<PAGE>   1
                                                                   EXHIBIT 10.47

                               LEASEHOLD CONTRACT


                                     BETWEEN


THE LESSOR:                    BASLER KANTONALBANK
                                 SPIEGELGASSE 2
                                  CH-4002 BASEL
                                   SWITZERLAND


                                       AND


THE LESSEE:                 DISCOVERY TECHNOLOGIES AG
                                  C/O BURECO AG
                                   STADTWEG 4
                               CH-4310 RHEINFELDEN
                                   SWITZERLAND


CONCERNING:           OFFICE AND LABORATORY PREMISES IN THE
                             REAL-ESTATE PROPERTY AT
                                GEWERBESTRASSE 16
                                CH-4123 ALLSCHWIL


<PAGE>   2
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 2 of 14
--------------------------------------------------------------------------------

1.    Preamble

      The parties agree on the rent for the office and laboratory premises in
      the property at Gewerbestrasse 16 in Allschwil. The right of
      codetermination for additional tenants, as well as intentions for the
      innovation centre, will be set forth in a separate agreement. The basic
      rent forms payment for the assignment of these premises in their (present)
      "rough state" (gross rent). For her(1) requirements the Lessee needs the
      installation of additional technical appointments (energy, ventilation,
      laboratory installations etc.). The parties shall plan this extension work
      jointly. The Lessor shall assume the task of obtaining the requisite
      planning permission and the execution of the extension work for own
      account. The Lessee shall reimburse this extra investment on the part of
      the Lessor by means of additional rent (extension rent). The parties wish
      to adhere to the following schedule(2):

      20.06.1997        Signing of the leasehold contract Availability of layout
                        and initial description of extension work

      23.07.1997        Submission of building application

      01.09.1997        Granting of planning permission

      01.02.1998        Completion of extension work on part of Lessor Handover
                        of leased property.

1.1   Suspensory condition

      This leasehold contract is concluded on the suspensory condition that
      planning permission is finally granted for the above-mentioned additional
      extension work (subitem 2.4.b).

      In the event of such planning permission not having been granted and made
      available by 3 November 1997, this leasehold contract shall lapse unless
      the Lessee declares her agreement in writing to a deferral of this time
      limit to a later juncture. In this case, each party shall bear the costs
      incurred by it to date. (In particular, the Lessor shall bear the planning
      costs of completion by the Lessee.) No further mutual obligations shall
      otherwise exist.

2.    Leased property

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

(1)   Translator's note: The use of the feminine form here may indicate either a
female lessee or simply a corporate lessee in the form of a company.

(2)   Translator's note: Please note that all figures in this text should be
checked, as the quality of the source document was not sufficiently clear to be
100% certain of certain digits!


<PAGE>   3
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 3 of 14
--------------------------------------------------------------------------------

2.1.  The Lessor shall assign to the Lessee the following premises in the
      previously mentioned property for use on a leased basis:

      Office and laboratory premises on the 4th floor, approx. 1,330 sq.m.
      Archive rooms on the 2nd sub-basement floor, approx. 60 sq.m. 15
      underground parking spaces

2.2   The Lessee is entitled in building no. 16 to joint use of the following
      communal and collective parts, premises, rooms and appointments under the
      terms of the house rules:

      -  Staircase

      -  Passenger lifts and goods lift

2.3   The rented premises according to subitem 2.1 are set out in the floor plan
      enclosed.

      The plan shall be signed by both parties and shall form part of this
      contract.

2.4   The Lessor shall assign the property to the Lessee with extensions
      specific to the Lessee. Currently, the building has not yet been extended.
      The following three different stages of extension have been finalized:

      a)    Shell construction (gross rent)

            supporting structure (floors, supports, ceilings) facade with
            windows and sunbreakers staircase, lift, toilet facilities in the
            core zone detailed description as per appendix

      b)    Lessee-specific extension provided by the Lessor (extension rent)

      The description of the extension shall be detailed more precisely in the
      mutual agreement on completion of the contract; the following shall be
      used as a basis at the time of completion of contract:

      Walls, doors:     -  Offices: partitions, panel component system

                        -  Labs: plasterboard partition walls with PVC
                           wallpapers

      Floors:           -  Offices: double floors, textile flooring, colour as
                           per collection

                        -  Labs: double floors, PVC flooring, colour as per
                           collection

                        -  antistatic, conductive

      Ceilings:         -  Offices, reception, conference rooms, corridor area,
                           suspended ceiling cladding made of mineral fibre
                           panels, lattice system


