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                                                                    EXHIBIT 4.3

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR
ANY STATE SECURITIES LAW. SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE
ABSENCE OF SUCH REGISTRATION OR UNLESS SUCH SALE OR TRANSFER IS EXEMPT FROM THE
REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SAID ACT.

                          ARONEX PHARMACEUTICALS, INC.

                      WARRANT FOR THE PURCHASE OF SHARES OF
                                  COMMON STOCK

No. 1                                                           150,000 Shares

         FOR VALUE RECEIVED, ARONEX PHARMACEUTICALS, INC., a Delaware
corporation (the "COMPANY"), hereby certifies that Paramount Capital, Inc., its
designee or its permitted assigns is entitled to purchase from the Company, at
any time or from time to time commencing on September 21, 2000 and prior to 5:00
P.M., New York City time, on September 21, 2007, ______________________________
fully paid and non-assessable shares of common stock, $.001 par value per share,
of the Company for an aggregate purchase price of $ 487,500. (Hereinafter, (i)
said common stock, $.001 par value per share, of the Company, is referred to as
the "COMMON STOCK"; (ii) the shares of the Common Stock purchasable hereunder or
under any other Warrant (as hereinafter defined) are referred to as the "WARRANT
SHARES"; (iii) the aggregate purchase price payable for the Warrant Shares
purchasable hereunder is referred to as the "AGGREGATE WARRANT PRICE"; (iv) the
price payable (initially $3.25 per share, subject to adjustment) for each of the
Warrant Shares hereunder is referred to as the "PER SHARE WARRANT PRICE"; (v)
this Warrant, all similar Warrants issued on the date hereof and all warrants
hereafter issued in exchange or substitution for this Warrant or such similar
Warrants are referred to as the "WARRANTS"; (vi) the holder of this Warrant is
referred to as the "HOLDER" and the holder of this Warrant and all other
Warrants and Warrant Shares are referred to as the "HOLDERS" and Holders of more
than fifty percent (50%) of the outstanding Warrants and Warrant Shares are
referred to as the "MAJORITY OF THE HOLDERS"); and (vii) the then Current Market
Price per share of the Common Stock (the "CURRENT MARKET PRICE") shall be deemed
to be the last reported trade of the Common Stock on the trading day prior to
such date or, in case no such reported sales take place on such day, the average
of the last reported bid and asked prices of the Common Stock on such day, in
either case on the principal national securities exchange on which the Common
Stock is admitted to trading or listed, or if not listed or admitted to trading
on any such exchange, the representative closing sale price of the Common Stock
as reported by the National Association of Securities Dealers, Inc. Automated
Quotations System ("NASDAQ"), or other similar organization if NASDAQ is no
longer reporting such information, or, if the Common Stock is not reported on
NASDAQ, the high per share sale price for the Common Stock in the
over-the-counter market as reported by the National Quotation Bureau or similar
organization, or if not so available, the fair market value of the Common Stock
as determined in

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good faith by the Board of Directors. The Aggregate Warrant Price is not subject
to adjustment. The Per Share Warrant Price is subject to adjustment as
hereinafter provided; in the event of any such adjustment, the number of Warrant
Shares deliverable upon exercise of this Warrant shall be adjusted by dividing
the Aggregate Warrant Price by the Per Share Warrant Price in effect immediately
after such adjustment.

