<PAGE>
                                                                     EXHIBIT 4.1


                              NEOTHERAPEUTICS, INC.

                                     WARRANT

DATED:  JUNE 5, 2002                                           NUMBER NEOT ___

         NeoTherapeutics, Inc., a Delaware corporation (the "Company"), hereby
certifies that, for value received, ________ or its registered assigns
("Holder"), is entitled, subject to the terms set forth below, to purchase from
the Company up to a total of ____ shares of Common Stock, $.001 par value per
share (the "Common Stock"), of the Company (each such share, a "Warrant Share"
and all such shares, the "Warrant Shares") at an exercise price equal to $0.45
per share (as adjusted from time to time as provided in Section 7, the "Exercise
Price"), at any time and from time to time from and after the date hereof and
through and including June 5, 2007 (the "Expiration Date"), and subject to the
following terms and conditions:

         1. Registration of Warrant. The Company shall register this Warrant
upon records to be maintained by the Company for that purpose (the "Warrant
Register"), in the name of the record Holder hereof from time to time. The
Company may deem and treat the registered Holder of this Warrant as the absolute
owner hereof for the purpose of any exercise hereof or any distribution to the
Holder, and for all other purposes, and the Company shall not be affected by
notice to the contrary.

         2. Registration of Transfers and Exchanges.

                  (a) This Warrant may not be sold, transferred, assigned
pledged, hypothecated or otherwise disposed, directly or indirectly, in whole or
in part, without the prior written consent of the Company. Any attempted sale,
transfer, assignment, pledge, hypothecation or other disposition of this
Warrant, or any portion thereof, shall be void and without any force or effect;
provided, however, that, subject to compliance with any applicable securities
laws, the Holder may transfer this Warrant, or any portion thereof, without the
prior written consent of the Company, if such transfer is to (i) a spouse,
child, grandchild, parent, sibling or custodian or trustee for the benefit of
any such relatives, or (ii) any shareholder or affiliate entity.

                  (b) The Company shall register the transfer of any portion of
this Warrant in conformance with Section 2(a) in the Warrant Register, upon
surrender of this Warrant, with the Form of Assignment attached hereto duly
completed and signed, to the Company at the office specified in or pursuant to
Section 10. Upon any such registration or transfer, a new warrant to purchase
Common Stock, in substantially the form of this Warrant (any such new warrant, a
"New Warrant"), evidencing the portion of this Warrant so transferred shall be
issued to the transferee and a New Warrant evidencing the remaining portion of
this Warrant not so transferred, if any, shall be issued to the transferring
Holder. The acceptance of the New Warrant by the transferee thereof shall be
deemed the acceptance of such transferee of all of the rights and obligations of
a holder of this Warrant.

                  (c) This Warrant is exchangeable, upon the surrender hereof by
the Holder to the office of the Company specified in or pursuant to Section 10
for one or more New Warrants,
<PAGE>
evidencing in the aggregate the right to purchase the number of Warrant Shares
which may then be purchased hereunder.

         3. Duration and Exercise of Warrant.

                  (a) This Warrant shall be exercisable by the then registered
Holder on any business day before 5:00 P.M., California time, at any time and
from time to time on or after the date hereof to and including the Expiration
Date. At 5:00 P.M., California time on the Expiration Date, the portion of this
Warrant not exercised prior thereto shall be and become void and of no value.

                  (b) Upon surrender of this Warrant, with the Form of Election
to Purchase attached hereto duly completed and signed, to the Company at its
address for notice set forth in Section 10 and upon payment of the Exercise
Price multiplied by the number of Warrant Shares that the Holder intends to
purchase hereunder, in the manner provided hereunder, all as specified by the
Holder in the Form of Election to Purchase, the Company shall promptly (and in
any event, within four business days) issue or cause to be issued and cause to
be delivered to or upon the written order of the Holder and in such name or
names as the Holder may designate, a certificate for the Warrant Shares issuable
upon such exercise. Any person so designated by the Holder to receive Warrant
Shares shall be deemed to have become holder of record of such Warrant Shares as
of the Date of Exercise of this Warrant.

                  A "Date of Exercise" means the date on which the Company shall
have received (i) this Warrant (or any New Warrant, as applicable), with the
Form of Election to Purchase attached hereto (or attached to such New Warrant)
appropriately completed and duly signed, and (ii) payment of the Exercise Price
for the number of Warrant Shares so indicated by the holder hereof to be
purchased.

