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                                                                    EXHIBIT 10.9

                              ADDENDUM TO SUBLEASE

1.    PARTIES.

      This Addendum to Sublease ("Sublease Addendum"), dated for reference
      purposes as of April 8, 2002, is made between WebSideStory, Inc.
      ("Sublessor"), and Avexus, Inc. ("Sublessee") in reference to that certain
      Sublease between Sublessor and Sublessee dated as of July 6, 2001 (the
      "Sublease"). This Sublease Addendum is a supplement to the Sublease, and
      together the Sublease and this Sublease Addendum form one integrated
      agreement.

2.    MASTER LEASE.

      Sublessor is the tenant under a written lease dated August 23, 1999 (the
      "Master Lease"), wherein LNR Seaview, Inc, a California corporation
      ("Lessor") leased to Sublessor the real property located in the City of
      San Diego, County of San Diego, State of California, described as: 10182
      Telesis Court, Suites 400, 500 and 600, San Diego, California, 92121
      ("Master Premises"). A true and correct copy of the Master Lease is
      attached hereto to the Sublease. Any capitalized terms used herein and not
      defined herein shall have the meanings set forth for such capitalized
      terms in the Master Lease. Any capitalized terms in this Sublease
      Addendum not defined herein shall have the meanings assigned to such terms
      in the Sublease.

3.    SUBLEASED PREMISES; USE.

      Sublessor hereby subleases to Sublessee on the terms and conditions set
      forth in this Sublease Addendum the following portion of the Master
      Premises: the portion of Suite 600 at 10182 Telesis Court indicated on
      EXHIBIT A attached hereto and consisting of the seven adjacent offices in
      area #7 (starting with the office adjacent to area #9 (the conference
      room) plus the adjacent hallway space in Area # 7, as marked on Attachment
      A (the "Additional Subleased Premises"). Sublessee may use the Additional
      Subleased Premises for the uses identified in Section 1.12 and Article 6.1
      of the Master Lease.

4.    TENANT IMPROVEMENTS AND UTILITIES.

      Sublessee shall not be entitled to construct any tenant improvements in
      the Additional Subleased Premises. At Sublessor's option, and subject to
      Landlord's consent, Sublessor may construct a hallway door between office
      number 7 and the next adjacent office (which office is marked office
      number "8" on EXHIBIT A). In such event, Sublessee will reimburse
      sublessor for 50% of the expense of such construction, not to exceed
      $2,000. Sublessee's rent will not be reduced during the construction
      period. Sublessee acknowledges that it will be responsible for the cost of
      running telephone cabling, data cabling, etc. to the Additional Subleased
      Premises, and all such cabling shall be done in a manner approved in
      advance by Sublessor with the objective of minimizing the expense of
      return of the Additional Subleased Premises to Sublessor at the end of the
      Term specified in Section 6. Utilities, security service and other
      expenses directly related to the entire sixth floor of the Master Premises
      (and not constituting Direct Expenses or Utilities Costs) will be
      allocated between the Sublessee and the Sublessor so that Sublessee will
      pay to Sublessor each month as invoiced by the applicable service provider
      an additional

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      14% of the total charges as reflected on such invoices. For the avoidance
      of doubt, the foregoing amount is in addition to the amounts required
      under the Sublease.

5.    WARRANTIES AND COVENANTS OF SUBLESSOR.

      Sublessor warrants and represents that, as of the Addendum Commencement
      Date (defined below), (i) the Additional Subleased Premises complies with
      all applicable laws, rules, regulations, codes, ordinances, underwriters'
      requirements, covenants, conditions and restrictions ("Laws"), (ii) the
      Additional Subleased Premises are in good and clean operating condition
      and repair, (iii) the electrical, mechanical, HVAC, plumbing, sewer,
      elevator, doors, and other systems serving the Additional Subleased
      Premises are in good operating condition and repair and (iv) that there
      are no "Hazardous Materials" present in the Additional Subleased Premises.
      Sublessor shall, promptly after receipt of notice from Sublessee, remedy
      any non-compliance with such warranty at Sublessor's sole cost and
      expense.

