-------------------------------
                                   ENZON, INC.

                         COMMON STOCK PURCHASE AGREEMENT

                                  June 25, 1998
                          -------------------------------










                                TABLE OF CONTENTS

                                                                            Page
                                                                            ----
Section 1

           Authorization and Sale of Common Stock .........................    1
  1.1  Authorization ......................................................    1
  1.2  Sale of Common .....................................................    1

Section 2

           Closing Date: Delivery .........................................    1
  2.1  Closing Date .......................................................    1
  2.2  Delivery ...........................................................    1

Section 3

           Representations and Warranties of the Company ..................    2
  3.1  Organization and Standing ..........................................    2
  3.2  Corporate Power, Authorization .....................................    2
  3.3  Issuance and Delivery of the Shares ................................    2
  3.4  Private Placement Offering Memorandum: SEC Documents, Financial
       Statements .........................................................    2
  3.5  Governmental Consents ..............................................    3
  3.6  No Material Adverse Change .........................................    3
  3.7  Intellectual Property ..............................................    3
  3.8  Authorized Capital Stock ...........................................    4
  3.9  Litigation .........................................................    4
  3.10 Use of Proceeds ....................................................    4
  3.11 Accountants ........................................................    4
  3.12 Compliance With Other Instruments ..................................    5
  3.13 Permits ............................................................    5
  3.14 Investment Company .................................................    5
  3.15 Offering Materials .................................................    5

Section 4

           Representations, Warranties and Covenants of the Purchasers ....    5
  4.1  Power; Authorization ...............................................    5
  4.2  Investment Experience ..............................................    6
  4.3  Investment Intent ..................................................    6
  4.4  Registration or Exemption Requirements .............................    6



                                      E-1



                                TABLE OF CONTENTS
                                   (continued)


Section 5

           Conditions to Closing of Purchasers ............................    6
  5.1  Representations and Warranties .....................................    7
  5.2  Covenants ..........................................................    7
  5.3  Blue Sky ...........................................................    7
  5.4  Legal Opinion ......................................................    7
  5.5  Patent Opinion .....................................................    7
  5.6  Registration Statement .............................................    7
  5.7  Nasdaq Qualification ...............................................    7

Section 6

           Conditions to Closing of Company ...............................    7
  6.1  Representations and Warranties .....................................    8
  6.2  Covenants ..........................................................    8
  6.3  Blue Sky ...........................................................    8
  6.4  Registration Statement .............................................    8
  6.5  Nasdaq Qualification ...............................................    8

Section 7

           Affirmative Covenants of the Company ...........................    8
  7.1  Financial Information ..............................................    8
  7.2  Registration Requirements ..........................................    8
  7.3  Indemnification and Contribution ...................................   10

Section 8

           Restrictions on Transferability of Shares:
           Compliance with Securities Act .................................   12
  8.1  Restrictions on Transferability ....................................   13
  8.2  Restrictive Legend .................................................   13
  8.3  Transfer of Shares After Registration ..............................   13
  8.4  Purchaser Information ..............................................   13

Section 9

           Miscellaneous ..................................................   14
  9.1  Waivers and Amendments .............................................   14


                                      E-2



                                TABLE OF CONTENTS
                                   (continued)


  9.2  Placement Agent Fee ................................................  14
  9.3  Governing Law ......................................................  14
  9.4  Survival ...........................................................  14
  9.5  Successors and Assigns .............................................  14
  9.6  Entire Agreement ...................................................  14
  9.7  Notices, etc .......................................................  14
  9.8  Severability of this Agreement .....................................  15
  9.9  Counterparts .......................................................  15
  9.10 Further Assurances .................................................  15
  9.11 Termination ........................................................  15
  9.12 Expenses ...........................................................  15
  9.13 Currency ...........................................................  15
                                                                      
Exhibit A - Schedule of Purchasers
Exhibit B - Form of Purchaser's Questionnaire
Exhibit C - Opinion of Company  Counsel 
Exhibit D - Opinions of Patent  Counsel
Exhibit E - Form of Purchaser's Legend Removal Certificate
Exhibit F - Form of Purchaser's Certificate of Subsequent Sale
Exhibit G - Description of Capital Stock









                                      E-3


                                   ENZON, INC.


                         COMMON STOCK PURCHASE AGREEMENT

     This Common Stock Purchase  Agreement (the  "Agreement") is made as of June
25, 1998, by and among Enzon, Inc., a Delaware corporation (the "Company"), with
its principal office at 20 Kingsbridge  Road,  Piscataway,  New Jersey,  and the
persons  listed on the Schedule of Investors  attached  hereto as Exhibit A (the
"Purchasers").

                                    Section 1

                     Authorization and Sale of Common Stock

     1.1  Authorization.  The Company has  authorized  the sale and  issuance of
3,985,000  shares of its Common  Stock,  $0.01 par value per share (the  "Common
Stock") pursuant to this Agreement (the "Shares").

     1.2 Sale of Common.  Subject to the terms and conditions of this Agreement,
the  Company  agrees  to issue  and sell to each  Purchaser  and each  Purchaser
severally  agrees to  purchase  from the  Company the number of Shares set forth
opposite such Purchaser's name on Exhibit A for $4.75 per share.

                                    Section 2

                             Closing Date: Delivery

     2.1  Closing  Date.  The  closing  of the  purchase  and sale of the Shares
hereunder (the "Closing")  shall be held at the offices of Dorsey & Whitney LLP,
250 Park Avenue,  New York, NY 10177,  at or before 10:00 a.m. New York Time, on
that date that is two  business  days  after the date on which the  Registration
Statement  (as defined  herein) is declared  effective or at such time and place
upon which the Company and SBC Warburg Dillon Read Inc. (the "Placement  Agent")
shall agree. The date of the Closing is hereinafter  referred to as the "Closing
Date."

     2.2 Delivery.  At the Closing, the Company will deliver to each Purchaser a
certificate,  registered  in  the  Purchaser's  name  as  shown  on  Exhibit  A,
representing  the  number of  Shares  to be  purchased  by the  Purchaser.  Such
delivery  shall be  against  payment  of the  purchase  price  therefor  by wire
transfer to the Company's bank account in the amount set forth on Exhibit A.





                                      E-4




                                    Section 3

                  Representations and Warranties of the Company

     The Company  represents  and warrants to the  Purchasers  as of the Closing
Date as follows:

     3.1 Organization and Standing.  The Company is a corporation duly organized
and validly  existing under, and by virtue of, the laws of the State of Delaware
and is in good standing as a domestic  corporation  under the laws of said state
and has all requisite  corporate  power and authority to conduct its business as
currently conducted and disclosed in the Offering Memorandum (as defined below).

     3.2 Corporate Power, Authorization. The Company has all requisite legal and
corporate  power and has taken all  requisite  corporate  action to execute  and
deliver  this  Agreement,  to sell and  issue  the  Shares  and to carry out and
perform all of its obligations under this Agreement.  This Agreement constitutes
the  legal,  valid  and  binding  obligation  of  the  Company,  enforceable  in
accordance  with its terms,  except (i) as  limited  by  applicable  bankruptcy,
insolvency,  reorganization  or  similar  laws  relating  to  or  affecting  the
enforcement  of  creditors'  rights  generally  and (ii) as limited by equitable
principles generally. The execution and delivery of this Agreement does not, and
the performance of this Agreement and the compliance with the provisions  hereof
and the  issuance,  sale and  delivery  of the Shares by the  Company  will not,
conflict  with or result in a breach or  violation of the terms,  conditions  or
provisions  of, or  constitute  a default  under,  or result in the  creation or
imposition  of  any  lien  pursuant  to  the  terms  of,  the   Certificate   of
Incorporation  or Bylaws of the Company or any statute,  law, rule or regulation
or any state or federal order,  judgment or decree or any  indenture,  mortgage,
lease or other  agreement  or  instrument  to which  the  Company  or any of its
properties is subject.

     3.3  Issuance  and  Delivery  of the  Shares.  The  Shares,  when issued in
compliance with the provisions of this Agreement,  will be validly issued, fully
paid and  nonassessable.  The issuance and delivery of the Shares is not subject
to preemptive or any other similar rights of the  stockholders of the Company or
any liens or encumbrances.

     3.4  Private  Placement  Offering  Memorandum:  SEC  Documents,   Financial
Statements.  Each  complete or partial  statement,  report,  or proxy  statement
included within the Company's Private Placement  Offering  Memorandum dated June
4, 1998 (the  "Offering  Memorandum")  is a true and complete copy of or excerpt
from such  document as filed by the Company  with the  Securities  and  Exchange
Commission  (the "SEC").  The Company has filed in a timely manner all documents
that the Company was required to file with the SEC under  Sections 13, 14(a) and
15(d) of the Securities  Exchange Act of 1934, as amended (the "Exchange  Act"),
during the twelve (12) months preceding the date of this Agreement.  As of their
respective  filing dates,  all documents  filed by the Company with the SEC (the
"SEC Documents")  complied in all material respects with the requirements of the
Exchange Act or the



                                      E-5




Securities  Act of 1933,  as amended  (the  "Securities  Act"),  as  applicable.
Neither  the  Offering  Memorandum  nor any of the  SEC  Documents  as of  their
respective  dates contained any untrue  statement of material fact or omitted to
state a material  fact  required to be stated  therein or  necessary to make the
statements  made therein,  in light of the  circumstances  under which they were
made,  not  misleading.  As of their  respective  filing  dates,  the  financial
statements  of  the  Company  included  in the  SEC  Documents  (the  "Financial
Statements")  complied  as to  form in all  material  respects  with  applicable
accounting  requirements and with the published rules and regulations of the SEC
with respect thereto.  The Financial Statements have been prepared in accordance
with generally accepted accounting  principles  consistently  applied and fairly
present the consolidated  financial position of the Company and any subsidiaries
at the dates  thereof  and the  consolidated  results  of their  operations  and
consolidated cash flows for the periods then ended; provided,  however, that the
unaudited  Financial   Statements  are  subject  to  normal  recurring  year-end
adjustments  (which in any case will not be  material)  and do not  contain  all
footnotes required under generally accepted accounting principles.

     3.5 Governmental Consents. No consent, approval, order or authorization of,
or  registration,  qualification,  designation,  declaration or filing with, any
federal,  state, or local  governmental  authority on the part of the Company is
required in connection with the consummation of the transactions contemplated by
this Agreement  except for (a) compliance  with the securities and blue sky laws
in the states in which  Shares are offered  and/or  sold,  (b) the filing of the
Registration  Statement and all amendments  thereto with the SEC as contemplated
by Section 7.2 of this  Agreement  and (c) all required  filings with The Nasdaq
Stock Market necessary for the listing of the Shares.

     3.6 No  Material  Adverse  Change.  Except as  otherwise  disclosed  in the
Offering  Memorandum,  since March 31, 1998,  there have not been any changes in
the assets,  liabilities,  financial condition or operations of the Company from
those  reflected in the  Financial  Statements,  except  changes in the ordinary
course of business which have not been, either individually or in the aggregate,
materially adverse.

     3.7 Intellectual Property.  Except as disclosed in the Offering Memorandum,
the Company owns or  possesses  sufficient  rights to use all existing  patents,
patent rights,  inventions,  trade  secrets,  know-how,  proprietary  rights and
processes  that are  necessary  for the  conduct  and  proposed  conduct  of its
business as described in the Offering  Memorandum  (the  "Company's  Proprietary
Rights") without any conflict with or infringement of the rights of others which
would  result in a  material  adverse  effect  on the  condition  (financial  or
otherwise), earnings, operations, business or business prospects of the Company.
The Company believes that there are no third parties who have or will be able to
establish rights to any of the Company's  Proprietary Rights, except for (i) the
ownership  rights of the third  party  licensors  to the  Company's  Proprietary
Rights which are licensed to the Company by such third party  licensors and (ii)
the  third  party  licensees  of the  Company's  Proprietary  Rights.  Except as
disclosed in the Offering Memorandum,  to the knowledge of the Company, there is
no infringement by any third parties of any of the Company's Proprietary Rights.
Except as disclosed in the Offering Memorandum, the Company has not received any
notice of, and has



                                      E-6




no knowledge of any basis for, any  infringement  of or conflict  with  asserted
rights of others with  respect to any patent,  patent  right,  invention,  trade
secret,  know-how  or other  proprietary  rights  that,  individually  or in the
aggregate,  would have a material adverse effect on the condition  (financial or
otherwise), earnings, operations, business or business prospects of the Company.

