Document:

<PAGE>   1
                                                                   EXHIBIT 10.28

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR HYPOTHECATED IN THE
ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT TO THE SECURITIES
UNDER SUCH ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY THAT SUCH
REGISTRATION IS NOT REQUIRED OR UNLESS SOLD PURSUANT TO AN EXEMPTION TO SUCH
ACT.

                    LEASING TECHNOLOGIES INTERNATIONAL, INC.

                           WARRANT TO PURCHASE 13,750
                       SHARES OF SERIES A PREFERRED STOCK

                            Void after March 31, 2006

         THIS CERTIFIES THAT, for value received, Leasing Technologies
International, Inc. (the "Holder") is entitled to purchase, on the terms and
subject to the conditions hereof, up to 13,750 shares of Series A Preferred
Stock, par value $0.001 per share (the "Series A Preferred Stock"), of Array
BioPharma Inc., a Delaware corporation (the "Company"), at a per share purchase
price of $3.00 (the "Exercise Price"), subject to adjustment as provided herein.

         The following terms shall apply to this Warrant:

         1. Exercise of Warrant. The terms and conditions upon which this
Warrant may be exercised, and the Series A Preferred Stock covered hereby (the
"Warrant Shares"), may be purchased, are as follows:

                  1.1 Number of Shares. This Warrant is being delivered to
Holder as additional consideration for Holder's extension of a credit facility
to the Company, pursuant to that certain Loan and Security Agreement dated of
even date herewith. The number of Warrant Shares for which this Warrant is
initially exercisable is 13,750 shares, which number is subject to adjustment
pursuant to Section 2 of this Warrant.

                  1.2 Exercise. This Warrant may be exercised in whole or in
part at any time or from time to time up until 5:00 p.m. Mountain Standard Time,
March 31, 2006, and shall be void thereafter; provided that the Company shall
give Holder written notice of Holder's right to exercise this Warrant not more
than 90 days and not less than 30 days before such date. If the notice is not so
given, the expiration date shall automatically be extended until 30 days after
the date the Company delivers the notice to Holder. The exercise of the purchase
rights hereunder, in whole or in part shall be effected by (a) the surrender of
this Warrant, together with a duly executed copy of the form of the subscription
attached as EXHIBIT A hereto, to the Company at its principal offices, and (b)
the delivery of the Exercise Price by (i) check or bank draft payable to the
Company's order,

                                        1
<PAGE>   2

or (ii) by wire transfer to the Company's account for the number of Warrant
Shares for which the purchase rights hereunder are being exercised.

                  1.3      Automatic Exercise.

                           (a) Notwithstanding the provisions of Section 1.1
above, this Warrant shall automatically be deemed to be exercised in full in the
manner set forth in Section 1.4 hereof, without any further action on behalf of
the Holder on the earliest of a date: (a) ten (10) days prior to a "Sale of the
Company" (as defined), or (b) immediately prior to the closing of an
underwritten initial public offering by the Company in which the Series A
Preferred Stock converts automatically into Common Stock (an "IPO"). A "Sale of
the Company" shall mean either of the following (i) the acquisition of all or
substantially all of the capital stock of the Company by another entity by means
of any transaction or series of related transactions (including, without
limitation, any reorganization, merger or consolidation but, excluding any
merger effected exclusively for the purpose of changing the domicile of the
Company); or (ii) a sale of all or substantially all of the assets of the
Company; unless the Company's shareholders of record as constituted immediately
prior to such acquisition or sale will, immediately after such acquisition ro
sale (by virtue of securities issued as consideration for the corporation's
acquisition or sale or otherwise) hold at least 50% of the voting power of the
surviving or acquiring entity. In connection with the exercise of this Warrant
pursuant to clause (a) and clause (b) of this Section 1.3, such exercise shall
be conditioned upon the closing of such Sale of the Company or IPO and the
Warrant shall not be deemed to have been exercised until the closing of such
Sale of the Company or IPO.

                           (b) Public Offering. For purposes of this Warrant,
IPO means the sale of the Company's Common Stock pursuant to a registration
statement under the Securities Act of 1933, as amended, for an underwritten
public offering (other than a registration on Form S-8, Form S-4 or comparable
forms), which results in aggregate cash proceeds (prior to underwriters'
commissions and expenses) to the Company of more than $7,500,000. Immediately
prior to the closing of any Public Offering prior to the Expiration Date, any
portion of this Warrant then not exercised or exercisable will be exercisable
for the number of shares of the Company's Common Stock that would have resulted
from the conversion, pursuant to the Company's Articles of Incorporation then in
effect of the maximum number of shares of Preferred Stock that could have been
acquired by the Holder upon the exercise of the unexpired portion of this
Warrant immediately prior to such Public Offering.

