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|DC_DOCS\96018.1||
                    PERIMMUNE HOLDINGS, INC.
                                
                      AMENDED AND RESTATED
                                
                  REGISTRATION RIGHTS AGREEMENT
                                

                  Dated as of December 22, 1997
                                

                    PERIMMUNE HOLDINGS, INC.
                                
         1330 Piccard Drive, Rockville, Maryland  20850
                                
          This Amended and Restated Registration Rights Agreement
("Agreement") is made and entered into as of December  22,  1997,
by  and  among  PerImmune Holdings, Inc., a Delaware  corporation
(the  "Company"),  and the stockholder of the Company  who  is  a
signatory hereto (the "Investor").

          WHEREAS, the Company and the Investor entered into that
certain  Registration Rights Agreement dated as of June 16,  1997
in connection with that certain Stock Purchase Agreement dated as
of  June 16, 1997 (the "June Stock Purchase Agreement"), pursuant
to which the Investor purchased 20 shares of Series B Convertible
Preferred Stock, par value $0.01.

          WHEREAS, the Company and the Investor have entered into
that certain Stock Purchase Agreement dated as of the date hereof
(the "December Stock Purchase Agreement"), pursuant to which  the
Investor  purchased 100 shares of Series B Convertible  Preferred
Stock, par value $0.01.

          WHEREAS,   the  Company  desires  to  grant  the   same
registration rights it granted to the Investor in respect of  the
shares  purchased pursuant to the June Stock Purchase  Agreement,
to  such Investor in respect of the shares purchased pursuant  to
the December Stock Purchase Agreement.

          Accordingly, in consideration of the foregoing  and  of
the  mutual  promises, covenants and conditions set forth  below,
the parties hereby agree as follows:

1.   Definitions
     
          As  used  in  this Agreement, the following capitalized
terms shall have the following meanings:

          Board  of  Directors:  The Board of  Directors  of  the
     Company.
     
          Claim:  Any  loss,  claim, damages,  liability  or
     expense    (including   the   reasonable    costs    of
     investigation and legal fees and expenses).
     
          Common  Stock:  The common stock, par value  $0.01  per
     share, of the Company.
     
          Equity  Security: Any capital stock of the  Company  or
     any  security  convertible, with or  without  consideration,
     into any such stock, or any security carrying any warrant or
     right  to  subscribe to or purchase any such stock,  or  any
     such warrant or right.
     
          Exchange  Act: The Securities Exchange Act of 1934,  as
     from time to time amended.
     
          Firm  Commitment Underwritten Offering: An offering  in
     which  the  underwriters  agree to purchase  securities  for
     distribution pursuant to a registration statement under  the
     Securities   Act  and  in  which  the  obligation   of   the
     underwriters is to purchase all the securities being offered
     if any are purchased.
     
          Holder:  The beneficial owner of a security.   For  all
     purposes of this Agreement, the Company shall be entitled to
     treat the record owner of a security as the beneficial owner
     of  such  security unless the Company has been given written
     notice   of  the  existence  and  identity  of  a  different
     beneficial owner.
     
          Indemnified   Holder:   Any   Holder   of   Registrable
     Securities, any officer, director, employee or agent of  any
     such  Holder  and  any Person who controls any  such  Holder
     within  the  meaning of either Section 15 of the  Securities
     Act or Section 20 of the Exchange Act.
     
          Misstatement: An untrue statement of a material fact or
     an  omission to state a material fact required to be  stated
     in  a  Registration Statement or Prospectus or necessary  to
     make  the statements in a Registration Statement, Prospectus
     or preliminary prospectus not misleading.
     
          Person:  A  natural  person, partnership,  corporation,
     business  trust, association, joint venture or other  entity
     or a government or agency or political subdivision thereof.
     
          Piggyback  Registration:  A  registration  pursuant  to
     Section 2 hereof.
     
          Preferred  Stock:  The  Series B Convertible  Preferred
     Stock,  par value $0.01 per share, issued and sold  pursuant
     to the Stock Purchase Agreements (as defined herein).
     
          Prospectus: The prospectus included in any Registration
     Statement,   as  supplemented  by  any  and  all  prospectus
     supplements  and  as  amended by any and all  post-effective
     amendments  and  including  all  material  incorporated   by
     reference in such prospectus.
     
          Qualifying  IPO:   The  first registered,  underwritten
     public offering of shares of Common Stock by the Company.
     
          Registrable Securities: (a) The shares of Common  Stock
     held  by  the  Investor, and (b) any  securities  issued  or
     issuable with respect to such Common Stock by way of a stock
     dividend  or stock split or in connection with a combination
     of   shares,  recapitalization,  merger,  consolidation   or
     reorganization;  provided  that  any  such  share  or  other
     security  shall be deemed to be Registrable Securities  only
     if and so long as it is a Transfer Restricted Security.
     
          Registration: A Piggyback Registration.
     
