Exhibit 10.2

No. ___                                                         May 21, 1999


                          ARONEX PHARMACEUTICALS, INC.

                              10% CONVERTIBLE NOTE

                  THE  SECURITIES  REPRESENTED  BY  THIS  INSTRUMENT  HAVE  BEEN
ACQUIRED FOR INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
1933, AS AMENDED,  OR THE  SECURITIES  LAWS OF ANY STATE OR OTHER  JURISDICTION.
WITHOUT  SUCH   REGISTRATION,   SUCH  SECURITIES  MAY  NOT  BE  SOLD,   PLEDGED,
HYPOTHECATED   OR  OTHERWISE   TRANSFERRED,   EXCEPT  UPON  DELIVERY  TO  ARONEX
PHARMACEUTICALS,   INC.   ("COMPANY")  OF  AN  OPINION  OF  COUNSEL   REASONABLY
SATISFACTORY TO THE COMPANY THAT REGISTRATION IS NOT REQUIRED FOR SUCH TRANSFER,
OR SUBMISSION TO THE COMPANY OF SUCH OTHER  EVIDENCE AS MAY BE  SATISFACTORY  TO
THE COMPANY TO THE EFFECT THAT ANY SUCH  TRANSFER  SHALL NOT BE IN  VIOLATION OF
THE  SECURITIES  ACT OF 1933,  AS AMENDED,  OR ANY  APPLICABLE  STATE OR FOREIGN
SECURITIES LAWS OR ANY RULE OR REGULATION PROMULGATED THEREUNDER.

                  Aronex   Pharmaceuticals,   Inc.,   a   Delaware   corporation
("Company"),  for value received, hereby promises to pay to Genzyme Corporation,
or registered assigns, the principal amount of Two Million Five Hundred Thousand
and No/100 Dollars  ($2,500,000.00) on May 21, 2002, (the "Due Date") except for
any portion of the principal  amount of this Convertible Note which is converted
to shares of Common Stock of the Company  pursuant to the terms of Section 1, at
the office of the Company in The Woodlands,  Texas. Interest shall accrue and be
payable  from  the  date of  issuance  of this  Convertible  Note on the  unpaid
principal   balance  at  a  rate  of  ten  percent  (10%)  per  annum,   payable
semi-annually  on each September 30 and March 30 following the issuance  hereof.
Except as otherwise provided herein, all sums of past-due principal and interest
shall bear  interest at a rate equal to 12% or at the  maximum  rate of interest
permitted  by  applicable  law, if lower.  Payment  shall be made prior to 12:00
noon, Boston, Massachusetts time, on the Due Date. When due, by wire transfer of
immediately  available  funds and  shall be in coin or  currency  of the  United
States of America  which at the time of payment is legal  tender for the payment
of public and private debts.

                  This Convertible Note may not be prepaid by the Company at any
time, in whole or in part.

                  The  following  is a statement of rights of the holder of this
Convertible  Note and the conditions to which this  Convertible Note is subject,
to which the holder hereof, by the acceptance of this Convertible Note, assents:


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                  2. Optional  Conversion Rights. The holder of this Convertible
Note  shall  have the  right to  convert  at any  time  during  the term of this
Convertible  Note part or all of the  principal  amount  hereof,  together  with
accrued  interest  thereon,  into  shares of Common  Stock of the  Company  (the
"Conversion  Shares")  at a price  per  share  equal to $4.35  (the  "Conversion
Price")  subject  to  adjustment  as  provided  in Section 9. Such right must be
exercised by written  notice  given by the holder to the  Company,  which notice
shall specify that portion of the principal  amount and accrued  interest  which
the holder  elects to  convert  and the name of the person or entity for which a
stock certificate  should be issued.  Any such notice given by a holder shall be
final and  irrevocable,  and  conversion  shall occur at the time such notice is
received by the Company with respect to that  portion of this  Convertible  Note
which the holder has  elected to  convert.  The  Company  shall  deliver a stock
certificate  to the holder  within  five  business  days  following  the date of
conversion  with  respect to that number of  Conversion  Shares of Common  Stock
acquired by the holder pursuant to the terms hereof,  and the Company shall have
no further  obligation to pay any principal amount of or accrued interest on the
portion of this Convertible Note which was so converted by the holder.

