<PAGE>   1
                                                                   EXHIBIT 10.42




                                    SUBLEASE


                                     BETWEEN


                            LUCENT TECHNOLOGIES INC.,

                                   SUBLANDLORD



                                       and


                                   AVIGEN INC.

                                    SUBTENANT




                  1201 Harbor Bay Parkway, Alameda, California





                             Dated: February 1, 2000

<PAGE>   2

                                     * * * *


        The mailing, delivery or negotiation of this Sublease shall not be
deemed an offer to enter into any transaction or to enter into any other
relationship, whether on the terms contained herein or on any other terms. This
Sublease shall not be binding nor shall either party have any obligations or
liabilities or any rights with respect thereto, or with respect to the premises,
unless and until both parties have executed and delivered this Sublease and the
Prime Landlord has consented in writing to this Sublease. Until such execution
and delivery of, and consent to this Sublease, either party may terminate all
negotiation and discussion of the subject matter hereof, without cause and for
any reason, without recourse or liability.

                                     * * * *

<PAGE>   3

                                Table of Contents


<TABLE>
<CAPTION>
                                                                                Page
                                                                                ----
<S>                                                                             <C>
1.  SUBLEASE.......................................................................2

2.  PARKING........................................................................3

3.  PRIME LEASE....................................................................3

4.  DEFINITIONS....................................................................6

5.  PRIME LANDLORD.................................................................6

6.  TERM...........................................................................7

7.  RENT/SECURITY DEPOSIT..........................................................8

8.  Intentionally Deleted.........................................................11

9.  Intentionally Deleted.........................................................11

10.  USE AND CONDITION OF SUBLEASED PREMISES......................................11

11.  ALTERATIONS..................................................................14

12.  REPAIRS AND MAINTENANCE......................................................17

13.  UTILITIES AND SERVICES.......................................................17

14.  ASSIGNMENT AND SUBLEASING....................................................18

15.  INSURANCE....................................................................18

16.  SIGNS - BUILDING DIRECTORY...................................................19

17.  COMPLIANCE WITH LAWS.........................................................19

18.  NON-BINDING MEDIATION........................................................22

19.  ESTOPPEL CERTIFICATES........................................................23

20.  SUBORDINATION................................................................24

21.  CASUALTY AND CONDEMNATION....................................................24

22.  CONSENT OR APPROVAL OF PRIME LANDLORD........................................24
</TABLE>



                                      (i)
<PAGE>   4

<TABLE>
<CAPTION>
                                                                                Page
                                                                                ----
<S>                                                                             <C>
23.  NOTICES......................................................................25

24.  BROKERS......................................................................26

25.  SUBLANDLORD'S AND SUBTENANT'S POWER TO EXECUTE...............................26

26.  CONSENT TO SUBLEASE BY PRIME LANDLORD........................................26

27.  HOLDOVER.....................................................................27

28.  DEFAULT AND REMEDIES.........................................................27

29.  ENTIRE AGREEMENT.............................................................29

30.  TABLE OF CONTENTS - CAPTIONS.................................................29

EXHIBIT A    Description of Subleased Premises....................................

EXHIBIT B    Intentionally Deleted................................................

EXHIBIT C    Prime Lease..........................................................
</TABLE>



                                      (ii)
<PAGE>   5

                                    SUBLEASE

        This Sublease is dated for reference purposes as of this 1st day of
February, 2000 and entered into by and between LUCENT TECHNOLOGIES INC., a
Delaware corporation, with offices at 475 South Street, Morristown, New Jersey
07962, (hereinafter "Sublandlord") and AVIGEN, INC., a Delaware corporation,
with offices at 1201 Harbor Bay Parkway, Suite 1000, Alameda, California 94502
(hereinafter "Subtenant").

                             INTRODUCTORY STATEMENTS

        A. By Lease dated June 1, 1998 (the "Prime Lease") ARE-1201 HARBOR BAY,
LLC, a Delaware limited liability company (the "Prime Landlord") leased to
ASCEND COMMUNICATIONS, INC., a Delaware corporation ("Ascend"), certain portions
of the building located at 1201 Harbor Bay Parkway, Alameda, California
(hereinafter called the "Building").

        B. Sublandlord acquired Ascend on January 12, 1999 and was assigned all
of Ascend's rights and benefits under the Prime Lease as part of the
acquisition.

        C. Sublandlord has agreed to sublet to, and Subtenant has agreed to
sublet from Sublandlord, certain portions of the Building.



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<PAGE>   6

        D. The parties desire to enter into this Sublease defining their
respective rights, duties and liabilities relating to the Subleased Premises
(defined below).

                                   WITNESSETH

        NOW THEREFORE, Sublandlord and Subtenant, in consideration of the mutual
promises and covenants contained herein and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, and
each with intent to be legally bound, for themselves and their respective
successors and assigns, agree as follows:

        1.     SUBLEASE

        Sublandlord, for and in consideration of the Subtenant's payment of the
rent and performance of the covenants contained in this Sublease, does hereby
demise and lease to Subtenant, on the dates set forth below, the following
portions of the Building:

<TABLE>
<CAPTION>
        Date                                Portion of Building
        ----                                -------------------
<S>                                         <C>
        Phase I                             15,348 square feet of Suite 150 of
        Commencement Date:                  the Building, as shown on the floor
        (as defined below)                  plan which is attached hereto as Exhibit A,
                                            referred to hereinafter as "Phase I"

        Phase II                            7,000 square feet of Suite 150 of
        Commencement Date:                  the Building, as shown on the floor
</TABLE>



                                     - 2 -
<PAGE>   7

<TABLE>
<S>                                         <C>
        (as defined below)                  plan which is attached hereto as Exhibit A,
                                            referred to hereinafter as "Phase II"
</TABLE>

The term "Subleased Premises" as used hereinafter shall refer to Phase I until
the Phase II Commencement Date, after which date the term "Subleased Premises"
shall refer to both Phase I and Phase II. Subtenant shall have the non-exclusive
right to use all Common Areas as defined and depicted in the Prime Lease during
the term of this Sublease.

        The restrooms serving Phase I and Phase II are located in Phase I.
Subtenant agrees that until the Phase II Commencement Date Sublandlord and its
employees and agents shall at all times have unrestricted access through Phase I
in order to use these restrooms. Phase I and Phase II combined, represent all of
the space that Sublandlord leases pursuant to the Prime Lease.

        2.     PARKING

        Subtenant shall be entitled to use three and one half parking spaces per
one thousand rentable square feet of space (3.5/1,000 rsf) without additional
charge in the Common Areas. Subtenant acknowledges that its right to use the
parking spaces located in the Common Area is on a non-exclusive and non-reserved
basis.



                                     - 3 -
<PAGE>   8

        3.     PRIME LEASE

        (a) A true copy of the Prime Lease is attached hereto as Exhibit C. For
purposes of this Sublease, the term "Prime Lease" shall include the lease
amendments contained in the Consent to Sublease dated as of February 10, 2000
among Prime Landlord, Sublandlord and Subtenant (the "Consent to Sublease").
Where not expressly inconsistent with the terms hereof, this Sublease shall be
subject and subordinate to all of the terms and conditions contained in the
Prime Lease as said terms and conditions affect the Subleased Premises, and all
of the terms and conditions of the Prime Lease, except as otherwise set forth
herein, are hereby incorporated into this Sublease and shall be binding upon
Subtenant and Sublandlord with respect to the Subleased Premises to the same
extent as if Subtenant were named as tenant and Sublandlord to the same extent
as if Sublandlord were named as landlord under the Prime Lease. For purposes of
this Sublease, references in the Prime Lease to the "Term" shall mean the Term
of this Sublease and references to the "Demised Premises" in the Prime Lease
shall mean the Subleased Premises. Upon the expiration or earlier termination of
the Prime Lease, this Sublease and Subtenant's right to use and occupy the
Subleased Premises shall immediately terminate. Except as otherwise provided
herein, when any fraction, factor or formula, which is based on the number of
square feet leased, is expressed in the Prime Lease, it will be adjusted by
substituting the number of



                                     - 4 -
<PAGE>   9

square feet of the Subleased Premises for the number of square feet of the
Demised Premises leased in the Prime Lease.