     3.8 Authorized  Capital Stock.  All outstanding  shares of capital stock of
the Company have been duly  authorized and validly issued and are fully paid and
nonassessable,  have  been  issued  in  compliance  with all  federal  and state
securities  laws,  were not issued in violation of or subject to any  preemptive
rights  or  other  rights  to  subscribe  for or  purchase  securities,  and the
authorized  and  outstanding  capital stock of the Company  conforms,  as of the
dates for which such  information  is given,  in all  material  respects  to the
statements  relating thereto contained in Exhibit G hereto;  there is no capital
stock  outstanding as of such dates other than as described in Exhibit G hereto;
and all issued and outstanding  shares of capital stock of the Company have been
duly authorized and validly issued and are fully paid and nonassessable.  Except
as disclosed in or  contemplated  by the Offering  Memorandum  and the Financial
Statements and the related notes thereto included in the Offering  Memorandum or
in  Exhibit G hereto,  the  Company  does not have  outstanding  any  options to
purchase,  or any  preemptive  rights  or other  rights to  subscribe  for or to
purchase,  any securities or obligations  convertible  into, or any contracts or
commitments  to issue or sell,  shares of its capital stock or any such options,
rights, convertible securities or obligations.  Except as described in Exhibit G
hereto, no stockholder of the Company, other than the Purchasers,  has any right
(which  has not  been  waived  or has not  expired  by  reason  of lapse of time
following  notification  of  the  Company's  intent  to  file  the  Registration
Statement)  to require the Company to register  the sale of any shares  owned by
such stockholder under the Securities Act in the Registration Statement.

     3.9 Litigation.  Except as set forth in the Offering Memorandum,  there are
no actions, suits,  proceedings or investigations pending or, to the best of the
Company's  knowledge,  threatened  against the Company or any of its  properties
before  or by any  court or  arbitrator  or any  governmental  body,  agency  or
official in which there is the possibility of an adverse decision that (a) would
reasonably  be  expected  to have a  material  adverse  effect on the  Company's
properties  or assets or the business of the Company as  presently  conducted or
proposed  to be  conducted  or (b) would  reasonably  be  expected to impair the
ability of the Company to perform its obligations under this Agreement.

     3.10 Use of Proceeds. The Company will apply the net proceeds from the sale
of the Shares in the manner set forth under the caption "Use of Proceeds" in the
Offering Memorandum.

     3.11  Accountants.  KPMG Peat Marwick LLP, who have expressed their opinion
with respect to the audited financial  statements and schedules to be filed with
the SEC as a part of the Registration Statement and included in the Registration
Statement  and the  Prospectus  which  forms  a part  thereof,  are  independent
accountants  as required  by the  Securities  Act and the rules and  regulations
promulgated thereunder (the "Rules and Regulations").




                                      E-7




     3.12 Compliance With Other Instruments.  Except as to defaults,  violations
and breaches which individually or in the aggregate would not be material to the
Company,  the Company is not in  violation  or default of any  provision  of its
Articles  of  Incorporation  or  Bylaws,  each as  amended  to  date,  or of any
agreement, license, permit, instrument, judgment, order, writ or decree to which
it is a party or by which it is bound, or, to the best of its knowledge,  of any
provision of any federal or state statute,  rule or regulation applicable to the
Company.

     3.13 Permits. The Company has all franchises,  permits,  licenses,  and any
similar  authority  necessary  for the  conduct  of its  business  as now  being
conducted by it, the lack of which could  materially  and  adversely  affect the
business,  properties,  prospects,  or financial  condition of the Company.  The
Company is not in default in any material  respect under any of such franchises,
permits, licenses, or other similar authority.

     3.14 Investment Company.  The Company is not an "investment company" within
the meaning of the Investment Company Act of 1940, as amended.

     3.15  Offering  Materials.  The  Company has not  distributed  and will not
distribute  prior to the Closing Date any offering  material in connection  with
the offering and sale of the Shares other than the Offering Memorandum.

                                    Section 4

           Representations, Warranties and Covenants of the Purchasers

     Each  Purchaser  hereby  severally  represents and warrants to the Company,
effective as of the Closing Date, as follows:

     4.1 Power;  Authorization.  (i) Such Purchaser has all requisite  legal and
corporate or other power and capacity and has taken all  requisite  corporate or
other action to execute and deliver this Agreement, to purchase the Shares to be
purchased by it and to carry out and perform all of its  obligations  under this
Agreement;  and (ii) this  Agreement  constitutes  the legal,  valid and binding
obligation of such Purchaser,  enforceable in accordance with its terms,  except
(a) as limited by applicable bankruptcy, insolvency,  reorganization, or similar
laws relating to or affecting the enforcement of creditors' rights generally and
(b) as limited by equitable principles generally.

     4.2 Investment  Experience.  Such Purchaser is an "accredited  investor" as
defined in Rule 501(a) under the Securities Act. Such Purchaser has received and
reviewed the Offering Memorandum, is aware of the Company's business affairs and
financial   condition  and  has  had  access  to  and  has  acquired  sufficient
information about the Company to reach an informed and knowledgeable decision to
acquire the Shares.  Purchaser has such business and financial  experience as is
required  to permit it to  protect  its own  interests  in  connection  with the
purchase of the Shares.



                                      E-8





     4.3  Investment  Intent.  Such  Purchaser is  purchasing  the Shares in the
ordinary course of its business for its own account as principal, for investment
purposes only,  and not with a present view to, or for, the resale  distribution
thereof,  in whole or in part,  within the meaning of the  Securities Act or any
state securities laws. Purchaser  understands that its acquisition of the Shares
has not been  registered  under the  Securities  Act or  registered or qualified
under  any  state  law in  reliance  on  specific  exemptions  therefrom,  which
exemptions  may depend upon,  among other  things,  the bona fide nature of such
Purchaser's  investment intent as expressed herein. Such Purchaser has completed
or caused to be completed the Purchaser Questionnaire attached hereto as Exhibit
B for use in preparation of the Registration  Statement (as defined below),  and
the  responses  provided  therein  shall be true and correct as of the effective
date of the Registration Statement and as of the Closing Date. Purchaser has, in
connection  with its  decision  to  purchase  the  number of Shares set forth in
Exhibit A hereto,  relied solely upon the Offering  Memorandum and the documents
attached as appendices  thereto and the  representations  and  warranties of the
Company  contained  herein.  Such  Purchaser  will not,  directly or indirectly,
offer, sell, pledge,  transfer or otherwise dispose of (or solicit any offers to
buy, purchase or otherwise acquire or take a pledge of) any of the Shares except
in compliance with the Securities Act, and the rules and regulations promulgated
thereunder and applicable state securities laws.

     4.4  Registration  or  Exemption   Requirements.   Such  Purchaser  further
acknowledges,  understands  and  agrees  that the  Shares  may not be  resold or
otherwise  transferred  except in a transaction  registered under the Securities
Act or unless an exemption from such  registration is available.  Such Purchaser
understands that the certificate(s) evidencing the Shares will be imprinted with
a  legend  that  prohibits  the  transfer  of the  Shares  unless  (i)  they are
registered or such  registration  is not  required,  and (ii) if the transfer is
pursuant  to an  exemption  from  registration  other  than  Rule 144  under the
Securities  Act and, if the Company  shall so request in writing,  an opinion of
counsel  reasonably  satisfactory  to the Company is obtained to the effect that
the transaction is so exempt.

                                    Section 5

                       Conditions to Closing of Purchasers

     Each  Purchaser's  obligation  to purchase the Shares at the Closing is, at
the option of such  Purchaser,  subject to the  fulfillment  or waiver as of the
Closing Date of the following conditions:

     5.1 Representations and Warranties. The representations and warranties made
by the  Company in Section 3 hereof  shall be true and  correct in all  material
respects  when made,  and shall be true and correct in all material  respects on
the Closing  Date with the same force and effect as if they had been made on and
as of said date.




                                      E-9




     5.2 Covenants.  All covenants,  agreements and conditions contained in this
Agreement  to be  performed by the Company on or prior to the Closing Date shall
have been performed or complied with in all respects.

     5.3 Blue Sky. The Company shall have  obtained all  necessary  blue sky law
permits and  qualifications,  or secured exemptions  therefrom,  required by any
state or foreign or other jurisdiction for the offer and sale of the Shares.

     5.4 Legal Opinion.  The  Purchasers  shall have received a legal opinion of
Dorsey & Whitney LLP,  counsel to the  Company,  with respect to the matters set
forth on Exhibit C.

     5.5 Patent  Opinion.  The Purchasers  shall have received legal opinions of
patent  counsel to the Company  with respect to the matters set forth on Exhibit
D.

     5.6 Registration  Statement.  The Registration Statement (as defined below)
registering  the  resale of the Shares by the  Purchasers  shall have been filed
with  and  declared  effective  by the SEC,  and no stop  order  suspending  the
effectiveness thereof and no proceedings therefor shall be pending or threatened
by the SEC.

     5.7 Nasdaq  Qualification.  The Shares shall be duly authorized for listing
by the Nasdaq Stock Market.

                                    Section 6

                        Conditions to Closing of Company

     The Company's obligation to sell and issue the Shares at the Closing is, at
the option of the Company, subject to the fulfillment or waiver of the following
conditions:

     6.1  Representations  and  Warranties.  The  representations  made  by  the
Purchasers  in  Section  4  hereof  shall be true and  correct  in all  material
respects  when made,  and shall be true and correct in all material  respects on
the Closing  Date with the same force and effect as if they had been made on and
as of such date.

     6.2 Covenants.  All covenants,  agreements and conditions contained in this
Agreement  to be  performed  by the  Purchasers  on or prior to the Closing Date
shall have been performed or complied with in all material respects.

     6.3 Blue Sky. The Company shall have  obtained all  necessary  blue sky law
permits and  qualifications,  or secured exemptions  therefrom,  required by any
state for the offer and sale of the Shares.




                                      E-10




     6.4 Registration  Statement.  The Registration Statement (as defined below)
registering  the  resale of the Shares by the  Purchasers  shall have been filed
with  and  declared  effective  by the SEC,  and no stop  order  suspending  the
effectiveness thereof and no proceedings therefor shall be pending or threatened
by the SEC.

     6.5 Nasdaq  Qualification.  The Shares shall be duly authorized for listing
by the Nasdaq Stock Market.

                                    Section 7

                      Affirmative Covenants of the Company

     The Company hereby covenants and agrees as follows:

     7.1 Financial  Information.  The Company will mail the following reports to
each  Purchaser  until  such  Purchaser  transfers,  assigns or sells the Shares
purchased by such Purchaser pursuant to this Agreement:

          (a) Within one hundred (100) days after the end of each fiscal year, a
     copy of its Annual Report on Form 10-K.

          (b) Within fifty-five (55) days after the end of the first, second and
     third quarterly  accounting  periods of each fiscal year of the Company,  a
     copy of its Quarterly Report on Form 10-Q.

          (c) Within ten (10) days after the Company files any Current Report on
     Form 8-K with the SEC, such Current Report on Form 8-K

     7.2 Registration Requirements.

          (a) The  Company  shall use its best  efforts  to  prepare  and file a
     registration  statement  with the SEC under the  Securities Act to register
     the resale of the Shares by the Purchasers (the  "Registration  Statement")
     no later than ten (10) days after the date hereof.

          (b) The Company shall pay all Registration Expenses (as defined below)
     in connection with any registration, qualification or compliance hereunder,
     and each  Purchaser  shall pay all Selling  Expenses (as defined below) and
     other expenses that are not  Registration  Expenses  relating to the Shares
     resold by such  Purchaser.  Registration  Expenses shall mean all expenses,
     except for Selling Expenses,  incurred by the Company in complying with the
     registration  provisions herein described,  including,  without limitation,
     all registration,  qualification and filing fees, printing expenses, escrow
     fees, fees and disbursements of counsel for the Company,  blue sky fees and
     expenses,  and the expense of any special audits incident to or required by
     any such registration. Selling Expenses shall mean all selling commissions,



                                      E-11




     underwriting fees and stock transfer taxes applicable to the Shares and all
     fees and disbursements of counsel for any Purchaser.

          (c) In the case of the  registration  effected by the Company pursuant
     to these registration provisions,  the Company will use its reasonable best
     efforts to: (i) cause the Registration Statement to become effective within
     sixty (60) days of the date hereof,  (ii) keep such registration  effective
     until the earlier of (a) the second  anniversary  of the Closing Date,  (b)
     such date as all of the Shares have been resold by the original  Purchasers
     thereof,  or (c) such time as all of the Shares held by the  Purchasers can
     be sold  within a given  three-month  period  without  compliance  with the
     registration  requirements of the Securities Act pursuant to Rule 144 under
     the Securities Act; (iii) prepare and file with the SEC such amendments and
     supplements  to the  Registration  Statement  and  the  prospectus  used in
     connection  with the  Registration  Statement as may be necessary to comply
     with the provisions of the  Securities Act with respect to the  disposition
     of all securities covered by the Registration Statement;  (iv) furnish such
     number of prospectuses and other documents incident thereto,  including any
     amendment of or supplement to the  prospectus,  as a Purchaser from time to
     time may reasonably  request;  (v) cause all Shares registered as described
     herein  to be  listed  on  each  securities  exchange  and  quoted  on each
     quotation  service on which  similar  securities  issued by the Company are
     then listed or quoted;  (vi) provide a transfer agent and registrar for all
     Shares registered pursuant to the Registration Statement and a CUSIP number
     for all such Shares;  (vii)  otherwise  use its best efforts to comply with
     all  applicable  rules and  regulations  of the SEC;  and  (viii)  file the
     documents  required of the Company and  otherwise  use its best  efforts to
     maintain requisite blue sky clearance in (A) all jurisdictions in which any
     of the  Shares  are  originally  sold and (B) all other  states  reasonably
     specified  in writing by a Purchaser,  provided as to clause (B),  however,
     that in no event shall the Company be required to qualify to do business or
     consent  to  service  of  process  in any  state  in which it is not now so
     qualified or has not so consented.

