<PAGE>

                              LMSI Venture Finance
                         2500 Sand Hill Road, Suite 101.
                              Menlo Park, CA 94025
                 Telephone; (650) 854-9450 o Fax: (650) 854-9457


July 28, 1999

                                                                         Revised
                                                                         -------
Mr. David J. Borges
Controller
Rosetta Inpharmatics, Inc.
12040 115th Avenue, NE
Kirkland, WA 98034
Dear David:

This will confirm approval of a time and line extension of $605,000 for Rosetta
Inpharmatics. The terms will be the same as Rosetta's prior line (5/13/98
proposal and subsequent credit approval) except that

         -        Equipment allotments have been changed to allow more soft
                  costs. The new allotments are lab and test equipment (> 32%);
                  computers, furniture, & similar (=34%); and soft costs
                  (leaseholds, software, & similar) (Greater than or equal to
                  34%)

         -        LMSI will retain a continuing lien on all equipment financed
                  or to be financed under Equipment Financing Agreements #10819
                  and #10821 until all of Rosetta's obligations under this new
                  financing are fulfilled. (With LMSI's prior approval, Rosetta
                  may sell or dispose of some items of equipment)

         -        The line expires 6/30/00, however, fundings after 12/31/99 are
                  contingent upon Rosetta closing a major corporate partnership
                  as represented.

Cynthia Murayama, Contract Manager, will be calling shortly to update
information and to expedite the few additional documents we need. Equipment
purchased since the expiration of Rosetta's prior line may be financed under
this line. Please send any invoices you have accumulated.

We are delighted to be able to continue working with you and with Rosetta!

Best regards,

/s/ Barbara Kaiser

Barbara B.. Kaiser
EVP/ General Manager


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                         Lease Management Services, Inc.
                         2500 Sand Hill Road. Suite 101
                               Menlo Park CA 94025
                  Telephone (650) 854-9450 o Fax (650) 854-9457


April 24, 1998
Revised: May 13, 1998

Mr. John J. King, II                                               CONFIDENTIAL
Chief Operating Officer
Rosetta Inpharmatics, Inc.
12040 115th Avenue NE
Kirkland, WA 98034

Dear John:

We are pleased to present the following equipment financing proposal to Rosetta
Inpharmatics, Inc.:

         BORROWER:         Rosetta Inpharmatics, Inc.

         LENDER:           Lease Management Services, Inc.

         EQUIPMENT:        A master line of credit for $1,500,000 equipment per
                           the attached list, including:

                    Greater than or equal to  $750,000   lab & scientific
                                                         equipment

                    Less than or equal to      500,000   computers, furniture &
                                                         similar

                    Greater than or equal to   250,000   leaseholds, software &
                                                         similar
                                            -------
                                          $1,500,000

                           Previously-purchased and used equipment may be
                           included in this line. All equipment is subject to
                           Lenders final approval.

TERM &
PAYMENT:

                           OPTION 1: Forty-two (42) months at 2.604% of
                           equipment cost, payable monthly in advance for each
                           loan schedule, plus a 15% balloon at end of term.
                           [Subject to satisfactory credit review, the balloon
                           may be paid over 9 months at 1.740% per month.]

                           OPTION 2: Forty-eight (48) months at 2.615% of
                           equipment cost, payable monthly in advance for each
                           loan schedule, plus a $1.00 payment at end of term.


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<PAGE>

                           The yield in this transaction will be adjusted
                           relative to any increase in comparable term U.S.
                           Treasury maturities. The payment factor for each
                           schedule will be set at the time it is documented and
                           will be FIXED for the term. The payment factors above
                           are based on the average of the Federal Reserve 3-
                           and 5-year treasuries (5.575%) for the week ending
                           4/17/98.

STRUCTURE:                 Secured loan. Borrower retains title and keeps
                           depreciation. Borrower will grant Lender a first
                           security interest in the equipment to be financed.

WARRANT:                   In consideration for this financing, Borrower will
                           grant to Lender a warrant to purchase Borrower's
                           common or preferred stock. The warrant will be for
                           2.5% of equipment cost at the lower of $5.20 per
                           share or Borrower's next round (> $2MM new - equity)
                           share price. The exercise price will be the lower of
                           $5.20 per share or the price half-way between the
                           price per share of Borrower's Series A and next round
                           financing. The warrant will be for the greater of
                           7,000 shares or the number of shares based pro rata
                           on the actual amount of equipment financed. The
                           warrant may be exercised by cash or net issue and
                           will include standard anti-dilution provisions. The
                           exercise period shall end 72 months from the date of
                           issue.

