Document:

<PAGE>   1
                                                                   EXHIBIT 10.20

                                 AMENDMENT #14

AMENDMENT NUMBER #14 TO THAT LEASE DATED SEPTEMBER 10, 1991 BETWEEN SPIEKER
PROPERTIES, L.P., AS LANDLORD, AND SCICLONE PHARMACEUTICALS, INC., AS TENANT
(THE "LEASE"), FOR PREMISES LOCATED AT 901 MARINER'S ISLAND BOULEVARD, SAN
MATEO, CALIFORNIA.

Effective December 1, 2000, the Lease will be amended as follows to provide for
Tenant's expansion premises and terminated premises:

1.      PREMISES. Effective December 1, 2000, the parties hereto desire to
        terminate the Lease only with respect to that portion of the Premises,
        located on the second floor and known as Suite 200, consisting of
        approximately 935 square feet of rentable area as shown outlined in red
        on the attached floor plan (Exhibit B - Suite 200).

        Effective January 1, 2001, the term "Premises" as used in the Lease is
        therefore amended to mean approximately 16,748 square feet of rentable
        area (which includes a portion of the building common area) located on
        the first and second floors of the building known as 901 Mariner's
        Island Boulevard. The Premises as expanded herein are approximately as
        shown outlined in red on the attached floor plan (Exhibit B-1 - Suite
        170, Suite 205, Suite 235, Suite 245 and Suite 285).

        Effective March 1, 2001 or unless sooner terminated by Landlord and
        Tenant, the parties hereto desire to terminate the Lease only with
        respect to that portion of the Premises, located on the first floor and
        known as Suite 170, consisting of approximately 1,980 square feet of
        rentable area as shown outlined in red on the attached floor plan
        (Exhibit B-2 - Suite 170).

2.      OCCUPANCY DENSITY.  4 people per 1000 square feet.

3.      RENT. Base Rent for the Premises as expanded herein shall be as follows:

<TABLE>
<CAPTION>

       <S>                       <C>
       12/01/00 - 12/31/00:      Forty thousand seven hundred sixty one and 00/100ths
       (Suite 200 terminated     dollars ($40,761.00) per month plus operating expenses per
       12/1/00)                  Paragraph 29 of the Lease.  Operating expenses through
                                 December, 2000 are estimated to be $7,193.00
                                 per month. Direct operating expenses are
                                 estimated a year in advance and collected on a
                                 monthly basis. Any adjustments necessary (up or
                                 down) will be made at the end of the operating
                                 year.

       01/01/01 - 02/29/01:      Eighty Six Thousand Four Hundred Forty Four and 00/100ths
                                 dollars (86,444.00) per month plus operating expenses per
                                 Paragraph 29 of the Lease.

       03/01/01 - 08/31/01:      Seventy Seven Thousand Six Hundred Ninety Two and 00/100ths
       (Suite 170 terminated     dollars ($77,692.00) per month plus operating expenses per
       2/29/01)                  Paragraph 29 of the Lease.

       09/01/01 - 12/31/01:      Seventy Eight Thousand Nine Hundred Ninety Six and
                                 00/100ths dollars ($78,996.00) per month plus
                                 operating expenses per Paragraph 29 of the
                                 Lease.

       01/01/02 - 08/31/02:      Eighty Thousand Three Hundred Fifty One and 00/100ths
                                 dollars ($80,351.00) per month plus operating expenses per
                                 Paragraph 29 of the Lease.

</TABLE>

<PAGE>   2

       09/01/02 - 12/31/02:      Eighty One Thousand Seven Hundred Twenty Seven
                                 and 00/100ths dollars ($81,727.00) per month
                                 plus operating expenses per Paragraph 29 of the
                                 Lease.

       01/01/03 - 08/31/03:      Eighty Three Thousand One Hundred Fifty Seven
                                 and 00/100ths dollars ($83,157.00) per month
                                 plus operating expenses per Paragraph 29 of the
                                 Lease.

       09/01/03 - 12/31/03:      Eighty Four Thousand Six Hundred Five and
                                 00/100ths dollars ($84,605.00) per month plus
                                 operating expenses per Paragraph 29 of the
                                 Lease.

       01/01/04 - 08/31/04:      Eighty Six Thousand Thirty Five and 00/100ths
                                 dollars ($86,035.00) per month plus operating
                                 expenses per Paragraph 29 of the Lease.

       09/01/04 - 12/31/04:      Eighty Seven Thousand Four Hundred Eighty Three
                                 and 00/100ths dollars ($87,483.00) per month
                                 plus operating expenses per Paragraph 29 of the
                                 Lease.

       01/01/05 - 08/31/05:      Eighty Eight Thousand Nine Hundred Eighty Nine
                                 and 00/100ths dollars ($88,989.00) per month
                                 plus operating expenses per Paragraph 29 of the
                                 Lease.

       09/01/05 - 12/31/05:      Ninety Thousand Three Hundred Sixty Five and
                                 00/100ths dollars ($90,365.00) per month plus
                                 operating expenses per Paragraph 29 of the
                                 Lease.

       01/01/06 - 8/31/06:       Ninety One Thousand Nine Hundred Forty Five and
                                 00/100ths dollars ($91,945.00) per month plus
                                 operating expenses per Paragraph 29 of the
                                 Lease.

       09/01/06 - 12/31/06:      Ninety Three Thousand Three Hundred Twenty One
                                 and 00/100ths dollars ($93,321.00) per month
                                 plus operating expenses per Paragraph 29 of the
                                 Lease.

       01/01/07 - 08/31/07:      Ninety Four Thousand Nine Hundred One and
                                 00/100ths dollars ($94,901.00) per month plus
                                 operating expenses per Paragraph 29 of the
                                 Lease.