          (d) The  Company  shall  furnish  to each  Purchaser  upon  request  a
     reasonable  number of copies of a  supplement  to or an  amendment  of such
     prospectus  as may be necessary in order to  facilitate  the public sale or
     other disposition of all or any of the Shares held by such Purchaser.

          (e) With a view to making  available to the Purchasers the benefits of
     Rule 144  promulgated  under the  Securities Act ("Rule 144") and any other
     rule or  regulation  of the SEC that may at any time permit a Purchaser  to
     sell  Shares  to  the  public  without   registration   or  pursuant  to  a
     registration on Form S-3, the Company covenants and agrees to: (i) make and
     keep  public  information  available,  as those  terms are  understood  and
     defined in Rule 144 under the Securities  Act, until the earlier of (A) the
     second  anniversary  of the  Closing  Date or (B)  such  date as all of the
     Shares shall have been resold by the original Purchasers thereof; (ii) file
     with the SEC in a timely manner all reports and other documents required of
     the  Company  under the  Securities  Act and the  Exchange  Act;  and (iii)
     furnish to any Purchaser  upon request,  as long as the Purchaser  owns any
     Shares,  (A) a written  statement by the Company that it has complied  with
     the reporting  requirements of the Securities Act and the Exchange Act, (B)
     a copy of the most recent annual or quarterly report of the Company, and



                                      E-12




     (C) such other information as may be reasonably requested in order to avail
     any Purchaser of any rule or regulation of the SEC that permits the selling
     of any such Shares without registration or pursuant to such Form S-3.

          (f) At any time the Company may refuse to permit a Purchaser to resell
     any Shares pursuant to the Registration Statement;  provided, however, that
     in order to exercise this right,  the Company must deliver a certificate in
     writing to the  Purchasers  and the  Placement  Agent to the effect  that a
     cessation  of  the  ability  to  sell  under,  or  a  withdrawal  of,  such
     Registration  Statement  is  necessary  because  a  sale  pursuant  to  the
     Registration   Statement  in  its  then-current  form  would  constitute  a
     violation of the federal  securities  laws.  In such an event,  the Company
     shall use its best efforts to promptly amend the Registration  Statement if
     necessary and take all other actions necessary to allow such sale under the
     federal  securities laws, and shall notify the Purchasers and the Placement
     Agent  promptly  after  it  has  determined   that  such  sale  has  become
     permissible  under  the  federal  securities  laws.   Notwithstanding   the
     foregoing,  the Company  shall not under any  circumstances  be entitled to
     exercise its right to withdraw the registration statement more then one (1)
     time in any twelve  (12) month  period,  and the period  during  which such
     Registration  Statement may be withdrawn  shall not exceed sixty (60) days.
     Each Purchaser hereby covenants and agrees that it will not sell any Shares
     pursuant to the Registration  Statement during the periods the Registration
     Statement is withdrawn  or the ability to sell  thereunder  is suspended as
     set forth in this Section 7.2(f).

     7.3 Indemnification and Contribution.

          (a) The Company  agrees to indemnify and hold harmless each  Purchaser
     from and against any losses,  claims, damages or liabilities (or actions or
     proceedings in respect  thereof) to which such Purchaser may become subject
     (under the  Securities  Act or otherwise)  insofar as such losses,  claims,
     damages or liabilities (or actions or proceedings in respect thereof) arise
     out of or are based upon, any untrue statement of a material fact contained
     in the Registration  Statement, on the effective date thereof, or arise out
     of any failure by the Company to fulfill  any  undertaking  included in the
     Registration Statement,  and the Company will, as incurred,  reimburse such
     Purchaser  for  any  legal  or  other  expenses   reasonably   incurred  in
     investigating, defending or preparing to defend any such action, proceeding
     or claim;  provided,  however,  that the Company shall not be liable in any
     such case to the extent that such loss,  claim,  damage or liability arises
     out of or is based upon (i) an untrue  statement made in such  Registration
     Statement  in reliance  upon and in  conformity  with  written  information
     furnished to the Company by or on behalf of such Purchaser specifically for
     use in preparation of the Registration Statement,  (ii) the failure of such
     Purchaser to comply with the covenants and agreements  contained in Section
     8.3  hereof,  or (iii)  any  untrue  statement  in any  Prospectus  that is
     corrected in any subsequent  Prospectus that was delivered to the Purchaser
     prior to the pertinent sale or sales by the Purchaser.

          (b) Each Purchaser, severally and not jointly, agrees to indemnify and
     hold harmless the Company from and against any losses,  claims,  damages or
     liabilities  (or actions or  proceedings  in respect  thereof) to which the
     Company may become subject (under the


                                      E-13



     Securities  Act or otherwise)  insofar as such losses,  claims,  damages or
     liabilities (or actions or proceedings in respect  thereof) arise out of or
     are based upon (i) an untrue statement made in such Registration  Statement
     in reliance upon and in conformity  with written  information  furnished to
     the  Company  by or on behalf  of such  Purchaser  specifically  for use in
     preparation  of the  Registration  Statement,  provided,  however,  that no
     Purchaser  shall be  liable  in any  such  case  for any  untrue  statement
     included in any Prospectus which statement has been corrected,  in writing,
     by such  Purchaser and delivered to the Company  before the sale from which
     such loss  occurred,  (ii) the failure of such Purchaser to comply with the
     covenants  and  agreements  contained  in Section 8.3 hereof,  or (iii) any
     untrue  statement in any  prospectus  that is  corrected in any  subsequent
     Prospectus  that was delivered to the Purchaser prior to the pertinent sale
     or sales by the Purchaser,  and each Purchaser,  severally and not jointly,
     will, as incurred,  reimburse  the Company for any legal or other  expenses
     reasonably incurred in investigating,  defending or preparing to defend any
     such action, proceeding or claim.

          (c) Promptly after receipt by any indemnified  person of a notice of a
     claim or the beginning of any action in respect of which indemnity is to be
     sought against an  indemnifying  person  pursuant to this Section 7.3, such
     indemnified person shall notify the indemnifying  person in writing of such
     claim or of the commencement of such action, and, subject to the provisions
     hereinafter  stated,  in case any such action  shall be brought  against an
     indemnified  person and the  indemnifying  person shall have been  notified
     thereof,  the indemnifying person shall be entitled to participate therein,
     and, to the extent that it shall wish, to assume the defense thereof,  with
     counsel  reasonably  satisfactory to the indemnified  person.  After notice
     from the indemnifying person to such indemnified person of the indemnifying
     person's  election to assume the defense thereof,  the indemnifying  person
     shall not be  liable  to such  indemnified  person  for any legal  expenses
     subsequently  incurred by such  indemnified  person in connection  with the
     defense thereof,  provided,  however, that if there exists or shall exist a
     conflict of interest  that would make it  inappropriate  in the  reasonable
     judgment of the  indemnified  person for the same counsel to represent both
     the  indemnified  person and such  indemnifying  person or any affiliate or
     associate  thereof,  the indemnified person shall be entitled to retain its
     own counsel at the expense of such indemnifying person.

          (d)  If  the  indemnification  provided  for in  this  Section  7.3 is
     unavailable to or insufficient to hold harmless an indemnified  party under
     subsection  (a) or (b) above in respect of any losses,  claims,  damages or
     liabilities  (or actions or  proceedings  in respect  thereof)  referred to
     therein,  then each indemnifying  party shall contribute to the amount paid
     or  payable by such  indemnified  party as result of such  losses,  claims,
     damages or liabilities  (or actions in respect  thereof) in such proportion
     as is  appropriate  to reflect the relative fault of the Company on the one
     hand and the  Purchasers on the other in connection  with the statements or
     omissions which resulted in such losses, claims, damages or liabilities (or
     actions  in  respect  thereof),  as well as any  other  relevant  equitable
     considerations.  The relative  fault shall be  determined  by reference to,
     among other  things,  whether the untrue or alleged  untrue  statement of a
     material fact or the omission or alleged  omission to state a material fact
     relates  to  information  supplied  by the  Company  on the  one  hand or a
     Purchaser on the other and the parties' relative intent, knowledge,  access
     to information and opportunity to correct or prevent such statement or



                                      E-14




     omission.  The Company and the  Purchasers  agree that it would not be just
     and  equitable  if  contribution  pursuant  to  this  subsection  (d)  were
     determined by pro rata  allocation  (even if the Purchasers were treated as
     one entity for such  purpose) or by any other  method of  allocation  which
     does not take account of the equitable  considerations referred to above in
     this subsection (d). The amount paid or payable by an indemnified  party as
     a result of the  losses,  claim,  damages,  or  liabilities  (or actions in
     respect  thereof)  referred to above in this subsection (d) shall be deemed
     to  include  any  legal  or  other  expenses  reasonably  incurred  by such
     indemnified  party in connection with  investigating  or defending any such
     action or claim.  Notwithstanding the provisions of this subsection (d), no
     Purchaser  shall be  required  to  contribute  any  amount in excess of the
     amount by which the net amount  received by the Purchaser  from the sale of
     the Shares to which such loss  relates  exceeds  the amount of any  damages
     which such  Purchaser has otherwise  been required to pay by reason of such
     untrue or alleged  untrue  statement  or omission or alleged  omission.  No
     person  guilty of  fraudulent  misrepresentation  (within  the  meaning  of
     Section 11(f) of the Securities Act) shall be entitled to contribution from
     any  person who was not guilty of such  fraudulent  misrepresentation.  The
     Purchasers' obligations in this subsection (d) to contribute are several in
     proportion to their  respective  sales of Shares to which such loss relates
     and not joint.

          (e) The  obligations  of the  Company  and the  Purchasers  under this
     Section 7.3 shall be in addition to any liability which the Company and the
     respective  Purchasers may otherwise  have and shall extend,  upon the same
     terms and conditions,  to each person,  if any, who controls the Company or
     any Purchaser within the meaning of the Act.

                                    Section 8

                   Restrictions on Transferability of Shares:
                          Compliance with Securities Act

     8.1 Restrictions on  Transferability.  The Shares shall not be transferable
in the  absence  of a  registration  under the  Securities  Act or an  exemption
therefrom or in the absence of compliance with any term of this  Agreement.  The
Company  shall be entitled to give stop  transfer  instructions  to its transfer
agent with respect to the Shares in order to enforce the foregoing restrictions.

     8.2 Restrictive  Legend.  Each certificate  representing  Shares shall bear
substantially  the following  legends (in addition to any legends required under
applicable securities laws):

               THE SHARES  REPRESENTED  BY THIS  CERTIFICATE
               HAVE BEEN  ACQUIRED FOR  INVESTMENT  PURPOSES
               ONLY AND HAVE NOT BEEN  REGISTERED  UNDER THE
               SECURITIES ACT OF 1933. THE SHARES MAY NOT BE
               SOLD OR  TRANSFERRED  IN THE  ABSENCE OF SUCH
               REGISTRATION OR AN EXEMPTION THEREFROM.



                                      E-15



               ADDITIONALLY   THE  TRANSFER  OF  THE  SHARES
               REPRESENTED BY THIS CERTIFICATE IS SUBJECT TO
               CERTAIN RESTRICTIONS  SPECIFIED IN THE COMMON
               STOCK PURCHASE  AGREEMENT DATED JUNE 25, 1998
               BETWEEN   THE   COMPANY   AND  THE   ORIGINAL
               PURCHASER, AND NO TRANSFER OF SHARES SHALL BE
               VALID OR  EFFECTIVE  ABSENT  COMPLIANCE  WITH
               SUCH RESTRICTIONS.  ALL SUBSEQUENT HOLDERS OF
               THIS CERTIFICATE WILL HAVE AGREED TO BE BOUND
               BY  CERTAIN  OF THE  TERMS OF THE  AGREEMENT,
               INCLUDING   SECTIONS   7.2  AND  8.3  OF  THE
               AGREEMENT.  COPIES  OF THE  AGREEMENT  MAY BE
               OBTAINED AT NO COST BY WRITTEN  REQUEST  MADE
               BY THE REGISTERED  HOLDER OF THIS CERTIFICATE
               TO THE SECRETARY OF THE COMPANY.

     The legend  contained in this Section 8.2 may be removed from a certificate
either in  accordance  with  Section  8.3 or  immediately  upon  receipt  by the
Transfer  Agent of a certificate  substantially  in the form attached  hereto as
Exhibit E.

     8.3 Transfer of Shares After Registration.  Each Purchaser hereby covenants
with the  Company  not to make  any  sale of the  Shares  except  either  (i) in
accordance with the Registration Statement, in which case Purchaser covenants to
comply with the  requirement  of  delivering  a current  prospectus,  or (ii) in
accordance with Rule 144, in which case Purchaser  covenants to comply with Rule
144.  Purchaser  further  acknowledges  and  agrees  that  such  Shares  are not
transferable on the books of the Company unless the certificate submitted to the
Company's  transfer  agent  evidencing  such Shares is accompanied by a separate
certificate  executed by an officer of, or other person duly  authorized by, the
Purchaser in the form attached hereto as Exhibit F.