         This Warrant, together with warrants of like tenor, constituting in the
aggregate Warrants to purchase 150,000 Warrant Shares, was originally issued
pursuant to an agency agreement between the Company and Paramount Capital, Inc.,
as non-exclusive finder in connection with a private placement (the "OFFERING")
of Units with each Unit consisting of (i) a number of shares of Common Stock of
the Company (rounded to the nearest whole share, with one-half (0.5) of one
share, or greater fraction thereof, being rounded upward), determined by
dividing one hundred thousand dollars ($100,000) by $2.75, and (ii) a warrant
(collectively, the "Warrants") to purchase a number of shares of Common Stock
equal to thirty-three percent (33%) of the shares of Common Stock included in
such Unit, such warrants to be exercisable, in whole or in part, at any time
prior to the fifth anniversary of the date of issuance at an exercise price
equal to $3.00 (the Common Stock, the Warrants, and the Common Stock issuable
upon the exercise of the Warrants are sometimes herein collectively referred to
as the "Securities") (the "Offering") at a purchase price of $100,000 per Unit
(the "Offering Price");

1.       EXERCISE OF WARRANT.

         (a) This Warrant may be exercised in whole at any time, or in part from
time to time, commencing on September 29, 2000 and prior to 5:00 P.M., New York
City time, on September 29, 2007 by the Holder:

          (i) by the surrender of this Warrant (with the subscription form at
     the end hereof duly executed) at the address set forth in Section 9(a)
     hereof, together with proper payment of the Aggregate Warrant Price, or the
     proportionate part thereof if this Warrant is exercised in part, with
     payment for the Warrant Shares made by certified or official bank check
     payable to the order of the Company; or

          (ii) by the surrender of this Warrant (with the cashless exercise form
     at the end hereof duly executed) (a "CASHLESS EXERCISE") at the address set
     forth in Section 9(a) hereof. Such presentation and surrender shall be
     deemed a waiver of the Holder's obligation to pay the Aggregate Warrant
     Price, or the proportionate part thereof if this Warrant is exercised in
     part. In the event of a Cashless Exercise, the Holder shall exchange its
     Warrant for that number of Warrant Shares subject to such Cashless Exercise
     multiplied by a fraction, the numerator of which shall be the difference
     between the then Current Market Price and the Per Share Warrant Price, and
     the denominator of which shall be the then Current Market Price. For
     purposes of any computation under this Section 1(a), the then Current
     Market Price shall be based on the trading day prior to the Cashless
     Exercise.

         (b) If this Warrant is exercised in part, this Warrant must be
exercised for a number of whole shares of the Common Stock and the Holder is
entitled to receive a new Warrant covering the Warrant Shares that have not been
exercised and setting forth the

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proportionate part of the Aggregate Warrant Price applicable to such Warrant
Shares. Upon surrender of this Warrant, the Company will (i) issue a certificate
or certificates in the name of the Holder for the largest number of whole shares
of the Common Stock to which the Holder shall be entitled and, if this Warrant
is exercised in whole, in lieu of any fractional share of the Common Stock to
which the Holder shall be entitled, pay to the Holder cash in an amount equal to
the fair value of such fractional share (determined in such reasonable manner as
the Board of Directors of the Company shall determine), and (ii) deliver the
other securities and properties receivable upon the exercise of this Warrant, or
the proportionate part thereof if this Warrant is exercised in part, pursuant to
the provisions of this Warrant.

         2.       RESERVATION OF WARRANT SHARES; LISTING.

         The Company agrees that, prior to the expiration of this Warrant, the
Company shall at all times (a) have authorized and in reserve, and shall keep
available, solely for issuance and delivery upon the exercise of this Warrant,
the shares of the Common Stock and other securities and properties as from time
to time shall be receivable upon the exercise of this Warrant, free and clear of
all restrictions on sale or transfer, other than under Federal or state
securities laws, and free and clear of all preemptive rights and rights of first
refusal and (b) if the Company hereafter lists its Common Stock on any national
securities exchange, the Nasdaq National Market or the Nasdaq Smallcap Market,
use its best efforts to keep the Warrant Shares authorized for listing on such
exchange upon notice of issuance.