4.      SECURITY DEPOSIT The Letter of Credit ("LC") of $316,898.00 under the
        Lease shall be increased by $316,092.00 for a total of $632,990.00 ("LC
        Amount"). The LC shall be delivered to Landlord within forty-five (45)
        days of the commencement date of this Amendment #14 and shall be in
        accordance with Paragraph 5 of Amendment #13 of the Lease.

5.      TENANT'S PROPORTIONATE SHARE Effective December 1, 2000, Tenant's
        proportionate share shall be 7.75%. Effective January 1, 2001, Tenant's
        proportionate share shall be 14.06%. Effective March 1, 2001 or upon the
        termination of Suite 170 if earlier, Tenant's proportionate share shall
        be 12.39%.

6.      TENANT IMPROVEMENTS Tenant agrees to accept the Premises as so expanded
        in "as is" condition. Provided Tenant is not in default of the Lease,
        Landlord shall contribute a one time tenant improvement allowance not to
        exceed $22,578.00 toward the cost of initial tenant improvements. Tenant
        shall not perform any work in the Premises (including, without
        limitation, cabling, wiring, fixturization, painting, carpeting,
        replacements or repairs) except in accordance with Paragraphs 7 and 9 of
        the Lease.

<PAGE>   3

7.      SUBLETTING During the first thirty six (36) months of the Term of this
        Lease, provided that Tenant is not in default of the Lease, Tenant shall
        have the right to sublease the 2,557 square foot portion of the Premises
        on the second floor, known as Suite 285, with prior written Landlord's
        consent, from time to time, to one subtenant at a time provided that the
        term of such proposed sublease shall not exceed thirty six (36) months
        and no extension options shall be granted in such sublease, without
        extending any option to Landlord to recapture or terminate the Lease as
        to such portion of the Premises, and as otherwise in accordance with
        Paragraph 10 of the Lease.

All other terms and conditions of the Lease shall remain in full force and
effect and shall apply to the Premises as well as to the original premises.

Dated: November 21, 2000

IN WITNESS WHEREOF, the parties hereto have executed this Amendment #14 as of
the day and year first above written.

LANDLORD:

SPIEKER PROPERTIES, L.P.,
a California limited partnership

By:     Spieker Properties, Inc.,
        a Maryland corporation,
        its general partner

        By:
           ----------------------
             Nancy Gille
        Its: Vice President
            ---------------------

TENANT:

SCICLONE PHARMACEUTICALS, INC.
A California Corporation

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

        Its:
            ---------------------<PAGE>   1
                                                                   EXHIBIT 10.31

CONFIDENTIAL TREATMENT - EDITED COPY

                          REGISTRATION RIGHTS AGREEMENT

        REGISTRATION RIGHTS AGREEMENT, dated as of February 16, 2001, by and
between SciClone Pharmaceuticals, Inc., a California corporation (the
"Company"), and UBS AG, London Branch (the "Purchaser") entered into in
connection with the issuance of (i) 6% Convertible Note due 2006 convertible
into shares of Common Stock, no par value ("Common Stock"), of the Company
pursuant to the Purchase Agreement referred to below and (ii) option to purchase
Zero Coupon Convertible Note due 2005 convertible into shares of Common Stock of
the Company pursuant to the Option Agreement referred to below.

        1. Certain Definitions. For purposes of this Registration Rights
Agreement, the following terms shall have the following respective meanings:

               (a) "Commission" shall mean the Securities and Exchange
Commission, or any other federal agency at the time administering the Exchange
Act or the Securities Act, whichever is the relevant statute for the particular
purpose.

               (b) "Convertible Note" shall mean the 6% Convertible Note due
2006 of the Company to be issued and sold to the Purchaser pursuant to the
Purchase Agreement, and the Zero Coupon Convertible Note due 2006 of the Company
that may be issued pursuant to the Option Agreement, and any Convertible Note
issued in exchange therefor or in lieu thereof.

               (c) "Effective Time" shall mean the date on which the Commission
declares the Shelf Registration effective or on which the Shelf Registration
otherwise becomes effective.

               (d) "Exchange Act" shall mean the Securities Exchange Act of
1934, or any successor thereto, as the same shall be amended from time to time.

               (e) "Initial Note" means the $4,000,000 principal amount of
Convertible Note issued pursuant to the Purchase Agreement.

               (f) "Issue Date" shall mean the date on which a Convertible Note
is initially issued.

               (g) "Option Agreement" means the Option Agreement of even date
herewith between the Company and the Purchaser.

               (h) "Option Note" means the Convertible Note, if any, issued
pursuant to the Option Agreement.

               (i) The term "person" shall mean a corporation, association,
partnership, organization, business, individual, government or political
subdivision thereof or governmental agency.

               (j) "Purchase Agreement" means the Convertible Note Purchase
Agreement of even date herewith between the Company and the Purchaser.

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CONFIDENTIAL TREATMENT - EDITED COPY

               (k) "Registrable Securities" means any Shares, Option Note or
shares of Common Stock issuable in lieu thereof subject to registration under
the Securities Act pursuant to this Agreement.

               (l) "Registration Expenses" shall have the meaning assigned
thereto in Section 4 hereof.

               (m) "Securities Act" shall mean the Securities Act of 1933, or
any successor thereto, as the same shall be amended from time to time.

               (n) "Shares" means the shares of Common Stock issuable upon
exercise of the Convertible Note.

               (o) "Shelf Registration" shall have the meaning assigned thereto
in Section 2 hereof.

