Document:

<PAGE>   1
                                                                    EXHIBIT 4.10

THE SECURITIES REPRESENTED BY THIS INSTRUMENT HAVE BEEN ACQUIRED FOR INVESTMENT
AND NOT WITH VIEW TO, OR IN CONNECTION WITH, THE SALE OR DISTRIBUTION THEREOF.
NO SUCH SALE OR DISPOSITION MAY BE AFFECTED WITHOUT AN EFFECTIVE REGISTRATION
STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL REASONABLY ACCEPTABLE TO THE
COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT OF 1933.

No. WA-__

                             STOCK PURCHASE WARRANT
               To Purchase Shares of Series A Preferred Stock of
                                VIROLOGIC, INC.

      THIS CERTIFIES that pursuant to that certain lease (the "Lease") between
Virologic, Inc. (the "Company") and Britannia Developments, Inc. ("Landlord")
and upon the terms and subject to the conditions hereinafter set forth,
________________, a Delaware corporation ("Holder") may at any time on or after
the date of this Warrant and on or prior to August 22, 2002, but not thereafter,
subscribe for and purchase, from the Company, up to _______ shares of Series A
Preferred Stock. The purchase price of one share of Series A Preferred Stock
issuable under this Warrant shall be $4.00. The purchase price and the number of
shares for which the Warrant is exercisable shall be subject to adjustment as
provided herein.

      1.    EXERCISE OF WARRANT.

            (a)   EFFECTIVENESS OF WARRANT. This Warrant shall not be
exercisable for any shares of Series A Preferred Stock until the Commencement
Date (as defined in the Lease) has occurred with respect to all of the Premises
(as defined in the Lease) and the Premises have been delivered in the condition
required by Section 2.4 of the Lease.

            (b)   CASH EXERCISE. Unless earlier terminated under Section 7 and
only to the extent then exercisable pursuant to Sections 1 (a) above, the
purchase rights represented by this Warrant are exercisable by Holder, in whole
or in part, at any time after the date hereof and before the close of business
on August 22, 2002 by the surrender of this Warrant and the Notice of Exercise
annexed hereto duly executed at the office of the Company, in South San
Francisco, California (or such other office or agency of the Company as it may
designate by notice in writing to the registered holder hereof at the address
of such holder appearing on the books of the Company), and upon payment of the
purchase price of the shares of Series A Preferred Stock thereby purchased (by
cash or by check or bank draft payable to the order of the Company in an amount
equal to the purchase price of the shares thereby purchased); whereupon the
holder of this Warrant shall be entitled to receive a certificate for the
number of shares of Series A Preferred Stock so purchased. The Company agrees
that if at the time of the surrender of this Warrant and purchase of the
shares, the holder hereof shall be entitled to exercise this Warrant, and the
shares so purchased shall be and be deemed to be issued to such holder as the
record owner of such shares as of the close of business on the date on which
this Warrant shall have been exercised as aforesaid.

                                       1.

<PAGE>   2
      Certificates for shares of Series A Preferred Stock purchased hereunder
shall be delivered to the holder hereof within a reasonable time after the date
on which this Warrant shall have been exercised as aforesaid.

            (c)   NET EXERCISE. In lieu of the cash payment set forth in
Section 1(b) above and provided that the Company's Series A Preferred Stock has
converted to Common Stock pursuant to a public offering, the Holder shall have
the right, to convert this Warrant in its entirety (without payment of any
kind) into that number of shares of Common Stock equal to the quotient obtained
by dividing the Net Value (as defined below) of the shares of Common Stock then
exercisable under this Warrant by the Fair Market Value (as defined below) of
one share of Common Stock. For purposes of this Section 1(c), (i) the Fair
Market Value of Common Stock means the average of the closing prices quoted on
the National Association of Securities Dealers Automated Quotation System
("NASDAQ") National Market System ("NMS") (or, if then traded on a national
securities exchange, the closing prices on the principal national securities
exchange on which it is listed, or, if quoted on NASDAQ, the average of the
closing bid and asked prices) on each of the twenty (20) trading days
immediately preceding the date of exercise; and (ii) the Net Value of the
shares means the aggregate Fair Market Value of the shares of Common Stock then
exercisable under this Warrant minus the aggregate purchase price for the
shares of Common Stock then exercisable under this Warrant.

      2.    NO FRACTIONAL SHARES OR SCRIP. No fractional shares or scrip
representing fractional shares shall be issued upon the exercise of this
Warrant. With respect to any fraction of a share called for upon the exercise
of this Warrant, an amount equal to such fraction multiplied by the then
current price at which each share may be purchased hereunder shall be paid in
cash to the holder of this Warrant.

