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                                                                    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.

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      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.
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     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.


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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.
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     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.
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                               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.