COVENANT:                  No additional collateral will be required except in
                           the event Borrower's unrestricted cash, excluding
                           long-term debt, falls below the appropriate benchmark
                           below. In that event, Borrower will provide to Lender
                           a cash security deposit equivalent to 12.5% of
                           original, aggregate equipment cost, but in no event
                           to exceed the remaining gross receivable.

                           PRE-IPO BENCHMARK: unrestricted cash, excluding
                           long-term debt, must be equal to the greater of
                           $2,000,000 or 6 months' cash needs. ["6 months' cash
                           needs" will be defined as the cash bum for the 3
                           months just completed, multiplied by a factor of
                           2.3.]

                           POST-IPO BENCHMARK: unrestricted cash, excluding
                           long-term debt, must be equal to the greater of
                           $5,000,000 or 10 months' cash needs. ["10 months'
                           cash needs" will be defined as the cash burn for the
                           3 months just completed, multiplied by a factor of
                           3.6.]

                           Interest will be accrued at 5.0% annually and will be
                           paid with the return of the deposit.

                           This deposit will be released when Borrower's
                           unrestricted cash, excluding long-term debt, recovers
                           and is greater than the appropriate benchmark above
                           for at least one quarter and continues to remain
                           greater. (Or, will be returned immediately if
                           Borrower's new equity or other non-refundable cash is
                           great enough to dearly keep Borrower above the
                           appropriate benchmark for at least three quarters.)


                                      -3-
<PAGE>

                           Verification of achievement of benchmarks is to be
                           acceptable to Lender. Return of deposits prior to end
                           of term is contingent upon receipt of all payments
                           and financials to date as agreed, no default under
                           any financial obligation, and no material adverse
                           change.

CONTINGENCIES:

                           1)       Standard documentation satisfactory to
                                    Borrower and Lender.

                           2)       Releases against this credit line are
                                    contingent upon Borrower providing evidence
                                    of reasonable performance against the 1998
                                    Budget or subsequent Board-approved plan
                                    acceptable to Lender. This credit line,
                                    unless extended in writing, expires 5/31/99.

                           3)       Throughout the loan term, Borrower will
                                    provide monthly financials within 30 days of
                                    each month-end, and annually, an audited
                                    statement within 90 days of fiscal year end
                                    or at such time as Borrower's Board receives
                                    the audit All such financial statements are
                                    to be prepared using generally accepted
                                    accounting principles.

                           4)       Invoices must be less than 45 days old ~
                                    funded within 45 days of credit approval.

                                    All equipment is to be located at Borrower's
                                    Seattle area facilities unless Lender gives
                                    prior approval to do otherwise.

                                    Custom equipment; upgrades to equipment to
                                    which Lender does not have clear title or
                                    first security interest; disposables; and
                                    "soft costs" such as sales tax, freight, and
                                    installation are excluded from this line.

                           5)       Subject to final approval by Lender's Credit
                                    Committee.

                           6)       This is a statement of mutual intent and not
                                    an agreement to finance. The terms set forth
                                    above are not therefore binding until a loan
                                    agreement is executed between Borrower and
                                    Lender for specific items of equipment.

COMMITMENT
FEE:                       $10,000.00 commitment fee. This fee shall be fully
                           credited pro-rata to schedules as financed. All or a
                           portion of said fee will be forfeited If this
                           transaction is approved by Lender and not executed by
                           Borrower as called for in this proposal. However, in
                           the event Borrower uses the line in good faith but
                           does not use the entire line, then any remaining fee
                           will be applied to any new line agreed to by Borrower
                           and Lender prior to


                                      -4-
<PAGE>

                           9/30/98. The entire fee will be returned to Borrower
                           promptly in the event Len4er fails to approve this
                           transaction.

If the terms of this proposal meet with your approval, please sign and return
with your commitment fee, and we will proceed. Unless previously accepted, this
proposal will expire 5/16/98.

We look forward to meeting your equipment financing needs and continuing a
mutually rewarding relationship.

----------------------------- --------------------------------------------------
Sincerely,                    ACCEPTED:  Rosetta Inpharmatics, Inc.

/s/ Barbara B. Kaiser         By: /s/
                                  ------------------------------------------
Barbara B. Kaiser             Title: SR. V.P. & C.O.O.
EVP/General Manager                  ---------------------------------------
                              Date: MAY 14, 1998
                                    ----------------------------------------
----------------------------- --------------------------------------------------


Pricing:

         Option 1:
                  ------
         Option 2:   X
                  ------


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