                  1.4 Net Issue Election.

                           (a) Upon automatic exercise of this Warrant as
provided in Section 1.3 above or at any time or from time to time as the Holder
may elect, the Holder shall be entitled to receive, without the payment by the
Holder of any additional consideration, shares of Series A Preferred Stock equal
to the value of this Warrant or any portion hereof by the surrender of this
Warrant or such portion to the Company, with the net issue election notice
attached hereto as EXHIBIT B duly executed, at the principal office of the
Company. Thereupon, the Company shall issue to the Holder such number of fully
paid and nonassessable shares of Series A Preferred Stock as is computed using
the following formula:

                                        2
<PAGE>   3

                                                     X=Y (A-B)
                                                      --------
                                                         A

                  where:            X=       the number of shares of Series A
                                             Preferred Stock to be issued to the
                                             Holder.

                                    Y=       the number of shares of Series A
                                             Preferred Stock covered by this
                                             Warrant in respect of which the net
                                             issue election is made.

                                    A=       the fair market value of one share
                                             of Series A Preferred Stock, as
                                             determined pursuant to subsection
                                             (b) below, as at the time the net
                                             issue election is made.

                                    B=       the Exercise Price in effect under
                                             this Warrant at the time the net
                                             issue election is made.

                           (b) Determination of Fair Market Value. For purposes
of this Section, fair market value of one share of Series A Preferred Stock as
of a particular date (the "Determination Date") shall mean:

                                    (i) In the case of an initial public
offering of the Common Stock, the initial "Price to Public" of one share of
Common Stock specified in the final prospectus with respect to such offering,
multiplied by the number of shares of Common Stock into which each share of
Series A Preferred Stock converts as of that date;

                                    (ii) In the case of a Sale of the Company,
the effective per share consideration to be received in a Sale of the Company by
holders of the Series A Preferred Stock, or if no such price is set forth in the
agreement concerning the Sale of the Company, then as determined in good faith
by the Company's Board of Directors;

                                    (iii) If the Company's Common Stock is
listed on a security exchange or the Nasdaq National Market, the closing price
of the Company's Common Stock on such exchange or the Nasdaq National Market on
the day notice of exercise is provided to the Company under Section 1.4(b)
hereof, multiplied by the number of shares of Common Stock into which each share
of Series A Preferred Stock converts as of that date; or

                                    (iv) If Sections 1.4(b)(i), (ii), or (iii)
do not apply, then as determined by the Board of Directors in good faith, which
determination shall be conclusive and binding on the holder hereof.

                  1.5 Issuance of Shares. Upon the exercise of the purchase
rights, in whole or in part, evidenced by this Warrant, a certificate or
certificates for the purchased Warrant Shares shall be issued by the Company to
the Holder as soon as practicable. Upon the partial exercise of this Warrant,
the Company shall, as soon as practicable, deliver to the Holder a warrant in
like tenor as this Warrant to purchase the number of shares in respect of which
this Warrant shall not have been exercised.

                                       3
<PAGE>   4

         2. Certain Adjustments.

                  2.1 Series A Preferred Stock Dividends. If the Company at any
time prior to the expiration of this Warrant shall pay a dividend with respect
to the Company's Series A Preferred Stock payable in shares of Series A
Preferred Stock, or make any distribution with respect to the Company's Series A
Preferred Stock, then the purchase price per share shall be appropriately
decreased, and the number of Warrant Shares shall be appropriately increased in
proportion to such dividend.

                  2.2 Splits and Subdivisions. In the event the Company should
at any time or from time to time fix a record date for a split or subdivision of
the outstanding shares of Series A Preferred Stock of the Company, or the
determination of the holders of Series A Preferred Stock of the Company entitled
to receive a dividend or other distribution payable in additional shares of
Series A Preferred Stock of the Company or other securities or rights
convertible into, or entitling the holder thereof to receive directly or
indirectly, additional shares of the Company's Series A Preferred Stock
(hereinafter referred to as the "Series A Preferred Stock Equivalents") without
payment of any consideration by such holder for the additional shares of Series
A Preferred Stock or Series A Preferred Stock Equivalents (including the
additional shares of Series A Preferred Stock issuable upon conversion or
exercise thereof), then, and as of such record date (or the date of such
distribution, split or subdivision if no record date is fixed), the per share
purchase price shall be appropriately decreased, and the number of Warrant
Shares shall be appropriately increased in proportion to such increase of
outstanding shares.

                  2.3 Combination of Shares. If the number of shares of Series A
Preferred Stock outstanding at any time after the date hereof is decreased by a
combination of the outstanding shares of Series A Preferred Stock of the
Company, the per share purchase price shall be appropriately increased and the
number of Warrant Shares shall be appropriately decreased in proportion to such
decrease in outstanding shares.

