Exhibit 10.1

                            STOCK EXCHANGE AGREEMENT




                                      among


                               CYTOGEN CORPORATION


                                       and


                        THE STOCKHOLDERS AND DEBTHOLDERS
                               OF PROSTAGEN, INC.



                            Dated as of June 15, 1999







                                Table of Contents


ARTICLE I SALE AND PURCHASE OF SHARES.........................................1
     Section 1.1. Closing.....................................................1
     Section 1.2. Deliveries by the Sellers...................................1
     Section 1.3. Deliveries by the Purchaser.................................1
     Section 1.4. Other Closing Matters.......................................2
     Section 1.5. Post Closing Adjustment.....................................2
     Section 1.6. Contingent Payments.........................................4
     Section 1.7. Cancellation................................................5

ARTICLE II REPRESENTATIONS AND WARRANTIES OF THE SELLERS......................5
     Section 2.1. Organization................................................5
     Section 2.2. Capitalization..............................................6
     Section 2.3. Binding Nature of this Agreement............................6
     Section 2.4. Consents and Approvals; No Violations.......................7
     Section 2.5. Financial Statements........................................7
     Section 2.6. Absence of Certain Changes..................................8
     Section 2.7. No Undisclosed Liabilities..................................8
     Section 2.8. Litigation..................................................9
     Section 2.9. No Default..................................................9
     Section 2.10.Permits; Compliance with Applicable Law.....................9
     Section 2.11.Taxes and Tax Returns.......................................9
     Section 2.12.Employee Benefit Plans.....................................13
     Section 2.13.Intellectual Property......................................15
     Section 2.14.Transactions with Affiliates...............................15
     Section 2.15.Contracts..................................................15
     Section 2.16.Labor Relations............................................16
     Section 2.17.Environmental..............................................16
     Section 2.18.Ownership of Assets........................................18
     Section 2.19.Insurance..................................................18
     Section 2.20.Real Property..............................................18
     Section 2.21.Share Ownership............................................19
     Section 2.22.Investment.................................................19
     Section 2.23.Accredited Investor........................................19
     Section 2.24.No Misleading Statements...................................20
     Section 2.25.No Exclusive Manufacturing Rights..........................20

ARTICLE III REPRESENTATIONS AND WARRANTIES OF THE PURCHASER .................20
     Section 3.1. Organization...............................................20
     Section 3.2. Capitalization.............................................20
     Section 3.3. Authority Relative to this Agreement.......................21
     Section 3.4. Consents and Approvals; No Violations......................21
     Section 3.5. SEC Reports; Financial Statements..........................22
     Section 3.6. Absence of Certain Changes.................................22


                                       ii

ARTICLE IV COVENANTS.........................................................22
     Section 4.1. Further Assurances.........................................23
     Section 4.2. Brokers or Finders.........................................23
     Section 4.3. Performance of Obligations.................................23
     Section 4.4. Tax Covenants..............................................23
     Section 4.5. Employees; Releases........................................23
     Section 4.6. NWB Board..................................................24
     Section 4.7. Lockup.....................................................24

ARTICLE V SURVIVAL; INDEMNIFICATION..........................................24
     Section 5.1. Survival Periods...........................................24
     Section 5.2. Indemnification............................................25
     Section 5.3. Indemnification Amounts....................................25
     Section 5.4. Claims.....................................................26
     Section 5.5. Indemnification with Respect to Taxes......................27
     Section 5.6. Exclusive Remedy...........................................28

ARTICLE VI MISCELLANEOUS.....................................................28
     Section 6.1. Notices....................................................28
     Section 6.2. Headings...................................................29
     Section 6.3. Counterparts...............................................29
     Section 6.4. Entire Agreement; Assignment...............................29
     Section 6.5. Governing Law..............................................29
     Section 6.6. Specific Performance.......................................30
     Section 6.7. Publicity..................................................30
     Section 6.8. Binding Nature; No Third Party Beneficiaries...............30
     Section 6.9. Severability...............................................30
     Section 6.10.Interpretation.............................................30
     Section 6.11.Payment of Expenses........................................30


                                    Exhibits

         Exhibit A:        Allocation
         Exhibit B:        Registration Rights Agreement


                                      iii


     STOCK  EXCHANGE  AGREEMENT,  dated  as  of  June  15,  1999  among  Cytogen
Corporation, a Delaware corporation (the "Purchaser"),  and the stockholders and
the  holders  of  certain  rights  to  receive  cash  (the  "Debtholders",  and,
collectively,  the "Sellers") of Prostagen,  Inc., a Delaware  corporation  (the
"Company").

     WHEREAS, the Purchaser has agreed to acquire from the stockholders, and the
stockholders have agreed to sell to the Purchaser, all of the outstanding shares
of common  stock,  par value  $0.001 per share,  of the  Company  (the  "Company
Shares"),  and the Debtholders  have agreed to cancel such debt, in each case in
exchange for shares of common  stock,  par value $.01 per share (the  "Purchaser
Shares"), of the Purchaser, on the terms and subject to the conditions set forth
herein.

     NOW, THEREFORE, the parties agree as follows:

                                   ARTICLE I
                           SALE AND PURCHASE OF SHARES

     Section 1.1. Closing. The closing of the transactions  contemplated by this
Agreement (the "Closing") is taking place  simultaneously  with the execution of
this  Agreement,  at the  offices of Dewey  Ballantine  LLP,  1301 Avenue of the
Americas,  New  York,  New  York.  The  date on  which  the  Closing  occurs  is
hereinafter referred to as the "Closing Date."

     Section 1.2. Deliveries by the Sellers.  At the Closing,  the Sellers shall
deliver or cause to be delivered to the Purchaser the following:

     (a) Certificates for all of the outstanding  Company Shares,  duly endorsed
in blank,  or  accompanied  by stock  powers duly  executed  in blank,  with any
necessary stock transfer tax stamps attached or provided for;

     (b) Cancelled  demand  promissory notes held by Max Link, S. Leslie Misrock
and CC Consulting A/S and a release to the Company of the funds held pursuant to
the escrow agreement in favor of Alan Fox;

     (c) a  certificate  of exemption  from  withholding  as provided in Section
1445(b) of the Code (as hereinafter  defined) and Treasury  Regulation  1.1445-2
(the "FIRPTA Certificate"); and

     (d) such other duly executed  documents and  certificates  as the Purchaser
may reasonably request.

     Section 1.3. Deliveries by the Purchaser.

     (a) At the Closing, or as promptly as practicable thereafter, but not later
than three  Nasdaq  trading days after the Closing  Date,  the  Purchaser  shall
deliver or cause to be  delivered  to the Sellers  certificates  representing  a


number of the  Purchaser  Shares equal to $2 million  divided by the  Conversion
Number. Such Purchaser Shares shall be allocated among the Sellers in accordance
with Exhibit A to this Agreement.

     (i) If the  Purchaser  Market  Value (as defined  below) is greater than or
equal to $1-1/32,  then the  Conversion  Number  shall be the  Purchaser  Market
Value.

     (ii) If the  Purchaser  Market  Value is less than $1-1/32 and greater than
$31/32, then the Conversion Number shall be $1.

     (iii) If the  Purchaser  Market  Value is less than or equal to $31/32  and
greater than $.50,  then the  Conversion  Number shall be the  Purchaser  Market
Value.

     (iv) If the Purchaser  Market Value is less than or equal to $.50, then the
Conversion Number shall be $.50.

     (v) The Purchaser Market Value shall equal the average of the closing price
of the Purchaser Shares, as reported by Nasdaq,  for the ten trading days ending
on the second trading day prior to the Closing Date.

     (b)  Notwithstanding  anything  in this  Section 1.3 to the  contrary,  the
Purchaser shall not be required to deliver any fractional  Purchaser  Shares. In
lieu  thereof,   amounts  delivered  under  this  Section  1.3  to  any  Company
shareholder shall be rounded to the nearest whole share.

     Section 1.4. Other Closing Matters.

     (a) The  management of Purchaser  shall  consider the election of S. Leslie
Misrock and Alan Fox to the Purchaser's Board of Directors.

     (b) At  the  Closing,  the  Purchaser  and  S.  Leslie  Misrock,  Esq.,  as
representative  for  the  Sellers  (the  "Representative"),  shall  execute  the
Registration Rights Agreement in the form of Exhibit B hereto. The Sellers,  and
each of them,  irrevocably appoint the Representative as their  attorney-in-fact
to act for them and in their name in  connection  with all  matters  relating to
this Stock Exchange Agreement and the Registration Rights Agreement.

     Section  1.5.  Post  Closing  Adjustment.  (a) If the Closing Date Cash (as
defined  below) is less than  $550,000,  the Sellers shall pay the difference to
the Purchaser.  If the Closing Date Liabilities (as defined below) are more than
$25,000,  the Sellers  shall pay the  difference to the  Purchaser.  Any payment
shall be  accompanied  by interest  on such amount from the Closing  Date to the
date of payment at a floating rate equal to the publicly announced prime lending
rate of Citibank,  N.A. Any payment by the Sellers  under this Section 1.5 shall
be paid in the Purchaser Shares valued at the Conversion Number.


                                       2


     (b) As promptly as practicable  following the Closing Date, but in no event
more than 45 days  following the Closing Date,  the Purchaser  shall prepare and
deliver to the  Representative  a  consolidated  balance sheet setting forth the
total assets and total liabilities of the Company and its subsidiaries as of the
Closing Date (the "Closing Date Balance  Sheet"),  in accordance with clause (f)
below.  The  Representative  and his accountants will be entitled to observe the
preparation  of the  Closing  Date  Balance  Sheet  and  shall be  granted  such
information and access as they may reasonably request in connection therewith.

     (c) Unless  within 20 days after its  receipt of the Closing  Date  Balance
Sheet, the Representative  shall deliver to the Purchaser a statement describing
its objections  thereto,  the amounts  determined in accordance  with clause (b)
shall be final and binding for purposes of this Section 1.5.

     (d) If the Representative shall deliver the statement referred to in clause
(c) above, the  Representative  and the Purchaser will use reasonable efforts to
resolve any disputes,  but if a final  resolution is not reached  within 20 days
after the  Representative  has submitted its objections,  any remaining disputes
will be resolved by the Reviewing  Accountants.  The Reviewing Accountants shall
be instructed to resolve any matters in dispute as promptly as practicable.  The
determination  of the  Reviewing  Accountants  will be  final  and  binding  for
purposes of this Section 1.5.

     (e) The  Purchaser,  on the one hand,  and the Sellers,  on the other hand,
shall each pay  one-half of the fees and expenses of the  Reviewing  Accountants
and  shall  cooperate,   including  by  furnishing  any  information  reasonably
requested,  with each other and such  accounting  firm in the  resolution of any
disputes.  The Sellers  shall  satisfy  such  obligation  to pay one-half of the
Reviewing  Accountant's  fees and  expenses  by causing  the  Representative  to
deliver to the  Purchaser a number of Purchaser  Shares  (rounded to the nearest
whole share) equal to the Seller's  portion of such fees and expenses divided by
the Conversion Number.

