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                                                                    EXHIBIT 4.15

NEITHER THESE SECURITIES NOR THE SECURITIES INTO WHICH THESE SECURITIES ARE
EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR
THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM
REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES
ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN
EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN
AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS THEREUNDER AND IN
COMPLIANCE WITH APPLICABLE STATE SECURITIES OR BLUE SKY LAWS.

                              NEOTHERAPEUTICS, INC.

                               ADJUSTABLE WARRANT

Warrant No. A-1                                        Dated: September 29, 2000

         NeoTherapeutics, Inc., a Delaware corporation (the "Company"), hereby
certifies that, for value received, Montrose Investments Ltd., or its registered
assigns ("Holder"), is entitled, subject to the terms set forth below, to
purchase from the Company the total number 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") calculated pursuant
to Section 3 of this Warrant (subject to adjustment for certain events as set
forth herein) at an exercise price equal to $.001 per share (as adjusted from
time to time as provided in Section 8, the "Exercise Price"), at the times set
forth herein through and including the 90th Business Day (as defined herein)
immediately following the Second Vesting Date (as defined in Section 3(a)) (the
"Expiration Date"), and subject to the following terms and conditions (certain
terms used herein are defined in Exhibit A attached hereto):

         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.

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                  (a) This Warrant may only be transferred pursuant to an
effective registration statement under the Securities Act, to the Company or
pursuant to an available exemption from or in a transaction not subject to the
registration requirements of the Securities Act. In connection with any transfer
of this Warrant other than pursuant to an effective registration statement or to
the Company, the Company may require the transferor thereof to provide to the
Company an opinion of counsel selected by the transferor, the form and substance
of which opinion shall be reasonably satisfactory to the Company, to the effect
that such transfer does not require registration of such Warrant under the
Securities Act. Holder agrees to the imprinting, so long as is required by this
Section 2(a), of a legend substantially similar to that first above written on
any New Warrant (as defined below). Any such transferee shall agree in writing
to be bound by the terms of this Warrant and shall have the rights of Holder
under this Warrant.

                  (b) The Company shall register the transfer of any portion of
this Warrant in the Warrant Register, upon surrender of this Warrant, with the
Form of Assignment attached hereto duly completed and signed, to the Transfer
Agent or to the Company at the address specified in Section 13. 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 a Warrant.

                  (c) This Warrant is exchangeable, upon the surrender hereof by
the Holder to the office of the Company at the address specified in Section 13
for one or more New Warrants, evidencing in the aggregate the right to purchase
the number of Warrant Shares which may then be purchased hereunder. Any such New
Warrant will be dated the date of such exchange.

         3. Duration and Exercise of Warrants.

                  (a) The vesting of the Warrant Shares which the Holder may
acquire pursuant to this Warrant shall occur on the dates set forth below. On
each such date, this Warrant shall vest on a cumulative basis with respect to a
number of Warrant Shares calculated pursuant to Section 3(b) below. Only the
Warrant Shares that have vested may be acquired upon exercise of this Warrant.

                           (i) The first vesting date (the "First Vesting Date")
shall be the 30th Trading Day following the Effective Date (as defined herein).

                           (ii) The second vesting date (the "Second Vesting
Date") shall be the 30th Trading Day following the First Vesting Date.

                           Each of the First Vesting Date and the Second Vesting
Date shall be referred to herein as a "Vesting Date."

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                  (b) Except as otherwise set forth in this Warrant, this
Warrant shall vest and become exercisable on a Vesting Date with respect to the
number of Warrant Shares calculated in accordance with the following formula:

     (Applicable Share Number) x (Purchase Price x 1.08 - Adjustment Price)
      --------------------------------------------------------------------
                                Adjustment Price

                  If the number calculated in accordance with the foregoing
formula is zero or a negative number, no Warrant Shares shall vest hereunder for
such Vesting Date and the Holder shall not be obligated to transfer any shares
of Common Stock to the Company.

                  (c) Notwithstanding anything herein to the contrary, if, at
any time after the Effective Date: (A) the average of the Per Share Market
Values for ten (10) consecutive Trading Days (as defined herein) exceeds 150% of
the Purchase Price, and (B) no less than five (5) Trading Days during such 10
Trading Day period used in (A), the Per Share Market Value exceeded 150% of the
Purchase Price, then no Warrant Shares shall vest with respect to any subsequent
Vesting Date (accordingly if such circumstances were met prior to the First
Vesting Date, then no Warrant Shares would ever vest under this Warrant).

                  (d) Notwithstanding anything herein to the contrary, if on any
Vesting Date the Adjustment Price shall be less than $5.00 (such an Adjustment
Price, the "Floor Price"), then on such Vesting Date: (i) this Warrant shall
vest with respect to the Warrant Shares pursuant to Section 3(a) and (b) hereof,
provided, that the Adjustment Price pursuant to the formula set forth in Section
3(b) shall, exclusively for purposes of this Section 3(d), equal the Floor Price
(such number of Warrant Shares, the "Initial Shares") and (ii) with respect to
the Warrant Shares whose vesting would, in the absence of the operation of
Section 3(d), result in a vesting of Warrant Shares in excess of the Initial
Shares, the Company will have the option to elect by written notice (the
"Notice") delivered to the Holder no later than thirty (30) Trading Days prior
to the applicable Vesting Date to either (x) pay to the Holder, in cash (the
"Cash Payment"), within three (3) Trading Days from the Vesting Date at issue,
an amount equal to the product obtained by multiplying (A) the applicable
Adjustment Price and (B) the difference between the number of Warrant Shares
which would have, notwithstanding the operation of Section 3(d), vested on such
Vesting Date pursuant to Section 3(a) and (b) hereof and the Initial Shares
(such number of Warrant Shares, the "Subsequent Shares") or (y) allow this
Warrant to vest with respect to the Subsequent Shares. A failure by the Company
to timely deliver the Notice to the Holder pursuant to the terms of this Section
shall constitute an election by the Company to allow this Warrant to vest as to
the Subsequent Shares pursuant to the terms hereof. If the Company shall fail to
pay the Cash Payment in full to the Holder by the third (3rd) Trading Day from
the Vesting Date at issue, then, at the election of the Holder, the Company
shall either (x) pay to the Holder $5,000 per day until the Cash Payment and all
additional payments due hereunder are paid in full, or (y) allow this Warrant to
vest with respect to the Subsequent Shares.

                  (e) The vesting of the Warrant Shares in accordance with this
Section 3 shall not be affected by any failure by the Company to maintain the
effectiveness of the Underlying Shares Registration Statement (as defined
herein) after the Effective Date.

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                  (f) Notwithstanding the foregoing provisions of this Section
3, at any time within ten (10) Trading Days following the occurrence of any of
the following events (each, an "Event"), the Holder shall have the option to
elect by notice ("Vesting Notice") to the Company to have this Warrant vest with
respect to those Warrant Shares that have not yet already vested:

                           (i) upon the occurrence of any of (i) an acquisition
after the date hereof by an individual or legal entity or "group" (as described
in Rule 13d-5(b)(1) promulgated under the Securities Exchange Act of 1934, as
amended (the "Exchange Act")) of in excess of 1/3 of the voting securities of
the Company, (ii) a replacement of more than one-half of the members of the
Company's board of directors which is not approved by those individuals who are
members of the board of directors on the date hereof in one or a series of
related transactions, (iii) the merger of the Company with or into another
entity, consolidation or sale of all or substantially all of the assets of the
Company in one or a series of related transactions, unless following such
transaction or series of transactions, the holders of the Company's securities
prior to the first such transaction continue to hold at least 2/3 of the
securities of the surviving entity or acquirer of such assets or (iv) the
execution by the Company of an agreement to which the Company is a party or by
which it is bound, providing for any of the events set forth above in (i), (ii)
or (iii);

                           (ii) immediately prior to an assignment by the
Company for the benefit of creditors or commencement of a voluntary case under
Title 11 of the United States Code, or an entering into of an order for relief
in an involuntary case under Title 11 of the United States Code, or adoption by
the Company of a plan of liquidation or dissolution;

                           (iii) five (5) Business Days prior to the proposed
consummation with respect to the Company of a "Rule 13e-3 transaction" as
defined in Rule 13e-3 under the Exchange Act (or, if necessary, such earlier
date as the Company shall determine in good faith to be required in order for
the Holder to be able to participate in such transaction), it being agreed that
the Holder will receive actual notice of the 13e-3 Statement filed with the
Commission (as defined herein) on the date filed and actual notice of the date
of acceleration hereunder no later than such date, and that if such transaction
is not consummated, and this Warrant has been exercised, then the Holder (and to
the extent that this Warrant would not but for this paragraph be exercisable,
the Company) shall be entitled to declare the exercise null and void and the
Holder shall, upon return of the Warrant Shares to the Company, be entitled to
receive a refund of the Exercise Price and warrants identical to this Warrant,
and such acceleration shall become void ab initio, and the Warrants shall (as to
any remaining unexercised portion thereof) remain in full force and effect in
accordance with the terms hereof;

                           (iv) The Common Stock fails to be listed or quoted
for trading on the NASDAQ (as defined herein) or a Subsequent Market (as defined
herein) for a period of three (3) Trading Days (which need not be consecutive
Trading Days);

                           (v) A holder of Registrable Securities (as defined in
the Registration Rights Agreement) is not permitted by action of the Company to
sell Registrable Securities under the Underlying Shares Registration Statement
for any reason for five (5) or more Trading Days (whether or not consecutive);
or

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                           (vi) The Company shall fail or default in the timely
performance of any material obligation under the Transaction Documents and such
failure or default shall continue uncured for a period of five (5) Business Days
after the date on which notice of such failure or default is first given to the
Company (it being understood that no prior notice need be provided in the case
of defaults which cannot reasonably be cured within a 5-day period).

