EXHIBIT 10.23

FIRST AMENDMENT
 
TO
 
TRANSITION AGREEMENT
 

WHEREAS, a transition agreement (the “Agreement”) was entered into, effective as
of August 10, 2005, between Genentech, Inc., One DNA Way, South San Francisco,
CA 94080, and Myrtle Potter;

WHEREAS, Section 6 of the Agreement provides that the parties to the Agreement
are to cooperate diligently and in good faith to take action to prevent the
imposition of penalties under Section 409A of the Internal Revenue Code
(“Section 409A Penalties”); and

WHEREAS, the parties have decided to amend the Agreement as contemplated by
Section 6 of the Agreement in order to avoid the imposition of Section 409A
Penalties;

WHEREAS, the parties understand that further action, or amendments to the
Agreement, may need to be made to avoid Section 409A Penalties as provided in
Section 6 of the Agreement;

NOW, THEREFORE, the Agreement is hereby, amended effective August 10, 2005, as
follows:

I.

     Section 5 is amended as follows:

    A. The second paragraph of Section 5 is amended to read as follows:

Potter’s currently outstanding stock options granted to her under Genentech’s
1999 Stock Plan during the course of her employment will continue to vest and be
exercisable during her term as a consultant in the same manner as they were
during her employment. The stock options will cease to vest when her consultancy
ends either at the end of its term as set forth in Section 1 above or upon its
earlier termination as set forth in Section 1 above. Potter’s options granted on
or after September 12, 2002 that are or become vested and exercisable shall be
exercised in a cashless exercise in accordance with their terms as follows: All
options granted on or after September 12, 2002 that become vested and
exercisable on or after January 2, 2006 shall be exercised on January 2, 2006 or
the first trading day thereafter. Options granted on or after September 12, 2002
that are not vested and exercisable on January 2, 2006 shall be exercised on the
first trading day after the date they first become vested and exercisable. For
illustration, a schedule showing, with respect to options granted on or after
September 12, 2002, exercise dates and

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number of options to be exercised is attached hereto as Exhibit A. Potter’s
options granted prior to September 12, 2002 are the subject of a property
settlement incident to divorce and will be exercised at the direction of James
Potter pursuant to such settlement.

    B. The following sentence is added to the end of last paragraph of Section
5:

Notwithstanding the foregoing, Potter shall be paid her accrued SERP benefit
with Genentech in a lump sum cash payment on February 13, 2006.

II.

The first paragraph of Section 6 is amended by adding the following sentence to
the end thereof:

Notwithstanding the foregoing provisions of this paragraph, in lieu of any and
all information technology support and security services to be provided as
described above after March 16, 2006, commencing on March 16, 2006, Genentech
will instead provide to Potter during the term of her consultancy a monthly
payment equal to fifty dollars ($50.00) payable March 16, 2006 and the 16th day
of each subsequent month for the remainder of the term of the consulting
relationship (with any payments for partial months to be prorated
appropriately); provided that in the event the cost of such services to Potter
exceeds $350.00 in the aggregate, Potter may request in advance that Genentech
pay such excess. If Genentech approves Potter’s request, Genentech shall
promptly pay Potter such excess.

III.

The following sentence is added to the end of Section 12:

Notwithstanding the foregoing, any reimbursements for attorney’s fees and
related costs incurred by Potter will be made on or before March 15, 2006.

IV.

A new Exhibit A - Option Exercise Plan - is added to the end of the Agreement to
read as provided in the attachment hereto.

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V.

Except as otherwise provided herein, the Agreement shall remain in full force
and effect.

This First Amendment to the Agreement may be executed in separate counterparts
that together constitute one instrument.

     
GENENTECH, INC.
           
By:
/s/ STEPHEN JUELSGAARD
       
Stephen Juelsgaard
               
Date:
  December 28, 2005
                         
MYRTLE POTTER
               
/s/ MYRTLE POTTER
               
Date:
  December 29, 2005

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