      As an inducement to Sublessee to enter the Sublease Addendum, Sublessor
      represents and warrants that (i) the Master Lease is in full force and
      effect, and there exists under the Master Lease no default or event of
      default by either Lessor or Sublessor, nor has there occurred any event
      which, with the giving of notice or the passage of time or both, could
      constitute such a default or event of default; (ii) there are no pending
      or threatened actions, suits or proceedings before any court or
      administrative agency against Sublessor, Lessor or third parties which
      could, in the aggregate, adversely affect the Additional Subleased
      Premises or any part thereof or the ability of Lessor or Sublessor to
      perform their respective obligations under the Master Lease or of
      Sublessor to perform its obligations under the Sublease Addendum, and
      Sublessor is not aware of any facts that might result in any such actions,
      suits or proceedings; (iii) there is no pending or threatened condemnation
      or similar proceeding affecting the Premises or any portion thereof, and
      Sublessor has no knowledge that any such action currently is contemplated.

      Sublessor shall (i) keep the Master Lease in effect; (ii) not modify,
      amend or waive any provisions thereof or make any election, exercise any
      option, right or remedy, or grant any consent or approval thereunder that
      in any such case would affect the Sublessee without, in each instance,
      Sublessee's prior written consent; (iii) pay the rent due and perform all
      of Sublessor's other obligations under the Master Lease, except to the
      extent that Sublessee is obligated to perform such other obligations under
      the Sublease Addendum; (iv) not take any action or omit to take any action
      that could cause or constitute a breach of the Master Lease or otherwise
      give rise to a right of Lessor to terminate the Master Lease or declare
      any provision thereof to have become ineffective; and (v) enforce
      performance of all obligations of Lessor under the Master Lease. In
      enforcing performance of all such obligations of Lessor, Sublessor shall
      (a) upon Sublessee's written request, immediately notify Lessor of its
      nonperformance under the Master Lease and request that Lessor perform its
      obligations under the Master Lease, and (b) permit Sublessee to commence a
      lawsuit or other action in Sublessee's name (and assign to Sublessee any
      rights of Sublessor required in connection therewith), or commence a

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      lawsuit or other action in Sublessor's name, to obtain the performance
      required from Lessor under the Master Lease, provided that Sublessee pays
      all costs and expenses incurred in connection with any such lawsuit or
      other action. Sublessor will also deliver all notices received from or
      sent to the Lessor affecting the Additional Subleased Premises, including,
      without limitation, any notices relating to any breaches or defaults under
      the Master Lease,

6.    TERM.

      For purposes of this Sublease Addendum, the term of this Sublease Addendum
      ("Sublease Addendum Term") shall commence on approval of this Sublease
      Addendum and, unless earlier terminated, continue until December 31, 2002.
      Either Sublessee or Sublessor may terminate this lease earlier in its
      discretion upon 75 days (seventy five days) written notice. Sublessor
      shall deliver possession of the Additional Subleased Premises no later
      than one (1) day after the receipt by Sublessor of the Lessor's consent
      referred to in Section 17. Notwithstanding the foregoing, if Sublessor has
      not delivered possession to Sublessee within one (1) day after receipt by
      Sublessor of the Lessor's consent referred to in Section 17, then at any
      time thereafter and before delivery of possession of the Additional
      Subleased Premises to Sublessee, Sublessee may give written notice to
      Sublessor of Sublessee's intention to terminate this Sublease Addendum in
      which case all consideration previously paid by Sublessee to Sublessor on
      account of this Sublease Addendum shall be returned to Sublessee, this
      Sublease Addendum shall thereafter be of no further force or effect, and
      Sublessor shall have no further liability to Sublessee on account of such
      delay or cancellation.

7.    RENT.

            Sublessee shall pay to Sublessor "Additional Basic Rent" of $5,000
      for April 2002, or any part thereof and $5,000 per month thereafter. Such
      Additional Basic Rent payments shall be without deduction, setoff, notice
      or demand, at 10182 Telesis I Court, Suite 600, San Diego, California,
      92121, or at such other place as Sublessor shall I designate from time to
      time by written notice to Sublessee. For the avoidance of doubt, the
      foregoing amount is in addition to the amounts required under the
      Sublease.

      In the event that the Lessor has not provided consent by April 19, 2002,
      then either the Sublessor or the Sublessee may cancel this Sublease
      Addendum without any further financial or legal obligation to the other
      party.