                  In the event the Holder delivers a Vesting Notice, this
Warrant shall vest with respect to the number of Warrant Shares calculated in
accordance with the formula set forth on Section 3(b); provided, that for
purposes of such calculation, (i) the "Applicable Share Number" shall be deemed
to mean 100% of the number of shares of Common Stock purchased by the original
Holder pursuant to the Purchase Agreement, provided, that if the Holder delivers
a Vesting Notice subsequent to the First Vesting Date, such number shall be
deemed to mean 50% of the number of shares of Common Stock purchased by the
original Holder pursuant to the Purchase Agreement and (ii) the "Adjustment
Price" shall be deemed to mean the average of the ten (10) lowest Per Share
Market Values (which need not occur on consecutive Trading Days) during the
thirty (30) Trading Days immediately preceding the date on which the Event
occurred.

                  (h) Subject to Sections 3(a) and (b), this Warrant shall be
exercisable by the registered Holder on any Business Day before 8:00 P.M., New
York City time, at any time and from time to time on or after the date hereof to
and including the Expiration Date. At 8:00 P.M., New York City time on the
Expiration Date, the portion of this Warrant not exercised prior thereto shall
be and become void and of no value.

                  (i) Subject to Sections 3(a) and (b), 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.

         4. Delivery of Warrant Shares.

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                  (a) Subject to Sections 2(b), 5 and 9, 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 13 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 (but in no event later than three (3) Trading Days after the Date
of Exercise (as defined herein)) 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, free of restrictive legends, except in the event that either an
Underlying Shares Registration Statement is not then effective or the Warrant
Shares are not freely transferable without volume restrictions pursuant to Rule
144(k) promulgated under the Securities Act of 1933, as amended (the "Securities
Act"). 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. The Company shall, upon request of the Holder, if
available, use its best efforts to deliver Warrant Shares hereunder
electronically through the Depository Trust Corporation or another established
clearing corporation performing similar functions.

                           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.

                  (b) If the Company fails to deliver to the Holder certificate
or certificates representing the Warrant Shares pursuant to Section 4(a) by the
third (3rd) Trading Day after the Date of Exercise, the Company shall pay to
such Holder, in cash, as liquidated damages and not as a penalty, $5,000 for
each day after such third (3rd) Trading Day until such certificates are
delivered. Nothing herein shall limit the Holder's right to pursue actual
damages for the Company's failure to deliver certificates representing shares of
Common Stock upon exercise within the period specified herein and the Holder
shall have the right to pursue all remedies available to it at law or in equity
including, without limitation, a decree of specific performance and/or
injunctive relief. The exercise of any such rights shall not prohibit the Holder
from seeking to enforce damages pursuant to any other Section hereof or under
applicable law.

                  (c) In addition to any other rights available to the Holder,
if the Company fails to deliver to the Holder certificate or certificates
representing the Warrant Shares pursuant to Section 4(a) by the third (3rd)
Trading Day after the Date of Exercise, and if after such third (3rd) Trading
Day the Holder purchases (in an open market transaction or otherwise) shares of
Common Stock to deliver in satisfaction of a sale by the Holder of the Warrant
Shares which the Holder anticipated receiving upon such exercise (a "Buy-In"),
then the Company shall pay (1) in cash to the Holder the amount by which (x) the
Holder's total purchase price (including brokerage commissions, if any) for the
shares of Common Stock so purchased exceeds (y) the amount obtained by
multiplying (A) the number of Warrant Shares that the Company was required to
deliver pursuant to Section 4(b) to deliver to the Holder in connection with the
exercise at issue, by (B) the Per Share Market Value at the time of the
obligation giving rise to such purchase obligation and (2) deliver to the Holder
the

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number of shares of Common Stock that would have been issued had the Company
timely complied with its exercise and delivery obligations under Section 4(b).
For example, if the Holder purchases Common Stock having a total purchase price
of $11,000 to cover a Buy-In with respect to an attempted exercise of shares of
Common Stock with a market price on the date of exercise totaled $10,000, under
clause (A) of the immediately preceding sentence the Company shall be required
to pay the Holder $1,000. The Holder shall provide the Company written notice
and documentation indicating the amounts payable to the Holder in respect of the
Buy-In.

                  (d) 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 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. If the Company breaches its obligations under this Warrant,
then, in addition to any other liabilities the Company may have hereunder and
under applicable law, the Company shall pay or reimburse the Holder on demand
for all costs of collection and enforcement (including reasonable attorneys fees
and expenses).

         5. Payment of Taxes. The Company will pay all 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.

         6. 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 customary and
reasonable indemnity, if requested. 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.

         7. 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 (taking into account the adjustments and
restrictions of Section 8). The Company covenants that all Warrant Shares that
shall be so issuable and deliverable shall, upon

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issuance and the payment of the applicable Exercise Price in accordance with the
terms hereof, be duly and validly authorized, issued and fully paid and
nonassessable.

         8. 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. Upon each such adjustment of the Exercise
Price pursuant to this Section, 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. Notwithstanding anything to the contrary set forth herein, no
adjustment shall be made hereunder to the Exercise Price due to (i) the adoption
by the Company of a shareholders rights plan, (ii) the creation of "rights"
under such a plan that are evidenced by the shares of Common Stock to which they
are attached, but adjustments would be made if such rights are ever separated
from such shares of Common Stock or otherwise become evidenced by a separate
certificate or if, for any other reason, such rights would entitle the holders
thereof or of the Common Stock to which they attach to receive shares of Common
Stock, (iii) the granting of options or warrants to employees, officers,
directors, consultants and other service providers, and the issuance of shares
upon exercise of options granted, under any stock option plan heretofore or
hereinafter duly adopted by the Company, (iv) shares of Common Stock issuable
upon exercise of currently outstanding options and warrants and upon conversion
of any currently outstanding convertible securities of the Company, in each case
to the extent disclosed in Schedule 2.1(c) to the Securities Purchase Agreement
but not with respect to any amendment or modification thereof, (v) shares of
Common Stock issuable in connection with a Strategic Transaction (as defined in
Section 3.9 of the Securities Purchase Agreement), (vi) an underwritten public
offering of Common Stock resulting in net proceeds to the Company in excess of
$10,000,000, (vii) warrants issuable to Brighton Capital, Ltd. in connection
with the Securities Purchase Agreement and the issuance of shares upon exercise
thereof, (viii) warrants to be issued by the Company to Kingsbridge Capital
Limited to purchase 25,000 shares of Common Stock and the issuance of shares
upon exercise thereof, (ix) the granting of warrants to purchase up to 10,000
shares of Common Stock in connection with equipment leasing or other debt
financing transactions, and (x) the issuance of shares of Common Stock issuable
pursuant to the Private Equity Line of Credit Agreement dated March 27, 1998
between the Company and Kingsbridge Capital Limited.

         (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 as of the date hereof which contain a stated dividend rate) or
otherwise make a distribution or distributions on shares of its Common Stock or
on any other class of capital 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 of which the denominator shall
be the number of shares of Common Stock (excluding treasury shares, if any)
outstanding

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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 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, 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 or share exchange. The terms of any such
reclassification 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 8(b) upon any exercise following any such reclassification 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
8(a), (b) and (d)), 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 Exercise Price
determined as of the record date mentioned above, and of which the numerator
shall be such Exercise Price on such record date less the then 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) If at any time the Company or any subsidiary thereof, as applicable
with respect to Common Stock Equivalents (as defined below), shall issue: (x)
shares of Common Stock at a price per share less than both 15% of the Purchase
Price and the market price of the Common Stock at the time of issuance of such
Common Stock, or (y) rights, warrants, options or other securities or debt that
is convertible into or exchangeable for shares of Common Stock ("Common Stock
Equivalents"), entitling any person or entity to acquire shares of Common Stock
at a price per share less than both 15% of the Purchase Price and the market
price of the Common Stock at the time of issuance of such Common Stock
Equivalent (if the holder of the Common Stock Equivalent so issued shall at any
time, whether by operation of purchase price adjustments, reset provisions,
floating conversion, exercise or exchange prices or otherwise, be entitled to
receive shares of Common Stock at a price less than (i) 15% of the Purchase
Price; (ii) the market price of the Common Stock at the time of such adjustment
and (iii) the market price of the Common Stock at the time such shares of Common
Stock are acquired, such issuance shall be deemed to