          Registration Expenses: The out-of-pocket expenses of  a
     Registration, including:
     
               (1)  all registration and filing fees (including fees with
          respect to filings required to be made with the National
          Association of Securities Dealers);
          
               (2)  fees and expenses of compliance with securities or blue sky
          laws (including fees and disbursements of counsel for the
          underwriters or selling holders in connection with blue sky
          qualifications of the Registrable Securities and determinations
          of their eligibility for investment under the laws of such
          jurisdictions as the managing underwriters or holders of a
          majority of the Registrable Securities being sold may designate);
          
               (3)  printing, messenger, telephone and delivery expenses;
          
               (4)  fees and disbursements of counsel for the Company, counsel
          for the underwriters and of not more than one firm of attorneys
          for the sellers of the Registrable Securities (the attorneys for
          such sellers to be determined by a vote of the majority of the
          aggregate shares of Registrable Securities requested to be
          included in the Registration Statement for  such Registration);
          
               (5)  fees and disbursements of all independent certified public
          accountants of the Company incurred in connection with such
          Registration (including the expenses of any special audit and
          "cold comfort" letters incident to such registration);
          
               (6)  fees and disbursements of underwriters (excluding discounts,
          commissions or fees of underwriters, selling brokers, dealer
          managers or similar securities industry professionals relating to
          the distribution of the Registrable Securities);
          
               (7)  premiums and other costs of securities acts liability
          insurance if the Company so desires or if the underwriters or
          selling holders of Registrable Securities so require; and
          
               (8)  fees and expenses of any other Persons retained by the
          Company.
          
          Registration  Statement:  Any  registration   statement
     under the Securities Act on an appropriate form (which  form
     shall   be   available  for  the  sale  of  the  Registrable
     Securities in accordance with the intended method or methods
     of  distribution  thereof and shall  include  all  financial
     statements required by the SEC to be filed therewith)  which
     covers Registrable Securities pursuant to the provisions  of
     this  Agreement, including the Prospectus included  in  such
     registration statement, amendments (including post-effective
     amendments) and supplements to such registration  statement,
     and  all  exhibits  to  and  all  material  incorporated  by
     reference in such registration statement.
     
          Securities  Act: The Securities Act of  1933,  as  from
     time to time amended.
     
          SEC: The Securities and Exchange Commission.
     
          Stock  Purchase  Agreements:  The June  Stock  Purchase
     Agreement and the December Stock Purchase Agreement.
     
          Transfer Restricted Security: A security that  has  not
     been sold to or through a broker, dealer or underwriter in a
     public  distribution or other public securities  transaction
     or  sold  in a transaction exempt from the registration  and
     prospectus delivery requirements of the Securities Act under
     Rule  144  promulgated thereunder (or any  successor  rule).
     The  foregoing  notwithstanding, a security shall  remain  a
     Transfer  Restricted Security until (i)  all  stop  transfer
     instructions  or  notations  and  restrictive  legends  with
     respect  to  such security have been lifted or  removed  and
     (ii)  the  Holder of such security has received  at  Company
     expense  an opinion of counsel to the Company (which counsel
     and opinion are reasonably satisfactory to such Holder),  to
     the  effect  that  such shares in such  Holder's  hands  are
     freely  transferable  in any public or  private  transaction
     without  registration  under the  Securities  Act  (or  such
     Holder has waived receipt of such opinion).
     
          Underwritten Registration or Underwritten  Offering:  A
     registration in which securities of the Company are sold  to
     an underwriter for distribution to the public.
     
2.   Piggyback Registrations
     
     (a)  Participation
          
          Each  time  the Company decides to file a  Registration
Statement under the Securities Act (other than on Forms S-4 or S-
8 or any successor form thereto and other than in connection with
a Qualifying IPO) covering the offer and sale by it or any of its
security holders of any of its securities for money, the  Company
shall  give  written notice thereof to all Holders of outstanding
Registrable Securities, which written notice shall state that the
Company has decided to so file a registration statement and shall
include the approximate date that such registration statement  is
expected to be filed with the SEC and the name of any underwriter
(if  any)  with  respect  to such offering.   The  Company  shall
include in such registration statement such shares of Registrable
Securities for which it has received written requests to register
such  shares  within 30 days after such written notice  has  been
given.  If the registration statement is to cover an Underwritten
Offering,  such Registrable Securities shall be included  in  the
underwriting  on the same terms and conditions as the  securities
otherwise being sold through the underwriters.

     (b)  Underwriter's Cutback
          
          Subject to the requirements of Section 10 hereof, if in
the  good  faith  judgment of the managing  underwriter  of  such
offering  the  inclusion  of  all of the  shares  of  Registrable
Securities  and any other Common Stock requested to be registered
would interfere with the successful marketing of a smaller number
of  such  shares,  then  the  number  of  shares  of  Registrable
Securities and other Common Stock to be included in the  offering
shall be reduced to such smaller number with the participation in
such  offering  to  be in the following order of  priority:   (1)
first,  the shares of Common Stock which the Company proposes  to
sell  for  its own account, (2) second, the shares of Registrable
Securities and any other shares of Common Stock requested  to  be
included.   Any necessary allocation among the Holders of  shares
within each of the foregoing groups shall be pro rata among  such
Holders  requesting such registration based upon  the  number  of
shares  of Common Stock and Registrable Securities owned by  such
Holders.

     (c)  Company Control
          
          The   Company   may  decline  to  file  a  Registration
Statement  after giving notice to any Holder pursuant to  Section
3(a) above, or withdraw a Registration Statement after filing and
after  such  notice,  but  prior to  the  effectiveness  thereof,
provided  that the Company shall promptly notify each  Holder  in
writing  of any such action and provided further that the Company
shall  bear all expenses incurred by such Holder or otherwise  in
connection with such withdrawn Registration Statement.