                  (c) This Warrant shall be exercisable, either in its entirety
or, from time to time, for a portion of the number of Warrant Shares. If less
than all of the Warrant Shares which may be purchased under this Warrant are
exercised at any time, the Company shall issue or cause to be issued, at its
expense, a New Warrant evidencing the right to purchase the remaining number of
Warrant Shares for which no exercise has been evidenced by this Warrant.

                  (d) Prior to the exercise of this Warrant, the Holder shall
not be entitled to any rights as a stockholder of the Company with respect to
the Warrant Shares, including (without limitation) the right to vote such
shares, receive dividends or other distributions thereon or be notified of
stockholder meetings (except as otherwise set forth in Section 7(f) herein).

                  (e) If by the tenth business day after a Date of Exercise the
Company fails to deliver the required number of Warrant Shares in the manner
required pursuant to Section 3(b), then the Holder will have the right to
rescind such exercise.

                  (f) The Company's obligations to issue and deliver Warrant
Shares in accordance with the terms hereof are absolute and unconditional,
irrespective of any action or inaction by the Holder to enforce the same, any
waiver or consent with respect to any provision hereof, the recovery of any
judgment against any Person or any action to enforce the same, or any setoff,
counterclaim, recoupment, limitation or termination, or any breach or alleged
breach


                                       2
<PAGE>
by the Holder or any other Person of any obligation to the Company or any
violation or alleged violation of law by the Holder or any other Person, and
irrespective of any other circumstance which might otherwise limit such
obligation of the Company to the Holder in connection with the issuance of
Warrant Shares. Nothing herein shall limit a Holder's right to pursue any other
remedies available to it hereunder, at law or in equity including, without
limitation, a decree of specific performance and/or injunctive relief with
respect to the Company's failure to timely deliver certificates representing
shares of Common Stock upon exercise of the Warrant as required pursuant to the
terms hereof.

         4. Payment of Taxes. The Company will pay any documentary stamp taxes
attributable to the issuance of Warrant Shares upon the exercise of this
Warrant; provided, however, that the Company shall not be required to pay any
tax which may be payable in respect of any transfer involved in the registration
of any certificates for Warrant Shares or Warrants in a name other than that of
the Holder. The Holder shall be responsible for all other tax liability that may
arise as a result of holding or transferring this Warrant or receiving Warrant
Shares upon exercise hereof.

         5. Replacement of Warrant. If this Warrant is mutilated, lost, stolen
or destroyed, the Company shall issue or cause to be issued in exchange and
substitution for and upon cancellation hereof, or in lieu of and substitution
for this Warrant, a New Warrant, but only upon receipt of evidence reasonably
satisfactory to the Company of such loss, theft or destruction and indemnity, if
requested, satisfactory to it. Applicants for a New Warrant under such
circumstances shall also comply with such other reasonable regulations and
procedures and pay such other reasonable charges as the Company may prescribe.

         6. Reservation of Warrant Shares. The Company covenants that it will at
all times reserve and keep available out of the aggregate of its authorized but
unissued Common Stock, solely for the purpose of enabling it to issue Warrant
Shares upon exercise of this Warrant as herein provided, the number of Warrant
Shares which are then issuable and deliverable upon the exercise of this entire
Warrant, free from preemptive rights or any other actual contingent purchase
rights of persons other than the Holder. The Company covenants that all Warrant
Shares that shall be so issuable and deliverable shall, upon issuance and the
payment of the applicable Exercise Price in accordance with the terms hereof, be
duly authorized, validly issued and fully paid and nonassessable.

         7. Certain Adjustments. The Exercise Price and number of Warrant Shares
issuable upon exercise of this Warrant are subject to adjustment from time to
time as set forth in this Section 7. Upon each such adjustment of the Exercise
Price pursuant to this Section 7, the Holder shall thereafter prior to the
Expiration Date be entitled to purchase, at the Exercise Price resulting from
such adjustment, the number of Warrant Shares obtained by multiplying the
Exercise Price in effect immediately prior to such adjustment by the number of
Warrant Shares issuable upon exercise of this Warrant immediately prior to such
adjustment and dividing the product thereof by the Exercise Price resulting from
such adjustment.