     (f)  "Closing  Date  Cash"  will be  equal to (i) the  total  cash and cash
equivalents less (ii) the total current  liabilities,  in each case set forth on
the Closing  Date Balance  Sheet  finally  determined  in  accordance  with this
Section 1.5.  "Closing Date Liabilities " will be equal to the total liabilities
(other than current  liabilities)  set forth on the Closing  Date Balance  Sheet
finally determined in accordance with this Section 1.5, plus the total amount of
all other liabilities (other than current liabilities  reflected on such balance
sheet,  and other than contingent  liabilities).  The Closing Date Balance Sheet
shall  be  prepared  in  accordance  with  U.S.  generally  accepted  accounting
principles ("GAAP") applied on a basis consistent with the accounting principles
used in preparation of the audited balance sheets delivered  pursuant to Section
2.5 hereof and in all  respects as if the Closing  Date were the end of a fiscal
year.  The Closing Date  Balance  Sheet need not include any  information  which
would not affect the  calculation  of the Closing  Date Cash or the Closing Date
Liabilities.


                                       3


     Section 1.6. Contingent Payments.

     (a) The Purchaser shall deliver to the Representative a number of Purchaser
Shares equal to $2 million  divided by the Conversion  Number  (recomputed as of
the date of payment) on the earlier of (x) five days  following  the filing of a
New Drug  Application or Biologic License  Application,  as the case may be, for
dendritic cell therapy by Northwest Biotherapeutics, Inc. ("NWB") or (y) January
1, 2002.

     (b) The Purchaser shall deliver to the Representative a number of Purchaser
Shares equal to $2 million  divided by the Conversion  Number  (recomputed as of
the date of payment) on the earlier of (x) five days following the  demonstrated
efficacy of immunotherapy (vaccine or radioimmunotherapy) at the end of Phase II
clinical  trials,  as  evidenced  solely by  commencement  of Phase III clinical
trials or (y) January 1, 2004.

     (c)  Notwithstanding  the  foregoing,  (1) no  payment  shall be made under
clause (a)(x) of this Section 1.6 unless at the  scheduled  time of such payment
the dendritic  cell therapy  program is  continuing  and (2) no payment shall be
made under clause (a)(y) or of this Section 1.6 unless at the scheduled  time of
such payment the dendritic  cell therapy  program is  continuing  and safety has
been demonstrated in clinical trials.

     (d)  Notwithstanding  the  foregoing,  (1) no  payment  shall be made under
clause (b)(x) of this Section 1.6 unless at the  scheduled  time of such payment
the immunotherapy (vaccine or radioimmunotherapy)  program is continuing and (2)
no payment  shall be made under clause  (b)(y) of this Section 1.6 unless at the
scheduled time of such payment the immunotherapy (vaccine or radioimmunotherapy)
program is continuing and safety has been demonstrated in clinical trials.

     (e) On the date the  payment  contemplated  by Section  1.6(b) is due,  the
Purchaser shall deliver to the Representative a number of Purchaser Shares equal
to  $500,000  divided  by the  Conversion  Number at such time as the  exclusive
manufacturing  right relating to Prostate  Specific  Membrane  Antigen  ("PSMA")
granted to Northwest  Clinicals  LLC ("NWC")  shall have been  cancelled or made
non-exclusive.  Any amount  payable  pursuant to this  Section  1.6(e)  shall be
decreased  by (x) any  amounts  paid,  payable or which  would be payable to any
third party,  including NWC, in connection with any such manufacturing  right or
the  cancellation  thereof and (y) with respect to arrangements  between NWB, on
the one hand, and the Purchaser or the Company, or both, on the other hand, that
are made  with the  approval  of S.  Leslie  Misrock,  such  approval  not to be
unreasonably  withheld,  the excess,  if any,  of the net  present  value of the
royalty  payments  under the  license  agreement  between  the  Company  and the
Purchaser  relating to PSMA over the net present  value of the royalty  payments
under the sublicense relating to such license,  between the Company and NWB (net
present  value to be  calculated  using the  publicly  announced  prime  rate of
Citibank, N.A.).

     (f) On or before the date which is six months  from the Closing  Date,  the
Purchaser  shall pay, as set forth in this Section  1.6(f),  an amount,  if any,
equal to (i) $450,000  divided by the Conversion  Number less (ii) the amount of

                                       4

Unsettled  Liabilities.  Unsettled  Liabilities  shall  mean any  amounts  paid,
payable or which  would be payable by the Company in respect of the lease on the
Company's office and other space in Allandale,  New Jersey.  In order to prevent
any  double-counting,  amounts  paid by the  Sellers  pursuant  to  Section  1.5
attributable  to the matters  covered by this  Section  1.6(e)  shall reduce the
amount of the Unsettled  Liabilities  on a  dollar-for-dollar  basis.  The first
$60,000 of such payment, if any, shall be paid in cash to S. Leslie Misrock. The
balance,  if any,  of such  payment  shall  be  paid  to the  Representative  in
Purchaser Shares valued at the Conversion Number.

     (g) It is  understood  that  certain  persons  who are not  parties to this
Agreement  will be entitled to payments  under this Section 1.6, as set forth in
Exhibit A. In order to prevent  any  double-counting,  any  payments  under this
Section 1.6 shall be reduced by such payments.

     Section  1.7.  Cancellation.  Effective  as of  immediately  prior  to  the
Closing,  all rights of the  Sellers (or any  affiliates)  under (a) any option,
warrant or right to acquire  any  securities  of the  Company and (b) any notes,
bonds, indentures or other evidences of indebtedness, are hereby cancelled, with
no  further  obligations  of  the  Company,   the  Purchaser  or  any  affiliate
thereunder.

                                   ARTICLE II
                  REPRESENTATIONS AND WARRANTIES OF THE SELLERS

     The  Sellers  severally  and  not  jointly  represent  and  warrant  to the
Purchaser  as  follows,  except as set forth in the  disclosure  schedule  being
delivered by the Sellers to the Purchaser concurrently herewith (the "Disclosure
Schedule"):

     Section 2.1.  Organization.  Each of the Company and its  subsidiaries is a
corporation duly organized, validly existing and in good standing under the laws
of the jurisdiction of its  organization  and has all requisite  corporate power
and authority and all necessary governmental approvals to own, lease and operate
its properties  and assets and to carry on its business as now being  conducted,
except where the failure to be so organized, existing and in good standing or to
have such power, authority, and governmental approvals would not have a Material
Adverse  Effect on the  Company.  As used  herein  with  respect  to an  entity,
"Material  Adverse  Effect"  shall  mean  an  event,  change  or  effect  which,
individually or together with all other events,  changes or effects, has had, or
is  reasonably  likely to have,  a  material  adverse  effect  on the  financial
condition, assets, liabilities, results of operations or business of that entity
and its subsidiaries  taken as a whole. The Company and each of its subsidiaries
is duly  qualified  or  licensed  to do  business  and in good  standing in each
jurisdiction in which the property owned, leased or operated by it or the nature
of the business conducted by it makes such qualification or licensing necessary,
except  where  the  failure  to be so duly  qualified  or  licensed  and in good
standing  would  not in the  aggregate  have a  Material  Adverse  Effect on the
Company.  The Company has delivered to the Purchaser true and complete copies of
its and its  subsidiaries  certificate of incorporation  and bylaws,  or similar
organizational  documents.  Notwithstanding anything herein to the contrary, NWC

                                       5

shall not be considered a subsidiary of the Company.  S. Leslie Misrock does not
have  knowledge  that  were NWC a  subsidiary  of the  Company,  that any of the
representations  and  warranties  herein,  if made by the Company with regard to
NWC, would be untrue.

     Section  2.2.  Capitalization.  (a) The  authorized  capital  stock  of the
Company consists of 12,000,000  Shares and no preferred  shares.  As of the date
hereof  3,850,000  Shares  are  issued  and  outstanding.  On the  date  hereof,
1,250,000  of such  Shares  are being  contributed  to the  Company.  All of the
outstanding  shares of the Company's capital stock are duly authorized,  validly
issued,  fully paid and non-assessable.  Except as set forth above (i) there are
no shares of capital stock of the Company authorized,  issued or outstanding and
(ii) there are no options, warrants, calls, pre-emptive rights, subscriptions or
other rights, agreements, arrangements or commitments of any character, relating
to  the  issued  or  unissued  capital  stock  of  the  Company  or  any  of its
subsidiaries,  obligating  the  Company  or any of its  subsidiaries  to  issue,
transfer  or sell or cause to be  issued,  transferred  or sold  any  shares  of
capital  stock  of, or other  equity  interest  in,  the  Company  or any of its
subsidiaries or securities  convertible  into or exchangeable for such shares or
equity interests, or obligating the Company or any of its subsidiaries to grant,
extend or enter  into any such  option,  warrant,  call,  subscription  or other
right,  agreement,  arrangement or commitment and (iii) there are no outstanding
obligations of the Company or any of its  subsidiaries to vote or to repurchase,
redeem or otherwise  acquire any shares of capital stock of the Company,  or any
subsidiary  or  affiliate  of the  Company  or to  provide  funds  to  make  any
investment  (in the form of a loan,  capital  contribution  or otherwise) in any
subsidiary or any other entity.  Other than Shares, no securities of the Company
have the right to vote.

     (b) The Company has delivered to the Purchaser true and complete  copies of
all instruments  governing or defining rights under the Shares.  The Company has
delivered a true and complete  list of all holders of securities of the Company.
All such securities were issued in compliance with all applicable law, including
federal and state securities laws.

     (c) All of the outstanding shares of capital stock of each of the Company's
subsidiaries  are owned by the  Company,  directly or  indirectly,  and all such
shares have been validly issued and are fully paid and nonassessable and free of
preemptive rights and are owned by either the Company or one of its subsidiaries
free and clear of all liens, charges,  claims or encumbrances.  The Company owns
___  shares  of common  stock of NWB,  free and  clear of any  liens,  claims or
encumbrances.  The Sellers have delivered to the Purchaser a certificate setting
forth the number of shares of NWB common stock outstanding as of the date hereof
on a fully diluted basis. The Company does not, directly or indirectly, have any
equity or ownership interest in any other business, other than its subsidiaries.

     Section 2.3.  Binding  Nature of this  Agreement.  (a) Such Seller has full
power and authority to execute and deliver this  Agreement and to consummate the
transactions  contemplated  hereby.  This  Agreement  has been duly executed and

                                       6

delivered by such Seller and is a valid and binding  obligation  of such Seller,
enforceable against such Seller in accordance with its terms.

     (b) The Board of Directors of the Company has taken all necessary action to
approve this Agreement and the transactions  contemplated hereby for purposes of
Section 203 of the  Delaware  General  Corporation  Law and the  certificate  of
incorporation and bylaws of the Company.