         3.       PROTECTION AGAINST DILUTION.

         (a) If, at any time or from time to time after the date of this
Warrant, the Company shall issue or distribute to the holders of shares of
Common Stock evidence of its indebtedness, any other securities of the Company
or any cash, property or other assets (excluding a subdivision, combination or
reclassification, or dividend or distribution payable in shares of Common Stock,
referred to in Section 3(b), and also excluding cash dividends or cash
distributions paid out of net profits legally available therefor in the full
amount thereof (any such non-excluded event being herein called a "SPECIAL
DIVIDEND")), the Per Share Warrant Price shall be adjusted by multiplying the
Per Share Warrant Price then in effect by a fraction, the numerator of which
shall be the then Current Market Price in effect on the record date of such
issuance or distribution less the fair market value (as determined in good faith
by the Company's Board of Directors) of the evidence of indebtedness, cash,
securities or property, or other assets issued or distributed in such Special
Dividend applicable to one share of Common Stock and the denominator of which
shall be the then Current Market Price in effect on the record date of such
issuance or distribution. An adjustment made pursuant to this Subsection 3(a)
shall become effective immediately after the record date of any such Special
Dividend.

         (b) In case the Company shall (i) pay a dividend or make a distribution
on its capital stock in shares of Common Stock, (ii) subdivide its outstanding
shares of Common Stock into a greater number of shares, (iii) combine its
outstanding shares of Common Stock into a smaller number of shares or (iv) issue
by reclassification of its Common Stock any shares of capital stock of the
Company, the Per Share Warrant Price shall be adjusted to be equal to a
fraction, the numerator of which shall be the Aggregate Warrant Price and the
denominator of which shall be the number of shares of Common Stock or other
capital stock of the Company that the Holder would have owned immediately
following such action had such Warrant been

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exercised immediately prior thereto. An adjustment made pursuant to this
Subsection 3(b) shall become effective immediately after the record date in the
case of a dividend or distribution, and shall become effective immediately after
the effective date in the case of a subdivision, combination or
reclassification.

         (c) No adjustment in the Per Share Warrant Price shall be required in
the case of the issuance by the Company of Common Stock (i) pursuant to the
exercise of any warrant; or (ii) pursuant to the exercise of any stock options
or warrants currently outstanding or securities issued after the date hereof,
which may be approved by the Company's Board of Directors pursuant to any
Company benefit plan or exercised, under any employee benefit plan of the
Company to officers, directors, consultants or employees, but only with respect
to such warrants or stock options as are exercisable at prices no lower than the
closing bid price of the Common Stock as of the date of grant thereof.

         (d) In case of any capital reorganization or reclassification, or any
consolidation or merger to which the Company is a party other than a merger or
consolidation in which the Company is the continuing corporation, or in case of
any sale or conveyance to another entity of the property of the Company as an
entirety or substantially as a entirety, or in the case of any statutory
exchange of securities with another corporation (including any exchange effected
in connection with a merger of a third corporation into the Company), the Holder
of this Warrant shall have the right thereafter to receive on the exercise of
this Warrant the kind and amount of securities, cash or other property which the
Holder would have owned or have been entitled to receive immediately after such
reorganization, reclassification, consolidation, merger, statutory exchange,
sale or conveyance had this Warrant been exercised immediately prior to the
effective date of such reorganization, reclassification, consolidation, merger,
statutory exchange, sale or conveyance and in any such case, if necessary,
appropriate adjustment shall be made in the application of the provisions set
forth in this Section 3 with respect to the rights and interests thereafter of
the Holder of this Warrant to the end that the provisions set forth in this
Section 3 shall thereafter correspondingly be made applicable, as nearly as may
reasonably be, in relation to any shares of stock or other securities or
property thereafter deliverable on the exercise of this Warrant. The above
provisions of this Section 3(e) shall similarly apply to successive
reorganizations, reclassifications, consolidations, mergers, statutory
exchanges, sales or conveyances. The Company shall require the issuer of any
shares of stock or other securities or property thereafter deliverable on the
exercise of this Warrant to be responsible for all of the agreements and
obligations of the Company hereunder. Notice of any such reorganization,
reclassification, consolidation, merger, statutory exchange, sale or conveyance
and of said provisions so proposed to be made, shall be mailed to the Holders of
the Warrants not less than thirty (30) days prior to such event. A sale of all
or substantially all of the assets of the Company for a consideration consisting
primarily of securities shall be deemed a consolidation or merger for the
foregoing purposes.