      3.    CHARGES, TAXES AND EXPENSES. Issuance of certificates for shares to
be received upon the exercise of this Warrant shall be made without charge to
the holder hereof for any issue or transfer tax or other incidental expense in
respect of the issuance of such certificate, all of which taxes and expenses
shall be paid by the Company, and such certificates shall be issued in the name
of the holder of this Warrant.

      4.    NO RIGHTS AS STOCKHOLDERS. This Warrant does not entitle the holder
hereof to any voting rights or other rights as a stockholder of the Company
prior to the exercise thereof.

      5.    LOSS, THEFT, DESTRUCTION OR MUTILATION OF WARRANT. Upon receipt by
the Company of evidence reasonably satisfactory to it of the loss, theft,
destruction or mutilation of this Warrant, and in case of loss, theft or
destruction, of indemnity or security reasonably satisfactory to it, and upon
reimbursement to the Company of all reasonable expenses incidental thereto, and
upon surrender and cancellation of this Warrant, if mutilated, the Company will
make and deliver a new Warrant of like tenor and dated as of such cancellation,
in lieu of this Warrant.

      6.    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 a Sunday or shall be a legal holiday, then such
action may be taken or such right may be exercised on the next succeeding day
not a legal holiday.

                                       2.
<PAGE>   3
     7.   EARLY TERMINATION AND DILUTION.

          (a)  EARLY TERMINATION ON MERGER, ETC. If at any time the Company
proposes to merge with or into any other corporation, effect a reorganization,
or sell or convey all or substantially all of its assets to any other entity in
a transaction in which the stockholders of the Company immediately before the
transaction own immediately after the transaction less than a majority of the
outstanding voting securities of the surveying entity (or its parent), then the
Company shall give the undersigned at least thirty (30) days notice of the
proposed effective date of the transaction and, if the Warrant has not been
exercised by the effective date of the transaction, the Warrant shall
terminate. The exercise of this Warrant may be conditioned upon the
effectiveness of the transaction.

          (b)  RECLASSIFICATION, ETC. If the Company at any time shall, by
subdivision, conversion, combination or reclassification of securities or
otherwise, change any of the securities to which purchase rights under this
Warrant exist into the same or a different number of securities of any class or
classes, this Warrant shall thereafter be to acquire such number and kind of
securities as would have been issuable as the result of such change with
respect to the securities which were subject to the purchase rights under this
Warrant immediately prior to such subdivision, combination, reclassification or
other change. If shares of the Company's Series A Preferred Stock are
subdivided or combined into a greater or smaller number of shares of Series A
Preferred Stock, the purchase price under this Warrant shall be proportionately
reduced in case of subdivision of shares or proportionately increased in the
case of combination of shares, in both cases by the ratio which the total
number of shares of Series A Preferred Stock to be outstanding immediately after
such event bears to the total number of shares of Series A Preferred Stock
outstanding immediately prior to such event.

          (c)  CASH DISTRIBUTIONS. No adjustment on account of cash dividends
or interest on the Company's Series A Preferred Stock or other securities
purchasable hereunder will be made to the purchase price under this Warrant.

          (d)  AUTHORIZED SHARES. The Company covenants that during the period
the Warrant is outstanding, it will reserve from its authorized and unissued
Series A Preferred Stock a sufficient number of shares to provide for the
issuance of Series A Preferred Stock upon the exercise of any purchase rights
under this Warrant. The Company further covenants that its issuance of this
Warrant shall constitute full authority to its officers who are charged with
the duty of executing stock certificates to execute and issue the necessary
certificates for shares of the Company's Series A Preferred Stock upon the
exercise of the purchase rights under this Warrant.

     8.   MISCELLANEOUS.

          (a)  ISSUE DATE. The provisions of this Warrant shall be construed
and shall be given effect in all respect as if it had been issued and delivered
by the Company on the date hereof.

                                       3.

<PAGE>   4

This Warrant shall be binding upon any successors or assigns of the Company.
This Warrant shall constitute a contract under the laws of the State of
California and for all purposes shall be construed in accordance with and
governed by the laws of said state.

     (b)  RESTRICTIONS. The holder hereof acknowledges that the shares acquired
upon the exercise of this Warrant may have restrictions upon its resale imposed
by state and federal securities laws.

     (c)  WAIVERS AND AMENDMENTS. This Warrant and any provisions hereof may be
changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought.

     (d)  ASSIGNMENT AND TRANSFERABILITY. This Warrant may not be assigned or
transferred without the prior written approval of the Company. Following an
assignment, the Company shall, without charge, execute and deliver a new
Warrant or Warrants dated as of the date hereof and registered in the name of
the assignee or assignees named in such instrument of assignment (any such
assignee will then be a "holder" for purposes of this Warrant) and, if holder's
entire interest is not being assigned, in the name of holder, and this Warrant
shall promptly be canceled.

