ARONEX PHARMACEUTICALS INC
POS AM, 1996-07-30
PHARMACEUTICAL PREPARATIONS
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      As filed with the Securities and Exchange Commission on July 29, 1996

                            Registration No. 33-91584

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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


                         POST-EFFECTIVE AMENDMENT NO. 1
                                       TO
                                    FORM S-4
                                       ON
                                    FORM S-3

             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

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


                          ARONEX PHARMACEUTICALS, INC.
             (Exact name of Registrant as specified in its charter)

                  Delaware                      76-0196535
      (State or other jurisdiction of        (I.R.S. Employer
       incorporation or organization)      Identification Number)

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


                           3400 Research Forest Drive
                           The Woodlands, Texas 77381
                                 (713) 367-1666
(Address,  including zip code,  and telephone  number,  including  area code, of
registrant's principal executive offices)

                                 James M. Chubb
                                    President
                           3400 Research Forest Drive
                           The Woodlands, Texas 77381
                                 (713) 367-1666
(Name, address,  including zip code, and telephone number,  including area code,
of agent for service)

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

                                   Copies to:
                             Andrews & Kurth L.L.P.
                        2170 Buckthorne Place, Suite 150
                           The Woodlands, Texas 77380
                               Jeffrey Wade, Esq.
                                 (713) 220-4801
                      ------------------------------------


If the only securities  being registered on this Form are being offered pursuant
to a dividend or interest reinvestment plans, please check the following box:|_|

If any of the  securities  being  registered on this Form are to be offered on a
delayed or continuous  basis  pursuant to Rule 415 under the  Securities  Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. |X|

If this Form is filed to register additional securities for an offering pursuant
to Rule 462(b) under the Securities Act, please check the following box and list
the  Securities  Act  registration  statement  number of the  earlier  effective
registration statement for the same offering. |_|

If this Form is a  post-effective  amendment filed pursuant to Rule 462(c) under
the  Securities  Act,  check  the  following  box and  list the  Securities  Act
registration  statement number of the earlier effective  registration  statement
for the same offering. |_|

If delivery  of the  prospectus  is  expected  to be made  pursuant to Rule 434,
please check the following box. |_|



                                                 

<PAGE>



                      [Aronex Pharmaceuticals, Inc. Logo]





                               3,220,000 Shares of
                                  Common Stock
                       Issuable Upon Exercise of Warrants

         Aronex  Pharmaceuticals,  Inc., a Delaware corporation ("Aronex" or the
"Company")  is offering up to  3,220,000  shares  (the  "Shares")  of its Common
Stock, par value $0.001 per share ("Common  Stock"),  issuable upon the exercise
of outstanding warrants to purchase Common Stock ("Warrants").  The Common Stock
is quoted on the Nasdaq National Market under the trading symbol "ARNX". On July
26,  1996,  the last  reported  sale  price of the  Common  Stock on the  Nasdaq
National Market was $6-7/8 per share.

         Each  Warrant  entitles,  or upon  issuance  will  entitle,  the holder
thereof  to  purchase  one share of Common  Stock and is  subject  to a Series A
Exercise,  Series B  Exercise  and a  Series  C  Exercise.  Subject  to  certain
exceptions,  holders of the  Warrants  were  required to  exercise  the Series A
Exercise,  in whole but not in part, prior to December 28, 1995 (January 2, 1996
after  allowance  of a five day grace  period).  The holders who  exercised  the
Series A Exercise have the right, prior to June 11, 1998, to exercise the Series
B Exercise,  in whole but not in part, at an effective  exercise  price of $8.00
per share.  In the event the Series B Exercise  has been  exercised by a holder,
then prior to December 11,  1999,  the Series C Exercise  may be  exercised,  in
whole but not in part,  at an  effective  exercise  price of $12.00 per share of
Common  Stock.  Aronex has the right,  at its  option,  to convert a Series B or
Series C Exercise into a "cashless" exercise based on the value of a Series B or
Series C Exercise  (equal to the fair market value per share of the Common Stock
less the  exercise  price per share)  divided by the market  price of the Common
Stock at the time of  exercise.  Prior to the  purchase of Common Stock upon the
exercise of a Warrant,  the holder of a Warrant  will have none of the rights or
privileges of a stockholder of the Company.

         The number of Shares and the exercise prices of the Series B and Series
C Exercise  give effect to a one-for- two reverse split of the Common Stock that
was effected on July 1, 1996.

         The Common Stock  offered  hereby  involves a high degree of risk,  see
"Risk Factors" on page 5 of this Prospectus.

           THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE
             SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES
                   COMMISSION NOR HAS THE SECURITIES AND EXCHANGE
                   COMMISSION OR ANY STATE SECURITIES COMMISSION
                      PASSED UPON THE ACCURACY OR ADEQUACY OF
                      THIS PROSPECTUS.  ANY REPRESENTATION TO
                         THE CONTRARY IS A CRIMINAL OFFENSE.


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


                  The date of this Prospectus is July 29, 1996.

                                                 

<PAGE>



                              AVAILABLE INFORMATION

         The  Company  is  subject  to  the  informational  requirements  of the
Securities  Exchange  Act  of  1934,  as  amended  (the  "Exchange  Act"),  and,
accordingly,  files reports,  proxy  statements and other  information  with the
Securities and Exchange Commission (the "SEC").  Such reports,  proxy statements
and other  information  filed  with the SEC are  available  for  inspection  and
copying at the public reference  facilities  maintained by the SEC at Room 1024,
Judiciary Plaza, 450 Fifth Street, N.W., Washington,  DC 20549, and at the SEC's
Regional  Offices located at Citicorp  Center,  500 West Madison  Street,  Suite
1400, Chicago,  Illinois 60661 and at Seven World Trade Center,  Suite 1300, New
York,  New York 10048.  Copies of such  documents  may also be obtained from the
Public Reference Section of the SEC at Judiciary Plaza, 450 Fifth Street,  N.W.,
Washington, DC 20549, at prescribed rates. The SEC maintains a site on the World
Wide Web at http://www.sec.gov that contains reports, proxy statements and other
information  regarding  registrants  that file  electronically  with the SEC. In
addition,  such  materials and other  information  concerning the Company can be
inspected  at the National  Association  of  Securities  Dealers,  Inc.,  1735 K
Street, N.W., Washington, DC 20006.

         The  Company  has  filed  with the SEC a  registration  statement  (the
"Registration  Statement")  under the  Securities  Act of 1933,  as amended (the
"Securities  Act"),  on  Form  S-4  (Reg.  No.  33-91584)  with  respect  to the
securities  offered  hereby.  This  Prospectus  does  not  contain  all  of  the
information set forth in the  Registration  Statement and the exhibits  thereto,
certain parts of which are omitted in accordance  with the rules and regulations
of the  SEC.  Statements  made  in this  Prospectus  as to the  contents  of any
contract,  agreement or other document referred to are not necessarily complete.
With  respect to each such  contract,  agreement or other  document  filed as an
exhibit to the  Registration  Statement,  reference is made to the exhibit for a
more complete description of the matter involved. The Registration Statement and
any amendments thereto, including exhibits filed or incorporated by reference as
a part thereof, are available for inspection and copying at the SEC's offices as
described above.

                       DOCUMENTS INCORPORATED BY REFERENCE

         The following documents,  which have been filed by the Company with the
SEC, are incorporated by reference into this Prospectus:

          1.   The Annual Report on Form 10-K for the fiscal year ended December
               31, 1995, as amended; and

          2.   The Quarterly  Report on Form 10-Q for the quarterly period ended
               March 31, 1996;

          3.   The Quarterly  Report on Form 10-Q for the quarterly period ended
               June 30, 1996; and

          4.   The  description  of the Common Stock  contained in the Company's
               Registration   Statement  on  Form  8-A  filed  April  23,  1992,
               including  any  amendments  and reports  filed for the purpose of
               updating such description.

         All reports  and  documents  filed by the  Company  pursuant to Section
13(a),  13(c),  14 or 15(d)  of the  Exchange  Act,  prior  to the  filing  of a
post-effective amendment which indicates that all securities offered hereby have
been sold or which  deregisters all securities then remaining  unsold,  shall be
deemed to be incorporated  by reference  herein and to be a part hereof from the
respective date of filing of such documents.  Any statement  contained herein or
in a  document  all or a  portion  of  which is  incorporated  or  deemed  to be
incorporated  by reference  herein shall be deemed to be modified or  superseded
for purposes of this Prospectus to the extent that a statement  contained herein
or in any  other  subsequently  filed  document  that also is or is deemed to be
incorporated by reference herein modifies or supersedes such statement. Any such
statement so modified or superseded  shall not be deemed,  except as so modified
or superseded, to constitute a part of this Prospectus.

          This  Prospectus  incorporates  documents by  reference  which are not
presented herein or delivered herewith. The Company hereby undertakes to provide
without charge to each person, including any beneficial owner, to whom a copy of
this Prospectus has been  delivered,  on the written or oral request of any such
person, a copy of any and all of the documents referred to above which have been
or may be incorporated in this Prospectus

                                               
                                       -2-

<PAGE>



by reference,  other than exhibits to such  documents  (unless such exhibits are
specifically  incorporated by reference into such documents).  Such requests for
documents  should be directed to Aronex  Pharmaceuticals,  Inc.,  3400  Research
Forest  Drive,  The  Woodlands,  Texas  77381,  Attention:  Investor  Relations,
telephone number (713) 367-1666.

         No  person  is  authorized  to give  any  information  or to  make  any
representation  not contained in this  Prospectus,  and, if given or made,  such
information or representation must not be relied upon as having been authorized.
This  Prospectus  does not constitute an offer to sell, or a solicitation  of an
offer to purchase,  any of the  securities  offered by this  Prospectus,  or the
solicitation of a proxy, in any jurisdiction in which, or to any person to whom,
it is  unlawful  to make  such  offer  or  solicitation  of an  offer  or  proxy
solicitation.  Neither the delivery of this  Prospectus nor any  distribution of
the  securities  offered  hereby  shall,  under any  circumstances,  create  any
implication  that the  information  contained  herein is  correct as of any time
subsequent to the date hereof or that there has been no change in the affairs of
the Company since the date hereof.