         (e) No adjustment in the Per Share Warrant Price shall be required
unless such adjustment would require an increase or decrease of at least $0.05
per share of Common Stock; provided, however, that any adjustments which by
reason of this Subsection 3(e) are not required to be made shall be carried
forward and taken into account in any subsequent adjustment; provided, further,
however, that adjustments shall be required and made in accordance with the
provisions of this Section 3 (other than this Subsection 3(e)) not later than
such time as may be required in order to preserve the tax-free nature of a
distribution to the Holder of this Warrant or Common Stock issuable upon the
exercise hereof. All calculations

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under this Section 3 shall be made to the nearest cent or to the nearest 1/100th
of a share, as the case may be. Anything in this Section 3 to the contrary
notwithstanding, the Company shall be entitled to make such reductions in the
Per Share Warrant Price, in addition to those required by this Section 3, as it
in its discretion shall deem to be advisable in order that any stock dividend,
subdivision of shares or distribution of rights to purchase stock or securities
convertible or exchangeable for stock hereafter made by the Company to its
stockholders shall not be taxable.

         (f) Whenever the Per Share Warrant Price is adjusted as provided in
this Section 3 and upon any modification of the rights of a Holder of Warrants
in accordance with this Section 3, the Company shall promptly prepare a brief
statement of the facts requiring such adjustment or modification and the manner
of computing the same and cause copies of such certificate to be mailed to the
Holders of the Warrants. The Company may, but shall not be obligated to unless
requested by a Majority of the Holders, obtain, at its expense, a certificate of
a firm of independent public accountants of recognized standing selected by the
Board of Directors (who may be the regular auditors of the Company) setting
forth the Per Share Warrant Price and the number of Warrant Shares in effect
after such adjustment or the effect of such modification, a brief statement of
the facts requiring such adjustment or modification and the manner of computing
the same and cause copies of such certificate to be mailed to the Holders of the
Warrants.

         (g) If the Board of Directors of the Company shall declare any dividend
or other distribution with respect to the Common Stock other than a cash
distribution out of earned surplus, the Company shall mail notice thereof to the
Holders of the Warrants not less than ten (10) days prior to the record date
fixed for determining stockholders entitled to participate in such dividend or
other distribution.

         (h) If, as a result of an adjustment made pursuant to this Section 3,
the Holder of any Warrant thereafter surrendered for exercise shall become
entitled to receive shares of two or more classes of capital stock or shares of
Common Stock and other capital stock of the Company, the Board of Directors
(whose determination shall be conclusive and shall be described in a written
notice to the Holder of any Warrant promptly after such adjustment) shall
determine the allocation of the adjusted Per Share Warrant Price between or
among shares or such classes of capital stock or shares of Common Stock and
other capital stock.

         (j) Upon the expiration of any rights, options, warrants or conversion
privileges with respect to the issuance of which an adjustment to the Per Share
Warrant Price had been made, if such option, right warrant or conversion shall
not have been exercised, the number of Warrant Shares purchasable upon exercise
of this Warrant, to the extent this Warrant has not then been exercised, shall,
upon such expiration, be readjusted and shall thereafter be such as they would
have been had they been originally adjusted (or had the original adjustment not
been required, as the case may be) on the basis of (A) the fact that Common
Stock, if any, actually issued or sold upon the exercise of such rights,
options, warrants or conversion privileges, and (B) the fact that such shares of
Common Stock, if any, were issued or sold for the consideration actually
received by the Company upon such exercise plus the consideration, if any,
actually received by the Company for the issuance, sale or grant of all such
rights, options, warrants or conversion privileges whether or not exercised;
provided, however, that no such readjustment shall have the effect of decreasing
the number of Warrant Shares purchasable upon exercise of this Warrant by an
amount in excess of the amount of the adjustment initially made in respect of
the issuance, sale or grant of such rights, options, warrants or conversion
privileges.