     (e)  MARKET STAND OFF. The undersigned holder of this Warrant hereby
agrees that,for a period of 180 days following the effective date of a
registration statement of the Company for its initial public offering filed
pursuant to the Securities Act of 1933, it shall not to the extent requested by
the Company and its underwriter sell or otherwise transfer or dispose of (other
than to donees who agree to be similarly bound) any Common Stock received upon
exercise of this Warrant. The undersigned holder of this Warrant further agrees
to enter into an agreement with the Company's underwriter for its initial
public offering which evidences the foregoing covenant. In order to enforce the
foregoing covenants, the Company may impose stop-transfer instructions with its
transfer agent.

                                       4.
<PAGE>   5

     IN WITNESS WHEREOF, the undersigned have caused this Warrant to be executed
by its officers thereunto duly authorized.

Originally dated: October 30, 1997

Re-issued: September 1, 1999

                                        VIROLOGIC, INC.
--------------------------

By:                                     By: /s/ MARTIN H. GOLDSTEIN
    ---------------------------------       ---------------------------------

Title:                                  Title: Pres & CEO
        -----------------------------          ------------------------------

Address:                                Address: 270 E. Grand Ave.
         ----------------------------            ----------------------------

                                                 S. San Francisco, CA 94080
         ----------------------------            ----------------------------

                                       5.
<PAGE>   6

                               NOTICE OF EXERCISE

To:
   ---------------------------

     1.   The undersigned hereby elects to purchase ________ shares of Series A
Preferred Stock of Virologic, Inc. pursuant to the terms of the attached
Warrant, and tenders herewith payment of the purchase price in full, together
with all applicable transfer taxes, if any.

     2.   Please issue a certificate of certificates representing said shares
of Series A Preferred Stock in the name of the undersigned as is specified
below:

                         -----------------------------
                                     (Name)

                         -----------------------------
                                   (Address)

     3.   The undersigned represents that the aforesaid shares are being
acquired for the account of the undersigned for investment and not with a view
to, or for resale in connection with, the distribution thereof and that the
undersigned has no present intention of distributing or reselling such shares.

-------------------------------------   ------------------------------------
(Date)                                  (Signature)

                                       1.<PAGE>   1
                                                                    EXHIBIT 4.11

                                    WARRANT

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933. SUCH SECURITIES AND ANY SECURITIES OR SHARES ISSUED HEREUNDER MAY
NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION
THEREFROM UNDER SAID ACT. COPIES OF THE AGREEMENT COVERING THE PURCHASE OF THESE
SECURITIES AND RESTRICTING THEIR TRANSFER OR SALE MAY BE OBTAINED AT NO COST BY
WRITTEN REQUEST MADE BY THE HOLDER OF RECORD HEREOF TO THE SECRETARY OF THE
COMPANY AT ITS PRINCIPAL EXECUTIVE OFFICES.

No.  WB-__                                    Warrant to Purchase 301,522 Shares
                                               Series B Preferred Stock (subject
                                                                  to adjustment)

                  WARRANT TO PURCHASE SERIES B PREFERRED STOCK

                                       OF

                                 VIROLOGIC, INC.

                           VOID AFTER AUGUST 30, 2003

        This certifies that, for value received, ___________________, or
registered assigns ("Holder") is entitled, subject to the terms set forth below,
to purchase from VIROLOGIC, INC. (the "Company"), a Delaware corporation, up to
_______ of the Series B Preferred Stock of the Company, as constituted on August
25, 1998 (the "Warrant Issue Date"), upon surrender hereof, at the principal
office of the Company referred to below, with the subscription form attached
hereto duly executed, and simultaneous payment therefor in lawful money of the
United States or otherwise as hereinafter provided, at the Exercise Price as set
forth in Section 2 below. The number, character and Exercise Price of such
shares of Series B Preferred Stock are subject to adjustment as provided below.
The term "Warrant" as used herein shall include this Warrant, which is one of a
series of warrants issued for the Series B Preferred Stock of the Company, and
any warrants delivered in substitution or exchange therefor as provided herein.

        This Warrant is issued in connection with the transactions described in
that certain Series B Preferred Stock Purchase Agreement between the Company and
the investors described therein, dated as of August 25, 1998 (the "Purchase
Agreement").

        1. TERM OF WARRANT. Subject to the terms and conditions set forth
herein, this warrant shall be exercisable, in whole or in part, during the term
commencing on the Warrant Issue Date and ending at 5:00 p.m., Pacific standard
time, on August 30, 2003, and shall be void thereafter.