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<PAGE>   10
have occurred for less than both 15% of the Purchase Price and the market
price), then, forthwith upon such issue or sale, at the option of the Holder,
the Exercise Price shall be reduced to the price (calculated to the nearest
cent) determined by multiplying the Exercise Price in effect immediately prior
thereto by a fraction, the numerator of which shall be the sum of (i) the number
of shares of Common Stock outstanding immediately prior to such issuance, and
(ii) the number of shares of Common Stock which the aggregate consideration
received (or to be received, assuming exercise or conversion in full of such
Common Stock Equivalents) for the issuance of such additional shares of Common
Stock would purchase at the Exercise Price, and the denominator of which shall
be the sum of the number of shares of Common Stock outstanding immediately after
the issuance of such additional shares. For purposes hereof, all shares of
Common Stock that are issuable upon conversion, exercise or exchange of Common
Stock Equivalents shall be deemed outstanding immediately after the issuance of
such Common Stock Equivalents. Such adjustment shall be made whenever such
Common Stock or Common Stock Equivalents are issued, or, if the maximum number
of shares of Common Stock issuable upon conversion, exercise or exchange of a
Common Stock Equivalent is not determined at the time of issuance of such Common
Stock Equivalent, such adjustment shall be made at such time as the maximum
number of shares of Common Stock issuable upon conversion, exercise or exchange
of such Common Stock Equivalent becomes determinable. However, upon the
expiration of any Common Stock Equivalents the issuance of which resulted in an
adjustment in the Exercise Price pursuant to this Section, if any such Common
Stock Equivalents shall expire or be surrendered to the Company and shall not
have been exercised, converted or exchanged in full or shall have been
exercised, converted or exchanged for less than the number of shares of Common
Stock used in computing such adjustment, the Exercise Price shall immediately
upon such expiration be recomputed and effective immediately upon such
expiration be increased to the price which it would have been (but reflecting
any other adjustments in the Exercise Price made pursuant to the provisions of
this Section after the issuance of such Common Stock Equivalents) had the
adjustment of the Exercise Price made upon the issuance of such Common Stock
Equivalents been made on the basis of offering for subscription or purchase only
that number of shares of the Common Stock actually purchased upon the exercise
of such Common Stock Equivalents actually exercised. Notwithstanding anything to
the contrary contained herein, other than adjustments resulting from the
expiration of Common Stock Equivalents, no adjustment shall be made to the
Exercise Price upon: (i) the issuance of shares of Common Stock upon the
exercise, conversion or exchange of any Common Stock Equivalents outstanding as
of the date of issuance of this Warrant, or (ii) any change in the number of
shares of Common Stock issuable upon the exercise, conversion or exchange of any
Common Stock Equivalents outstanding as of the date of issuance of this Warrant,
including, without limitation, changes occurring by operation of purchase price
adjustments, reset provisions, anti-dilution provisions or floating conversion,
exercise or exchange prices.

         (e) In case of any (1) merger or consolidation of the Company with or
into another Person, or (2) sale by the Company of more than one-half of the
assets of the Company (on a book value basis) in one or a series of related
transactions, or (3) tender or other offer or exchange (whether by the Company
or another Person) pursuant to which holders of Common Stock are permitted to
tender or exchange their shares for other securities, stock, cash or property of
the Company or another Person; then the Holder shall have the right thereafter
to (A) exercise this Warrant for the shares of stock and other securities, cash
and property receivable upon or deemed

                                      -10-
<PAGE>   11
to be held by holders of Common Stock following such merger, consolidation or
sale, and the Holder shall be entitled upon such event or series of related
events to receive such amount of securities, cash and property as the Common
Stock for which this Warrant could have been exercised immediately prior to such
merger, consolidation or sales would have been entitled, (B) in the case of a
merger or consolidation, (x) require the surviving entity to issue to the Holder
a warrant entitling the Holder to acquire shares of such entity's common stock,
which warrant shall have terms identical (including with respect to exercise) to
the terms of this Warrant and shall be entitled to all of the rights and
privileges set forth herein and the agreements pursuant to which this Warrant
was issued (including, without limitation, as such rights relate to the
acquisition, transferability, registration and listing of such shares of stock
other securities issuable upon exercise thereof), or (C) in the event of an
exchange or tender offer or other transaction contemplated by clause (3) of this
Section, tender or exchange this Warrant for such securities, stock, cash and
other property receivable upon or deemed to be held by holders of Common Stock
that have tendered or exchanged their shares of Common Stock following such
tender or exchange, and the Holder shall be entitled upon such exchange or
tender to receive such amount of securities, cash and property as the shares of
Common Stock for which this Warrant could have been exercised immediately prior
to such tender or exchange would have been entitled as would have been issued.
In the case of clause (B), the exercise price applicable for the newly issued
warrant shall be based upon the amount of securities, cash and property that
each shares of Common Stock would receive in such transaction and the Exercise
Price immediately prior to the effectiveness or closing date for such
transaction. The terms of any such merger, sale, consolidation, tender or
exchange shall include such terms so as continue to give the Holder the right to
receive the securities, cash and property set forth in this Section upon any
conversion or redemption following such event. This provision shall similarly
apply to successive such events.

         (f) For the purposes of this Section 8, 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 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.

         (g) All calculations under this Section 8 shall be made to the nearest
cent or the nearest 1/100th of a share, as the case may be.

         (h) Whenever the Exercise Price is adjusted pursuant to Section 8(c)
above, the Holder, after receipt of the determination by the Appraiser, shall
have the right to select an additional appraiser (which shall be a nationally
recognized accounting firm), in which case the adjustment

                                      -11-
<PAGE>   12
shall be equal to the average of the adjustments recommended by each of the
Appraiser and such appraiser. The Holder shall promptly mail or cause to be
mailed to the Company, a notice setting forth the Exercise Price after such
adjustment and setting forth a brief statement of the facts requiring such
adjustment. Such adjustment shall become effective immediately after the record
date mentioned above.

         (i) If (i) the Company shall declare a dividend (or any other
distribution) on its Common Stock;(ii) the Company shall declare a special
nonrecurring cash dividend on or a redemption of its Common Stock; (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; (iv) the approval of any stockholders of the Company
shall be required in connection with any reclassification of the Common Stock,
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 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.

         9. Payment of Exercise Price. The Holder may pay the Exercise Price in
one of the following manners:

                  (a) Cash Exercise. The Holder shall deliver immediately
available funds; or

                  (b) Cashless Exercise. The Holder shall surrender this Warrant
to the Company together with a notice of cashless exercise, in which event the
Company shall issue to the Holder the number of Warrant Shares determined as
follows:

                           X = Y (A-B)/A

         where:

                           X = the number of Warrant Shares to be issued to the
                           Holder.

                           Y = the number of Warrant Shares with respect to
                           which this Warrant is being exercised.

                                      -12-
<PAGE>   13
                           A = the average of the closing sale prices of the
                           Common Stock on the NASDAQ for the five (5) trading
                           days immediately prior to (but not including) the
                           Date of Exercise as reported by Bloomberg Information
                           Systems, Inc. (or any successor to its function of
                           reporting stock prices).

                           B = the Exercise Price.

For purposes of Rule 144 promulgated under the Securities Act, it is intended,
understood and acknowledged that the Warrant Shares issued in a cashless
exercise transaction shall be deemed to have been acquired by the Holder, and
the holding period for the Warrant Shares shall be deemed to have been
commenced, on the issue date.

         10. Certain Exercise Restrictions.

                  (a) A Holder may not exercise this Warrant to the extent such
exercise would result in the Holder, together with any affiliate thereof,
beneficially owning (as determined in accordance with Section 13(d) of the
Exchange Act of 1934, as amended (the "Exchange Act") and the rules promulgated
thereunder) in excess of 4.999% of the then issued and outstanding shares of
Common Stock, including shares of Common Stock issuable upon such exercise and
held by such Holder after application of this Section. Since the Holder will not
be obligated to report to the Company the number of shares of Common Stock it
may hold at the time of an exercise hereunder, unless the exercise at issue
would result in the issuance of shares of Common Stock in excess of 4.999% of
the then outstanding shares of Common Stock without regard to any other shares
of Common Stock which may be beneficially owned by the Holder or an affiliate
thereof, the Holder shall have the authority and obligation to determine whether
the restriction contained in this Section will limit any particular exercise
hereunder and to the extent that the Holder determines that the limitation
contained in this Section applies, the determination of which portion of this
Warrant is exercisable shall be the responsibility and obligation of the Holder.
If the Holder has delivered a Form of Election to Purchase for a number of
Warrant Shares that would result in the issuance in excess of the permitted
amount hereunder, the Company shall notify the Holder of this fact and shall
honor the exercise for the maximum portion of this Warrant permitted to be
exercised on such Date of Exercise in accordance with the periods described
herein and disregard the balance of such Form of Election to Purchase, as if
never delivered The provisions of this Section may be waived by a Holder (but
only as to itself and not to any other Holder) upon not less than 61 days' prior
notice to the Company. Other Holders shall be unaffected by any such waiver.

                  (b) A Holder may not exercise this Warrant to the extent such
exercise would result in the Holder, together with any affiliate thereof,
beneficially owning (as determined in accordance with Section 13(d) of the
Exchange Act and the rules promulgated thereunder) in excess of 9.999% of the
then issued and outstanding shares of Common Stock, including shares of Common
Stock issuable upon such exercise and held by such Holder after application of
this Section. Since the Holder will not be obligated to report to the Company
the number of shares of Common Stock it may hold at the time of an exercise
hereunder, unless the exercise at issue would result in the

                                      -13-
<PAGE>   14
issuance of shares of Common Stock in excess of 9.999% of the then outstanding
shares of Common Stock without regard to any other shares of Common Stock which
may be beneficially owned by the Holder or an affiliate thereof, the Holder
shall have the authority and obligation to determine whether the restriction
contained in this Section will limit any particular exercise hereunder and to
the extent that the Holder determines that the limitation contained in this
Section applies, the determination of which portion of this Warrant is
exercisable shall be the responsibility and obligation of the Holder. If the
Holder has delivered a Form of Election to Purchase for a number of Warrant
Shares that would result in the issuance in excess of the permitted amount
hereunder, the Company shall notify the Holder of this fact and shall honor the
exercise for the maximum portion of this Warrant permitted to be exercised on
such Date of Exercise in accordance with the periods described herein and
disregard the balance of such Form of Election to Purchase, as if never
delivered The provisions of this Section may be waived by a Holder (but only as
to itself and not to any other Holder) upon not less than 61 days' prior notice
to the Company. Other Holders shall be unaffected by any such waiver.