        (b) Subtenant agrees that it shall not do or omit to do anything which
would result in a default under the Prime Lease, and Subtenant agrees to
indemnify, defend and hold Sublandlord, its officers, directors, employees and
agents, and each of their respective successors and assigns, harmless from and
against all claims, demands or liabilities resulting from Subtenant's breach,
violation or nonperformance of any of provisions of the Prime Lease, as
incorporated herein. With the exceptions set forth herein, Subtenant shall be
entitled to all of the rights and privileges of the Sublandlord as tenant under
the terms of the Prime Lease with respect to the Subleased Premises. The
following provisions of the Prime Lease shall not be incorporated into this
Sublease: Sections 1.1 (except 1.1.1, 1.1.2 and 1.1.5), 1.2, 3, 4, 5, 6, 7, 8,
9, 11, 22, 23, 28 and 42, Right to Extend Addendum, and Exhibits B, D and F.
Additionally, references in the following sections to Landlord shall be deemed
to refer to Prime Landlord only: 30.1, 30.2, 31, 33 and 35.

        (c) Sublandlord represents to Subtenant that the Prime Lease is in full
force and effect, and that no default or event that, with the passing of time or
the giving of notice or both, would constitute a default, exists on the part of
Sublandlord, or, to Sublandlord's knowledge, the Prime Landlord. Sublandlord
agrees to maintain the Prime Lease in full force and effect,



                                     - 5 -
<PAGE>   10

except to the extent that any failure to maintain the Prime Lease is due to the
failure of Subtenant to comply with any of its obligations under this Sublease.
Sublandlord shall not amend or modify the Prime Lease in such a manner as to
materially adversely affect Subtenant's use of the Subleased Premises or
increase the obligations or decrease the rights of Subtenant hereunder, without
the prior written consent of Subtenant, which may be granted or withheld at
Subtenant's sole discretion.

        4.     DEFINITIONS

        All terms not expressly defined in this Sublease shall have the meanings
given to them in the Prime Lease.

        5.     PRIME LANDLORD

        Subtenant agrees to look solely to the Prime Landlord, and not to
Sublandlord, for the performance of services and obligations which are the
obligations of Prime Landlord under the Prime Lease with respect to the
Subleased Premises. At Subtenant's expense and written request, Sublandlord
will, at its election, either (i) exercise commercially reasonable efforts, at
Subtenant's sole cost and expense, to cause Prime Landlord to perform such
obligations, or (ii) assign its rights to enforce the terms of the Prime Lease
against Prime Landlord to Subtenant such that Subtenant can pursue enforcement
efforts directly against Prime Landlord (the matters discussed in clauses (i)
and (ii) being "Enforcement Efforts"). Provided that Sublandlord undertakes
Enforcement Efforts, Subtenant hereby releases



                                     - 6 -
<PAGE>   11

Sublandlord from any and all loss, cost, expense, liability, claims or causes of
action that Subtenant may have or hereafter acquire against Sublandlord as a
result of the failure of Prime Landlord to perform any services or obligations
that it is obligated to perform under the Prime Lease.

        6.     TERM

        The term of this Sublease (the "Term") shall commence on the dates set
forth below and shall end, as to both Phase I and Phase II, on June 30, 2003
(the "Expiration Date"):

<TABLE>
<CAPTION>
        Phase                               Phase Commencement Date
        -----                               -----------------------
<S>                                         <C>
        Phase I                             Approximately February 1, 2000

        Phase II                            Approximately August 1, 2000.
</TABLE>

The "Phase I Commencement Date" and the "Phase II Commencement Date" shall occur
when Sublandlord has delivered exclusive possession of Phase I and Phase II,
respectively, to Subtenant in the condition required under this Sublease. The
commencement dates for Phase I and Phase II set forth above are approximate
dates and Sublandlord shall not be subject to any liability to Subtenant, nor
shall Subtenant be entitled to terminate this Sublease, if it fails to deliver
possession of the Subleased Premises to Subtenant on the approximate dates set
forth above.



                                     - 7 -
<PAGE>   12

Notwithstanding anything to the contrary contained herein, if the Phase I
Commencement Date, or the Phase II Commencement Date have not occurred before
April 1, 2000 and October 1, 2000, then Subtenant shall have the right
thereafter to cancel this Sublease with respect to such Phase I and/or Phase II
space, and upon such cancellation, Sublandlord shall return all sums theretofore
deposited or prepaid by Subtenant to Sublandlord, and neither party shall have
any further liability to the other.

        7.     RENT/SECURITY DEPOSIT

        a. The basic rent ("Monthly Basic Rent") during the Term hereunder shall
be as set forth below:

<TABLE>
<CAPTION>
        Months                              Monthly Basic Rent
        ------                              ------------------
<S>                                         <C>
        Phase I Commencement Date -
        the day immediately preceding
        the Phase II Commencement Date
        (anticipated to be 07/31/00)           $14,580.80

        Phase II Commencement Date
        (anticipated to be 08/01/00) -
        02/09/01                               $21,230.60

        02/10/01 - 06/30/03                    $23,465.40
</TABLE>

The Monthly Basic Rent shall be payable in lawful money of the United States of
America, in advance on the first day of each calendar month during the Term,
except that a proportionately lesser sum may be paid for the first and last
months of the Term of this Sublease if the Term commences on a date other than
the first day of the month or ends on other than the last day of a month.
Subtenant shall pay Sublandlord, concurrently with the



                                     - 8 -
<PAGE>   13

execution of this Sublease, the sum of $14,680.80, which represents the Monthly
Basic Rent due for the first month of the Term of this Sublease. If the Phase I
Commencement Date occurs on other than the first day of a month, then the
$14,680.80 shall be credited to the partial Monthly Basic Rent due for the first
month of the Term and the unapplied balance shall be credited against Monthly
Basic Rent due for the following month.

        b. In addition to the Monthly Basic Rent set forth in section 7.a.
above, Subtenant shall pay Sublandlord (as and when due under the terms of the
Prime Lease), as additional rent, all Operating Expenses, as such term is
defined in the Prime Lease, due with respect to the Subleased Premises.
Operating Expenses shall include, without limitation, property taxes and
assessments, landscaping, property management, parking lot, roof, foundation and
building maintenance, mechanical, fire system monitoring, pest control, Common
Area utilities, and property, liability and, if carried by Master Landlord,
earthquake, insurance. Until the Phase II Commencement Date, Subtenant shall
only be obligated to pay to Sublandlord that portion of the Operating Expenses
allocable to Phase I (based on the relative square footage of Phase I and Phase
II). Following the occurrence of the Phase II Commencement Date, Subtenant shall
pay all Operating Expenses due under the Prime Lease.

        c. The terms "Monthly Basic Rent" and "additional rent" are sometimes
referred to herein as "Rent" or "rent" and shall



                                     - 9 -
<PAGE>   14

include all sums due from Subtenant to Sublandlord under the terms of this
Sublease. All Rent shall be payable at the office of the Sublandlord at the
following address:

                            Lucent Technologies Inc.
                                475 South Street
                          Morristown, New Jersey 07962
                         Attention: Lease Administration

or at such other address as directed by notice from Sublandlord to Subtenant.

        d. Subtenant shall pay to Sublandlord, concurrently with the execution
of this Sublease and in lawful money of the United States of America, a security
deposit ("Security Deposit") in the amount of $93,861.60 for the full and
faithful performance of Subtenant's obligations under this Sublease. If at any
time during the term of this Sublease, Subtenant shall be in default in the
payment of Rent or in the performance of any other obligation under this
Sublease, Sublandlord may use, apply or retain all or part of the Security
Deposit for payment of any amount due Sublandlord or to cure such default or to
compensate Sublandlord for any liability, loss, cost, expense or damage
(including attorney's fees) which Sublandlord may suffer or incur by reason of
Subtenant's defaults. If Sublandlord uses or applies all or any part of the
Security Deposit, Subtenant shall, within ten (10) business days of demand, pay
to Sublandlord a sum sufficient to restore the Security Deposit to the full
amount required by this Sublease. Sublandlord shall have no obligation



                                     - 10 -
<PAGE>   15

to segregate the Security Deposit from its general funds or to pay interest in
respect thereof. No part of the Security Deposit shall be considered to be held
in trust, or to be prepayment of any monies to be paid by Subtenant under this
Sublease. If Subtenant performs all of its obligations hereunder, the Security
Deposit or such portion thereof as had not theretofore been applied by
Sublandlord, shall be returned to Subtenant within fifteen (15) days after the
expiration of the term hereof or after Subtenant has vacated the Subleased
Premises, whichever is later.

