<PAGE>




DATED  3RD JULY  1996









                                    SENETEK PLC               (1)

                                    DR. GERLOF HOMAN (2)















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

                             SUPPLEMENTAL AGREEMENT

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

















                                Trowers & Hamlins
                                  6 New Square
                                  Lincoln's Inn
                                 London WC2A 3RP




                                      
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THIS AGREEMENT is made the 3rd day of JULY 1996

BETWEEN

(1)      SENETEK PLC a company  registered in England under Number 1759068 whose
         registered  office is  situated at 23 Palace  Street,  London SW1E 5HW,
         England (the "Company"); and

(2)      DR. GERLOF HOMAN of [1819 Hermitage  Place,  Imperial,  Missouri 63052,
         United States of America] ("Dr. Homan").

WHEREAS

This Agreement is  supplemental  to a service  agreement  dated 11th August 1995
between the Company and Dr. Homan (the  "Service  Agreement").  The parties have
agreed to amend the Service Agreement in the manner hereinafter set out.

NOW IT IS HEREBY AGREED as follows:

1. With effect from the date  hereof the Service  Agreement  shall be amended as
   follows:

                 (a)   In  Clause 2 of the  Service  Agreement  there  shall be
                       inserted a new Clause 2(f) as follows:


                           "(f)     The expression  "Initial  Period" shall mean
                                    the  period  from 1st  October  1995 to 30th
                                    September    1997    and   the    expression
                                    "Additional  Period"  shall  mean the period
                                    from  1st  October  1997 to  30th  September
                                    1998".

                  (b)  Clause 3 of the Service  Agreement  shall be deleted and
                       replaced with the following:

                           "The   employment   shall  be  for  a  fixed   period
                           commencing  on 1st October  1995 and expiring on 30th
                           September   1998   subject   to   prior   termination
                           hereinafter  provided.  Dr. Homan shall be obliged to
                           retire on 30th  September  1998 and the Company shall
                           not  continue  or extend this  Agreement  beyond that
                           date".

                  (c)  There shall be inserted a new Clause 4(h) in the Service
                       Agreement as follows:

                           "At the  commencement  of the  Additional  Period Dr.
                           Homan  shall be  entitled to a salary pro rata to his
                           salary  at the end of the  Initial  Period  and  such
                           salary shall be subject to review in accordance  with
                           Clause  4(a)  (and such  salary  shall be paid to him
                           irrespective  of whether or not the Company  requires
                           Dr. Homan to work for the entire


                                       
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                           46 day period  referred to in Clause  7(a)).  For the
                           avoidance of doubt,  during the Additional Period Dr.
                           Homan  shall  continue  to be  entitled  to all other
                           benefits and entitlements due to him under,  pursuant
                           to or in connection  with this Agreement  (except for
                           the 4 weeks holiday entitlement)".

                  (d)  In Clause 7(a) of the Service  Agreement  there shall be
                       inserted after the words "subject to a maximum commitment
                       of 2.5 days per working  week,  averaged  over a period 
                       of each calendar month" the following words:

                              "during  the  Initial  Period,  and  subject  to a
                              maximum  commitment  of a total of 46 days  during
                              the Additional Period (on such days as the Company
                              and Dr. Homan may from time to time agree),"

                  (e)  In Clause 7(b) of the Service  Agreement  there shall be
                       inserted  after the words "more than the  equivalent  of 
                       2.5 days per working week over any calendar month" the 
                       following words:

                              "during the Initial  Period,  or more than 46 days
                              during the Additional Period".

2.       The parties  hereby agree that the Service  Agreement as amended hereby
         shall continue in full force and effect in accordance with its terms.