                  (c) At any time when the Common Stock is listed for trading on
the NASDAQ or Nasdaq SmallCap Market and the Company has not obtained the
Shareholder Approval (as defined below), then the Company may not issue in
excess of 2,290,081 Warrant Shares (which number equals 19.999% of the number of
shares of Common Stock outstanding on September 28, 2000): (i) upon exercise of
this Warrant, (ii) upon exercise of any other Adjustable Warrant (as defined in
the Purchase Agreement) issued by the Company in accordance with the terms of
the Purchase Agreement, or any warrant substituted therefor, (iii) upon
conversions of debentures (the "Debentures") issued by the Company in accordance
with the terms of that certain Securities Purchase Agreement, dated as of
September 21, 2000, among the Company, NeoGene Technologies, Inc., Montrose
Investments Ltd. and Strong River Investments, Inc. (the "NeoGene Agreement"),
(iv) as payment of interest in respect of Debentures, (v) upon conversions of
shares of preferred stock issued by the Company in accordance with the terms of
the NeoGene Agreement (the "Preferred Stock") and (vi) as payment of dividends
under the Preferred Stock such (number of shares, the "Issuable Maximum"). If on
any Date of Exercise: (A) the Company Stock is listed for trading on the NASDAQ
or Nasdaq SmallCap Market, (B) the Exercise Price then in effect is such that
the aggregate number of shares of Common Stock that would then be issuable: (i)
upon exercise in full of this Warrant together with any shares of Common Stock
previously issued upon exercise of this Warrant, (ii) upon exercise of any other
Adjustable Warrant issued by the Company in accordance with the terms of the
Purchase Agreement, or any warrant substituted therefor, (iii) upon conversions
of Debentures, (iv) as payment of interest in respect of Debentures, (v) upon
conversions of shares of Preferred Stock and (vi) as payment of dividends under
the Preferred Stock, would equal or exceed the Issuable Maximum, and (C) the
Company shall not have previously obtained the vote of shareholders, if any, as
may be required by the applicable rules and regulations of the Nasdaq Stock
Market or any successor entity to approve the issuance of shares of Common Stock
in excess of the Issuable Maximum pursuant to the terms hereof (the "Shareholder
Approval"), then the Company shall issue to the Holder a number of shares of
Common Stock equal to the lesser of (x) the number of shares of Common Stock
issuable upon such exercise and (y) such portion of the Issuable Maximum less
all shares of Common Stock previously issued: (i) upon exercise of any
Adjustable Warrant issued by the Company in accordance with the terms of the
Purchase Agreement, or any warrant substituted therefor, (ii) upon conversions
of Debentures, (iii) as payment of interest

                                      -14-
<PAGE>   15
in respect of Debentures, (iv) upon conversions of shares of Preferred Stock and
(v) as payment of dividends under the Preferred Stock ( the "Current Maximum
Issuable"), as is applicable to this Warrant. The portion of the Current
Issuable Maximum applicable to this Warrant at any time shall be determined
pro-rata by reference to the number of Warrant Shares issuable upon exercise of
all Adjustable Warrants issued by the Company in accordance with the terms of
the Purchase Agreement, or any warrant substituted therefor, then outstanding.
With respect to the shares whose issuance would result in an issuance of shares
of Common Stock in excess of the Current Issuable Maximum, (the "Excess Warrant
Shares"), the Holder shall have the option to require the Company to either: (1)
use its best efforts to obtain the Shareholder Approval applicable to such
issuance as soon as possible, but in any event no later than 60 days after such
request (such 60th day, the "Target Date") or (2) pay to the Holder, within one
(1) Trading Day from the request therefor, an amount in cash equal to the
product of (x) the Excess Warrant Shares multiplied by (y) the closing sales
price of the Common Stock on (a) the Target Date or (b) the Date of Exercise
giving rise to the obligation to seek Shareholder Approval, whichever is greater
(the "Cash Payment"). In the event the Holder has elected to require the Company
to seek the Shareholder Approval pursuant to clause (1) of the immediately
preceding sentence and the Company does not obtain the Shareholder Approval on
or prior to the Target Date, then, on the Target Date, the Company shall pay the
Cash Payment to the Holder. If the Company fails to pay the Cash Payment in full
pursuant to this Section within seven (7) days after the date payable, the
Company will pay interest on such amount at a rate of 18% per annum, or such
lesser maximum amount that is permitted to be paid by applicable law, to the
Holder, accruing daily from the date payable until such amount, plus all such
interest thereon, is paid in full. The Company and the Holder understand and
agree that shares of Common Stock issued upon exercise of any Adjustable Warrant
issued in accordance with the terms of the Purchase Agreement, or any warrant
substituted therefor, and then held by the Holder or an Affiliate thereof may
not cast votes or be deemed outstanding for purposes of any vote to obtain the
Shareholder Approval.

         12. 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, 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.

         13. 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 8:00 PM. (New York City 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 8:00 PM. (New York City time) on any date and earlier than
11:59 PM (New York City time) on such date, (iii) the Business Day following the
date of mailing, if sent by nationally recognized overnight courier service with
next day delivery specified thereon, or (iv) if sent other than by the methods
set forth in (i)-(iii) of this section, 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: 157 Technology Drive, Irvine, CA 92618;

                                      -15-
<PAGE>   16
facsimile number (949) 788-6706, attention Chief Financial Officer, 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 13.

         14. Warrant Agent.

                  (a) The Company shall serve as warrant agent under this
Warrant. Upon thirty (30) days' notice to the Holder, the Company may appoint a
new warrant agent.

                  (b) Any corporation into which the Company or any new warrant
agent may be merged or any corporation resulting from any consolidation to which
the Company or any new warrant agent shall be a party or any corporation to
which the Company or any new warrant agent transfers substantially all of its
corporate trust or shareholders services business 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.

         15. 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 15(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 New York without
regard to the principles of conflicts of law thereof.

                  (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.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK,
                             SIGNATURE PAGE FOLLOWS]

                                      -16-
<PAGE>   17
                  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:  Chief Financial Officer
                                         ---------------------------------------

                                      -17-
<PAGE>   18
                          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. and, if such Holder is not utilizing the cashless exercise
provisions set forth in this Warrant, 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)

<PAGE>   19
                               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 within Warrant
to purchase __________ shares of Common Stock of NeoTherapeutics, Inc. to which
the within 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:

______________________________

<PAGE>   20
                                    Exhibit A

         (i) "Adjustment Price" means for each Vesting Date, the average of the
ten (10) lowest Per Share Market Values (which need not occur on consecutive
Trading Days) during the thirty (30) consecutive Trading Days immediately prior
to a Vesting Date.

         (ii) "Applicable Share Number" means (i) with respect to the First
Vesting Date, 50% of the number of shares of Common Stock purchased by the
Holder pursuant to the Purchase Agreement, and (ii) with respect to the Second
Vesting Date, 50% of the number of shares of Common Stock purchased by the
Holder pursuant to the Purchase Agreement.

         (iii) "Business Day" means any day except Saturday, Sunday and any day
which shall be a federal legal holiday or a day on which banking institutions in
the State of New York and the State of California generally are authorized or
required by law or other governmental action to close.

         (iv) "Closing Date" shall have the meaning set forth in the Purchase
Agreement.

         (v) "Commission" means the Securities and Exchange Commission.

         (vi) "Effective Date" the date on which the initial Underlying Shares
Registration Statement is first declared effective by the Commission.

         (vii) "NASDAQ" shall mean the Nasdaq National Market.

         (viii) "Per Share Market Value" means on any particular date (a) the
closing bid price per share of the Common Stock on such date on the NASDAQ or on
any Subsequent Market, or if there is no such price on such date, then the
closing bid price on the NASDAQ or on such Subsequent Market on the date nearest
preceding such date, or (b) if the Common Stock is not then listed or quoted on
the NASDAQ or a Subsequent Market, the closing bid price for a share of Common
Stock in the over-the-counter market, as reported by the national Quotation
Bureau Incorporated or similar organization or agency succeeding to its
functions of reporting prices) at the close of business on such date, or (c) if
the Common Stock is not then reported by the National Quotation Bureau
Incorporated (or similar organization or agency succeeding to its functions of
reporting prices), then the average of the "Pink Sheet" quotes for the relevant
conversion period, as determined in good faith by the Holder, or (d) if the
Common Stock is not then publicly traded the fair market value of a share of
Common Stock as determined by an appraiser selected in good faith by the Holders
of a majority of the applicable Warrant Shares.

         (ix) "Purchase Agreement" means the Securities Purchase Agreement,
dated the date hereof to which the Company and the original Holder are parties
and pursuant to which this Warrant was issued.

         (x) "Purchase Price" means $8.26.

         (xi) "Subsequent Market" shall mean any of the New York Stock Exchange,
Inc., American Stock Exchange, Inc. or Nasdaq SmallCap Market.

         (xii) "Trading Day" means a day on which the Common Stock is traded on
NASDAQ or any Subsequent Market, as the case may be, or (b) if the Common Stock
is not listed on the NASDAQ or on a Subsequent Market, a day on which the Common
Stock is traded in the over-the-counter market, as reported by the OTC Bulletin
Board, or (i) if the Common Stock is not quoted on the OTC Bulletin Board a day
on which the Common Stock is quoted in the over-the-counter market as reported
by the National Quotation Bureau Incorporated (or any similar organization or

<PAGE>   21
agency succeeding its functions of reporting price); provided, that in the event
that the Common Stock is not listed or quoted, as set forth in (a), (b) or (c)
hereof, the Trading Day shall mean a Business Day.

         (xiii) "Transaction Documents" shall have the meaning set forth in the
Purchase Agreement.

         (xiv) "Underlying Shares Registration Statement" shall have the meaning
ascribed to it in the Purchase Agreement.<PAGE>   1
                                                                    EXHIBIT 4.16

NEITHER THESE SECURITIES NOR THE SECURITIES INTO WHICH THESE SECURITIES ARE
EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR
THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM
REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES
ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN
EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN
AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS THEREUNDER AND IN
COMPLIANCE WITH APPLICABLE STATE SECURITIES OR BLUE SKY LAWS.