3.   Hold-Back Agreements
     
          Upon the written request of the managing underwriter of
any  Underwritten Offering of the Company's securities, a  Holder
of Registrable Securities shall not sell, make any short sale of,
loan,  grant any option for the purchase of, or otherwise dispose
of  any Registrable Securities (other than those included in such
registration) without the prior written consent of such  managing
underwriter  for  a  period (not to exceed  30  days  before  the
effective  date  and  180  days thereafter)  that  such  managing
underwriter reasonably determines is necessary in order to effect
the  underwritten  public offering; provided  that  each  of  the
officers  and  directors of the Company shall have  entered  into
substantially  similar  holdback agreements  with  such  managing
underwriter covering at least the same period.

4.   Registration Procedures
     
          If  and  whenever the Company is required  to  register
Registrable  Securities in a Piggyback Registration, the  Company
will  use its best efforts to effect such registration to  permit
the  sale  of such Registrable Securities in accordance with  the
intended  plan of distribution thereof, and pursuant thereto  the
Company will as expeditiously as possible:

          a)   prepare and file with the SEC as soon as practicable a
Registration   Statement  with  respect   to   such   Registrable
Securities  and  use its best efforts to cause such  Registration
Statement  to become effective and remain continuously  effective
until  the date earlier to occur of (i) the date six months  from
the  date such Registration Statement was declared effective, and
(ii)  the date the last of the Registrable Securities covered  by
such  Registration Statement have been sold provided that  before
filing  a  Registration Statement or Prospectus or any amendments
or  supplements thereto, the Company shall furnish to the Holders
of  the  Registrable  Securities  covered  by  such  Registration
Statement and the underwriters, if any, draft copies of all  such
documents  proposed to be filed, which documents will be  subject
to  the  review of such Holders and underwriters, and the Company
shall not file any Registration Statement or amendment thereto or
any Prospectus or any supplement thereto to which the Holders  of
a   majority  of  the  Registrable  Securities  covered  by  such
Registration  Statement  or  the  underwriters,  if  any,   shall
reasonably object;

          b)   prepare and file with the SEC such amendments and post-
effective  amendments  to the Registration  Statement,  and  such
supplements to the Prospectus, as may be requested by any  Holder
of  Registrable  Securities  or any  underwriter  of  Registrable
Securities  or  as may be required by the rules,  regulations  or
instructions  applicable to the registration  form  used  by  the
Company  or  by  the  Securities Act  or  rules  and  regulations
thereunder to keep the Registration Statement effective until all
Registrable Securities covered by such Registration Statement are
sold  in  accordance with the intended plan of  distribution  set
forth  in  such  Registration  Statement  or  supplement  to  the
Prospectus;

          c)   promptly notify the selling Holders of Registrable
Securities  and  the  managing  underwriter,  if  any,  and   (if
requested by any such Person) confirm such advice in writing,

               (1)  when the Prospectus or any supplement or post-effective
          amendment has been filed, and, with respect to the Registration
          Statement or any post-effective amendment, when the same has
          become effective,
          
               (2)  of any request by the SEC for amendments or supplements to
          the Registration Statement or the Prospectus or for additional
          information,
          
(3)  of the issuance by the SEC of any stop order suspending the
effectiveness of the Registration Statement or the initiation of
any proceedings for that purpose,
(4)  if at any time the representations and warranties of the
Company contemplated by clause (1) of paragraph (o) below cease
to be accurate in all material respects,
(5)  of the receipt by the Company of any notification with
respect to the suspension of the qualification of the Registrable
Securities for sale in any jurisdiction or the initiation or
threatening of any proceeding for such purpose, and
(6)  of the existence of any fact which results in the
Registration Statement, the Prospectus or any document
incorporated therein by reference containing a Misstatement;
          d)   make every reasonable effort to obtain the withdrawal of any
order  suspending the effectiveness of the Registration Statement
at the earliest possible time;

          e)   if requested by the managing underwriter or a Holder of
Registrable   Securities  being  sold  in  connection   with   an
Underwritten Offering, immediately incorporate in a supplement or
post-effective  amendment  such  information  as   the   managing
underwriter  and  the Holders of a majority  of  the  Registrable
Securities  being sold agree should be included therein  relating
to  the  sale  of the Registrable Securities, including,  without
limitation, information with respect to the number of  shares  of
Registrable  Securities being sold to underwriters, the  purchase
price  being paid therefor by such underwriters and with  respect
to   any  other  terms  of  the  Underwritten  Offering  of   the
Registrable Securities to be sold in such offering; and make  all
required  filings of such supplement or post-effective  amendment
as  soon  as notified of the matters to be incorporated  in  such
supplement or post-effective amendment;

          f)   promptly prior to the filing of any document which is to be
incorporated by reference into the Registration Statement or  the
Prospectus  (after initial filing of the Registration  Statement)
provide copies of such document to counsel to the selling Holders
of  Registrable  Securities and to the managing  underwriter,  if
any,  and  make  the  Company's  representatives  available   for
discussion  of  such  document and  make  such  changes  in  such
document prior to the filing thereof as counsel for such  selling
Holders or underwriters may reasonably request;

          g)   furnish to each selling Holder of Registrable Securities and
the  managing  underwriter, without charge, at least  one  signed
copy   of  the  Registration  Statement  and  any  post-effective
amendments thereto, including financial statements and schedules,
all  documents incorporated therein by reference and all exhibits
(including those incorporated by reference);