     Section 2.4. Consents and Approvals; No Violations.  Neither the execution,
delivery or performance of this Agreement by the Sellers nor the consummation by
the  Sellers  of the  transactions  contemplated  hereby nor  compliance  by the
Sellers or the Company with any of the provisions  hereof will (i) conflict with
or result in any breach of any provision of the certificate of  incorporation or
the bylaws (or similar  organizational  instrument)  of the Company or of any of
its  subsidiaries,  (ii)  require  any filing  with,  or permit,  authorization,
consent or approval of, any court, tribunal, administrative agency or commission
or other  governmental or other regulatory  authority or agency (a "Governmental
Entity") or any other  person or entity,  (iii)  result in a violation or breach
of,  or  constitute  (with or  without  due  notice  or lapse of time or both) a
default (or give rise to any right of  termination,  amendment,  cancellation or
acceleration),  result  in the  termination  of or a  right  of  termination  or
cancellation of,  modification of any benefit under,  accelerate the performance
required  by,  result  in  the  triggering  of any  payment  or  other  material
obligation  pursuant to, result in the creation of any lien,  security interest,
charge or encumbrance  upon any of the material  properties of the Sellers,  the
Company or its subsidiaries under, or result in being declared void, voidable or
without further binding effect any of the terms, conditions or provisions of any
note, bond, mortgage, indenture, lease, license, contract, permit, deed of trust
agreement or other instrument or commitment obligation to which the Sellers, the
Company or any of its  subsidiaries is a party or by which any of them or any of
their  properties  or assets may be bound or affected or (iv) violate any order,
writ, injunction, decree, statute, rule or regulation applicable to the Sellers,
the  Company,  any of its  subsidiaries  or any of their  properties  or assets,
excluding  from the  foregoing  clauses  (ii),  (iii) and (iv) such  violations,
breaches or defaults which would not, in the aggregate,  have a Material Adverse
Effect.

     Section 2.5. Financial  Statements.  Section 2.5 of the Disclosure Schedule
sets forth the consolidated balance sheets,  income statements and statements of
cash flow of the Company and its consolidated  subsidiaries at and for the years
ended December 31, 1997 and 1998 and the three month period ended March 31, 1999
(collectively,   the  "Financial  Statements").   Each  of  the  balance  sheets
(including  the related  notes)  included  in the  Financial  Statements  fairly
presents in all material respects the financial  position of the Company and its
consolidated  subsidiaries  as of the  respective  dates thereof and each of the
statements of income and cash flow (including the related notes) included in the
Financial  Statements  fairly  presents in all material  respects the results of
operations of the Company and its  consolidated  subsidiaries for the respective
periods then ended, except as otherwise noted therein.  The consolidated balance
sheet of the Company and its  consolidated  subsidiaries as of March 31, 1999 is
sometimes  referred  to as the  "Company  Balance  Sheet"  and such  date as the
"Balance Sheet Date." Each of the Financial  Statements has been (i) prepared in

                                       7

accordance with GAAP consistently applied during the periods involved, except as
otherwise  noted  therein  and (ii)  prepared in  accordance  with the books and
records of the  Company.  The Company  maintains  adequate  books and records in
accordance with GAAP.

     Section 2.6. Absence of Certain Changes.  Since the Balance Sheet Date, (a)
each of the Company and its  subsidiaries has operated in the ordinary and usual
course of business,  (b) there have not occurred any events,  changes or effects
which have had or which could  reasonably  be likely to have a Material  Adverse
Effect,  and,  neither  the Company nor any of its  subsidiaries  has taken,  or
agreed to take, any action to:

     (i)  amend  its  Certificate  of   Incorporation   or  By-laws  or  similar
organizational documents, or alter through merger, liquidation,  reorganization,
restructuring or in any other fashion,  the corporate  structure or ownership of
the Company or any subsidiary;

     (ii) (A) declare,  set aside or pay any dividend or other distribution with
respect to its capital stock, (B) redeem, purchase or otherwise acquire directly
or indirectly any of its  securities,  (C) issue,  sell,  pledge,  dispose of or
encumber any securities (or any rights to acquire such securities) or (D) split,
combine or reclassify its outstanding capital stock;

     (iii)  acquire  or agree to  acquire,  any assets or  securities  either by
purchase, merger or otherwise;

     (iv) transfer,  lease,  license,  sell,  mortgage,  pledge,  dispose of, or
encumber  any  assets or  securities,  or  authorize,  propose  or  announce  an
intention to authorize or propose,  or enter into an agreement  with respect to,
any merger,  consolidation or business  combination or license or sublicense any
Intellectual  Property or otherwise dispose of any Intellectual  Property or any
interest therein;

     (v) modify,  amend or terminate any of its material contracts or engagement
with any third party, or waive, release or assign any material rights or claims,
or modify or amend the terms of any outstanding securities;

     (vi) make (or permit to be made) any Tax  election or settle or  compromise
any liability for taxes; or

     (vii) enter into an agreement,  contract,  commitment or  arrangement to do
any of the  foregoing,  or to  authorize,  recommend,  propose  or  announce  an
intention to do any of the foregoing.

     Section 2.7. No Undisclosed Liabilities.  There are no liabilities,  debts,
obligations  or claims  (absolute,  contingent,  known,  unknown  or  otherwise)
against the Company or its subsidiaries,  except liabilities, debts, obligations
or claims (a)  reflected or reserved in Company  Balance Sheet or (b) which were

                                       8

incurred  after the Balance Sheet Date in the ordinary  course of business.  For
purposes of this  Agreement,  incurred in the  ordinary  course of business  (or
similar  formulations) shall mean (x) in accordance with the terms of a contract
listed in Section 2.7(x) of the Company Disclosure Schedule or (y) comparable in
nature and  magnitude to those  payments made in the prior year, as evidenced by
the general ledger delivered to the Purchaser prior to the date hereof.

     Section 2.8.  Litigation.  There is no suit, claim,  action,  proceeding or
investigation  pending or, to the best  knowledge  of the Company or any Seller,
threatened  against  the  Company  or any  of its  subsidiaries  that  would  be
reasonably  likely  to have a  Material  Adverse  Effect,  and there is no basis
therefor,  and neither the Company nor any of its subsidiaries is subject to any
outstanding order, writ, injunction or decree that would be reasonably likely to
have a  Material  Adverse  Effect or that  restricts  the  Company or any of its
subsidiaries in any material respect.

     Section 2.9. No Default. There exists no default or violation (and no event
has  occurred  which with notice or lapse of time would  constitute a default or
violation or loss of material  benefits) of any term,  condition or provision of
(i) any note, bond, mortgage,  indenture,  contract, agreement, permit, license,
lease,  purchase  order,  sales  order,   arrangement  or  other  commitment  or
obligation  to which the Company or any  subsidiary is a party or may be subject
or (ii) any order, writ, injunction, decree, statute, treaty, rule or regulation
applicable to the Company or any  subsidiary,  except for violations or defaults
which would not have a Material Adverse Effect.

     Section 2.10. Permits; Compliance with Applicable Law. (a) To the knowledge
of the  Company  or any  Seller,  the  Company  does not  require  any  permits,
licenses,  variances,  exemptions,  orders,  approvals or  authorizations of any
Governmental Entity to conduct the business of the Company and its subsidiaries,
as presently conducted,  in a lawful manner, other than those that it possesses.
All such permits have been legally obtained and maintained and are in full force
and effect.

     (b) To the  knowledge  of the  Company or any Seller,  the  business of the
Company and its  subsidiaries is being and has been conducted in compliance with
all permits, orders, writs, judgments,  injunctions, decrees and settlements and
all applicable laws, ordinances,  codes, rules,  regulations and policies of any
Governmental Entity.

     Section 2.11. Taxes and Tax Returns.

     (a) Definitions:

     "Code" means the Internal  Revenue Code of 1986, as amended.  All citations
to  provisions  of  the  Code,  or  to  the  Treasury  Regulations   promulgated
thereunder, shall include any amendments thereto and any substitute or successor
provisions thereto.

     "Taxes"  means  any  and all  federal,  state,  local  and  foreign  taxes,
assessments and other  governmental  charges,  duties,  impositions,  levies and

                                       9

liabilities,  including,  without  limitation,  taxes  based upon or measured by
gross receipts,  income, profits, sales, use and occupation, and value added, ad
valorem,   transfer,   gains,  franchise,   withholding,   payroll,   recapture,
employment, excise, unemployment,  insurance, social security, business license,
occupation,  business  organization,  stamp,  environmental  and property taxes,
together with all interest, penalties and additions imposed with respect to such
amounts.  For purposes of this Agreement,  "Taxes" also includes any obligations
under any  agreements  or  arrangements  with any  person  with  respect  to the
liability for, or sharing of, Taxes (including, without limitation,  pursuant to
Treas. Reg. ss. 1.1502-6 or comparable provisions of state, local or foreign Tax
law) and including,  without limitation, any liability for Taxes as a transferee
or successor, by contract or otherwise.

     "Taxable Period" means any taxable year or any other period that is treated
as a taxable year (or other  period,  or portion  thereof,  in the case of a Tax
imposed with respect to such period or portion  thereof,  e.g., a quarter)  with
respect to which any Tax may be imposed under any applicable  statute,  rule, or
regulation.

     "Tax Reserve" shall have the meaning set forth in Section 2.11(c).

     "Tax  Return"  means  any  report,  return,  election,   notice,  estimate,
declaration,  information  statement and other forms and  documents  (including,
without  limitation,  all  schedules,  exhibits and other  attachments  thereto)
relating  to and  filed or  required  to be filed  with a  taxing  authority  in
connection with any Taxes (including, without limitation, estimated Taxes).

     (b) All Tax Returns  required to be filed by or with respect to the Company
or any of its  subsidiaries  for all Taxable Periods have been timely filed. All
such Tax Returns (i) were  prepared in the manner  required by  applicable  law,
(ii) are true,  correct  and  complete  in all  respects,  and (iii)  accurately
reflect the liability for Taxes of the Company and each of its subsidiaries. All
Taxes shown to be payable on such Tax Returns,  and all  assessments of Tax made
against the Company or any of its subsidiaries with respect to such Tax Returns,
have been paid when due. No adjustment  relating to any such Tax Return has been
proposed or threatened  formally or  informally  by any taxing  authority and no
basis exists for any such adjustment.


     (c) The Company and each of its subsidiaries have (i) timely paid or caused
to be paid all Taxes that are or were due,  whether or not shown (or required to
be shown) on a Tax Return and (ii) provided a sufficient reserve for the payment
of all Taxes not yet due and payable  (without regard to deferred Tax assets and
liabilities)  (the "Tax  Reserve") on the Financial  Statements  for the Taxable
Period ended  December 31, 1998 There are no Taxes that would be due if asserted
by a taxing authority,  except with respect to which the Company and each of its
subsidiaries are maintaining adequate reserves.

     (d) The Company and each of its  subsidiaries  have complied (and until the
Closing Date will comply) in all material  respects  with the  provisions of the
Code  relating  to the  withholding  and  payment of Taxes,  including,  without


                                       10

limitation,  the withholding and reporting requirements under Code sections 1441
through  1464,  3401 through  3406,  and 6041 through  6049,  as well as similar
provisions  under any other  laws,  and have,  within the time and in the manner
prescribed  by law,  withheld  from  employee  wages and paid over to the proper
governmental authorities all amounts required.

     (e) To the knowledge of the Company or any Seller,  none of the Tax Returns
of the  Company  or any of its  subsidiaries  has  been  or is  currently  being
examined by the Internal Revenue Service (the "IRS") or relevant state, local or
foreign taxing authorities. To the knowledge of the Company or any Seller, there
are no examinations or other  administrative  or court  proceedings  relating to
Taxes in  progress or  pending,  nor has the Company or any of its  subsidiaries
received a revenue agent's or similar report asserting a Tax deficiency.

     (f) To the  knowledge of the Company or any Seller,  no material  claim has
ever been made in writing by any taxing authority with respect to the Company or
any  of its  subsidiaries  in a  jurisdiction  where  the  Company  or any  such
subsidiary  does not file Tax Returns that the Company or any such subsidiary is
or may be  subject  to  taxation  by that  jurisdiction.  There are no  security
interests  on any of the assets of the Company or any of its  subsidiaries  that
arose in connection with any failure (or alleged  failure) to pay any Taxes and,
except for liens for real and personal  property  Taxes that are not yet due and
payable,  there are no liens for any Tax upon any asset of the Company or any of
its subsidiaries.