                              NEOTHERAPEUTICS, INC.

                               ADJUSTABLE WARRANT

Warrant No. A-2                                        Dated: September 29, 2000

         NeoTherapeutics, Inc., a Delaware corporation (the "Company"), hereby
certifies that, for value received, Strong River Investments, Inc., or its
registered assigns ("Holder"), is entitled, subject to the terms set forth
below, to purchase from the Company the total number 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") calculated pursuant
to Section 3 of this Warrant (subject to adjustment for certain events as set
forth herein) at an exercise price equal to $.001 per share (as adjusted from
time to time as provided in Section 8, the "Exercise Price"), at the times set
forth herein through and including the 90th Business Day (as defined herein)
immediately following the Second Vesting Date (as defined in Section 3(a)) (the
"Expiration Date"), and subject to the following terms and conditions (certain
terms used herein are defined in Exhibit A attached hereto):

         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.

<PAGE>   2
                  (a) This Warrant may only be transferred pursuant to an
effective registration statement under the Securities Act, to the Company or
pursuant to an available exemption from or in a transaction not subject to the
registration requirements of the Securities Act. In connection with any transfer
of this Warrant other than pursuant to an effective registration statement or to
the Company, the Company may require the transferor thereof to provide to the
Company an opinion of counsel selected by the transferor, the form and substance
of which opinion shall be reasonably satisfactory to the Company, to the effect
that such transfer does not require registration of such Warrant under the
Securities Act. Holder agrees to the imprinting, so long as is required by this
Section 2(a), of a legend substantially similar to that first above written on
any New Warrant (as defined below). Any such transferee shall agree in writing
to be bound by the terms of this Warrant and shall have the rights of Holder
under this Warrant.

                  (b) The Company shall register the transfer of any portion of
this Warrant in the Warrant Register, upon surrender of this Warrant, with the
Form of Assignment attached hereto duly completed and signed, to the Transfer
Agent or to the Company at the address specified in Section 13. 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 a Warrant.

                  (c) This Warrant is exchangeable, upon the surrender hereof by
the Holder to the office of the Company at the address specified in Section 13
for one or more New Warrants, evidencing in the aggregate the right to purchase
the number of Warrant Shares which may then be purchased hereunder. Any such New
Warrant will be dated the date of such exchange.

         3. Duration and Exercise of Warrants.

                  (a) The vesting of the Warrant Shares which the Holder may
acquire pursuant to this Warrant shall occur on the dates set forth below. On
each such date, this Warrant shall vest on a cumulative basis with respect to a
number of Warrant Shares calculated pursuant to Section 3(b) below. Only the
Warrant Shares that have vested may be acquired upon exercise of this Warrant.

                           (i) The first vesting date (the "First Vesting Date")
shall be the 30th Trading Day following the Effective Date (as defined herein).

                           (ii) The second vesting date (the "Second Vesting
Date") shall be the 30th Trading Day following the First Vesting Date.

                           Each of the First Vesting Date and the Second Vesting
Date shall be referred to herein as a "Vesting Date."

                                      -2-
<PAGE>   3
                  (b) Except as otherwise set forth in this Warrant, this
Warrant shall vest and become exercisable on a Vesting Date with respect to the
number of Warrant Shares calculated in accordance with the following formula:

     (Applicable Share Number) x (Purchase Price x 1.08 - Adjustment Price)
      --------------------------------------------------------------------
                                Adjustment Price

                  If the number calculated in accordance with the foregoing
formula is zero or a negative number, no Warrant Shares shall vest hereunder for
such Vesting Date and the Holder shall not be obligated to transfer any shares
of Common Stock to the Company.

                  (c) Notwithstanding anything herein to the contrary, if, at
any time after the Effective Date: (A) the average of the Per Share Market
Values for ten (10) consecutive Trading Days (as defined herein) exceeds 150% of
the Purchase Price, and (B) no less than five (5) Trading Days during such 10
Trading Day period used in (A), the Per Share Market Value exceeded 150% of the
Purchase Price, then no Warrant Shares shall vest with respect to any subsequent
Vesting Date (accordingly if such circumstances were met prior to the First
Vesting Date, then no Warrant Shares would ever vest under this Warrant).

                  (d) Notwithstanding anything herein to the contrary, if on any
Vesting Date the Adjustment Price shall be less than $5.00 (such an Adjustment
Price, the "Floor Price"), then on such Vesting Date: (i) this Warrant shall
vest with respect to the Warrant Shares pursuant to Section 3(a) and (b) hereof,
provided, that the Adjustment Price pursuant to the formula set forth in Section
3(b) shall, exclusively for purposes of this Section 3(d), equal the Floor Price
(such number of Warrant Shares, the "Initial Shares") and (ii) with respect to
the Warrant Shares whose vesting would, in the absence of the operation of
Section 3(d), result in a vesting of Warrant Shares in excess of the Initial
Shares, the Company will have the option to elect by written notice (the
"Notice") delivered to the Holder no later than thirty (30) Trading Days prior
to the applicable Vesting Date to either (x) pay to the Holder, in cash (the
"Cash Payment"), within three (3) Trading Days from the Vesting Date at issue,
an amount equal to the product obtained by multiplying (A) the applicable
Adjustment Price and (B) the difference between the number of Warrant Shares
which would have, notwithstanding the operation of Section 3(d), vested on such
Vesting Date pursuant to Section 3(a) and (b) hereof and the Initial Shares
(such number of Warrant Shares, the "Subsequent Shares") or (y) allow this
Warrant to vest with respect to the Subsequent Shares. A failure by the Company
to timely deliver the Notice to the Holder pursuant to the terms of this Section
shall constitute an election by the Company to allow this Warrant to vest as to
the Subsequent Shares pursuant to the terms hereof. If the Company shall fail to
pay the Cash Payment in full to the Holder by the third (3rd) Trading Day from
the Vesting Date at issue, then, at the election of the Holder, the Company
shall either (x) pay to the Holder $5,000 per day until the Cash Payment and all
additional payments due hereunder are paid in full, or (y) allow this Warrant to
vest with respect to the Subsequent Shares.

                  (e) The vesting of the Warrant Shares in accordance with this
Section 3 shall not be affected by any failure by the Company to maintain the
effectiveness of the Underlying Shares Registration Statement (as defined
herein) after the Effective Date.

                                      -3-
<PAGE>   4
                  (f) Notwithstanding the foregoing provisions of this Section
3, at any time within ten (10) Trading Days following the occurrence of any of
the following events (each, an "Event"), the Holder shall have the option to
elect by notice ("Vesting Notice") to the Company to have this Warrant vest with
respect to those Warrant Shares that have not yet already vested:

                           (i) upon the occurrence of any of (i) an acquisition
after the date hereof by an individual or legal entity or "group" (as described
in Rule 13d-5(b)(1) promulgated under the Securities Exchange Act of 1934, as
amended (the "Exchange Act")) of in excess of 1/3 of the voting securities of
the Company, (ii) a replacement of more than one-half of the members of the
Company's board of directors which is not approved by those individuals who are
members of the board of directors on the date hereof in one or a series of
related transactions, (iii) the merger of the Company with or into another
entity, consolidation or sale of all or substantially all of the assets of the
Company in one or a series of related transactions, unless following such
transaction or series of transactions, the holders of the Company's securities
prior to the first such transaction continue to hold at least 2/3 of the
securities of the surviving entity or acquirer of such assets or (iv) the
execution by the Company of an agreement to which the Company is a party or by
which it is bound, providing for any of the events set forth above in (i), (ii)
or (iii);

                           (ii) immediately prior to an assignment by the
Company for the benefit of creditors or commencement of a voluntary case under
Title 11 of the United States Code, or an entering into of an order for relief
in an involuntary case under Title 11 of the United States Code, or adoption by
the Company of a plan of liquidation or dissolution;

                           (iii) five (5) Business Days prior to the proposed
consummation with respect to the Company of a "Rule 13e-3 transaction" as
defined in Rule 13e-3 under the Exchange Act (or, if necessary, such earlier
date as the Company shall determine in good faith to be required in order for
the Holder to be able to participate in such transaction), it being agreed that
the Holder will receive actual notice of the 13e-3 Statement filed with the
Commission (as defined herein) on the date filed and actual notice of the date
of acceleration hereunder no later than such date, and that if such transaction
is not consummated, and this Warrant has been exercised, then the Holder (and to
the extent that this Warrant would not but for this paragraph be exercisable,
the Company) shall be entitled to declare the exercise null and void and the
Holder shall, upon return of the Warrant Shares to the Company, be entitled to
receive a refund of the Exercise Price and warrants identical to this Warrant,
and such acceleration shall become void ab initio, and the Warrants shall (as to
any remaining unexercised portion thereof) remain in full force and effect in
accordance with the terms hereof;

                           (iv) The Common Stock fails to be listed or quoted
for trading on the NASDAQ (as defined herein) or a Subsequent Market (as defined
herein) for a period of three (3) Trading Days (which need not be consecutive
Trading Days);

                           (v) A holder of Registrable Securities (as defined in
the Registration Rights Agreement) is not permitted by action of the Company to
sell Registrable Securities under the Underlying Shares Registration Statement
for any reason for five (5) or more Trading Days (whether or not consecutive);
or

                                      -4-
<PAGE>   5
                           (vi) The Company shall fail or default in the timely
performance of any material obligation under the Transaction Documents and such
failure or default shall continue uncured for a period of five (5) Business Days
after the date on which notice of such failure or default is first given to the
Company (it being understood that no prior notice need be provided in the case
of defaults which cannot reasonably be cured within a 5-day period).