<PAGE>   4
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 4 of 14
--------------------------------------------------------------------------------

                        -  Labs: rough concrete ceilings, painted

      Ventilation:      -  Offices: mechanical ventilation across floors and
                           ceilings, incl. cooling

                        -  Labs: mechanical ventilation, visibly mounted on
                           ceiling, chapel exhaust air removal(3) (as per
                           EKAS(4) guidelines), incl. cooling

      Electrical plant: -  Ducting from main distribution to subdistribution in
                           labs and to sockets in offices. Ceiling illumination

                        -  Cable chutes in labs

                        -  Doorbell system and interphone

                        -  Fire alert system

      Sanitary, media:  -  Hot and cold water connection, waste water connection
                           (WAS(5), labs), separate system to sub-basement
                           floors

      Telephone:        -  Connections available on 4th floor at lift landing
                           place.

      Immediately after signing this leasehold contract the parties shall
      expedite detailed planning together with the planning company commissioned
      and submit the building application in due course. The Lessor shall assume
      the costs of these additional extensions up to a maximum amount of
      1,800,000 Swiss francs (planning, costing, planning permission procedure,
      execution). Works and appointments exceeding this limit shall be borne by
      the Lessee and are subject to prior acceptance by him in writing.

      c)    In particular, items not included in the extension and additional
            building by the Lessor, and hence to be assumed by the Lessee, are:

               -  Electrical installations in the labs from the subdistribution
                  system

               -  Telephone switchboards with internal cabling

               -  Computer installation and internal cabling/trunking as well as
                  installations for additional means of communications

               -  Miscellaneous lessee-specific, special-purpose extensions such
                  as chapels, lab furniture, cold-storage cells, clean rooms,
                  washing benches in labs, gas installations, compressed air,
                  built-in cupboards corridor area

               -  Pretreatment or disposal of contaminated waste water (WAS
                  connection available)

               -  mobile fire extinguishing gear.

      The Lessee shall submit the plans to the Lessor for written permission.

--------------
(3)   Translator's note: Technical term not found. This is merely a literal
translation.

(4)   Translator's note: EKAS stands for the "(Swiss) Confederate Coordination
Commission for Occupational Safety", under SUVA (the "Swiss Workmen's
Compensation Institute").

(5)   WAS stands for the Water Delivery Regulations.


<PAGE>   5
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 5 of 14
--------------------------------------------------------------------------------

      Any permits, authorization and consent needed apart from building
      permission for structural additions (operating authorization, work permits
      etc.) shall be the concern of the Lessee and shall be submitted with the
      building application. They have no influence on the continuance of the
      present leasehold contract.

2.5   Until 30 June 2000 the Lessee shall have a leasing option on the remaining
      premises on the 4th floor of building 14 measuring in the region of 650
      sq.m. Gross rent conditions as per graduated rent in item 4.1.

3.    Term of tenancy

3.11  Start of tenancy

      Tenancy shall commence five months after final and effective building
      authorization has been granted, foreseeably on 1 February 1998 and no
      later than 1 June 1998.

3.12  Term of tenancy, extension of contract

      The tenancy shall be concluded for an initial fixed contractual duration
      of 10 years until 31 January 2008.

      On expiry of the first contractual period the contract shall be extended
      by an additional fixed contractual term of five years each time, unless
      terminated by registered letter at least 12 months prior to expiry.

3.13  Notice

      On expiry of a fixed contractual period the tenancy can be terminated at
      12 months' notice to the end of January, the first time being end-January
      2008.

3.2   End of lease

3.21  Termination shall be deemed to have taken place promptly if deposited with
      the recipient or in his sphere of control (notice of collection in
      letterbox or post-office box) no later than the last day prior to the
      beginning of the period of notice.

      The Lessor shall use the official form to serve notice.

3.22  The rent may be adjusted to prevailing market conditions with a
      notification period of 15 months to the end of the fixed contractual
      period or above-mentioned extension period.

3.3   Unscheduled termination of the leasehold contract


<PAGE>   6
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 6 of 14
--------------------------------------------------------------------------------

3.31  If the Lessee wishes to end the leasehold contract without observing the
      agreed time limits or deadlines, he shall advise the Lessor of this by
      registered letter.

3.32  The Lessee is at liberty to propose to the Lessor a reasonable and solvent
      substitute tenant to enter into the contractual relationship.

3.33  Unless otherwise agreed, the Lessor shall also take whatever measures are
      necessary and appropriate to enable him to re-let the rented premises as
      soon as possible.