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




                                                  
                                                        -3-

<PAGE>



                                   THE COMPANY

         The  following  is  qualified  in its  entirety  by the  more  detailed
information  appearing  elsewhere in this  Prospectus,  and by the more detailed
information and financial statements,  including notes thereto,  included in the
Company's Annual Report on Form 10-K for the year ended December 31, 1995 and in
subsequent  reports  filed  pursuant to Section 13 or 15(d) of the Exchange Act,
which are incorporated by reference herein.

         Aronex is a leading  biopharmaceutical company engaged in the discovery
and  development  of  proprietary  innovative  medicines  to  treat  cancer  and
life-threatening  infectious diseases. The Company's strategy is to discover and
develop  medicines  based upon either  refinements of proven  therapies or novel
mechanisms  of action  against  specific  disease  targets.  The  Company  has a
portfolio  of clinical  and  preclinical  products  that it believes  provides a
balanced  development and  commercialization  risk profile. The Company believes
its focus on medicines for cancer and  life-threatening  infectious diseases for
which  current  therapy  is  inadequate  will  provide  synergies  in  research,
development   and   product   marketing,    and   will   facilitate    expedited
commercialization of its products.

         Aronex  currently  has four  products  in  various  stages  of  ongoing
clinical  development  and a number of products in preclinical  development.  In
addition,  the Company has  proprietary  technologies in drug discovery and drug
formulation  that  should  continue  to  provide  a  significant   research  and
development   pipeline.   The  Company's  four  products  in  ongoing   clinical
development are listed below:

<TABLE>
<CAPTION>

                                                                                           Clinical
         Product                                  Indications                               Status
<S>                                      <C>                                          <C>    

Nyotran TM                               Systemic Fungal Infections                   Phase III
TretinoinLF                              Acute Promyelocytic Leukemia                 Phase II
                                         Kaposi's Sarcoma (a skin cancer)             Phase II/III
Annamycin                                Breast Cancer                                Phase I/II
ZintevirTM                               HIV Infection                                Phase I
</TABLE>

         The Company has strategic alliances and collaboration arrangements with
leading  corporations and academic  institutions,  including Genzyme Corporation
("Genzyme"),  Hoechst Marion Roussel, Inc. ("Hoechst"),  The University of Texas
M.D.  Anderson  Cancer Center ("MD Anderson") and The Baylor College of Medicine
("Baylor").

          The Company was  incorporated in 1986 as Argus  Pharmaceuticals,  Inc.
("Argus").   Argus   acquired   Oncologix,   Inc.   ("Oncologix")   and  Triplex
Pharmaceutical   Corporation   ("Triplex")   through  a  three-way  merger  (the
"Mergers")  in September  1995,  at which time Argus  changed its name to Aronex
Pharmaceuticals,   Inc.  The  merger  of  these  three  complementary  companies
established  an  integrated  company with the following  characteristics:  (i) a
clear therapeutic focus in cancer and life-threatening infectious diseases; (ii)
a well-defined  and diverse  portfolio of products at various stages of clinical
and  preclinical  development;  (iii)  a  broad-based  platform  of  synergistic
technologies  and  scientific  expertise;  (iv) a  diverse  group  of  corporate
partners and academic  affiliations;  and (v) an experienced  team of scientific
and biopharmaceutical  personnel who possess the ability to discover and develop
novel products,  design and implement complex clinical trials, manage regulatory
issues,  develop manufacturing  processes and implement the commercialization of
products.  Unless the context otherwise requires,  references in this Prospectus
to  "Aronex"  and the  "Company"  refer  to  Aronex  and its  subsidiaries.  The
Company's  corporate  headquarters is located at 3400 Research Forest Drive, The
Woodlands, Texas 77381, and its telephone number is (713) 367-1666.



                                                  
                                       -4-

<PAGE>



                                  RISK FACTORS

         In  evaluating  the Company  and its  business,  prospective  investors
should  consider  carefully  the  following  risk  factors,  together  with  the
information   and  financial  data  set  forth  in  the  reports  and  documents
incorporated by reference herein, prior to purchasing any shares of Common Stock
offered hereby.

         Early Stage of Development;  History of Operating Losses;  Anticipation
of Future Losses.  The Company is a development stage company.  It has generated
no revenues from product sales,  and it does not expect to generate revenue from
product sales for several years. As of June 30, 1996, the Company's  accumulated
deficit  was $48.6  million.  To date,  the Company  has  dedicated  most of its
financial  resources to the research and  development  of products,  general and
administrative expenses, and the prosecution of patents and patent applications.
The Company expects to incur significant and increasing  operating losses for at
least the next several years, primarily due to the expansion of its research and
development  programs,  including  preclinical  studies and clinical trials, and
costs  associated  with the  commercialization  of its  products  if  regulatory
approvals are  received.  The Company's  ability to achieve  profitability  will
depend,  among other  things,  on  successfully  completing  development  of its
products, obtaining regulatory approvals, establishing manufacturing,  sales and
marketing  capabilities or collaborative  arrangements,  and raising  sufficient
funds to finance its activities. There can be no assurance that the Company will
be able to achieve  profitability  or that  profitability,  if achieved,  can be
sustained.

         Future Capital Needs;  Uncertainty of Additional  Funding.  The Company
has experienced  negative cash flows from operations since its inception and has
funded its activities to date primarily from equity financings.  The Company has
expended,  and will continue to require,  substantial funds to continue research
and  development,  including  preclinical  studies  and  clinical  trials of its
products,  and to commence sales and marketing efforts if United States Food and
Drug Administration (the "FDA") and other regulatory approvals are obtained. The
Company expects that its existing  capital  resources will be sufficient to fund
its capital  requirements  through  1998.  Thereafter,  the Company will need to
raise  substantial  additional  capital to fund its  operations.  The  Company's
capital  requirements  will  depend on many  factors,  including  the  problems,
delays,  expenses and complications  frequently encountered by development stage
companies;  the progress of the  Company's  research,  development  and clinical
trial programs;  the Company's  ability to satisfy certain  milestones under its
current  collaborative  arrangements  with Genzyme and  Hoechst;  the extent and
terms of any future collaborative  research,  manufacturing,  marketing or other
funding  arrangements;  the costs and timing of seeking regulatory  approvals of
the Company's  products;  the Company's ability to obtain regulatory  approvals;
the success of the  Company's  sales and  marketing  programs;  costs of filing,
prosecuting and defending and enforcing any patent claims and other intellectual
property rights; and changes in economic,  regulatory or competitive  conditions
or the Company's planned  business.  Estimates about the adequacy of funding for
the  Company's  activities  are  based on  certain  assumptions,  including  the
assumption  that testing and  regulatory  procedures  relating to the  Company's
products can be conducted at  projected  costs.  There can be no assurance  that
changes in the Company's research and development plans, acquisitions,  or other
events will not result in accelerated or unexpected expenditures. To satisfy its
capital  requirements,  the  Company may seek to raise  additional  funds in the
public or private capital  markets.  The Company's  ability to raise  additional
funds in the public or private markets will be adversely affected if the results
of its current or future clinical trials are not favorable. The Company may seek
additional   funding  through  corporate   collaborations  and  other  financing
vehicles.  There can be no assurance  that any such funding will be available to
the Company on favorable  terms or at all. If adequate  funds are not available,
the Company may be required to curtail significantly one or more of its research
or  development  programs,  or it  may  be  required  to  obtain  funds  through
arrangements with future  collaborative  partners or others that may require the
Company to relinquish rights to some or all of its technologies or products.  If
the Company is successful in obtaining additional  financing,  the terms of such
financing may have the effect of diluting or adversely affecting the holdings or
the rights of the holders of the Company's Common Stock.


                                                   
                                       -5-

<PAGE>



         Uncertainties  Related to  Clinical  Trial  Results.  The FDA and other
regulatory  authorities generally require that the safety and efficacy of a drug
be  supported by results from  adequate and  well-controlled  Phase III clinical
trials before approval for commercial  sale. The Company has limited  experience
in  conducting  and managing  Phase III clinical  trials.  If the results of the
Company's  clinical  trials do not  demonstrate  the safety and  efficacy of its
products in the treatment of patients suffering from the diseases for which such
products  are being  tested,  the Company  will not be able to submit a New Drug
Application  ("NDA") to the FDA.  Clinical trials conducted on a fast-track,  or
expedited, basis may carry a higher risk that data will not be favorable or that
the FDA will not accept the NDA for submission than do Phase III clinical trials
developed  from earlier  clinical  trials with large  populations  using similar
protocols.   Even  if  the  Company  believes  the  Phase  III  clinical  trials
demonstrate  the safety and  efficacy of a product in the  treatment of disease,
the FDA and other regulatory authorities may not accept the Company's assessment
of the  results.  In either  case,  the Company  may have to conduct  additional
clinical  trials in an effort to  demonstrate  the  safety and  efficacy  of the
product.  Without acceptable results and regulatory  approval,  the Company will
not be able to commercialize  its products,  which would have a material adverse
effect on the Company.  There can be no assurance that the results of any of the
Company's  clinical  trials will be favorable  or that its products  will obtain
regulatory approval for commercialization.