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         (k) In case any event shall occur as to which the other provisions of
this Section 3 are not strictly applicable but as to which the failure to make
any adjustment would not fairly protect the purchase rights represented by this
Warrant in accordance with the essential intent and principles hereof then, in
each such case, the Board of Directors of the Company shall in good faith
determine the adjustment, if any, on a basis consistent with the essential
intent and principles established herein, necessary to preserve the purchase
rights represented by the Warrants. Upon such determination, the Company will
promptly mail a copy thereof to the Holder of this Warrant and shall make the
adjustments described therein.

         4. FULLY PAID STOCK; TAXES. The shares of the Common Stock represented
by each and every certificate for Warrant Shares delivered on the exercise of
this Warrant shall at the time of such delivery, be duly authorized, validly
issued and outstanding, fully paid and nonassessable, and not subject to
preemptive rights or rights of first refusal, and the Company will take all such
actions as may be necessary to assure that the par value, if any, per share of
the Common Stock is at all times equal to or less than the then Per Share
Warrant Price. The Company shall pay, when due and payable, any and all Federal
and state stamp, original issue or similar taxes which may be payable in respect
of the issue of any Warrant Share or any certificate thereof to the extent
required because of the issuance by the Company of such security.

         5. REGISTRATION UNDER SECURITIES ACT OF 1933. (a) The Holder shall have
the right to participate in the registration rights granted to purchasers of the
Units pursuant to Article V of the subscription agreement (the "Subscription
Agreement") between such purchasers and the Company that were entered into at
the time of the initial sale of the Units. By acceptance of this Warrant, the
Holder agrees to comply with the provisions in Article V of the Subscription
Agreement to same extent as if it were a party thereto.

         (b) Until all of the Warrant Shares and any shares of Common Stock
issuable pursuant to the Article V Rights (as defined below) with respect to the
Warrant Shares have been sold under a Registration Statement or pursuant to Rule
144(k), the Company shall use its reasonable best efforts to file with the
Securities and Exchange Commission all current reports and the information as
may be necessary to enable the Holder to effect sales of its shares in reliance
upon Rule 144(K) promulgated under the Act.

         6. ARTICLE V RIGHTS. Upon exercise of this Warrant, the Holder shall be
entitled to the contractual rights set forth in Article V of the Subscription
Agreement pursuant to which the Offering Units were sold with respect to any
Warrant Shares acquired upon such exercise.

         7 INVESTMENT INTENT; LIMITED TRANSFERABILITY.

         (a) The Holder represents, by accepting this Warrant, that it
understands that this Warrant and any securities obtainable upon exercise of
this Warrant have not been registered for sale under Federal or state securities
laws and are being offered and sold to the Holder pursuant to one or more
exemptions from the registration requirements of such securities laws. In the
absence of an effective registration of such securities or an exemption
therefrom, any certificates for such securities shall bear the legend set forth
on the first page hereof. The Holder understands that it must bear the economic
risk of its investment in this Warrant and any securities obtainable upon
exercise of this Warrant for an indefinite period of time, as this Warrant and
such securities

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have not been registered under Federal or state securities laws and therefore
cannot be sold unless subsequently registered under such laws, unless an
exemption from such registration is available.

         (b) The Holder, by its acceptance of this Warrant, represents to the
Company that it is acquiring this Warrant and will acquire any securities
obtainable upon exercise of this Warrant for its own account for investment and
not with a view to, or for sale in connection with, any distribution thereof in
violation of the Securities Act of 1933, as amended (the "Act"). The Holder
agrees that this Warrant and any such securities will not be sold or otherwise
transferred unless (i) a registration statement with respect to such transfer is
effective under the Act and any applicable state securities laws or (ii) such
sale or transfer is made pursuant to one or more exemptions from the Act.