                  2.4 Adjustments for Other Distributions. In the event the
Company shall declare a distribution with respect to the Series A Preferred
Stock payable in securities of other persons, evidences of indebtedness issued
by the Company or other persons, assets, or options, or rights not referred to
above, then, in each such case for the purpose of this Section 2, upon exercise
of this Warrant the holder hereof shall be entitled to a proportionate share of
any such distribution as though such holder was the holder of the number of
shares of Series A Preferred Stock of the Company into which this Warrant may be
exercised as of the record date fixed for the determination of the holders of
Series A Preferred Stock of the Company entitled to receive such distribution.

                  2.5 Sale or Issuance Below Purchase Price. If the Company
shall at any time or from time to time issue or sell any of its Preferred Stock,
or any other securities convertible into Preferred Stock, for a consideration
per share of at least $1.00 per share, but less than the Exercise Price in
effect immediately prior to the time of such issue or sale, the Exercise Price
then in effect and then applicable for any subsequent period or periods shall be
adjusted to a price determined by dividing (i) an amount equal to the sum of (x)
the number of shares of Common Stock outstanding immediately prior to such issue
or sale multiplied by the Exercise Price then in effect and (y) the

                                       4
<PAGE>   5

consideration, if any, received by the Company upon such issue or sale, by (ii)
the total number of shares of Common Stock outstanding immediately after such
issue or sale. For purposes of this Section 2.5, all shares of Common Stock
issuable upon the exercise and/or conversion of all outstanding warrants
(including this Warrant), options and convertible securities shall be deemed to
be outstanding. The foregoing notwithstanding, no adjustment shall be made
pursuant to this Section 2.5 on account of a given issue or sale to the extent
that the Exercise Price is adjusted pursuant to any other Section of this
Warrant.

                  2.6 Certificate as to Adjustments. In the case of each
adjustment or readjustment of the purchase price pursuant to this Section 2, the
Company will promptly compute such adjustment or readjustment in accordance with
the terms hereof and cause a certificate setting forth such adjustment or
readjustment, and showing in detail the fact upon which such adjustment or
readjustment is based to be delivered to the holder of this Warrant. The Company
will, upon the written request at any time of the holder of this Warrant,
furnish or cause to be furnished to such holder a certificate setting forth:

                      (a) such adjustments and readjustments;

                      (b) the purchase price at the time in effect; and

                      (c) the number of Warrant Shares receivable upon the
exercise of the Warrant.

                  2.7 Notice of Record Date, etc. In the event of any taking by
the Company of a record of the holders of any class of securities of the Company
for the purpose of determining the holders thereof who are entitled to receive
any dividend (other than a cash dividend), or other distribution, or any right
to subscribe for, purchase or otherwise acquire any shares of stock of any class
or any other securities or property, or to receive any other right, or any
capital reorganization of the Company, any reclassification or recapitalization
of the capital stock of the Company, the Company will mail to the holder of this
Warrant at least twenty (20) days prior to the earliest date specified therein,
a notice specifying:

                           (a) The date on which such record is to be taken for
the purpose of such dividend, distribution, or right, and the amount and
character of such dividend, distribution, or right; or

                           (b) The date on which any such reorganization, or
reclassification is expected to become effective, and the record date for
determining shareholders entitled to vote thereon.

         3. Representations of Holder.

                  3.1 Investment Intent. Holder hereby warrants and represents
that Holder is acquiring this Warrant, and any Warrant Shares issued upon
exercise of this Warrant, for Holder's own account and not with a view to their
resale or distribution.

                                       5
<PAGE>   6

                  3.2 Exempt from Registration. Holder acknowledges that this
Warrant has not been registered under the Securities Act of 1933, as amended
(the "1933 Act"), on the ground that the issuance of this Warrant is exempt from
registration pursuant to Section 4(2) of the 1933 Act, and that the Company's
reliance on such exemption is predicated on the representations of Holder set
forth herein.

                  3.3 Investment Experience. In connection with the investment
representations made herein, Holder represents that it is able to fend for
itself in the transactions contemplated by this Warrant, has such knowledge and
experience in financial and business matters as to be capable of evaluating the
merits and risks of his investment, has the ability to bear the economic risks
of its investment and has been furnished with and has had access to such
information as it has requested and deemed appropriate to its investment
decision.

                  3.4 Restricted Securities. Holder hereby confirms that Holder
has been informed that this Warrant, and the Warrant Shares issued upon exercise
of this Warrant, are restricted securities under the 1933 Act and may not be
resold or transferred unless this Warrant, and the Warrant Shares issued upon
exercise of this Warrant, are first registered under the federal securities laws
or unless an exemption from such registration is available. Accordingly, Holder
hereby acknowledges that Holder is prepared to hold this Warrant, and the
Warrant Shares issued upon exercise of this Warrant, for an indefinite period
and that Holder is aware that Rule 144 of the Securities and Exchange Commission
issued under the 1933 Act is not presently available to exempt the issuance of
this Warrant from the registration requirements of the 1933 Act.