        2. EXERCISE PRICE. The Exercise Price at which this Warrant may be
exercised shall be $3.68 per share of Series B Preferred Stock, as adjusted from
time to time pursuant to Section 11 hereof.

        3. VESTING OF WARRANT. Effective as of the Warrant Issue Date, this
Warrant is exercisable with respect to ______ shares of Series B Preferred Stock
of the Company.

                                       1.
<PAGE>   2
        4. EXERCISE OF WARRANT.

               (a) The purchase rights represented by this Warrant are
exercisable by the Holder in whole or in part, at any time, or from time to
time, during the term hereof as described in Section I above, by the surrender
of this Warrant and the Notice of Exercise annexed hereto duly completed and
executed on behalf of the Holder, at the office of the Company (or such other
office or agency of the Company as it may designate by notice in writing to the
Holder at the address of the Holder appearing on the books of the Company), upon
payment (i) in cash or by check acceptable to the Company, (ii) by cancellation
by the Holder of indebtedness of the Company to the Holder, or (iii) by a
combination of (i) and (ii) of the purchase price of the shares to be purchased.

               (b) This Warrant shall be deemed to have been exercised
immediately prior to the close of business on the date of its surrender for
exercise as provided above, and the person entitled to receive the shares of
Series B Preferred Stock issuable upon such exercise shall be treated for all
purposes as the holder of record of such shares as of the close of business on
such date. As promptly as practicable on or after such date and in any event
within ten (10) days thereafter, the Company at its expense shall issue and
deliver to the person or persons entitled to receive the same a certificate or
certificates for the number of shares issuable upon such exercise. In the event
that this Warrant is exercised in part, the Company at its expense will execute
and deliver a new Warrant of like tenor exercisable for the number of shares for
which this Warrant may then be exercised.

               (c) Notwithstanding any provisions herein to the contrary, if the
fair market value of one share of Series B Preferred Stock is greater than the
Exercise Price (at the date of calculation as set forth below), in lieu of
exercising this Warrant for cash, the Holder may elect to receive shares equal
to the value (as determined below) of this Warrant (or the portion thereof being
cancelled) by surrender of this Warrant at the principal office of the Company
together with the properly endorsed Notice of Exercise and notice of such
election in which event the Company shall issue to the Holder a number of shares
of Series B Preferred Stock computed using the following formula:

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

Where   X   =    the number of shares of Series B Preferred Stock to be issued
                 to the Holder

        Y   =    the number of shares of Series B Preferred Stock purchasable
                 under the Warrant or, if only a portion of the Warrant is being
                 exercised, the portion of the Warrant being canceled (at the
                 date of such calculation)

        A   =    the fair market value of one share of the Company's Series B
                 Preferred Stock (at the date of such calculation)

        B   =    Exercise Price (as adjusted to the date of such calculation)

                                       2.
<PAGE>   3
For purposes of the above calculation, fair market value of one share of Series
B Preferred Stock shall be determined by the Company's Board of Directors in
good faith; provided, however, that where there exists a public market for the
Company's Common Stock at the time of such exercise, the fair market value per
share shall be the product of (i) the average of the closing bid and asked
prices of the Common Stock quoted in the Over-The-Counter Market Summary or the
last reported sale price of the common Stock or the closing price quoted on The
Nasdaq National Market or on any exchange on which the Common Stock is fisted,
whichever is applicable, as published in the Western Edition of The Wall Street
Journal for the five (5) trading days prior to the date of determination of fair
market value and (ii) the number of shares of Common Stock into which each share
of Series B Preferred Stock is convertible at the time of such exercise.
Notwithstanding the foregoing, in the event the Warrant is exercised in
connection with the Company's initial public offering of Common Stock, the fair
market value per share shall be the product of (i) the per share offering price
to the public of the Company's initial public offering, and (ii) the number of
shares of Common Stock into which each share of Series B Preferred Stock is
convertible at the time of such exercise.

               (d) No fractional shares or scrip representing fractional shares
shall be issued upon the exercise of this Warrant. In lieu of any fractional
share to which the Holder would otherwise be entitled, the Company shall make a
cash payment equal to the Exercise Price multiplied by such fraction.

        5. REPLACEMENT OF WARRANT

        6. RIGHTS OF STOCKHOLDERS. Subject to Sections 9 and 11 of this Warrant,
the Holder shall not be entitled to vote or receive dividends or be deemed the
holder of the Series B Preferred Stock to which this Warrant relates or any
other securities of the Company that may at any time be issuable on the exercise
hereof for any purpose.