          h)   deliver to each selling Holder of Registrable Securities and
the  underwriters, if any, without charge, as many copies of each
Prospectus (and each preliminary prospectus) as such Persons  may
reasonably request (the Company hereby consenting to the  use  of
each  such Prospectus (or preliminary prospectus) by each of  the
selling  Holders of Registrable Securities and the  underwriters,
if  any,  in  connection  with  the  offering  and  sale  of  the
Registrable Securities covered by such Prospectus (or preliminary
prospectus);

          i)   prior to any public offering of Registrable Securities,
register  or  qualify or cooperate with the  selling  Holders  of
Registrable  Securities,  the underwriters,  if  any,  and  their
respective  counsel  in  connection  with  the  registration   or
qualification of such Registrable Securities for offer  and  sale
under  the  securities or blue sky laws of such jurisdictions  as
such selling Holders or underwriters may designate in writing and
do anything else necessary or advisable to enable the disposition
in  such  jurisdictions of the Registrable Securities covered  by
the  Registration Statement; provided that the Company shall  not
be   required  to  qualify  generally  to  do  business  in   any
jurisdiction  where it is not then so qualified or  to  take  any
action  which would subject it to general service of  process  in
any such jurisdiction where it is not then so subject;

          j)   cooperate with the selling Holders of Registrable Securities
and  the  managing underwriter, if any, to facilitate the  timely
preparation   and  delivery  of  certificates  not  bearing   any
restrictive legends representing the Registrable Securities to be
sold  and  cause  such  Registrable  Securities  to  be  in  such
denominations  and  registered in  such  names  as  the  managing
underwriter may request at least three business days prior to any
sale of Registrable Securities to the underwriters;

          k)   use its best efforts to cause the Registrable Securities
covered  by the Registration Statement to be registered  with  or
approved  by  such other governmental agencies or authorities  as
may  be necessary to enable the seller or sellers thereof or  the
underwriters,  if  any,  to consummate the  disposition  of  such
Registrable Securities;

          l)   if the Registration Statement or the Prospectus contains a
Misstatement, prepare a supplement or post-effective amendment to
the  Registration  Statement or the  related  Prospectus  or  any
document  incorporated therein by reference  or  file  any  other
required  document  so  that,  as  thereafter  delivered  to  the
purchasers of the Registrable Securities, the Prospectus will not
contain a Misstatement;

m)   cause all Registrable Securities covered by the Registration
Statement to be listed on any national securities exchange or
authorized for quotation on NASDAQ or in the National Market
System on which Common Stock is then listed or is authorized for
quotation, if requested by the Holders of a majority of such
Registrable Securities or the managing underwriter, if any;
          n)   provide a CUSIP number for all Registrable Securities not
later than the effective date of the Registration Statement;

          o)   enter into such agreements (including an underwriting
agreement) and do anything else necessary or advisable  in  order
to  expedite  or  facilitate the disposition of such  Registrable
Securities,  and  in  such  connection,  whether   or   not   the
registration is an Underwritten Registration:

               (1)  make such representations and warranties to the Holders of
          such Registrable Securities and the underwriters, if any, in
          form, substance and scope as are customarily made by issuers to
          underwriters in primary Underwritten Offerings;
          
               (2)  obtain opinions of counsel to the Company and updates
          thereof (which counsel and opinions (in form, scope and
          substance) shall be reasonably satisfactory to the managing
          underwriter, if any, and the Holders of a majority of the
          Registrable Securities being sold) addressed to each selling
          Holder and the underwriter, if any, covering the matters
          customarily covered in opinions delivered to underwriters in
          primary Underwritten Offerings and such other matters as may be
          reasonably requested by such Holders or underwriters;
          
               (3)  obtain "cold comfort" letters and updates thereof from the
          Company's independent certified public accountants addressed to
          the  selling Holders of Registrable Securities and  the
          underwriters, if any, such letters to be in customary form and
          covering matters of the type customarily covered in "cold
          comfort" letters by underwriters in connection with primary
          Underwritten Offerings;
          
(4)  if an underwriting agreement is entered into, cause the same
to include the indemnification and contribution provisions and
procedures of Section 6 hereof with respect to all parties to be
indemnified pursuant to said Section (or, with respect to the
indemnification of such underwriters, such similar
indemnification and contribution provisions as such underwriters
shall customarily require); and
               (5)  deliver such documents and certificates as may be requested
          by the Holders of a majority of the Registrable Securities being
          sold and the managing underwriter, if any, to evidence compliance
          with clause (1) above and with any customary conditions contained
          in the underwriting agreement or other agreement entered into by
          the Company.
          
