<PAGE>

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS,
HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.


                                                                   EXHIBIT 10.41
December 14, 2001

Amgen Inc. ("Amgen")
One Amgen Center Drive
Building 29
Thousand Oaks, CA 91320
Attention:  Philip Tagari
Associate Director, Research

RE:  AMENDMENT TO TECHNOLOGY ACCESS AGREEMENT

Dear Phil:

        Further to our recent conversations, this Letter Amendment (the
"Amendment") sets forth certain changes that the parties wish to make to the
Technology Access Agreement between Caliper and Amgen dated December 21, 1998
(the "Original Agreement"). Capitalized terms used herein but not defined shall
have the meaning ascribed to them in the Original Agreement.

        1.      CREDITS FOR CERTAIN FEES DUE UNDER THE ORIGINAL AGREEMENT.

                a.      General. The parties acknowledge that the HTS
                        enterprises under the Original Agreement have evolved
                        from their focus on early product development and access
                        to a later-stage commercial relationship involving
                        commercial sales of standard HTS products by Caliper. In
                        light of this evolution, Caliper agrees to convert the
                        final [ * ] in fees paid by Amgen pursuant to the
                        Original Agreement into credits toward the purchase of
                        Caliper HTS products and services, subject to the terms
                        and conditions of this Amendment.

                b.      Purchase Credit for Past Fees. The credit set forth in
                        Section 1(a) shall be utilized by Amgen to purchase one
                        demonstration model Caliper 250 Fluorogenic and Mobility
                        Shift Screening System at an additional [ * ] discount
                        pursuant to a purchase order placed with Caliper on or
                        before December 19, 2001. Amgen agrees to accept such
                        instrument prior to the end of 2001.

                c.      Additional Instrument Terms. In consideration for
                        allowing Amgen to purchase the demonstration model at a
                        discounted price as set forth in Section 1(b) above,
                        Amgen shall, upon request from Caliper at any time
                        before June 30, 2002, return to Caliper the Caliper 220
                        currently in Amgen's possession. Caliper shall upgrade
                        the Caliper 250 instrument set forth in subsection 1(b)
                        above with multiport pressure capability [ * ] when such
                        functionality becomes commercially available. In
                        addition, Caliper


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

<PAGE>




                        shall extend the warranty for the two (2) Caliper 110
                        instruments currently in Amgen's possession through
                        December 31, 2002 at [ * ]. Caliper shall continue to
                        manufacture Chips and reagents for the Caliper 110 for
                        sale to Amgen.

        2.      PURCHASE TERMS FOR COMMERCIALLY AVAILABLE PRODUCTS. From the
                date this Amendment is executed by both parties until [ * ],
                Caliper agrees to provide the following discounts or prices to
                Amgen. Caliper's standard list prices as of the date of this
                letter are set forth in Exhibit A.

                a.      Except as set forth in Section 1(b) above, [ * ] off the
                        list price of Caliper's commercially released HTS
                        instruments set forth in Caliper's then-current product
                        catalog at the time of purchase;

                b.      All services other than standard field service for
                        commercially released HTS instruments, including but not
                        limited to HTS assay development services and custom
                        project development services, will be provided at a
                        [ * ] discounted rate of [ * ] per Caliper FTE per year,
                        or [ * ]/hour.

                c.      Amgen shall pay for datapoints as set forth in that
                        certain Datapoint Pricing Agreement dated December 17,
                        2001. Amgen shall pay list price for Caliper's
                        microfluidic chips.

                d.      No Multiple Discounts. Except as set forth in Section
                        1(b) above, in the event that more than one discount may
                        apply to a particular item under this Amendment, other
                        agreements between the parties or pursuant to Caliper's
                        standard commercial practices (including volume
                        discounts), Amgen may choose which discount to apply but
                        may not combine discounts.

        3.      SERVICES.

                a.      FTEs. Caliper shall provide to Amgen one-half (1/2) of
                        an FTE during calendar year 2002 for LabChip Assay
                        development as requested by Amgen, subject to Section
                        3(b) below, and pursuant to the terms of Sections 4 and
                        5 of the Original Agreement, which are hereby
                        incorporated herein by reference for the purpose of
                        governing development activities by such FTE.

                b.      Library Card Project. Caliper shall provide to Amgen
                        updates on a calendar quarter basis regarding the status
                        of Caliper's development of a library card (the
                        "Project"), provided that Caliper does not guarantee any
                        particular result for, or continuation of, the Project.
                        In the event that Caliper requests certain compounds
                        from Amgen for use in the Project, Amgen shall provide
                        such compounds to Caliper free of charge, and shall
                        inform Amgen of any data obtained during the Project
                        from the use of such compounds. If Amgen requests that
                        such compounds be tested against a particular target,
                        then Caliper may, in its sole discretion, perform such
                        testing and inform


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

<PAGE>

                        Amgen of the results, provided that Caliper may use the
                        FTE time set forth in Section 3(a) of this Amendment to
                        perform such testing.

        4.      AMENDMENT OF SECTION 8.4 OF ORIGINAL AGREEMENT. Section 8.4 of
                the Original Agreement is hereby amended and restated as
                follows:

                        "SURVIVING OBLIGATIONS. No expiration or termination of
                this Agreement shall relieve either party of any obligation
                accruing prior to such expiration or termination. The provisions
                of Sections 2.1(a) (third and fourth sentences), 2.1(b), 2.1(c)
                (except as such subsection relates to 3.3(c)), 2.1(d), 2.4, 2.5,
                2.7, 3.1(b)(i), 4, 5, 7, 8.4, 8.5 and 9 shall survive the
                expiration or termination of this Agreement."