        7. TRANSFER OF WARRANT.

               (a) WARRANT REGISTER. The Company will maintain a register (the
"Warrant Register") containing the names' and addresses of the Holder or
Holders. Any Holder of this Warrant or any portion thereof may change his/her
address as shown on the Warrant Register by written notice to the Company
requesting such change. Any notice or written communication required or
permitted to be given to the Holder may be delivered or given by mail to such
Holder as shown on the Warrant Register and at the address shown on the Warrant
Register. Until this Warrant is transferred on the Warrant Register of the
Company, the Company may treat the Holder as shown on the Warrant Register as
the absolute owner of this Warrant for all purposes, notwithstanding any notice
to the contrary.

               (b) WARRANT AGENT. The Company may, by written notice to the
Holder, appoint an agent for the purpose of maintaining the Warrant Register
referred to in Section 7(a) above, issuing the Series B Preferred Stock or other
securities then issuable upon the exercise of this Warrant, exchanging this
Warrant, replacing this Warrant, or any or all of the foregoing. Thereafter, any
such registration, issuance, exchange, or replacement, as the case may be, shall
be made at the office of such agent.

               (c) TRANSFERABILITY AND NONNEGOTIABILITY OF WARRANT. This Warrant
may not be transferred or assigned (i) except in its entirety (other than
transfers to BB Biotech and its

                                       3.
<PAGE>   4
affiliates) and (ii) without compliance with all applicable federal and state
securities laws by the transferor and the transferee (including the delivery of
investment representation letters reasonably satisfactory to the Company, if
such are requested by the Company), and then only against receipt of an
agreement of the transferee to comply with the provisions of this Section 7(c)
with respect to any resale or other disposition of this Warrant. Subject to the
provisions of this warrant with respect to compliance with the Securities Act of
1933 " as amended (the "Act"), title to this Warrant may be transferred by
endorsement (by the Holder executing the Assignment Form annexed hereto) and
delivery in the same manner as a negotiable instrument transferable by
endorsement and delivery.

               (d) EXCHANGE OF WARRANT UPON A TRANSFER. On surrender of this
Warrant for exchange, properly endorsed on the Assignment Form and subject to
the provisions of this warrant with respect to compliance with the Act and with
the limitations on assignments and transfers and contained in this Section 7,
the Company at its expense shall issue to or on the order of the Holder a new
warrant or warrants of like tenor, in the name of the Holder or as the Holder
(on payment by the Holder of any applicable transfer taxes) may direct, for the
number of shares issuable upon exercise hereof

               (e) COMPLIANCE WITH SECURITIES LAWS.

                      (i) The Holder of this Warrant, by acceptance hereof,
acknowledges that this Warrant and the shares of Series B Preferred Stock or
Common Stock to be issued upon exercise hereof or conversion thereof are being
acquired solely for the Holder's own account and not as a nominee for any other
party, and for investment, and that the Holder will not offer, sell or otherwise
dispose of this Warrant or any shares of Series B Preferred Stock or Common
Stock to be issued upon exercise hereof or conversion thereof except under
circumstances that will not result in a violation of the Act or any state
securities laws. Upon exercise of this Warrant, the Holder shall, if requested
by the Company, confirm in writing, in a form satisfactory to the Company, that
the shares of Series B Preferred Stock or Common Stock so purchased are being
acquired solely for the Holder's own account and not as a nominee for any other
party, for investment, and not with a view toward distribution or resale.

                      (ii) This Warrant and all shares of Series B Preferred
Stock or Common Stock issued upon exercise hereof or conversion thereof shall be
stamped or imprinted with a legend in substantially the following form (in
addition to any legend required by state securities laws):

        THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
        SECURITIES ACT OF 1933. SUCH SECURITIES AND ANY SECURITIES OR SHARES
        ISSUED HEREUNDER MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH
        REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT. COPIES OF THE
        AGREEMENT COVERING THE PURCHASE OF THESE SECURITIES AND RESTRICTING
        THEIR TRANSFER OR SALE MAY BE OBTAINED AT NO COST BY WRITTEN REQUEST
        MADE BY THE HOLDER OF RECORD HEREOF TO THE SECRETARY OF THE COMPANY AT
        ITS PRINCIPAL EXECUTIVE OFFICES.

                                       4.
<PAGE>   5
        8. RESERVATION OF STOCK. The Company covenants that during the term this
Warrant is exercisable, the Company will reserve from its authorized and
unissued Series B Preferred Stock a sufficient number of shares to provide for
the issuance of Series B Preferred Stock upon the exercise of this warrant (and
shares of its Common Stock for issuance on conversion of such Series B Preferred
Stock) and, from time to time, will take all steps necessary to amend its
Certificate of Incorporation (the "Certificate") to provide sufficient reserves
of shares of Series B Preferred Stock issuable upon exercise of the Warrant (and
shares of its Common Stock for issuance on conversion of such Series B Preferred
Stock). The Company further covenants that all shares that may be issued upon
the exercise of rights represented by this Warrant, upon exercise of the rights
represented by this Warrant and payment of the Exercise Price, all as set forth
herein, will be free from all taxes, liens and charges in respect of the issue
thereof (other than taxes in respect of any transfer occurring contemporaneously
or otherwise specified herein). The Company agrees that its issuance of this
Warrant shall constitute full authority to its officers who are charged with the
duty of executing stock certificates to execute and issue the necessary
certificates for shares of Series B Preferred Stock upon the exercise of this
Warrant.