The  above  shall be done at each closing under such underwriting
or similar agreement or as and to the extent otherwise reasonably
requested  by  the  Holders  of  a majority  of  the  Registrable
Securities being sold;

          p)   make available for inspection by representatives of the
Holders  of a majority of the Registrable Securities being  sold,
any underwriter participating in any disposition pursuant to such
Registration  Statement, and any attorney or accountant  retained
by  the sellers or any such underwriter, all financial and  other
records and pertinent corporate documents and properties  of  the
Company,   and  cause  the  Company's  officers,  directors   and
employees to supply all information reasonably requested  by  any
such  representative,  underwriter,  attorney  or  accountant  in
connection  with  the Registration; provided  that  any  records,
information  or documents that are designated by the  Company  in
writing  as  confidential  shall be  kept  confidential  by  such
Persons  unless  disclosure  of  such  records,  information   or
documents is required by court or administrative order; and

          q)   otherwise use its best efforts to comply with all applicable
rules and regulations of the SEC, and make generally available to
its   security   holders  earnings  statements   satisfying   the
provisions of Section 11(a) of the Securities Act, no later  than
45 days after the end of any 12-month period (or 90 days, if such
period  is a fiscal year) (x) commencing at the end of any fiscal
quarter  in which Registrable Securities are sold to underwriters
in  an Underwritten Offering, or, if not sold to underwriters  in
such  an  offering,  (y) beginning with the first  month  of  the
Company's  first  fiscal quarter commencing after  the  effective
date  of the Registration Statement, which statements shall cover
said 12-month periods.

          Notwithstanding the foregoing, the Company shall,  upon
written   notice   delivered  to  the  Holders   of   Registrable
Securities, be entitled to postpone the filing or declaration  of
effectiveness of a Registration Statement required or proposed to
be  filed  hereunder (i) upon the happening of any event  of  the
kind  described in Section 4(c)(6), or (ii) if, in the reasonable
determination of the Company, there exists circumstances not  yet
disclosed  to the public, which would be required to be disclosed
in  such Registration Statement and the disclosure of which would
be  materially harmful to the Company.  The Company shall use its
best  efforts  to  minimize the length  of  any  postponement  or
discontinuance  provided  that the Company  may  postpone  for  a
period of sixty (60) days the disclosure of any circumstances if,
in  the  reasonable determination of the Company, such disclosure
would be materially harmful to the Company.

5.   Registration Expenses
     
     (a)   Piggyback Registrations
          
          The   Company  shall  bear  all  Registration  Expenses
incurred in connection with all Piggyback Registrations.

     (b)  Company Expenses
          
          The  Company also will, in any event, pay its  internal
expenses   (including,  without  limitation,  all  salaries   and
expenses  of  its  officers  and employees  performing  legal  or
accounting duties), the expense of any annual audit, the fees and
expenses  incurred  in  connection  with  any  listing   of   the
securities  to  be registered on a securities exchange,  and  the
fees  and  expenses  of  any Person, including  special  experts,
retained by the Company.

6.   Indemnification
     
     (a)  Indemnification by the Company
          
          The  Company agrees to indemnify and hold harmless each
Indemnified Holder from and against all Claims arising out of  or
based  upon  any  Misstatement  or alleged  Misstatement,  except
insofar  as such Misstatement or alleged Misstatement  was  based
upon  information  furnished in writing to  the  Company  by  any
Indemnified  Holder expressly for use in the document  containing
such  Misstatement or alleged Misstatement.  This indemnity shall
not  be exclusive and shall be in addition to any liability which
the Company may otherwise have.

          The foregoing notwithstanding, the Company shall not be
liable  to  the extent that any such Claim arises out  of  or  is
based  upon  a Misstatement or alleged Misstatement made  in  any
preliminary prospectus if (i) such Indemnified Holder  failed  to
send  or  deliver a copy of the Prospectus with or prior  to  the
delivery  of  written  confirmation of the  sale  of  Registrable
Securities  giving  rise to such Claim and  (ii)  the  Prospectus
would have corrected such untrue statement or omission.

          In  addition,  the Company shall not be liable  to  the
extent  that  any  such Claim arises out of or is  based  upon  a
Misstatement or alleged Misstatement in a Prospectus, (x) if such
Misstatement or alleged Misstatement is corrected in an amendment
or  supplement to such Prospectus and (y) having previously  been
furnished  by  or  on behalf of the Company with  copies  of  the
Prospectus as so amended or supplemented, such Indemnified Holder
thereafter  fails  to deliver such Prospectus as  so  amended  or
supplemented prior to or concurrently with the sale to the person
who purchased a Registrable Security from such Indemnified Holder
and who is asserting such Claim.

          The  Company shall also indemnify underwriters, selling
brokers,   dealer   managers  and  similar  securities   industry
professionals  participating  in  a  distribution  covered  by  a
Registration  Statement, their officers and  directors  and  each
Person  who controls such Persons (within the meaning of  Section
15  of  the Securities Act or Section 20 of the Exchange Act)  to
the   same  extent  as  provided  above  with  respect   to   the
indemnification  of  the  Indemnified  Holders   of   Registrable
Securities.

     (b)  Indemnification Procedures
          
          If any action or proceeding (including any governmental
investigation or inquiry) shall be brought or asserted against an
Indemnified  Holder in respect of which indemnity may  be  sought
from  the Company, such Indemnified Holder shall promptly  notify
the  Company in writing, and the Company shall assume the defense
thereof, including the employment of counsel satisfactory to such
Indemnified Holder and the payment of all expenses.

          Such  Indemnified Holder shall have the right to employ
separate  counsel  in any such action and to participate  in  the
defense  thereof,  but  the fees and expenses  of  such  separate
counsel  shall  be the expense of such Indemnified Holder  unless
(i)  the  Company has agreed to pay such fees and expenses,  (ii)
the  Company  shall  have failed to assume the  defense  of  such
action or proceeding or has failed to employ counsel satisfactory
to  such  Indemnified Holder in any such action or proceeding  or
(iii)  the  named  parties  to  any  such  action  or  proceeding
(including  any impleaded parties) include both such  Indemnified
Holder  and  the Company, and such Indemnified Holder shall  have
been  advised  by  counsel that there may be one  or  more  legal
defenses  available to such Indemnified Holder that are different
from or additional to those available to the Company.