          The results of preclinical  studies and initial clinical trials of the
Company's   products  are  not  necessarily   predictive  of  the  results  from
large-scale  clinical trials. The Company must demonstrate  through  preclinical
studies and clinical  trials that its products are safe and effective for use in
each target indication  before the Company can obtain  regulatory  approvals for
the  commercial  sale of those  products.  These  studies and trials may be very
costly and  time-consuming.  The speed with which the  Company is able to enroll
patients in clinical  trials is an important  factor in determining  how quickly
clinical  trials may be  completed.  Many  factors  affect  patient  enrollment,
including  the size of the  patient  population,  the  proximity  of patients to
clinical  sites,  and the  eligibility  criteria for the study.  A number of the
Company's  clinical trial protocols are targeted at indications  that have small
patient  populations,  which may make it  difficult  for the  Company  to enroll
enough  patients to complete  the trials.  Delays in patient  enrollment  in the
trials may result in increased costs,  program delays, or both, which could have
a material  adverse effect on the Company.  Even if the Company  establishes the
safety  and  efficacy  of its  products  and  obtains  FDA and other  regulatory
approvals for its products, physicians may not prescribe the approved product.

         The  administration  of any product the  Company  develops  may produce
undesirable  side  effects in  humans.  The  occurrence  of side  effects  could
interrupt or delay clinical  trials of products and could result in the FDA's or
other regulatory authorities' denying approval of the Company's products for any
or  all  targeted  indications.   The  Company,  the  FDA  or  other  regulatory
authorities  may suspend or terminate  clinical  trials at any time. Even if the
Company receives FDA and other regulatory approvals,  the Company's products may
later exhibit adverse effects that limit or prevent their widespread use or that
necessitate their withdrawal from the market. There can be no assurance that any
of the Company's products will be safe for human use.

         Government  Regulation;  No  Assurances  of  Regulatory  Approval.  The
Company's research and development  activities,  preclinical  studies,  clinical
trials,  and the  manufacturing  and  marketing  of its  products are subject to
extensive  regulation by the FDA and other regulatory  authorities in the United
States. These activities are also regulated in other countries where the Company
intends to test and market its products.

          Before  marketing,  any drug  developed by the Company must undergo an
extensive  regulatory approval process.  The regulatory process,  which includes
preclinical studies and clinical trials of each compound to establish its safety
and  efficacy,  takes many years and requires  the  expenditure  of  substantial
resources.   Data  obtained  from   preclinical  and  clinical   activities  are
susceptible to varying  interpretations  which could delay, limit or prevent FDA
regulatory  approval.  Although the FDA may have been  consulted  in  developing
protocols for clinical trials, that consultation  provides no assurance that the
FDA will accept the clinical trials as adequate or well-controlled or accept the
results of those trials.  Similarly, the FDA may determine that products are not
eligible for or will not receive  expedited  review,  whether or not the FDA has
previously indicated that such products may be eligible for expedited review. In
addition,  delays or  rejections  may be  encountered  based upon changes in FDA
policy  for drug  approval  during the  period of  product  development  and FDA
regulatory  review of each submitted NDA. Similar delays and rejections may also
be encountered in foreign countries.  There can be no assurance that, even after
such time and expenditures,  regulatory  approval will be obtained for any drugs
developed by the Company. Moreover, if regulatory approval of a drug is granted,
such approval may entail

                                                  
                                       -6-

<PAGE>



limitations on the indicated uses for which it may be marketed. Further, even if
such regulatory approval is obtained,  a marketed drug, its manufacturer and its
manufacturing   facilities   are  subject  to  continual   review  and  periodic
inspections,  and later discovery of previously unknown problems with a product,
manufacturer   or  facility  may  result  in  restrictions  on  the  product  or
manufacturers, including a withdrawal of the product from the market. Failure to
comply with the  applicable  regulatory  requirements  can,  among other things,
result in fines, suspensions of regulatory approvals, product recalls, operating
restrictions and criminal prosecution. Further, additional government regulation
may be  established  that could  prevent  or delay  regulatory  approval  of the
Company's products. A bill proposing comprehensive reform of FDA regulations has
been introduced in the United States Senate.  This bill addresses many facets of
FDA  regulations,  including  requirements  for NDA approval,  requirements  for
supplemental   approval,   off-label  information   dissemination,   and  export
regulations.  A counterpart  bill is expected to be  introduced  into the United
States House of Representatives.  It is not certain whether any such legislation
will be enacted  into law,  what form any law will take,  or what effect any new
law would have on the Company.

         The Company's  business is also subject to  regulation  under state and
federal laws regarding environmental  protection,  hazardous substances control,
and  exposure to  blood-borne  pathogens.  These laws  include the  Occupational
Safety and Health Act, the Environmental Protection Act, and the Toxic Substance
Control Act. Any violation of, and the cost of compliance  with,  these laws and
regulations  could adversely affect the Company.  There can be no assurance that
statutes or regulations applicable to the Company's business will not be adopted
that impose  substantial  additional  costs or  otherwise  materially  adversely
affect the Company's operations.

         Uncertainty of Protection for Patents and Proprietary  Technology.  The
Company's  ability to commercialize  any products will depend, in part, upon its
or its licensors'  ability to obtain  patents,  enforce those patents,  preserve
trade secrets,  and operate without  infringing  upon the proprietary  rights of
third  parties.   The  patent  positions  of  biotechnology  and  pharmaceutical
companies are highly uncertain and involve complex legal and factual  questions.
Some of the United States patents and patent  applications  owned by or licensed
to the Company are method-of-use patents that cover the use of certain compounds
to  treat  specified  conditions,  and  composition-of-matter  patents  are  not
available for some of the  Company's  product  candidates.  The Company does not
have any patents or patent  applications  with  respect to one of its  products,
AR102.  There can be no assurance  that the patent  applications  licensed to or
owned by the Company will result in issued patents,  that patent protection will
be secured for any particular technology, that any patents that have been or may
be issued to the Company or its licensors will be valid or enforceable, that any
patents will provide meaningful  protection to the Company, that others will not
be able to design around the patents, or that the Company's patents will provide
a competitive advantage or have commercial application.

         There can be no  assurance  that  patents  owned by or  licensed to the
Company will not be  challenged by others.  The Company could incur  substantial
costs in proceedings before the United States Patent Office and other regulatory
authorities,  including interference proceedings. These proceedings could result
in adverse  decisions about the  patentability  of the Company's  inventions and
products as well as about the  enforceability,  validity or scope of  protection
afforded by the patents.  The Company is currently  involved in an  interference
proceeding before the United States Patent Office regarding AR726.

          There can be no  assurance  that the  manufacture,  use or sale of the
Company's products will not infringe patent rights of others. The Company may be
unable to avoid  infringement  of those  patents and may have to seek a license,
defend an  infringement  action,  or  challenge  the  validity of the patents in
court.  There  can be no  assurance  that a  license  will be  available  to the
Company, if at all, upon terms and conditions  acceptable to the Company or that
the Company will prevail in any patent  litigation.  Patent litigation is costly
and time  consuming,  and there can be no  assurance  that the Company will have
sufficient resources to bring such litigation to a successful conclusion. If the
Company  does not  obtain a license  under  such  patents,  is found  liable for
infringement,  or is not able to have such patents declared invalid, the Company
may be liable for  significant  damages,  may  encounter  significant  delays in
bringing  products to market,  or may be  precluded  from  participating  in the
manufacture,  use or sale of products  or methods of  treatment  requiring  such
licenses.  There can be no  assurance  that the  Company has  identified  United
States and foreign patents that pose a risk of infringement.

                                                   
                                       -7-

<PAGE>





         The  Company  also  relies  upon  trade  secrets  and other  unpatented
proprietary information in its product development activities. To the extent the
Company  relies  on trade  secrets  and  unpatented  know-how  to  maintain  its
competitive  technological  position,  there can be no assurance that others may
not independently develop the same or similar technologies. The Company seeks to
protect trade secrets and proprietary knowledge, in part through confidentiality
agreements  with  its  employees,   consultants,   advisors  and  collaborators.
Nevertheless,  these  agreements may not effectively  prevent  disclosure of the
Company's  confidential  information  and may not provide  the  Company  with an
adequate remedy in the event of unauthorized disclosure of such information.  If
the  Company's  employees,   scientific  consultants  or  collaborators  develop
inventions  or processes  independently  that may be applicable to the Company's
products,  disputes  may arise about  ownership of  proprietary  rights to those
inventions and  processes.  Such  inventions and processes will not  necessarily
become the Company's  property,  but may remain the property of those persons or
their employers.  Protracted and costly litigation could be necessary to enforce
and determine the scope of the Company's  proprietary rights.  Failure to obtain
or maintain  patent and trade secret  protection,  for any reason,  would have a
material adverse effect on the Company.

         The Company engages in collaborations,  sponsored research  agreements,
licensing and other arrangements with academic researchers and institutions that
have received and may receive funding from United States government agencies. As
a result of these  arrangements,  the United States  government or certain third
parties  have rights in certain  inventions  developed  during the course of the
performance  of such  collaborations  and  agreements as required by law or such
agreements.

         Several  bills  affecting  patent  rights have been  introduced  in the
United  States  Congress.  These bills  address  various  aspects of patent law,
including  publication,   patent  term,   re-examination,   subject  matter  and
enforceability.  It is not  certain  whether  any of these bills will be enacted
into law or what form new laws may take. Accordingly,  the effect of legislative
change on the Company's intellectual property estate is uncertain.

         Manufacturing  Uncertainties;  Reliance on Third-Party  Suppliers.  The
Company does not operate and does not  currently  plan to operate  manufacturing
facilities for the production of its products in commercial  quantities,  and it
intends to contract  with third  parties for the  manufacture  and supply of its
products.  There can be no  assurance  that the  Company  will be able to obtain
supplies of its products  from  third-party  suppliers on terms or in quantities
acceptable to the Company.  Also, the Company's  dependence on third parties for
the  manufacture  of its products may  adversely  affect the  Company's  product
margins and its ability to develop and deliver  products on a timely basis.  Any
such third-party suppliers or any manufacturing facility the Company establishes
will be required to meet FDA  manufacturing  requirements.  FDA certification of
manufacturing  facilities for a drug is a prerequisite to approval of an NDA for
that drug. The Company may encounter  significant  delays in obtaining  supplies
from third-party  manufacturers or experience  interruptions in its supplies. If
the  Company  is unable to  obtain  adequate  supplies,  its  business  would be
materially adversely affected.