        In addition, capitalized terms not defined herein shall have the meaning
ascribed in the Convertible Note.

        2. Shelf Registration of Shares; Other Registrations.

               (a) Not later than February 16, 2002, the Company shall file
under the Securities Act a "shelf" registration statement providing for the
registration of, and the sale on a continuous or delayed basis by the Purchaser
of, all Shares issuable upon conversion of the Initial Note, pursuant to Rule
415 under the Securities Act and/or any similar rule that may be adopted by the
Commission (the "Shelf Registration"). The Company agrees to use its
commercially reasonable efforts to cause the Shelf Registration to become or be
declared effective no later than 45 calendar days after the filing thereof and
to keep such Shelf Registration continuously effective for a period ending on
the earliest to occur of (i) the second anniversary of the latest Issue Date of
any Initial Note, (ii) notification to the Company by the Purchaser that it has
sold all Shares issuable upon conversion of the Initial Note so owned by it, or
(iii) such time as the Purchaser may sell all of such Shares pursuant to Rule
144(k) under the Securities Act. The Company further agrees, if necessary, to
supplement or make amendments to the Shelf Registration, if required by the
rules, regulations or instructions applicable to the registration form used by
the Company for such Shelf Registration or by the Securities Act or rules and
regulations thereunder for shelf registration, and the Company agrees to furnish
to the Purchaser a copy of any such supplement or amendment prior to its being
used and/or filed with the Commission, and will not file any such supplement or
amendment to which the Purchaser reasonably objects.

               (b) Notwithstanding the foregoing, following the effectiveness of
the Shelf Registration, the Company may, at any time, suspend the effectiveness
of such Shelf Registration for up to 60 days, as appropriate (a "Suspension
Period"), by giving notice to the Purchaser, if the Company shall have
determined that the Company may be required to disclose any material corporate
development which disclosure may have a material adverse effect on the Company.
The Company will use its commercially reasonable efforts to minimize the length
of any Suspension Period. Notwithstanding the foregoing, no more than one
Suspension Period may occur within any 180 day period. The Purchaser agrees
that, upon receipt of any notice from the

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CONFIDENTIAL TREATMENT - EDITED COPY

Company of a Suspension Period, the Purchaser shall forthwith discontinue
disposition of shares covered by the Shelf Registration until the Purchaser (i)
is advised in writing by the Company that the use of the applicable prospectus
may be resumed, (ii) has received copies of a supplemental or amended
prospectus, if applicable, and (iii) has received copies of any additional or
supplemental filings which are incorporated or deemed to be incorporated by
reference in such prospectus.

               (c) Not later than the earlier of (a) September __, 2005 or (b)
30 days after any issuance of the Option Note, or shares of Common Stock in lieu
thereof pursuant to the Option Agreement, the Company shall file under the
Securities Act a "shelf" registration statement providing for the registration
of, and the sale on a continuous or delayed basis by the Purchaser of, the
Option Note, any Shares issuable upon conversion thereof or in payment thereof,
and/or shares of Common Stock issued in lieu thereof, pursuant to Rule 415 under
the Securities Act and/or any similar rule that may be adopted by the
Commission. The Company agrees to use its commercially reasonable efforts to
cause such shelf registration to become or be declared effective no later than
30 calendar days after the required filing date thereof and to keep such shelf
registration continuously effective for a period ending on the earliest to occur
of (i) the 180th day after such issuance of the Option Note or shares of Common
Stock in lieu thereof, (ii) notification to the Company by the Purchaser that it
has sold all the Option Note or shares of Common Stock so owned by it, or (iii)
such time as the Purchaser may sell all of the Option Note or shares of Common
Stock pursuant to Rule 144(k) under the Securities Act. The Company further
agrees, if necessary, to supplement or make amendments to the such shelf
registration statement, if required by the rules, regulations or instructions
applicable to the registration form used by the Company for such shelf
registration or by the Securities Act or rules and regulations thereunder for
shelf registration, and the Company agrees to furnish to the Purchaser a copy of
any such supplement or amendment prior to its being used and/or filed with the
Commission, and will not file any such supplement or amendment to which the
Purchaser reasonably objects.

        3. Registration Procedures.

               (a) In connection with any obligation of the Company to register
the Registrable Securities, the Company shall use its commercially reasonable
efforts to effect or cause such registration to permit the sale of the
Registrable Securities by the Purchaser in accordance with the intended method
or methods of distribution thereof described in the applicable registration
statement. In connection therewith, the Company shall, within the time specified
in Section 2 above:

                      (i) prepare and file with the Commission a registration
statement on any form which may be utilized by the Company and which shall
permit the disposition of the Registrable Securities in accordance with the
intended method or methods thereof, as specified in writing by the Purchaser;

                      (ii) comply with the provisions of the Securities Act with
respect to the disposition of all of the Registrable Securities covered by such
registration statement in accordance with the intended methods of disposition by
the Purchaser set forth in such registration statement;

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CONFIDENTIAL TREATMENT - EDITED COPY

                      (iii) provide (A) the Purchaser, (B) the underwriters
(which term, for purposes of this Agreement, shall include a person deemed to be
an underwriter within the meaning of Section 2(a)(11) of the Securities Act), if
any, thereof, (C) the sales or placement agent, if any, therefor, (D) counsel
for such underwriters or agent, and (E) one counsel for the Purchaser the
opportunity to participate in the preparation of such registration statement,
each prospectus included therein or filed with the Commission, and each
amendment or supplement thereto;