SIGNED BY [ P. A. LOGAN    ]        )
for and on behalf of SENETEK PLC    )     /S/ P. A. Logan
in the presence of:                 )
/s/ Karen Goldsmith
Karen Goldsmith
5 Charlton Drive
Biggin Hill, Kent TN1G 3T2


SIGNED by the said                  )
DR. GERLOF HOMAN                    )    /s/ Gerlof Homan
in the presence of:                 )

Signature of Witness:  /s/ Nancy K. Dennigmann
Full name of Witness: Nancy K. Dennigmann

Address:             1714 Sibley
                     St. Charles, MO 63301
Occupation:          Off. Mgr.




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SENETEK PLC
SENESCENCE TECHNOLOGY
23 PALACE STREET, LONDON SW1E 5HW
(Registered Office)
Tel: 0171-828-4800 Fax: 0171-828-8081



                                SERVICE AGREEMENT
                                -----------------

AN AGREEMENT made the 11th day of August 1995 between:

A.        SENETEK PLC whose  registered  office is situated at 23 Palace Street,
          London SW1E 5HW, England ("the Company"), and

B.        DR. GERLOF HOMAN of 1819 Hermitage  Place,  Imperial,  Missouri 63052,
          United States of America ("Dr. Homan").

NOW IT IS HEREBY AGREED as follows:
-----------------------

1.        The  Company  shall  employ Dr.  Homan and Dr.  Homan  shall serve the
          Company with effect from the 1st day of October 1995 as the  Executive
          Chairman of the Board of Directors  which  appointment  shall  include
          liaison  with the  Company's  investors  and  parties  acting on their
          behalf,  with  additional  special  responsibilities  that shall cover
          advising on the development  and marketing of the Company's  products,
          including  in  particular  the  auto-injector  syringe and its various
          applications,  advising on additional  projects and potential products
          that may be of value to the Company and its  subsidiary and associated
          companies,  and liaising with the Company  Secretary,  particularly on
          matters  affecting SEC  compliance,  UK statutory  obligations and the
          distribution  of  investor  information,   upon  and  subject  to  the
          following terms and conditions:

2.       In this Agreement:

         (a)      the  expression  the "Board"  means the Board of Directors for
                  the time being of the Company, and the expression "subsidiary"
                  means a subsidiary (as defined by Section 736 of the Companies
                  Act 1985) for the time being of the Company;

         (b)      the expression  "associated  company"  means, in relation to a
                  company, its holding company (as defined by Section 736 of the
                  Companies Act 1985) or any subsidiary of such holding  company
                  and   the   expression   "associates"   shall   be   construed
                  accordingly;

         (c)      "the Act" means the Employment Protection (Consolidation) Act
                  1978;



                                       
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         (d)      any  reference  to a  statutory  provision  shall be deemed to
                  include  a  reference  to  any   statutory   modification   or
                  re-enactment of the same;

         (e)      references to the singular shall include the plural and vice
                  versa.

3.       The  employment  shall be for a fixed  period of two years  subject  to
         prior termination as hereinafter provided.

4.   (a)  The basic remuneration of Dr. Homan shall be a salary (which shall
          accrue from day to day) at a rate of US$125,000  per annum (subject to
          annual or earlier review at the discretion of the Board).  Such salary
          shall be  payable  by equal  monthly  installments  on the last day of
          every  month  and the  first  of such  payments  shall be made on 31st
          October 1995. In addition to the annual or earlier review  referred to
          above, Dr. Homan's salary shall be subject to an automatic increase on
          the 1st day of  January  of each year by the  percentage  by which the
          cost  of  living  has  increased,   as  determined  by  the  US  Labor
          Department,   over  the  immediately  preceding  twelve  months.  Such
          adjusted salary will then become the "basic remuneration" of Dr. Homan
          for the corresponding year.


     (b)  The Board shall, on an annual basis, determine any additional payment,
          if any, that may be paid to Dr. Homan arising from the  performance of
          his duties.  Without  prejudice to any payment that may be paid to Dr.
          Homan in respect of the fiscal  year ending  December  31,  1995,  the
          first determination shall be in respect of the fiscal year ending 31st
          December 1996.