          Lack of Sales and Marketing Experience.  The Company does not have any
experience in sales,  marketing or distribution.  To market any of its products,
the  Company  must  develop  a  sales  and  marketing   force  with   supporting
distribution  capability or enter into marketing and  distribution  arrangements
with a  company  that  has an  established  capability.  Significant  additional
expenditures will be required for the Company to develop such capabilities.  The
Company  has entered  into a license  agreement  with  Genzyme  with  respect to
TretinoinLF,  and it plans to enter into marketing  agreements  with one or more
other pharmaceutical  companies to market other products that it may develop. To
the  extent  the  Company  relies  upon  licensing,  marketing  or  distribution
arrangements with others, any revenues the Company receives will depend upon the
efforts of third  parties.  There can be no assurance  that any third party will
market the Company's products successfully or that any third-party collaboration
will be on terms  favorable to the Company.  If any  marketing  partner does not
market a  product  successfully,  the  Company's  business  would be  materially
adversely  affected.  There can be no assurance that the Company will be able to
establish  sales,  marketing  and  distribution  capabilities  or that it or its
collaborators  will be successful in gaining market  acceptance for any products
that the Company may  develop.  The  Company's  failure to  establish  marketing
capabilities  or to enter into marketing  arrangements  with third parties would
have a material adverse effect on the Company.

                                                  
                                       -8-

<PAGE>

         Risks Associated with Collaborative Arrangements. The Company's product
development and  commercialization  strategy  involves the Company entering into
various  arrangements  with  corporate,  government and academic  collaborators,
licensors,  licensees and others.  As a consequence,  the Company's  success may
depend  on  the   success   of  these   other   parties  in   performing   their
responsibilities.  There can be no  assurance  that the Company  will be able to
establish additional  collaborative  arrangements or license agreements that are
necessary or desirable for the Company to develop and commercialize its products
or  that  any  such  collaborative   agreement  or  license  agreement  will  be
successful.   Some  of  the  Company's  collaborative   agreements  and  license
agreements provide for milestone payments to the Company, and others require the
Company to pay milestone  payments to others. No assurance can be given that the
Company will achieve the milestones  that trigger  payments to the Company,  nor
can  assurance  be  given  that  payments  by the  Company  will  result  in the
development of marketable  products.  No assurance can be given that any current
or future  collaborative  arrangement  will be renewed at the end of its term or
will be renewed on terms as favorable to the Company as its original terms.  The
Company's  collaboration  with  Hoechst  expires  at the end of 1996  unless the
parties agree to renew the arrangement.

         Competition  and  Technological  Change.  The  Company  is  engaged  in
pharmaceutical  product development  characterized by extensive research efforts
and  rapid   technological   progress.   Many  established   biotechnology   and
pharmaceutical  companies,  universities  and other research  institutions  with
resources  significantly  greater than the Company's  may develop  products that
directly  compete with the  Company's  products.  Those  entities may succeed in
developing  products,  including  liposomes and lipid-based  products,  that are
safer,  more effective or less costly than the Company's  products.  Even if the
Company's  products  should prove to be more effective  than those  developed by
other companies, other companies may be more successful than the Company because
of greater financial resources, greater experience in conducting preclinical and
clinical trials and obtaining regulatory approval,  stronger sales and marketing
efforts,  earlier receipt of approval for competing  products and other factors.
If the Company commences significant commercial sales of its products, it or its
collaborators  will  compete  in areas in which  the  Company  has  little or no
experience such as manufacturing  and marketing.  There can be no assurance that
the Company's  products,  if commercialized,  will be accepted and prescribed by
healthcare professionals.

         Some of the  Company's  competitors  are active in the  development  of
liposome and  lipid-based  research and product  development to treat cancer and
certain fungal  infections.  Those competitors  include Sequus  Pharmaceuticals,
Inc.,  NeXstar  Pharmaceuticals,  Inc. and The Liposome  Company.  Some of those
companies'  products  have  regulatory  approval in the United  States and other
countries.  Any  marketing  of these  and  other  products  that  treat  disease
indications targeted by the Company could adversely affect the market acceptance
of the Company's  products as a result of the established market recognition and
physician  familiarity  with the  competing  product.  The  presence of directly
competitive  products could also result in more intense price  competition  than
might  otherwise  exist,  which  could  have a  material  adverse  effect on the
Company's  financial  condition and results of operations.  The Company believes
that competition will be intense for all of its products.

         No  Assurance  of Adequate  Third-Party  Reimbursement.  The  Company's
ability to commercialize  its products  successfully  will depend in part on the
extent to which  appropriate  reimbursement  levels for the cost of the products
and related treatment are obtained from government  authorities,  private health
insurers  and  other  organizations,  such as health  maintenance  organizations
("HMOs"). Third-party payors are increasingly challenging the prices charged for
medical products and services.  Accordingly, if less costly drugs are available,
third-party  payors may not authorize  reimbursement for the Company's  products
even if they offer  advantages  in safety or  efficacy.  Also,  the trend toward
managed  healthcare  and  government   insurance  programs  could  significantly
influence the purchase of healthcare  services and products,  resulting in lower
prices and reducing  demand for the  Company's  products.  The cost  containment
measures that healthcare  providers are  instituting  and any healthcare  reform
could affect the Company's  ability to sell its products and may have a material
adverse effect on the Company.

         There can be no assurance  that  reimbursement  in the United States or
foreign countries will be available for any of the Company's products,  that any
reimbursement  granted  will be  maintained,  or that  limits  on  reimbursement
available from third-party  payors will not reduce the demand for, or negatively
affect the price of, the Company's products. The unavailability or inadequacy of
third-party  reimbursement  for the  Company's  products  would  have a material
adverse effect on the Company. The Company is unable to forecast what additional
legislation  or regulation  relating to the 


                                      -9-

<PAGE>

healthcare industry or third-party  coverage and reimbursement may be enacted in
the  future,  or what effect the  legislation  or  regulation  would have on the
Company's business.

         Potential  Product  Liability;  Availability of Insurance.  The Company
risks exposure to product liability claims if the use of its products is alleged
to have an adverse effect on subjects or patients. This risk exists for products
tested in human clinical trials as well as products that are sold  commercially.
There can be no assurance  that product  liability  claims,  if made,  would not
result in a recall of the Company's  products or a change in the indications for
which  they may be used.  The  Company  maintains  product  liability  insurance
coverage for claims  arising  from the use of its  products in clinical  trials.
There can be no assurance  that this  coverage will be adequate to cover claims.
Product liability insurance is becoming increasingly expensive, and no assurance
can be given that the Company will be able to maintain  such  insurance,  obtain
additional insurance,  or obtain insurance at a reasonable cost or in sufficient
amounts to protect the Company against losses that could have a material adverse
effect on the Company.

         Control  by  Existing  Stockholders.  As of July 23,  1996,  directors,
executive  officers,  certain  stockholders  of the Company who are parties to a
stockholders  agreement  and  their  respective  affiliates  beneficially  owned
approximately  34.1% of the Company's  outstanding  Common  Stock.  Stockholders
holding  4,834,807  shares  (approximately  33.3% of the  Company's  outstanding
stock) of the Common Stock are parties to a stockholders  agreement  pursuant to
which  they have  agreed to vote  their  shares for the  election  of  directors
designated by certain groups among the parties to such  agreement.  In addition,
the Company has agreed to nominate for election only those directors  designated
by parties to that stockholders agreement. The stockholders agreement terminates
on September 11, 1997.  Accordingly,  these stockholders,  individually and as a
group,  may be able to determine the  composition  of the board of directors and
may be able to influence the outcome of other stockholder votes, including votes
concerning the adoption or amendment of provisions in the Company's  Amended and
Restated  Certificate of Incorporation (the "Certificate of Incorporation")  and
the  approval  of mergers  and other  significant  corporate  transactions.  The
existence of these levels of ownership  concentrated  in a few persons  makes it
unlikely  that any  other  holder  of Common  Stock  will be able to affect  the
management or direction of the Company.  These  factors,  along with the factors
described in "-- Anti-Takeover Provisions," may also have the effect of delaying
or preventing a change in the management or voting  control of the Company.  See
"Description of the Company's Securities -- Stockholders Agreement."

         Dependence  on Key  Personnel.  The success of the  Company  depends in
large  part on the  Company's  ability to attract  and retain  highly  qualified
scientific  and management  personnel.  The Company faces  competition  for such
personnel from other companies,  research and academic institutions,  government
entities and other  organizations.  There can be no  assurance  that the Company
will be successful in hiring or retaining key personnel.

         Shares  Eligible  for  Future  Sale;  Registration  Rights.  Sales of a
substantial number of shares of Common Stock in the public market following this
offering could  adversely  affect the market price for the Common Stock.  Of the
14,526,801  shares of Common Stock  outstanding as of July 23, 1996,  13,546,944
shares are eligible for sale without  restriction  under the  Securities  Act of
1933, as amended (the "Securities Act") (except for shares held by affiliates of
the Company and certain former  affiliates of Triplex and Oncologix whose shares
may be sold subject to the volume  limitations and certain other requirements of
Rule 144 under the Securities Act), and 979,857 shares are restricted securities
that may not be resold unless such resale is registered under the Securities Act
or it is made under Rule 144 or another  exemption from  registration  under the
Securities Act. The holders of 5,985,919  shares of Common Stock have agreed not
to sell such shares  until March 11,  1997  without the consent of the  Company,
except  under  certain  circumstances,  and the holders of  4,008,181  shares of
Common Stock  (including  3,177,471  shares that are also subject to the lock-up
agreements  that  expire on March 11,  1997) have agreed not to sell such shares
until  November  14, 1996  without the consent of  Donaldson,  Lufkin & Jenrette
Securities Corporation.  Some investors have the right to require the Company to
register the public resale of their shares. Any such sales may have an adverse
effect on the price of the Company's Common Stock and could impair the Company's
ability  to  raise  capital  through   offerings  of  equity   securities.   See
"Description of the Company's Securities -- Registration Rights."