                  (a) If the Company, at any time while this Warrant is
outstanding, (i) shall pay a stock dividend (except scheduled dividends paid on
outstanding preferred stock which contain a stated dividend rate) or otherwise
make a distribution or distributions on shares of its


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Common Stock payable in shares of Common Stock, (ii) subdivide outstanding
shares of Common Stock into a larger number of shares, or (iii) combine
outstanding shares of Common Stock into a smaller number of shares, the Exercise
Price shall be multiplied by a fraction of which the numerator shall be the
number of shares of Common Stock (excluding treasury shares, if any) outstanding
before such event and the denominator shall be the number of shares of Common
Stock (excluding treasury shares, if any) outstanding after such event. Any
adjustment made pursuant to this Section shall become effective immediately
after the record date for the determination of stockholders entitled to receive
such dividend or distribution and shall become effective immediately after the
effective date in the case of a subdivision or combination, and shall apply to
successive subdivisions and combinations.

                  (b) In case of any reclassification of the Common Stock, any
consolidation or merger of the Company with or into another person, the sale or
transfer of all or substantially all of the assets of the Company or any
compulsory share exchange pursuant to which the Common Stock is converted into
other securities, cash or property, then the Holder shall have the right
thereafter to exercise this Warrant only into the shares of stock and other
securities and property receivable upon or deemed to be held by holders of
Common Stock following such reclassification, consolidation, merger, sale,
transfer or share exchange, and the Holder shall be entitled upon such event to
receive such amount of securities or property equal to the amount of Warrant
Shares such Holder would have been entitled to had such Holder exercised this
Warrant immediately prior to such reclassification, consolidation, merger, sale,
transfer or share exchange. The terms of any such consolidation, merger, sale,
transfer or share exchange shall include such terms so as to continue to give to
the Holder the right to receive the securities or property set forth in this
Section 7(b) upon any exercise following any such reclassification,
consolidation, merger, sale, transfer or share exchange.

                  (c) If the Company, at any time while this Warrant is
outstanding, shall distribute to all holders of Common Stock (and not to holders
of this Warrant) evidences of its indebtedness or assets or rights or warrants
to subscribe for or purchase any security (excluding those referred to in
Sections 7(a), and (b)), other than as part of its dissolution or liquidation or
the winding up of its affairs, then in each such case the Exercise Price shall
be determined by multiplying the Exercise Price in effect immediately prior to
the record date fixed for determination of stockholders entitled to receive such
distribution by a fraction of which the denominator shall be the fair market
value of a share of Common Stock determined as of the record date mentioned
above, and of which the numerator shall be the fair market value of a share of
Common Stock determined as of such record date less the fair market value at
such record date of the portion of such assets or evidence of indebtedness so
distributed applicable to one outstanding share of Common Stock as determined by
the Company's independent certified public accountants that regularly examines
the financial statements of the Company (an "Appraiser").

                  (d) For the purposes of this Section 7, the following clauses
shall also be applicable:

                           (i)      Record Date. In case the Company shall take
                                    a record of the holders of its Common Stock
                                    for the purpose of entitling them (A) to
                                    receive a dividend or other distribution
                                    payable in Common


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                                    Stock or in securities convertible or
                                    exchangeable into shares of Common Stock, or
                                    (B) to subscribe for or purchase Common
                                    Stock or securities convertible or
                                    exchangeable into shares of Common Stock,
                                    then such record date shall be deemed to be
                                    the date of the issue or sale of the shares
                                    of Common Stock deemed to have been issued
                                    or sold upon the declaration of such
                                    dividend or the making of such other
                                    distribution or the date of the granting of
                                    such right of subscription or purchase, as
                                    the case may be.

                           (ii)     Treasury Shares. The number of shares of
                                    Common Stock outstanding at any given time
                                    shall not include shares owned or held by or
                                    for the account of the Company, and the
                                    disposition of any such shares shall be
                                    considered an issue or sale of Common Stock.

                  (e) All calculations under this Section 7 shall be made to the
nearest cent or the nearest 1/100th of a share, as the case may be.

                  (f) If:

                           (i)      the Company shall declare a dividend (or any
                                    other distribution) on its Common Stock; or

                           (ii)     the Company shall declare a special
                                    nonrecurring cash dividend on or a
                                    redemption of its Common Stock; or

                           (iii)    the Company shall authorize the granting to
                                    all holders of the Common Stock rights or
                                    warrants to subscribe for or purchase any
                                    shares of capital stock of any class or of
                                    any rights; or

                           (iv)     the approval of any stockholders of the
                                    Company shall be required in connection with
                                    any reclassification of the Common Stock of
                                    the Company, any consolidation or merger to
                                    which the Company is a party, any sale or
                                    transfer of all or substantially all of the
                                    assets of the Company, or any compulsory
                                    share exchange whereby the Common Stock is
                                    converted into other securities, cash or
                                    property; or