     (g) The Company and each of its  subsidiaries  have made  available (or, in
the case of Tax Returns filed after the date hereof, will make available at such
time and place as  Purchaser  may  request) to  Purchaser  complete and accurate
copies of such Tax Returns, and amendments thereto,  filed by the Company and/or
its  subsidiaries  as Purchaser  may request.  Since the date of the most recent
Financial Statement, neither the Company nor any subsidiary thereof has incurred
any  liability  for Taxes that would  result in a material  decrease  in the net
worth of the Company or any such subsidiary.

     (h)  Neither the Company  nor any of its  subsidiaries  is, or has been,  a
party to any  agreement  relating  to  allocating  or sharing the payment of, or
liability for, Taxes with respect to any Taxable Period.

     (i) Neither the Company nor any of its  subsidiaries  has  distributed  the
stock of any corporation in a transaction satisfying the requirements of Section
355 of the Code since April 16,  1997.  The stock of neither the Company nor any
of its  subsidiaries  has  been  distributed  in a  transaction  satisfying  the
requirements of Section 355 of the Code since April 16, 1997.

     (j) There is no  contract,  agreement,  plan or  arrangement  covering  any
person  that,  individually  or  collectively,  could give rise to, nor will the
consummation of the transactions contemplated hereby obligate the Company or any
of its  subsidiaries  or Purchaser to make, the payment of any amount that would
not be deductible by the Company or any of its subsidiaries by reason of Section
280G of the Code.


                                       11


     (k)  Neither  the  Company nor any of its  subsidiaries  has  executed  any
outstanding  waivers or comparable  consents  regarding the  application  of the
statute of limitations with respect to any Taxes or Tax Returns. No extension of
time with respect to any date on which a Tax Return was or is to be filed by the
Company or any of its  subsidiaries is in force.  Neither the Company nor any of
its  subsidiaries  has granted a power of attorney to any person with respect to
any Taxable Period.

     (l) All options to acquire stock of the Company or any of its  subsidiaries
granted  under any  stock  option  plan of the  Company  or any such  subsidiary
qualify under  Section  162(m)(4) of the Code as an exception  from  "applicable
employer  remuneration,"  and as such,  no  deduction of the Company or any such
subsidiary  relating to such options  would be  disallowed  by reason of Section
162(m) of the Code.

     (m) The Company is the common  parent of an  affiliated  group  (within the
meaning of Code section  1504(a)) that files a consolidated  U.S. federal income
tax return and includes the  corporations  listed as  "subsidiaries"  in Section
2.2(b) of the Disclosure Schedule.

     (n) Neither the Company nor any of its  subsidiaries  owns an interest in a
partnership or could be treated as a partner in a partnership  for U.S.  federal
income tax purposes.

     (o) Neither the Company nor any of its subsidiaries has been a member of an
(i)  affiliated  group  (within the meaning of Section 1504 of the Code) or (ii)
affiliated, combined,  consolidated,  unitary, or similar group for state, local
or foreign Tax purposes, other than the group of which the Company is the common
parent.

     (p) There are no outstanding options, warrants, securities convertible into
stock, or other contractual obligations that might be treated for federal income
tax  purposes as stock or another  equity  interest in the Company or any of its
subsidiaries.

     (q)  Neither  the  Company  nor any of its  subsidiaries  has  agreed or is
required to include in income any  adjustment  under  either  Section  481(a) or
Section 482 of the Code (or an analogous  provision of state,  local, or foreign
law) by reason of a change in accounting method or otherwise.

     (r) To the  knowledge  of the Company or any Seller,  there are no proposed
reassessments of any property owned by the Company or any of its subsidiaries or
other  proposals  that could increase the amount of any Tax to which the Company
or any of its subsidiaries could be subject.

     (s) Neither the Company nor any of its subsidiaries has any deferred income
reportable  for a period ending after the Closing Date but that is  attributable
to a transaction  (e.g., an installment  sale) occurring in, or resulting from a
change of  accounting  method  for, a period  ending on or prior to the  Closing
Date.


                                       12

     (t) None of the  indebtedness  of the  Company  or any of its  subsidiaries
constitutes "corporate  acquisition  indebtedness" (as defined in Section 279(b)
of the Code) or other indebtedness with respect to which any interest deductions
may be disallowed under Section 279 of the Code or otherwise.

     (u) Neither the Company nor any of its  subsidiaries has an overall foreign
loss within the meaning of Section 904 of the Code.  Neither the Company nor any
of its subsidiaries has consented to have provisions of Section 341(f)(2) of the
Code applied to it. Neither the Company nor any of its subsidiaries  has, during
the five-year period ending on the Closing Date, been a personal holding company
within the meaning of Section 541 of the Code.

     Section 2.12. Employee Benefit Plans.

     (a)  Section  2.12 of the  Company  Disclosure  Schedule  sets  forth  each
material  pension,   retirement,   profit  sharing,   medical,  dental,  health,
disability, life, death benefit, group insurance,  deferred compensation,  stock
option,  stock purchase,  restricted stock,  bonus or incentive,  severance pay,
employment or  termination,  and other employee  benefit or  compensation  plan,
trust,  arrangement,  contract,  agreement,  policy  or  commitment,  including,
without  limitation,  each "employee benefit plan" as defined in Section 3(3) of
the  Employee  Retirement  Income  Security  Act of 1974,  as amended  ("ERISA")
whether  formal or  informal,  written or oral under which (i) current or former
employees,  directors or  independent  contractors  of the Company or any of its
subsidiaries  participate  or are  entitled  to  participate  by reason of their
relationship  with the  Company  or any of its  subsidiaries,  (ii) to which the
Company or any of its  subsidiaries  is a party or a sponsor thereof or by which
the Company or any of its  subsidiaries is currently bound or (iii) with respect
to which the  Company  or any of its  subsidiaries  has any  obligation  to make
payments or contributions, (the "Benefit Plans").

     (b) Each Benefit Plan has at all times been  operated and  administered  in
compliance in all material respects with its terms, the applicable  requirements
of ERISA and the Code and all other  applicable  laws,  ach Benefit Plan that is
intended to be tax  qualified  under  Section  401(a) of the Code has received a
favorable  determination letter from the IRS stating that it is so qualified and
that any trust  associated  with such Benefit  Plan is tax exempt under  Section
501(a) of the Code, and, to the knowledge of the Company or any Seller, there is
no reason why the  qualified  status of any such  Benefit Plan or trust would be
denied or revoked, whether retroactively or prospectively.

     (c)  No  pending  or,  to  the  knowledge  of the  Company  or any  Seller,
threatened disputes,  lawsuits, claims (other than routine claims for benefits),
investigations,  audits or  complaints  to, or by,  any  person or  governmental
entity have been filed or are pending with  respect to the Benefit  Plans or the
Company or any of its  Subsidiaries  in connection  with any Benefit Plan or the
fiduciaries or administrators  thereof (other than routine claims for benefits).
With  respect to each Benefit  Plan,  there has not  occurred,  and no person or
entity  is  contractually  bound  to  enter  into,  any  nonexempt   "prohibited


                                       13

transaction"  within the  meaning of Section  4975 of the Code or Section 406 of
ERISA,  nor any  transaction  that would result in a civil penalty being imposed
under  Section  409 or  502(i) of  ERISA,  except  as would not have a  Material
Adverse Effect.

     (d)  Neither  the  Company,  its  Subsidiaries,  nor any trade or  business
(whether or not  incorporated)  which,  together  with the Company or any of its
Subsidiaries, would be deemed a "single employer" under Section 4001(b) of ERISA
(an  "ERISA  Affiliate")  has or at any time  within the  applicable  statute of
limitations  period has had (i) any  liability,  contingent or otherwise,  under
Title IV of ERISA or Section 412 of the Code,  (ii) an  obligation to contribute
to any "multiemployer plan" (as defined in Section 3(37) of ERISA).

     (e) All material contributions or payments made or deemed to have been made
with  respect  to each  Benefit  Plan  that  is a  deferred  compensation  plan,
including any pension  plan,  are  presently,  and have been during the years to
which they relate,  fully deductible pursuant to Section 404 of the Code and are
not  presently,  and have  never been  during  the years to which  they  relate,
subject to any material  excise tax under Section 4972 of the Code. All material
contributions  to and payments  with respect to or under the Benefit  Plans that
are required to be made with respect to periods  ending on or before the Closing
Date have been made or accrued  before the  Closing  Date by the  Company in all
material  respects in accordance with the appropriate plan documents,  financial
statement,  actuarial  report,  collective  bargaining  agreements  or insurance
contracts or arrangements.

     (f) No  Benefit  Plan that is an  "employee  welfare  benefit  plan"  under
Section 3(1) of ERISA (a "Welfare  Plan") is partially or fully funded through a
trust.  No Welfare  Plan  providing  medical or death  benefits  (whether or not
insured)  with respect to current or former  employees of the Company  continues
such coverage or provides such benefits beyond their date of retirement or other
termination  of service  (other than coverage  mandated by Section 601 of ERISA,
the  cost  of  which  is  fully  paid  by  the  former  employee  or  his or her
dependents).

     (g) With respect to each Benefit  Plan,  the Company has made  available to
Purchaser complete and correct copies of the following documents,  to the extent
in each case that such documents  exist or are required by law: (1) current plan
documents,  subsequent  plan  amendments,  or any and all other  documents  that
establish or describe the existence of the plan, trust,  arrangement,  contract,
policy or commitment;  (2) the most recent tax qualified  determination letters,
if any,  received from or  applications  pending with the IRS; and (3) the three
most recent Form 5500 Annual Reports,  including  related  schedules and audited
and  financial   statements  and  opinions  of  independent   certified   public
accountants.

     (h) The execution of, and performance of the transactions  contemplated in,
this  Agreement  will not (either alone or upon the occurrence of any additional
or subsequent events) constitute an event under any plan, policy, arrangement or

                                       14

agreement  or any trust or loan that will or would  reasonably  be  expected  to
result  in any  material  payment  (whether  of  severance  pay  or  otherwise),
acceleration   of,   forgiveness  of  indebtedness   owing  from,   vesting  of,
distribution of, or increase in or obligation to fund, any benefits with respect
to any current or former employee, director or consultant of the Company.

