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                                                                     EXHIBIT 4.1

                                 AMENDMENT NO. 2
                                     TO THE
                                RIGHTS AGREEMENT
                          DATED AS OF DECEMBER 13, 2000
                                 BY AND BETWEEN
                         SPECTRUM PHARMACEUTICALS, INC.
                                       AND
                         U.S. STOCK TRANSFER CORPORATION

      On December 13, 2000, the Board of Directors of Spectrum Pharmaceuticals,
Inc., a Delaware corporation (the "Company") authorized and declared a dividend
distribution of one Right (as defined in the Rights Agreement) for each share of
its Common Stock, each Right initially representing the right to purchase
one-hundredth of a share of Series B Junior Participating Preferred Stock of the
Company, upon the terms set forth in a Rights Agreement dated as of December 13,
2000 by and between U.S. Stock Transfer Corporation (the "Rights Agent") and the
Company (the "Rights Agreement").

      The Company recently entered into a Common Stock and Warrant Purchase
Agreement dated August 13, 2003 (the "Common Stock and Warrant Purchase
Agreement"), pursuant to which the Company issued and sold shares of its common
stock (the "Common Stock") and Series 2003-1 Warrants (the "Series 2003 - 1
Warrants"). Pursuant to the terms of the Series 2003-1 Warrants, each holder of
a Series 2003-1 Warrant has the right to receive, after the Distribution Date
(as defined in the Rights Agreement), upon exercise of the Series 2003-1
Warrant, such number of Rights (as defined in the Rights Agreement) equal to the
number of Rights such holder would have held if, immediately prior to the
Distribution Date, the portion of the Series 2003-1 Warrant being exercised at
such time had been exercised and the Warrant Shares, as defined in the Series
2003-1 Warrant, issuable upon such exercise were outstanding immediately prior
to the Distribution Date.

      Therefore, in order to give effect to the above terms of the Series 2003-1
Warrant, the Company and U.S. Stock Transfer Corporation hereby agreed to amend
the Rights Agreement as follows:

      1.    Amend Section 1(a) of the Rights Agreement to add the following
            separate paragraph at the end of the section:

            "Also, notwithstanding the foregoing, SCO Capital Partners LLC and
each of the Investors listed on Schedule I (the "Investors") to the Common Stock
and Warrant Purchase Agreement dated August 13, 2003 (the "Common Stock and
Warrant Purchase Agreement") by and among the Company and the Investors, shall
not be deemed to be an "Acquiring Person," by virtue of such Investor or SCO
Capital Partners LLC acquiring Beneficial Ownership of shares of Common Stock
pursuant to the terms of the Common Stock and Warrant Purchase Agreement
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or the Series 2003-1 Warrants (as defined in the Common Stock and Warrant
Purchase Agreement) or the Placement Agent Warrant (the "Placement Agent
Warrant") issued or issuable to SCO Capital Partners LLC, and/or its designees,
pursuant to that certain financial advisory agreement between the Company and
SCO Financial Group LLC, dated February 1, 2003 (the Series 2003-1 Warrants and
the Placement Agent Warrants hereinafter referred to as the "August Series
2003-1 Warrant," if singular, or the "August Series 2003-1 Warrants," if
plural). However, this exception to the definition of "Acquiring Person" shall
not affect the determination of whether the Investors or any of them or SCO
Capital Partners LLC shall be an "Acquiring Person" as the result of any other
acquisition of Beneficial Ownership of shares of Common Stock."

      2.    Add subsection (e) to Section 3 of the Rights Agreement to read in
            its entirety as follows:

            "(e) Notwithstanding any of the foregoing, any holder of an August
Series 2003-1 Warrant who exercises any portion of such August Series 2003-1
Warrant after a Distribution Date shall receive, upon exercise of such August
Series 2003-1 Warrant, a number of Rights equal to the number of Rights such
holder would have held in respect of the Warrant Shares (as defined in the
August Series 2003-1 Warrant) issuable upon such exercise if the portion of the
August Series 2003-1 Warrant being exercised had been exercised immediately
prior to the Distribution Date. As soon as practicable after such exercise (but
in any case no later than 5 business days following such exercise), the Rights
Agent will send by first-class, insured, postage prepaid mail, to the record
holder of such Warrant Shares, one or more Rights Certificates evidencing the
Rights so held. In an event that an adjustment in the number of Rights per share
of Common Stock has been made pursuant to Section 11(p) hereof, the Company
shall make the necessary and appropriate rounding adjustments (in accordance
with Section 14(a) hereof) so that Rights Certificates representing only whole
numbers of Rights are distributed and cash is paid in lieu of any fractional
Rights.

      Capitalized terms used and not otherwise defined herein shall have the
meanings given such terms in the Rights Agreement.

                            [SIGNATURE PAGE FOLLOWS]
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      IN WITNESS WHEREOF, the Company and the Rights Agent have caused this
amendment to be executed this 10th day of May, 2004.

Spectrum Pharmaceuticals, Inc.          U.S. Stock Transfer Corporation

By: /s/ SHYAM KUMARIA                   By: /s/ RICHARD C. BROWN
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Name: Shyam Kumaria                     Name: Richard C. Brown
     --------------------------------        -----------------------------------

Title: Vice President Finance           Title: Vice President
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