                           (v)      the Company shall authorize the voluntary
                                    dissolution, liquidation or winding up of
                                    the affairs of the Company,

then the Company shall cause to be mailed to each Holder at their last addresses
as they shall appear upon the Warrant Register, at least 30 calendar days prior
to the applicable record or effective date hereinafter specified, a notice
stating (x) the date on which a record is to be taken for the purpose of such
dividend, distribution, redemption, rights or warrants, or if a record is not to
be taken, the date as of which the holders of Common Stock of record to be
entitled to such dividend, distributions, redemption, rights or warrants are to
be determined or (y) the date on which such reclassification, consolidation,
merger, sale, transfer or share exchange is expected to


                                       5
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become effective or close, and the date as of which it is expected that holders
of Common Stock of record shall be entitled to exchange their shares of Common
Stock for securities, cash or other property deliverable upon such
reclassification, consolidation, merger, sale, transfer, share exchange,
dissolution, liquidation or winding up; provided, however, that the failure to
mail such notice or any defect therein or in the mailing thereof shall not
affect the validity of the corporate action required to be specified in such
notice.

         8. Payment of Exercise Price. The Holder shall pay the Exercise Price
in immediately available funds by certified check or bank draft payable to the
order of the Company or by wire transfer to an account designated by the
Company.

         9. Fractional Shares. The Company shall not be required to issue or
cause to be issued fractional Warrant Shares on the exercise of this Warrant.
The number of full Warrant Shares which shall be issuable upon the exercise of
this Warrant shall be computed on the basis of the aggregate number of Warrant
Shares purchasable on exercise of this Warrant so presented. If any fraction of
a Warrant Share would, except for the provisions of this Section 9, be issuable
on the exercise of this Warrant, the Company shall pay an amount in cash equal
to the Exercise Price multiplied by such fraction.

         10. Notices. Any and all notices or other communications or deliveries
hereunder shall be in writing and shall be deemed given and effective on the
earliest of (i) the date of transmission, if such notice or communication is
delivered via facsimile at the facsimile telephone number specified in this
Section prior to 5:00 p.m. (California time) on a business day, (ii) the
business day after the date of transmission, if such notice or communication is
delivered via facsimile at the facsimile telephone number specified in this
Section later than 5:00 p.m. (California time) on any date and earlier than
11:59 p.m. (California time) on such date, (iii) the business day following the
date of mailing, if sent by nationally recognized overnight courier service, or
(iv) upon actual receipt by the party to whom such notice is required to be
given. The addresses for such communications shall be: (i) if to the Company, to
157 Technology Drive, Irvine, CA 92618, Attention: Chief Financial Officer, or
to facsimile no. (949) 788-6706, or (ii) if to the Holder, to the Holder at the
address or facsimile number appearing on the Warrant Register or such other
address or facsimile number as the Holder may provide to the Company in
accordance with this Section 10.

         11. Warrant Agent. The Company shall serve as warrant agent under this
Warrant. The Company may appoint a new warrant agent upon notice to the Holder
in accordance with Section 10. Any corporation into which the Company may be
merged or any corporation resulting from any consolidation to which the Company
shall be a party or any corporation to which the Company transfers substantially
all of its corporate assets shall be a successor warrant agent under this
Warrant without any further act. Any such successor warrant agent shall promptly
cause notice of its succession as warrant agent to be mailed (by first class
mail, postage prepaid) to the Holder at the Holder's last address as shown on
the Warrant Register.


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<PAGE>
         12. Miscellaneous.

                  (a) This Warrant shall be binding on and inure to the benefit
of the parties hereto and their respective successors and permitted assigns.
This Warrant may be amended only in writing signed by the Company and the Holder
and their successors and assigns.

                  (b) Subject to Section 12(a), above, nothing in this Warrant
shall be construed to give to any person or corporation other than the Company
and the Holder any legal or equitable right, remedy or cause under this Warrant.
This Warrant shall inure to the sole and exclusive benefit of the Company and
the Holder.