     Section  2.13.  Intellectual  Property.  Set forth in  Section  2.13 of the
Company  Disclosure  Schedule  is a  list  (the  "Listed  Intellectual  Property
Rights") of certain U.S.  and foreign,  registered  and  unregistered,  patents,
patent   applications,    trademarks,   trade   names,   copyrights,   copyright
registrations,   technology  (including  software),   trade  secrets,  know-how,
inventions,   data,   processes   and   other   intellectual   property   rights
(collectively,  "Intellectual  Property Rights") used by the Company.  No claims
are  pending  or, to the  Company's  or S. Leslie  Misrock's  actual  knowledge,
threatened,  by any person as to the use of any Intellectual  Property Rights or
infringement  of the rights of others by the Company or any  subsidiary  and, to
the actual  knowledge  of the Company or any Seller,  the use by the Company and
its  subsidiaries  of all  Intellectual  Property  Rights and the conduct of the
Company's business does not infringe on the rights of any person and there is no
basis for any such claim.  To the actual  knowledge  of the Company or S. Leslie
Misrock,  no third  person is  infringing  on the Listed  Intellectual  Property
Rights. The Company and its subsidiaries have not taken any action to impair any
Listed  Intellectual  Property  Rights,  including  by  granting  any  licenses,
sublicenses,  liens  or  encumbrances.  The  Company  has not  entered  into any
agreement to indemnify any other person  against any charge of  infringement  of
any third party intellectual property right. All employees,  agents, consultants
or  contractors  who have  contributed  to or  participated  in the  creation or
development of any  Intellectual  Property Rights on behalf of the Company,  its
subsidiaries or any predecessor in interest thereto either:  (i) is a party to a
"work-for-hire"  agreement  under  which the Company  and its  subsidiaries  are
deemed to be the original  owner/author  of all property  rights therein or (ii)
has executed an assignment or any agreement to assign in favor of the Company or
its subsidiaries (or such predecessor in interest,  as applicable) of all right,
title and interest in such material. Listed Intellectual Property Rights include
the NWB License, the NWB/NWC License and the Velos License.

     Section 2.14.  Transactions with Affiliates.  No present or former officer,
director,  stockholder or other affiliate of the Company has (i) any interest in
the  assets,  properties  or rights  used in the  business of the Company or its
subsidiaries  (other than  solely  through the  ownership  of Shares),  (ii) any
contract,  arrangement,  agreement  or  understanding  with the  Company  or its
subsidiaries  (iii)  engaged  in any  transactions  with the  Company  since the
Balance Sheet Date.

     Section 2.15. Contracts.

     (i)  Section  2.15 of the  Disclosure  Schedule  sets forth a complete  and
accurate list of each of the contracts to which the Company or any subsidiary is
a party or is bound.


                                       15

     (b)  Each  such  contract  or  agreement  is  legal,  valid,   binding  and
enforceable against the Company or its subsidiaries, and to the knowledge of the
Company or any Seller,  against each other party  thereto,  is in full force and
effect and will continue to be so legal, valid, binding, enforceable and in full
force and effect  following the Closing.  Neither the Company or the  applicable
subsidiary,  nor to the knowledge of the Company or any Seller, any other party,
is in breach or default,  and no event has occurred which would constitute (with
or without notice or lapse of time or both) a breach or default (or give rise to
any  right  of  termination,  modification,  cancellation  or  acceleration)  or
modification of benefits under any such contract.

     (c) The Company has delivered or made available for review by the Purchaser
true and complete  copies of each such contract or agreement.  Since the Balance
Sheet Date,  there has been no material  modification,  breach or termination of
any such contract or agreement.

     Section  2.16.  Labor  Relations.  (a) There is no unfair  labor  practice,
charge or complaint or other proceeding pending or, to the best knowledge of the
Company or any Seller, threatened,  against the Company or any subsidiary before
the National Labor Relations Board or any other Governmental Entity.

     (b) There is no labor strike,  slowdown or stoppage pending or, to the best
knowledge of the Company or any Seller,  threatened,  against or  affecting  the
Company or any subsidiary,  nor has there been any such activity within the past
two years.

     (c) There are no pending collective bargaining negotiations relating to the
employees of the Company or any subsidiary.

     (d) (i) there are no agreements with, or pending  petitions for recognition
of, a labor union or  association as the exclusive  bargaining  agent for any or
all of the employees of the Company or any  subsidiary,  (ii) no such  petitions
have been pending  within the past five years and (iii) to the best knowledge of
the  Company  or any  Seller,  there has not been any  general  solicitation  of
representation  cards by any union  seeking to  represent  the  employees of the
Company or any subsidiary as their exclusive bargaining agent at any time within
the past five years.

     Section  2.17.  Environmental.  (a)  Except to the  extent  that any of the
following  would not be reasonably  likely to have a Material  Adverse Effect on
the  Company:  (i) the Company and its  subsidiaries  comply  (which  compliance
includes, without limitation, the possession by the Company and its subsidiaries
of all permits and other  government  authorizations  required under  applicable
Environmental Laws, and compliance with the terms and conditions thereof) and at
all times have  complied  with all  applicable  Environmental  Laws (as  defined
below),  (ii) no Hazardous  Substances  (as defined below) are present at any of
the  properties  currently  owned,  leased,  operated or  otherwise  used by the
Company or its  subsidiaries  (including  soils,  ground water,  surface  water,
buildings or other structures), (iii) no Hazardous Substances have been disposed
on or released or discharged from, onto or under any of the properties currently

                                       16

owned,  leased,  operated or otherwise  used by the Company or its  subsidiaries
(including soils,  ground water,  surface water,  buildings or other structures)
during the period of  ownership,  lease,  operation or use by the Company or any
subsidiary  or, to the actual  knowledge  of the Company or any  Seller,  at any
other time, (iv) none of the Company or its subsidiaries disposed of or released
or discharged Hazardous Substances from, onto or under or adjacent to any of the
properties  (including soils,  ground water,  surface water,  buildings or other
structures) formerly owned, leased, operated or otherwise used by the Company or
any subsidiary,  and to the actual  knowledge of the Company and any Seller,  no
Hazardous Substances were present at or disposed on or released or discharged by
any  other  person  or  entity  from,  onto or under or  adjacent  to any of the
properties  (including soils,  ground water,  surface water,  buildings or other
structures) formerly owned, leased, operated or otherwise used by the Company or
any subsidiary  during the period of ownership,  lease,  operation or use by the
Company  or any  subsidiary,  (v) none of the  Company or its  subsidiaries  are
subject to any liability or obligation in connection  with Hazardous  Substances
present at any location owned,  leased,  operated or otherwise used by any third
party,  (vi) none of the Company or its subsidiaries or, to the actual knowledge
of the Company or any Seller,  any person or entity  whose  liability  under any
Environmental  Law the  Company  has or may  have  retained  or  assumed  either
contractually or by operation of law, has received any notice,  demand,  letter,
claim  or  request  for  information  alleging  that  any  of the  Company,  its
subsidiaries  or, to the actual  knowledge  of the  Company or any  Seller,  any
person or entity whose liability under any  Environmental Law the Company has or
may have retained or assumed either  contractually or by operation of law, is or
may be in violation of or liable under any Environmental  Law, (vii) none of the
Company or its subsidiaries is subject to any order, decree, injunction or other
directive  of  any  governmental  authority  and  none  of  the  Company  or its
subsidiaries  is subject to any indemnity or other  agreement with any person or
entity relating to Hazardous Substances and (viii) there are no circumstances or
conditions  involving  any of  Company  and its  subsidiaries  or, to the actual
knowledge of the Company or any Seller,  any assets (including real property) or
businesses  previously owned,  leased,  operated or otherwise used by Company or
any  subsidiary  or any assets  (including  real  property) or businesses of any
predecessors of the Company or any subsidiary that would  reasonably be expected
to result in any  damages to the  Company  or any  subsidiary  arising  under or
pursuant to  Environmental  Law or in any  restriction on the ownership,  use or
transfer of any of the assets of the Company or its  subsidiaries  arising under
or pursuant to any Environmental Law.

                                       17

     (b) As used herein, the term  "Environmental  Law" means any international,
national,  provincial,   regional,  federal,  state,  municipal  or  local  law,
regulation, order, judgement, decree, permit, authorization,  opinion, common or
decisional  law  (including,  without  limitation,  principles of negligence and
strict   liability)   or  agency   requirement   relating  to  the   protection,
investigation or restoration of the environment (including,  without limitation,
natural  resources) or the health or safety of human or other living  organisms,
including,  without  limitation,  the manufacture,  introduction  into commerce,
export, import, handling, use, presence, disposal, release or threatened release
of any  Hazardous  Substance  or  noise  pollution,  odor  pollution,  wetlands,
pollution, or contamination.

     (c) As used  herein,  the term  "Hazardous  Substance"  means any  element,
compound,  substance or other material  (including  any pollutant,  contaminant,
hazardous waste,  hazardous substance,  chemical substance,  or product) that is
listed,  classified or regulated pursuant to any Environmental  Law,  including,
without  limitation,  any petroleum product,  by-product or additive,  asbestos,
presumed  asbestos-containing  material,  asbestos-containing  material, medical
waste,    biological   waste,    chloroflourocarbon,    hydrochloroflourocarbon,
lead-containing  paint  or  plumbing,   polychlorinated  biphenyls,  radioactive
material or radon.

     Section 2.18. Ownership of Assets. The assets, properties and rights of the
Company and its subsidiaries  are held by the Company or its  subsidiaries  free
and clear of any liens,  claims or  encumbrances,  other than  Permitted  Liens.
"Permitted  Liens" means (i) liens for current  taxes not yet due and payable or
(ii) mechanics', carriers', workers' and other similar liens arising or incurred
in the ordinary course of business, which, individually or in the aggregate, are
not  substantial  in  amount,  do not  materially  detract  from the value of or
materially  interfere with the present use of any of the assets subject  thereto
or  materially  impair  the  conduct  of the  business  of the  Company  and its
subsidiaries.

     Section  2.19.  Insurance.  The  insurance  policies of the Company and its
subsidiaries are current, are in full force and effect, all premiums due thereon
have been paid,  and the  Company  and its  subsidiaries  have  complied  in all
material  respects with the provisions of such  policies,  and all such policies
either  specifically  include the Company as a named insured or include  omnibus
named insured  language which generally  includes the Company.  No proceeding is
pending or, to the best knowledge of the Company or any Seller,  threatened,  to
revoke,  cancel or limit such policies and no notice of  cancellation  of any of
such  policies has been received by the Company or any  subsidiary.  Each of the
Company and its  subsidiaries is in compliance with all warranties  contained in
all insurance policies.

     Section 2.20. Real Property.  Each of the Company and its subsidiaries have
good and  marketable  title to, or a valid  leasehold  interest in, all of their
real  properties,  and,  other than the  properties in which they hold leasehold
interests,  own  such  properties  free  and  clear  of all  liens,  claims  and
encumbrances,  other than Permitted  Liens. All real property owned or leased by
the  Company  or any  subsidiary  is set forth on  Section  2.20 of the  Company

                                       18

Disclosure Schedule. The Company and its subsidiaries are in compliance with the
terms of all  leases to which  they are a party and all such  leases are in full
force and effect.

     Section 2.21.  Share  Ownership.  Such Seller owns the number of Shares set
forth  opposite  such  Seller's  name on Exhibit A, free and clear of all liens,
claims and  encumbrances,  including any restrictions on or sharing of rights to
vote or dispose of such shares. Such Shares are the only equity interests in the
Company or any  subsidiary  beneficially  owned by such Seller.  No other person
beneficially  owns any equity  interest in the Company or any  subsidiary of the
Company or has any right to acquire or vote any such equity interest.