                  In the event the Holder delivers a Vesting Notice, this
Warrant shall vest with respect to the number of Warrant Shares calculated in
accordance with the formula set forth on Section 3(b); provided, that for
purposes of such calculation, (i) the "Applicable Share Number" shall be deemed
to mean 100% of the number of shares of Common Stock purchased by the original
Holder pursuant to the Purchase Agreement, provided, that if the Holder delivers
a Vesting Notice subsequent to the First Vesting Date, such number shall be
deemed to mean 50% of the number of shares of Common Stock purchased by the
original Holder pursuant to the Purchase Agreement and (ii) the "Adjustment
Price" shall be deemed to mean the average of the ten (10) lowest Per Share
Market Values (which need not occur on consecutive Trading Days) during the
thirty (30) Trading Days immediately preceding the date on which the Event
occurred.

                  (h) Subject to Sections 3(a) and (b), this Warrant shall be
exercisable by the registered Holder on any Business Day before 8:00 P.M., New
York City time, at any time and from time to time on or after the date hereof to
and including the Expiration Date. At 8:00 P.M., New York City time on the
Expiration Date, the portion of this Warrant not exercised prior thereto shall
be and become void and of no value.

                  (i) Subject to Sections 3(a) and (b), 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.

         4. Delivery of Warrant Shares.

                                      -5-
<PAGE>   6
                  (a) Subject to Sections 2(b), 5 and 9, 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 13 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 (but in no event later than three (3) Trading Days after the Date
of Exercise (as defined herein)) 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, free of restrictive legends, except in the event that either an
Underlying Shares Registration Statement is not then effective or the Warrant
Shares are not freely transferable without volume restrictions pursuant to Rule
144(k) promulgated under the Securities Act of 1933, as amended (the "Securities
Act"). 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. The Company shall, upon request of the Holder, if
available, use its best efforts to deliver Warrant Shares hereunder
electronically through the Depository Trust Corporation or another established
clearing corporation performing similar functions.

                           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.

                  (b) If the Company fails to deliver to the Holder certificate
or certificates representing the Warrant Shares pursuant to Section 4(a) by the
third (3rd) Trading Day after the Date of Exercise, the Company shall pay to
such Holder, in cash, as liquidated damages and not as a penalty, $5,000 for
each day after such third (3rd) Trading Day until such certificates are
delivered. Nothing herein shall limit the Holder's right to pursue actual
damages for the Company's failure to deliver certificates representing shares of
Common Stock upon exercise within the period specified herein and the Holder
shall have the right to pursue all remedies available to it at law or in equity
including, without limitation, a decree of specific performance and/or
injunctive relief. The exercise of any such rights shall not prohibit the Holder
from seeking to enforce damages pursuant to any other Section hereof or under
applicable law.

                  (c) In addition to any other rights available to the Holder,
if the Company fails to deliver to the Holder certificate or certificates
representing the Warrant Shares pursuant to Section 4(a) by the third (3rd)
Trading Day after the Date of Exercise, and if after such third (3rd) Trading
Day the Holder purchases (in an open market transaction or otherwise) shares of
Common Stock to deliver in satisfaction of a sale by the Holder of the Warrant
Shares which the Holder anticipated receiving upon such exercise (a "Buy-In"),
then the Company shall pay (1) in cash to the Holder the amount by which (x) the
Holder's total purchase price (including brokerage commissions, if any) for the
shares of Common Stock so purchased exceeds (y) the amount obtained by
multiplying (A) the number of Warrant Shares that the Company was required to
deliver pursuant to Section 4(b) to deliver to the Holder in connection with the
exercise at issue, by (B) the Per Share Market Value at the time of the
obligation giving rise to such purchase obligation and (2) deliver to the Holder
the

                                      -6-
<PAGE>   7
number of shares of Common Stock that would have been issued had the Company
timely complied with its exercise and delivery obligations under Section 4(b).
For example, if the Holder purchases Common Stock having a total purchase price
of $11,000 to cover a Buy-In with respect to an attempted exercise of shares of
Common Stock with a market price on the date of exercise totaled $10,000, under
clause (A) of the immediately preceding sentence the Company shall be required
to pay the Holder $1,000. The Holder shall provide the Company written notice
and documentation indicating the amounts payable to the Holder in respect of the
Buy-In.

                  (d) 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 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. If the Company breaches its obligations under this Warrant,
then, in addition to any other liabilities the Company may have hereunder and
under applicable law, the Company shall pay or reimburse the Holder on demand
for all costs of collection and enforcement (including reasonable attorneys fees
and expenses).

         5. Payment of Taxes. The Company will pay all 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.

         6. 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 customary and
reasonable indemnity, if requested. 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.

         7. 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 (taking into account the adjustments and
restrictions of Section 8). The Company covenants that all Warrant Shares that
shall be so issuable and deliverable shall, upon

                                      -7-
<PAGE>   8
issuance and the payment of the applicable Exercise Price in accordance with the
terms hereof, be duly and validly authorized, issued and fully paid and
nonassessable.

         8. 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. Upon each such adjustment of the Exercise
Price pursuant to this Section, 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. Notwithstanding anything to the contrary set forth herein, no
adjustment shall be made hereunder to the Exercise Price due to (i) the adoption
by the Company of a shareholders rights plan, (ii) the creation of "rights"
under such a plan that are evidenced by the shares of Common Stock to which they
are attached, but adjustments would be made if such rights are ever separated
from such shares of Common Stock or otherwise become evidenced by a separate
certificate or if, for any other reason, such rights would entitle the holders
thereof or of the Common Stock to which they attach to receive shares of Common
Stock, (iii) the granting of options or warrants to employees, officers,
directors, consultants and other service providers, and the issuance of shares
upon exercise of options granted, under any stock option plan heretofore or
hereinafter duly adopted by the Company, (iv) shares of Common Stock issuable
upon exercise of currently outstanding options and warrants and upon conversion
of any currently outstanding convertible securities of the Company, in each case
to the extent disclosed in Schedule 2.1(c) to the Securities Purchase Agreement
but not with respect to any amendment or modification thereof, (v) shares of
Common Stock issuable in connection with a Strategic Transaction (as defined in
Section 3.9 of the Securities Purchase Agreement), (vi) an underwritten public
offering of Common Stock resulting in net proceeds to the Company in excess of
$10,000,000, (vii) warrants issuable to Brighton Capital, Ltd. in connection
with the Securities Purchase Agreement and the issuance of shares upon exercise
thereof, (viii) warrants to be issued by the Company to Kingsbridge Capital
Limited to purchase 25,000 shares of Common Stock and the issuance of shares
upon exercise thereof, (ix) the granting of warrants to purchase up to 10,000
shares of Common Stock in connection with equipment leasing or other debt
financing transactions, and (x) the issuance of shares of Common Stock issuable
pursuant to the Private Equity Line of Credit Agreement dated March 27, 1998
between the Company and Kingsbridge Capital Limited.

         (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 as of the date hereof which contain a stated dividend rate) or
otherwise make a distribution or distributions on shares of its Common Stock or
on any other class of capital 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 of which the denominator shall
be the number of shares of Common Stock (excluding treasury shares, if any)
outstanding

                                      -8-
<PAGE>   9
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 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, 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 or share exchange. The terms of any such
reclassification 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 8(b) upon any exercise following any such reclassification 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
8(a), (b) and (d)), 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 Exercise Price
determined as of the record date mentioned above, and of which the numerator
shall be such Exercise Price on such record date less the then 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) If at any time the Company or any subsidiary thereof, as applicable
with respect to Common Stock Equivalents (as defined below), shall issue: (x)
shares of Common Stock at a price per share less than both 15% of the Purchase
Price and the market price of the Common Stock at the time of issuance of such
Common Stock, or (y) rights, warrants, options or other securities or debt that
is convertible into or exchangeable for shares of Common Stock ("Common Stock
Equivalents"), entitling any person or entity to acquire shares of Common Stock
at a price per share less than both 15% of the Purchase Price and the market
price of the Common Stock at the time of issuance of such Common Stock
Equivalent (if the holder of the Common Stock Equivalent so issued shall at any
time, whether by operation of purchase price adjustments, reset provisions,
floating conversion, exercise or exchange prices or otherwise, be entitled to
receive shares of Common Stock at a price less than (i) 15% of the Purchase
Price; (ii) the market price of the Common Stock at the time of such adjustment
and (iii) the market price of the Common Stock at the time such shares of Common
Stock are acquired, such issuance shall be deemed to