         (c) This Warrant may not be sold, transferred, assigned or hypothecated
for six (6) months from the date hereof except (i) to any firm or corporation
that succeeds to all or substantially all of the business of Paramount Capital,
Inc., (ii) to any of the officers, employees, associates or affiliated companies
of Paramount Capital, Inc., or of any such successor firm, (iii) to any NASD
member participating in the Offering or any officer or employee of any such NASD
member or (iv) in the case of an individual, pursuant to such individual's last
will and testament or the laws of descent and distribution, and is so
transferable only upon the books of the Company which the Company shall cause to
be maintained for such purpose. The Company may treat the registered Holder of
this Warrant as it appears on the Company's books at any time as the Holder for
all purposes. The Company shall permit any Holder of a Warrant or its duly
authorized attorney, upon written request during ordinary business hours, to
inspect and copy or make extracts from its books showing the registered Holders
of Warrant. All Warrants issued upon the transfer or assignment of this Warrant
will be dated the same date as this Warrant, and all rights of the holder
thereof shall be identical to those of the Holder.

         8. LOSS, ETC., OF WARRANT. Upon receipt of evidence satisfactory to the
Company of the loss, theft, destruction or mutilation of this Warrant, and of
indemnity reasonably satisfactory to the Company, if lost, stolen or destroyed,
and upon surrender and cancellation of this Warrant, if mutilated, the Company
shall execute and deliver to the Holder a new Warrant of like date, tenor and
denomination.

         9. WARRANT HOLDER NOT STOCKHOLDER. This Warrant does not confer upon
the Holder any right to vote on or consent to or receive notice as a stockholder
of the Company, as such, in respect of any matters whatsoever, nor any other
rights or liabilities as a stockholder, prior to the exercise hereof; this
Warrant does, however, require certain notices to Holders as set forth herein.

         10. COMMUNICATION. No notice or other communication under this Warrant
shall be effective unless, however, any notice or other communication shall be
effective and shall be deemed to have been given if, the same is in writing and
is mailed by first-class mail, postage prepaid, addressed to:

         (a) the Company at Aronex Pharmaceuticals, Inc, 8707 Technology Forest
    Place, The Woodlands, TX 77381-1191, Fax: (281) 367-1666 Attn: Geoffrey F.
    Cox or such other address as the Company has designated in writing to the
    Holder, or

         (b) the Holder at c/o Paramount Capital, Inc., 787 Seventh Avenue, New
    York, NY 10019 or other such address as the Holder has designated in writing
    to the Company.

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         11. HEADINGS. The headings of this Warrant have been inserted as a
matter of convenience and shall not affect the construction hereof.

         12. APPLICABLE LAW. This Warrant shall be governed by and construed in
accordance with the law of the State of New York without giving effect to the
principles of conflicts of law thereof.

         13. AMENDMENT, WAIVER, ETC. Except as expressly provided herein,
neither this Warrant nor any term hereof may be amended, waived, discharged or
terminated other than by a written instrument signed by the party against whom
enforcement of any such amendment, waiver, discharge or termination is sought;
provided, however, that any provisions hereof may be amended, waived, discharged
or terminated upon the written consent of the Company and the Majority of the
Holders.

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         IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by
its President and has caused its corporate seal to be hereunto affixed and
attested by its Secretary this 29T day of March, 2000.

                                 ARONEX PHARMACEUTICALS, INC.

                                 By:
                                 Name:  Geoffrey F. Cox
                                 Title: President and Chief Executive Officer

ATTEST:

-------------------------------
Secretary

[Corporate Seal]

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                               SUBSCRIPTION (CASH)

         The undersigned, ___________________, pursuant to the provisions of the
foregoing Warrant, hereby agrees to subscribe for and purchase
____________________ shares of the Common Stock, par value $.001 per share, of
Aronex Pharmaceuticals, Inc. covered by said Warrant, and makes payment therefor
in full at the price per share provided by said Warrant.