     Section 2.22. Investment. Such Seller is acquiring the Purchaser Shares for
investment and not with a view toward,  or for sale in connection with, any sale
or distribution  thereof.  Such Seller agrees that neither the Purchaser  Shares
nor  any  interest  therein  may  be  offered,   sold,   transferred,   pledged,
hypothecated  or  otherwise  disposed  of except  pursuant  to (i) an  effective
registration  statement  under  the  Securities  Act  and any  applicable  state
securities laws or (ii) an exemption from the  registration  requirements of the
Securities Act and any applicable  state  securities  laws, such exemption to be
evidenced  by  such  documentation  as the  Purchaser  may  reasonably  request,
including an opinion of counsel  (which  counsel and opinion shall be reasonably
satisfactory  to the  Purchaser)  that such  transfer is not in violation of the
Securities Act and any applicable  state laws. The Sellers  understand  that the
certificates  to be issued to the  Sellers  hereunder  will be  subject  to stop
transfer instructions and bear a legend substantially as follows:

     "The security  represented by this  certificate was issued in a transaction
which was not registered under the Securities Act of 1933 or the securities laws
of any state and neither the security  nor any interest  therein may be offered,
sold,  transferred,  pledged,  hypothecated  or  otherwise  disposed  of  except
pursuant to (i) an effective registration statement under the Securities Act and
any applicable  state securities laws or (ii) an exemption from the registration
requirements  of the Securities Act and any applicable  state  securities  laws,
such  exemption  to be  evidenced  by  such  documentation  as  the  issuer  may
reasonably  request,  including an opinion of counsel (which counsel and opinion
shall be  reasonably  satisfactory  to the issuer) that such  transfer is not in
violation of the Securities Act and any applicable state laws."

     Section 2.23. Accredited Investor.  Such Seller is an "accredited investor"
within the meaning of Rule 501 under the  Securities  Act,  provided that in the
case  of the  Seller  identified  in  Section  2.23  of the  Company  Disclosure
Schedule,  such  Seller has such  knowledge  and  experience  in  financial  and
business  matters that he is capable of  evaluating  the merits and risks of the
transactions  contemplated hereby,  including an investment in Purchaser Shares.
Such Seller has been given an adequate  opportunity to investigate the Purchaser
and has been  given  access to all  information  he deems  appropriate.  Without
limiting the  generality of the  foregoing,  such Seller  acknowledges  that the
Purchaser  has  furnished  (or made  available  to) such Seller the  Purchaser's

                                       19


Annual Report on Form 10-K for the year ended  December 31, 1998 and all filings
under  the  Exchange  Act or  the  Securities  Act  since  such  date,  a  brief
description of the Purchaser  Shares,  any material  changes in the  Purchaser's
affairs not disclosed in such documents and adequate  information  regarding the
Purchaser and the transactions  contemplated  hereby,  in each case a reasonable
time prior to the date hereof.

     Section 2.24. No Misleading Statements.  The representations and warranties
made by the Sellers in or pursuant to this  Agreement  do not include any untrue
statement of a material fact or omit to state any material fact.

     Section  2.25.  No  Exclusive  Manufacturing  Rights.  The  Company has not
granted  exclusive  manufacturing  rights to any person or entity with regard to
any immunotherapy technologies, except for the NWC License.


                                  ARTICLE III
                 REPRESENTATIONS AND WARRANTIES OF THE PURCHASER

     The Purchaser  represents  and warrants as of the date hereof and as of the
Closing  Date to the Sellers as follows,  except as set forth in the  disclosure
schedule being delivered by the Purchaser to the Sellers  concurrently  herewith
(the "Purchaser Disclosure Schedule"):

     Section 3.1. Organization.  Each of the Purchaser and its subsidiaries is a
corporation duly organized, validly existing and in good standing under the laws
of the jurisdiction of its  organization  and has all requisite  corporate power
and authority and all necessary governmental approvals to own, lease and operate
its properties and to carry on its business as now being conducted, except where
the failure to be so  organized,  existing and in good  standing or to have such
power,  authority,  and governmental approvals would not have a Material Adverse
Effect on the  Purchaser.  The  Purchaser and each of its  subsidiaries  is duly
qualified or licensed to do business and in good  standing in each  jurisdiction
in which the  property  owned,  leased or  operated  by it or the  nature of the
business conducted by it makes such qualification or licensing necessary, except
where the failure to be so duly qualified or licensed and in good standing would
not in the aggregate have a Material Adverse Effect on the Purchaser.

     Section  3.2.  Capitalization.  (a) The  authorized  capital  stock  of the
Purchaser  consists  of  89,600,000  Purchaser  Shares and  5,400,000  preferred
shares.  As of May  31,  1999,  65,122,000  Purchaser  Shares  were  issued  and
outstanding  and an  aggregate  of 8,128,464  Shares were  issuable  pursuant to
outstanding  options,  warrants or convertible notes. All the outstanding shares
of the Purchaser's  capital stock are, and all the Purchaser Shares which may be
issued  pursuant to the exercise of  outstanding  options to purchase  Purchaser
Shares will be, when issued in accordance  with the  respective  terms  thereof,
duly authorized,  validly issued,  fully paid and non-assessable.  Except as set
forth above and in the  Purchaser's  filings  with the  Securities  and Exchange
Commission pursuant to the Securities Exchange Act of 1934 (the "Exchange Act"),

                                       20

(i) there are no shares of capital stock of the Purchaser authorized,  issued or
outstanding and (ii) there are no options,  warrants, calls, pre-emptive rights,
subscriptions  or other rights,  agreements,  arrangements or commitments of any
character,  relating to the issued or unissued capital stock of the Purchaser or
any of its subsidiaries,  obligating the Purchaser or any of its subsidiaries to
issue, transfer or sell or cause to be issued, transferred or sold any shares of
capital  stock of, or other  equity  interest  in, the  Purchaser  or any of its
subsidiaries or securities  convertible  into or exchangeable for such shares or
equity  interests,  or obligating  the Purchaser or any of its  subsidiaries  to
grant,  extend or enter into any such option,  warrant,  call,  subscription  or
other  right,  agreement,  arrangement  or  commitment  and  (iii)  there are no
outstanding  obligations of the Purchaser or any of its  subsidiaries to vote or
to  repurchase,  redeem or otherwise  acquire any shares of capital stock of the
Purchaser,  or any  subsidiary or affiliate of the Purchaser or to provide funds
to  make  any  investment  (in  the  form of a  loan,  capital  contribution  or
otherwise)  in any  subsidiary  or any other  entity.  Other than the  Purchaser
Shares, no securities of the Purchaser have the right to vote. The Purchaser has
delivered to the Company true and complete copies of all  instruments  governing
or defining rights under the Purchaser Shares.

     (b) The Purchaser  Shares to be issued  pursuant to Section 1.3 hereof have
been duly  authorized  and, upon  issuance in accordance  with the terms hereof,
shall be validly issued, fully paid and nonassessable.

     Section 3.3. Authority  Relative to this Agreement.  The Purchaser has full
corporate  power and  authority  to execute and deliver  this  Agreement  and to
consummate the transactions  contemplated  hereby. The execution and delivery by
the Purchaser of this Agreement,  and the consummation by it of the transactions
contemplated  hereby,  have been  duly and  validly  authorized  by its Board of
Directors  and no  other  corporate  action  on the  part  of the  Purchaser  is
necessary  to authorize  the  execution  and  delivery by the  Purchaser of this
Agreement and the  consummation by it of the transactions  contemplated  hereby.
This  Agreement  has been duly  executed and delivered by the Purchaser and is a
valid and binding obligation of the Purchaser, enforceable against the Purchaser
in accordance with its terms.

     Section 3.4. Consents and Approvals; No Violations.  Neither the execution,
delivery or performance of this Agreement by the Purchaser nor the  consummation
by the Purchaser of the transactions  contemplated  hereby nor compliance by the
Purchaser with any of the provisions  hereof will (i) conflict with or result in
any breach of any provision of the  certificate of  incorporation  or the bylaws
(or  similar  organizational  instrument)  of  the  Purchaser  or of  any of its
subsidiaries, (ii) require any filing with, or permit, authorization, consent or
approval of, any Governmental Entity or any other person or entity, (iii) result
in a violation or breach of, or constitute  (with or without due notice or lapse
of time or both) a default (or give rise to any right of termination, amendment,
cancellation  or  acceleration),  result  in the  termination  of or a right  of
termination or cancellation  of,  modification of any benefit under,  accelerate
the  performance  required by, result in the  triggering of any payment or other
material  obligation  pursuant to, result in the creation of any lien,  security
interest,  charge or  encumbrance  upon any of the  material  properties  of the
Purchaser or its subsidiaries  under, or result in being declared void, voidable

                                       21

or without further binding effect any of the terms,  conditions or provisions of
any note, bond, mortgage,  indenture,  lease, license, contract, permit, deed of
trust  agreement  or other  instrument  or  commitment  obligation  to which the
Purchaser or any of its  subsidiaries  is a party or by which any of them or any
of their  properties  or assets may be bound or  affected  or (iv)  violate  any
order, writ, injunction,  decree,  statute, rule or regulation applicable to the
Purchaser,  any  of its  subsidiaries  or any of  their  properties  or  assets,
excluding  from the  foregoing  clauses  (ii),  (iii) and (iv) such  violations,
breaches or defaults which would not, in the aggregate,  have a Material Adverse
Effect on the Purchaser.

     Section 3.5. SEC Reports; Financial Statements.

     (a) The  Purchaser  has filed with the SEC all forms,  reports,  schedules,
statements and other documents  required to be filed by it since January 1, 1996
(collectively,  the "Purchaser SEC  Documents").  As of the date of filing,  the
Purchaser SEC  Documents  (a) do not contain any untrue  statement of a material
fact or omit to state a material fact required to be stated therein or necessary
in order to make the statements  therein,  in light of the  circumstances  under
which they were made, not  misleading and (b) complied in all material  respects
with the applicable  requirements of the Exchange Act and the Securities Act, as
the case may be, and the applicable rules and regulations of the SEC thereunder.

     (b) Each of the balance sheets  (including  the related notes)  included in
the  Purchaser  SEC  Documents  fairly  presents in all  material  respects  the
financial position of the Purchaser and its consolidated  subsidiaries as of the
respective  dates  thereof  and each of the  statements  of income and cash flow
(including  the related  notes)  included in the Purchaser SEC Documents  fairly
presents in all material respects the results of operations of the Purchaser and
its consolidated  subsidiaries for the respective periods then ended,  except as
otherwise noted therein. The audited consolidated balance sheet of the Purchaser
and its consolidated  subsidiaries as of December 31, 1998 is sometimes referred
to as the  "Purchaser  Balance Sheet" and such date as the "Balance Sheet Date."
Each  of the  Purchaser  financial  statements  included  in the  Purchaser  SEC
Documents has been (i) prepared in  accordance  with GAAP  consistently  applied
during the periods  involved,  except as otherwise noted therein or in the notes
thereto  and (ii)  prepared  in  accordance  with the books and  records  of the
Purchaser.

     Section 3.6. Absence of Certain Changes.  Since the Balance Sheet Date, (a)
each of the  Purchaser  and its  subsidiaries  has  operated in the ordinary and
usual course of business and (b) there have not occurred any events,  changes or
effects  which  have had or  which  could  reasonably  likely  to  have,  in the
aggregate, a Material Adverse Effect on the Purchaser.


                                       22

                                   ARTICLE IV
                                    COVENANTS

     Section  4.1.  Further  Assurances.  From time to time  after the  Closing,
without  additional  consideration,  each of the  parties  hereto  will (or,  if
appropriate,  cause their  affiliates  to)  promptly  execute  and deliver  such
further  instruments  and take such  other  action as may be  necessary  to make
effective the transactions contemplated by this Agreement.