         Immediate and Substantial Dilution; Contingent Stock Rights; Absence of
Dividends.  Purchasers  of the Common Stock in the offering  will  experience an
immediate and substantial  dilution in net tangible book value per share.
                                                   
                                      -10-

<PAGE>

These  investors will also experience  additional  dilution upon the exercise of
outstanding  options and  warrants.  In  addition,  pursuant to the terms of the
mergers in which the  Company  acquired  Triplex and  Oncologix,  the Company is
obligated to issue shares of Common Stock to certain former  securityholders  of
Triplex and Oncologix  contingent upon the occurrence of certain  events.  These
rights may result in the  issuance  of up to an  aggregate  of $10.1  million of
Common Stock,  valued for such purpose at the current market value of the Common
Stock at the time the  event  requiring  issuance  of such  shares  occurs.  See
"Dilution"  and  "Description  of the Company's  Securities -- Contingent  Stock
Rights."  The  Company  does  not  anticipate   paying  cash  dividends  in  the
foreseeable future.

         Limited  Trading  Volumes;   Possible  Stock  Price   Volatility.   The
historical trading volume of the Company's Common Stock has been limited.  There
can be no  assurance  that an active  public  market for the  Common  Stock will
develop or be sustained.  The trading price of the Common Stock and the price at
which the Company may sell  securities  in the future  could be subject to large
fluctuations in response to announcements of research activities,  technological
innovations  or new  products  by the  Company  or its  competitors,  changes in
government regulations,  developments  concerning proprietary rights,  quarterly
variations  in  operating  results,  litigation,  clinical  trials of  products,
approval or denial of NDAs,  general  market  conditions,  the  liquidity of the
Company and its ability to raise additional  funds and other events.  The market
price of the Common  Stock,  and the market  prices for  securities  of emerging
biotechnology  companies  generally,  have experienced  extreme  fluctuations in
recent years.  These fluctuations have sometimes been unrelated to the operating
performance  of the affected  companies.  These market  fluctuations  as well as
general  fluctuations  in the stock  markets  may also  affect  the price of the
Common Stock.

         Anti-Takeover  Provisions.  The Company's  Certificate of Incorporation
(i) provides for staggered terms of office for directors;  (ii) requires certain
procedures  to be followed  and time  periods to be met for any  stockholder  to
propose matters to be considered at annual meetings of  stockholders,  including
nominating   directors  for  election  at  those   meetings;   (iii)   prohibits
stockholders from calling special meetings of stockholders;  and (iv) authorizes
the  Board of  Directors  of the  Company  to issue up to  10,000,000  shares of
preferred stock without stockholder approval and to set the rights,  preferences
and other designations, including voting rights, of those shares as the Board of
Directors may determine.  These  provisions,  alone or in combination  with each
other and with the matters  described in "-- Control by Existing  Stockholders,"
may discourage  transactions involving actual or potential changes of control of
the Company,  including  transactions  that otherwise could involve payment of a
premium over  prevailing  market prices to holders of Common Stock.  The Company
also is subject to provisions of the Delaware  General  Corporation Law that may
make  some  business  combinations  more  difficult.  See  "Description  of  the
Company's  Securities -- Certain  Provisions of the Company's Charter and Bylaws
and Delaware Law."

         Forward-Looking   Statements  and  Associated  Risks.  This  Prospectus
contains   forward-looking   statements.   The  words  "anticipate,"  "believe,"
"expect," "estimate," "project" and similar expressions are intended to identify
forward-looking  statements. Such statements reflect the Company's current views
with  respect to future  events and  financial  performance  and are  subject to
certain risks,  uncertainties  and  assumptions,  including the risk factors set
forth above. Should one or more of these risks or uncertainties materialize,  or
should  underlying   assumptions  prove  incorrect,   actual  results  may  vary
materially from those anticipated, believed, expected, estimated or projected.


                                      -11-

<PAGE>



                     DESCRIPTION OF THE COMPANY'S SECURITIES

GENERAL

         The Company's  Certificate  of  Incorporation  provides for  authorized
capital stock of 85,000,000  shares,  consisting of 75,000,000  shares of common
stock, par value $0.001 per share, and 10,000,000 shares of preferred stock, par
value $0.001 per share. The following  summary  description of the capital stock
of the Company is qualified in its entirety by reference to the  Certificate  of
Incorporation,  a copy of  which  is filed  as an  exhibit  to the  Registration
Statement of which this Prospectus is a part.

COMMON STOCK

         Holders  of  Common  Stock  are  entitled  to one vote per share in the
election  of  directors  and on all  other  matters  on which  stockholders  are
entitled  or  permitted  to vote.  Holders of Common  Stock are not  entitled to
cumulative voting rights. Therefore,  holders of a majority of the shares voting
for the election of directors can elect all the directors.  Subject to the terms
of any outstanding  series of Preferred  Stock,  the holders of Common Stock are
entitled to  dividends  in such  amounts and at such times as may be declared by
the Company's Board of Directors out of funds legally  available  therefor.  See
"Dividend Policy." Upon liquidation or dissolution,  holders of Common Stock are
entitled  to share  ratably  in all net assets  available  for  distribution  to
stockholders  after  payment  of  any  liquidation  preferences  to  holders  of
Preferred  Stock.  Holders of Common  Stock have no  redemption,  conversion  or
preemptive rights.

PREFERRED STOCK

         The Board of Directors  has the authority to cause the Company to issue
up to the authorized  number of shares of Preferred Stock in one or more series,
to  designate  the  number of shares  constituting  any  series,  and to fix the
rights,  preferences,  privileges and restrictions  thereof,  including dividend
rights,  voting  rights,   redemption  and  conversion  rights  and  liquidation
preferences  of such series,  without  further action by the  stockholders.  The
issuance of  Preferred  Stock with voting and  conversion  rights may  adversely
affect the voting power of the holders of the Common  Stock.  The Company has no
present plan to issue any shares of Preferred Stock.

WARRANTS

         As of  July  23,  1996,  Aronex  had  outstanding  warrants  issued  in
connection with financing transactions to purchase an aggregate of 60,623 shares
of Common  Stock.  In  addition,  as of July 23,  1996,  Aronex had  outstanding
Warrants  issued in connection  with the September 1995 merger with Oncologix to
purchase an aggregate of  approximately  3,220,000  shares of Common Stock.  The
Oncologix   Warrants  are  not   transferable   except  under  certain   limited
circumstances.  Each Warrant  entitles the holder thereof to purchase a total of
one share of Common  Stock and is  subject  to a Series A  Exercise,  a Series B
Exercise  and a Series C  Exercise.  Subject to certain  exceptions,  holders of
Warrants  were  required to exercise the Series A Exercise,  in whole but not in
part,  prior to December 28, 1995 (January 2, 1996 after allowance of a five day
grace period).

         The holders who exercised  the Series A Exercise have the right,  prior
to June 11, 1998,  to exercise the Series B Exercise,  in whole but not in part,
at an  effective  exercise  price of $8.00 per share.  In the event the Series B
Exercise has been  exercised by a holder,  then prior to December 11, 1999,  the
Series C Exercise may be  exercised,  in whole but not in part,  at an effective
exercise  price of $12.00 per share of Common  Stock.  The  holders of  Warrants
outstanding  as of June 30,  1996 have the right to  purchase  an  aggregate  of
1,374,000 shares of Common Stock upon the Series B Exercise, and an aggregate of
1,846,000  shares of Common Stock upon the Series C Exercise  (assuming the full
exercise  of the  Series B Exercise  by the  holders  of  outstanding  Oncologix
Warrants).                               

         Aronex has the right, at its option,  to convert a Series B or Series C
Exercise into a "cashless" exercise based on the value of a Series B or Series C
Exercise  (equal to the fair market value per share of the Common Stock less the
exercise price per share) divided by the market price of the Common Stock at the
time of exercise.
                 
                                      -12-

<PAGE>

CONTINGENT STOCK RIGHTS

         In connection  with the Triplex merger,  the Company issued  contingent
rights (the "Triplex  Contingent Stock Rights") to the former holders of Triplex
stock and options  entitling them to receive  additional  shares of Common Stock
upon the  occurrence  of certain  events.  The Triplex  Contingent  Stock Rights
entitle the former  Triplex stock and option holders to receive shares of Common
Stock  with an  aggregate  fair  market  value at the time of  issuance  of $5.0
million  (subject to certain  adjustments) if the Company either (i) enters into
an agreement on or before  September  11, 1997 with respect to the  licensing of
ZintevirTM  whereby  the Company  receives  at least $5.0  million in cash or an
unconditional  binding commitment for at least $5.0 million or (ii) obtains data
from  clinical  trials of  ZintevirTM  on or before  September 11, 2000 that the
Company's  Board of Directors  determines  to be  sufficient  to file an NDA. In
addition,  the Triplex  Contingent Stock Rights entitle the former Triplex stock
and option  holders to receive  shares of Common  Stock with an  aggregate  fair
market  value at the time of  issuance of $3.0  million if the Company  does not
receive a minimum of $5.0 million in equity  milestone  payments from Genzyme on
or before September 11, 1997 with respect to the development of TretinoinLF.  In
no event, however,  shall more than 3,500,097 shares of Common Stock (subject to
adjustments in the event of stock splits, stock dividends or reclassification of
the Common Stock) be issued pursuant to the Triplex Contingent Stock Rights.