        9. NOTICES.

               (a) Whenever the Exercise Price or number of shares purchasable
hereunder shall be adjusted pursuant to Section 11 hereof, the Company shall
issue a certificate signed by its Chief Financial Officer setting forth, in
reasonable detail, the event requiring the adjustment, the amount of the
adjustment, the method by which such adjustment was calculated, and the Exercise
Price and number of shares purchasable hereunder after giving effect to such
adjustment, and shall cause a copy of such certificate to be mailed (by
first-class mail, postage prepaid) to the Holder of this Warrant.

               (b) In case:

                      (i) the Company shall take a record of the holders of its
Series B Preferred Stock or Common Stock (or other stock or securities at the
time receivable upon the exercise or conversion of this Warrant) for the purpose
of entitling them to receive any dividend or other distribution, or any right to
subscribe for or purchase any shares of stock of any class or any other
securities, or to receive any other right, or

                      (ii) of any public offering of the Company's Common Stock,
any capital reorganization of the Company, any reclassification of the capital
stock of the Company, any consolidation or merger of the Company with or into
another corporation, or any conveyance of all or substantially all of the assets
of the Company to another corporation, or

                      (iii) of any voluntary dissolution, liquidation or
winding-up of the Company, then, and in each such case, the Company will mail or
cause to be mailed to the Holder or Holders a notice specifying, as the case may
be, (A) the date on which a record is to be taken for the purpose of such
dividend, distribution or right, and stating the amount and character of such
dividend, distribution or right, or (B) the date on which such reorganization,
reclassification, consolidation, merger, conveyance, dissolution, liquidation or
winding up is to take place, and the time, if any is to be fixed, as of which
the holders of record of Series B

                                       5.
<PAGE>   6
Preferred Stock or Common Stock (or such stock or securities at the time
receivable upon the exercise of this Warrant) shall be entitled to exchange
their shares of Series B Preferred Stock or Common Stock (or such other stock or
securities) for securities or other property deliverable upon such
reorganization, reclassification, consolidation, merger, conveyance,
dissolution, liquidation or winding up. Such notice shall be mailed at least
fifteen (15) days prior to the date therein specified.

               (c) All such notices, advices and communications shall be deemed
to have been received (i) in the case of personal delivery, on the date of such
delivery and (ii) in the case of mailing, on the third business day following
the date of such mailing.

        10. AMENDMENTS. This Warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of such change, waiver, discharge or termination is
sought.

        11. ADJUSTMENTS. The Exercise Price and the number of shares purchasable
hereunder are subject to adjustment from time to time as follows:

               11.1 CONVERSION OR REDEMPTION OF SERIES B PREFERRED STOCK. Should
all of the Company's Series B Preferred Stock be, or if outstanding would be, at
any time prior to the expiration of this warrant or any portion thereof,
redeemed or converted into shares of the Company's Common Stock in accordance
with Section 4(b) of the Certificate, then this Warrant shall immediately become
exercisable for that number of shares of the Company's Common Stock equal to the
number of shares of the Common Stock that would have been received if this
Warrant had been exercised in full and the Series B Preferred Stock received
thereupon had been simultaneously converted immediately prior to such event, and
the Exercise Price shall be immediately adjusted to equal the quotient obtained
by dividing (x) the aggregate Exercise Price of the maximum number of shares of
Series B Preferred Stock for which this Warrant was exercisable immediately
prior to such conversion or redemption, by (y) the number of shares of Common
Stock for which this Warrant is exercisable immediately after such conversion or
redemption. For purposes of the foregoing, the "Certificate" shall mean the
Certificate of Incorporation of the Company as amended and/or restated and
effective immediately prior to the redemption or conversion of all of the
Company's Series B Preferred Stock.