     Section 4.2. Brokers or Finders. Each party hereto represents, as to itself
and its affiliates that no agent, broker,  investment banker,  financial advisor
or other firm or person is or will be entitled to any  broker's or finder's  fee
or  any  other  commission  or  similar  fee  in  connection  with  any  of  the
transactions contemplated by this Agreement, other than Gerard Klauer Mattison &
Co., Inc. in the case of the Sellers.

     Section  4.3.  Performance  of  Obligations.  The  Sellers  shall cause the
Company to timely perform its obligations under this Agreement.

     Section 4.4. Tax Covenants.

     (a) All transfer,  documentary,  sales,  use,  registration  and other such
Taxes  (including,  without  limitation,  all applicable real estate transfer or
gains Taxes and stock transfer Taxes), any penalties,  interest and additions to
Tax and fees incurred in  connection  with this  Agreement and the  transactions
contemplated  hereby shall be paid by the Sellers.  Each party to this Agreement
shall cooperate in the timely making of all filings,  returns, reports and forms
as may be required in connection therewith.

     (b) All contracts,  agreements,  or intercompany  accounting  systems under
which the Company or any of its  subsidiaries may at any time have an obligation
to share the  payment of any  portion of a Tax (or any  amount  calculated  with
reference  to any  portion of a Tax)  shall be  terminated  with  respect to the
Company and each such  subsidiary  as of the Closing  Date,  and the Company and
each such subsidiary shall thereafter be released from any liability thereunder.

     (c) If any Seller  receives  any written  notice from any taxing  authority
proposing  any  adjustment  to any Tax  relating  to the  Company  or any of its
subsidiaries,  the  Seller  shall  give  prompt  written  notice  thereof to the
Purchaser and the Company,  which notice shall  describe in detail each proposed
adjustment.

     Section 4.5. Employees; Releases.

     (a) The Company has terminated all of its employees,  agents,  consultants,
independent contractors, and satisfied all of its liabilities and obligations to
such  employees,  agents,  consultants,  independent  contractors,  prior to the
Closing  including,  any liability  related to  outstanding  options to purchase
Company Shares, any severance or change in control payments or any contributions
that are or will be required to be made to any Benefit Plan in  accordance  with
the terms of such plan for the plan year in which the Closing  Date  occurs,  or
any prior plan year.

                                       23


     (b) Each Seller hereby releases,  effective as of the Closing,  the Company
(and its subsidiaries, affiliates, officers, directors and other employees) from
all  liabilities  and  obligations  it  may  owe  such  Sellers,  including  any
liabilities and obligations  based on any facts or circumstances  existing on or
prior  to the  Closing.  Each  Seller  represents  that  it  has no  outstanding
indemnity  claim  against  the Company and knows of no basis for any such claim.
The Company hereby releases,  effective as of the Closing,  each Seller from all
liabilities  and  obligations it may owe the Company,  including any liabilities
and obligations based on any facts or circumstances  existing on or prior to the
Closing.  Each Seller  represents that it knows of no liability or obligation it
may owe the  Company,  other than as set forth in Section  4.5(y) of the Company
Disclosure  Schedule.  Nothing in this Section 4.5 shall  decrease or impair any
liability  any Seller may have to the  Purchaser and no Seller shall be entitled
to  indemnification  or other  payment from the Company in respect of any matter
for which the Purchaser may be entitled to indemnification hereunder.

     (c)  The  Company  has  provided  any  required  notice  under  the  Worker
Adjustment and Retraining Notification Act, as amended (the "WARN Act"), and any
similar state statute, and to otherwise comply with any such statute with repect
to any "plant closing" or "mass layoff" (as defined in the WARN Act), or similar
event  affecting  employees  of the  Company  and  occurring  on or prior to the
Closing Date.  The Sellers shall  indemnify and hold harmless the Purchaser with
respect to any liability  under the WARN Act or similar statute arising from the
actions of the Company on or prior to the Closing Date.

     Section 4.6. NWB Board. The Sellers shall use their reasonable best efforts
to cause H. Joseph Reiser, PhD. to be appointed to the Board of Directors of NWB
as promptly as practicable.

     Section 4.7.  Lockup.  No Purchaser  Shares or any interest  therein may be
offered, sold,  transferred,  pledged,  hypothecated or otherwise disposed of by
(a)  Messrs.  Misrock  and Fox  prior to one  year  from  the  Closing  Date and
thereafter only pursuant to the Purchaser's policy regarding trading by officers
and directors or (b) any other Seller prior to one year from the Closing Date.

                                   ARTICLE V
                            SURVIVAL; INDEMNIFICATION

     Section 5.1. Survival Periods.  (a) All  representations  and warranties of
the  parties  contained  in  this  Agreement,  the  Disclosure  Schedule  or any
certificate  delivered in  connection  herewith  shall  survive  until the first
anniversary  of the Closing Date,  and, if notice of a claim is provided by such
date,  shall  survive until the final  resolution  thereof,  provided,  that the
representations and warranties  contained in Section 2.21 [share ownership] (the
"Listed  Representations")  shall survive the Closing  without  limitation,  and
provided further,  that the representations and warranties  contained in Section
2.11 shall survive until 90 days after the expiration of the applicable  statute
of  limitations  for the  assessment  of Taxes,  including all  extensions.  All

                                       24

covenants and agreements  hereunder shall survive without limit (unless by their
terms they are to survive for a shorter period).

     (b)  For  purposes  of  this  Agreement,  a  party's   representations  and
warranties shall be deemed to include such party's  Disclosure  Schedule and all
other  documents  or  certificates  delivered  by or on behalf of such  party in
connection with this Agreement.  None of the Closing,  any party's waiver of any
condition to Closing or any party's knowledge of any breach prior to the Closing
shall constitute a waiver of any rights such party may have hereunder.

     Section  5.2.  Indemnification.  Subject  to the other  provisions  of this
Article V, from and after the Closing:

     (a) The Sellers  shall  indemnify  and hold  harmless  the  Purchaser,  its
affiliates  and  the  Purchaser's  and  its  affiliates   employees,   officers,
directors,  agents  and  other  representatives  from and  against  any costs or
expenses  (including  reasonable  attorneys',  experts' and consultants'  fees),
judgments,   fines,   penalties,   losses,   claims,   liabilities  and  damages
(collectively,  "Damages") that are the result of, arise out of or relate to (i)
any breach of any  representation or warranty or failure to perform any covenant
made by or on behalf of the Company or the Sellers under this Agreement and (ii)
any liability or obligation  that is the result of, arises out of or relates to,
any fact or  circumstance  existing at or prior to the Closing Date,  other than
liabilities or obligations  disclosed to the Purchaser prior to the date hereof.
To the extent any Seller  makes a  representation,  warranty  or  covenant as to
himself,  such indemnity  obligation will be allocated to such Seller. All other
indemnity  obligations  shall  be  allocated  among  the  Sellers  pro  rata  in
accordance  with their receipt of Purchaser  shares as set forth on the attached
Exhibit A. In the absence of manifest error, any  determination by the Purchaser
as to such allocations shall be final and binding.

     (b) The  Purchaser  shall  indemnify and hold harmless the Sellers from and
against any Damages that are the result of, arise out of or relate to any breach
of any representation or warranty or the failure to perform any covenant made by
or on behalf of the Purchaser under this Agreement.

     (c) The persons to whom  indemnification is provided hereunder are referred
to herein as the "Indemnified Parties" and the persons providing indemnification
are referred to as the "Indemnifying Parties."

     Section 5.3.  Indemnification Amounts. (a) Notwithstanding any provision to
the contrary contained in this Agreement,  the Sellers shall not be obligated to
indemnify  the  Purchaser  for Damages  pursuant to this Article V to the extent
they are the result of any breach of any  representation  or warranty made by or
on behalf of the Company or the Sellers  (other than Damages  resulting from the
breach  of any of the  Listed  Representations,  as to which  there  shall be no
limitation) unless and until the dollar amount of all Damages shall equal in the
aggregate  $5,000,  in which case the Sellers will be obligated to indemnify the

                                       25

Purchaser  for the total  amount of Damages  including  any amounts  which would
otherwise  not be  required  to be  paid  by  reason  of  this  Section  5.3(a).
Notwithstanding  any provision to the contrary contained in this Agreement,  the
Sellers' indemnity  obligations  hereunder shall be limited to the return of the
Purchaser Shares received by such Sellers,  valued at the prices contemplated by
Article I hereof (on a  first-in-first-out  basis). For purposes of this Article
V, all materiality,  Material Adverse Effect and similar  qualifications  in any
representation, warranty, covenant or other provision hereof shall be ignored.

     (b)  Notwithstanding  any  provision  to the  contrary  contained  in  this
Agreement, the Purchaser shall not be obligated to indemnify the Sellers for any
Damages  pursuant  to this  Article V to the  extent  they are the result of any
breach of any  representation or warranty made by or on behalf of the Purchaser,
unless  and  until the  dollar  amount of all such  Damages  shall  equal in the
aggregate $5,000, in which case the Purchaser will be obligated to indemnify the
Sellers  for the total  amount of Damages  including  any  amounts  which  would
otherwise  not be  required  to be  paid  by  reason  of  this  Section  5.3(b).
Notwithstanding  any provision to the contrary contained in this Agreement,  the
Purchaser  shall not be obligated to indemnify the Sellers for Damages  pursuant
to this Article V in an amount exceeding the consideration paid or to be paid by
the Purchaser pursuant to Article I hereof, valued at the prices contemplated by
Article I hereof (on a first-in-first-out basis).

     Section  5.4.  Claims.   (a)  If  an  Indemnified  Party  intends  to  seek
indemnification  pursuant  to this  Article  V,  such  Indemnified  Party  shall
promptly notify the Indemnifying Party in writing of such claim. The Indemnified
Party will provide the Indemnifying  Party with prompt notice of any third party
claim in respect of which  indemnification  is  sought.  The  failure to provide
either such notice will not affect any rights hereunder except to the extent the
Indemnifying Party is materially prejudiced thereby.

     (b) If such claim involves a claim by a third party against the Indemnified
Party, the Indemnifying  Party may, within ten days after receipt of such notice
and upon notice to the  Indemnified  Party,  assume,  through counsel of its own
choosing and at its own expense,  the  settlement  or defense  thereof,  and the
Indemnified  Party shall  cooperate with it in connection  therewith,  provided,
that the Indemnified Party may participate in such settlement or defense through
counsel  chosen by it.  If the  Indemnified  Party  reasonably  determines  that
representation  by the  Indemnifying  Party's  counsel of both the  Indemnifying
Party and the  Indemnified  Party may present  such  counsel  with a conflict of
interest, then the Indemnifying Party shall pay the reasonable fees and expenses
of the Indemnified Party's counsel. Notwithstanding anything in this Section 5.4
to the  contrary,  the  Indemnifying  Party may not,  without the consent of the
Indemnified  Party,  settle or compromise  any action or consent to the entry of
any  judgment,  such  consent not to be  unreasonably  withheld.  So long as the
Indemnifying  Party is contesting any such claim in good faith,  the Indemnified
Party shall not pay or settle any such claim  without the  Indemnifying  Party's
consent, such consent not to be unreasonably withheld. If the Indemnifying Party
is not contesting such claim in good faith  (including if it does not notify the
Indemnified  Party of its assumption of the defense of such claim within the ten

                                       26

day period set forth above), then the Indemnified Party may conduct and control,
through  counsel of its own  choosing  and at the  expense  of the  Indemnifying
Party,  the  settlement or defense  thereof,  and the  Indemnifying  Party shall
cooperate with it in connection therewith.  The failure of the Indemnified Party
to  participate  in,  conduct or control  such  defense  shall not  relieve  the
Indemnifying Party of any obligation it may have hereunder.