        8.     Intentionally Deleted.

        9.     Intentionally Deleted.

        10.    USE AND CONDITION OF SUBLEASED PREMISES

        a. Subtenant acknowledges that its intended use of the Subleased
Premises for biotechnology research and development purposes does not fall
within the "Permitted Use" under the Prime Lease. Subtenant cannot engage in any
use outside of the Permitted Use unless it has received the prior written
consent to such other uses from Prime Landlord and has provided Subtenant with a
copy of such prior written consent.

        b. Subtenant acknowledges that: (i) it has been advised by Sublandlord
to satisfy itself with respect to the condition of the Subleased Premises
(including, without limitation, the HVAC, electrical, plumbing and other
mechanical installations, fire sprinkler systems, security, environmental
aspects, and



                                     - 11 -
<PAGE>   16

compliance with applicable laws, ordinances, rules and regulations) and the
present and future suitability of the Subleased Premises for Subtenant's
intended use; (ii) Subtenant has had the opportunity to make such inspection and
investigation as it deems necessary with reference to such matters; (iii)
neither Sublandlord or nor any of Sublandlord's agents has made any oral or
written representations or warranties with respect to the condition, suitability
or fitness of the Subleased Premises other than as may be specifically set forth
in this Sublease; and (iv) neither Sublandlord nor any of Sublandlord's agents
has agreed to undertake any alterations, additions, or improvements to or to
perform any maintenance or repair of the Subleased Premises prior to or at
delivery of possession of the Subleased Premises or during the term of this
Sublease, except that Sublandlord shall (i) at Subtenant's sole cost and
expense, construct the Subtenant Improvements (as defined below), and (ii) prior
to the Phase II Commencement Date, dismantle and remove its computer lab
equipment from Phase II. Except for the foregoing, Subtenant accepts the
Subleased Premises in its "As-Is" condition existing on the date Subtenant
executes this Sublease, subject to all matters of record and applicable laws,
ordinances, rules and regulations. Subtenant agrees to reimburse Sublandlord
within 30 days after written demand therefor, together with a copy of invoices
and other documentation that reasonably supports such costs, for Sublandlord's
reasonable, actual, out-of-pocket costs



                                     - 12 -
<PAGE>   17

to prepare for the dismantling and removal of, and dismantle and remove, the
computer lab equipment from Phase II, which reimbursement obligation shall not
exceed $200,000.

        c. Upon the Phase I Commencement Date, Sublandlord shall promptly
commence and thereafter diligently pursue to completion the following work
("Phase I Improvements"), at Subtenant's sole cost and expense: (i) installation
of a demising wall between Phase I and Phase II (which is needed because
Sublandlord will continue to use and occupy Phase II until the Phase II
Commencement Date); (ii) close off one door that leads to Phase II and move one
door that leads to Phase II, (iii) install security features on the door
installed in the demising wall such that Sublandlord can limit Subtenant's
access to Phase II while Sublandlord is occupying Phase II, and (iv) re-balance
the distribution of electrical service and HVAC service serving Phase I and
Phase II such that electrical and HVAC service adequate for Subtenant's and
Sublandlord's respective uses in Phase I and Phase II is available. It is
estimated that the Phase I Improvements will cost approximately $25,000.
Subtenant shall reimburse Sublandlord for all costs incurred by it in completing
the Phase I Improvements within 30 days after Sublandlord delivers to Subtenant
a bill for such costs, together with a copy of invoices and other documentation
that reasonably supports such costs; provided, however, such reimbursement
obligation shall not



                                     - 13 -
<PAGE>   18

exceed $35,000, and any costs in excess of $35,000 shall be paid by Sublandlord.

        Since Phase I and Phase II will not be separately metered or
sub-metered, Subtenant shall pay for all utilities consumed in Phase I and Phase
II. Until the Phase II Commencement Date Sublandlord shall reimburse Subtenant
for Sublandlord's proportionate share (based on the relative square footage of
Phase I and Phase II) of electrical and HVAC service, provided that Subtenant
has given Sublandlord a copy of the utility bills for such service and the
calculation showing apportionment of such utility bills between Subtenant and
Sublandlord. Sublandlord shall make such reimbursement within 30 days after
receiving the utility bills.

        d. Notwithstanding anything to the contrary in this Sublease,
Sublandlord warrants that, to its actual knowledge, without investigation, as of
the date of this Sublease with respect to Phase I and Phase II (i) Phase I and
Phase II comply with all laws, codes, ordinances and other governmental
requirements then applicable to Phase I and Phase II, (ii) Phase I and Phase II,
including the improvements and equipment located therein, are in good working
order, condition and repair, (iii) Phase I and Phase II are free of any
Hazardous Materials contamination, and (iv) there are no material physical
defects in Phase I and Phase II which would unreasonably interfere with the



                                     - 14 -
<PAGE>   19

use of Phase I and Phase II for research and development purposes.

        11.    ALTERATIONS

        Subtenant shall not make alterations, improvements or installations in
or to the Subleased Premises without the prior written consent of Sublandlord,
which consent shall not be unreasonably withheld, and without the prior written
consent of Prime Landlord, as provided in the Prime Lease. Any alterations,
improvements or installations permitted under this Sublease and the Prime Lease
or which are consented to by the Sublandlord and the Prime Landlord shall be
made by Subtenant or Subtenant's contractors at the sole cost and expense of
Subtenant. All alterations, improvements or installations to the Subleased
Premises made by Subtenant shall remain the property of the Prime Landlord and
shall be surrendered to the Prime Landlord with the Subleased Premises at the
Expiration Date of this Sublease, as set forth in the Prime Lease; provided,
however, Subtenant shall remove any or all of such alterations, improvements, or
installations, together with the Phase I Improvements and any alterations,
improvements or installations made by Sublandlord prior to Subtenant's occupancy
of the Subleased Premises, and immediately repair any resulting damage to the
Subleased Premises if and to the extent required by Prime Landlord under the
Prime Lease at the expiration or earlier termination of this Sublease.



                                     - 15 -
<PAGE>   20

        Under the Consent to Sublease, Prime Landlord is requiring a Restoration
Deposit (as defined therein) to secure the restoration obligations under the
Prime Lease ("Restoration Obligations"). Subtenant agrees to pay the Restoration
Deposit to Prime Landlord, as well as any future restoration deposits that Prime
Landlord may require in connection with any future alterations to the Subleased
Premises that Subtenant may seek to make (collectively, "Restoration Deposits").
Sublandlord agrees that Subtenant is entitled, upon the expiration of the Term
and provided that there has not occurred and is not continuing a material
default by Subtenant under this Sublease, to the return of that portion of the
Restoration Deposits that has not been applied pursuant to the Consent to
Sublease or any future agreements among Sublandlord, Subtenant and Prime
Landlord. If this Sublease terminates prior to the expiration of the Term,
Subtenant agrees that Prime Landlord shall be entitled to retain the Restoration
Deposits until the expiration of the term of the Prime Lease. At that time, (i)
if Prime Landlord completes the Restoration Obligations then Subtenant shall be
entitled to the return of the unapplied portion of the Restoration Deposits, and
(ii) if Sublandlord completes the Restoration Obligations, then Sublandlord
shall be entitled to apply the Restoration Deposits against Sublandlord's actual
costs to complete the Restoration Obligations, together with a ten percent (10%)
construction management fee to compensate Sublandlord for its time in



                                     - 16 -
<PAGE>   21

undertaking the Restoration Obligations. Upon its completion of the Restoration
Obligations, Sublandlord shall refund the balance of the Restoration Deposits,
if any, to Subtenant, and if Sublandlord's actual costs and construction
management fee exceed the amount of the Restoration Deposits, then Subtenant
shall reimburse Sublandlord within 20 days after written demand for such excess
amounts.