         In connection with the Oncologix merger,  the Company issued contingent
rights (the "Oncologix  Contingent Stock Rights") to certain Oncologix investors
entitling them to receive  additional shares of Common Stock upon the occurrence
of certain  events.  The Oncologix  Contingent  Stock Rights entitle such former
Oncologix  investors to receive  shares of Common Stock with a fair market value
at the time of issuance of approximately $2.1 million if the Company receives at
least $5.0 million in cash or an unconditional  binding  commitment for at least
$5.0  million on or before  September  11, 1997  relating  to certain  products,
including  AR102 and AR209.  In no event,  however,  shall  more than  2,135,000
shares of Common Stock (subject to certain  adjustments)  be issued  pursuant to
the Oncologix Contingent Stock Rights.

CERTAIN PROVISIONS OF THE COMPANY'S CHARTER AND BYLAWS AND DELAWARE LAW

         Certain  provisions of the Certificate of Incorporation  and Bylaws are
intended to enhance the  likelihood of continuity  and stability in the Board of
Directors  of the  Company  and in its  policies,  but might  have the effect of
delaying  or  preventing  a change in control of the  Company  and may make more
difficult the removal of incumbent management even if such transactions could be
beneficial  to the  interests  of  stockholders.  Set  forth  below is a summary
description of such provisions:

         Authority  to Issue  Preferred  Stock.  The  Company's  Certificate  of
Incorporation  authorizes the Board of Directors,  without stockholder approval,
to establish and to issue shares of one or more series of preferred stock,  each
such series having such voting rights, dividend rates, liquidation,  redemption,
conversion and other rights as may be fixed by the Board.

         Stockholder  Actions and  Meetings.  The  Company's  Bylaws direct that
special  meetings  of the  stockholders  may only be called by a majority of the
members of the Board of Directors,  the Chairman of the Board of Directors,  the
President of the Company or the holders of not less than 30 percent of the total
voting power of all shares of the Company's  capital  stock  entitled to vote in
the  election  of  directors.  The Bylaws  further  provide  that  stockholders'
nominations to the Board of Directors and other stockholder business proposed to
be transacted at stockholder  meetings must be timely received by the Company in
a proper  written  form which meets the  prescribed  content  requirements.  The
Certificate of  Incorporation  and Bylaws of the Company  prohibit  stockholders
from taking any action by written consent.

          Classification   of   Directors.    The   Company's   Certificate   of
Incorporation  and Bylaws  provide that the  directors  of the Company  shall be
divided  into three  classes as equal in number as possible  serving  three-year
terms.

         Limitation  of Director  Liability.  Section  102(b)(7) of the Delaware
General Corporation Law ("Section 102(b)")  authorizes  corporations to limit or
eliminate  the  personal  liability  of  directors  to  corporations  and  their
stockholders  for monetary  damages for breach of directors'  fiduciary  duty of
care.  Although  Section  102(b)  does not 

                                                   
                                      -13-

<PAGE>

change  directors'  duty of care,  it enables  corporations  to limit  available
relief to equitable  remedies such as injunction  or  rescission.  The Company's
Certificate of Incorporation limits the liability of directors to the Company or
its  stockholders  (in their  capacity as directors but not in their capacity as
officers)  to the fullest  extent  permitted  by Section  102(b).  Specifically,
directors of the Company will not be personally  liable for monetary damages for
breach of a director's fiduciary duty as a director,  except for liability:  (i)
for  any  breach  of the  director's  duty  of  loyalty  to the  Company  or its
stockholders,  (ii) for acts or  omissions  not in good  faith or which  involve
intentional  misconduct  or a  knowing  violation  of law,  (iii)  for  unlawful
payments of dividends or unlawful  stock  repurchases or redemptions as provided
in  Section  174  of the  Delaware  General  Corporation  Law or  (iv)  for  any
transaction from which the director derived an improper personal benefit.

         Indemnification.  To the maximum extent permitted by law, the Company's
Certificate of Incorporation and Bylaws provide for mandatory indemnification of
directors,  and permit indemnification of officers,  employees and agents of the
Company against all expense, liability and loss to which they may become subject
or which they may incur as a result of being or having been a director, officer,
employee or agent of the  Company.  In  addition,  the Company  must  advance or
reimburse directors, and may advance or reimburse officers, employees and agents
for expenses incurred by them in connection with indemnifiable claims.

         Section 203 of the Delaware  General  Corporation  Law ("Section  203")
generally  provides  that a  stockholder  acquiring  more than 15 percent of the
outstanding voting stock of a corporation subject to the statute (an "Interested
Stockholder")  but less than 85  percent of such stock may not engage in certain
"Business  Combinations"  with the corporation for a period of three years after
the date on which the stockholder  became an Interested  Stockholder  unless (i)
prior to such date, the  corporation's  board of directors  approved  either the
Business  Combination  or the  transaction  in which the  stockholder  became an
Interested  Stockholder,  or (ii) the  Business  Combination  is approved by the
corporation's board of directors and authorized at a stockholders'  meeting by a
vote of at least two-thirds of the  corporation's  outstanding  voting stock not
owned by the Interested Stockholder.  Under Section 203, these restrictions will
not apply to certain Business Combinations proposed by an Interested Stockholder
following  the earlier of the  announcement  or  notification  of one of certain
extraordinary transactions involving the corporation and a person who was not an
Interested  Stockholder  during  the  previous  three  years  or who  became  an
Interested   Stockholder  with  the  approval  of  the  corporation's  board  of
directors,  if such  extraordinary  transaction  is approved or not opposed by a
majority of the directors  who were  directors  prior to any person  becoming an
Interested  Stockholder  during the previous three years or were recommended for
election or elected to succeed such directors by a majority of such directors.

         Section 203 defines the term "Business Combination" to encompass a wide
variety of transactions with or caused by an Interested  Stockholder,  including
transactions  in which the  Interested  Stockholder  receives or could receive a
benefit on other than a pro rata basis with other stockholders, such as mergers,
certain asset sales,  certain  issuances of additional  shares to the Interested
Stockholder,  transactions with the corporation which increase the proportionate
interest in the  corporation  directly  or  indirectly  owned by the  Interested
Stockholder,  or  transactions  in which  the  Interested  Stockholder  receives
certain other benefits.

          The  provisions  of  Section  203,  together  with the  ability of the
Company's   Board  of  Directors  to  issue   Preferred  Stock  without  further
stockholder action,  could delay or frustrate the removal of incumbent directors
or a change in control of the Company.  The  provisions  also could  discourage,
impede or prevent a merger,  tender offer or proxy  contest,  even if such event
would be favorable to the interests of stockholders. The Company's stockholders,
by adopting an  amendment  to the  Company's  Certificate  of  Incorporation  or
Bylaws,  may elect not to be governed by Section 203  effective  12 months after
such adoption.  Neither the Company's  Certificate of  Incorporation  nor Bylaws
currently exclude the Company from the restrictions imposed by Section 203.

                                                  
                                      -14-

<PAGE>

TRANSFER AGENT

         The transfer agent and registrar for the Common Stock is American Stock
Transfer & Trust Company.

STOCKHOLDERS AGREEMENT

         The Company and certain of its  stockholders  who hold an  aggregate of
approximately  4,834,807  shares of Common Stock,  are parties to a Stockholders
Agreement  which provides that the Board of Directors of Aronex shall consist of
nine  members,  divided into three  classes  designated as Class I, Class II and
Class III. The Stockholders Agreement provides that of the nine directors, three
shall be  designated  by certain  former  Triplex  stockholders,  three shall be
designated  by certain  former Argus  stockholders,  one shall be  designated by
Genzyme, one shall be designated by certain former Oncologix  stockholders,  and
one shall be the  president  of the Company  elected by the Board of  Directors.
Such  agreement  further  provides  that the three  directors  designated by the
former  Triplex  stockholders  shall be  equally  apportioned  among  the  three
director  classes so that one of such directors shall be included in each class.
Any vacancy occurring on the board by reason of death, disability or retirement,
resignation,  removal or otherwise shall be filled by a new director  designated
by the  stockholders who are entitled to designate the director who is no longer
on the board. Of the Company's current directors,  Ronald J. Brenner and Gregory
F.  Zaic  are   designees   of  the   former   Triplex   stockholders,   Gabriel
Lopez-Berestein,  George B.  Mackaness and Martin P. Sutter are designees of the
former Argus stockholders and Geoffrey F. Cox is the designee of Genzyme;  James
M. Chubb serves as a member of the board as the Company's  President.  The Board
of Directors  currently  has two  vacancies,  one of which the former  Oncologix
stockholders are entitled to designate and the other of which the former Triplex
stockholders  are entitled to designate.  Each stockholder who is a party of the
Stockholders  Agreement  has agreed to vote all of his shares of Common Stock in
favor of the election as a director of the  individuals  designated for election
in accordance with the Stockholders Agreement.  The Stockholders Agreement shall
continue in effect until the later of (i) the  completion  of the second  annual
meeting  of  stockholders  of the  Company  after  September  11,  1995 and (ii)
September 11, 1997. See "Risk Factors -- Control by Existing Stockholders."

REGISTRATION RIGHTS

         The Company entered into registration rights agreements dated September
1, 1986 with Dr. Jim Klostergaard and Dr. Gabriel  Lopez-Berestein.  Pursuant to
such  Agreements,   Drs.   Klostergaard  and   Lopez-Berestein   have  unlimited
"piggyback" registration rights with respect to the shares of Common Stock owned
by them.  These  registration  rights  are  subject to  certain  conditions  and
limitations,  including the right of the  underwriters to restrict the number of
shares offered in a registration.

         Pursuant  to a  registration  rights  agreement  dated  August 2, 1989,
holders of  approximately  2,447,500  shares of Common  Stock and of warrants to
purchase  60,623  shares  of Common  Stock  have the right to demand up to three
registrations  of the  Registrable  Securities (as defined) under the Securities
Act and  unlimited  piggyback  registration  rights.  These demand  registration
rights are subject to certain conditions and limitations, including the right of
the underwriters to limit the number of shares offered in such  registration and
to require a lock-up of shares not included in such  registration  and the right
of the Company to refuse a registration  under certain  conditions,  such as the
six-month period immediately following effectiveness of a registration statement
and the  ninety-day  period  preceding  an  expected  filing  of a  registration
statement. If the Company proposes an offering of Registrable Securities, either
for its own  account  or for other  stockholders  exercising  such  registration
rights,  the  other  holders  of these  rights  are  entitled  to  notice of the
contemplated registration and an opportunity to include their securities in such
registration. The Company must use its best efforts to effect such registration,
with  certain  limitations.  Furthermore,  the  Company is  required  to pay the
associated registration expenses, excluding the underwriting discounts and sales
commissions, for the holders exercising such registration rights.