3.34  The Lessee shall be liable for the rent as well as incidental and
      subsidiary costs and for any other duties incumbent upon him as Lessee
      until such time as the rented premises have been re-let, and at longest
      until the next contractual term of notice, and for this purpose shall
      furnish sureties in addition to those in subitem 14.1. below.

4.    Rent

      The rent is made up of a basic rent (gross rent) (with graduation for the
      office and laboratory premises) and an extra rent for the total duration
      of the lease for the additional building work by the Lessor (extension
      rent).

4.1   The rent is agreed as follows:

      Gross rent (shell) in accordance with subitem 2.4 a) for the bare premises
      (without lessee-specific extensions), graduated:

<TABLE>
<CAPTION>
<S>                                              <C>                 <C>
         |X| During 1st and 2nd lease years      CHF/m(2)/yr          75.00
         |X| During 3rd lease year               CHF/m(2)/yr          85.00
         |X| During 4th lease year               CHF/m(2)/yr         100.00
         |X| During 5th to 10th lease years      CHF/m(2)/yr         125.00
</TABLE>

      Extension rent for lessee-specific extensions provided by the Lessor in
      accordance with subitem 2.4 b) throughout the duration of the lease:

<TABLE>
<CAPTION>
<S>                                 <C>                       <C>
         |X| Estimate               CHF/m(2)/yr               approx. 125.00
</TABLE>

      The extension rent shall be finalized once work measurement and billing
      become available. Amortization of the extension costs shall be fixed at 15
      years. The calculated estimate comprises 6.5% for amortization and 2% for
      the average rate of interest, or 8.5% in total.

      Extension costs: 1,800,000 million francs: 1,250 sq.m. = CHF 1,440/sq.m.,
      8.5% of which = CHF 125/m(2)/yr.

      The amount of CHF 125/m(2)/yr shall apply as a ceiling for the extension
      rent.


<PAGE>   7
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 7 of 14
--------------------------------------------------------------------------------

4.2   Accordingly, upon commencement of the lease, the annual rent for the first
      two years will foreseeably total: CHF 270,400.00 made up as follows:

<TABLE>
<CAPTION>
<S>                                   <C>         <C>                    <C>
         |X|  Offices and labs:       1,330 sq.m. @ CHF/m(2)/yr 75.00    CHF  99,750.00

         |X|  Extensions by Lessor    1,250 sq.m. @ CHF/m(2)/yr 125.00   CHF 156,250.00

         |X|  15 parking spaces                   @ CHF 80/month         CHF  14,400.00

         |X|  Total                                                      CHF 270,400.00

         payable in quarterly instalments of                             CHF  67,600.00
         excluding: subsidiary costs, quarterly
         (1,330 sq.m. x CHF 6/m(2)/yr), on account                       CHF   1,995.00

         Total payable in advance quarterly                              CHF  69,595.00
</TABLE>

4.3   The rent is payable in advance, no later than the first day of the rental
      quarter (as due date).

5.    Rent adjustments

5.1   The gross rent for offices and laboratories (in accordance with subitem
      4.1) and parking spaces is based on the [Swiss] national consumer price
      index. As of April 1997 this stood at 104.1 points. If the national
      consumer price index is subject to any change after the commencement of
      the lease or since the last adjustment, then irrespective of the fixed
      contractual duration the gross rent can be adjusted to the change in this
      index once a year on 1 February, the first time being in the fifth year of
      the lease. However, the amount may not fall short of the gross rent in
      subitem 4.1.

      The Lessee shall be notified of the change in rent in writing and on the
      official form, giving one month's notice.

5.2   Where value-enhancing applications or investments are undertaken during
      the fixed contractual period, these shall be added to the basic rent in
      accordance with subitem 4 in keeping with trade custom. Notification of
      rent adjustments effected on the grounds of value-enhancing applications
      shall be given on the official form, giving one month's notice.

6.    Heating and subsidiary costs

6.1   The Lessee shall be charged the following heating and subsidiary costs on
      top of the rent:

         |X| Heating and hot water



<PAGE>   8
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 8 of 14
--------------------------------------------------------------------------------

         |X| Operation and maintenance of ventilation plant

         |X| Water consumption, charges and wastewater treatment systems

         |X| Operating and maintenance costs incl. service subscription for
             passenger and goods lifts

         |X| General lighting

         |X| Caretaker's services (salary, social security payments, janitorial
             materials)

         |X| Refuse disposal/refuse container

         |X| Any security and surveillance services or alarm system operations

         |X| 3% of the total subsidiary costs by way of administration fee.