          If  such  Indemnified Holder notifies  the  Company  in
writing  that it elects to employ separate counsel at the expense
of  the  Company as permitted by the provisions of the  preceding
paragraph,  the Company shall not have the right  to  assume  the
defense   of  such  action  or  proceeding  on  behalf  of   such
Indemnified  Holder.  The foregoing notwithstanding, the  Company
shall not be liable for the reasonable fees and expenses of  more
than  one  separate  firm  of attorneys  at  any  time  for  such
Indemnified Holder and any other Indemnified Holders (which  firm
shall  be  designated in writing by such Indemnified Holders)  in
connection with any one such action or proceeding or separate but
substantially  similar or related actions or proceedings  in  the
same jurisdiction arising out of the same general allegations  or
circumstances.

          The  Company shall not be liable for any settlement  of
any  such  action  or  proceeding effected  without  its  written
consent, but if settled with its written consent, or if there  be
a  final  judgment  for  the plaintiff  in  any  such  action  or
proceeding,  the  Company agrees to indemnify and  hold  harmless
such  Indemnified Holders from and against any loss or  liability
by reason of such settlement or judgment.

     (c)  Indemnification by Holder of Registrable Securities
          
          Each   Holder  of  Registrable  Securities  agrees   to
indemnify  and  hold  harmless the  Company,  its  directors  and
officers and each Person, if any, who controls the Company within
the meaning of either Section 15 of the Securities Act or Section
20  of  the  Exchange  Act to the same extent  as  the  foregoing
indemnity from the Company to such Holder, but only with  respect
to  information relating to such Holder furnished in  writing  by
such  Holder  expressly  for use in any  Registration  Statement,
Prospectus  or  preliminary prospectus.  In  no  event,  however,
shall   the   liability  hereunder  of  any  selling  Holder   of
Registrable Securities be greater than the dollar amount  of  the
proceeds received by such Holder upon the sale of the Registrable
Securities giving rise to such indemnification obligation.

          In  case  any  action or proceeding  shall  be  brought
against  the  Company or its directors or officers  or  any  such
controlling person, in respect of which indemnity may  be  sought
against  a  Holder of Registrable Securities, such  Holder  shall
have  the rights and duties given the Company and the Company  or
its  directors or officers or such controlling person shall  have
the  rights and duties given to each Holder by Sections 6(a)  and
6(b) above.

          The  Company  shall be entitled to receive  indemnities
from  underwriters, selling brokers, dealer managers and  similar
securities   industry   professionals   participating   in    the
distribution, to the same extent as provided above  with  respect
to   information  so  furnished  in  writing  by   such   Persons
specifically  for  inclusion  in any Prospectus  or  Registration
Statement.

     (d)  Contribution
          
          If  the indemnification provided for in this Section  6
is  unavailable  to an indemnified party under  Section  6(a)  or
Section  6(c) above (other than by reason of exceptions  provided
in  those Sections) in respect of any Claims referred to in  such
Sections,  then each applicable indemnifying party,  in  lieu  of
indemnifying  such  indemnified party, shall  contribute  to  the
amount  paid or payable by such indemnified party as a result  of
such  Claims in such proportion as is appropriate to reflect  the
relative  fault  of  the  Company on the  one  hand  and  of  the
Indemnified Holder on the other in connection with the statements
or  omissions which resulted in such Claims as well as any  other
relevant equitable considerations.  The amount paid or payable by
a  party  as  a result of the Claims referred to above  shall  be
deemed  to  include,  subject to the  limitations  set  forth  in
Section  6(b),  any  legal or other fees or  expenses  reasonably
incurred  by  such  party  in connection  with  investigating  or
defending any action or claim.

          The  relative fault of the Company on the one hand  and
of  the  Indemnified Holder on the other shall be  determined  by
reference  to,  among other things, whether the  Misstatement  or
alleged  Misstatement  relates to  information  supplied  by  the
Company  or  by the Indemnified Holder and the parties'  relative
intent,  knowledge,  access  to information  and  opportunity  to
correct or prevent such Misstatement or alleged Misstatement.

          The  Company and each Holder of Registrable  Securities
agree  that  it  would not be just and equitable if  contribution
pursuant  to  this  Section  6(d) were  determined  by  pro  rata
allocation  or by any other method of allocation which  does  not
take account of the equitable considerations referred to above.

          Notwithstanding the provisions of this Section 6(d), an
Indemnified Holder shall not be required to contribute any amount
in excess of the amount by which (i) the total price at which the
securities  that  were  sold  by  such  Indemnified  Holder   and
distributed to the public were offered to the public exceeds (ii)
the  amount  of  any  damages which such Indemnified  Holder  has
otherwise been required to pay by reason of such Misstatement.

          No   person   guilty  of  fraudulent  misrepresentation
(within the meaning of Section 11(f) of the Securities Act) shall
be entitled to contribution from any person who was not guilty of
such fraudulent misrepresentation.