                           (a) Disposition of Shares. Holder hereby agrees that
Holder shall make no disposition of this Warrant, and the Warrant Shares issued
upon exercise of this Warrant, unless and until Holder shall have (i) provided
the Company with assurances that (A) the proposed disposition does not require
registration of the Warrant Shares under the 1933 Act, or (B) all appropriate
action necessary for compliance with the registration requirements of the 1933
Act or of any exemption from registration available under the 1933 Act
(including Rule 144) has been taken; and (ii) complied with the terms of the
Shareholders Agreement dated as of December 27, 1995 by and between the Company
and the holders of its capital stock (the "Shareholders Agreement").

                  3.5 Restrictive Legend. In order to reflect the restrictions
on disposition of the Warrant Shares, the stock certificates for the Warrant
Shares will be endorsed with the following restrictive legends to the following
effect:

         "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
         REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR THE
         SECURITIES LAWS OF ANY STATE AND MAY NOT BE SOLD OR OTHERWISE DISPOSED
         OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH
         ACT AND APPLICABLE STATE SECURITIES LAWS OR PURSUANT TO AN APPLICABLE
         EXEMPTION TO THE REGISTRATION REQUIREMENTS OF SUCH ACT OR SUCH LAWS.

                                       6
<PAGE>   7

         THE SHARES OF STOCK REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A
         SHAREHOLDERS AGREEMENT DATED AS OF MAY 18, 1998, AND AS MAY BE
         AMENDED FROM TIME TO TIME, AND SAID SHARES MAY NOT BE SOLD,
         TRANSFERRED, ASSIGNED, HYPOTHECATED OR OTHERWISE DISPOSED OF EXCEPT
         IN ACCORDANCE WITH THE TERMS OF SUCH AGREEMENT.  SUCH AGREEMENT MAY
         BE EXAMINED AT THE PRINCIPAL PLACE OF BUSINESS OF THE COMPANY AND A
         COPY THEREOF WILL BE FURNISHED WITHOUT CHARGE TO THE HOLDER OF THIS
         CERTIFICATE UPON RECEIPT BY THE COMPANY AT ITS PRINCIPAL PLACE OF
         BUSINESS OR REGISTERED OFFICE OF A WRITTEN REQUEST FROM THE
         SHAREHOLDER.

         4. Representations, Warranties and Covenants. This Warrant is issued
and delivered by the Company and accepted by each Holder on the basis of the
following representations, warranties and covenants made by the Company:

                  4.1 The Company covenants that it will at all times from and
after the date hereof reserve and keep available such number of its authorized
shares of Series A Preferred Stock and Common Stock, $.001 par value, of the
Company (the "Common Stock"), as will be sufficient to permit, respectively, the
exercise of this Warrant in full and the conversion into shares of Common Stock
of all shares of Series A Preferred Stock receivable upon such exercise. The
Company covenants further that such shares as may be issued pursuant to such
exercise and/or conversion will, upon issuance, be duly and validly issued,
fully paid and nonassessable and free from all taxes, liens and charges with
respect to the issuance thereof.

                  4.2 The Company has all necessary authority to issue, execute
and deliver this Warrant and to perform its obligations hereunder. This Warrant
has been duly authorized issued, executed and delivered by the Company and is
the valid and binding obligation of the Company, enforceable in accordance with
its terms.

                  4.3 The shares of Series A Preferred Stock issuable upon the
exercise of this Warrant have been duly authorized and reserved for issuance by
the Company and, when issued in accordance with the terms hereof, will be
validly issued, fully paid and nonassessable.

                  4.4 The issuance, execution and delivery of this Warrant do
not, and the issuance of the shares of Series A Preferred Stock upon the
exercise of this Warrant in accordance with the terms hereof will not, (i)
violate or contravene the Company's Articles or bylaws, or any law, statute,
regulation, rule, judgment or order applicable to the Company, (ii) violate,
contravene or result in a breach or default under any contract, agreement or
instrument to which the Company is a party or by which the Company or any of its
assets are bound or (iii) require the consent or approval of or the filing of
any notice or registration with any person or entity.

         5. Fractional Shares. No fractional shares shall be issued in
connection with any exercise of this Warrant. In lieu of the issuance of such
fractional shares, the Company shall make a cash payment equal to the then fair
market value of such fractional share as determined in good faith by the
Company's Board of Directors pursuant to Section 1.4(b) above.

                                       7
<PAGE>   8

         6. No Privilege of Stock Ownership. Prior to the exercise of this
Warrant, the Holder shall not be entitled, by virtue of holding this Warrant, to
any rights of a stockholder of the Company, including (without limitation) the
right to vote, receive dividends or other distributions, or exercise preemptive
rights, and such holder shall not be entitled to any notice or other
communication concerning the business or affairs of the Company. Nothing in this
Section 6, however, shall limit the right of the Holder to be provided the
notices required herein, or to participate in distributions described in Section
2 hereof if the Holder ultimately exercises this Warrant. Notwithstanding the
foregoing, upon exercise of this Warrant, Holder shall be deemed to be a
"Holder" and "Holder of Registrable Securities" pursuant to Section 2.2 and 2.3
of the Investor Rights Agreement dated as of May 18,. 1998, as amended, by and
among the Company and certain of its shareholders; provided, that as a condition
of receiving such registration rights, Holder agrees to execute such Investor
Rights Agreement as requested by the Company.