     8.4 Purchaser  Information.  Each Purchaser covenants that it will promptly
notify  the  Company  of  any  changes  in  the  information  set  forth  in the
Registration  Statement  regarding such Purchaser or such  Purchaser's  "Plan of
Distribution."

                                    Section 9

                                  Miscellaneous

     9.1 Waivers and  Amendments.  With the  exception  of Sections  7.1 and 7.2
hereof,  the terms of this  Agreement  may be waived or amended with the written
consent of the Company and each Purchaser.  With respect to Sections 7.1 and 7.2
hereof,  with the written  consent of the Company and the record holders of more
than fifty percent (50%) of the Shares then  outstanding and held by Purchasers,
the terms of the Agreement may be waived or amended



                                      E-16




and any such  amendment  or waiver  shall be binding  upon the  Company  and all
holders of Shares.

     9.2  Placement  Agent Fee.  Each  Purchaser  acknowledges  that the Company
intends to pay a fee to SBC Warburg  Dillon Read Inc. and  Evolution  Capital in
respect of the sale of the Shares to the  Purchaser.  Each of the parties hereto
hereby  represents that, on the basis of any actions and agreements by it, there
are no other brokers or finders  entitled to compensation in connection with the
sale of the Shares to the Purchasers.

     9.3 Governing Law. This Agreement  shall be governed in all respects by and
construed  in  accordance  with the laws of the  State of New York  without  any
regard to conflicts of laws principles.

     9.4 Survival.  The  representations,  warranties,  covenants and agreements
made in this Agreement  shall survive any  investigation  made by the Company or
the Purchasers and the Closing.

     9.5  Successors  and  Assigns.  The  provisions  hereof  shall inure to the
benefit of, and be binding upon, the successors,  assigns,  heirs, executors and
administrators of the parties to this Agreement.  Notwithstanding the foregoing,
no Purchaser  shall assign this Agreement  without the prior written  consent of
the Company.

     9.6  Entire  Agreement.  This  Agreement  constitutes  the full and  entire
understanding  and  agreement  between the parties  with regard to the  subjects
thereof.

     9.7  Notices,  etc.  All  notices  and  other  communications  required  or
permitted  under this Agreement  shall be effective upon receipt and shall be in
writing and may be delivered in person, by telecopy,  overnight delivery service
or  registered or certified  United States mail  addressed to the Company or the
Purchasers,  as the case may be, at their respective  addresses set forth at the
beginning  of this  Agreement  or on Exhibit A or at such  other  address as the
Company or the  Purchasers  shall have  furnished to the other party in writing.
All  notices and other  communications  shall be  effective  upon the earlier of
actual  receipt  thereof by the person to whom  notice is directed or (i) in the
case of notices and  communications  sent by personal delivery or telecopy,  one
business  day after  such  notice or  communication  arrives  at the  applicable
address or was successfully sent to the applicable  telecopy number, (ii) in the
case of notices and communications  sent by overnight delivery service,  at noon
(local  time) on the  second  business  day  following  the day such  notice  or
communication was sent, and (iii) in the case of notices and communications sent
by United States mail seven days after such notice or  communication  shall have
been deposited in the United States mail.

     9.8  Severability  of this  Agreement.  If any provision of this  Agreement
shall be judicially  determined  to be invalid,  illegal or  unenforceable,  the
validity,  legality and enforceability of the remaining  provisions shall not in
any way be affected or impaired thereby.




                                      E-17




     9.9  Counterparts.  This  Agreement  may  be  executed  in  any  number  of
counterparts,  each of which  shall be an  original,  but all of which  together
shall constitute one instrument.

     9.10 Further Assurances.  Each party to this Agreement shall do and perform
or cause to be done and  performed  all such  further  acts and things and shall
execute and deliver all such other  agreements,  certificates,  instruments  and
documents as the other party hereto may reasonably request in order to carry out
the intent and accomplish the purposes of this Agreement and the consummation of
the transactions contemplated hereby.

     9.11 Termination.  In the event that the Closing shall not have occurred on
or before sixty (60) days from the date hereof,  the  Purchasers  shall have the
option to terminate this Agreement at the close of business on such date, and in
the event that the Closing shall not have occurred on or before ninety (90) days
from the date hereof, this Agreement shall terminate at the close of business on
such date.

     9.12  Expenses.  The  Company  and each such  Purchaser  shall bear its own
expenses  incurred  on its  behalf  with  respect  to  this  Agreement  and  the
transactions contemplated hereby, including fees of legal counsel.

     9.13 Currency.  All references to "dollars" or "$" in this Agreement  shall
be deemed to refer to United States dollars.



                                      E-18




     The  foregoing  agreement  is hereby  executed  as of the date first  above
written.


                                   "COMPANY"

                                   ENZON, INC.
                                   a Delaware corporation


                                   By:
                                      ------------------------------------------

                                   Title:
                                         ---------------------------------------


                                   "PURCHASERS"


                                   THE DCF LIFE SCIENCES FUND, LTD.



                                   By:
                                      ------------------------------------------

                                   Name:
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   DCF PARTNERS, L.P.



                                   By:
                                      ------------------------------------------

                                   Name:
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------









                                      E-19




                                   ARIES DOMESTIC FUND, L.P.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   THE ARIES TRUST



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                         ---------------------------------------

                                   Title:
                                         ---------------------------------------



                                   HAUSMANN HOLDINGS, N.V.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                         ---------------------------------------

                                   Title:
                                         ---------------------------------------














                                      E-20




                                   ORACLE OFFSHORE LTD.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   ORACLE PARTNERS L.P.



                                   By:    
                                      ------------------------------------------

                                   Name:  
                                        ----------------------------------------

                                   Title: 
                                         ---------------------------------------



                                   ORACLE INSTITUTIONAL PARTNERS



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------














                                      E-21




                                   GSAM ORACLE FUND, INC.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   SBC WARBURG DILLON READ, INC.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   SBC WARBURG DILLON READ, INC.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------














                                      E-22




                                   CACLUCEUS CAPITAL L.P.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   CACLUCEUS CAPITAL LTD.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   MERLIN BIOMED L.P.



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------













                                      E-23




                                   DEUTSCHE VERMOGEN SBILDUNGSGESELL
                                   SCHAFT MBH



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   WAYNE P. ROTHBAUM



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------



                                   MITCHELL D. SILBER



                                   By:   
                                      ------------------------------------------

                                   Name: 
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------













                                      E-24




                                   NEW TECHNOLOGIES FUND




                                   By:
                                      ------------------------------------------

                                   Name:
                                        ----------------------------------------

                                   Title:
                                         ---------------------------------------







                                      E-25


                                    Exhibit A
                                     to CSPA




               Purchaser                           Shares       Purchase Price
               ---------                           ------       --------------
                                                             
                                                                 
DCF Life Sciences Fund Ltd.                       200,000       $   950,000

DCF Partners, L.P.                                853,000       $ 4,051,750

     C/O DCF Capital
     660 Steamboat Road
     Greenwich, CT 06830
     Attn: Mr. Doug Floren
     Facsimile: (203) 618-1495

Oracle Partners, L.P.                             315,789       $ 1,499,997.75

Oracle Institutional Partners, L.P.                78,496       $   372,856

GSAM Oracle Fund, Inc.                            168,721       $   801,424.75

Haussmann Holdings, N.V                            50,526       $   239,998.50

Oracle Offshore Ltd.                               18,046       $    85,718.50

     C/O Oracle Partners, L.P.
     712 Fifth Avenue, 45th Floor
     New York, NY 10019
     Attn: Mr. Norman Schleffer
     Facsimile: (212) 459-0863

SBC Warburg Dillon Read, Inc.                     500,000       $ 2,375,000

     141 West Jackson Blvd.
     Chicago, IL  60604
     Attn: Mr. James Del Medico
     Facsimile: (312) 554-6332

Caduceus Capital L.P.                             105,000       $   498,750

Caduceus Capital Ltd.                             220,000       $ 1,045,000

     C/O Orbimed Advisors LLC
     767 Third Avenue, 6th Floor
     New York, NY 10017
     Attn: Mr. Sven H. Borho
     Facsimile: (212) 739-6444

Merlin BioMed LP                                   21,053       $   100,001.75

Deutsche Vermogen                                 294,737       $ 1,400,000.75
Sbildungsgesell Shaft mbH

     C/O Merlin Biomed
     237 Park Avenue, Suite 801
     New York, NY 10017
     Attn: Ms. Jennifer Stoler
     Facsimile: (212) 808-7422

The Aries Trust                                   747,368         3,549,998

Aries Domestic Fund, L.P.                         305,264         1,450,004

     C/O Paramount Capital Asset
       Management, Inc.
     787 Seventh Avenue
     New York, NY 10019
     Attn: Mr. David Tanen
     Facsimile: (212) 554-4355

Wayne P. Rothbaum                                  30,000       $   142,500

Mitchell D. Silber                                 15,000       $    71,250

     C/O The Carson Group
     156 West 56th Street
     10th Floor
     New York, NY 10019
     Attn: Mr. Wayne Rothbaum

New Technologies Fund                              60,000       $   285,000

     C/O Emerging Growth
       Management Co.
     One Embarcadero Center
     Suite 2410
     San Francisco, CA 94111
     Attn: Mr. Marc Pentopoulos
     Facsimile: (415) 782-9645
                                               ----------       --------------
                                                3,983,000       $18,919,250
                                               ==========       ==============
                                                   



                                      E-26


                                    Exhibit B

                         INSTRUCTION SHEET FOR PURCHASER

                   (to be read in conjunction with the entire
                        Common Stock Purchase Agreement)

A.   Complete the following items in the Common Stock Purchase Agreement:

     1.   Provide the  information  regarding  the  Purchaser  requested  on the
          signature  page.  The  Agreement  must be  executed  by an  individual
          authorized to bind the Purchaser.

     2.   Exhibit B-1 - Stock Certificate Questionnaire:

          Provide   the   information   requested   by  the  Stock   Certificate
          Questionnaire;

     3.   Exhibit B-2 - Registration Statement Questionnaire:

          Provide  the  information  requested  by  the  Registration  Statement
          Questionnaire.

     4.   Exhibit B-3 - Purchaser Certificate:

          Provide the  information  requested by the  Certificate for Individual
          Purchasers  or the  Certificate  for  Corporate,  Partnership,  Trust,
          Foundation and Joint Purchasers, as applicable.

     5.   Return the signed Purchase Agreement  including the properly completed
          Exhibit 4.2 to:

                         Brobeck, Phleger & Harrison LLP
                         1633 Broadway, 47th Floor
                         New York, New York 10019
                         Telephone: (212) 581-1600
                         Attn: Heather Willens, Esq.

B.   Instructions  regarding  the  transfer of funds for the  purchase of Shares
     will be telecopied to the Purchaser by the Placement Agent at a later date.

C.   Upon the  resale of the  Shares  by the  Purchaser  after the  Registration
     Statement  covering the Shares is  effective,  as described in the Purchase
     Agreement, the Purchaser:

          (i)  must  deliver a current  prospectus,  and  annual  and  quarterly
               reports of the Company to the buyer (prospectuses, and annual and
               quarterly  reports  may  be  obtained  from  the  Company  at the
               Purchaser's request); and

          (ii) must send a letter in the form of  Exhibit  D to the  Company  so
               that the Shares may be properly transferred.



                                      E-27


                                   Exhibit B-1

                                   ENZON, INC.

                         STOCK CERTIFICATE QUESTIONNAIRE


                  Pursuant to Section 4.3 of the  Agreement,  please  provide us
with the following information:


1.   The exact name that the Shares are to be
     registered in (this is the name that will
     appear on the stock certificate(s)). You may
     use a nominee name if appropriate:            _____________________________

2.   The relationship between the Purchaser of the
     Shares and the Registered Holder listed in
     response to item 1 above:                     _____________________________

3.   The mailing address of the Registered Holder
     listed in response to item 1 above:           _____________________________


                                                   _____________________________


                                                   _____________________________


                                                   _____________________________


                                                   _____________________________

4.   The Tax Identification Number of the
     Registered Holder listed in response to item
     1 above:                                      _____________________________







                                      E-28




                                   Exhibit B-2

                                   ENZON, INC.

                      REGISTRATION STATEMENT QUESTIONNAIRE


     In connection with the preparation of the  Registration  Statement,  please
provide us with the following information regarding the Purchaser.

     1. Please state your organization's name exactly as it should appear in the
Registration Statement:


     2. Have you or your organization had any position, office or other material
relationship  within the past three  years  with the  Company or its  affiliates
other  than  as  disclosed  in  the  prospectus  included  in  the  Registration
Statement?

     _____ Yes        _____ No

     If yes, please indicate the nature of any such relationship below:


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


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


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


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




                                      E-29




                                   Exhibit B-3

                                   ENZON, INC.

                      CERTIFICATE FOR INDIVIDUAL PURCHASERS


     If  the  investor  is an  individual  Purchaser  (or  married  couple)  the
Purchaser must complete, date and sign this Certificate.