7.   Exchange Act Reporting Requirements
     
          From   and  after  the  effective  date  of  the  first
registration statement filed by the Company under the  Securities
Act,  the Company shall (whether or not it shall then be required
to  do so) timely file such information, documents and reports as
the Commission may require or prescribe under Section 13 or 15(d)
(whichever is applicable) of the Exchange Act.  In addition,  the
Company  shall  take  such other measures  and  file  such  other
information,  documents  and  reports,  as  shall  hereafter   be
required by the Commission as a condition to the availability  of
Rule  144  under the Securities Act (or any successor  provision)
and the use of Form S-3.

          From  and  after such date, the Company shall forthwith
upon  request furnish any Holder of Registrable Securities (i)  a
written  statement by the Company that it has complied with  such
reporting requirements, (ii) a copy of the most recent annual  or
quarterly report of the Company, and (iii) such other reports and
documents filed by the Company with the Commission as such Holder
may reasonably request in availing itself of an exemption for the
sale  of  Registrable Securities without registration  under  the
Securities Act.

          The  purpose of the foregoing requirements are  (x)  to
enable  any  such  Holder  to  comply  with  the  current  public
information requirements contained in paragraph (c) of  Rule  144
under the Securities Act (or any successor provision) and (y)  to
qualify  the  Company for the use of registration  statements  on
Form S-3.

8.   Requirements for Participation in Underwritten Offerings
     
          No  Person may participate in any Underwritten Offering
pursuant  to  a  Registration hereunder unless  such  Person  (a)
agrees to sell such Person's securities on the basis provided  in
any  underwriting  arrangements approved by the Persons  entitled
hereunder  to  approve such arrangements and  (b)  completes  and
executes  all  questionnaires, powers of  attorney,  indemnities,
underwriting  agreements and other documents required  under  the
terms of such underwriting arrangements.

9.   Suspension of Sales
     
          Upon  receipt  of written notice from the Company  that
(i)   a   Registration   Statement  or  Prospectus   contains   a
Misstatement,  or  (ii) in the reasonable  determination  of  the
Company,  there  exists circumstances not yet  disclosed  to  the
public   which  would  be  required  to  be  disclosed  in   such
Registration  Statement  and the disclosure  of  which  would  be
materially  harmful  to the Company, each Holder  of  Registrable
Securities shall forthwith discontinue disposition of Registrable
Securities  until  such  Holder  has  received  copies   of   the
supplemented  or  amended  Prospectus required  by  Section  4(1)
hereof, or until such Holder is advised in writing by the Company
that  the  use  of  the  Prospectus may be resumed,  and,  if  so
directed by the Company, such Holder shall deliver to the Company
(at  the Company's expense) all copies, other than permanent file
copies  then  in  such  Holder's possession,  of  the  Prospectus
covering  such  Registrable Securities current  at  the  time  of
receipt  of  such notice.  The Company shall use  its  reasonable
best  efforts to minimize the length of such suspension of sales,
provided,  that the Company may require the suspension  of  sales
for  a period of sixty (60) days in the event that the disclosure
of  any  circumstances, in the reasonable  determination  of  the
Company would be materially harmful to the Company.

10.  Miscellaneous
     
     (a)  Remedies
          
          Each  Holder of Registrable Securities, in addition  to
being  entitled  to exercise all rights provided herein,  in  the
Stock  Purchase Agreements and granted by law, including recovery
of  damages,  shall  be entitled to specific performance  of  its
rights  under  this Agreement.  The Company agrees that  monetary
damages  would not be adequate compensation for any loss incurred
by  reason  of a breach by it of the provisions of this Agreement
and hereby agrees to waive the defense in any action for specific
performance that a remedy at law would be adequate.

     (b)  No Inconsistent Agreements
          
          The  Company  shall not on or after the  date  of  this
Agreement enter into any agreement with respect to its securities
that  is  inconsistent with the rights granted to the Holders  of
Registrable  Securities in this Agreement or otherwise  conflicts
with the provisions hereof.

          Except  as  otherwise disclosed to  the  Investor,  the
Company  has  not  previously entered  into  any  agreement  with
respect to its securities granting any registration rights to any
Person.

     (c)  Amendments and Waivers
          
          The   provisions  of  this  Agreement,  including   the
provisions of this sentence, may not be amended, modified or  sup
plemented,  and  waivers  or  consents  to  departures  from  the
provisions  hereof  may  not  be given  unless  the  Company  has
obtained  the  written  consent of the  Holders  of  at  least  a
majority  of  the  outstanding shares of Registrable  Securities.
The  foregoing notwithstanding, a waiver or consent to  departure
from the provisions hereof that relates exclusively to the rights
of  Holders of shares of Registrable Securities whose shares  are
being sold pursuant to a Registration Statement and that does not
directly  or  indirectly affect the rights of  other  Holders  of
shares of Registrable Securities may be given by the Holders of a
majority of the shares of Registrable Securities being sold.

     (d)  Notices
          
          All  notices and other communications provided  for  or
permitted  hereunder shall be made in writing  by  hand-delivery,
registered  first-class mail, telex, telecopier, or  air  courier
guaranteeing overnight delivery:

               i)   if to a Holder of Registrable Securities, at the most
          current address given by such Holder to the Company in accordance
          with the provisions hereof, which address initially is, with
          respect to each Investor, the address set forth in Section 9.2(a)
          of the June Stock Purchase Agreement, with a copy to Reicker,
          Clough, Pfau & Pyle LLP, 1421 State Street, Suite B, Santa
          Barbara, California 93102-1470, Attention: Dan Reicker, Esq.; and
          
               ii)  if to the Company, initially at its address set forth in
          Section 9.2(b) of the June Stock Purchase Agreement and
          thereafter at such other address, notice of which is given in
          accordance with the provisions hereof, with a copy to  with a
          copy to Latham & Watkins, Latham & Watkins, 1001 Pennsylvania
          Avenue, N.W., Suite 1300, Washington, D.C. 20004, Attention:
          Bruce E. Rosenblum, Esq.
          