Dated:_______________                     Signature:
                                                    ---------------------------
                                          Address:
                                                  ------------------------------

                         SUBSCRIPTION (PROMISSORY NOTE)

                  The undersigned, __________________________, pursuant to the
provisions of the foregoing Warrant, hereby agrees to subscribe for and purchase
________________ shares of the Common Stock, par value $.001 per share, of
Aronex Pharmaceuticals, Inc. covered by said Warrant, and makes payment therefor
in full at the price per share provided by said Warrant by delivery of the
attached Promissory Note. The undersigned hereby confirms the representations
and warranties made by it in the Warrant and in the attached Promissory Note.

Dated:_______________                     Signature:
                                                    ---------------------------
                                          Address:
                                                  -----------------------------

                                CASHLESS EXERCISE

                  The undersigned ___________________, pursuant to the
provisions of the foregoing Warrant, hereby elects to exchange its Warrant for
___________________ shares of Common Stock, par value $.001 per share, of Aronex
Pharmaceuticals, Inc. pursuant to the Cashless Exercise provisions of the
Warrant.

Dated:_______________                     Signature:
                                                    ---------------------------
                                          Address:
                                                  -----------------------------

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                                   ASSIGNMENT

         FOR VALUE RECEIVED _______________ hereby sells, assigns and transfers
unto ____________________ the foregoing Warrant and all rights evidenced
thereby, and does irrevocably constitute and appoint _____________________,
attorney, to transfer said Warrant on the books of Aronex Pharmaceuticals, Inc.

Dated:_______________                     Signature:
                                                   ----------------------------
                                          Address:
                                                 ------------------------------

                               PARTIAL ASSIGNMENT

         FOR VALUE RECEIVED _______________ hereby assigns and transfers unto
____________________ the right to purchase _______ shares of Common Stock, par
value $.001 per share, of Aronex Pharmaceuticals, Inc. covered by the foregoing
Warrant, and a proportionate part of said Warrant and the rights evidenced
thereby, and does irrevocably constitute and appoint ____________________,
attorney, to transfer such part of said Warrant on the books of Aronex
Pharmaceuticals, Inc.

Dated:_______________                     Signature:
                                                   ----------------------------
                                          Address:
                                                 ------------------------------

                                       11<PAGE>   1

                                                                    EXHIBIT 99.1

ARONEX PHARMACEUTICALS COMPLETES $8.1 MILLION PRIVATE PLACEMENT

THE WOODLANDS, Texas, April 18 /PRNewswire/ -- Aronex Pharmaceuticals, Inc.
(Nasdaq National Market: ARNX), announced today that approximately $8.1 million
was raised in its recent private placement. The Company sold units at $100,000
per unit. Each unit consisted of 36,364 shares of Aronex Pharmaceuticals common
stock and a five-year warrant to purchase 12,121 shares of Aronex
Pharmaceuticals common stock at an exercise price of $3.00 per share. Paramount
Capital, Inc. acted as financial advisor.

The private placement was not registered under the Securities Act of 1933 and
was made in reliance on exemptions from the registration requirements of the
Securities Act. Shares of common stock may not be offered or sold by the
purchasers of such shares without registration under the Securities Act or an
applicable exemption from registration. The Company expects to file for
registration of the shares under the Securities Act within thirty days of the
closing.

Aronex Pharmaceuticals, Inc. is a biopharmaceutical company that develops and
commercializes proprietary innovative medicines to treat cancer and infectious
diseases. Aronex Pharmaceuticals currently has four products in clinical
development, two of which (ATRAGEN(R) and Nyotran(R)) are in an advanced stage.
For more information about Aronex Pharmaceuticals, please visit the Company's
web site at http://www.aronex-pharm.com.

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