                                   CERTIFICATE

     I  certify  that  the  representations  and  responses  below  are true and
accurate:

     In order for the Company to offer and sell the Shares in  conformance  with
state and federal  securities  laws, the following  information must be obtained
regarding your investor status.  Please initial each category  applicable to you
as an investor in the Company.

     ___ (1) A natural  person whose  individual  net worth,  or joint net worth
with that person's spouse, at the time of his purchase exceeds $1,000,000;

     ___ (2) A natural person who had an individual income in excess of $200,000
in each of the two most recent years,  or joint income with that person's spouse
in excess of $300,000, in each of those years, and has a reasonable  expectation
of reaching the same income level in the current year;

     ___ (3) An executive officer or director of the Company.




Dated: __________________           ____________________________________________
                                    Name(s) of Purchaser

                                    ____________________________________________
                                    Signature

                                    ____________________________________________
                                    Signature





                                      E-30




                                   Exhibit B-4

                                   ENZON, INC.

                     CERTIFICATE FOR CORPORATE, PARTNERSHIP,
                     TRUST, FOUNDATION AND JOINT PURCHASERS


     If  the  investor  is a  corporation,  partnership,  trust,  pension  plan,
foundation,  joint purchaser  (other than a married couple) or other entity,  an
authorized  officer,  partner,  or  trustee  must  complete,  date and sign this
Certificate.

                                   CERTIFICATE

     The undersigned  certifies that the representations and responses below are
true and accurate:

     (a) The investor has been duly formed and is validly  existing and has full
power and  authority to invest in the Company.  The person  signing on behalf of
the  undersigned  has the  authority  to execute and  deliver  the Common  Stock
Purchase  Agreement on behalf of the  Purchaser  and to take other  actions with
respect thereto.

     (b) Indicate the form of entity of the undersigned:

         ____  Limited Partnership

         ____  General Partnership

         ____  Corporation

         ____  Revocable  Trust  (identify  each grantor and indicate under what
               circumstances the trust is revocable by the grantor):
               _________________________________________________________________
               _________________________________________________________________
               _________________________________________________________________
               _________________________________________________________________
               _________________________________________________________________
               ________.  (Continue on a separate piece of paper, if necessary.)

          ____ Other type of Trust (indicate type of trust and, for trusts other
               than pension trusts, name the grantors and beneficiaries):_______
               _________________________________________________________________
               _________________________________________________________________
               _________________________________________________________________
               ________.  (Continue on a separate piece of paper, if necessary.)



                                      E-31


          ____ Other form of organization (indicate form of organization (____
               _______________________________________________________________).

     (c) Indicate the approximate date the undersigned entity was formed: ______
____________________.

     (d) In order for the  Company to offer and sell the  Shares in  conformance
with state and  federal  securities  laws,  the  following  information  must be
obtained regarding your investor status. Please initial each category applicable
to you as an investor in the Company.

          ____ 1. A bank as defined in Section 3(a)(2) of the Securities Act, or
               any savings and loan association or other  institution as defined
               in Section 3(a)(5)(A) of the Securities Act whether acting in its
               individual or fiduciary capacity;

          ____ 2. A broker or dealer  registered  pursuant  to Section 15 of the
               Securities Exchange Act of 1934;

          ____ 3. An  insurance  company  as  defined  in  Section  2(13) of the
               Securities Act;

          ____ 4. An investment  company registered under the Investment Company
               Act of 1940 or a  business  development  company  as  defined  in
               Section 2(a)(48) of that Act;

          ____ 5. A Small Business Investment Company licensed by the U.S. Small
               Business  Administration under Section 301(c) or (d) of the Small
               Business Investment Act of 1958;

          ____ 6. A plan  established  and maintained by a state,  its political
               subdivisions,  or any agency or instrumentality of a state or its
               political subdivisions, for the benefit of its employees, if such
               plan has total assets in excess of $5,000,000;

          ____ 7. An employee  benefit  plan within the meaning of the  Employee
               Retirement  Income  Security  Act  of  1974,  if  the  investment
               decision is made by a plan fiduciary, as defined in Section 3(21)
               of  such  Act,   which  is  either  a  bank,   savings  and  loan
               association, insurance company, or registered investment advisor,
               or if the  employee  benefit  plan has total  assets in excess of
               $5,000,000 or, if a self-directed plan, with investment decisions
               made solely by persons that are accredited investors;

          ____ 8. A private business  development  company as defined in Section
               202(a)(22) of the Investment Advisers Act of 1940;



                                      E-32





          ____ 9. An organization described in Section 501(c)(3) of the Internal
               Revenue  Code,  corporation,  Massachusetts  or similar  business
               trust,  or  partnership,  not formed for the specific  purpose of
               acquiring the Shares, with total assets in excess of $5,000,000;

          ____ 10. A trust,  with  total  assets in excess  of  $5,000,000,  not
               formed for the specific  purpose of acquiring  the Shares,  whose
               purchase is directed by a  sophisticated  person as  described in
               Rule 506(b)(2)(ii) of the Exchange Act;

          ____ 11. An entity in which all of the equity owners qualify under any
               of the above  subparagraphs.  If the undersigned  belongs to this
               investor   category   only,   list  the  equity   owners  of  the
               undersigned,  and the  investor  category  which each such equity
               owner satisfies:

               _________________________________________________________________
               _________________________________________________________________
               _________________________________________________________________
               ________________________________________________________________.
               (Continue on a separate piece of paper, if necessary.)



Dated: _________________________, 19__

______________________________________
Name of investor



_____________________________________________________________
Signature and title of authorized officer, partner or trustee






                                      E-33


                                    Exhibit C

                           Opinion of Company Counsel


                                      E-34


                                    EXHIBIT C

                                                                           DRAFT



                              [Closing Date], 1998

[                 ]


     Re: Enzon, Inc. - Sale of Common Stock


Ladies and Gentlemen:

     We have acted as counsel to Enzon,  Inc. (the "Company") in connection with
the sale by the Company of shares of common stock of the Company (the  "Shares")
pursuant to the Common Stock  Purchase  Agreement  (the  "Purchase  Agreement"),
dated as of June [ ], 1998, by and between the Company and the investors  listed
on  Schedule A thereto  (the  "Purchasers").  This  opinion  is being  delivered
pursuant to Section 5.4 of the Purchase  Agreement.  All capitalized  terms used
herein and not defined  herein have the  meanings  assigned to such terms in the
Purchase Agreement.

     We have examined such  documents and have reviewed such questions of law as
we have  considered  necessary and  appropriate for the purposes of our opinions
set forth below.

     In rendering our opinions set forth below, we have assumed the authenticity
of all documents submitted to us as originals, the genuineness of all signatures
and the  conformity to authentic  originals of all documents  submitted to us as
copies. We have also assumed the legal capacity for all purposes relevant hereto
of all  natural  persons  and,  with  respect to all  parties to  agreements  or
instruments  relevant  hereto other than the Company,  that such parties had the
requisite power and authority  (corporate or otherwise) to execute,  deliver and
perform such agreements or instruments, that such agreements or instruments have
been duly  authorized  by all requisite  action  (corporate or otherwise) on the
part of such parties and have been duly  executed and  delivered by such parties
and that such agreements or instruments  are the valid,  binding and enforceable
obligations  of such parties.  As to questions of fact material to our opinions,
we have relied upon the representations  made in the Purchase Agreement and upon
certificates  of officers of the  Company  and of public  officials  (including,
without limitation, those certificates delivered to others at the Closing).




                                      E-35




     Our opinions expressed below as to certain factual matters are qualified as
being  limited  "to our  knowledge"  or by other  words  to the same or  similar
effect.  Such words, as used herein, mean the information known to the attorneys
in the firm who have principally  represented the Company in connection with the
transactions contemplated by the Purchase Agreement. In rendering such opinions,
we have not  conducted any  independent  investigation  or consulted  with other
attorneys in our firm with respect to the matters covered thereby.  No inference
as to our knowledge  with respect to such matters  should be drawn from the fact
of our representation of the Company.

     Based on the foregoing, we are of the opinion that:

     1. The Company is a corporation duly incorporated,  validly existing and in
good standing under the laws of the State of Delaware.

     2. The  Company has the  corporate  power and  authority  to enter into the
Purchase  Agreement and to issue,  sell and deliver to the Purchasers the Shares
to be issued and sold by it thereunder.

     3.  The  Purchase  Agreement  has been  duly  authorized  by all  necessary
corporate  action  on the part of the  Company  and has been duly  executed  and
delivered by the Company.

     4.  The  performance  by the  Company  of the  Purchase  Agreement  and the
consummation by the Company of the transactions  therein  contemplated  will not
(a) violate any provision of the Company's  charter or bylaws or any  applicable
statute,  rule or regulation,  or (b) result in the material breach or violation
of  any of the  terms  and  provisions,  or  constitute  a  default  under,  any
indenture,  mortgage,  deed of trust,  loan  agreement,  bond,  debenture,  note
agreement or other  evidence of  indebtedness,  or any lease,  contract or other
agreement or instrument  known to us to which the Company is a party or by which
its properties are bound, or, to our knowledge, any order, writ or decree of any
court or governmental  agency or body having  jurisdiction over the Company,  or
over any of its properties or operations;  provided, however, that we express no
opinion herein regarding state or foreign securities or Blue Sky laws.

     5. The Purchase Agreement constitutes a valid and binding obligation of the
Company, enforceable against the Company according to its terms.




                                      E-36




     6. The  Shares  to be issued by the  Company  pursuant  to the terms of the
Purchase  Agreement will be, upon issuance and delivery against payment therefor
in accordance  with the terms  thereof,  duly  authorized and validly issued and
fully  paid and  nonassessable,  and the  stockholders  of the  Company  have no
preemptive or other rights to purchase any of the Shares.

     The  opinions set forth above are subject to the  following  qualifications
and exceptions:

          (a)  Our  opinions  are  subject  to  the  effect  of  any  applicable
     bankruptcy, insolvency, reorganization,  moratorium or other similar law of
     general  application  affecting  creditors' or secured  creditors'  rights,
     including (without limitation) applicable fraudulent transfer laws.

          (b) Our  opinions are subject to the effect of general  principles  of
     equity,   including   (without   limitation)   concepts   of   materiality,
     reasonableness,  good faith and fair dealing,  and other similar  doctrines
     affecting the enforceability of agreements generally (regardless of whether
     considered in a proceeding in equity or at law).

          (c) Our opinions are subject to possible judicial action giving effect
     to governmental actions or foreign laws affecting creditors' rights.

          (d)  Our   opinions,   insofar  as  they  relate  to   indemnification
     provisions,  are subject to the effect of federal and state securities laws
     and public policy relating thereto.

     Our  opinions  expressed  above are  limited to the law of the State of New
York, the Delaware  General  Corporation Law, and the federal laws of the United
States of America.

     The foregoing  opinions are being  furnished to you solely for your benefit
and may not be relied upon by, nor may copies be delivered  to, any other person
without our prior written consent.

                                           Very truly yours,





                                      E-37




                                    Exhibit D

                           OPINIONS OF PATENT COUNSEL






                                      E-38


                   [LETTERHEAD OF ROBERTS & MERCANTI, L.L.P.]



                                 June 25, 1998

The Purchasers in the
Enzon, Inc. Common Stock
Purchase Agreement
dated June 25, 1998
and
SBC Warburg Dillon Read, Inc
535 Madison Avenue
New York, New York 10022

                 Re: Opinion of Intellectual Property Counsel with Respect to
                 Enzon's PEG INTRON A Technologies and Proprietary Rights 
                 Our Reference 213 1092
    
Ladies and Gentlemen:

     Our client, Enzon, Inc., a Delaware corporation (the "Company"), has
requested that we furnish to you our opinion in respect of certain matters
relating to the Company's PEG INTRON A technologies, and pursuant to Section 5.5
of the Common Stock Purchase Agreement, dated June 25, 1998, between SBC
Warburg Dillon Read, Inc. (the "Placement Agent") and the Company (the Placement
Agent Agreement"). Capitalized terms not otherwise defined herein shall have the
meaning ascribed to them, in the Purchase Agreement.

     For the purposes of rendering the opinions set forth below, we have either
reviewed the following in the course of preparing this opinion or else we have
reviewed the following in the course of our representation of the Company
(collectively the "Documents"):

     1.   the Purchase Agreement;

     2.   that certain Private Placement Offering Memorandum (the "Memorandum")
          dated June 2, 1998, together with any and all exhibits and amendments
          thereto;

     3.   the patents and patent applications listed on Schedule 1 attached
          hereto, which include all of the patents and patent applications
          referred to in the memorandum (the "Patents and Patent Applications")
          with respect to the Company's PEG


                                      E-39



SBC Warburg Dillon Read, Inc.
June 25, 1998
Page 2


          INTRON A technologies and which are divided into category A, which are
          the patents and patent applications owned by the Company and the
          Company's subsidiaries listed on Schedule 2 attached hereto (the
          "Subsidiaries") (collectively, the "Owned Patent Rights")
          collectively, and category B, which are the patents and patent
          applications licensed by the Company and its Subsidiaries
          (collectively, the "Licensed Patent Rights");

     4.   copies of the license agreements listed on Schedule 3 attached hereto
          (collectively, the "License Agreements"); 

     5.   copies of assignments relevant to ownership of the Patents and Patent
          Applications, 

     6.   the results of searches in the United States Patent and Trademark
          Office ("USPTO"), completed on June 4, 1998 in relation to the USPTO's
          record of title to the United States patents and patent applications
          within the Patents and Patent Applications;

     7.   any and all references cited to, or by, the USPTO during the
          prosecution of the United States patents and patent applications
          included within the Patents and Patent Applications;

     8.   the documents referred to in those opinions of this firm which we
          delivered to the Company relating to the Owned Patent Rights or
          relating to whether the PEG INTRON A products or proposed products of
          the Company infringe patents belonging to any third parties;

     9.   the internal files of this firm pertaining to the Owned Patent Rights.