                                      -9-
<PAGE>   10
have occurred for less than both 15% of the Purchase Price and the market
price), then, forthwith upon such issue or sale, at the option of the Holder,
the Exercise Price shall be reduced to the price (calculated to the nearest
cent) determined by multiplying the Exercise Price in effect immediately prior
thereto by a fraction, the numerator of which shall be the sum of (i) the number
of shares of Common Stock outstanding immediately prior to such issuance, and
(ii) the number of shares of Common Stock which the aggregate consideration
received (or to be received, assuming exercise or conversion in full of such
Common Stock Equivalents) for the issuance of such additional shares of Common
Stock would purchase at the Exercise Price, and the denominator of which shall
be the sum of the number of shares of Common Stock outstanding immediately after
the issuance of such additional shares. For purposes hereof, all shares of
Common Stock that are issuable upon conversion, exercise or exchange of Common
Stock Equivalents shall be deemed outstanding immediately after the issuance of
such Common Stock Equivalents. Such adjustment shall be made whenever such
Common Stock or Common Stock Equivalents are issued, or, if the maximum number
of shares of Common Stock issuable upon conversion, exercise or exchange of a
Common Stock Equivalent is not determined at the time of issuance of such Common
Stock Equivalent, such adjustment shall be made at such time as the maximum
number of shares of Common Stock issuable upon conversion, exercise or exchange
of such Common Stock Equivalent becomes determinable. However, upon the
expiration of any Common Stock Equivalents the issuance of which resulted in an
adjustment in the Exercise Price pursuant to this Section, if any such Common
Stock Equivalents shall expire or be surrendered to the Company and shall not
have been exercised, converted or exchanged in full or shall have been
exercised, converted or exchanged for less than the number of shares of Common
Stock used in computing such adjustment, the Exercise Price shall immediately
upon such expiration be recomputed and effective immediately upon such
expiration be increased to the price which it would have been (but reflecting
any other adjustments in the Exercise Price made pursuant to the provisions of
this Section after the issuance of such Common Stock Equivalents) had the
adjustment of the Exercise Price made upon the issuance of such Common Stock
Equivalents been made on the basis of offering for subscription or purchase only
that number of shares of the Common Stock actually purchased upon the exercise
of such Common Stock Equivalents actually exercised. Notwithstanding anything to
the contrary contained herein, other than adjustments resulting from the
expiration of Common Stock Equivalents, no adjustment shall be made to the
Exercise Price upon: (i) the issuance of shares of Common Stock upon the
exercise, conversion or exchange of any Common Stock Equivalents outstanding as
of the date of issuance of this Warrant, or (ii) any change in the number of
shares of Common Stock issuable upon the exercise, conversion or exchange of any
Common Stock Equivalents outstanding as of the date of issuance of this Warrant,
including, without limitation, changes occurring by operation of purchase price
adjustments, reset provisions, anti-dilution provisions or floating conversion,
exercise or exchange prices.

         (e) In case of any (1) merger or consolidation of the Company with or
into another Person, or (2) sale by the Company of more than one-half of the
assets of the Company (on a book value basis) in one or a series of related
transactions, or (3) tender or other offer or exchange (whether by the Company
or another Person) pursuant to which holders of Common Stock are permitted to
tender or exchange their shares for other securities, stock, cash or property of
the Company or another Person; then the Holder shall have the right thereafter
to (A) exercise this Warrant for the shares of stock and other securities, cash
and property receivable upon or deemed

                                      -10-
<PAGE>   11
to be held by holders of Common Stock following such merger, consolidation or
sale, and the Holder shall be entitled upon such event or series of related
events to receive such amount of securities, cash and property as the Common
Stock for which this Warrant could have been exercised immediately prior to such
merger, consolidation or sales would have been entitled, (B) in the case of a
merger or consolidation, (x) require the surviving entity to issue to the Holder
a warrant entitling the Holder to acquire shares of such entity's common stock,
which warrant shall have terms identical (including with respect to exercise) to
the terms of this Warrant and shall be entitled to all of the rights and
privileges set forth herein and the agreements pursuant to which this Warrant
was issued (including, without limitation, as such rights relate to the
acquisition, transferability, registration and listing of such shares of stock
other securities issuable upon exercise thereof), or (C) in the event of an
exchange or tender offer or other transaction contemplated by clause (3) of this
Section, tender or exchange this Warrant for such securities, stock, cash and
other property receivable upon or deemed to be held by holders of Common Stock
that have tendered or exchanged their shares of Common Stock following such
tender or exchange, and the Holder shall be entitled upon such exchange or
tender to receive such amount of securities, cash and property as the shares of
Common Stock for which this Warrant could have been exercised immediately prior
to such tender or exchange would have been entitled as would have been issued.
In the case of clause (B), the exercise price applicable for the newly issued
warrant shall be based upon the amount of securities, cash and property that
each shares of Common Stock would receive in such transaction and the Exercise
Price immediately prior to the effectiveness or closing date for such
transaction. The terms of any such merger, sale, consolidation, tender or
exchange shall include such terms so as continue to give the Holder the right to
receive the securities, cash and property set forth in this Section upon any
conversion or redemption following such event. This provision shall similarly
apply to successive such events.

         (f) For the purposes of this Section 8, 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 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.

         (g) All calculations under this Section 8 shall be made to the nearest
cent or the nearest 1/100th of a share, as the case may be.

         (h) Whenever the Exercise Price is adjusted pursuant to Section 8(c)
above, the Holder, after receipt of the determination by the Appraiser, shall
have the right to select an additional appraiser (which shall be a nationally
recognized accounting firm), in which case the adjustment

                                      -11-
<PAGE>   12
shall be equal to the average of the adjustments recommended by each of the
Appraiser and such appraiser. The Holder shall promptly mail or cause to be
mailed to the Company, a notice setting forth the Exercise Price after such
adjustment and setting forth a brief statement of the facts requiring such
adjustment. Such adjustment shall become effective immediately after the record
date mentioned above.

         (i) If (i) the Company shall declare a dividend (or any other
distribution) on its Common Stock;(ii) the Company shall declare a special
nonrecurring cash dividend on or a redemption of its Common Stock; (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; (iv) the approval of any stockholders of the Company
shall be required in connection with any reclassification of the Common Stock,
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 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.

         9. Payment of Exercise Price. The Holder may pay the Exercise Price in
one of the following manners:

                  (a) Cash Exercise. The Holder shall deliver immediately
available funds; or

                  (b) Cashless Exercise. The Holder shall surrender this Warrant
to the Company together with a notice of cashless exercise, in which event the
Company shall issue to the Holder the number of Warrant Shares determined as
follows:

                           X = Y (A-B)/A

         where:

                           X = the number of Warrant Shares to be issued to the
                           Holder.

                           Y = the number of Warrant Shares with respect to
                           which this Warrant is being exercised.

                                      -12-
<PAGE>   13
                           A = the average of the closing sale prices of the
                           Common Stock on the NASDAQ for the five (5) trading
                           days immediately prior to (but not including) the
                           Date of Exercise as reported by Bloomberg Information
                           Systems, Inc. (or any successor to its function of
                           reporting stock prices).

                           B = the Exercise Price.

For purposes of Rule 144 promulgated under the Securities Act, it is intended,
understood and acknowledged that the Warrant Shares issued in a cashless
exercise transaction shall be deemed to have been acquired by the Holder, and
the holding period for the Warrant Shares shall be deemed to have been
commenced, on the issue date.

         10. Certain Exercise Restrictions.

                  (a) A Holder may not exercise this Warrant to the extent such
exercise would result in the Holder, together with any affiliate thereof,
beneficially owning (as determined in accordance with Section 13(d) of the
Exchange Act of 1934, as amended (the "Exchange Act") and the rules promulgated
thereunder) in excess of 4.999% of the then issued and outstanding shares of
Common Stock, including shares of Common Stock issuable upon such exercise and
held by such Holder after application of this Section. Since the Holder will not
be obligated to report to the Company the number of shares of Common Stock it
may hold at the time of an exercise hereunder, unless the exercise at issue
would result in the issuance of shares of Common Stock in excess of 4.999% of
the then outstanding shares of Common Stock without regard to any other shares
of Common Stock which may be beneficially owned by the Holder or an affiliate
thereof, the Holder shall have the authority and obligation to determine whether
the restriction contained in this Section will limit any particular exercise
hereunder and to the extent that the Holder determines that the limitation
contained in this Section applies, the determination of which portion of this
Warrant is exercisable shall be the responsibility and obligation of the Holder.
If the Holder has delivered a Form of Election to Purchase for a number of
Warrant Shares that would result in the issuance in excess of the permitted
amount hereunder, the Company shall notify the Holder of this fact and shall
honor the exercise for the maximum portion of this Warrant permitted to be
exercised on such Date of Exercise in accordance with the periods described
herein and disregard the balance of such Form of Election to Purchase, as if
never delivered The provisions of this Section may be waived by a Holder (but
only as to itself and not to any other Holder) upon not less than 61 days' prior
notice to the Company. Other Holders shall be unaffected by any such waiver.

                  (b) A Holder may not exercise this Warrant to the extent such
exercise would result in the Holder, together with any affiliate thereof,
beneficially owning (as determined in accordance with Section 13(d) of the
Exchange Act and the rules promulgated thereunder) in excess of 9.999% of the
then issued and outstanding shares of Common Stock, including shares of Common
Stock issuable upon such exercise and held by such Holder after application of
this Section. Since the Holder will not be obligated to report to the Company
the number of shares of Common Stock it may hold at the time of an exercise
hereunder, unless the exercise at issue would result in the

                                      -13-
<PAGE>   14
issuance of shares of Common Stock in excess of 9.999% of the then outstanding
shares of Common Stock without regard to any other shares of Common Stock which
may be beneficially owned by the Holder or an affiliate thereof, the Holder
shall have the authority and obligation to determine whether the restriction
contained in this Section will limit any particular exercise hereunder and to
the extent that the Holder determines that the limitation contained in this
Section applies, the determination of which portion of this Warrant is
exercisable shall be the responsibility and obligation of the Holder. If the
Holder has delivered a Form of Election to Purchase for a number of Warrant
Shares that would result in the issuance in excess of the permitted amount
hereunder, the Company shall notify the Holder of this fact and shall honor the
exercise for the maximum portion of this Warrant permitted to be exercised on
such Date of Exercise in accordance with the periods described herein and
disregard the balance of such Form of Election to Purchase, as if never
delivered The provisions of this Section may be waived by a Holder (but only as
to itself and not to any other Holder) upon not less than 61 days' prior notice
to the Company. Other Holders shall be unaffected by any such waiver.