               Subtenant acknowledges that until the Phase II Commencement Date
Sublandlord will be continuously operating a computer lab from Phase II. It is
of critical importance that Sublandlord's operations in Phase II not be
disrupted or interfered with in any manner whatsoever by any alterations,
additions or improvements to Phase I made by Subtenant. Accordingly, until the
Phase II Commencement Date Subtenant shall not undertake any construction in
Phase I without (i) providing Sublandlord with at least 10 days' prior written
notice of the date of commencement of any such construction, (ii) establishing
and enforcing rules and regulations with its contractors and suppliers such that
the construction will not disrupt or interfere with Sublandlord's operations in
Phase II, and (iii) allowing Sublandlord and its agents continual access to
Phase I and continuing updates concerning such construction so that Sublandlord
can evaluate the potential of such construction disrupting or interfering with
Sublandlord's operations in Phase II. If at any time during such construction
Sublandlord



                                     - 17 -
<PAGE>   22
reasonably believes that such construction is disrupting or interfering with, or
there is a significant likelihood that such construction will disrupt or
interfere with, Sublandlord's operations in Phase II, Sublandlord shall have the
right to require Subtenant, at Subtenant's sole cost and expense, to immediately
cease the construction or to modify the manner of construction so as to
eliminate or reduce the likelihood of any such disruption or interference.
Without diminishing any other indemnities given by Subtenant in this Sublease
(including all indemnities applicable to Subtenant through the Prime Lease),
Subtenant agrees to indemnify, defend and hold Sublandlord, its officers,
directors, employees and agents, and each of their respective successors and
assigns, harmless from and against all loss, cost, claims, causes of action,
expenses, liability and damages of any kind whatsoever threatened against or
incurred by such parties as a result of any disruption or interference with
Sublandlord's operations in Phase II resulting, directly or indirectly, from
Subtenant's construction of any work in Phase I.

        12.    REPAIRS AND MAINTENANCE

        Any repair and maintenance obligations with respect to the Subleased
Premises which are the responsibility of the Sublandlord, as tenant under the
Prime Lease, shall be performed, in a timely manner, by Subtenant at Subtenant's
sole cost and expense. In the event that Prime Landlord is obligated to repair
or maintain any portions of the Subleased Premises under the



                                     - 18 -
<PAGE>   23

terms of the Prime Lease, Subtenant shall look solely to Prime Landlord for the
performance of such obligations. If Subtenant provides Sublandlord with written
notice of Prime Landlord's failure to perform any such obligations, Sublandlord
shall undertake Enforcement Efforts, whereupon Sublandlord shall not be liable
to Subtenant for Prime Landlord's failure to fulfill any such obligations.

        13.    UTILITIES AND SERVICES

        Subtenant shall be entitled to all those services and utilities which
Prime Landlord is required to provide under the terms of the Prime Lease;
provided, however, that Subtenant shall pay for the costs of all utilities and
garbage services provided to or consumed in the Subleased Premises, subject to
Sublandlord's obligation to reimburse Subtenant for Sublandlord's Proportionate
Share of such costs. Subtenant shall look solely to the Prime Landlord for the
provision of those services and utilities which Prime Landlord is required to
provide under the terms of the Prime Lease, and, provided that Sublandlord
undertakes Enforcement Efforts following receipt of written notice from
Subtenant of Prime Landlord's failure to provide such services and utilities,
Sublandlord shall not be responsible for Prime Landlord's failure to provide the
same. Until the Phase II Commencement Date, Sublandlord shall pay and provide
for its own janitorial service for Phase II.



                                     - 19 -
<PAGE>   24

        14.    ASSIGNMENT AND SUBLEASING

        Subtenant shall not have the right to assign this Sublease or sublet the
Subleased Premises, in whole or in part, without the prior written consent of
Sublandlord, which consent shall not be unreasonably withheld, and without the
prior written consent of the Prime Landlord, all under the terms and conditions
set forth in the Prime Lease.

        15.    INSURANCE

        Subtenant agrees to comply with all of the insurance requirements and
obligations of Sublandlord as set forth in the Prime Lease. In addition to any
such insurance requirements and obligations, Subtenant hereby agrees to procure
and maintain throughout the term of this Sublease, at its sole costs and
expense, environmental remediation insurance for Use of Hazardous Substances (as
such term is defined in Section 17 below), which environmental remediation
insurance shall be on such terms and underwritten by such companies as are
reasonably acceptable to Sublandlord

        16.    SIGNS - BUILDING DIRECTORY

        Subtenant shall have the right to place any sign on the exterior of the
Building or in such manner within the Subleased Premises as may be visible from
the exterior of the Building only in accordance with the terms and conditions of
the Prime Lease. Subtenant shall have the right to place identification signs on



                                     - 20 -
<PAGE>   25

its entrance doors to the Subleased Premises in accordance with the terms and
conditions of the Prime Lease.

        17.    COMPLIANCE WITH LAWS

        a. In addition to any obligations under the Prime Lease, Subtenant shall
promptly comply with all statutes, ordinances, rules, orders, regulations and
requirements of the Federal, State and municipal Governments and of any and all
their Departments and Bureaus applicable to its intended use and occupancy of
the Subleased Premises by Subtenant or any subtenant or assignee of Subtenant,
for the correction, prevention and abatement of nuisances, violations or other
grievances, in, upon or connected with Subtenant's specific use of the Subleased
Premises during the Term or any renewal thereof, including without limitation,
all laws relating to environmental matters and the Americans with Disabilities
Act, and shall also promptly comply with, and execute all rules, orders and
regulations of the Board of Fire Underwriters relating to Subtenant's specific
use of the Subleased Premises and promulgated for the prevention of fires
(collectively referred to as "Legal Requirements") at its own cost and expense.

        b. Without limiting the generality of Section 17.a above, Subtenant
agrees to comply with all Legal Requirements and prudent business practices
applicable to Subtenant's use, transportation, storage, disposal, release,
discharge or generation (collectively, shall be referred to hereinafter "Use



                                     - 21 -
<PAGE>   26

of Hazardous Materials") of any Hazardous Materials in, on, to, under, from or
about the Subleased Premises or the Building. Subtenant shall indemnify, defend
(by counsel reasonably acceptable to the indemnified party), protect and hold
Sublandlord, its officers, directors, employees and agents, and each of their
respective successors and assigns, free and harmless from and against any and
all claims, demands, causes of action, damages, liabilities, penalties, fines,
losses or expenses (including, without limitation, attorneys' fees and costs and
court costs), arising from or caused in whole or in part, directly or
indirectly, by Subtenant's Use of Hazardous Substances to, in, on, under, about
or from the Subleased Premises or Building or Subtenant's failure to comply with
any Legal Requirements as set forth above. For purposes of the indemnity
provisions hereof, any acts or omissions of Subtenant, or by employees, agents,
assignees, contractors or subcontractors of Subtenant or others for whose acts
Subtenant is legally responsible or liable (whether or not they are negligent,
intentional, willful or unlawful) shall be strictly attributable to Subtenant.
This indemnification shall include without limitation any diminution in the
value of the Subleased Premises or Building, damages for the loss or restriction
on use of the Subleased Premises or Building, and remediation expenses. The
indemnification contained herein shall survive the expiration or earlier
termination of this Sublease.



                                     - 22 -
<PAGE>   27

        c. As used in this Sublease, the term "Hazardous Substances" shall mean
hazardous wastes, hazardous chemicals, biological and/or medical waste,
flammable or explosive materials, radioactive materials, toxic materials or
related materials (whether potentially injurious to persons or property and
whether potentially injurious by themselves or in combination with other
materials), including, but not limited to, petroleum products or fractions
thereof and any waste, chemical, substance or material now or hereafter
determined by any federal, state or local governmental agency or authority
having jurisdiction to be hazardous to human health or the environment or which
is or becomes regulated by such agency or authority (including, but not limited
to, those materials listed in the United States Department of Transportation
Hazardous Materials Table as amended from time to time), which were released to
the environment, including, without limitation, the soil, groundwater and/or
air, at the Subleased Premises.

        d. Sublandlord shall have the right, at any time on at least one
business day's prior notice, to enter the Subleased Premises, to inspect the
same and, at Subtenant's cost and expense, to conduct such tests as Sublandlord
reasonably deems appropriate to see if Subtenant is complying with the
provisions of Section 17.b. Additionally, Subtenant shall provide Sublandlord on
demand with a copy of any permits, manifests, or other documentation that
evidences that Subtenant is complying



                                     - 23 -
<PAGE>   28

with the provisions of Section 17.b with respect to its Use of Hazardous
Materials.