          All such notices and communications shall be deemed  to
have  been  duly  given:   at  the time  delivered  by  hand,  if
personally delivered; five business days after being deposited in
the  mail,  postage  prepaid, if mailed; when answered  back,  if
telexed;  when receipt acknowledged, if telecopied;  and  on  the
next  business  day,  if  timely  delivered  to  an  air  courier
guaranteeing  overnight  delivery.  The  Company  shall  promptly
provide  a  list of the most current addresses of the Holders  of
Registrable  Securities  given  to  it  in  accordance  with  the
provisions hereof to any such Holder for the purpose of  enabling
such  Holder to communicate with other Holders in connection with
this Agreement.

     (e)  Successors and Assigns
          
          This  Agreement shall inure to the benefit  of  and  be
binding upon the successors and assigns of each of the parties.

     (f)  Counterparts
          
          This  Agreement  may  be  executed  in  any  number  of
counterparts  and by the parties hereto in separate counterparts,
each  of which when so executed shall be deemed to be an original
and all of which taken together shall constitute one and the same
agreement.

     (g)  Table of Contents and Headings
          
          The  table  of contents and headings in this  Agreement
are  for  convenience of reference only and shall  not  limit  or
otherwise affect the meaning hereof.

     (h)  Governing Law
          
          This  Agreement shall be governed by and  construed  in
accordance with the laws of the State of Maryland.

     (i)  Severability
          
          In  the  event  that any one or more of the  provisions
contained herein, or the application thereof in any circumstance,
is held invalid, illegal or unenforceable, the validity, legality
and  enforceability of any such provision in every other  respect
and  of  the remaining provisions contained herein shall  not  be
affected or impaired thereby.

     (j)  Forms
          
          All references in this Agreement to particular forms of
registration  statements are intended to  include  all  successor
forms  which  are  intended to replace, or to  apply  to  similar
transactions as, the forms herein referenced.

     (k)  Entire Agreement
          
          This  Agreement  and the Stock Purchase Agreements  are
intended  by  the respective parties to those agreements  as  the
final  expression of their respective agreement and are  intended
to  be  a  complete and exclusive statement of the agreement  and
understanding  of the parties hereto in respect  of  the  subject
matter  contained  herein.  There are no restrictions,  promises,
warranties  or  undertakings,  other  than  those  set  forth  or
referred  to  herein or therein with respect to the  registration
rights granted by the Company with respect to the securities sold
pursuant  to  the Stock Purchase Agreements.  This Agreement  and
the  Stock Purchase Agreements supersede all prior agreements and
understandings between the parties with respect to  such  subject
matter.

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


                              COMPANY:

                              PERIMMUNE HOLDINGS, INC.

                              By:  /s/MICHAEL G. HANNA
                                                            Name:
Michael G. Hanna
                                                           Title:
President


                              INVESTOR:

                              MENTOR CORPORATION

                              By:  /s/CHRISTOPHER J. CONWAY
                                                            Name:
Christopher J. Conway
                                                           Title:
Chairman, CEO


1.   DEFINITIONS                                                1

2.   PIGGYBACK REGISTRATIONS                                    5
     
     (A)  PARTICIPATION                                         5
     
     (B)  UNDERWRITER'S CUTBACK                                 5
     
     (C)  COMPANY CONTROL                                       6

3.   HOLD-BACK AGREEMENTS                                       6

4.   REGISTRATION PROCEDURES                                    6

5.   REGISTRATION EXPENSES                                     11
     
     (A)  PIGGYBACK REGISTRATIONS                              11
     
     (B)  COMPANY EXPENSES                                     11

6.   INDEMNIFICATION                                           12
     
     (A)  INDEMNIFICATION BY COMPANY                           12
     
     (B)  INDEMNIFICATION PROCEDURES                           13
     
     (C)  INDEMNIFICATION BY HOLDER OF REGISTRABLE SECURITIES  13
     
     (D)  CONTRIBUTION                                         14

7.   EXCHANGE ACT REPORTING REQUIREMENTS                       15

8.   REQUIREMENTS FOR PARTICIPATION IN UNDERWRITTEN OFFERINGS  16

9.   SUSPENSION OF SALES                                       16

10.  MISCELLANEOUS                                             16
     
     (A)  REMEDIES                                             16
     
     (B)  NO INCONSISTENT AGREEMENTS                           17
     
     (C)  AMENDMENTS AND WAIVERS                               17
     
     (D)  NOTICES                                              17
     
     (E)  SUCCESSORS AND ASSIGNS                               18
     
     (F)  COUNTERPARTS                                         18
     
     (G)  TABLE OF CONTENTS AND HEADINGS                       18
     
     (H)  GOVERNING LAW                                        18
     
     (I)  SEVERABILITY                                         18
     
     (J)  FORMS                                                       19
     
     (K)  ENTIRE AGREEMENT                                     19