                  (c) At any time when the Common Stock is listed for trading on
the NASDAQ or Nasdaq SmallCap Market and the Company has not obtained the
Shareholder Approval (as defined below), then the Company may not issue in
excess of 2,290,081 Warrant Shares (which number equals 19.999% of the number of
shares of Common Stock outstanding on September 28, 2000): (i) upon exercise of
this Warrant, (ii) upon exercise of any other Adjustable Warrant (as defined in
the Purchase Agreement) issued by the Company in accordance with the terms of
the Purchase Agreement, or any warrant substituted therefor, (iii) upon
conversions of debentures (the "Debentures") issued by the Company in accordance
with the terms of that certain Securities Purchase Agreement, dated as of
September 21, 2000, among the Company, NeoGene Technologies, Inc., Montrose
Investments Ltd. and Strong River Investments, Inc. (the "NeoGene Agreement"),
(iv) as payment of interest in respect of Debentures, (v) upon conversions of
shares of preferred stock issued by the Company in accordance with the terms of
the NeoGene Agreement (the "Preferred Stock") and (vi) as payment of dividends
under the Preferred Stock such (number of shares, the "Issuable Maximum"). If on
any Date of Exercise: (A) the Company Stock is listed for trading on the NASDAQ
or Nasdaq SmallCap Market, (B) the Exercise Price then in effect is such that
the aggregate number of shares of Common Stock that would then be issuable: (i)
upon exercise in full of this Warrant together with any shares of Common Stock
previously issued upon exercise of this Warrant, (ii) upon exercise of any other
Adjustable Warrant issued by the Company in accordance with the terms of the
Purchase Agreement, or any warrant substituted therefor, (iii) upon conversions
of Debentures, (iv) as payment of interest in respect of Debentures, (v) upon
conversions of shares of Preferred Stock and (vi) as payment of dividends under
the Preferred Stock, would equal or exceed the Issuable Maximum, and (C) the
Company shall not have previously obtained the vote of shareholders, if any, as
may be required by the applicable rules and regulations of the Nasdaq Stock
Market or any successor entity to approve the issuance of shares of Common Stock
in excess of the Issuable Maximum pursuant to the terms hereof (the "Shareholder
Approval"), then the Company shall issue to the Holder a number of shares of
Common Stock equal to the lesser of (x) the number of shares of Common Stock
issuable upon such exercise and (y) such portion of the Issuable Maximum less
all shares of Common Stock previously issued: (i) upon exercise of any
Adjustable Warrant issued by the Company in accordance with the terms of the
Purchase Agreement, or any warrant substituted therefor, (ii) upon conversions
of Debentures, (iii) as payment of interest

                                      -14-
<PAGE>   15
in respect of Debentures, (iv) upon conversions of shares of Preferred Stock and
(v) as payment of dividends under the Preferred Stock ( the "Current Maximum
Issuable"), as is applicable to this Warrant. The portion of the Current
Issuable Maximum applicable to this Warrant at any time shall be determined
pro-rata by reference to the number of Warrant Shares issuable upon exercise of
all Adjustable Warrants issued by the Company in accordance with the terms of
the Purchase Agreement, or any warrant substituted therefor, then outstanding.
With respect to the shares whose issuance would result in an issuance of shares
of Common Stock in excess of the Current Issuable Maximum, (the "Excess Warrant
Shares"), the Holder shall have the option to require the Company to either: (1)
use its best efforts to obtain the Shareholder Approval applicable to such
issuance as soon as possible, but in any event no later than 60 days after such
request (such 60th day, the "Target Date") or (2) pay to the Holder, within one
(1) Trading Day from the request therefor, an amount in cash equal to the
product of (x) the Excess Warrant Shares multiplied by (y) the closing sales
price of the Common Stock on (a) the Target Date or (b) the Date of Exercise
giving rise to the obligation to seek Shareholder Approval, whichever is greater
(the "Cash Payment"). In the event the Holder has elected to require the Company
to seek the Shareholder Approval pursuant to clause (1) of the immediately
preceding sentence and the Company does not obtain the Shareholder Approval on
or prior to the Target Date, then, on the Target Date, the Company shall pay the
Cash Payment to the Holder. If the Company fails to pay the Cash Payment in full
pursuant to this Section within seven (7) days after the date payable, the
Company will pay interest on such amount at a rate of 18% per annum, or such
lesser maximum amount that is permitted to be paid by applicable law, to the
Holder, accruing daily from the date payable until such amount, plus all such
interest thereon, is paid in full. The Company and the Holder understand and
agree that shares of Common Stock issued upon exercise of any Adjustable Warrant
issued in accordance with the terms of the Purchase Agreement, or any warrant
substituted therefor, and then held by the Holder or an Affiliate thereof may
not cast votes or be deemed outstanding for purposes of any vote to obtain the
Shareholder Approval.

         12. 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, 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.

         13. 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 8:00 PM. (New York City 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 8:00 PM. (New York City time) on any date and earlier than
11:59 PM (New York City time) on such date, (iii) the Business Day following the
date of mailing, if sent by nationally recognized overnight courier service with
next day delivery specified thereon, or (iv) if sent other than by the methods
set forth in (i)-(iii) of this section, 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: 157 Technology Drive, Irvine, CA 92618;

                                      -15-
<PAGE>   16
facsimile number (949) 788-6706, attention Chief Financial Officer, 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 13.

         14. Warrant Agent.

                  (a) The Company shall serve as warrant agent under this
Warrant. Upon thirty (30) days' notice to the Holder, the Company may appoint a
new warrant agent.

                  (b) Any corporation into which the Company or any new warrant
agent may be merged or any corporation resulting from any consolidation to which
the Company or any new warrant agent shall be a party or any corporation to
which the Company or any new warrant agent transfers substantially all of its
corporate trust or shareholders services business 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.

         15. 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 15(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 New York without
regard to the principles of conflicts of law thereof.

                  (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.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK,
                             SIGNATURE PAGE FOLLOWS]

                                      -16-
<PAGE>   17
                  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:  Chief Financial Officer
                                              ----------------------------------

                                      -17-
<PAGE>   18
                          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. and, if such Holder is not utilizing the cashless exercise
provisions set forth in this Warrant, 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)

<PAGE>   19
                               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 within
Warrant to purchase ____________ shares of Common Stock of NeoTherapeutics, Inc.
to which the within 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:

______________________________

<PAGE>   20
                                    Exhibit A

         (i) "Adjustment Price" means for each Vesting Date, the average
of the ten (10) lowest Per Share Market Values (which need not occur on
consecutive Trading Days) during the thirty (30) consecutive Trading Days
immediately prior to a Vesting Date.

         (ii) "Applicable Share Number" means (i) with respect to the First
Vesting Date, 50% of the number of shares of Common Stock purchased by the
Holder pursuant to the Purchase Agreement, and (ii) with respect to the Second
Vesting Date, 50% of the number of shares of Common Stock purchased by the
Holder pursuant to the Purchase Agreement.

         (iii) "Business Day" means any day except Saturday, Sunday and any day
which shall be a federal legal holiday or a day on which banking institutions in
the State of New York and the State of California generally are authorized or
required by law or other governmental action to close.

         (iv) "Closing Date" shall have the meaning set forth in the Purchase
Agreement.

         (v) "Commission" means the Securities and Exchange Commission.

         (vi) "Effective Date" the date on which the initial Underlying Shares
Registration Statement is first declared effective by the Commission.

         (vii) "NASDAQ" shall mean the Nasdaq National Market.

         (viii) "Per Share Market Value" means on any particular date (a) the
closing bid price per share of the Common Stock on such date on the NASDAQ or on
any Subsequent Market, or if there is no such price on such date, then the
closing bid price on the NASDAQ or on such Subsequent Market on the date nearest
preceding such date, or (b) if the Common Stock is not then listed or quoted on
the NASDAQ or a Subsequent Market, the closing bid price for a share of Common
Stock in the over-the-counter market, as reported by the national Quotation
Bureau Incorporated or similar organization or agency succeeding to its
functions of reporting prices) at the close of business on such date, or (c) if
the Common Stock is not then reported by the National Quotation Bureau
Incorporated (or similar organization or agency succeeding to its functions of
reporting prices), then the average of the "Pink Sheet" quotes for the relevant
conversion period, as determined in good faith by the Holder, or (d) if the
Common Stock is not then publicly traded the fair market value of a share of
Common Stock as determined by an appraiser selected in good faith by the Holders
of a majority of the applicable Warrant Shares.

         (ix) "Purchase Agreement" means the Securities Purchase Agreement,
dated the date hereof to which the Company and the original Holder are parties
and pursuant to which this Warrant was issued.

         (x) "Purchase Price" means $8.26.

         (xi) "Subsequent Market" shall mean any of the New York Stock Exchange,
Inc., American Stock Exchange, Inc. or Nasdaq SmallCap Market.

         (xii) "Trading Day" means a day on which the Common Stock is traded on
NASDAQ or any Subsequent Market, as the case may be, or (b) if the Common Stock
is not listed on the NASDAQ or on a Subsequent Market, a day on which the Common
Stock is traded in the over-the-counter market, as reported by the OTC Bulletin
Board, or (i) if the Common Stock is not quoted on the OTC Bulletin Board a day
on which the Common Stock is quoted in the over-the-counter market as reported
by the National Quotation Bureau Incorporated (or any similar organization or

<PAGE>   21
agency succeeding its functions of reporting price); provided, that in the event
that the Common Stock is not listed or quoted, as set forth in (a), (b) or (c)
hereof, the Trading Day shall mean a Business Day.

         (xiii) "Transaction Documents" shall have the meaning set forth in the
Purchase Agreement.

         (xiv) "Underlying Shares Registration Statement" shall have the meaning
ascribed to it in the Purchase Agreement.

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