        18.    NON-BINDING MEDIATION

        a. If a dispute arises out of or relates to this Sublease, or its
breach, and the parties have not been successful in resolving such dispute
through negotiation, the parties agree to attempt to resolve the dispute through
non-binding mediation by submitting the dispute to a sole mediator selected by
the parties or, at the option of a party, to mediation by the American
Arbitration Association ("AAA"). If such dispute is not resolved by such
non-binding mediation, the parties shall have the right to resort to any
remedies permitted by law. All defenses based on passage of time shall be tolled
during the mediation.

        b. The direct expenses of the mediation, including the compensation and
expenses of the mediator and the fees of the AAA, shall be borne equally by the
parties. All other costs incurred by the parties to this Sublease, including the
parties' legal expenses and their witnesses' expenses, shall be borne by the
party incurring the expense. The parties, their representatives, other
participants and the mediator shall hold the existence, content and result of
the mediation in confidence.

        19.    ESTOPPEL CERTIFICATES

        Subtenant agrees that from time to time upon not less than fifteen (15)
days prior notice by Sublandlord, Subtenant or its duly authorized
representative having knowledge of the following



                                     - 24 -
<PAGE>   29

facts will deliver to Sublandlord, or to such person or persons as the
Sublandlord may designate, a statement in writing certifying (a) that this
Sublease is unmodified and in full force and effect (or if there have been
modifications, that the Sublease as modified is in full force and effect); (b)
the date to which the Rent and other charges have been paid; (c) that to the
best of Subtenant's knowledge, the Sublandlord is not in default under any
provision of this Sublease or if in default, the nature thereof in detail. Any
such statement may be conclusively relied upon by any prospective purchaser or
encumbrancer of the Subleased Premises. Subtenant's failure to deliver such
statement within the specified time shall be conclusive upon Subtenant (a) that
this Sublease is in full force and effect, without modification except as may be
represented by Sublandlord; (b) that there are no uncured defaults in
Sublandlord's performance; and (c) that not more than one month's rent has been
paid in advance, or such failure may be considered by Sublandlord as a default
by Subtenant under this Sublease.

        20.    SUBORDINATION

        This Sublease shall be subject and subordinate to the Prime Lease, any
ground lease and to any mortgage or deed of trust thereon or on the fee simple
interest in the Building or the land on which the Building is located.



                                     - 25 -
<PAGE>   30

        21.    CASUALTY AND CONDEMNATION

        If the Prime Lease is terminated with respect to the Subleased Premises
pursuant to the casualty and condemnation provisions of the Prime Lease, this
Sublease shall automatically terminate at the same time. If the Prime Lease is
not terminated with respect to the Subleased Premises upon the occurrence of a
casualty or condemnation, the provisions of the Prime Lease with respect to
casualty or condemnation shall apply to this Sublease and the Subleased
Premises.

        22.    CONSENT OR APPROVAL OF PRIME LANDLORD

        If the consent or approval of Prime Landlord is required under the Prime
Lease with respect to any matter relating to the Subleased Premises, Subtenant
shall, at its sole costs and expense, directly obtain such consent or approval
from the Prime Landlord. Sublandlord shall have no liability to Subtenant for
the failure of Prime Landlord to give its consent; however, Sublandlord will
cooperate with Subtenant, at Subtenant's sole costs and expense, in any
reasonable attempt to obtain Prime Landlord's consent. Provided that Sublandlord
undertakes Enforcement Efforts, Sublandlord shall have no liability to Subtenant
if the Prime Landlord shall default in the performance of any of its obligations
under the Prime Lease or breach any provision of the Prime Lease pertaining to
the Subleased Premises.



                                     - 26 -
<PAGE>   31

        23.    NOTICES

        All notices given pursuant to the provisions of this Sublease shall be
in writing, addressed to the party to whom notice is given and sent registered
or certified mail, return receipt requested, in a postpaid envelope or by
nationally recognized overnight delivery service as follows:

                             To Subtenant:

                             2101 Harbor Bay Parkway, Suite 1000
                             Alameda, California 94502
                             Attention:_________________


                             To Sublandlord:
                             Lucent Technologies Inc.
                             475 South Street
                             Morristown, New Jersey 07962
                             Attention: Lease Administrator

with a copy to:              Lucent Technologies Inc.
                             1701 Harbor Bay Parkway
                             Alameda, California 94502
                             Attention: Transaction Manager

        All notices shall be deemed given upon receipt or rejection. Either
party by notice to the other may change or add persons and places where notices
are to be sent or delivered. In no event shall notice have to be sent on behalf
of either party to more than three (3) persons.

        24.    BROKERS

        The parties warrant that they have had no dealings with any real estate
broker or agent in connection with this Sublease, except that Sublandlord has
engaged Cushman & Wakefield to



                                     - 27 -
<PAGE>   32

represent it in this transaction and Subtenant has engaged Mr. Chuck Campagnet
of Colliers Parrish to represent it in this transaction (collectively, the
"Broker(s)"). Each party covenants to pay, hold harmless and indemnify the other
from and against any and all costs, expenses or liabilities for any
compensation, commissions and charges claimed by any other broker or agent with
respect to this Sublease or the negotiation thereof, based upon alleged dealings
with the indemnifying party.

        25.    SUBLANDLORD'S AND SUBTENANT'S POWER TO EXECUTE

        Sublandlord and Subtenant covenant, warrant and represent that they have
full power and proper authority to execute this Sublease.

        26.    CONSENT TO SUBLEASE BY PRIME LANDLORD

        This Sublease shall not become operative until and unless the Prime
Landlord has given to Sublandlord its consent hereto and to all matters related
to this Sublease for which Prime Landlord's consent is required pursuant to the
Prime Lease, including but not limited to Subtenant's intended use of the
Subleased Premises and Subtenant's construction of the Subtenant Improvements.
Sublandlord shall use commercially reasonable efforts to obtain the consent of
the Prime Landlord, however, Sublandlord shall not be responsible for Prime
Landlord's failure to consent to this Sublease or other matters related thereto.
Should Prime Landlord not so consent, each party shall be released from all
obligations with respect hereto and neither



                                     - 28 -
<PAGE>   33

party shall have any further rights in law or in equity with respect to this
Sublease.

        27.    HOLDOVER

        Subtenant covenants and agrees that, notwithstanding Section 12 of the
Prime Lease, Subtenant shall not hold over after the expiration or earlier
termination of this Sublease without the express prior written consent of
Sublandlord or the Prime Landlord. In the event that Subtenant does hold over
without such consent, Subtenant shall become a tenant at sufferance and shall
pay Sublandlord a monthly rent equal to two hundred percent (200%) of the
Monthly Basic Rent in effect during the last thirty (30) days of the Term. In
addition to the foregoing monthly rent, Subtenant shall be liable to Sublandlord
for any and all amounts due and owing pursuant to the terms and provisions of
Section 12 of the Prime Lease.

        28.    DEFAULT AND REMEDIES

        a. The occurrence of any one or more of the following events shall
constitute a material default and breach of this Sublease by Subtenant: (i) any
act or omission which constitutes a default under the Prime Lease; (ii) the
failure by Subtenant to make any payment of rent or any other payment required
to be made by Subtenant hereunder, as and when due, where such failure shall
continue for a period of five (5) days after written notice thereof from
Sublandlord to Subtenant; and (iii) the failure by Subtenant to perform any of
the covenants, conditions or



                                     - 29 -
<PAGE>   34

provisions of this Sublease, where such failure shall continue for a period of
thirty (30) days after written notice thereof from Sublandlord to Subtenant,
provided, however, that if the nature of such failure is such that it cannot
reasonably be cured within said 30 day period, then Subtenant shall be deemed
not to be in default, provided Subtenant commences to cure within said 30 day
period and thereafter diligently prosecutes such cure to completion.

        b. In the event of any such material default by Subtenant, Sublandlord
shall have all of the rights and remedies available to Prime Landlord under
Section 24 of the Prime Lease (including without limitation Section 24.5),
except that the term "Landlord" therein shall be deemed to refer to Sublandlord
and the term "Tenant" therein shall be deemed to refer to Subtenant. Sublandlord
may at any time after a material default by Subtenant, with or without notice or
demand, exercise any of such rights or remedies available to Sublandlord.

        29.    ENTIRE AGREEMENT

        This Sublease (which includes each of the Exhibits attached hereto)
contains the entire agreement between the parties and all prior negotiations and
agreements are merged into this Sublease. This Sublease may not be changed,
modified, terminated or discharged, in whole or in part, nor any of its
provisions waived except by a written instrument which (a) shall expressly refer
to this Sublease and (b) shall be executed by the party against whom



                                     - 30 -
<PAGE>   35

enforcement of the change, modification, termination, discharge or waiver shall
be sought.