                  (c) This Warrant shall be governed by and construed and
enforced in accordance with the internal laws of the State of California without
regard to the principles of conflicts of law thereof. The Company and the Holder
hereby irrevocably submit to the exclusive jurisdiction of the state and federal
courts sitting in Orange County, California, for the adjudication of any dispute
hereunder or in connection herewith or with any transaction contemplated hereby
or discussed herein, and hereby irrevocably waives, and agrees not to assert in
any suit, action or proceeding, any claim that it is not personally subject to
the jurisdiction of any such court, or that such suit, action or proceeding is
improper. Each of the Company and the Holder hereby irrevocably waives personal
service of process and consents to process being served in any such suit, action
or proceeding by receiving a copy thereof sent to it at the address in effect
for notices to it under this instrument and in the manner set forth in Section
10 above, and agrees that such service shall constitute good and sufficient
service of process and notice thereof. Nothing contained herein shall be deemed
to limit in any way any right to serve process in any manner permitted by law.

                  (d) The headings herein are for convenience only, do not
constitute a part of this Warrant and shall not be deemed to limit or affect any
of the provisions hereof.

                  (e) In case any one or more of the provisions of this Warrant
shall be invalid or unenforceable in any respect, the validity and
enforceability of the remaining terms and provisions of this Warrant shall not
in any way be affected or impaired thereby and the parties will attempt in good
faith to agree upon a valid and enforceable provision which shall be a
commercially reasonable substitute therefor, and upon so agreeing, shall
incorporate such substitute provision in this Warrant.


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         IN WITNESS WHEREOF, the Company has caused this Warrant to be duly
executed by its authorized officer as of the date first indicated above.

                                NEOTHERAPEUTICS, INC.


                                By:        /s/ Samuel Gulko
                                         --------------------------------------

                                Name:      Samuel Gulko
                                         --------------------------------------

                                Title:     Sen. VP Finance, CFO, Sec & Treas.
                                         --------------------------------------


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                          FORM OF ELECTION TO PURCHASE

(To be executed by the Holder to exercise the right to purchase shares of Common
Stock under the foregoing Warrant)

To NeoTherapeutics, Inc.:

         In accordance with the Warrant enclosed with this Form of Election to
Purchase, the undersigned hereby irrevocably elects to purchase __________
shares of Common Stock ("Common Stock"), $.001 par value per share, of
NeoTherapeutics, Inc. encloses herewith $__________ in cash, certified or
official bank check or checks, which sum represents the aggregate Exercise Price
(as defined in the Warrant) for the number of shares of Common Stock to which
this Form of Election to Purchase relates, together with any applicable taxes
payable by the undersigned pursuant to the Warrant.

         The undersigned requests that certificates for the shares of Common
Stock issuable upon this exercise be issued in the name of

                                            PLEASE INSERT SOCIAL SECURITY OR
                                            TAX IDENTIFICATION NUMBER

                                            ------------------------------------

--------------------------------------------------------------------------------
                         (Please print name and address)

         If the number of shares of Common Stock issuable upon this exercise
shall not be all of the shares of Common Stock which the undersigned is entitled
to purchase in accordance with the enclosed Warrant, the undersigned requests
that a New Warrant (as defined in the Warrant) evidencing the right to purchase
the shares of Common Stock not issuable pursuant to the exercise evidenced
hereby be issued in the name of and delivered to:

--------------------------------------------------------------------------------
                         (Please print name and address)

--------------------------------------------------------------------------------

Dated:  __________, ____         Name of Holder:

                                 (Print)
                                          --------------------------------------

                                 (By:)
                                          --------------------------------------

                                 (Name:)
                                        ----------------------------------------
                                 (Title:)
                                          --------------------------------------
                                 (Signature must conform in all respects to
                                 name of holder as specified on the face of the
                                 Warrant)
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                               FORM OF ASSIGNMENT

           [To be completed and signed only upon transfer of Warrant]

         FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers
unto ____________________ the right represented by the Warrant enclosed with
this Form of Assignment to purchase __________ shares of Common Stock of
NeoTherapeutics, Inc. to which the Warrant relates and appoints
____________________ attorney to transfer said right on the books of
NeoTherapeutics, Inc. with full power of substitution in the premises.

Dated:  __________, ____
                                           -------------------------------------
                                           (Signature must conform in all
                                           respects to name of holder as
                                           specified on the face of the Warrant)

                                           -------------------------------------
                                           Address of Transferee

                                           -------------------------------------

                                           -------------------------------------

In the presence of:

---------------------------------------


                                       -1-
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                                   Schedule I

<TABLE>
<CAPTION>
Warrant Number                             Purchaser                                 Warrant Shares
--------------                        --------------------                           --------------
<S>                                  <C>                                             <C>
    057                                Omicron Partners, L.P.                             200,000
    058                                Brighton Capital Ltd.                                1,400
    059                                Atwood Capital Ltd.                                  1,400
</TABLE>