         7. Transfers or Exchanges.

                  7.1 Subject to compliance with the Shareholders Agreement and
applicable federal and state securities laws, this Warrant and all rights
hereunder are transferable in whole or in part by the Holder to any person or
entity reasonably acceptable to the Company. The Holder will provide written
notice of such transfer to the Company, and if no written objection from the
Company is received by the Holder within five business days after the date of
notice, then such transfer shall be deemed accepted. The transfer shall be
recorded on the books of the Company upon the surrender of this Warrant,
properly endorsed, to the Company at its principal offices, and the payment to
the Company of all transfer taxes and other governmental charges imposed on such
transfer. In the event of a partial transfer, the Company shall issue to the
holders one or more appropriate new warrants.

                  7.2 All new warrants issued in connection with transfers,
exchanges or partial exercises shall be identified in form and provision to this
Warrant, except as to the number of shares.

                  7.3 Holder hereby agrees that, during the period of duration
(not to exceed 180 days) specified by the Company and an underwriter of Series A
Preferred Stock or other securities of the Company, following the effective date
of an IPO, it shall not, to the extent requested by the Company and such
underwriter, directly or indirectly sell, offer to sell, contract to sell
(including, without limitation, any short sale), grant any option to purchase or
otherwise transfer or dispose of (other than to donees who agree to be similarly
bound) any securities of the Company held by it at any time during such period
except Common Stock included in such registration; provided, however, that all
officers and directors of the Company enter into similar agreements.

         8. Successors and Assigns. The terms and provisions of this Warrant
shall be binding upon the Company, the Holder, and their respective successors
and assigns, subject at all times to the restrictions set forth in the Agreement
and in this Warrant.

         9. Loss, Theft, Destruction or Mutilation of Warrant. Upon receipt of
notice by the Company of the loss, theft, destruction, or mutilation of this
Warrant, and upon reimbursement to the Company of all reasonable expenses
incidental thereto, and, if mutilated upon surrender and

                                       8
<PAGE>   9

cancellation of this Warrant, the Company will make and deliver a new warrant,
in identical form, and dated as of such cancellation, in lieu of this Warrant.

         10. Saturdays, Sundays, Holidays, etc. If the last or appointed day for
the taking of any action, or the expiration of any right required or granted
herein shall be a Saturday, or Sunday, or
shall be a legal holiday, then such action may be taken or such right may be
exercised, except as to the purchase price, on the next succeeding day not a
legal holiday.

         11. Amendments and Waivers. Any term of this Warrant may be amended,
and the observance of any term of this Warrant may be waived (either generally
or in a particular instance, and either retroactively or prospectively), with
the written consent of the Company and the Holder, such consent not to be
unreasonably withheld. Any such amendment or waiver shall be binding on the
Holder.

         12. Governing Law. This Warrant shall be governed by and construed in
accordance with the laws of the State of Colorado.

         13. Notices. Any notice, demand or delivery pursuant to the provisions
hereof shall be sufficiently delivered or made if sent by first class mail,
postage prepaid, addressed to any holder of a Warrant at its last known address
appearing on the books of the Company, or, except as herein otherwise expressly
provided, to the Company at its principal executive office at 1885 33rd Street,
Boulder, Colorado, 80301, or such other address as shall have been furnished to
the party giving or making such notice, demand or delivery.

                  DATED:  March 30, 1999

                                 Array BioPharma Inc., a Delaware corporation

                                 By: /s/ MIKE CARRUTHERS
                                     ---------------------------
                                 Print Name:  Mike Carruthers
                                 Title:  Chief Financial Officer

                                        9
<PAGE>   10

                                    EXHIBIT A

                                  Subscription

Array BioPharma Inc.

Ladies and Gentlemen:

         The undersigned hereby elects to purchase, pursuant to the provisions
of the Warrant dated March 31, 1999, __________ shares of the Series A Preferred
Stock of Array BioPharma Inc., a Delaware corporation.

Dated: _______________, ______

                                   Leasing Technologies International, Inc.

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

<PAGE>   11

                                    EXHIBIT B

                               Net Issue Election

Array BioPharma Inc.

Ladies and Gentlemen:

         The undersigned hereby elects under Section 1.4 of the Warrant dated
March 31, 1999 (the "Warrant"), to exercise its right to receive ______________
shares of Series A Preferred Stock pursuant to the Warrant. The certificate(s)
for such shares issuable upon such net issue election shall be issued in the
name of the undersigned or as otherwise indicated below:

         Name for Registration:
                               -------------------------------------------------

         Mailing Address:
                               -------------------------------------------------

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

                                   Leasing Technologies International, Inc.