     Section 5.5. Indemnification with Respect to Taxes.

     (a)  Notwithstanding  any other  provision  in this  Article V, the Sellers
shall indemnify, defend and hold harmless the Purchaser and, after the Effective
Time, the Company and each of its subsidiaries,  and their respective  officers,
directors,    employees,    affiliates,    controlling   persons,   agents   and
representatives,  and their  respective  successors  and assigns  (each,  a "Tax
Indemnitee") from and against,  and shall reimburse each Tax Indemnitee for, any
and  all  Taxes  (including,   without   limitation,   reasonable   expenses  of
investigation  and reasonable  attorneys' and accountants'  fees and expenses in
connection with any action, suit or proceeding) actually incurred or suffered at
any  time  by any  Tax  Indemnitee  arising  out of or  attributable  to (i) any
misrepresentation,   inaccuracy  or  breach  of  any  representation,  warranty,
covenant,  agreement  or  promise  related  to Taxes by the  Sellers  and/or the
Company  and/or any of its  subsidiaries  contained in this Agreement (or in any
certificate,  document,  list or  schedule  delivered  to the  Purchaser  by the
Sellers or the Company or any of its subsidiaries  hereunder),  (ii) any and all
unpaid Taxes for any Taxable Period ending on or before the Closing Date, except
to the extent  that such Taxes are  specifically  set forth in the  reserve  for
Taxes accrued on the Financial Statements for the period ended December 31, 1998
(iii) any and all unpaid Taxes, whether determined on a separate,  consolidated,
combined,  group or unitary  basis,  including  any  penalties  and  interest in
respect  thereof,  of the  Company or any of its  subsidiaries  (A)  pursuant to
Treas. Reg.  ss.1.1502-6 or any comparable provision of state, local, or foreign
law with respect to any Taxable Period beginning before the Closing Date and (B)
pursuant to any guaranty,  indemnification,  Tax sharing,  or similar  agreement
made on or before the Closing Date relating to the sharing of liability  for, or
payment of,  Taxes or (iv) any and all Taxes,  whether  payable  before,  on, or
after the Closing Date,  arising out of or attributable  to the  cancellation of
promissory  notes  obligations  of the Company and/or any waiver of rights by an
employee or option holder of the Company.

     (b) Any Tax or other  amount for which  indemnification  is provided  under
this  Agreement  shall be (i)  increased  to take  account of any Tax  detriment
incurred by any Tax Indemnitee  arising from the receipt or accrual of indemnity
payments  hereunder  (i.e.,  grossed-up  for any Tax  incurred on such  payment,
accrual,  and/or  increase)  and (ii) reduced to take account of any Tax benefit
attributable to the items to which such payments relate.

     (c) The indemnitor and its duly  appointed  representatives  shall have the
sole right to negotiate, resolve, settle, or contest any claim for Tax made by a
taxing  authority with respect to which the indemnitor has agreed to indemnify a
Tax  Indemnitee  under this Section 5.5 and with respect to which the indemnitor
has acknowledged in writing such indemnification obligation;  provided, however,

                                       27

that the  indemnitor  shall not initiate any claim,  settle any issue,  file any
amended Tax Return,  take or advocate any position or otherwise  take any action
that could adversely affect the Tax Indemnitee or any of its affiliates  without
the  written  consent  of  the  Tax  Indemnitee,  which  consent  shall  not  be
unreasonably  withheld. If the indemnitor does not assume the defense of a claim
for the Tax made by a taxing  authority with respect to which the indemnitor has
indemnified  a Tax  Indemnitee  under this Section 5.5, the Tax  Indemnitee  may
defend the same at the reasonable expense of the indemnitor in such manner as it
may deem  appropriate,  including,  but not limited to,  settling  such audit or
proceeding  with the  consent  of the  indemnitor,  which  consent  shall not be
unreasonably withheld.

     Section 5.6.  Exclusive  Remedy.  Following the Closing,  the provisions of
this Article V shall be the  exclusive  remedy for the matters  covered  hereby,
provided  that nothing  herein shall  relieve any party from any  liability  for
fraud.  Following the Closing, (i) all notices to the Sellers may be made to the
Representative,  (ii)  all  notices  from  the  Sellers  shall  be  made  by the
Representative and (iii) the Representative  shall have the power to act for the
Sellers in all matters related to this Agreement.


                                   ARTICLE VI
                                  MISCELLANEOUS

     Section 6.1. Notices. All notices and other communications  hereunder shall
be in  writing  and shall be deemed  given upon  receipt  by the  parties at the
following  addresses (or at such other address for a party as shall be specified
by like notice):

     (a) if to the Purchaser, to:

                  Cytogen Corporation
                  600 College Road East
                  CN 5308
                  Princeton, New Jersey 08540
                  Attention: Donald F. Crane, Jr.
                  Telecopier: (609) 987-1229

                  with a copy to:

                  Dewey Ballantine LLP
                  1301 Avenue of the Americas
                  New York, New York 10019
                  Attention: Frederick W. Kanner
                  Telecopier: (212) 259-6333



                                       28



     (b) if to the Sellers to:

                  S. Leslie Misrock, Esq., as Representative
                  1155 Avenue of the Americas
                  New York, New York 10036


                  with a copy to:

                  Proskauer Rose LLP
                  1585 Broadway
                  New York, New York 10036-8299
                  Attention: Edward Brodsky
                  Telecopier: (212) 969-2900



     Section 6.2.  Headings.  The headings  herein are inserted for  convenience
only  and  are  not  intended  to be  part  of  or  to  affect  the  meaning  or
interpretation of this Agreement.

     Section 6.3.  Counterparts.  This  Agreement may be executed in two or more
counterparts, all of which shall be considered one and the same instrument.

     Section 6.4.  Entire  Agreement;  Assignment.  (a) This  Agreement  and the
exhibits and schedules  hereto and the documents and  certificates  delivered in
connection herewith,  and the Confidentiality  Agreement and Registration Rights
Agreement, constitute the entire agreement among the parties hereto with respect
to the subject  matter  hereof,  and  supersedes  all prior and  contemporaneous
agreements  and  understandings,  both written and oral,  among the parties with
respect to the subject matter hereof.

     (b) This Agreement  shall not be assigned by a party hereto by operation of
law or  otherwise;  provided,  that the  Purchaser  may  assign  its  rights and
obligations  hereunder to any wholly owned  subsidiary of the Purchaser,  but no
such assignment shall relieve the Purchaser of its obligations hereunder if such
assignee does not perform such obligations.

     Section 6.5.  Governing Law. This Agreement shall be governed and construed
in  accordance  with the laws of the  State of New York,  without  regard to any
applicable  conflicts  of law  principles.  The  parties  hereto  expressly  and
irrevocably  (i) consent to the exclusive  jurisdiction of the federal and state
courts  sitting in New York,  (ii) agree not to bring any action related to this
Agreement or the transactions  contemplated hereby in any other court (except to
enforce the  judgement  of such  courts),  (iii) agree not to object to venue in
such  courts or to claim  that such  forum is  inconvenient  and (iv) agree that
notice or the service of process in any proceeding  shall be properly  served or

                                       29



delivered if delivered in the manner  contemplated by Section 6.1 hereof.  Final
judgement by such courts shall be  conclusive  and may be enforced in any manner
permitted by law.

     Section 6.6. Specific Performance.  The parties hereto agree that if any of
the  provisions of this  Agreement  were not performed in accordance  with their
specific terms or were otherwise  breached,  irreparable  damage would occur, no
adequate  remedy at law would exist and damages would be difficult to determine,
and that the parties  shall be entitled  to  specific  performance  of the terms
hereof, in addition to any other remedy at law or equity.

     Section 6.7.  Publicity.  Except as otherwise  required by law or the rules
and regulations of any national securities exchange, no party hereto shall issue
any press  release or otherwise  make any public  statement  with respect to the
transactions  contemplated by this Agreement without prior consultation with the
other parties hereto.

     Section 6.8. Binding Nature; No Third Party  Beneficiaries.  This Agreement
shall be binding  upon and inure  solely to the benefit of each party hereto and
their permitted successors and assigns,  and nothing in this Agreement,  express
or implied,  is intended to or shall confer upon any other person or persons any
rights, benefits or remedies of any nature whatsoever under or by reason of this
Agreement.

     Section 6.9.  Severability.  This Agreement shall be deemed severable;  the
invalidity or  unenforceability of any term or provision of this Agreement shall
not affect the validity or enforceability of this Agreement or of any other term
hereof, which shall remain in full force and effect.

     Section 6.10.  Interpretation.  As used in this Agreement,  (a) "including"
(or similar terms) shall be deemed  followed by "without  limitation"  and shall
not be deemed to be limited to matters of a similar nature to those  enumerated,
(b) "contract"  shall include any note,  bond,  mortgage,  indenture,  contract,
agreement,  permit,  license,  sublicense,  lease,  purchase order, sales order,
arrangement or other commitment,  obligation or understanding,  (c) "subsidiary"
of any person means another person,  an amount of the voting  securities,  other
voting ownership or voting partnership interests of which is sufficient to elect
at least a majority of its Board of  Directors or other  governing  body (or, if
there are no such  voting  interests,  50% or more of the  equity  interests  of
which) is owned  directly or  indirectly  by such first  person,  (d)  "ordinary
course of business" (or similar  terms) shall be deemed  followed by "consistent
with past practice" and (e) "assets" shall include  "rights,"  including  rights
under  contracts.  In  determining  whether  a fact,  event or other  item has a
Material  Adverse  Effect,  such fact,  event or other item shall be  considered
individually and in the aggregate with all other facts, events or other items.

     Section  6.11.  Payment  of  Expenses.  Whether  or  not  the  transactions
contemplated by this Agreement shall be consummated, each party hereto shall pay
its own expenses  incident to preparing for, entering into and carrying out this
Agreement.  The  Sellers  shall  be  responsible  for all of  their  own and the

                                       30

Company's  expenses  in  connection  with this  Agreement  and the  transactions
contemplated  hereby  (including  the  negotiation  and  investigation  hereof),
including legal, investment banking and accounting fees and expenses.


                                       31



         IN WITNESS WHEREOF,  the parties hereto have executed this Agreement as
of the date first written above.


                                              CYTOGEN CORPORATION


                                              By: /s/
                                                 ------------------------
                                                 Joseph Reiser, Ph.D.
                                                  President and CEO


                                              SELLERS:

                                              /s/
                                              ---------------------------
                                              S. Leslie Misrock


                                              /s/
                                              ---------------------------
                                              Alan Fox
                                              By: S. Leslie Misrock, as Agent


                                              /s/
                                              ---------------------------
                                              Max Link
                                              By: S. Leslie Misrock, as Agent


                                              CC CONSULTING A/S


                                              By: /s/
                                                 ------------------------
                                              S. Leslie Misrock, as Agent


                                              MISROCK HOLDINGS LP



                                              By: /s/
                                                 ------------------------
                                              S. Leslie Misrock
                                              General Partner




                                       32