         Whenever our opinions herein are qualified by the phrase "to our best
knowledge," except as may be further qualified below, such language means
that based upon the Documents, the actual knowledge of attorneys within our firm
(i.e., not including matters as to which such attorneys could be deemed to have
constructive knowledge) and inquiries of officers, directors and employees of
the Company, we believe that such opinions are factually correct.

     (1)  To our best knowledge, the Company and its Subsidiaries are the sole
          owners of the Owned Patent Rights and have obtained currently
          effective licenses to the Licensed Patent Rights pursuant to the
          License Agreements.


                                      E-40




SBC Warburg Dillon Read, Inc.
June 25, 1998
Page 3


     (2)  The Company and its Subsidiaries are listed in the records of the
          USPTO as the sole owners of the United States patents and patent
          applications within the Owned Patent Rights.

     (3)  The Licensors are listed in the records of the USPTO as the sole
          owners of the United States patents and patent applications within the
          Licensed Patent Rights.

     (4)  To our best knowledge, the Company and its Subsidiaries have good and
          marketable title to the Owned Patent Rights, free of any liens,
          pledges, claims, security interests or other encumbrances, but
          excluding those licenses set forth on Schedule 4.

     (5)  To our best knowledge, there is no information which would preclude
          the grant of patent from each of the patent applications within the
          Patents and Patent Applications, it being understood that there can be
          no certainty as to which adjustments may be made to the claims as part
          of the prosecution process within the PTO.

     (6)  To our best knowledge, the Company, the Subsidiaries and the Licensors
          have all complied with USPTO's duty of candor and disclosure for each
          of the United States patents and patent applications included in the
          Patents and Patent Applications.

     (7)  To our best knowledge, there is no information which forms a basis for
          a finding of unenforceability or invalidity of any of the claims of
          the Patents and Patent. Applications except for with regard to U.S.
          Patent No. 5,324,614; prior art uncovered after the '614 patent issued
          may be deemed to be such information either by itself or in
          combination with other information.

     (8)  There is no pending or, to our best knowledge, threatened action,
          suit, proceeding, or claim by others challenging the Company's or its
          Subsidiaries' ownership or license rights in or to any of the Owned
          Patent Rights or Licensed Patent Rights.


     (9)  There is no pending or, to our best knowledge, threatened action,
          suit, proceeding or claim by others challenging the validity or scope
          of any of the Owned Patent Rights or Licensed Patent Rights.

     (1O) There is no pending or, to our best knowledge, threatened action,
          suit, proceeding or claim by the Company or its Subsidiaries that a
          third party has or will infringe or otherwise violate any of the Owned
          Patent Rights or Licensed Patent Rights.


                                      E-41



SBC Warburg Dillon Read, Inc.
June 25, 1998
Page 4


     (11) There is no pending or, to our best knowledge, threatened action,
          suit, proceeding or claim by any third party that the Company or its
          Subsidiaries or their products and processes infringe or otherwise
          violate any patent, trademark, copyright, trade secret or other right
          of such third party.

     (12) To our best knowledge, the statements in the Memorandum under the
          captions "Risk Factors - Patents and Proprietary Rights" and
          "Executive Summary" and other references in the Memorandum to the
          Intellectual Property and other patent, trade secret, trademark and
          licensing matters, insofar as such statements constitute a summary of
          the legal matters, documents or proceedings referred to therein, are
          accurate in all material respects and fairly present the information
          purported to be disclosed therein.

     We have participated in conferences with officials and other
representatives of the Company, Company's counsel and others, at which
conferences the contents of the Memorandum and related matters were discussed,
and although we have not verified the accuracy or completeness of the statements
contained in the Memorandum, nothing has come to our attention which leads us to
believe that the Memorandum or exhibits thereto (other than the financial
statements including supporting schedules and other financial and statistical
information derived therefrom) contained any untrue statement of a material fact
or omitted to state a material fact necessary to make the statements therein not
misleading.


                                           Sincerely,


                                           ROBERTS & MERCANTI, L.L.P.

                                           /s/MICHAEL N. MERCANTI
                                           ----------------------
                                           Michael N. Mercanti

MNM/aap


                                      E-42



                                      DRAFT


                                           June 25, 1998



The Purchasers in the Enzon, Inc. 
     Common Stock
Purchase Agreement Dated June 25, 1998

and

SBC Warburg Dillon Read, Inc.
535 Madison Avenue
New York, New York 10022


Ladies and Gentlemen:

     Our client, Enzon, Inc., a Delaware corporation (the "Company"), has
requested that we furnish to you our opinion in respect of certain matters
relating to the Company's single chain antigen binding protein ("SCA")
technologies, and pursuant to Section 5.5 of the Common Stock Purchase
Agreement, dated June 25, 1998, between SBC Warburg Dillon Read, Inc. (the
"Placement Agent") and the Company (the "Placement Agent Agreement").
Capitalized terms not otherwise defined herein shall have the meaning ascribed
to them in the Purchase Agreement.

     For the purposes of rendering the opinions set forth below, we have either
reviewed the following in the course of preparing this opinion or else we have
reviewed the following in the course of our representation of the Company
(collectively the "Documents"):

     1.   the Purchase Agreement;


                                      E-43



The Purchasers in the Enzon, Inc. Common Stock
and SBC Warburg Dillon Read, Inc.
June 25, 1998
Page 2


     2.   that certain Private Placement Offering Memorandum (the "Memorandum")
          dated June 2, 1998, together with any and all exhibits and amendments
          thereto;

     3.   the patents and certain patent applications listed on Schedule 1
          attached hereto, which include all of the patents and patent
          applications referred to in the Memorandum (the "Patents and Patent
          Applications") with respect to the Company's SCA technologies and
          which are divided into category A, which are the patents and patent
          applications owned by the Company and the Company's subsidiaries
          listed on Schedule 2 attached hereto (the "Subsidiaries")
          (collectively, the "Owned Patent Rights") collectively, and within
          category B, the issued U.S. patents licensed by the Company and its
          Subsidiaries no pending applications were examined in category B
          (collectively, the "Licensed Patent Rights");

     4.   copies of the license agreements listed on Schedule 3 attached hereto
          (collectively, the "License Agreements");

     5.   copies of assignments relevant to ownership of the Patents and Patent
          applications;

     6.   the results of searches in the United States Patent and Trademark
          Office ("USPTO"), completed on June 25, 1998 in relation to the
          USPTO's record of title to the United States patents and patent
          applications within the Patents and Patent Applications;

     7.   any and all references cited to, or by, the USPTO during the
          prosecution of the United States patents and patent applications
          included within Owned Patent Rights of the Patents and Patent
          Applications;

     8.   the documents referred to in those opinions of this firm which we
          delivered to the Company relating to the Owned Patent Rights or
          relating to whether the SCA products or proposed products of the
          Company infringe patents belonging to any third parties;

     9.   the internal files of this firm pertaining to the Owned Patent Rights.

     Whenever our opinions herein are qualified by the phrase "to our best
knowledge," except as may be further qualified below, such language means that
based upon the Documents, the


                                      E-44



The Purchasers in the Enzon, Inc. Common Stock
and SBC Warburg Dillon Read, Inc.
June 25, 1998
Page 3


actual knowledge of attorneys within our firm (i.e., not including matters as to
which such attorneys could be deemed to have constructive knowledge) and
inquiries of officers, directors and employees of the Company, we believe that
such opinions are factually correct.

          (1) To our best knowledge, the Company and its Subsidiaries are the
     sole owners of the Owned Patent Rights and have obtained currently
     effective licenses to the Licensed Patent Rights pursuant to the License
     Agreements.

          (2) The Company and its Subsidiaries are listed in the records of the
     USPTO as the sole owners of the United Stated patents and patent
     applications within the Owned Patent Rights.

          (3) The Licensors are listed in the records of the USPTO as the sole
     owners of the United Stated patents within the Licensed Patent Rights. The
     undersigned can make no representation about the ownership of any pending
     patent applications of Licensors.

          (4) To our best knowledge, the Company and its Subsidiaries have good
     and marketable title to the Owned Patent Rights, free of any liens,
     pledges, claims, security interests or other encumbrances, but excluding
     those licenses set forth on Schedule 4.

          (5) To our best knowledge, there is no information which would
     preclude the grant of a patent from each of the patent applications within
     the Owned Patent Rights, it being understood that there can be no certainty
     as to which adjustments may be made to the claims as part of the
     prosecution process within the PTO. The undersigned can make no
     representation about the granting of any pending patent applications of
     third parties, such as Licensors.

          (6) To our best knowledge, the Company, and the Subsidiaries have all
     complied with USPTO's duty of candor and disclosure for each of the United
     Stated patents and patent applications included in the Owned Patent Rights.
     No representation can be made with respect to complying with the duty of
     candor by any Licensor.

          (7) To our best knowledge, there is no information which forms a basis
     for a finding of unenforceability or invalidity of any of the claims of the
     Owned Patent Rights.

          (8) There is no pending or, to our best knowledge, threatened action,
     suit, proceeding or claim by others challenging the Company's or its
     Subsidiaries' ownership or license rights in or to any of the Owned Patent
     Rights or Licensed Patent Rights.


                                      E-45



The Purchasers in the Enzon, Inc. Common Stock
and SBC Warburg Dillon Read, Inc.
June 25, 1998
Page 4


          (9) There is no pending or, to our best knowledge, threatened action,
     suit, proceeding or claim by others challenging the validity or scope of
     any of the Owned Patent Rights.

          (10) There is no pending or, to our best knowledge, threatened action,
     suit, proceeding or claim by the Company or its Subsidiaries that a third
     party has or will infringe or otherwise violate any of the Owned Patent
     Rights or Licensed Patent Rights. However, the Company is constantly
     evaluating the activity of third parties and intends to enforce its patent
     rights when necessary and appropriate.

          (11) There is no pending or, to our best knowledge, threatened action,
     suit, proceeding or claim by any third party that the Company or its
     Subsidiaries or their products and processes infringe or otherwise violate
     any patent, trademark, copyright, trade secret, or other right of such
     third party.

          (12) To our best knowledge, the statements in the Memorandum under the
     captions "Risk Factors - Patents and Proprietary Rights" and "Executive
     Summary" and other references in the Memorandum to the Intellectual
     Property and other patent, trade secret, trademark and licensing matters,
     insofar as such statements constitute a summary of the legal matters,
     documents or proceedings referred to therein, are accurate in all material
     respects and fairly present the information purported to be disclosed
     therein.

     We have participated in conferences with officials and other
representatives of the Company, Company's counsel and others, at which
conferences the contents of the Memorandum and related matters were discussed,
and although we have not verified the accuracy or completeness of the statements
contained in the Memorandum, nothing has come to our attention which leads us to
believe that the Memorandum or exhibits thereto (other than the financial
statements including supporting schedules and other financial and statistical
information derived therefrom) contained any untrue statement of a material fact
or omitted to state a material fact necessary to make the statements therein not
misleading.

                                   Very truly yours,

                                   STERNE, KESSLER, GOLDSTEIN & FOX P.L.L.C.