                                   By: /s/
                                      ------------------------------------------
                                   Name:
                                        ----------------------------------------
                                   Title:
                                         ---------------------------------------<PAGE>   1
                                                                   EXHIBIT 10.29

[ * ] Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 406 of the Securities Act of 1933, as amended.

                                CUSTOM SYNTHESIS
                            FEE-FOR-SERVICE AGREEMENT
                                 by and between
                                MERCK & CO., INC.
                                       and
                                 ARRAY BIOPHARMA

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

This Agreement (the "Agreement") confirms the mutual understanding by and
between Merck & Co., Inc., a New Jersey corporation with a place of business at
126 E. Lincoln Avenue, Rahway, New Jersey 07065-0900 ("MERCK") and Array
BioPharma, a Delaware corporation with a place of business at 1885 33rd Street,
Boulder, Colorado 80301 ("ARRAY BIOPHARMA").

1. Purpose and Scope. ARRAY BIOPHARMA agrees to diligently perform services
("Services") required to synthetically prepare the desired proprietary organic
compounds ("Products") requested by MERCK (or by one or more Affiliates
designated by MERCK) under this Agreement. For the purposes of this Agreement,
Affiliates shall mean any entities controlling, controlled by, or under common
control with, MERCK and ARRAY BIOPHARMA, respectively. Control shall mean the
ownership of at least 50% of the equity interests in or voting control of the
identified entity.

         (a) For each proposed Service to be initiated under this Agreement,
MERCK shall submit to ARRAY BIOPHARMA, at no cost, a written request
("Requisition") stating the chemical structure(s) and gram quantity (or molar
equivalent) amount(s) of the desired Product(s), including any synthetic routes
to such chemical structure(s) and other specifications (the foregoing together
with Purchase Orders and other non-public information generated by MERCK,
hereinafter shall be referred to as "MERCK Know-How") and/or chemical material
("MERCK Material"). ARRAY BIOPHARMA shall be permitted to use such Requisition
for the sole purpose of evaluating its interest to synthetically prepare
Product(s) described therein for MERCK. Within thirty (30) days of receipt of
said Requisition, ARRAY BIOPHARMA shall advise MERCK of its interest to
synthetically prepare the Product(s) embodied in the Requisition by submitting
to MERCK a written bid stating the proposed start and delivery dates, total
costs of preparing and gram quantity amount of the Product(s) that ARRAY
BIOPHARMA agrees to provide ("Quote"). Within thirty (30) days of MERCK's
receipt of a Quote, MERCK shall advise ARRAY BIOPHARMA in writing of the
acceptance of each submitted Quote, and upon such acceptance, shall initiate an
Authorized Purchase Order.

         (b) The MERCK Material is not to be used in humans. It is understood
that the MERCK Know-How and MERCK Material are provided only for the proposed
Service to be carried out hereunder and shall not be used for any other purpose
nor shall the MERCK Know-How or MERCK Material or any derivatives, analogs,
modifications or components thereof or information about said MERCK Know-How or
MERCK Material be transferred, delivered or disclosed to any third party without
the prior written consent of MERCK. [ * ]. Any and all unused MERCK Material
shall, at MERCK's expense and election, be returned to MERCK promptly upon
completion of such Service or otherwise disposed of in accordance with
instructions from MERCK.

         (c) For each Service initiated under this Agreement, ARRAY BIOPHARMA
shall deliver to MERCK the agreed upon amount [ * ] of each synthetically
prepared Product, accompanied by a writing in English, in electronic or
hard-copy format, which describes the step-wise synthetic procedure carried out
to prepare each Product ("Product Report") and liquid chromatography-mass
spectral (LC-MS) analysis to prove chemical identity and confirm overall purity
[ * ]. [ * ]

[ * ] Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 406 of the Securities Act of 1933, as amended.

<PAGE>   2

         (D) [ * ]. ARRAY BIOPHARMA shall advise MERCK of all quantities of the
Product(s) generated in excess of the Authorized Purchase Order. [ * ]. MERCK
may agree to purchase additional quantities of Product(s) at a discounted price
mutually agreed upon by the parties in writing, and ARRAY BIOPHARMA agrees to
dispose of any additional remaining quantities of Product(s) in accordance with
instructions from MERCK.

2. Term and Termination. The term of this Agreement shall be for a period of
[ * ] years, effective upon execution of this Agreement by both parties. MERCK
may terminate this Agreement [ * ] upon written notice to ARRAY BIOPHARMA. Upon
termination of this Agreement, or at any other time that MERCK might request,
ARRAY BIOPHARMA promptly shall return all papers, records and other documents
embodying MERCK confidential information, including all MERCK Material supplied
by MERCK, and all embodiments of MERCK Know-How, including all documents,
materials and Products generated by ARRAY BIOPHARMA in connection with the
Services provided under this Agreement, except that ARRAY BIOPHARMA may retain
one copy of such papers, records and other documents for record keeping
purposes. Termination of this Agreement for any reason shall not release either
party hereto from any liability which, at the time of such termination, has
already accrued to the other party or which is attributable to a period prior to
or as a result of such termination.