               11.2 MERGER, SALE OF ASSETS, ETC. If at any time while this
Warrant, or any portion thereof, is outstanding and unexpired there shall be (a)
a reorganization (other than a combination, reclassification, exchange or
subdivision of shares otherwise provided for herein), (b) a merger or
consolidation of the Company with or into another corporation in which the
Company is not the surviving entity, or a reverse triangular merger in which the
Company is the surviving entity but the shares of the Company's capital stock
outstanding immediately prior to the merger are converted by virtue of the
merger into other property, whether in the form of securities, cash or
otherwise, or (c) a sale or transfer of the Company's properties and assets as,
or substantially as, an entirety to any other person, then the Company shall
provide the holder of this Warrant with not less than thirty (30) days, prior
written notice of such event and an opportunity to exercise this Warrant
effective upon the consummation of such event, so that, as a part of such
reorganization, merger, consolidation, sale or transfer, the holder of this
Warrant shall be entitled to receive upon exercise of this Warrant the number of
shares of stock or other

                                       6.
<PAGE>   7
securities or property of the successor corporation resulting from such
reorganization, merger, consolidation, sale or transfer that a holder of the
shares deliverable upon exercise of this Warrant would have been entitled to
receive in such reorganization, consolidation, merger, sale or transfer. The
Company shall not effect any such consolidation, merger, sale, transfer or other
disposition unless prior to or simultaneously with the consummation thereof the
successor corporation (if other than the Company) resulting from such
consolidation or merger, or the corporation purchasing or otherwise acquiring
such assets or other appropriate corporation or entity shall agree to deliver to
the holder of the Warrant, upon its exercise and payment of the Exercise Price
then in effect, such shares of stock, securities or assets as, in accordance
with the foregoing provisions, such holder may be entitled to purchase.

               11.3 RECLASSIFICATION, ETC. If the Company, at any time while
this Warrant, or any portion thereof, remains outstanding and unexpired, by
reclassification of securities or otherwise, shall change any of the securities
as to which purchase rights under this Warrant exist into the same or a
different number of securities of any other class or classes, this Warrant shall
thereafter represent the right to acquire such number and kind of securities as
would have been issuable as the result of such change with respect to the
securities that were subject to the purchase rights under this Warrant
immediately prior to such reclassification or other change and the Exercise
Price therefor shall be appropriately adjusted, all subject to further
adjustments as provided in this Section 11. No adjustment shall be made pursuant
to this Section 11.3, upon any conversion or redemption of the Series B
Preferred Stock which is the subject of Section 11.1.

               11.4 SPLIT, SUBDIVISION OR COMBINATION OF SHARES. If the Company
at any time while this Warrant, or any portion thereof, remains outstanding and
unexpired shall split, subdivide or combine the securities as to which purchase
rights under this warrant exist, into a different number of securities of the
same class, the Exercise Price for such securities shall be proportionately
decreased in the case of a split or subdivision or proportionately increased in
the case of a combination.

               11.5 ADJUSTMENTS FOR DIVIDENDS IN STOCK OR OTHER SECURITIES OR
PROPERTY. If while this Warrant, or any portion hereof, remains outstanding and
unexpired the holders of the securities as to which purchase rights under this
Warrant exist at the time shall have received, or, on or after the record date
fixed for the determination of eligible Stockholders, shall have become entitled
to receive, without payment therefor, other or additional stock or other
securities or property (other than cash) of the Company by way of dividend, then
and in each case, this Warrant shall represent the right to acquire, in addition
to the number of shares of the security receivable upon exercise of this
Warrant, and without payment of any additional consideration therefor, the
amount of such other or additional stock or other securities or property (other
than cash) of the Company that such holder would hold on the date of such
exercise had it been the holder of record of the security receivable upon
exercise of this Warrant on the date hereof and had thereafter, during the
period from the date hereof to and including the date of such exercise, retained
such shares and/or all other additional stock available by it as aforesaid
during such period, giving effect to all adjustments called for during such
period by the provisions of this Section 11.

               11.6 CERTIFICATE AS TO ADJUSTMENTS. Upon the occurrence of each
adjustment or readjustment pursuant to this Section 11, the Company at its
expense shall promptly compute

                                       7.
<PAGE>   8
such adjustment or readjustment in accordance with the terms hereof and furnish
to each Holder of this Warrant a certificate setting forth such adjustment or
readjustment and showing in detail the facts upon which such adjustment or
readjustment is based. The Company shall, upon the written request, at any time,
of any such Holder, furnish or cause to be furnished to such Holder a like
certificate setting forth: (a) such adjustments and readjustments; (b) the
Exercise Price at the time in effect; and (c) the number of shares and the
amount, if any, of other property that at the time would be received upon the
exercise of the Warrant.

               11.7 NO IMPAIRMENT. The Company will not, by any voluntary
action, avoid or seek to avoid the observance or performance of any of the terms
to be observed or performed hereunder by the Company, but will at all times in
good faith assist in the carrying out of ail the provisions of this Section 11
and in the taking of all such action as may be necessary or appropriate in order
to protect the rights of the Holders of this Warrant against impairment.