                      (iv) for a reasonable period prior to the filing of such
registration statement, and throughout the period specified in Section 2 hereof,
make available for inspection by the parties referred to in Section 3(a)(iii)
above who shall certify to the Company that they have a current intention to
sell the Registrable Securities pursuant to the registration statement such
financial and other information and books and records of the Company, and cause
the officers, employees, counsel and independent certified public accountants of
the Company to respond to such inquiries, as shall be reasonably necessary, in
the judgment of the respective counsel referred to in such Section, to conduct a
reasonable investigation within the meaning of Section 11 of the Securities Act;
provided, however, that each such party shall be required to maintain in
confidence and not to disclose to any other person any information or records
provided by the Company until such time as (A) such information becomes a matter
of public record (whether by virtue of its inclusion in such registration
statement or otherwise), or (B) such person shall be required so to disclose
such information pursuant to the subpoena or order of any court or other
governmental agency or body having jurisdiction over the matter (subject to the
requirements of such order, and only after such person shall have given the
Company prompt prior written notice of such requirement), or (C) such
information is required to be set forth in such registration statement or the
prospectus included therein or in an amendment to such registration statement or
an amendment or supplement to such prospectus in order that such registration
statement, prospectus, amendment or supplement, as the case may be, does not
contain an untrue statement of a material fact or omit to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading;

                      (v) promptly notify the Purchaser, the sales or placement
agent, if any, therefor and the managing underwriter or underwriters, if any,
thereof and confirm such advice in writing, (A) when such registration statement
or the prospectus included therein or any prospectus amendment or supplement or
post-effective amendment has been filed, and, with respect to such registration
statement or any post-effective amendment, when the same has become effective,
(B) of any comments by the Commission and by the Blue Sky or securities
commissioner or regulator of any state with respect thereto or any request by
the Commission for amendments or supplements to such registration statement or
prospectus or for additional information, (C) of the issuance by the Commission
of any stop order suspending the effectiveness of such registration statement or
the initiation or overt threatening of any proceedings for that purpose, (D) if
at any time the representations and warranties of the Company contemplated by
Section 5 hereof cease to be true and correct in all material respects, (E) of
the receipt by the Company of any notification with respect to the suspension of
the qualification of the Registrable Securities for sale in any jurisdiction or
the initiation or overt threatening of any proceeding for such purpose, or (F)
at any time when a prospectus is required to be delivered under the Securities
Act, if such registration statement, prospectus, prospectus amendment or
supplement or post-effective amendment, or any document incorporated by

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CONFIDENTIAL TREATMENT - EDITED COPY

reference in any of the foregoing, contains an untrue statement of a material
fact or omits to state any material fact required to be stated therein or
necessary to make the statements therein not misleading in light of the
circumstances then existing;

                      (vi) use its best efforts to obtain the withdrawal of any
order suspending the effectiveness of such registration statement or any
post-effective amendment thereto at the earliest practicable date;

                      (vii) if requested by any managing underwriter or
underwriters, any placement or sales agent or the Purchaser, promptly
incorporate in a prospectus supplement or post-effective amendment such
information as is required by the applicable rules and regulations of the
Commission that such managing underwriter or underwriters, such agent or the
Purchaser specifies should be included therein relating to the terms of the sale
of such Registrable Securities, including, without limitation, information with
respect to the number of Registrable Securities being sold by the Purchaser, or
agent or to any underwriters, the name and description of the Purchaser, agent
or underwriter, the offering price of such Registrable Securities and any
discount, commission or other compensation payable in respect thereof, the
purchase price being paid therefor by such underwriters and with respect to any
other terms of the offering of the Registrable Securities to be sold by the
Purchaser or agent or to such underwriters; and make all required filings of
such prospectus supplement or post-effective amendment promptly after
notification of the matters to be incorporated in such prospectus supplement or
post-effective amendment;

                      (viii) furnish to the Purchaser, each placement or sales
agent, if any, therefor, each underwriter, if any, thereof and the respective
counsel referred to in Section 3(a)(iii) a copy of such registration statement
in the form in which it became effective, each such amendment and supplement
thereto (in each case including all exhibits thereto and documents incorporated
by reference therein) and such number of copies of such registration statement
(excluding exhibits thereto and documents incorporated by reference therein
unless specifically so requested by the Purchaser, agent or underwriter, as the
case may be) and of the prospectus included in such registration statement
(including each preliminary prospectus and any summary prospectus), in
conformity with the requirements of the Securities Act, and such other
documents, as the Purchaser, such agent, if any, and such underwriter, if any,
may reasonably request in order to facilitate the offering and disposition of
the Registrable Securities owned by the Purchaser, offered or sold by such agent
or underwritten by such underwriter and to permit such Purchaser or such agent
and underwriter to satisfy the prospectus delivery requirements of the
Securities Act; and the Company hereby consents to the use of such prospectus
(including such preliminary and summary prospectus) and any amendment or
supplement thereto by the Purchaser and by any such agent and underwriter, in
each case in the form most recently provided to such party by the Company, in
connection with the offering and sale of the Registrable Securities covered by
the prospectus (including such preliminary and summary prospectus) or any
supplement or amendment thereto;

                      (ix) use its commercially reasonable efforts to (A)
register or qualify the Registrable Securities to be included in such
registration statement under such securities laws or blue sky laws of such
jurisdictions as the Purchaser and each placement or sales agent, if any,
therefor and underwriter, if any, thereof shall reasonably request, (B) keep
such registrations or

