenses in connection with such registration, and (ii)
         if such withdrawal occurs subsequent to the filing of the registration
         statement with the Commission, then Lilly shall be responsible for
         that portion of the Registration Expenses directly resulting from such
         withdrawal; provided, however, that if at the time of such withdrawal,
         Lilly has learned of a material adverse change in the conditions,
         business or prospects of the Company from that known to them at the
         time of their request, then Lilly shall not be required to pay any of
         such expenses.

                  (c) Each Person that is participating in any registration
         hereunder agrees that, upon receipt of any notice from the Company of
         the happening of any event of the kind described in SECTION 4.1(D)
         above, such Person will forthwith discontinue the disposition of its
         Registrable Stock pursuant to the registration statement until such
         Person's receipt of the copies of a supplemented or amended prospectus
         as contemplated by such SECTION 4.1(d).

                                      -13-

<PAGE>   14


         SECTION 13. MISCELLANEOUS.

         13.1 Modifications; Amendment. Neither this Agreement nor any
provision hereof may be changed, waived, discharged or terminated unless
effected by a writing executed and delivered by the Company and Lilly.

         13.2 Severability. In the event that any court or any governmental
authority or agency declares all or any part of any Section of this Agreement
to be unlawful or invalid, such unlawfulness or invalidity shall not serve to
invalidate any other Section of this Agreement, and in the event that only a
portion of any Section is so declared to be unlawful or invalid, such
unlawfulness or invalidity shall not serve to invalidate the balance of such
Section.

         13.3 Successors and Assigns. Subject to SECTION 10, this Agreement is
binding upon and inures to the benefit of the Company, its successors and
assigns, and Lilly, its successors and assigns, and legal representatives.

         13.4 Notices. All communications in connection with this Agreement
shall be in writing and shall be deemed properly given if hand delivered or
sent by telecopier or overnight courier with adequate evidence of delivery or
sent by registered or certified mail, return receipt requested, and, if to
Lilly, at Lilly's address as shown on the books of the Company or its transfer
agent, and if to the Company, at its offices at:

                              ILEX ONCOLOGY, INC.
                              11550 I.H. 10 West, Suite 100
                              San Antonio, TX 78230
                              Attention: President

Any notice called for hereunder shall be deemed given when received.

         13.5 Governing Law. This Agreement shall be governed by and construed
in accordance with the laws of the State of New York without application of the
choice of laws provisions of such laws.

         13.6 Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original but all of which shall
together constitute one and the same instrument. A written consent executed
pursuant to SECTION 10 of this Agreement shall be deemed to be part of, and
constitute a counterpart of, this Agreement.

         13.7 Headings. The headings used herein are solely for the convenience
of the parties and shall not serve to modify or interpret the text of the
Sections at the beginning of which they appear.

         13.8 Entire Agreement. This Agreement embodies the entire agreement
and understanding among the Company and Lilly and supersedes all prior oral and
written agreements and understandings relating to the subject matter hereof.

                                      -14-

<PAGE>   15


         13.9 Waiver. Any waiver or consent under this Agreement shall be
effective only in the specific instance and for the purpose for which it was
given, and shall not constitute a continuing waiver or consent except as
specifically set forth in such waiver or consent. The election of any remedy by
a party hereto shall not constitute a waiver of the right of such party to
pursue other available remedies. No notice to or demand on a party not
expressly required under this Agreement shall entitle the party receiving such
notice or demand to any other or further notice or demand in similar or other
circumstances or constitute a waiver of the rights of the party giving such
notice or demand to any other or further action in any circumstances without
such notice or demand.

         13.10 Specific Performance. The Company recognizes that the rights of
the Lilly under this Agreement are unique and, accordingly, Lilly shall, in
addition to such other remedies as may be available to them at law or in
equity, have the right to enforce their rights hereunder by actions for
injunctive relief and specific performance to the extent permitted by law.

         13.11 Grant of Registration Rights. The Company shall not hereafter
grant to any third party any registration rights more favorable than, or in any
way conflicting with, any of those contained herein, so long as any of the
registration rights under this Agreement remain in effect, provided, in any
event, (i) any grant of demand or required registration rights shall provide
that Lilly has incidental or "piggyback" registration rights with respect
thereto in accordance with the provisions of SECTION 2 hereof, (ii) such rights
shall not become effective prior to the rights of Lilly hereunder, and (iii)
the recipients of such rights shall be subject to provisions comparable to
those set forth in SECTION 8 hereof.



                         [signatures on following page]


                                      -15-

<PAGE>   16


         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be executed on the day first above written.


The Company:
------------
                                       ILEX ONCOLOGY, INC.

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



Lilly:
-----
                                       ELI LILLY AND COMPANY

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

                                     -16-