        5.      MATERIALS. In the event that Amgen transfers any Materials to
                Caliper hereunder, the terms of Section 4.3 of the Original
                Agreement, which is hereby incorporated herein by reference,
                shall apply to such transfer. Caliper understands that any Amgen
                compounds transferred will not be subject to attempts for
                structural elucidation without the prior written consent of
                Amgen.

        6.      TERM. Except as set forth herein, the terms of the Original
                Agreement shall remain in full force and effect. The terms of
                this Amendment shall survive beyond the scheduled expiration of
                the Original Agreement on December 21, 2001, to the extent and
                for the duration expressly provided in this Amendment. This
                Amendment shall not otherwise extend the term of the Original
                Agreement in any manner.

Please indicate Amgen's agreement to the foregoing terms by signing below where
indicated.

Sincerely,

CALIPER TECHNOLOGIES CORP.

By: /s/ Daniel Kisner
    ------------------------------
    Name: Daniel L. Kisner
    Title: CEO

ACCEPTED AND AGREED:

AMGEN INC.

By: /s/ Nick Lydon
    ------------------------------
    Name: Nick Lydon
    Title: VP Small Molecule Drug Discovery
    Date:  17 December 2001


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

<PAGE>

                                    EXHIBIT A

                               HTS PRODUCT CATALOG
                            (AS OF DECEMBER 10, 2001)

<TABLE>
<CAPTION>
PRODUCT                                                                   PRICE
<S>                                                                     <C>
CALIPER 250 CORE SYSTEM                                                 $285,000
-2-CCD Detection
-Blue and Red excitation lasers
-16V+1P Power and Pressure
Controller
-Computer System
-X-Y-Z robot system w/controller
-Next Gen Instrument Control and
Data Acquisition Software
-Includes 3 Training Credits
-1 Year Warranty, First Year
On-site Service and Software Updates

OPTION 1*: ENVIRONMENTAL CONTROL                                        $ 92,000
AND MULTI-PLATE HANDLING
-Temperature and Humidity Control
Unit
-Twister Plate Handler and Barcode
Unit

OPTION 2*: ADDITION OF UV                                               $ 55,000
EXCITATION AND DETECTION
-355nM Excitation and Detection

ANALYSIS SOFTWARE
-Fluorogenic Analysis Module                                            $ 28,750
-Off-Chip Mobility Shift Analysis                                       $ 28,750
Module

ASSAY CHIPS**
-4-Sipper Off-Chip Mobility Shift                                       $    250
Chip
-4-Sipper Fluorogenic Chip                                              $    250


SYSTEM                                                                     PRICE

MOBILITY SHIFT AND FLUOROGENIC
SCREENING SYSTEM
-Caliper 250 Core System                                                $285,000
-Option 1*: Environmental Control and                                   $ 92,000
Multi-Plate Handling
-Option 2*: Addition of UV Excitation                                   $ 55,000
and Detection
-Fluorogenic Analysis Module                                            $ 28,750
-Off-Chip Mobility Shift Analysis                                       $ 28,750
Module

                                 TOTAL                                  $489,500

MOBILITY SHIFT SCREENING SYSTEM
-Caliper 250 Core System                                                $285,000
-Option 1*: Environmental Control and                                   $ 92,000
Multi-Plate Handling
-Off-Chip Mobility Shift Analysis                                       $ 28,750
Module
                                 TOTAL                                  $405,750

MOBILITY SHIFT AND FLUOROGENIC DEVELOPMENT SYSTEM
-Caliper 250 Core System                                                $285,000
-Option 2*: Addition of UV Excitation                                   $ 55,000
and Detection
-Fluorogenic Analysis Module                                            $ 28,750
-Off-Chip Mobility Shift Analysis                                       $ 28,750
Module
                                 TOTAL                                  $397,500

MOBILITY SHIFT DEVELOPMENT SYSTEM
-Caliper 250 Core System                                                $285,000
-Off-Chip Mobility Shift Analysis                                       $ 28,750
Module
                                 TOTAL                                  $313,750
</TABLE>


[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

<PAGE>

                              EXHIBIT B (CONTINUED)

<TABLE>
<S>                                                                             <C>
CUSTOMER SUPPORT AND SERVICE

ASSAY DEVELOPMENT SERVICE                                                       $250/HR.
-Development of Assay Conditions for Standard Fluorogenic or
Mobility Shift Assay.

TRAINING COURSES
-Assay Development Training Course:  Fluorogenic (3 days)                       $2000/PERSON
-Assay Development Training Course:  Off-Chip Mobility Shift (3 days)           $2000/PERSON
-Instrument Training Course: (2 days)                                           $1500/PERSON

ANNUAL MAINTENANCE CONTRACT                                                     12% OF
                                                                                SYSTEM PRICE

(SW Updates, Annual Calibration, On-Site Service, Extended Warranty, Laser
Replacements not included)

*INSTALLATION OF HARDWARE UPGRADES TO SYSTEMS AFTER PURCHASE                    20% OF HW
                                                                                 UPGRADE
</TABLE>

** ASSAY CHIPS ARE ONLY AVAILABLE TO CUSTOMERS AT THESE PRICES AFTER EXECUTION
OF DATAPOINT PRICING AGREEMENT.



[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.