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CONFIDENTIAL TREATMENT - EDITED COPY

qualifications in effect and comply with such laws so as to permit the
continuance of offers, sales and dealings therein in such jurisdictions during
the respective periods such registration statements are required to remain
effective under Section 2 above and for so long as may be necessary to enable
the Purchaser or any agent or underwriter to complete its distribution of
Registrable Securities pursuant to such registration statement and (C) take any
and all other actions as may be reasonably necessary or advisable to enable the
Purchaser, such agent, if any, and such underwriter, if any, to consummate the
disposition in such jurisdictions of such Registrable Securities; provided,
however, that the Company shall not be required for any such purpose to (I)
qualify as a foreign corporation in any jurisdiction wherein it would not
otherwise be required to qualify but for the requirements of this Section
3(a)(ix) or (II) consent to general service of process in any such jurisdiction;

                      (x) use its commercially reasonable efforts to obtain the
consent or approval of each governmental agency or authority, whether federal,
state or local, which may be required to effect the Shelf Registration or the
offering or sale in connection therewith or to enable the Purchaser to offer, or
to consummate the disposition of, its Registrable Securities;

                      (xi) cooperate with the Purchaser and the managing
underwriters, if any, to facilitate the timely preparation and delivery of any
certificates representing Registrable Securities to be sold, which certificates
shall be printed, lithographed or engraved, or produced by any combination of
such methods, and which shall not, once sold under such registration statement,
bear any restrictive legends; and, in the case of an underwritten offering,
enable such Registrable Securities to be in such denominations and registered in
such names as the managing underwriters may request at least two business days
prior to any sale of the Registrable Securities:

                      (xii) enter into one or more underwriting agreements,
engagement letters, agency agreements or similar agreements, as appropriate,
including (without limitation) customary provisions relating to indemnification
and contribution, and take such other actions in connections therewith as the
Purchaser shall request in order to expedite or facilitate the disposition of
the Registrable Securities;

                      (xiii) notify the Purchaser in writing of any proposal by
the Company to amend or waive any provision of these Registration Rights
pursuant to Section 7(g) hereof and of any amendment or waiver effected pursuant
thereto, each of which notices shall contain the text of the amendment or waiver
proposed or effected, as the case may be;

                      (xiv) in the event that any broker-dealer registered under
the Exchange Act shall underwrite any Registrable Securities or participate as a
member of an underwriting syndicate or selling group or "assist in the
distribution" (within the meaning of the Rules of Fair Practice and the By-Laws
of the National Association of Securities Dealers, Inc. ("NASD")) thereof,
whether as an underwriter, a placement or sales agent or a broker or dealer in
respect thereof, or otherwise, assist such broker-dealer in complying with the
requirements of such Rules and By-Laws, including, without limitation, by
providing such information to such broker-dealer as may be required in order for
such broker-dealer to comply with the requirements of the Rules of Fair Practice
of the NASD;

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CONFIDENTIAL TREATMENT - EDITED COPY

                      (xv) comply with all applicable rules and regulations of
the Commission, and make generally available to its security holders as soon as
practicable but in any event not later than eighteen months after the effective
date of such registration statement, an earning statement of the Company and its
subsidiaries complying with Section 11(a) of the Securities Act (including, at
the option of the Company, Rule 158 thereunder); and

                      (xvi) in the case of Shares or other shares of Common
Stock, use its commercially reasonable efforts to have the Shares or such other
shares approved for trading on the Nasdaq National Market.

               (b) In the event that the Company would be required, pursuant to
Section 3(a)(v)(F) above, to notify the Purchaser, the placement or sales agent,
if any, therefor and the managing underwriters, if any, thereof, the Company
shall, as promptly as practicable, prepare and furnish to the Purchaser, to each
placement or sales agent, if any, and to each underwriter, if any, a reasonable
number of copies of a prospectus supplemented or amended in form and substance
reasonably satisfactory to them, so that, as thereafter delivered to purchasers
of Registrable Securities, such prospectus shall not contain an untrue statement
of a material fact or omit to state a material fact required to be stated
therein or necessary to make the statements therein not misleading in light of
the circumstances then existing. The Purchaser agrees that upon receipt of any
notice from the Company pursuant to Section 3(a)(v)(F) hereof, the Purchaser
shall forthwith discontinue the disposition of Registrable Securities pursuant
to the registration statement applicable to such Registrable Securities until
the Purchaser shall have received copies of such amended or supplemented
prospectus, and if so directed by the Company, the Purchaser shall deliver to
the Company (at the Company's expense) all copies, other than permanent file
copies, then in the Purchaser's possession of the prospectus covering such
Registrable Securities at the time of receipt of such notice.

               (c) The Company may require the Purchaser to furnish to the
Company in writing such information regarding the Purchaser and the Purchaser's
intended method of distribution of such Registrable Securities as the Company
may from time to time reasonably request in writing, but only to the extent that
such information is required in order to comply with such Securities Act. The
Purchaser agrees to notify the Company in writing as promptly as practicable of
any inaccuracy or change in information previously furnished by the Purchaser to
the Company or of the occurrence of any event in either case as a result of
which any prospectus relating to such registration contains or would contain an
untrue statement of a material fact regarding the Purchaser or the Purchaser's
intended method of distribution of such Registrable Securities or omits to state
any material fact regarding the Purchaser or the Purchaser's intended method of
distribution of such Registrable Securities required to be stated therein or
necessary to make the statements therein not misleading in light of the
circumstances then existing, and promptly to furnish to the Company in writing
any additional information required to correct and update any previously
furnished information or required so that such prospectus shall not contain,
with respect to the Purchaser or the distribution of such Registrable
Securities, an untrue statement of a material fact or omit to state a material
fact required to be stated therein or necessary to make the statements therein
not misleading in light of the circumstances then existing. The Purchaser agrees
that upon delivering any written notice to the Company pursuant to this Section
3(c), the Purchaser shall forthwith discontinue the disposition of Registrable
Securities pursuant to the registration statement applicable to such Registrable
Securities until

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<PAGE>   8
CONFIDENTIAL TREATMENT - EDITED COPY

the Purchaser shall have the received copies of such amended or supplemented
prospectus, and if so directed by the Company, the Purchaser shall deliver to
the Company (at the Company's expense) all copies, other than permanent file
copies then in the Purchaser's possession of the prospectus covering such
Registrable Securities at the time of receipt of such notice.