      For purposes of this Sublease Addendum, "Base Year" shall mean calendar
      year 2000, and Sublesee's "Additional Tenant's Percentage" shall be 2.1%.
      For the avoidance of doubt, the foregoing amount is in addition to the
      percentage under the Sublease. Sublessee's Additional Tenant's Percentage
      is determined by dividing 2,618 rentable square feet in the Additional
      Subleased Premises by 122,798, the rentable square feet of the Building
      and expressing the result as a percentage. (Both parties acknowledge that

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      such square footage is an only a rough estimate for purposes of cost
      allocation). Sublessee shall pay Sublessee's Tenant's Percentage of Direct
      Expenses and Utilities Costs in the same manner as set forth in, and
      pursuant to the terms of, Article 4 of the Master Lease. In no event shall
      Sublessee's obligation to pay Direct Expenses and Utilities Costs exceed
      Sublessee's Tenant's Percentage share of Direct Expenses and Utilities
      Costs due and payable by Sublessor under the Master Lease. Sublessee shall
      pay Sublessee's Tenant's Percentage of Direct Expenses and Utilities Costs
      as and when the same is due and payable to Lessor under the Master Lease
      and no earlier. Sublessee shall be entitled to its pro rata share of all
      credits, if any, given by Lessor to Sublessor for Sublessor's and/or
      Sublessee's overpayment of Direct Expenses and Utilities Costs. Sublessee
      shall be entitled to, and benefit from, any rental abatement granted
      Sublessor under the Master Lease for whatever reason to the extent that
      such abatement relates to the Additional Subleased Premises and the
      Sublease Addendum term. Sublessee shall be permitted to request
      after-hours air conditioning services, and the actual amounts for such
      services that are charged to Sublessor will be paid by Sublessee.

8.    MAINTENANCE.

      Sublessee shall have all maintenance obligations of the tenant under the
      Master Lease applicable to the Additional Subleased Premises. Sublessor
      shall have no maintenance or repair obligations with respect to the
      Additional Premises.

9.    PERSONAL PROPERTY.

      During the Term of the Sublease Addendum, Sublessee shall be allowed to
      use the items of personal property (e.g. furniture, etc.) currently
      located in the Additional Subleased Premises and as listed and described
      on Exhibit B. Sublessee shall keep all such items in good condition and
      repair and return same to Sublessor at the end of the Term, subject to
      ordinary wear and tear. Any modifications to such items shall be subject
      to the prior written approval of Sublessor; provided, however, that in the
      event any such modifications are approved, such items shall be returned to
      Sublessor at the end of the Sublease Addendum Term with such approved
      modifications intact. The parties agree that $374 of the monthly
      Additional Basic Rent shall be allocated to the lease of personal property
      referenced in this Section 9. For the avoidance of doubt, the foregoing
      amount is in addition to the amounts allocated under the Sublease.

10.   OTHER PROVISIONS OF SUBLEASE ADDENDUM.

      All applicable terms and conditions of the Master Lease are incorporated
      into and made a part of this Sublease Addendum as if Sublessor were the
      lessor thereunder, Sublessee the lessee thereunder, and the Additional
      Subleased Premises the Master Premises. Sublessee assumes and agrees to
      perform the lessee's obligations under the Master Lease during the Term to
      the extent that such obligations are applicable to the Additional
      Subleased Premises, except that the obligation to pay rent to Lessor under
      the Master Lease shall be considered performed by Sublessee to the extent
      and in the amount rent is paid to Sublessor in accordance with Section 7
      of this Sublease Addendum. The parties agree that the Waiver of
      Subrogation set forth in Section 22(i) shall apply as between