                  3. Collection  Fees. In the event of default  hereunder and if
this  Convertible  Note is placed in the hands of any  attorney  for  collection
(whether or not suit is filed), or if this Convertible Note is collected by suit
or legal proceedings or through  bankruptcy  proceedings,  the Company agrees to
pay in addition to all sums then due hereon,  including  principal and interest,
all reasonable attorney's fees.

                  4. Registered  Owner;  Transfer.  The Company and any agent of
the Company may treat the person or entity  identified in the initial  paragraph
of this  Convertible  Note as the  absolute  owner  hereof  for the  purpose  of
receiving payment of, or on account of, the principal or interest due hereon and
for all other  purposes,  and  neither  the  Company nor any such agent shall be
affected  by notice to the  contrary.  Subject  to  compliance  with  applicable
federal and state securities laws, this Convertible Note is transferable only on
the books of the  Company  (at its  offices  or agency to be  maintained  in The
Woodlands, Texas) by the registered holder in person or by attorney on surrender
of this Convertible Note properly endorsed.

                  5. No Recourse Against  Individuals.  This Convertible Note is
the obligation of the Company only, and no recourse shall be had for the payment
hereof or the interest hereon against any incorporator, shareholder, director or
officer  as such  (whether  past,  present  or  future)  of the  Company  or any
successor entity whether by virtue of any  constitution,  statute or rule of law
or equity, or by the enforcement of any assessment of penalty, or otherwise, all
such  liability of the  incorporators,  shareholders,  directors and officers as
such being expressly  waived and released by the holder hereof by the acceptance
of this Convertible Note.

                  6. Amendments and Waivers. The holder of this Convertible Note
may waive or otherwise consent to the amendment of any of the provisions hereof.

                  7. Maximum Rate of Interest. Notwithstanding any provisions to
the  contrary in this  Convertible  Note,  or in any of the  documents  relating
hereto,  in no event shall this Convertible  Note or such documents  require the
payment or permit the collecting of interest in



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excess of the maximum amount permitted by the laws of the State of Texas. If any
such  excess  interest  is  contracted  for,  charged  or  received  under  this
Convertible Note or under the terms of any of the documents  relating hereto, or
in the event the maturity of the indebtedness evidenced by this Convertible Note
is  accelerated  in whole or in part,  or in the  event  that all or part of the
principal or interest of this Convertible  Note shall be prepaid,  so that under
any of such  circumstances  the amount of interest  contracted  for,  charged or
received  under this  Convertible  Note or under any of the  documents  relating
hereto, on the amount of principal actually  outstanding from time to time under
this Convertible Note, shall exceed the maximum amount of interest  permitted by
the laws of the State of Texas,  then in any such  event (a) the  provisions  of
this paragraph  shall govern and control,  (b) neither the Company nor any other
person or entity  now or  hereafter  liable  for the  payment  hereof,  shall be
obligated to pay the amount of such  interest to the extent that it is in excess
of the maximum  amount of interest  permitted by the laws of the State of Texas,
(c) any such excess which may have been  collected  shall be either applied as a
credit  against  the then  unpaid  principal  amount  hereof or  refunded to the
Company, at the holder's option, and (d) the effective rate of interest shall be
automatically  reduced to the maximum lawful rate of interest  allowed under the
laws of the State of Texas as now or hereafter  construed  by the courts  having
jurisdiction  thereof.  It is further  agreed  that  without  limitation  of the
foregoing,  all calculations of the rate of interest  contracted for, charged or
received under this  Convertible  Note or under such other  documents  which are
made for the purpose of determining whether such rate exceeds the maximum lawful
rate of  interest,  shall be made,  to the extent  permitted  by the laws of the
State of Texas, by amortizing,  prorating,  allocating and spreading  during the
period  of the  full  stated  term of the  indebtedness  evidenced  hereby,  all
interest at any time  contracted  for,  charged or received  from the Company or
otherwise by the holder or holders hereof in connection with such indebtedness.