         In addition,  Genzyme has one demand registration right, which requires
Aronex to register all shares of Common  Stock  Genzyme  currently  holds or may
acquire in the future. Genzyme has agreed not to sell its shares of Common Stock
prior to March 11, 1997, subject to certain exceptions.
                                      
         
                                      -15-

<PAGE>

         In connection with the Triplex  merger,  the Company granted the former
stockholders of Triplex unlimited  piggyback  registration  rights which provide
that, if Aronex proposes an offering of Common Stock, either for its own account
or for other  stockholders  exercising  registration  rights, the holders of the
rights  are  entitled  to  notice  of  the  contemplated   registration  and  an
opportunity to include their Aronex Common Stock in such  registration,  subject
to certain limitations. These registration rights have been or will be waived in
connection with this offering.

         The  Company  has agreed to  register  the resale of 570,274  shares of
Common  Stock by certain  stockholders,  pursuant  to a  registration  statement
required to be effective no later than March 11, 1997.

                              PLAN OF DISTRIBUTION

         The  Shares  offered  hereby  are  issuable  upon the  exercise  of the
Warrants and the payment of the exercise price for the Series B Exercise and the
Series C Exercise, respectively. The exercise price of the Series B Exercise and
the Series C Exercise  and the number of Shares  issuable  upon the  exercise of
each  Warrant are subject to  adjustment,  as  provided  in the  Warrants,  upon
certain events.

         In accordance with the provisions of the Warrants, upon the delivery of
a  written  notice  in the  form of the  subscription  notice  set  forth in the
Warrants  (and,  upon  exercise of the Series C Exercise,  the  surrender of the
Warrant),  duly  executed,  along with payment in full of the exercise price for
the Series B Exercise or Series C  Exercise,  as the case may be, to the warrant
agent or its  successor at its  principal  office in New York City,  Aronex will
issue the applicable  number of shares of Common Stock,  registered in such name
or names as may be directed by him, to the registered  holder of such Warrant or
Warrants.

                                 USE OF PROCEEDS

         The  Company  intends to use the  proceeds  from the sale of the shares
upon exercise of the Warrants for general corporate  purposes,  depending on the
Company's  needs  as  determined  from  time to time by the  Company's  Board of
Directors.

                                    DILUTION

         The net  tangible  book value of the Common  Stock of the Company as of
June 30, 1996 was approximately $43.4 million, or approximately $2.99 per share.
Net tangible book value per share of Common Stock  represents the total tangible
assets of the Company reduced by its total liabilities and divided by the number
of  shares  of  Common  Stock  outstanding.  If  the  holders  of  all  Warrants
outstanding as of June 30, 1996 had exercised the Series B Exercise and Series C
Exercise  as of such date at the Series B Exercise  price of $8.00 per share and
the Series C Exercise  price of $12.00 per  share,  the  adjusted  pro forma net
tangible book value of the Common Stock of the Company as of June 30, 1996 would
have been  approximately  $76.6 million or  approximately  $4.32 per share.  The
increase  in net  tangible  book value of $1.33 per share would be due solely to
the purchase of the Shares.  Holders of Warrants would have immediately incurred
a  dilution  of $3.68 per share and  $7.68 per share  upon the  exercise  of the
Series  B  Exercise  and the  Series C  Exercise,  respectively.  "Dilution"  is
determined by subtracting  pro forma net tangible book value per share after the
exercise of the Series B Exercise and the Series C Exercise of all Warrants from
the exercise price of the Series B Exercise and Series C Exercise, respectively.

                                  LEGAL MATTERS

          Andrews & Kurth L.L.P.  has passed upon certain matters as counsel for
the Company.
                                                  
                                      -16-

<PAGE>

                             

                                     EXPERTS

         The financial statements incorporated by reference in this Registration
Statement  have  been  audited  by  Arthur  Andersen  LLP,   independent  public
accountants,  as  indicated  in  their  report  with  respect  thereto,  and are
incorporated by reference  herein in reliance upon the authority of said firm as
experts in giving said report.


                                                  
                                      -17-

<PAGE>



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


No  dealer,  salesperson  or  other  person  has  been  authorized  to give  any
information  or to make any  representations  other than those  contained  in or
incorporated  by reference in this  Prospectus in connection with the offer made
by this Prospectus and, if given or made,  such  information or  representations
must not be relied upon as having been authorized.  Neither the delivery of this
Prospectus nor any sale made hereunder shall,  under any  circumstances,  create
any  implication  that there has been no change in the  affairs  of the  Company
since  the  date  hereof.  This  Prospectus  does  not  constitute  an  offer or
solicitation  by anyone in any  jurisdiction in which such offer or solicitation
is not  authorized  or in which the person making such offer is not qualified to
do so or to any person to whom it is unlawful to make such solicitation.




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




                                TABLE OF CONTENTS

                                                                         Page

Available Information........................     2
Documents Incorporated by Reference..........     2
The Company..................................     4
Risk Factors.................................     5
Description of the Company's
Securities...................................    12
Plan of Distribution.........................    16
Use of Proceeds..............................    16
Dilution.....................................    16
Legal Matters................................    17
Experts......................................    17



                      [Aronex Pharmaceuticals, Inc. Logo]


                              3,220,000 SHARES OF
                                  COMMON STOCK
                       ISSUABLE UPON EXERCISE OF WARRANTS



                                   ----------
                                   PROSPECTUS
                                   ----------



                              Dated July 29, 1996



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


                                                   
                                      -18-

<PAGE>



                                     PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14.          Other Expenses of Issuance and Distribution

         Set forth below are the expenses  expected to be incurred in connection
with the issuance and distribution of the securities registered hereby. With the
exception  of the  Securities  and  Exchange  Commission  registration  fee, the
amounts  set forth  below are  estimates  and  consist  exclusively  of expenses
incurred in connection with this amendment on Form S-3:


Securities and Exchange Commission registration fee............ $      --  (1)
Printing and engraving expenses................................     1,000
Legal fees and expenses........................................     5,000
Accounting fees and expenses...................................     5,000
Blue Sky fees and expenses.....................................        --
Miscellaneous expenses.........................................     1,000
                                                                ---------
         Total................................................. $  12,000

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

(1)  Previously paid in connection with the filing of the Company's Registration
     Statement on Form S-4 to which this post- effective amendment relates.

Item 15.          Indemnification of Directors and Officers

         Section 145 of the Delaware  General  Corporation  Law ("DGCL"),  inter
alia,  empowers a Delaware  corporation  to indemnify any person who was or is a
party  or is  threatened  to be  made a  party  to any  threatened,  pending  or
completed action, suit or proceeding (other than an action by or in the right of
the  corporation)  by reason of the fact that such  person is or was a director,
officer,  employee  or agent of the  corporation,  or is or was  serving  at the
request of the corporation as a director,  officer, employee or agent of another
corporation or other enterprise,  against expenses (including  attorneys' fees),
judgments, fines and amounts paid in settlement actually and reasonably incurred
by him in  connection  with such action,  suit or proceeding if he acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests  of the  corporation,  and,  with  respect to any  criminal  action or
proceeding, had no reasonable cause to believe his conduct was unlawful. Similar
indemnity is authorized for such persons against expenses (including  attorneys'
fees)  actually  and  reasonably  incurred  in  connection  with the  defense or
settlement of any such  threatened,  pending or completed action or suit if such
person  acted in good faith and in a manner he  reasonably  believed to be in or
not opposed to the best interests of the corporation,  and provided further that
(unless a court of competent  jurisdiction otherwise provides) such person shall
not have been adjudged liable to the corporation.  Any such  indemnification may
be made only as authorized in each  specific  case upon a  determination  by the
stockholders  or  disinterested  directors or by independent  legal counsel in a
written  opinion that  indemnification  is proper because the indemnitee has met
the applicable standard of conduct.

         Section 145 further  authorizes a corporation  to purchase and maintain
insurance on behalf of any person who is or was a director, officer, employee or
agent of the corporation, or is or was serving at the request of the corporation
as a director,  officer, employee or agent of another corporation or enterprise,
against  any  liability  asserted  against  him and  incurred by him in any such
capacity,  or arising out of his status as such,  whether or not the corporation
would  otherwise  have the power to indemnify him under Section 145. The Company
maintains  policies  insuring its and its  subsidiaries'  officers and directors
against  certain  liabilities  for actions taken in such  capacities,  including
liabilities under the Securities Act of 1933, as amended (the "Securities Act").

         Article VIII of the Amended and Restated  Certificate of  Incorporation
of the  Company  and  Article  VII of the  Bylaws  of the  Company  provide  for
indemnification  of the directors of the Company to the full extent permitted by
law, as now in effect or later  amended.  Article VII of the Bylaws also permits
the  indemnification to the same extent of officers, 


                                      II-1

<PAGE> 
    
employees  or agents of the  Company if, and to the  extent,  authorized  by the
Board of Directors.  In addition, the Bylaws provide for indemnification against
expenses  incurred  by a  director  to be  paid  by the  Company  at  reasonable
intervals in advance of the final disposition of such action, suit or proceeding
upon  receipt of an  undertaking  by or on behalf of the  director or officer to
repay such amount if it shall be ultimately  determined  that he is not entitled
to be indemnified by the Company.  The Bylaws further  provide for a contractual
cause of action on the part of  directors  of the  Company  for  indemnification
claims that have not been paid by the Company.
                                                     
          The Company also has provided  liability  insurance  for each director
and officer for certain  losses arising from claims or charges made against them
while acting in their capacities as directors or officers of the Company.
                                                     
          Article VII of the  Company's  Amended  and  Restated  Certificate  of
Incorporation,  as amended,  limits under certain circumstances the liability of
the Company's directors for a breach of their fiduciary duty as directors. These
provisions  do not eliminate the liability of a director (i) for a breach of the
director's duty of loyalty to the Company or its stockholders,  (ii) for acts or
omissions not in good faith or that involve intentional  misconduct or a knowing
violation  of  law,  (iii)  under  Section  174 of  the  DGCL  (relating  to the
declaration  of dividends  and purchase or  redemption of shares in violation of
the  DGCL) or (iv) for any  transaction  from  which  the  director  derived  an
improper personal benefit.