        30.    TABLE OF CONTENTS - CAPTIONS

        The Table of Contents and the captions appearing in this Sublease are
inserted only as a matter of convenience and do not define, limit, construe or
describe the scope or intent of the sections of this Sublease nor in any way
affect this Sublease.

        31.    SURVIVAL

        The covenants, indemnities and other obligations contained in this
Sublease shall survive the expiration of the Term or earlier termination of this
Sublease.



                                     - 31 -
<PAGE>   36

        IN WITNESS WHEREOF, the parties hereto have caused this Sublease to be
properly executed as of the day and year first above written.

ATTEST/WITNESS:                             SUBLANDLORD

                                            LUCENT TECHNOLOGIES INC.,
                                            a Delaware corporation

By:  /s/ Daniel E. Carrick                  By:  /s/ Deborah J. Quok     (SEAL)
   --------------------------------            --------------------------

Daniel E. Carrick Paralegal                 Deborah J. Quok, Transaction Manager
-----------------------------------         ------------------------------------
Name and Title                              Name and Title

ATTEST/WITNESS:                             SUBTENANT

                                            AVIGEN, INC.,
                                            a Delaware corporation


                                            By: /s/ John Monahan         (SEAL)
-----------------------------------            --------------------------

                                                  John Monahan, CEO
-----------------------------------         -----------------------------
Name and Title                              Name and Title



                                     - 32 -
<PAGE>   37

                            CONSENT OF PRIME LANDLORD

        Prime Landlord executes this Sublease to evidence its consent to the
Sublease and to the provisions herein set forth.

ATTEST/WITNESS:                             PRIME LANDLORD

                                            ARE-1201 HARBOR BAY, LLC,
                                            a Delaware limited liability company


                                            By:
-----------------------------------            ---------------------------------

-----------------------------------         ------------------------------------
Name and Title                              Name and Title



                                     - 33 -
<PAGE>   38

                                    EXHIBIT A

                        Description of Subleased Premises

[Graphic depicting a floor plan for suite 150 of the building located at 1201
Harbor Bay Parkway, Alameda, Ca.]



                                     - 34 -
<PAGE>   39

EXHIBIT B

Intentionally Deleted.



                                     - 35 -
<PAGE>   40

                                    EXHIBIT C

                                   Prime Lease

A copy of the document that comprises Exhibit C will be provided supplementally
to the Commission upon request.


                                     - 36 -
<PAGE>   41

                               CONSENT TO SUBLEASE

        This Consent to Sublease (this "CONSENT") is made as of February 10,
2000, by ARE - 1201 HARBOR BAY LLC, a Delaware limited liability company, having
an address of 135 North Los Robles Avenue, Suite 250, Pasadena, California 91101
("LANDLORD"), LUCENT TECHNOLOGIES INC. a Delaware corporation, having an address
of 475 South Street, Morristown, New Jersey 07962 ("TENANT"), AND AVIGEN, INC.,
a Delaware corporation, having an address of 1201 Harbor Bay Parkway, Alameda,
California 94502 ("SUBLESSEE") with reference to the following Recitals.

                                 R E C I T A L S

           A. Landlord and Ascend Communications, Inc. ("ASCEND") entered into
that certain Lease (the "Lease") dated June 1, 1998, wherein Landlord leased to
Ascend certain premises (the "PREMISES") consisting of approximately 22,348
rentable square feet in the building located at 1201 Harbor Bay Parkway,
Alameda, California, as more particularly described in the Lease. Ascend was
acquired by Tenant as of October 1, 1999.

           B. Tenant desires to sublease to Sublessee the Premises in two
phases, the first of which consists of 15,348 rentable square feet (the "PHASE I
SUBLEASED PREMISES") and the second of which consists of 7.000 rentable square
feet (the "PHASE 11 SUBLEASED PREMISES" and with the Phase I Subleased Premises
the "SUBLEASED PREMISES") all as more particularly described in and pursuant to
the provisions of that certain Sublease dated as of February 1, 2000 (the
"SUBLEASE"), a copy of which is attached hereto.

           C. Tenant desires to obtain Landlord's consent to the Sublease.

        NOW, THEREFORE, in consideration of the foregoing and the agreements
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Landlord hereby consents to:

               (a)    the sublease of the Subleased Premises to Sublessee,

               (b)    notwithstanding the restrictions contained in the Lease,
                      Sublessee's use of the Subleased Premises for research and
                      development laboratory, related office and other related
                      uses consistent with the character of the Project;

               (c)    the installation of the alterations being made to the
                      Subleased

<PAGE>   42

                      Premises in connection with the Sublease (the "Sublease
                      Improvements"),

such consent being subject to and upon the following terms and conditions to
which Tenant and Sublessee hereby agree:

        1. All initially capitalized terms not otherwise defined in this Consent
           shall have the meanings set forth in the Lease unless the context
           clearly indicates otherwise.

        2. This Consent shall not be effective and the Sublease shall not be
           valid nor shall Sublessee take possession of the Subleased Premises
           unless and until Landlord shall have received: (a) a fully executed
           counterpart of the Sublease, (b) a fully executed counterpart of this

Consent, and (c) reimbursement from Tenant for all of Landlord's costs and
expenses in preparing and negotiating this Consent and the documents described
herein, not to exceed $2,500.

        3. Landlord's consent set forth herein is subject to the following
           additional conditions:

           (a) Landlord shall have received and approved the plans and
specifications for Sublessee's proposed alterations, additions or improvements
to be made in connection with Sublessee's occupancy of the Subleased Premises
(collectively, "Sublease Improvements"): provided, however, that Tenant and
Sublessee hereby acknowledge and agree that notwithstanding anything to the
contrary contained in the Lease, Landlord shall have the right to require that
the Sublease Improvements be removed at the expiration or earlier termination of
the Lease at no cost or expense to Landlord and that the Subleased Premises be
fully restored to their condition prior to the installation of such Sublease
Improvements with all damage occasioned by such removal being fully repaired,
provided, however, that if upon any such expiration or earlier termination of
the Lease (i) Sublessee immediately succeeds to Tenant's interest in the
Subleased Premises, and (ii) Landlord continues to hold the Restoration Deposit,
as defined below, Landlord shall not require the removal of the Sublease
Improvements upon any such expiration or earlier termination of the Lease.

           (b) Landlord shall have received a restoration deposit in the amount
of $30 per rentable square foot of the Sublease Improvements ("RESTORATION
DEPOSIT"), which shall be held by Landlord against the obligation of Tenant to
restore the Premises to their condition existing before the construction of the
Sublease Improvements. Such Restoration Deposit shall be held by Landlord as
security for the performance of Tenant's restoration obligations under the
Lease. The Restoration Deposit is not an advance rental deposit or a measure of
Landlord's damages in case

<PAGE>   43

of Tenant's default. Upon Tenant's failure, following an election by Landlord to
require removal of the Sublease Improvement to remove such Sublease Improvements
and to restore the Sublease Premises to their condition existing before the
construction of the Sublease Improvements, Landlord may use all or part of the
Restoration Deposit to cause such removal and restoration, without prejudice to
any other remedy provided herein or provided by law. Landlord's obligation
respecting the Restoration Deposit is that of a debtor, not a trustee-, no
interest shall accrue thereon. The Restoration Deposit shall be the property of
Landlord, but shall be paid to Tenant when Tenant's obligations under this Lease
have been completely fulfilled. Landlord shall be released from any obligation
with respect to the Restoration Deposit upon transfer of this Lease and the
Premises to a person or entity assuming Landlord's obligations under this
Section 3(b). Tenant hereby waives the provisions of any law, now or hereafter
in force, which provide that Landlord may claim from a security deposit only
those sums reasonably necessary to remedy defaults in the payment of Rent, to
repair damage caused by Tenant or to clean the Premises. If Tenant shall fully
perform the provisions of Section 3(a) hereof, the Restoration Deposit, or any
balance thereof, shall be returned to Tenant (or, at Landlord's option, to the
last assignee of Tenant's interest hereunder) within 90 days after the
expiration or earlier termination of this Lease. Following any use by Landlord
of the Restoration Deposit to remove such Sublease Improvements, any remaining
balance thereof shall be returned to Tenant (or, at Landlord's option, to the
last assignee of Tenant's interest hereunder).