                  8. Restrictions on Transferability.  This Convertible Note and
the  Conversion  Shares which may be acquired upon  conversion  hereof have been
acquired for investment and have not been registered under the Securities Act of
1933, as amended,  or the  securities  laws of any state or other  jurisdiction.
Without  such   registration,   such  securities  may  not  be  sold,   pledged,
hypothecated or otherwise transferred, except upon delivery to the Company of an
opinion of counsel satisfactory to the Company that registration is not required
for such transfer, or submission to the Company of such other evidence as may be
reasonably  satisfactory  to the  Company to the effect  that any such  transfer
shall not be in  violation of the  Securities  Act of 1933,  as amended,  or any
applicable  state  or  foreign   securities  laws  or  any  rule  or  regulation
promulgated   thereunder.   Notwithstanding   the  above,  the  holder  of  this
Convertible Note has been provided certain  registration  rights with respect to
the Conversion  Shares which may be acquired upon conversion  hereof pursuant to
the Amendment No. 4 to License and  Development  Agreement of even date herewith
between  the  Company  and  such  holder  (the  "Fourth   Amendment  to  License
Agreement").

                  9. Default;  Acceleration.  An Event of Default  exists if the
Company fails to pay interest  within five days following the date due; fails to
pay principal  within three days  following  the date due;  fails to perform any
other  obligations  within  twenty days of notice;  is subject to a voluntary or
involuntary  bankruptcy proceeding and such involuntary proceeding is not stayed
or  dismissed  within sixty days;  if a default by the Company  exists under the
Development   Agreement  between  the  Company  and  Genzyme  Corporation  dated
September 10, 1993, as amended, or the

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Common Stock  Purchase  Warrant of even date  herewith  issued by the Company to
Genzyme  Corporation  pursuant  to  the  Amendment  No.  4 to  such  Development
Agreement,  which default,  in either case, has not been remedied by the Company
prior to the expiration of any applicable  grace period;  or if the Common Stock
of the  Company is no longer  listed for trading on The Nasdaq  Stock  Market or
other  national  securities  exchange.  In the event of any  default  under this
Convertible  Note by the  Company,  provided  there is no  agreement  for waiver
thereof or the Company has not cured such  default,  then,  at the option of the
holder of the Convertible  Note, the Convertible Note shall thereupon become and
be due and payable, without any other presentment,  demand, protest or notice of
any kind, all of which are hereby expressly waived.

                  10.      Adjustment of Conversion Price.

         (a) The  Conversion  Price and the number of Conversion  Shares and the
number or amount of any other  securities and property as  hereinafter  provided
into  which  this  Convertible  Note  may be  convertible  shall be  subject  to
adjustment  from  time to time  effective  upon  each  occurrence  of any of the
following events.

         (b) If the Company  shall  declare or pay any dividend  with respect to
its Common Stock  payable in shares of Common Stock,  subdivide the  outstanding
Common  Stock  into a greater  number of shares of Common  Stock,  or reduce the
number of shares of Common  Stock  outstanding  (by stock split,  reverse  stock
split,  reclassification  or otherwise  than by  repurchase of its Common Stock)
(any of such events being  hereinafter  called a "Stock Split"),  the Conversion
Price  and  number  of  Conversion  Shares  issuable  upon  conversion  of  this
Convertible  Note shall be  appropriately  adjusted  so as to entitle the holder
hereof  to  receive  upon  conversion  of this  Convertible  Note,  for the same
aggregate  consideration  provided  herein,  the same number of shares of Common
Stock (plus cash in lieu of fractional shares) as the holder would have received
as a result of such Stock Split had such holder  converted this Convertible Note
in full immediately prior to such Stock Split.

         (c) If the Company shall merge or consolidate  with or into one or more
corporations or partnerships and the Company is the sole surviving  corporation,
or the Company shall adopt a plan of recapitalization or reorganization in which
the Common  Stock is exchanged  for or changed  into  another  class of stock or
other security or property of the Company,  the holder of this  Convertible Note
shall, for the same aggregate  consideration  provided herein,  be entitled upon
conversion of this  Convertible  Note to receive in lieu of the number of shares
of  Common  Stock  as  to  which  this   Convertible  Note  would  otherwise  be
convertible, the number of shares of Common Stock or other securities (plus cash
in lieu of  fractional  shares) or property to which such holder would have been
entitled   pursuant  to  the  terms  of  the   agreement   or  plan  of  merger,
consolidation, recapitalization or reorganization had such holder converted this
Convertible  Note in full  immediately  prior  to  such  merger,  consolidation,
recapitalization or reorganization.