<TABLE>
<CAPTION>

Item 16.          Exhibits
<S>     <C>    

         4.1 Form of Common  Stock  Certificate  (incorporated  by  reference to
             Exhibit 4.1 to the Company's  Quarterly Report on Form 10-Q for the
             quarterly period ended June 30, 1996).
        *4.2 Form of Warrant Certificate
        *5.1 Opinion of Porter & Hedges
        *8.1 Opinion of Porter & Hedges
        23.1 Consent of Arthur Andersen LLP
       *23.2 Consent of Porter & Hedges
        25.1 Powers of Attorney, included in Part II of this Post-Effective Amendment No. 1 to the Registration
             Statement
<FN>

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

* Previously filed
</FN>
</TABLE>

                                                   
                                      II-2

<PAGE>



Item 17.          Undertakings

                  (1)      The undersigned registrant hereby undertakes:

                  (a) To file,  during any  period in which  offers or sales are
         being made, a post-effective amendment to this registration statement:

                    (i)  To include any prospectus  required by Section 10(a)(3)
                         of  the   Securities  Act  of  1933,  as  amended  (the
                         "Securities Act");

                    (ii) To  reflect  in the  prospectus  any  facts  or  events
                         arising  after the effective  date of the  Registration
                         Statement (or the most recent post-effective  amendment
                         thereof)  which,  individually  or  in  the  aggregate,
                         represent a fundamental  change in the  information set
                         forth in the  Registration  Statement.  Notwithstanding
                         the  foregoing,  any  increase or decrease in volume of
                         securities  offered  (if  the  total  dollar  value  of
                         securities  offered  would not  exceed  that  which was
                         registered)  and any deviation from the low or high end
                         of  the  estimated   maximum   offering  range  may  be
                         reflected  in the  form of  prospectus  filed  with the
                         Commission  pursuant to Rule 424(b) (ss.  230.424(b) of
                         this  chapter)  if, in the  aggregate,  the  changes in
                         volume and price represent no more than a 20% change in
                         the maximum  aggregate  offering price set forth in the
                         "Calculation   of   Registration   Fee"  table  in  the
                         effective registration statement;

                    (iii)To include any  material  information  with  respect to
                         the plan of  distribution  not previously  disclosed in
                         this  Registration  Statement or any material change to
                         such information in the Registration Statement.

                  (b) That, for the purpose of determining  any liability  under
         the Securities Act of 1933, each such post-effective amendment shall be
         deemed to be a new  registration  statement  relating to the securities
         offered therein, and the offering of such securities at that time shall
         be deemed to be the initial bona fide offering thereof.

                  (c) To remove from  registration by means of a  post-effective
         amendment any of the securities being registered which remain unsold at
         the termination of the offering.

                  (2) The undersigned  registrant  hereby  undertakes  that, for
purposes of determining  any liability  under the  Securities Act of 1933,  each
filing of the  registrant's  annual report  pursuant to section 13(a) or section
15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing
of an employee  benefit  plan's annual  report  pursuant to section 15(d) of the
Securities  Exchange  Act of 1934)  that is  incorporated  by  reference  in the
registration  statement  shall  be  deemed  to be a new  registration  statement
relating to the securities offered therein,  and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

                  (3) Insofar as indemnification  for liabilities  arising under
the  Securities  Act of  1933  may  be  permitted  to  directors,  officers  and
controlling persons of the registrant pursuant to the foregoing  provisions,  or
otherwise, the registrant has been advised that in the opinion of the Securities
and  Exchange  Commission  such  indemnification  is  against  public  policy as
expressed in the Act and is, therefore, unenforceable. In the event that a claim
for  indemnification  against  such  liabilities  (other than the payment by the
registrant  of expenses  incurred by paid by a director  officer or  controlling
person in the successful defense of any action,  suit or proceeding) is asserted
by  such  director,  officer  or  controlling  person  in  connection  with  the
securities being  registered,  the registrant will, unless in the opinion of its
counsel the matter has been settled by controlling precedent,  submit to a court
of appropriate  jurisdiction  the question whether such  indemnification  by its
against  public policy as expressed in the Act and will be governed by the final
adjudication of such issue.


                                                   
                                      II-3

<PAGE>



                                   SIGNATURES

         Pursuant to the  requirements  of the Securities  Exchange Act of 1933,
the Registrant certifies that is has reasonable grounds to believe that it meets
all of the  requirements  for  filing  on  Form  S-3 and has  duly  caused  this
Registration Statement to be signed on its behalf by the undersigned,  thereunto
duly authorized, in the City of The Woodlands, State of Texas on the 29th day of
July, 1996.

                                    ARONEX PHARMACEUTICALS, INC.


                                    By:      /s/ James M. Chubb
                                        ---------------------------
                                             James M. Chubb
                                             President

         KNOW ALL MEN BY THESE PRESENTS,  that each of the undersigned  officers
and directors of Aronex Pharmaceuticals, Inc. (the "Company") hereby constitutes
and appoints James M. Chubb and Terance A. Murnane, or either of them (with full
power to each of them to act alone),  his true and lawful  attorney-in-fact  and
agent,  with full power of substitution and  resubstitution,  for him and on his
behalf and in his name,  place and stead,  in any and all  capacities,  to sign,
execute and file this  Registration  Statement under the Securities Act of 1933,
as  amended,  and  any  or  all  amendments   (including,   without  limitation,
post-effective amendments), with all exhibits and any and all documents required
to be filed with respect thereto, with the Securities and Exchange Commission or
any regulatory authority,  granting unto such  attorneys-in-fact and agents, and
each of them acting  alone,  full power and authority to do and perform each and
every act and thing requisite and necessary to be done in and about the premises
in order to  effectuate  the same,  as fully to all intents  and  purposes as he
himself might or could do if personally present, hereby ratifying and confirming
all that such  attorneys-in-fact and agents, or any of them, or their substitute
or substitutes, may lawfully do or cause to be done.

         PURSUANT  TO THE  REQUIREMENTS  OF THE  SECURITIES  ACT OF  1933,  THIS
REGISTRATION  STATEMENT  HAS  BEEN  SIGNED  BY  THE  FOLLOWING  PERSONS  IN  THE
CAPACITIES AND ON THE DATES INDICATED.
<TABLE>
<CAPTION>

SIGNATURE                                   TITLE                                                    DATE
<S>                                         <C>                                                       <C>
/s/ James M. Chubb                          President                                                 July 29, 1996
- ----------------------------------------
James M. Chubb                              (Principal Executive Officer)

/s/ Terance A. Murnane                      Controller                                                July 29, 1996
- ----------------------------------------
Terance A. Murnane                          (Principal Financial and Accounting Officer)

/s/ Martin P. Sutter                        Chairman of the Board of Directors                        July 29, 1996
- ----------------------------------------
Martin P. Sutter

/s/ Gabriel Lopez-Berestein  
- ----------------------------------------    Director                                                  July 29, 1996
Gabriel Lopez-Berestein

/s/ Ronald J. Brenner                       Director                                                  July 29, 1996
- ----------------------------------------
Ronald J. Brenner

/s/ Geoffrey F. Cox                         Director                                                  July 29, 1996
- ----------------------------------------
Geoffrey F. Cox

/s/ George B. Mackaness                     Director                                                  July 29, 1996
- ----------------------------------------
George B. Mackaness

/s/ Gregory F. Zaic                         Director                                                  July 29, 1996
- ----------------------------------------
Gregory F. Zaic
</TABLE>

                                      II-4

<PAGE>



                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>

                                                                                                      Sequentially
   Exhibit                                                                                              Numbered
   Number                                         Description                                             Page
   ------                                         -----------                                          ----------
<S>       <C>                                                                                         <C>    

           4.1Form of Common Stock Certificate (incorporated by reference to Exhibit 4.1 to
                       the Company's Quarterly Report on Form 10-Q for the quarterly period ended
                       June 30, 1996)............................................................
          *4.2Form of Warrant Certificate........................................................
          *5.1Opinion of Porter & Hedges.........................................................
          *8.1Opinion of Porter & Hedges.........................................................
          23.1Consent of Arthur Andersen LLP.....................................................
         *23.2Consent of Porter & Hedges.........................................................
          25.1Powers of Attorney, included in Part II of this Post-Effective Amendment No. 1
                       to the Registration Statement.............................................
<FN>

- ---------------------
*Previously filed.
</FN>
</TABLE>


<PAGE>



                                                              EXHIBIT 23.1


                    CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS


     As independent public  accountants,  we hereby consent to the incorporation
by  reference  in  this  Post-Effective  Amendment  No.  1 to  the  Registration
Statement on Form S-4 on Form S-3 of Aronex Pharmaceuticals,  Inc. of our report
dated March 7, 1996 included in Aronex  Pharmaceuticals,  Inc.'s Form 10-K/A for
the year ended  December 31, 1995 and to all  references to our Firm included in
this Registration Statement.


/s/ ARTHUR ANDERSEN LLP

ARTHUR ANDERSEN LLP



The Woodlands, Texas
July 29, 1996


                                                  


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