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      Sublessor and Sublessee notwithstanding anything to the contrary in the
      Sublease Addendum, Sublease or Master Lease. Sublessee shall not commit or
      suffer any act or omission that will violate any of the provisions of the
      Master Lease. Sublessor shall exercise due diligence in attempting to
      cause Lessor to perform its obligations under the Master Lease for the
      benefit of Sublessee. If the Master Lease terminates for any reason other
      than a default by Sublessor as Tenant under the Master Lease, Sublease, or
      this Sublease Addendum shall terminate and the parties shall be relieved
      of any further liability or obligation under this Sublease Addendum. If
      the Master Lease terminates for a default by Sublessor as Tenant under the
      Master Lease, Sublease, or this Sublease Addendum shall terminate except
      as otherwise agreed to by Lessor and Sublessee, and Sublessor shall not be
      relieved of any liability or obligation under this Sublease Addendum.
      Notwithstanding the foregoing, if the Master Lease gives Sublessor any
      right to terminate the Master Lease in the event of the partial or total
      damage, destruction, or condemnation of the Master Premises or the
      building or project of which the Master Premises are a part, the exercise
      of such right by Sublessor shall not constitute a default or breach
      hereunder. If Lessor seeks to terminate the Master Lease because of a
      default or alleged default by Sublessor under the Master Lease, Sublessor
      shall use its reasonable good faith efforts to maintain the Master Lease
      in full force and effect for the benefit of Sublessee and Sublessor and to
      reinstate the Master Lease and/or to claim and pursue any right of
      redemption or relief from forfeiture of the Master Lease (and as a
      consequence thereof any forfeiture of the Sublease Addendum) to which
      Sublessor may be entitled at law or in equity. Any breach of this Sublease
      Addendum will be considered a breach of the Sublease and any breach of the
      Sublease will be considered a breach of this Sublease Addendum.

11.   NONAPPLICABLE MASTER LEASE PROVISIONS.

      Notwithstanding Section 10 above, (a) the following sections of the Master
      Lease shall not apply under this Sublease Addendum: In the Summary of
      Basis Lease Information: Section 1.2 (Tenant's Address); Section 1.5
      (Premises); Section 1.6 (Term); Section 1.7 (Estimate of Commencement
      Date); Section 1.8 (Monthly Basic Rent); Section 1.9 (Tenant's
      Percentage); Section 1.10 (Base Year); Section 1.11 (Security Deposit);
      Section 1.13 (Tenant Improvements); Section 1.15 (Parking with respect to
      exclusive spaces only); in the Master Lease itself: Section 1.4 (Suite
      400) Article 2 (Term); Article 3.1 (with respect to the amount of Basic
      Rent); Section 4.4(g) (first sentence only); Section 5.1 (first and last
      sentence only); Section 5.2(a) (first sentence only); Section 5.2(b)
      (Letter of Credit amount); Section 6.3(a); Section 7 (only with respect to
      specified addresses); Section 8; Section 12.5; Section 12.6; Section 31
      (second sentence only); Article 34 (Right of First Refusal); Article 35
      (Temporary Space); Article 36 (Option Term); Exhibit B, Exhibit C (Work
      Letter Agreement) and Exhibit D; (b) references in the following
      provisions to "Landlord" shall mean Lessor only: in the Summary of Basic
      Lease Information: Section 1.1; in the Master Lease itself: Sections 1.2;
      1.3; 4.2; 4.4(c); 4.4(d); 4.4(e); 4.6; 4.7 (Tenant's Audit Rights); 6.2;
      11.2; 12.1(c) (second to last sentence only); 12.1(d); Article 18; Article
      19; Article 25; Section 28.1; and Article 30; and Exhibit E.;.
      Notwithstanding Section 14 of the Master Lease, a sale or transfer of

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      Sublessee's capital stock shall not be deemed an assignment, subletting or
      any other transfer of the Sublease Addendum or the Additional Subleased
      Premises.

12.   SIGNAGE AND PARKING.

      Sublessee and Sublessor will mutually agree in good faith on acceptable
      signage for both parties in the shared sixth floor reception areas and
      lobby signage (subject to the consent of Lessor). Any other signage of
      Sublessee will be as Sublessee and Lessor may mutually agree. Sublessee
      shall have use of 5 parking spaces per Section 1.16 of the Master Lease,
      subject to the other parking provisions of the Master Lease. For the
      avoidance of doubt, the foregoing parking space allotment is in addition
      to the parking space allotment under the Sublease.

13.   ATTORNEYS' FEES.

      If Sublessor or Sublessee shall commence legal action against the other
      arising out of or in connection with this Sublease Addendum, the
      prevailing party shall be entitled to recover its costs of suit and
      reasonable attorneys' fees.