        4. Registration Expenses. The Company agrees to bear and to pay or cause
to be paid promptly upon request being made therefor all expenses incident to
the Company's performance of or compliance with this Agreement, including,
without limitation, (i) all Commission and any NASD registration and filing fees
and expenses, (ii) all fees and expenses in connection with the qualification of
the Registrable Securities for offering and sale under the State securities and
blue sky laws referred to in Section 3(a)(x) hereof, including reasonable fees
and disbursements, not to exceed $5,000, of counsel for the placement or sales
agent or underwriters in connection with such qualifications, (iii) all fees and
expenses in connection with the approval for trading of the Shares or other
shares of Common Stock on the Nasdaq National Market, (iv) all expenses relating
to the preparation, printing, distribution and reproduction of each registration
statement required to be filed hereunder, each prospectus included therein or
prepared for distribution pursuant hereto, each amendment or supplement to the
foregoing, the certificates representing the Registrable Securities and all
other documents relating hereto, (v) internal expenses (including, without
limitation, all salaries and expenses of the Company's officers and employees
performing legal or accounting duties), and (vi) fees, disbursements and
expenses of counsel and independent certified public accountants of the Company
(including the expenses of any opinions or "cold comfort" letters required by or
incident to such performance and compliance) (collectively, the "Registration
Expenses"). Notwithstanding the foregoing, the Purchaser shall pay all agency
fees and commissions and underwriting discounts and commissions attributable to
the sale of the Registrable Securities and the fees and disbursements of any
counsel or other advisors or experts retained by the Purchaser.

        5. Representations and Warranties. The Company represents and warrants
to, and agrees with, the Purchaser that:

               (a) Each registration statement covering Registrable Securities
and each prospectus (including any preliminary or summary prospectus) contained
therein or furnished pursuant to Section 3(a)(ix) hereof and any further
amendments or supplements to any such registration statement or prospectus, when
it becomes effective or is filed with the Commission, as the case may be, and,
in the case of an underwritten offering of Registrable Securities, at the time
of the closing under the underwriting agreement relating thereto will conform in
all material respects to the requirements of the Securities Act, and will not
contain an untrue statement of a material fact or omit to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading; and at all times subsequent to the Effective Time when a prospectus
would be required to be delivered under the Securities Act, other than from (i)
such time as a notice has been given to the Purchaser pursuant to Section
3(a)(vi)(F) hereof until (ii) such time as the Company furnishes an amended or
supplemented prospectus pursuant to Section 3(b) hereof, each such registration
statement, and each prospectus (including any summary prospectus) contained
therein or furnished pursuant to Section 3(c)(ix) hereof, as then amended or
supplemented, will conform in all material respects to the requirements of the
Securities Act, and will not contain an untrue statement of a material fact or
omit to state a material fact required to be stated therein or necessary to make
the statements therein not

                                       8
<PAGE>   9
CONFIDENTIAL TREATMENT - EDITED COPY

misleading in the light of the circumstances then existing; provided, however,
that this representation and warranty shall not apply to any statements or
omissions made in reliance upon and in conformity with information furnished in
writing to the Company by the Purchaser expressly for use therein.

               (b) Any documents incorporated by reference in any prospectus
referred to in Section 5(a) hereof, when they become or became effective or are
or were filed with the Commission, or if amended, when amended, as the case may
be, will conform or conformed in all material respects to the requirements of
the Exchange Act, and none of such documents will contain or contained an untrue
statement of a material fact or will omit or omitted to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading; provided, however, that this representation and warranty shall not
apply to any statements or omissions made in reliance upon and in conformity
with information furnished in writing to the Company by the Purchaser expressly
for use therein.

        6. Indemnification.

               (a) Indemnification by the Company. Upon the registration of
Registrable Securities pursuant to Section 2 hereof, and in consideration of the
agreements of the Purchaser contained herein, and as an inducement to the
Purchaser to purchase the Convertible Note and enter into the Option Agreement,
the Company shall, and it hereby agrees to, indemnify and hold harmless the
Purchaser and each person who participates as a placement or sales agent or as
an underwriter in any offering or sale of such Registrable Securities against
any losses, claims, damages or liabilities, joint or several, to which the
Purchaser or any such agent or underwriter may become subject under the
Securities Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon an
untrue statement or alleged untrue statement of a material fact contained in any
registration statement under which such Registrable Securities were registered
under the Securities Act, or any preliminary, final or summary prospectus
contained therein or furnished by the Company to the Purchaser, agent or
underwriter, or any amendment or supplement thereto, or arise out of or are
based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and the Company shall, and it hereby agrees to, reimburse the
Purchaser, such agent and such underwriter for any legal or other expenses
reasonably incurred by them in connection with investigating or defending any
such action or claim as such expenses are incurred; provided, however, that the
Company shall not be liable to any such person in any such case to the extent
that any such loss, claim, damage or liability arises out of or is based upon an
untrue statement or alleged untrue statement or omission or alleged omission
made in such registration statement, or preliminary, final or summary
prospectus, or amendment or supplement in reliance upon and in conformity with
written information furnished to the Company by such person expressly for use
therein.