     (c)  Dr.  Homan  shall  automatically  be entitled  to  participate  in any
          Executive  Share Option Scheme and Profit  Sharing  Scheme that may be
          operated by the Company.


     (d)  Dr. Homan shall (in addition to the usual public and bank holidays) be
          entitled  to four weeks  holiday  with pay per  annum,  to be taken at
          times agreed with the Board.  The  entitlement  to holiday pay accrues
          pro rata through each year of employment hereunder. At the end of each
          year of  employment  hereunder,  or upon  termination  of Dr.  Homan's
          employment  hereunder  for  whatever  reason,  Dr.  Homan shall at his
          option,  be  entitled  to either  payment  in lieu of any  outstanding
          holiday entitlement,  payment being calculated pro rata to Dr. Homan's
          remuneration  under  Clause 4(a) above or to  accumulate  such holiday
          entitlement so that it may be taken at a later date. In addition,  Dr.
          Homan may at any time claim from the Company pay in lieu of his
          holiday  entitlement that has accrued in respect of



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          employment  with the Company prior to the date of commencement of this
          Agreement  but  which,  due to  pressure  of  work,  it has  not  been
          practicable for him to take.

     (e)  In case of illness of Dr. Homan or other cause incapacitating him from
          attending to his duties,  Dr.  Homan shall  continue to be paid during
          such absence  provided that if such absence shall  aggregate in all to
          thirteen weeks in any twenty-six  consecutive  weeks,  the Company may
          terminate the  employment of Dr. Homan  hereunder  forthwith by notice
          given on a date not more than  fourteen days after the end of the last
          of such  thirteen  weeks,  in which event the Company shall pay to Dr.
          Homan  a sum  equal  to six  months  salary  from  the  date  of  such
          termination.

     (f)  Dr.  Homan and his spouse will be entitled to full  medical and dental
          insurance cover, the premiums being payable by the Company, during the
          term of this Agreement.


     (g)  Dr.  Homan  shall  participate  in  all  benefit  plans  available  to
          executives  of the Company;  such plans may include for the benefit of
          Dr. Homan term or other life  insurance  (in a form agreed upon by the
          Board)  providing  death benefits of $500,000 and long term disability
          insurance.

5.       Dr.  Homan's  place of work  shall  be in or  within  reasonable  daily
         traveling distance of the city of St. Louis, Missouri, United States of
         America,  provided  that Dr.  Homan may be  required  to make  business
         visits  elsewhere  from  time to time in  connection  with  his  duties
         hereunder.

6.       The Company shall reimburse Dr. Homan all reasonable hotel,  travel and
         other expenses  exclusively incurred by him in or about the performance
         of his duties  hereunder,  subject to the production of the appropriate
         receipts or vouchers.  In the event that aeroplane  journeys have to be
         undertaken  on behalf of the  Company,  such travel  shall be "business
         class" category, or equivalent standard. Furthermore, if such travel on
         behalf of the  Company's  business  matters  shall exceed a period of 4
         days. Dr. Homan's spouse shall,  upon Dr. Homan's request,  be provided
         with the same facilities at the cost of the Company.

7.       (a)       During the  continuance  of his  employment  hereunder,  Dr.
                   Homan shall,  unless  prevented  by ill health,  devote such
                   time and  attention  to the  business  of the Company as the
                   Board may require,  subject to a maximum  commitment  of 2.5
                   days per working week, averaged over a period  of each 
                   calendar  month,  and shall do all in his power to promote,
                   develop,  and extend the  business                        
                    
                    
                    


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                    of the  Company  and shall at all times and in all  respects
                    conform to and comply with the  directions  and  regulations
                    made by the Board and also shall not,  without the  previous
                    consent  of the  Board,  engage in any other  business  of a
                    similar nature to, or competitive  with,  that carried on by
                    the Company, its subsidiaries or associates.  This shall not
                    be construed so as to preclude Dr. Homan from serving in the
                    capacity  of an  adviser  or  director  to  any  company  or
                    organisation  whose interests are of a dissimilar  nature to
                    those of the Company its  subsidiaries or associates.  There
                    are no fixed  hours of work in  relation  to the  employment
                    hereunder.