         (d) If the Company is merged or  consolidated  with or into one or more
corporations or partnerships under circumstances in which the Company is not the
sole  surviving  corporation,  or if the Company sells or otherwise  disposes of
substantially all its assets, and in connection with any

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such merger,  consolidation or sale the holders of Common Stock receive stock or
other  securities   convertible  into  equity  of  the  surviving  or  acquiring
corporations  or entities,  or other  securities or property after the effective
date of such merger,  consolidation  or sale,  as the case may be, the holder of
this  Convertible  Note shall,  for the same  aggregate  consideration  provided
herein, be entitled upon conversion of this Convertible Note to receive, in lieu
of the shares of Common Stock as to which this  Convertible Note would otherwise
be convertible,  shares of such stock or other  securities (plus cash in lieu of
fractional shares) or property as the holder of this Convertible Note would have
received  pursuant  to the terms of the merger,  consolidation  or sale had such
holder converted this Convertible Note in full immediately prior to such merger,
consolidation  or sale.  In the  event of any  consolidation,  merger or sale as
described in this Section 9(d),  provision shall be made in connection therewith
for the  surviving  or  acquiring  corporations  or  partnerships  to assume all
obligations and duties of the Company hereunder or to issue a substitute note in
lieu of this  Convertible  Note with all such  changes  and  adjustments  in the
number or kind of shares of stock or securities or property  thereafter  subject
to this  Convertible  Note or in the  Conversion  Price as shall be  required in
connection with this Section 9(d).

         (e) If the  Company,  at any time after the date  hereof and before the
Due Date,  shall issue or sell or fix a record date for the  issuance of rights,
options,  warrants or convertible or  exchangeable  securities to all holders of
Common  Stock  entitling  them to  subscribe  for or purchase  Common  Stock (or
securities  convertible  into  Common  Stock) at a price per share (or  having a
conversion price per share),  that together with the value of any  consideration
paid for any such  rights,  options,  warrants or  convertible  or  exchangeable
securities  (as  determined  in good  faith  by the  Board of  Directors  of the
Company) is less than the fair market value of a share of Common Stock as of the
date of such issuance or sale or on such record date;  then,  immediately  after
the date of such issuance or sale or on such record date,  the holder shall have
the right to receive,  upon the same terms as the holders of Common  Stock,  the
kind and amount of rights,  options,  warrants or  convertible  or  exchangeable
securities  receivable in such  offerings by a holder of the number of shares of
Common Stock that the holder would have been entitled to receive upon conversion
of this  Convertible Note pursuant to Section 1 hereof had such Convertible Note
been  converted  immediately  before  such  issuance or the record date for such
issuance.

         (f) If (other than in  dissolution  or  liquidation)  securities of the
Company  (other than shares of Common Stock or securities  issued  pursuant to a
shareholder rights or similar plan) or assets are issued by way of a dividend on
outstanding  shares of Common Stock, then the Conversion Price shall be adjusted
so that it shall equal the price  determined by multiplying the Conversion Price
by a fraction, the numerator of which shall be the last sale price of the Common
Stock on such record date less the then fair market value as  determined  by the
Board of  Directors  of the company of the portion of the  securities  or assets
distributed  applicable to one share of Common  Stock,  and the  denominator  of
which shall be such last sale price.  Such  adjustment  shall  become  effective
immediately  prior to the opening of business on the day  following  such record
date.

         (g) If the Company  (other than in connection  with a sale described in
Section 9(d)) proposes to liquidate and dissolve,  the Company shall give notice
thereof as provided in Section  10(b) hereof and shall permit the holder of this
Convertible Note to convert any unconverted

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portion hereof at any time within the 10 day period  following  delivery of such
notice,  if such holder should elect to do so, and  participate as a stockholder
of the Company in connection with such dissolution.

         (h)      Whenever any adjustment is made as provided in any provision
                  of this Section 9:

                           (i) the  Company  shall  compute the  adjustments  in
                  accordance with this Section 9 and shall prepare a certificate
                  signed by an officer of the Company setting forth the adjusted
                  number  of  shares  or  other   securities   or  property  and
                  Conversion  Price,  as  applicable,  and showing in reasonable
                  detail the facts upon which such adjustment is based, and such
                  certificate  shall  forthwith be filed with the Company or its
                  designee; and

                           (ii) a notice  setting  forth the adjusted  number of
                  shares or other  securities  or  property  and the  Conversion
                  Price, as applicable, shall forthwith be required, and as soon
                  as  practicable  after it is  prepared,  such notice  shall be
                  delivered  by the  Company  to the  holder  of  record of this
                  Convertible Note.