               (b) Indemnification by the Purchaser and any Agents and
Underwriters. The Company may require, as a condition to including any
Registrable Securities in any registration statement filed pursuant to Section 2
hereof and to entering into any underwriting agreement with respect thereto,
that the Company shall have received an undertaking reasonably satisfactory to
it from the Purchaser and each underwriter named in any such underwriting
agreement, severally and not jointly, to (i) indemnify and hold harmless the
Company against

                                       9
<PAGE>   10
CONFIDENTIAL TREATMENT - EDITED COPY

any losses, claims, damages or liabilities to which the Company may become
subject, under the Securities Act or otherwise, insofar as such losses, claims,
damages or liabilities (or actions in respect thereof) arise out of or are based
upon an untrue statement or alleged untrue statement of a material fact
contained in such registration statement, or any preliminary, final or summary
prospectus contained therein or furnished by the Company to the Purchaser, agent
or underwriter, or any amendment or supplement thereto, or arise out of or are
based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, in each case to the extent, but only to the extent, that such untrue
statement or alleged untrue statement or omission or alleged omission was made
in reliance upon and in conformity with written information furnished to the
Company by the Purchaser or underwriter expressly for use therein, and (ii)
reimburse the Company for any legal or other expenses reasonably incurred by the
Company in connection with investigating or defending any such action or claim
as such expenses are incurred.

               (c) Notices of Claims, Etc. Promptly after receipt by an
indemnified party under subsection (a) or (b) above of written notice of the
commencement of any action, such indemnified party shall, if a claim in respect
thereof is to be made against an indemnifying party pursuant to the
indemnification provisions of or contemplated by this Section 6, notify such
indemnifying party in writing of the commencement of such action; but the
omission so to notify the indemnifying party shall not relieve it from any
liability which it may have to any indemnified party other than under the
indemnification provisions of or contemplated by Section 6(a) or 6(b) hereof. In
case any such action shall be brought against any indemnified party and it shall
notify an indemnifying party of the commencement thereof, such indemnifying
party shall be entitled to participate therein and, to the extent that it shall
wish, jointly with any other indemnifying party similarly notified, to assume
the defense thereof, with counsel satisfactory to such indemnified party (who
shall not, except with the consent of the indemnified party, be counsel to the
indemnifying party), and, after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof, such
indemnifying party shall not be liable to such indemnified party for any legal
expenses of other counsel or any other expenses, in each case subsequently
incurred by such indemnified party, in connection with the defense thereof other
than reasonable costs of investigation.

               (d) Contribution. Each party hereto agrees that, if for any
reason the indemnification provisions contemplated by Section 6(a) or Section
6(b) are unavailable to or insufficient to hold harmless an indemnified party in
respect of any losses, claims, damages or liabilities (or actions in respect
thereof) referred to therein, then each indemnifying party shall contribute to
the amount paid or payable by such indemnified party as a result of such losses,
claims, damages or liabilities (or actions in respect thereof) in such
proportion as is appropriate to reflect the relative benefits received by
indemnified party on the one hand and the indemnifying party on the other from
any offering of the Registrable Securities. If, however, the allocation provided
by the immediately preceding sentence is not permitted by applicable law or if
the indemnified party failed to give the notice required under subsection (c)
above, then each indemnifying party shall contribute to such amount paid or
payable by such indemnified party in such proportion as is appropriate to
reflect not only such relative benefits but also the relative fault of the
indemnifying party and the indemnified party in connection with the statements
or omissions which resulted in such losses, claims, damages or liabilities (or
actions in respect thereof), as well as any other relevant equitable
considerations. The relative benefits received by

                                       10
<PAGE>   11
CONFIDENTIAL TREATMENT - EDITED COPY

the Company on the one hand and the Purchaser on the other shall be deemed to be
in the same proportion as the total purchase price received by the Company upon
issuance of the Convertible Note to the Purchaser bears to the difference
between the proceeds from the offering of the Registrable Securities received by
the Purchaser and such purchase price. The relative fault of such indemnifying
party and indemnified party shall be determined by reference to, among other
things, whether the untrue or alleged untrue statement of a material fact or
omission or alleged omission to state a material fact relates to information
supplied by such indemnifying party or by such indemnified party, and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission. The parties hereto agree that it
would not be just and equitable if contributions pursuant to this Section 6(d)
were determined by pro rata allocation (even if the Purchaser or any agents or
underwriters or all of them were treated as one entity for such purpose) or by
any other method of allocation which does not take account of the equitable
considerations referred to in this Section 6(d). The amount paid or payable by
an indemnified party as a result of the losses, claims, damages, or liabilities
(or actions in respect thereof) referred to above shall be deemed to include any
legal or other fees or expenses reasonably incurred by such indemnified party in
connection with investigating or defending any such action or claim.
Notwithstanding the provisions of this Section 6(d), absent fraudulent
misrepresentation by the Purchaser, the Purchaser shall not be required to
contribute any amount in excess of the amount by which the dollar amount of the
proceeds received by the Purchaser from the sale of any Registrable Securities
(after deducting any fees, discounts and commissions applicable thereto) exceeds
the amount of any damages which the Purchaser have otherwise been required to
pay by reason of such untrue or alleged untrue statement or omission or alleged
omission, and absent fraudulent misrepresentation by an underwriter, no such
underwriter shall be required to contribute any amount in excess of the amount
by which the total price at which the Registrable Securities underwritten by it
and distributed to the public were offered to the public exceeds the amount of
any damages which such underwriter has otherwise been required to pay by reason
of such untrue or alleged untrue statement or omission or alleged omission. No
person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any person
who was not guilty of such fraudulent misrepresentation. The Purchaser's and any
underwriters' obligations in this Section 6(d) to contribute shall be several in
proportion to the principal amount of Registrable Securities registered or
underwritten, as the case may be, by them and not joint.