                                   DRAFT

                                   Jorge A. Goldstein


JAG/aye



                                      E-46



                                                                    Confidential


                       ENZON SCA(R) PROTEINS PATENT RIGHTS
                       -----------------------------------



                                                  DATE                                                   DATE
TITLE             INVENTOR         COUNTRY        FILED          SERIAL NO.          PATENT NO.          ISSUED
- -----             --------         -------        -----          ----------          ----------          ------
                                                                                       
Single            Ladner, Bird     US             09/02/86       06/902,971          Abandoned
Polypeptide                        US             09/02/87       07/902,110          Abandoned
Chain Molecules                    PCT            09/02/87       PCT/US87/02208
                                   EP             09/02/87       87906006.9          0281604             03/31/93
                                   Austria        09/02/87       87906006.9          0281604             03/31/93
                                   Belgium        09/02/87       87906006.9          0281604             03/31/93
                                   France         09/02/87       87906006.9          0281604             03/31/93
                                   Germany        09/02/87       87906006.9          0281604             03/31/93
                                   Italy          09/02/87       87906006.9          0281604             03/31/93
                                   Luxembourg     09/02/87       87906006.9          0281604             03/31/93
                                   Netherlands    09/02/87       87906006.9          0281604             03/31/93
                                   Sweden         09/02/87       87906006.9          0281604             03/31/93
                                   Switzerland    09/02/87       87906006.9          0281604             03/31/93
                                   U. Kingdom     09/02/87       87906006.9          0281604             03/31/93
                                   CA             09/04/87       546,164
                                   Japan          09/02/88       219589              Abandoned
                                   US             01/19/89       07/299,617          4,946,778           08/07/90
                                   US             04/25/90       07/512,910          5,260,203           11/09/93
                                   US             04/01/93       08/040,440          5,455,030           10/03/95
                                   US             06/06/95       08/468,988          5,518,889           05/21/96
                                   US             06/06/95       08/468,992          5,534,621           07/09/96

Computer Based    Ladner           US             09/02/86       06/902,970          4,704,692           11/03/87
System and                         PCT            09/02/87       PCT/US87/02211
Method for                         EP             09/02/87       87906007.7          Abandoned
Determining                        US             11/02/87       07/115,919          Abandoned
Possible                           US             06/09/88       07/204/940          4,881,175           Abandoned
Chemical
Structures

Organism          Ladner, Glick    US             03/02/87       07/021,046          Abandoned
Carrying a        Bird             PCT            03/02/88       PCT/US88/00716      
Single Chain                       EP             03/02/88       88903058.1          034978              11/30/94
Antibody                           France         03/02/88       88903058.1          034978              11/30/94
Domain                             Germany        03/02/88       88903058.1          034978              11/30/94
at its Surface                     U. Kingdom     03/02/88       88903058.1          034978              11/30/94
                                   US             07/30/89       07/373,702          Abandoned
                                   US             04/02/91       07/680,009          Abandoned
                                   US             11/04/91       07/802,631          Abandoned
                                   US             10/13/94       08/322,352          Abandoned

Incremental       Hardman          US             09/02/87       07/092,147          4,939,666           07/03/90
Macromolecule                      CA             09/01/88       576,286             Abandoned
Construction Method                JP             09/02/88       221223              Abandoned



                                      E-47



                                                                    Confidential


                       ENZON SCA(R) PROTEINS PATENT RIGHTS
                       -----------------------------------



                                                  DATE                                                   DATE
TITLE             INVENTOR         COUNTRY        FILED          SERIAL NO.          PATENT NO.          ISSUED
- -----             --------         -------        -----          ----------          ----------          ------
                                                                                       
                                   JP             11/20/92       510157              
Multivalent       Whitlow,         US             11/25/91       07/796,936          Abandoned
Antigen-          Wood             CA             11/20/92       2,122,732
Binding           Hardman          US             11/20/92       07/989,846          Abandoned
Proteins                           PCT            11/20/92       PCT/US92/09965
                                   EP             11/20/92       93900545.I
                                   US             02/22/95       08/392,338

Linkers for       Whitlow,         US             11/20/92       07/980,529          Abandoned
Linked fusion     Filpula          US             01/15/93       08/002,845          Abandoned
Polypeptides                       PCT            11/17/93       PCT/US93/11138      Abandoned
                                   US             04/07/94       08/224,591
                                   US             09/10/97       08/926,789

Antigen Binding   Whitlow,         US             10/13/94       08/232,445          5,763,733           06/09/98
Fusion Proteins   Filpula, Shorr   US             08/16/95       08/515,903
                                   PCT            10/13/95       PCT/US95/12840

Protein           Lee              US             04/07/95       08/417,855          5,656,730           08/12/97
Stabilized                         US             03/17/97       08/819,033
by Histidine

Production and    Filpula,         US             04/30/97       60/044,449          Abandoned
Uses of           Wang,            US             10/27/97       60/063,074
Glycosylated      Shorr,           US             12/02/97       60/067,341
Single Chain      Whitlow,         US             04/30/98       09/069,842
Fv Proteins       Lee              PCT            04/30/98

Polyalkylene      Shorr,           US             06/23/97       60/050,472
Glyco-Modified    Whitlow,         US             04/30/98       09/069,842
Single Chain      Filpula,         PCT            04/30/98       08654
Polypeptides      Lee



June 2, 1998
u:\sca.con


                                      E-48




                                   SCHEDULE 1B
                                   -----------


6/25/92              OIA Patent Applications/Issued Patents               Page 1

- --------------------------------------------------------------------------------
File No./                Docket No.          MSKCC Inventor(s)
Title of Disclosure      
- --------------------------------------------------------------------------------

SK 340                   25562               Lloyd et al

Monoclonal Antibodies to Human Gastrointestinal Cancer


Status of Disclosure: Abandoned for SK 340.1
- --------------------------------------------------------------------------------
Canada              Serial #: 507,097             Filing Date: 4/18/86
                    Patent #:                     Issue Date:
                    Status of Application:

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

PO         
         Serial #: 86104321.4          Filing Date: 3/27/86
                    Patent #:                     Issue Date:
                    Status of Application:

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

Japan               Serial #: 091154/86           Filing Date: 4/19/86
                    Patent #:                     Issue Date:
                    Status of Application:

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

U.S.                Serial #: 724,991             Filing Date: 4/19/85
                    Patent #:                     Issue Date:
                    Status of Application:        Abandoned for SK 340.1

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

SK 340.1                 25562-A             Lloyd et al

Monoclonal Antibodies to Human Gastrointestinal Cancer


Status of Disclosure: Abandoned for SK 340.2. Continuation of SK 340
- --------------------------------------------------------------------------------
U.S.                Serial #: 118,411             Filing Date: 11/06/87
                    Patent #:                     Issue Date:
                    Status of Application:        Abandoned for SK 340.2,
                                                  Continuation of SK 340
- --------------------------------------------------------------------------------


                                      E-49



6/25/92              OIA Patent Applications/Issued Patents               Page 2

- --------------------------------------------------------------------------------
File No./                Docket No.          MSKCC Inventor(s)
Title of Disclosure      
- --------------------------------------------------------------------------------

SK 340.2                 25562-B             Welt et al

Method of Imaging Colorectal Carcinoma Lesion and Composition for use
therein


Status of Disclosure: Active.  CIP of SK 340.1
- --------------------------------------------------------------------------------
U.S.                Serial #: 327,765             Filing Date: 3/23/89
                    Patent #:                     Issue Date:
                    Status of Application:        Abandoned for SK 340.3
                                                  and SK 340.4, CIP of SK
- --------------------------------------------------------------------------------


SK 340.3                 25562-C             Welt et al

Method of Imaging Colorectal Carcinoma Lesion and Composition for use
therein


Status of Disclosure: Active.  Continuation of SK 340.2
- --------------------------------------------------------------------------------
U.S.                Serial #: 673,155             Filing Date: 3/18/91
                    Patent #:                     Issue Date:
                    Status of Application:        Divisional of SK 340.2
                                                  Abandoned
- --------------------------------------------------------------------------------


SK 340.4                 25562-D             Welt et al

Method of Imaging Colorectal Carcinoma Lesion and Composition for use
therein


Status of Disclosure: Active.  Divisional of SK 340.2
- --------------------------------------------------------------------------------
U.S.                Serial #: 671,132             Filing Date: 3/18/91
                    Patent #:                     Issue Date:
                    Status of Application:        Divisional of SK 340.2 
                                                  U.S. Patent 5,160,723   
- --------------------------------------------------------------------------------

U.S.                Serial #: 020,223             
                    Patent #: 5,431,897                    
                    Status of Application:        U.S. Patent 5,432,897   
- --------------------------------------------------------------------------------

U.S.                Serial #: 312,633             
                    Patent #: 5,643,550                    
                    Status of Application:        U.S. Patent 5,643,550   
- --------------------------------------------------------------------------------


                                      E-50



                                  SCHEDULE 1B

                        PROTEIN ENGINEERING CORPORATION
                        -------------------------------

Title                    Inventor                Patent No.      Date Issued
- -----                    --------                ----------      -----------

Directed Evolution       Ladner, et. al.         5,223,409       06/29/93




                            AGEN BIOMEDICAL LIMITED
                            -----------------------

Title                    Country                 Serial No.
- -----                    -------                 ----------

Immunological Use        AU                      S0949/90
of Microwaves                                    (640634)
                         Int'l                   PCT/AU90/00040
                         CA                      2,046,621
                         EU                      90902980.3
                         US                      07/792,578



                            MOLECULAR ONCOLOGY, INC.

        U.S. Patent application Ser. No. 06/836,414; filed March 5, 1986



                                      E-51



                                  SCHEDULE 1B

                               XOMA PATENT RIGHTS


                                                             DATE
TITLE                   INVENTOR         COUNTRY             FILED          SERIAL NO.           PATENT NO.
- -----                   --------         -------             ------         ----------           ----------
                                                                                             
Modular Assembly        Robinson, Liu,   *United States      11/01/85       06/793,980     
of Antibody Genes,      Horwitz, Wall,   Australia           10/27/86       65981/86             606,320
Antibodies Prepared     Better           Austria             10/27/86       EP 86906676.1        0247091
Thereby and Use                          Belgium             10/27/86       EP 86906676.1        0247091
                                         Canada              10/31/86       521,909
                                         Denmark             10/27/86       3385/87
                                         Europe              10/27/86       EP 86906676.1        0247091
                                         Europe              10/27/86       92115754.1
                                         France              10/27/86       EP 86906676.1        0247091
                                         Germany             10/27/86       EP 86906676.1        0247091
                                         Italy               10/27/86       EP 86906676.1        0247091
                                         Japan               10/27/86       505887/86
                                         Luxembourg          10/27/86       EP 86906676.1        0247091
                                         Netherlands         10/27/86       EP 86906676.1        0247091
                                         PCT                 10/27/86       PCT/US88/02269
                                                                                                               (WO 87/02671)
                                         Sweden              10/27/86       EP 86906676.1        0247091
                                         Switzerland/
                                         Liechtenstein       10/27/86       EP 86906676.1        0247091
                                         Taiwan              11/27/86       75105650             51922
                                         United Kingdom      10/27/86       EP 86906676.1        0247091

Modular Assembly        Robinson, Liu,   Australia           07/25/88       23244/88             632462
of Antibody Genes,      Horwitz, Wall,   Austria             07/25/88       EP 88907510.7        0371998
Antibodies Prepared     Better           Belgium             07/25/88       EP 88907510.7        0371998
Thereby and Use                          Canada              07/24/88       572,398
                                         Denmark             07/25/88       0192/90
                                         Europe              07/25/88       EP 88907510.7        0371998
                                         Europe              07/25/88       EP 93100041.8

                                         France              07/25/88       EP 88907510.7        0371998
                                         Germany             07/25/88       EP 88907510.7        0371998
                                         Italy               07/25/88       EP 88907510.7        0371998
                                         Japan               07/24/88       506481/88
                                         Luxembourg          07/25/88       EP 88907510.7        0371998
                                         Netherlands         07/25/88       EP 88907510.7        0371998
                                         PCT                 07/25/88       PCT/US88/02514
                                                                                                               (WO 89/00999)
                                         Sweden              07/25/88       EP 88907510.7        0371998
                                         Switzerland/        
                                         Liechtenstein       07/25/88       EP 88907510.7        0371998
                                         United Kingdom      07/25/88       EP 88907510.7        0371998
                                         *United States      07/24/87       07/077,528
                                         United States       03/28/90       07/501,092
                                         United States       12/08/92       07/987,555
                                         United States       04/17/92       07/870,404
                                         United States       02/22/93       08/020,671
                                         United States       04/29/94       08/235,225
                                         United States       08/18/94       08/299,085
                                         United States       12/09/94       08/367,234

AraB Promoters          Lai, Lee, Lin    Austria             01/24/86       EP 86900983.7        0211047
and Method of           Ray, Wilcox      Belgium             01/24/86       EP 86900983.7        0211047
Producing                                Europe              01/24/86       EP 86900983.7        0211047
Polypeptides                             Finland             01/24/86       863891
Including                                France              01/24/86       EP 86900983.7        0211047
Cecropins by                             Germany             01/24/86       EP 86900983.7        0211047
Microbiological                          Italy               01/24/86       EP 86900983.7        0211047
Techniques                               Japan               01/24/86       500818/88
                                         Luxembourg          01/24/86       EP 86900983.7        0211047
                                         Netherlands         01/24/86       EP 86900983.7        0211047
                                         Norway              01/24/86       863808
                                         PCT                 01/24/86       PCT/US86/00131



                                      E-52





                                                                                             
                                                                                                               (WO 86/04356)
                                         Sweden              01/24/86       EP 86900983.7        0211047
                                         Switzerland/        
                                         Liechtenstein       01/24/86       EP 86900983.7        0211047
                                         United Kingdom      01/24/86       EP 86900983.7        0211047
                                         *United States      01/28/85       06/695,309
                                         *United States      11/13/85       06/797,472
                                         United States       02/05/90       07/474,304           5,028,530

Novel Plasmid           Lei, Wilcox      Australia           01/09/89       29377/89             627443
Vector With                              Canada              01/10/89       587,885
Pectate Lyase                            Europe              01/09/89       EP 89901763.6
Signal Sequence                          Japan               01/09/89       501661/89
                                         PCT                 01/09/89       PCT/US89/00077                     (WO 89/06283)

                                         *United States      01/11/88       07/142,089



                                      E-53



                                   SCHEDULE 2
                                   ----------

                                  Subsidiaries
                                  ------------



                                Enzon Labs, Inc.