14.   AGENCY DISCLOSURE.

      Sublessor and Sublessee each warrant that they have dealt with no real
      estate broker finders, agents or salesmen in connection with this
      transaction. Each party agrees to hold the other party harmless from and
      against all claims for brokerage commissions, finder's fees or other
      compensation made by any other agent, broker, salesman or finder as a
      consequence of such party's actions or dealings with such agent, broker,
      salesman or finder.

15.   COMMISSION.

      Neither Sublessee nor Sublessor has any obligation to pay any commission
      to any third party in connection with this Sublease Addendum.

16.   NOTICES.

      All notices and demands, which may or are to be required or permitted to
      be given by either party on the other hereunder shall be in writing. All
      notices and demands by the Sublessor to Sublessee shall be hand delivered
      or sent by nationally recognized overnight courier to the Sublessee at the
      Additional Subleased Premises, or to such other place as Sublessee may
      from time to time designate in a notice to the Sublessor. All notices and
      demands by the Sublessee to Sublessor shall be hand delivered or sent by
      nationally recognized overnight courier to the Sublessor at the address
      set forth above in Section 7, and to such other person or place as a the
      Sublessor may from time to time designate in a notice to the Sublessee.

17.   CONSENT BY LESSOR.

      THIS SUBLEASE ADDENDUM AND SUBLESSOR'S AND SUBLESSEE'S OBLIGATIONS
      HEREUNDER ARE CONDITIONED UPON THE WRITTEN

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      CONSENT OF LESSOR IN FORM AND SUBSTANCE SATISFACTORY TO SUBLESSEE AND
      SUBLESSOR AND THIS SUBLEASE ADDENDUM SHALL BE OF NO FORCE OR EFFECT UNLESS
      CONSENTED TO BY LESSOR, ON OR BEFORE APRIL 19, 2002.

Upon receipt of notice that Lessor has consented to the Sublease Addendum,
Sublessor shall promptly inform Sublessee that such consent has been obtained
so that Sublessee may make arrangement with respect to any work that needs to be
done to the Additional Subleased Premises as part of Sublessee's relocation
thereto.

18.   MUTUAL NO-HIRE.

Throughout the Sublease Addendum Term, neither Sublessor nor Sublessee shall
solicit for employment the employees of the other party.

20.   MISCELLANEOUS.

Should any provision of this Sublease Addendum be invalid, illegal or
unenforceable, the remaining provisions will continue as valid, legal and
enforceable. This Sublease Addendum and the Sublease constitute the entire
agreement between the parties with respect to its subject matter. No oral
modification or waiver of any provision of this Sublease Addendum will be
binding on either party. Any failure of either party to enforce this Sublease
Addendum as to any breach by the other party will not be deemed to be a waiver.
In the event that the Master Lease is terminated and Lessor recognizes the
Sublease Addendum, upon the written request of Sublessee, Sublessor shall
promptly transfer the security deposit and letter of credit to Lessor, provided
that Sublessee is not then in default under this Sublease Addendum.

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In witness whereof the parties below enter into this Agreement as of the dates
first above written.

SUBLESSOR: WEBSIDESTORY, INC.                    SUBLESSEE: AVEXUS, INC.,
a Delaware corporation '                         a Delaware Corporation

By: /s/ John J. Hentrich                         By: /s/ Jim L. Temple

Name: John J. Hentrich                           Name: Jim L. Temple

Title: President & CEO                           Title: Vice President, Finance

Date: April 8, 2002                              Date: 4/08/02

CONSENT OF LESSOR:

By:

Name:

Title:

Date:

     [Signature Page to Sublease Addendum Agreement for 10182 Telesis Court
                                   Suite 400]

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                                    EXHIBIT A

                                  [FLOOR PLAN]

WEBSIDE STORY

6TH FLOOR @ SEAVIEW CORPORATE CENTER

                                AREA SUMMARY

<TABLE>
<S>                                       <C>
VERTICAL SHAFTS                              909 S.F.
(STAIRS/ELEV./SHAFTS)

COMMON AREA                                2,349 S.F.
(RESTROOMS/ELEV. LOBBY/CORRIDOR)

USABLE                                    15,545 S.F.
(AREAS #1-#9)
-----------------------------------------------------
TOTAL                                     18,803 S.F.
</TABLE>

<PAGE>

                                    EXHIBIT B

                          Listing of Personal Property

Each of the seven offices are equipped with desks. No other furniture is located
in the offices.