        12. REGISTRATION RIGHTS. Upon exercise of this Warrant, the Holder shall
have and be entitled to exercise, together with all other holders of Registrable
Securities possessing registration rights under that certain Investors" Rights
Agreement, of even date herewith, between the Company and the parties who have
executed the counterpart signature pages thereto or are otherwise bound thereby
(the "Investors' Rights Agreement"), the rights of registration granted under
the Investors' Rights Agreement to Registrable Securities (with respect to the
Shares issued on exercise of this Warrant). By its receipt of this Warrant,
Holder agrees to be bound by the Investors' Rights Agreement upon exercise of
this warrant as a party thereto.

        13. MISCELLANEOUS.

               (a) SUCCESSORS. All the covenants and provisions hereof by or for
the benefit of the Company or the Holder shall bind and inure to the benefit of
their respective successors and assigns hereunder.

               (b) GOVERNING LAW. This Warrant shall be deemed to be a contract
made under the laws of the State of California and for all purposes shall be
construed in accordance with the laws of said State.

               (c) ATTORNEYS FEES IN THE EVENT OF A DISPUTE. In the event of any
action at law, suit in equity or arbitration proceeding in relation to this
Warrant or any Series B Preferred Stock issued or to be issued hereunder, the
prevailing party or parties, shall be paid by the other party or parties a
reasonable sum for attorneys, fees and expenses of such prevailing party or
parties.

               (d) SATURDAYS, SUNDAYS, HOLIDAYS. 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 a Sunday or shall be a legal holiday in the State
of California, then such action may be taken or such right may be exercised on
the next succeeding day not a legal holiday.

                                       8.
<PAGE>   9
        IN WITNESS WHEREOF, Virologic, Inc. has caused this Warrant to be
executed by its officers thereunto duly authorized.

        Dated: August 25, 1998.

                                       VIROLOGIC, INC.

                                       By
                                         ---------------------------------------
                                         President and CEO
        HOLDER:

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

                                       9.
<PAGE>   10

                               NOTICE OF EXERCISE

TO: VIROLOGIC, INC.

        (1) The undersigned hereby elects to purchase shares of Series B
Preferred Stock of VIROLOGIC INC., pursuant to the terms of the attached
Warrant, and tenders herewith payment of the purchase price for such shares in
full.

        (2) In exercising this Warrant, the undersigned hereby confirms and
acknowledges that the shares of Series B Preferred Stock or the Common Stock to
be issued upon conversion thereof are being acquired solely for the account of
the undersigned and not as a nominee for any other party, or for investment, and
that the undersigned will not offer, sell or otherwise dispose of any such
shares of Series B Preferred Stock or Common Stock except under circumstances
that will not result in a violation of the Securities Act of 1933, as amended,
or any state securities laws.

        (3) Please issue a certificate or certificates representing said shares
of Series B Preferred Stock in the name of the undersigned or in such other name
as is specified below:

                                       -----------------------------------------
                                                          (Name)

                                       -----------------------------------------
                                                          (Name)

        (4) Please issue a new Warrant for the unexercised portion of the
attached Warrant in the name of the undersigned or in such other name as is
specified below:

                                       -----------------------------------------
                                                          (Name)

---------------------------------      -----------------------------------------
              Date                                     (Signature)

                                      10.
<PAGE>   11
                                 ASSIGNMENT FORM

        FOR VALUE RECEIVED, the undersigned registered owner of this Warrant
hereby sells, assigns and transfers unto the Assignee named below all of the
rights of the undersigned under the within Warrant, with respect to the number
of shares of Series B Preferred Stock (or Common Stock) set forth below:

<TABLE>
<CAPTION>
   Name of Assignee                  Address                      No. of Shares
   ----------------                  -------                      -------------
<S>                                  <C>                          <C>
</TABLE>

and does hereby irrevocably constitute and appoint Attorney to make such
transfer on the books of VIROLOGIC, INC., maintained for the purpose, with full
power of substitution in the premises.

        The undersigned also represents that, by assignment hereof, the Assignee
acknowledges that this warrant and the shares of stock to be issued upon
exercise hereof or conversion thereof are being acquired for investment and that
the Assignee will not offer, sell or otherwise dispose of this warrant or any
shares of stock to be issued upon exercise hereof or conversion thereof except
under circumstances which will not result in a violation of the Securities Act
of 1933, as amended, or any state securities laws. Further, the Assignee has
acknowledged that upon exercise of this Warrant, the Assignee shall, if
requested by the Company, confirm in writing, in a form satisfactory to the
Company, that the shares of stock so purchased are being acquired for investment
and not with a view toward distribution or resale.

        Dated:

                                       -----------------------------------------
                                                    Signature of Holder

                                      11.

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