           (c) Landlord shall have received and approved a Hazardous Materials
List and all Documents relating to Sublessee's proposed use of the Subleased
Premises; and

           (d) The Lease shall be amended by adding the following to the end of
the second grammatical sentence of Section 17.1

           "including, without limitation, requiring a Restoration Deposit (as
           such term is defined in that certain Consent to Sublease dated as of
           February 10, 2000, by and among Landlord, Tenant, and Avigen, Inc.),
           in connection with any such Permitted Alteration which, in Landlord's
           reasonable opinion, substantially destroy the office improvements
           existing in the Lucent Space as of the date hereof."

           (e) The Lease shall be amended by deleting Section 40 of the Lease
and substituting the following therefor.

"40.       ENVIRONMENTAL REQUIREMENTS.

"(a) PROHIBITION/COMPLIANCE/INDEMNITY. Tenant shall not cause or permit any
Hazardous Materials (as hereinafter defined) to be brought upon, kept or used in
or about the Premises or the Project in violation of applicable law by Tenant,
its agents, employees. contractors or invitees. If Tenant breaches the
obligation stated in the preceding sentence, or if the

<PAGE>   44

presence of Hazardous Materials in the Premises during the Term or any holding
over results in contamination of the Premises, the Project or any adjacent
property or if contamination of the Premises, the Project or any adjacent
property by Hazardous Materials Is brought into the Premises by anyone other
than Landlord and Landlord's employees agents and contractors otherwise occurs
during the Term or any holding over, Tenant hereby indemnifies and shall defend
and hold Landlord, its officers, directors, employees, agents and contractors
harmless from any and all claims, judgments, damages, penalties, fines, costs,
liabilities, or losses (including, without limitation, diminution in value of
the Premises or any portion of the Project, damages for the loss or restriction
on use of rentable or usable space or of any amenity of the Premises or the
Project, damages arising from any adverse impact on marketing of space in the
Premises or the Project, and sums paid in settlement of claims, attorneys' fees,
consultant fees and expert fees) which arise during or after the Term as a
result of such contamination. This indemnification of Landlord by Tenant
includes, without limitation, costs incurred in connection with any
investigation of site conditions or any cleanup, remedial, removal, or
restoration work required by any federal, state or local governmental agency or
political subdivision because of Hazardous Materials present in the air, soil or
ground water above, on, or under the Premises. Without limiting the foregoing,
if the presence of any Hazardous Materials on the Premises, the Project or any
adjacent property caused or permitted by Tenant results in any contamination of
the Premises, the Project or any adjacent property, Tenant shall promptly take
all actions at its sole expense and in accordance with applicable law as are
necessary to return the Premises, the Project or any adjacent property to the
condition as nearly as economically practicable to the condition existing prior
to the time of such contamination, but in no event leaving more residual
contamination than permitted by law, provided that Landlord's approval of such
action shall first be obtained, which approval shall not unreasonably be
withheld so long as such actions would not potentially have any material adverse
long-term or short-term effect on the Premises or the Project.

" (b) BUSINESS. Landlord acknowledges that it is not the intent of this Section
40 to prohibit Tenant from using the Premises for the Permitted Use. Tenant may
operate its business according to the custom of the industry so long as the use
or presence of Hazardous Materials is strictly and properly monitored according
to all then applicable governmental requirements. As a material inducement to
Landlord to allow Tenant to use Hazardous Materials in connection with its
business, Tenant agrees to deliver to Landlord prior to the Commencement Date a
list identifying each type of Hazardous Materials to be present on the Premises
and setting forth any and all governmental approvals or permits required in
connection with the presence of such Hazardous Materials on the Premises
("HAZARDOUS MATERIALS LIST"). Tenant shall deliver to Landlord an updated
Hazardous Materials List at least once a year and shall also deliver an updated
list before any new Hazardous Material is brought onto the Premises. Tenant

<PAGE>   45

shall deliver to Landlord true and correct copies of the following documents
(the "HAZ MAT DOCUMENTS") relating to the handling, use, storage, disposal and
emission of Hazardous Materials prior to the Commencement Date, or if
unavailable at that time, concurrent with the receipt from or submission to a
governmental agency: permits; approvals; reports and correspondence; storage and
management plans, notice of violations of any laws; plans relating to the
installation of any storage tanks to be installed in or under the Project
(provided, said installation of tanks shall only be permitted after Landlord has
given Tenant its written consent to do so, which consent may be withheld in
Landlord's sole and absolute discretion); and all closure plans or any other
documents required by any and all federal, state and local governmental agencies
and authorities for any storage tanks installed in, on or under the Project for
the closure of any such tanks. Tenant is not required, however, to provide
Landlord with any portion(s) of the Haz Mat Documents containing information of
a proprietary nature which, in and of themselves, do not contain a reference to
any Hazardous Materials or hazardous activities. It is not the intent of this
Section to provide Landlord with information which could be detrimental to
Tenant's business should such information become possessed by Tenant's
competitors.

"(c) TENANT REPRESENTATION AND WARRANTY. Avigen hereby represents and warrants
to Landlord that (i) neither Avigen nor any of its legal predecessors has been
required by any prior landlord, lender or governmental authority at any time to
take remedial action in connection with Hazardous Materials contaminating a
property which contamination was permitted by Avigen or such predecessor or
resulted from Avigen's or such predecessor's action or use of the property in
question, and (ii) Avigen is not subject to any enforcement order issued by any
governmental authority in connection with the use, disposal or storage of a
Hazardous Materials. If Landlord determines that this representation and
warranty was not true as of the date of this lease, Landlord shall have the
right to terminate this Lease in Landlord's sole and absolute discretion.

"(d) INSPECTION RIGHTS. Landlord shall have the right to conduct annual tests of
the Premises to determine whether any contamination has occurred as a result of
Tenant's use. Tenant shall be required to pay the cost of such annual test of
the Premises, provided, however, that if Tenant conducts its own tests of the
Premises using third party contractors and test procedures acceptable to
Landlord which tests are certified to Landlord, Landlord shall accept such tests
in lieu of the annual tests to be paid for by Tenant. In addition, at any time,
and from time to time pursuant to Section 31.3, prior to the expiration or
earlier termination of the Term, Landlord shall have the right to conduct
appropriate tests of the Premises and the Project to determine if contamination
has occurred as a result of Tenant's use of the Premises. If contamination has
occurred for which Tenant is liable under this Section 30, Tenant shall pay all
costs to conduct such tests. If no such contamination is found, Landlord shall

<PAGE>   46

pay the costs of such tests (which shall not constitute an Operating Expense).
Landlord shall provide Tenant with a copy of all third party, non-confidential
reports and tests of the Premises made by or on behalf of Landlord during the
Term without representation or warranty and subject to a confidentiality
agreement. Landlord's receipt of or satisfaction with any environmental
assessment in no way waives any rights which Landlord may have against Tenant.

"(e) UNDERGROUND TANKS. If underground or other storage tanks storing Hazardous
Materials located on the Premises or the Project are used by Tenant or are
hereafter placed on the Premises or the Project by Tenant, Tenant shall monitor
such storage tanks, maintain appropriate records, implement reporting
procedures, properly close any underground storage tanks, and take or cause to
be taken all other actions necessary or required under applicable state and
federal law, as such now exists or may hereafter be adopted or amended in
connection with the use, maintenance, operation and closure of such storage
tanks.

"(f) TENANT'S OBLIGATIONS. Tenant's obligations under this Section 40 shall
survive the expiration or earlier termination of the Lease. During any period of
time after the expiration or earlier termination of this Lease required by
Tenant or Landlord to complete the removal from the Premises of any Hazardous
Materials as required pursuant to Tenant's obligations hereunder and the release
and termination of any licenses or permits held by Tenant or any person claiming
by or through Tenant restricting the use of the Premises, Tenant shall continue
to pay the full Rent in accordance with this Lease for any portion of the
Premises not relet by Landlord in Landlord's sole discretion, which Rent shall
be prorated daily.

