AVIRON
EXHIBIT 10.52
<DOCUMENT>
<TYPE>EX-10.52
<SEQUENCE>3
<FILENAME>f71770ex10-52.txt
<DESCRIPTION>EXHIBIT 10.52
<TEXT>

<PAGE>   1
                                                                  Exhibit 10.52

                   AMENDMENT NO. 2 TO STOCK TRANSFER AGREEMENT

     THIS AMENDMENT NO. 2 TO STOCK TRANSFER AGREEMENT entered into as of the 29
day of March, 2001, by and among AVIRON, a Delaware corporation ("Company") and
the REGENTS OF THE UNIVERSITY OF MICHIGAN ("University").

                                    RECITALS

     WHEREAS, the Company and the University are parties to that certain
Materials Transfer and Intellectual Property Agreement dated February 24, 1995
and that certain Stock Transfer Agreement dated February 24, 1995, as amended by
Amendment No. 1 to Stock Transfer Agreement, dated February 16, 2000 (the
"Transfer Agreement").

     WHEREAS, pursuant to Section 5 of the Transfer Agreement, Aviron agreed to
deliver to the University a warrant for the purchase of Aviron Common Stock
equal to one and twenty-five one-hundredths percent (1.25%) of the total number
of issued and outstanding shares of the Company's Common Stock on the Issue Date
(as defined therein).

     WHEREAS, the parties amended the Transfer Agreement to allow for the
issuance of a warrant as of February, 2000 and amended the calculation of the
number of shares to be issued pursuant to the further warrant to be issued to
the University on the Issue Date as defined therein.

     WHEREAS, the parties now desire to amend the Transfer Agreement for a
second time, in order to issue a warrant as of the date hereof and further amend
the calculation of the number of shares to be issued pursuant to the University
on the Issue Date as set forth below.

     NOW, THEREFORE, in consideration of the promises and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties agree as follows:

SECTION 1. ISSUANCE OF WARRANT.

     1.1  Promptly upon execution of this Agreement, the Company will issue to
University a warrant to purchase fifty thousand (50,000) shares of the Company
Common Stock at an exercise price per share of Ten Dollars ($10.00) (the
"Initial Exercise Price" and the "Second Warrant"). The Second Warrant shall be
in substantially the form as the warrant issued to University in February 2000
pursuant to the Transfer Agreement.

     1.2  The Company represents and warrants that the Initial Exercise Price is
properly calculated according to Section 5.3 of the Transfer Agreement.

<PAGE>   2

     1.3  In the event that the calculation of the Warrant Shares (as defined in
the Transfer Agreement and as amended below), is negative or zero, then
University shall retain the Second Warrant and there shall be no adjustment of
the number of shares exercisable under the Second Warrant.

     1.4  If University exercises/converts the New Warrant and Second Warrant in
full or portion prior to the date of the First Commercial Sale of any Product
(as defined in the Transfer Agreement) and is not able to sell the Warrant
Shares pursuant to Rule 144 under the Securities Act of 1933, as amended, then
the Company agrees to apply for registration of the Warrant Shares (this
agreement is for one such registration) for resale on a Form S-3 Registration
Statement (if such form is available for use by the Company) with the Securities
and Exchange Commission and both parties agree that such registration shall be
on terms and conditions substantially similar to those registration rights
granted to American Home Products Corporation pursuant to Section 5 of that
certain Common Stock Purchase Agreement by and between American Home Products
Corporation and the Company dated February 3, 2000.

SECTION 2. AMENDMENT OF CALCULATION FOR FURTHER ISSUANCE OF WARRANT.

     2.1  The first-paragraph of Section 5.2 of the Transfer Agreement is
further amended in its entirety as follows:

     "Subject to the provisions of Section 5.4 below, the Warrant shall be
     exercisable for a number of shares of the Company Common Stock (the
     "Warrant Shares") equal to one and twenty-five one-hundredths percent
     (1.25%) of the total number of issued and outstanding shares of the Company
     Common Stock on the Issue Date (including, on an as-converted basis,
     outstanding shares of Preferred Stock of the Company) less three hundred
     ninety thousand (390,000) shares of the Company Common Stock (as adjusted
     for recapitalizations, stock splits, dividends and the like). If such
     number is negative or zero, then no Warrant shall be issued. For purposes
     of calculating this percentage, "issued and outstanding shares of the
     Company Common Stock" shall NOT include shares of the Company Common Stock,
     or securities convertible into the Company Common Stock:"

     In Witness Whereof, the parties hereto have executed this AMENDMENT NO. 2
TO STOCK TRANSFER AGREEMENT as of the date set forth in the first paragraph
hereof.

AVIRON                                 THE REGENTS OF THE
                                       UNIVERSITY OF MICHIGAN


By:    /s/ Fred Kurland                By: /s/ Norman G. Herbert
     --------------------------            --------------------------
                                           Norman G. Herbert
                                           Associate Vice President & Treasurer


                                       By: /s/ L. Erik Lundberg
                                           --------------------------
                                           L. Erik Lundberg, CFA
                                           Chief Investment Officer

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