        (b)         To the extent that it may  reasonably  be  necessary  for Dr
                    Homan to  devote  more than the  equivalent  of 2.5 days per
                    working week over any calendar month,  Dr. Homan may provide
                    the Company  details of the additional time expended and the
                    nature  of the  work  undertaken  and in such  circumstances
                    shall be entitled in respect of such  additional time worked
                    to  additional  payment  at a rate  pro  rata  to his  basic
                    remuneration in clause 4(a) above.

8.   This Agreement shall not be terminated by any:

        (a)     Merger  or   consolidation   where  the   Company   is  not  the
                consolidating or surviving entity; or

        (b)     Transfer of all or substantially all of the assets of the
                Company.

         In the event of any such merger or  consolidation or transfer of all or
         a substantial  majority of the assets of the Company,  the surviving or
         resulting  entity or the  transferee of the  Company's  assets shall be
         bound  by,  and shall  have the  benefit  of,  the  provisions  of this
         Agreement,  and  the  Company  shall  endeavour  to  take  all  actions
         necessary  to ensure  that such  entity or  transferee  is bound by the
         provisions of this Agreement;  it being understood,  however,  that Dr.
         Homan's  job  title,  duties  and  responsibilities  may be  changed or
         realigned to reflect the fact that the  combination  has resulted,  but
         not changed otherwise, to his detriment.

9.       Subject to the provisions of the Patent Act 1977, if at any time during
         the  continuance  of his  employment  hereunder,  Dr.  Homan  makes  or
         discovers  or  participates  in  the  discovery  of  any  invention  or
         improvement  upon or in addition to an invention which is applicable to
         the  business  for the time  being  carried  on by the  Company  or its
         subsidiaries or associates, the same shall be forthwith communicated by
         him to the Company and shall be the absolute  property of the Company,
         and at the request and  expense of the  Company,  he



                                       4
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        shall give and supply all such information, data, and drawings as may be
        requisite to enable the Company to exploit such invention,  improvement,
        or  addition  to the best  advantage  and shall  execute and do all such
        documents  as may be  necessary or  desirable  for  obtaining  patent or
        similar  protection  for the same in such  part or parts of the world as
        may be  specified by the Company and for vesting the same in the Company
        or as it may direct.

10.     Dr.  Homan  shall  not  (except  in the  proper  course  of  his  duties
        hereunder)   either  during  or  after  the  period  of  his  employment
        hereunder,  divulge to any person and shall use his best  endeavours  to
        prevent  the   publication   or   disclosure  of  any  trade  secret  or
        manufacturing  process  or any  confidential  information  covering  the
        business  or   finances   of  the  Company  or  any  of  its   dealings,
        transactions,  affairs, trade secrets or secret manufacturing  processes
        and  any  similar   confidential   information   governing  any  of  the
        subsidiaries  or  associates,  and all notes and memoranda of such trade
        secrets or  information  made or received by Dr. Homan during the course
        of his  employment  hereunder  shall be the  property of the Company and
        shall be  surrendered  by Dr. Homan to someone duly  authorized  in that
        behalf at the termination of his employment.

11.     Dr.  Homan hereby  covenants  with the Company that he will not within 2
        years after ceasing to be employed hereunder, without the consent of the
        Company in writing  under the hand of a Director  duly  authorised  by a
        resolution of the Board,  directly or indirectly  seek to procure orders
        from or do business  with any person,  firm, or company who, on the date
        of Dr.  Homan  ceasing to be  employed  hereunder  or at any time in the
        twelve  months  prior to that  date,  was a client  or  customer  of the
        Company or its  subsidiary or associated  companies and with whom in the
        course of his  employment  Dr. Homan shall have had  dealings,  provided
        always that nothing in this clause contained shall be deemed to prohibit
        the  seeking  or  procuring  of orders or the doing of  business  not in
        direct or indirect competition with the business or businesses aforesaid
        or any of them.