"(g) DEFINITIONS. As used herein, the term "ENVIRONMENTAL REQUIREMENTS" means
all applicable present and future statutes, regulations, ordinances, rules,
codes, judgments, orders or other similar enactments of any governmental
authority or agency regulating or relating to health safety, or environmental
conditions on, under, or about the Premises or the Project, or the environment,
including without limitation, the following: the Comprehensive Environmental
Response; Compensation and Liability Act; the Resource Conservation and Recovery
Act; and all state and local counterparts thereto, and any regulations or
policies promulgated or issued thereunder. As used herein, the term "HAZARDOUS
MATERIALS" means and includes any substance, material, waste, pollutant, or
contaminant listed or defined as hazardous or toxic, or regulated by reason of
its impact or potential impact on humans, animals and/or the environment under
any Environmental Requirements, asbestos and petroleum, including crude oil or
any fraction thereof, natural gas liquids, liquefied natural gas, or synthetic
gas usable for fuel (or mixtures of natural gas and such synthetic gas). As
defined in Environmental Requirements, Tenant is and shall be deemed to be the
"operator" of Tenant's "facility" and the "owner" of all Hazardous Materials
brought on the Premises by Tenant, its agents,

<PAGE>   47

employees, contractors or invitees, and the wastes, by-products, or residues
generated, resulting, or produced therefrom "

(f) The Lease shall be amended by deleting the entire Right to Extend Term
Addendum.

(g) Landlord neither approves nor disapproves the terms, conditions and
agreements contained in the Sublease, all of which shall be subordinate and at
all times subject to (a) all of the covenants, agreements, terms, provisions and
conditions contained in the Lease, (b) superior ground leases, mortgages, deeds
of trust, or any other hypothecation or security now existing or hereafter
placed upon the real property of which the Premises are a part and to any and
all advances secured thereby and to all renewals, modifications, consolidations,
replacements and extensions thereof, and (c) all matters of record affecting the
Premises and all laws, ordinances and regulations now or hereafter affecting the
Premises.

4.         Nothing contained in the Sublease shall be construed to:

           (a) modify, waive, impair, or affect any of the terms, covenants or
conditions contained in the Lease (including Tenants obligation to obtain any
required consents for any other or future sublettings), or to waive any breach
thereof, or any rights or remedies of Landlord under the Lease against any
person, firm, association or corporation liable for the performance thereof, or
to enlarge or increase Landlord's obligations or liabilities under the Lease
(including, without limitation, any liability to Sublessee for any portion of
the security deposit held by Tenant under the Sublease), and all terms,
covenants and conditions of the Lease are hereby declared by each of Landlord
and Tenant to be in full force and effect; or

           (b) require Landlord to accept any payments from Sublessee on behalf
of Tenant;

In addition Tenant shall remain liable and responsible for the due keeping.
performance and observance of all the terms, covenants and conditions set forth
in the Lease on the part of the Tenant to be kept, performed and observed and
for the payment of the annual rent. additional rent and all other sums now and
hereafter becoming payable thereunder for all of the Premises, including,
without limitation, the Subleased Premises.

5          Notwithstanding anything in the Sublease to the contrary:

           (a) Sublessee does hereby expressly assume and agree to be bound by
and to perform and comply with, for the benefit of Landlord, each and every
obligation of Tenant under the Lease to the extent applicable to the Subleased
Premises, other than the obligation to pay Rent to Landlord. Landlord and
Sublessee each hereby release the other, and waive their respective rights of
recovery against the other for direct or consequential loss or damage arising
out of or incident to the perils covered by property insurance carried by such
party to the extent of such insurance and waive any right of subrogation which
might otherwise exist in or accrue to any person on account thereof. Nothing
herein shall, as between Tenant and Sublessee, modify, alter or affect any of
the terms of the Sublease.


<PAGE>   48

           (b) Tenant and Sublessee agree to each of the terms and conditions of
this Consent, and upon any conflict between the terms of the Sublease and this
Consent, the terms of this Consent shall control.

           (c) The Sublease shall be deemed and agreed to be a sublease only and
not an assignment and there shall be no further subletting or assignment of all
or any portion of the Premises demised under the Lease (including the Subleased
Premises demised by the Sublease) except in accordance with the terms and
conditions of the Lease.

           (d) If Landlord terminates the Lease as a result of a default It by
Tenant thereunder or the Lease terminates for any other reason, the Sublease
shall automatically terminate concurrently therewith, provided, however, if
Landlord elects, in its sole and absolute discretion and without obligation,
exercisable by giving written notice to Sublessee within 7 days of such
termination (a "REINSTATEMENT NOTICE"), to reinstate the Sublease and Sublessee
shall attorn to Landlord, in which case the Sublease shall become and be deemed
to be a direct lease between Landlord and Sublessee. If Landlord exercises the
option provided under this section, Landlord shall undertake the obligations of
Tenant under the Sublease from the time of the Reinstatement Notice through the
expiration or earlier termination of the Sublease, but Landlord shall not (a) be
liable for more than 1 month's rent or any security deposit paid by Sublessee
(except to the extent actually delivered to Landlord), (b) be liable for any
prior act or omission of Tenant under the Lease prior to the Reinstatement
Notice or for any other defaults of Tenant under the Sublease prior to the
Reinstatement Notice, (c) be subject to any defenses or offsets previously
accrued which Sublessee may have against Tenant for any period prior to the
Reinstatement Notice, or (d) be bound by any changes or modifications made to
the Sublease without the prior written consent of Landlord.

           (e) Tenant and Sublessee acknowledge and agree that if Tenant or
Landlord elects to terminate the Lease pursuant to the terms thereof, Landlord
shall have no responsibility, liability or obligation to Sublessee, and the
Sublease shall terminate except as expressly provided in Section 6(d) above

6. Any act or omission of Sublessee or anyone claiming under or through
Sublessee that violates any of the provisions of the Lease shall be deemed a
violation of the Lease by Tenant.

7. Upon a default by Tenant under the Lease, Landlord may proceed directly
against Tenant, any guarantors or anyone else liable under the Lease or the
Sublease without first exhausting Landlord's remedies against any other person
or entity liable thereon to Landlord. If Landlord gives Sublessee notice that
Tenant is in default under the Lease, Sublessee shall

<PAGE>   49

thereafter make directly to Landlord all payments otherwise due Tenant, which
payments will be received by Landlord without any liability to Landlord except
to credit such payments against amounts due under the Lease. The mention in this
Consent of any particular remedy shall not preclude Landlord from any other
remedy in law or in equity.

8. Tenant shall pay any broker commissions or fees that may be payable as a
result of the Sublease and Tenant hereby indemnifies and agrees to hold Landlord
harmless from and against any loss or liability arising there from or from any
other commissions or fees payable in connection with the Sublease which result
from the actions of Tenant. Sublessee hereby indemnifies and agrees to hold
Landlord harmless from and against any loss or liability arising from any
commissions or fees payable in connection with the Sublease which result from
the actions of Sublessee.

9. Tenant and Sublessee agree that the Sublease will not be modified or amended
in any way without the prior written consent of Landlord, which consent shall
not be unreasonably withheld or delayed. Tenant and Sublessee hereby agree that
it shall be reasonable for Landlord to withhold its consent to any modification
or amendment of the Sublease which would change the permitted use of the
Subleased Premises or which would affect Landlord's status as a real estate
investment trust. Any modification or amendment of the Sublease without
Landlord's prior written consent shall be void and of no force or effect.

10. This Consent may not be changed orally, but only by an agreement in writing
signed by Landlord and the party against whom enforcement of any change is
sought.

11. This Consent may be executed in any number of counterparts, each of which
shall be deemed an original, but all of which when taken together shall
constitute but one and the same instrument.

12. This Consent and the legal relations between the parties hereto shall be
governed by and construed and enforced in accordance with the internal laws of
the State in which the Property is located, without regard to its principles of
conflicts of law.

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<PAGE>   50

        IN WITNESS WHEREOF, Landlord, Tenant and Sublessee have caused their
duly authorized representatives to execute this Consent as of the date first
above written.

LANDLORD:                          ARE - 1201 HARBOR BAY LLC,
                                   a Delaware limited liability company

                                   BY:  ARE - QRS Corp., a Maryland corporation,
                                        Its managing member

                                   By:   /s/ Lynn Anne Shapiro
                                        ----------------------------------------
                                   Its:    General Counsel
                                        ----------------------------------------

TENANT:                            LUCENT TECHNOLOGIES, INC.,
                                   a Delaware corporation

                                   By:   /s/  illegible
                                        ----------------------------------------
                                   Its:    Transaction Manager
                                        ----------------------------------------

SUBLESSEE:                         AVIGEN, INC.,
                                   a Delaware corporation

                                   By:   /s/ John Monahan
                                        ----------------------------------------
                                   Its:    CEO and President
                                        ----------------------------------------