3. Amount. MERCK shall pay ARRAY BIOPHARMA the negotiated amount set forth in
the Authorized Purchase Order to cover total costs and expenses for each Service
initiated under this Agreement, with payment in full to be made within sixty
(60) days of delivery of the Product(s) to MERCK in accordance with the
conditions set forth in Section 1 of this Agreement. Such costs shall include
the preparation and shipment, per custom packaging instructions provided by
MERCK with the Authorized Purchase Order, of stated gram quantity amount (or
molar equivalent of salt forms) of the Product to MERCK. MERCK shall have no
obligation to make any payments whatsoever to ARRAY BIOPHARMA or bear any costs
or expenses for any Product which is not in compliance with the purity and
structural characterization criteria or other specifications set forth herein,
in the Requisition, or otherwise provided by MERCK to ARRAY BIOPHARMA. Under no
circumstances shall MERCK have any obligations to ARRAY BIOPHARMA beyond those
set forth hereunder. MERCK shall not be obligated to make any payments
whatsoever to ARRAY BIOPHARMA or bear any costs or expenses for any Services
beyond those set forth in the Authorized Purchase Order or requested in
connection with a subsequent mutual written agreement.

4. Confidentiality. ARRAY BIOPHARMA agrees to keep confidential and not to use,
except to perform for MERCK the Services under this Agreement, all information,
MERCK Know-How and MERCK Material supplied by MERCK and all information and
Products generated by ARRAY BIOPHARMA as a result of the Services performed
pursuant to this Agreement. ARRAY BIOPHARMA agrees not to disclose to any third
party any information, MERCK Know-How, MERCK Material or Products concerning
Services being conducted hereunder without MERCK's prior written consent. These
obligations of confidentiality and non-use shall continue at all times beyond
the term of this Agreement. ARRAY BIOPHARMA shall not use any third party trade
secrets, processes, methodologies or reagents in generating any Product(s) for
MERCK hereunder. This Agreement shall not restrict ARRAY BIOPHARMA's use or
disclosure of certain expected information which (i) is in the public domain by
use and/or publication before its receipt from MERCK, (ii) was already in ARRAY
BIOPHARMA'S possession prior to receipt from MERCK; (iii) is properly obtained
by ARRAY BIOPHARMA from a third party which has a valid legal right to disclose
such information to ARRAY BIOPHARMA and is not under a confidentiality
obligation to MERCK; or (iv) ARRAY BIOPHARMA is required by law or a court of
competent jurisdiction to make provided, however, to the extent it may legally
do so, ARRAY BIOPHARMA will give reasonable advance notice to MERCK of

[ * ] Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 406 of the Securities Act of 1933, as amended.

<PAGE>   3

such disclosure and reasonably assist MERCK to secure confidential treatment of
MERCK confidential information prior to its disclosure (whether through
protective orders or otherwise) (collectively, the "Exceptions"). ARRAY
BIOPHARMA agrees to advise MERCK of the applicability of any of the foregoing
Exceptions for any Product(s) or the synthetic preparation thereof that Array
BIOPHARMA is aware of in connection with any Services hereunder, and shall
advise MERCK of same in connection with the provision of the Quote; provided,
however, failure to do so shall not prevent ARRAY BIOPHARMA from relying on such
Exception.

5. Reports: Use of Information. ARRAY BIOPHARMA shall keep MERCK informed of the
status and progress of Services through written reports on a monthly basis which
shall continue through completion of each Service and delivery of the
Product(s), at which time ARRAY BIOPHARMA shall submit the Product Report as
outlined in Section 1 of this Agreement. ARRAY BIOPHARMA agrees to keep
confidential and not to use, except in connection with the Services provided
under this Agreement, all MERCK Know-How included in any and all written and
electronic copies of the aforementioned reports. [ * ]. At MERCK's request,
ARRAY BIOPHARMA shall provide to MERCK copies of all documentation relating to
the Services performed hereunder or shall permit MERCK to inspect and copy such
documentation.

6. Inventions.  [ * ]

7. Compliance with Law. ARRAY BIOPHARMA shall conduct the research in accordance
with the applicable laws, rules and regulations, including, without limitation,
all current governmental regulatory requirements concerning Good Laboratory
Practices. ARRAY BIOPHARMA hereby certifies that it will not or has not employed
or otherwise used in any capacity the services of any person debarred under
Section 306 (a) or (b) of the Federal Food, Drug, and Cosmetic Act in performing
any Services hereunder.

8. Authorized Purchase Orders. The terms of any Authorized Purchase Order and
any Requisition are in addition to the terms of this Agreement, and this
Agreement shall control over any terms in any Quote.

[ * ] Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 406 of the Securities Act of 1933, as amended.

<PAGE>   4

9. Liability. MERCK assumes no responsibility and shall have no liability for
the nature, conduct or results of any research, testing or other work performed
pursuant to the Services hereunder.

10. Indemnity. ARRAY BIOPHARMA hereby agrees to indemnify and hold harmless
MERCK, its subsidiaries and affiliates and their respective officers, employees
and directors against any and all liability, loss, damages, cost or expense
(including attorney's fees and expenses and costs of investigation) which any of
them may hereafter incur, suffer, or be required to pay as the result of any
damage suffered or alleged to be suffered, including, without limitation, death
or personal injury and any direct, consequential, special and punitive damages,
as the result of the Services being performed by ARRAY BIOPHARMA hereunder;
provided, however, that such loss, liability or damage is not attributable to
the fraud, gross negligence, malfeasance or willful misconduct of MERCK.
Notwithstanding the foregoing, ARRAY BIOPHARMA assumes no responsibility and
shall have no liability for MERCK's use of any of the results of the Services or
Product(s) provided to MERCK hereunder.

MERCK hereby agrees to indemnify and hold harmless ARRAY BIOPHARMA, its
subsidiaries and affiliates and their respective officers, employees and
directors against any and all liability, loss, damages, cost or expense
(including attorney's fees and expenses and costs of investigation) which any of
them may hereafter incur, suffer or be required to pay as the result of any
damage suffered or alleged to be suffered, including without limitation, death
or personal injury and any direct, consequential, special and punitive damages,
as the result of MERCK's use of any of the Products provided to MERCK hereunder;
provided, however, that such loss, liability or damage is not attributable to
the fraud, gross negligence, malfeasance or willful misconduct of ARRAY
BIOPHARMA.

11. Public Announcements. ARRAY BIOPHARMA shall hold in confidence all
information concerning this Agreement and the terms hereof and shall not make
any public statement or announcement about it, nor issue new releases or
advertising relating to the existence or implementation of this Agreement or the
subject matter thereof without the prior written consent of MERCK. ARRAY
BIOPHARMA shall not use the name "Merck", Merck & Co., Inc., or any trademarks,
trade names or logos of MERCK without MERCK's prior written consent.

12. Independent Contractors. It is not the intent of ARRAY BIOPHARMA and MERCK
to form any partnership or joint venture, and nothing contained herein shall be
construed to empower either party to act as an agent for the other. The parties
agree that each of them shall, in relation to its obligations hereunder, be
acting as an independent contractor.

13. Assignment. [ * ]

14. Force Majeure. Neither ARRAY BIOPHARMA nor MERCK shall be liable to the
other in damages for, nor shall this Agreement be terminable or cancelable by
reason of, any delay or default in such party's performance hereunder if such
default or delay is caused by events beyond such party's reasonable control
including, but not limited to, acts of God; acts or omissions of any government;
any rule, regulation or order issued by any governmental authority or by any
officer, department, agency or instrumentality thereof; fire; storm; flood;
earthquake; accident; war; rebellion; insurrection; riot; invasion; or strike,
lockout or other work stoppage provided that such failure or omission is cured
as is practicable after the occurrence of the force majeure.

[ * ] Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 406 of the Securities Act of 1933, as amended.

<PAGE>   5

15. Contacts. All correspondence, Requisitions, Quotes and Authorized Purchase
Orders pertaining to this Agreement should be directed to [ * ], Merck Research
Laboratories, in the case of MERCK, and [ * ] in the case of ARRAY BIOPHARMA.

16. No Obligation. It is understood and agreed that the entering into of this
Agreement and receipt of Quotes by MERCK shall not impose any obligation upon
MERCK to submit any Requisitions to ARRAY BIOPHARMA or to accept any Quote
submitted by ARRAY BIOPHARMA. MERCK retains the sole discretion to select
vendors for submission of Requisitions and acceptance of Quotes.

--------------------------------------------------------------------------------
IN WITNESS WHEREOF, the parties have caused this Agreement to be executed below
by duly authorized representatives.

         MERCK & CO., INC.

BY       /s/ Thomas N. Salzman, Ph.D.                DATE   5/14/99
         --------------------------------------           ----------------
         Thomas N. Salzmann, Ph.D.

TITLE    Senior Vice President, Basic Chemistry
         --------------------------------------

         ARRAY BIOPHARMA

BY       /s/ David Snitman                           DATE   5/25/99
         --------------------------------------           ----------------
         David Snitman

TITLE    Chief Operating Officer
         --------------------------------------

[ * ] Certain confidential information contained in this document, marked by
brackets, has been omitted and filed separately with the Securities and Exchange
Commission pursuant to Rule 406 of the Securities Act of 1933, as amended.

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00015-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00015-of-00352.parquet"}]]