         (i) If at any time, as a result of any adjustment made pursuant to this
Section  9, the holder of this  Convertible  Note shall  become  entitled,  upon
exercise  hereof,  to receive any shares other than shares of Common Stock or to
receive any other  securities,  the number of such other shares or securities so
receivable  upon  conversion  of this  Convertible  Note  shall  be  subject  to
adjustment  from time to time in a manner and on terms as nearly  equivalent  as
practicable  to the  provisions  contained in this Section 9 with respect to the
Common Stock.

         10.      Special Agreements of the Company.

         (a) The Company covenants and agrees that it will reserve and set apart
and have at all times a number of shares of authorized but unissued Common Stock
then  deliverable  upon the  conversion  of this  Convertible  Note or any other
rights or privileges  provided for herein sufficient to enable it at any time to
fulfill  all  its  obligations  hereunder;  and if at any  time  the  number  of
authorized but unissued shares of Common Stock shall not be sufficient to effect
the conversion of this  Convertible Note at the Conversion Price then in effect,
the Company will take such corporate action as may, in the reasonable opinion of
its counsel,  be necessary to increase its authorized shares but unissued shares
of  Common  Stock to such  number  of  shares  as shall be  sufficient  for such
purposes.

         (b)      In case the Company proposes

                  (i)    to pay  any  dividend  upon  the  Common  Stock  or
                         make any distribution or offer any subscription or
                         other rights to the holders of Common Stock, or

                  (ii)   to  effect  any  capital  reorganization  or
                         reclassification  of  capital  stock  of the
                         Company,


                                      -18-






                 (iii)   to effect the consolidation, merger, sale of all or
                         substantially all of the assets, liquidation,
                         dissolution or winding up of the Company,

                 (iv)    to effect a rights offering to its stockholders, or

                  (v)    to   conduct  a   self-tender   offer  or  other
                         repurchase  of  outstanding  shares of Company  Common
                         Stock, other than in connection with  repurchases from
                         employees upon termination of their employment,

then the Company shall cause notice of any such  intended  action to be given to
the holder of this Convertible Note not less than 15 nor more than 60 days prior
to the date on which the transfer  books of the Company  shall close or a record
be taken for such  dividend  or  distribution,  or the date  when  such  capital
reorganization,  reclassification,  consolidation,  merger,  sale,  liquidation,
dissolution or winding up shall be effected, or the date of such other event, as
the case may be.

         11. Notices.  Any notice or other document  required or permitted to be
given or  delivered to the holder of this  Convertible  Note shall be in writing
and sent (a) by telecopy if the sender on the same day sends a  confirming  copy
of such notice by a recognized overnight delivery service (charges prepaid),  or
(b) by  registered  or certified  mail with return  receipt  requested  (postage
prepaid)  or  (c) by a  recognized  overnight  delivery  service  (with  charges
prepaid).

                  (i) if to the Company, at Aronex Pharmaceuticals, Inc., 8707
         Technology Forest Drive, The Woodlands, Texas 77381, Telecopy No.:
         (281) 367-1676, or such other address as it shall have specified to
         the holder of this Convertible Note in writing; or

                  (ii) if to a holder,  at its address set forth below,  or such
         other address as it shall have specified to the Company in writing.

Notices  given under this  Section 11 shall be deemed  given only when  actually
received.

                  12.  Governing Law. This Convertible Note shall be governed by
and  construed in  accordance  with the laws of the State of  Delaware,  without
reference to the conflicts of law principles thereof.




                                      -19-





                  IN WITNESS  WHEREOF,  the Company has caused this  Convertible
Note to be duly executed as of the 21st day of May, 1999.


                                       ARONEX PHARMACEUTICALS, INC.


                                       By:   /s/ Geoffrey F. Cox
                                             ----------------------------------
                                       Name: Geoffrey F. Cox
                                             ----------------------------------
                                       Title: Chairman of the Board & Chief
                                              Executive Officer
                                             ----------------------------------




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