12.     The Company shall provide Dr. Homan with a motor car  appropriate to his
        status for his  business and  personal  use.  The Company  shall pay all
        taxation,  insurance  premiums,  maintenance and repair expenses and for
        all petrol,  oil and other running expenses thereof.  Dr. Homan shall at
        all  times  conform  to all  regulations  which may from time to time be
        imposed  by the  Company  with  respect to motor  cars  provided  by the
        Company for use by its personnel.


13.     The  employment of Dr. Homan  hereunder may be determined by the Company
        forthwith  if  Dr.  Homan  is  guilty  of any  gross  default  or  gross
        misconduct in connection  with or affecting the business of the Company,
        or in the event of any material



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        or  substantial  breach  or  non-observance  by Dr.  Homan of any of the
        stipulations herein contained.

14.     Notwithstanding  the terms and conditions of this  Agreement,  Dr. Homan
        shall be entitled to resign  without  incurring  any penalty upon giving
        the Company 24 hours  notice if he has bona fide  reasons for  believing
        that any party  appointed  to the Board of  Directors or to an executive
        position is or may be  prejudicial to the interests of the Company or to
        himself and, in addition under any circumstances  where he believes that
        the identification and development of any product or the purchase of any
        organisation  or its  assets  is  likely  to  have  similar  prejudicial
        effects.

15.     In the event of any dispute or  controversy  arising from the Agreement,
        the Company shall pay all reasonable legal fees incurred by Dr. Homan in
        the settlement of such dispute or  controversy,  provided that they have
        been properly and necessarily incurred by Dr. Homan.

16.     This  Agreement  shall take effect from 1st October  1995 and shall from
        that date  supersede  any and all other  agreements,  either  oral or in
        writing and, in particular, Dr. Homan's agreement with the Company dated
        the 10th day of December 1993 and his agreement dated 10th December 1993
        with the Company's  wholly owned subsidiary MEIS Corporation (a Delaware
        corporation)  for which,  in both cases, he undertakes to relinquish all
        rights and  entitlements  without any claim  against the Company or MEIS
        Corporation for such relinquishments,  and contains all of the covenants
        and  agreements  between the parties with respect to such  employment in
        any manner whatsoever. Each party to this Agreement acknowledges that no
        representations,   inducements,   promises,   or  agreements  orally  or
        otherwise,  have been made by any party,  or anyone  acting on behalf of
        any party,  which are not embodied  herein,  and that no other agreement
        shall be binding or valid.  Any  modification  of this Agreement will be
        effective only if it is in writing and signed by both parties hereto.

17.     This  agreement  shall be construed  and governed by the laws of England
        and Wales and the  parties  hereby  submit  to the  jurisdiction  of the
        English Courts.

18.     Dr. Homan's period of continuous  employment with the Company  commenced
        on 1st September 1988.

19.     There are no  pension  entitlements  under this  Agreement.  There is no
        contracting out certificate in force in respect of this employment.



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20.      There are no disciplinary or grievance rules in place in respect of Dr.
         Homan's employment.  Dr. Homan may raise any grievance or concern about
         any disciplinary matter with the Board.


SIGNED BY
for and on behalf of
SENETEK PLC
presence of                 }
 /s/                                          /s/ P.A. Logan  
-----------------------------               -----------------------
Witness                                     P.A. Logan
                                            Director
23 Palace Street
-----------------------------
London SW1
-----------------------------



SIGNED by the said Dr. Gerlof }
Homan in the presence of      }
/S/ Nancy Dennigmann                         /s/ Gerlof Homan
-----------------------------               -----------------------
Witness                                     Gerlof Homan
1714 Sibley
-----------------------------
St. Charles, MO 63301
-----------------------------




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