                                  Symvex, Inc.

                                   Enzon GmbH


                                      E-54



                                   SCHEDULE 3
                                   ----------

                                IN-LICENSES - SCA
                                -----------------



                    Agen Biomedical Limited
                    Memorial Sloan Kettering
                    Protein Engineering Corporation
                    XOMA



                                      E-55



                                   SCHEDULE 4
                                   ----------

                               OUT-LICENSES - SCA
                               ------------------



                    Alexion Pharmaceuticals, Inc.
                    Baxter Healthcare Corporation
                    Bristol-Myers Squibb Corporation
                    Cambridge Antibody Technology Limited
                    Creative BioMolecules
                    Cell Genesys, Inc.
                    Cytoclonal Pharmaceutics, Inc.
                    Hybritech Incorporated
                    Invitrogen, Inc.
                    Neoprobe Corporation
                    PanVera Corporation
                    Pharmacia Biotech, Inc.
                    Pharmacia P-L Biochemicals, Inc.
                    Rhone Poulenc Rorer (Gencell)
                    Molecular Oncology, Inc. (MOI)
                    XOMA
                

                                      E-56


                                    Exhibit E

                     PURCHASER'S LEGEND REMOVAL CERTIFICATE

To:  [Transfer agent name and address]

     Attention: ______________

     The  undersigned,  the  Purchaser  or an officer  of, or other  person duly
authorized by the Purchaser, hereby certifies that _____________________________
                                                    (fill in name of Purchaser)
institution  was  the  Purchaser  of  the  Shares   evidenced  by  the  attached
certificate,  and in order to induce the Company to remove the legends contained
on the  certificates  representing the Common Stock purchased by such Purchaser,
Purchaser  will  sell  such  Shares  (i) in  accordance  with  the  registration
statement,  file number in which case the Purchaser will satisfy the requirement
of  delivering a current  prospectus  in  connection  with such sale, or (ii) in
accordance with Rule 144 under the Securities Act of 1933 ("Rule 144"), in which
case the Purchaser  certifies  that it has complied with or will comply with the
requirements of Rule 144. Print or type:

     Name of Purchaser:  _______________________________________________________

     Name of Individual
      representing
      Purchaser (if an
      Institution):      _______________________________________________________

     Title of Individual
      representing
      Purchaser (if an
      Institution):      _______________________________________________________

Signature by:

         Purchaser or
          Individual representing
          Purchaser:     _______________________________________________________




                                      E-57





                                    Exhibit F

                   PURCHASER'S CERTIFICATE OF SUBSEQUENT SALE

To:  [Transfer agent name and address]

     Attention: _____________

     The  undersigned,  the  Purchaser  or an officer  of, or other  person duly
authorized by the Purchaser, hereby certifies that _____________________________
                                                    (fill in name of Purchaser)
institution  was  the  Purchaser  of  the  Shares   evidenced  by  the  attached
certificate,  and  as  such,  proposes  to  transfer  such  Shares  on  or about
______________________ either (i) in accordance with the registration statement,
       (date)
file  number  _____________,  in which  case the  Purchaser  certifies  that the
requirement of delivering a current prospectus has been complied with or will be
complied with in connection  with such sale, or (ii) in accordance with Rule 144
under the  Securities  Act of 1933  ("Rule  144"),  in which case the  Purchaser
certifies that it has complied with or will comply with the requirements of Rule
144.

Print or type:

         Name of Purchaser:  ___________________________________________________

         Name of Individual
          representing
          Purchaser (if an
          Institution):      ___________________________________________________

         Title of Individual
          representing
          Purchaser (if an
          Institution):      ___________________________________________________

Signature by:



                                      E-58



                                    Exhibit G

                          DESCRIPTION OF CAPITAL STOCK




                                      E-59


                                    EXHIBIT G

                          Description of Capital Stock

     Under its Certificate of Incorporation,  the Company is authorized to issue
60,000,000  shares of Common  Stock,  par value  $.01 per share,  and  3,000,000
shares of preferred  stock,  par value $.01 per share. As of May 29, 1998, there
were  31,331,081  shares of Common Stock,  and 108,000 shares of preferred stock
designated  as Series A Preferred  Stock,  outstanding.  Other than the Series A
Preferred Stock, there are no other classes of preferred stock designated and no
other shares of preferred stock  outstanding.  Holders of shares of Common Stock
and Series A Preferred Stock are entitled to one vote per share on matters to be
voted upon by the  stockholders of the Company.  There are no cumulative  voting
rights and, accordingly,  the holders of a majority of the combined Common Stock
and Series A Preferred  Stock may elect all of the  directors.  The Common Stock
and the Series A Preferred  Stock  shall be voted as one class,  except (i) with
respect to any action  amending or  repealing  any of the powers,  designations,
preferences  and rights of the Series A  Preferred  Stock,  which  requires  the
affirmative  vote of holders of not less than two-thirds of the then outstanding
Series A  Preferred  Stock and (ii) with  respect  to any action  increasing  or
decreasing  the  authorized  shares  or the par  value  of the  Common  Stock or
preferred stock or altering or changing  adversely the powers,  preferences,  or
special  rights of such  shares,  which  pursuant to Section 242 of the Delaware
General  Corporation  Law  requires  the  affirmative  vote of a majority of the
outstanding  shares  of the class so being  affected,  voting as a class and the
affirmative  vote of a majority of the  combination  of the  outstanding  Common
Stock and Series A Preferred Stock, voting as one class.

Common Stock

     Holders of shares of Common  Stock will be  entitled  to receive  dividends
when,  as and if declared by the Board of Directors  and to share ratably in the
assets of the Company legally  available for distribution to its stockholders in
the event of the liquidation,  dissolution or winding up of the Company, in each
case  subject to the rights of the  holders  of the  Series A  Preferred  Stock.
Holders  of  Common  Stock  have  no  preemptive,  subscription,  redemption  or
conversion  rights. All of the issued and outstanding shares of Common Stock are
duly authorized, validly issued, fully-paid and non-assessable.

     The registrar and transfer agent for the Common Stock is Continental  Stock
Transfer and Trust Company, 2 Broadway, New York, New York 10004.

     The authorized but unissued  preferred  stock may be issued by the Board of
Directors from time to time in one or more series with such  preferences,  terms
and rights as the Board of Directors may determine without further action by the
stockholders of the Company.  Accordingly,  the Board of Directors has the power
to fix the dividend rate and to establish the  provisions,  if any,  relating to
voting  rights,



                                      E-60



redemption rates,  sinking fund,  liquidation  preferences and conversion rights
for any series of preferred stock issued in the future.

     It is not possible to state the actual effect of the  authorization  of the
preferred  stock upon the rights of holders of the Common  Stock until the Board
of Directors  determines  the specific  rights of the holders of a series of the
preferred  stock.  The  issuance of the  preferred  stock may have the effect of
delaying,  deferring or  preventing  a change in control of the Company  without
further action by the stockholders.

Series A Preferred Stock

     The  holders  of the Series A  Preferred  Stock are  entitled  to an annual
dividend of $2.00 per share, payable semi-annually but only when and if declared
by the Board of Directors out of funds legally available therefor.  Dividends on
the Series A  Preferred  Stock are  cumulative  and accrue  and  accumulate.  No
dividends are to be paid or set apart for payment on the Common  Stock,  nor are
any shares of Common  Stock to be redeemed,  retired or  otherwise  acquired for
valuable  consideration unless the Company has paid in full, or made appropriate
provision for the payment in full of, all dividends which have then  accumulated
on the Series A Preferred Stock.

     Since the Company did not make cash dividend payments for eight semi-annual
periods from the date of issuance of the Series A Preferred Stock, any holder of
Series A Preferred  Stock may elect,  upon written notice to the Company,  to be
paid all or any part of such  accrued and unpaid  dividends,  and any  dividends
which  accrue  but are not  paid in cash  within  thirty  days of the  scheduled
payment date thereafter,  in shares of the Company's  Common Stock.  Accrued and
unpaid  dividends  payable to holders of Series A Preferred Stock as of the date
such holder  elects to convert the Series A  Preferred  Stock into Common  Stock
may, at the Company's option, be paid by the Company's  issuance of Common Stock
to such holder. In all cases the number of shares of Common Stock to be received
in lieu of accrued  dividends  shall be  determined  by dividing  the  aggregate
amount of the accrued and unpaid  dividends by the conversion rate of the Series
A Preferred  Stock in effect on the date of election.  To date,  the Company has
paid no dividends on the Series A Preferred Stock,  except for accrued dividends
payable on Series A Preferred Stock which has been converted,  all of which have
been paid with Common Stock.  The Company does not presently  intend to pay cash
dividends on the Series A Preferred  Stock.  There were 1,733,000 of accrued and
unpaid dividends on the Series A Preferred Stock as of March 31, 1998. Dividends
on the Series A Preferred  Stock  currently  accrue at the rate of $216,000  per
year.

     Each share of Series A Preferred  Stock is convertible at any time prior to
redemption.  For purposes of conversion,  each share of Series A Preferred Stock
is deemed to have a value of $25.00. The Series A Preferred Stock is convertible
into  Common  Stock at a  conversion  rate of $11.00 per share of Common  Stock.
The 


                                      E-61



conversion rate will be adjusted upon the Company's  payment of dividends on its
Common Stock in Common  Stock,  the  subdivision  or reduction of the  Company's
outstanding Common Stock, the reclassification of the Common Stock or the merger
or consolidation of the Company,  provided,  however, that no such adjustment to
the conversion  rate will be made unless the net effect on the conversion  price
per share of all such events is at least $.50 in the aggregate.

     The Company  may at any time,  redeem the whole or any part of the Series A
Preferred Stock then outstanding at a redemption price of $25.00 per share, plus
in each case a sum equal to all accumulated and unpaid dividends thereon through
the date fixed for redemption.  In case of redemption of only part of the Series
A Preferred  Stock at any time  outstanding,  the Company  shall  designate  the
amount of Series A  Preferred  Stock so to be  redeemed  and shall  redeem  such
Series A Preferred  Stock on a pro rata basis.  Subject to certain  limitations,
the Board of Directors shall have the power and authority to prescribe the terms
and  conditions  upon which the Series A Preferred  Stock shall be redeemed from
time to time.

     In the event of any voluntary or  involuntary  liquidation,  dissolution or
winding  up of the  Company,  the  holders of Series A  Preferred  Stock will be
entitled  to  receive  in cash out of the assets of the  Company,  whether  from
capital or from earnings, available for distribution to its stockholders, before
any amount shall be paid to the holders of the Common  Stock,  the sum of $25.00
per share of Series A Preferred  Stock,  plus an amount equal to all accumulated
and  unpaid  dividends  thereon  through  the date  fixed  for  payment  of such
distributive amount.

     All shares of Common  Stock are of junior rank to Series A Preferred  Stock
in respect of the preferences as to dividends,  distributions  and payments upon
the  liquidation,  dissolution  or winding up of the Company.  The rights of the
holders of the Common Stock are subject to the  preferences  and relative rights
of the Series A Preferred  Stock. The Company may authorize and issue additional
or other  Preferred  Stock  which is of equal rank with the  Series A  Preferred
Stock in respect of the preferences as to dividends,  distributions and payments
upon the  liquidation,  dissolution  or  winding  up of the  Company;  provided,
however,  that for so long as any Series A Preferred Stock remains  outstanding,
the Company  shall not issue any capital stock which is more senior in rank than
the Series A Preferred  Stock in respect of the foregoing  preferences  or which
shall have greater voting rights than the Series A Preferred Stock. In the event
of a merger or  consolidation  of the Company with or into another  corporation,
the Series A Preferred  Stock shall maintain its relative  powers,  designations
and preferences.

Common Stock Purchase Warrants

     As of May 29,  1998 the  Company  had  outstanding  warrants to purchase an
aggregate of 1,038,686  shares of Common Stock at exercise  prices  ranging from
$2.50 to $ 5.63 per share.


                                      E-62



Options to Purchase Common Stock

     As of May 29,  1998 the  Company  had  outstanding  options to  purchase an
aggregate of 4,378,736  shares of Common Stock at exercise  prices  ranging from
$1.88 to $14.88 per share held by employees, directors and consultants under the
Company's Non-Qualified Stock Option Plan.

Independent Directors Stock Plan

     Under the terms of the Company's Independent Directors Stock Plan (approved
by stockholders in December 1996) each independent director is granted shares of
Common Stock equivalent to $2,500 per quarter, plus $500 for Board of Directors'
meeting attended.  The number of shares issued is based on the fair market value
of the Common Stock on the last trading day of the applicable quarter.

Registration Rights

     Schering  Corporation  has  piggyback  registration  rights with respect to
847,489  shares of Common Stock.  Such shares are eligible  under Rule 144(k) of
the Securities Act of 1933, as amended.



                                      E-63