               (e) The obligations of the Company under this Section 6 shall be
in addition to any liability which the Company may otherwise have and shall
extend, upon the same terms and conditions, to each officer, director and
partner of the Purchaser, any agent and any underwriter and each person, if any,
who controls the Purchaser or any agent or underwriter within the meaning of the
Securities Act; and the obligations of the Purchaser and any agents and
underwriters contemplated by this Section 6 shall be in addition to any
liability which the Purchaser or any such agent or underwriter, respectively,
may otherwise have and shall extend, upon the same terms and conditions, to each
officer and director of the Company (including any person who, with his consent,
is named in any registration statement as about to become a director of the
Company) and to each person, if any, who controls the Company within the meaning
of the Securities Act.

                                       11
<PAGE>   12
CONFIDENTIAL TREATMENT - EDITED COPY

        7. Miscellaneous.

               (a) No Inconsistent Agreements. The Company represents, warrants,
covenants and agrees that it has not granted, and shall not grant, registration
rights with respect to shares of Common Stock or any other securities which
would be inconsistent with the terms contained in this Agreement.

               (b) Specific Performance. The parties hereto acknowledge that
there may be no adequate remedy at law if any party fails to perform any of its
obligations hereunder and that each party may be irreparably harmed by any such
failure, and accordingly agree that each party, in addition to any other remedy
to which it may be entitled at law or in equity, shall be entitled to compel
specific performance of the obligations of any other party under this Agreement
in accordance with the terms and conditions hereof, in any court of the United
States or any State thereof having jurisdiction.

               (c) Notices. Any notice or other communication required or
permitted to be given hereunder shall be deemed effectively given when
personally delivered, telexed, transmitted by facsimile or mailed by pre-paid
certified mail, return receipt requested, or by telephone when confirmed in
writing by one of the preceding methods addressed as follows (as applicable):

               If to the Company, to:

               SciClone Pharmaceuticals, Inc.
               901 Mariner's Island Blvd., #205
               San Mateo, California 94404

               Attention: [****]
               Telephone Number: [****]
               Facsimile Transmission Number: [****]

               with a copy to:

               Gray Cary Ware & Freidenrich
               400 Hamilton Avenue
               Palo Alto, California 94301

               Attention: David A. Hubb
               Telephone Number: 650-833-2164
               Facsimile Transmission Number: 650-327-3699

                                       12
<PAGE>   13
CONFIDENTIAL TREATMENT - EDITED COPY

               If to the Purchaser, to:

               UBS AG, London Branch
               c/o UBS Warburg LLC
               [****]
               [****]

               Attention: [****]
               Telephone Number: [****]
               Facsimile Transmission Number: [****]

               with copies of the written notice to:

               UBS Warburg LLC
               [****]
               [****]

               Attention: [****]
               Telephone Number: [****]
               Facsimile Transmission Number: [****]

               Attention: [****]
               Telephone Number: [****]
               Facsimile Transmission Number: [****]

or to such other address or number and to the attention of such other person as
either party may designate by written notice to the other party. Notice shall be
effective upon actual receipt.

               (d) Survival. The respective indemnities, agreements,
representations, warranties and each other provision set forth this Agreement or
made pursuant hereto shall remain in full force and effect regardless of any
investigation (or statement as to the results thereof) made by or on behalf of
the Purchaser, any director, officer or partner of the Purchaser, any agent or
underwriter or any director, officer or partner thereof, or any controlling
person of any of the foregoing.

               (e) Law Governing. This Agreement shall be governed by and
construed in accordance with the laws of the State of New York.

               (f) Headings. The descriptive headings of the several Sections
and paragraphs of this Agreement are inserted for convenience only, do not
constitute a part of this Agreement and shall not affect in any way the meaning
or interpretation of this Agreement.

               (g) Entire Agreement; Amendments. This Agreement and the other
writings referred to herein or delivered pursuant hereto which form a part
hereof contain the entire understanding of the parties with respect to its
subject matter. This Agreement supersedes all prior agreements and
understandings between the parties with respect to its subject matter. This
Agreement may be amended and the observance of any term of this Agreement may be
waived

                                       13
<PAGE>   14
CONFIDENTIAL TREATMENT - EDITED COPY

(either generally or in a particular instance and either retroactively or
prospectively) only by a written instrument duly executed by the Company and the
Purchaser.

               (h) Assignment. In connection with any permitted transfer of the
Convertible Note or any portion thereof in a principal amount of not less than
$2,000,000 the Purchaser may assign its rights hereunder in respect of the
Convertible Note to the transferee. Upon such assignment the transferee shall,
insofar as the transferred Convertible Note are concerned, be entitled to all of
the rights, and be subject to all of the obligations, of the Purchaser under
this Agreement, and all references to the "Purchaser" herein shall thereafter be
deemed to include the Purchaser, or such transferee, or both, as the
circumstances warrant.

               (i) Counterparts. This agreement may be executed by the parties
counterparts, each of which shall be deemed to be an original, but all such
respective counterparts shall together constitute one and the same instrument.

        Agreed to and accepted as of the date referred to above.

                                       SciClone Pharmaceuticals, Inc.

                                       By:
                                           -------------------------------------
                                           Name:  Donald R. Sellers
                                           Title: President and
                                                  Chief Executive Officer

                                       UBS AG, LONDON BRANCH

                                       By:
                                           -------------------------------------
                                           Name:
                                           Title:

                                       By:
                                           -------------------------------------
                                           Name:
                                           Title:

                                       14

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