6.2   The heating and subsidiary costs are broken down as follows (unoccupancies
      shall be chargeable to the Lessor):

6.21  Energy processing costs (especially heating and hot water costs):

         |X| Basic and hot water costs to be divided up according to the size of
             the business premises (square metres).

         |X| Heating costs, conversely, to be allocated according to individual
             meters.

6.22  Neutral costs (such as caretaker, general power, security services, alarm
      systems etc.) are to be divided up according to the size of the premises
      rented (square metres).

6.23  Costs dependent on consumption (e.g. water rate, wastewater and refuse
      charges, lift operation costs etc.) are to be allocated according to the
      size of the rented premises (square metres).

6.3   The Lessee shall remit half-yearly on-account payments towards the
      above-mentioned subsidiary costs, with the Lessor drawing up and providing
      the Lessee with a subsidiary cost sheet on 30 June of every year. The
      subsidiary cost sheet shall be deemed to have been approved if not queried
      in writing within 30 days of delivery (as postmarked). Upon expiry of the
      above 30-day deadline for queries all subsequent claims or repayments
      shall fall due.

      If the tenancy is ended during the accounting period, the Lessee shall
      have no claim to a subsidiary cost sheet ahead of the scheduled time.

6.4   The total power consumption for the leased property shall be chargeable to
      the Lessee. Charges and dues generated exclusively by the Lessee's
      business operations shall be borne by the Lessee even if levied from the
      Lessor.

7.    Handing-over of the leased property

7.1   The Lessor shall hand over the leased property in a clean state as
      contractually stipulated, issuing the necessary keys no later than the
      date mentioned in subitem 3 in accordance with local practice. Where the
      aforementioned date falls on a


<PAGE>   9
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                   Page 9 of 14
--------------------------------------------------------------------------------

      Saturday, Sunday or bank holiday, hand-over shall take place on the
      following working day at the latest.

7.2   The Lessee shall report all defects ascertained to the Lessor within 30
      days of commencement of the lease by registered letter. If he fails to do
      so, the leased property shall be assumed to have been transferred to him
      in the contractual state.

8.    Utilization of the leased property / duty of care

8.1   The rented space is at the Lessee's disposal for use as offices and a
      laboratory.

8.2   The Lessee undertakes not to use the leased property for any purpose other
      than that contractually provided for. Any change in ordinary use shall
      require the prior consent of the Lessor in writing.

8.3   Where machinery and heavy furniture are installed, the static data of the
      building shall be taken into consideration. The Lessee shall satisfy
      himself in advance of the permissible floor load.

8.4   The operating instructions stipulated by the manufacturers shall be
      observed when using the lift.

8.5   The Lessee may have extra keys made only with the written consent of the
      Lessor.

      In the event of keys being lost, the Lessee shall bear the costs of
      replacing them and any closure systems that require replacing.

8.6   In making use of the leased property the Lessee undertakes to employ care
      and consideration, particularly with regard to neighbours. The house rules
      shall form an integral part of this contract.

8.7   In very general terms the Lessee is obliged to take all appropriate
      measures to avoid or reduce noise, vibrations, smells and other
      immissions. The Lessee is liable to the Lessor for any damage (incl.
      claims by third parties) incurred by him from immissions exceeding
      customary and authorized use.

8.8   The Lessee shall be fully liable to pay damages for violating his duty of
      care. If, despite written admonition on the part of the Lessor, the Lessee
      continues to violate his duty of care or consideration, the Lessor is
      further at liberty to annul the present leasehold contract in accordance
      with Art. 257f of OR(6).

--------------
(6)   OR stands for the Swiss Code of Obligations, the 5th Part of the Act of 30
March 1911 to Amend the Swiss Statute Book.



<PAGE>   10
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                  Page 10 of 14
--------------------------------------------------------------------------------

9.    Upkeep

9.1   Lessor's duty of upkeep / improvements

9.11  Maintenance work on the leased property shall be incumbent on the Lessor.

9.12  Bearing in mind the interests of the Lessee, the Lessor shall at all
      times, unimpeded, be entitled to carry out repairs and renovations to the
      leased property and appurtenant appointments in accordance with Art.
      2.4a+b, provided that notice on the tenancy has not been given. The Lessee
      shall be given prompt notification in writing of major rebuilding work and
      new installations. Any claims on the part of the Lessee shall conform to
      Art. 260 of OR.

9.2   Lessee's duty of upkeep

9.21  Any improvement and repair work made necessary by normal use and not
      exceeding CHF 500 in any one instance shall be chargeable to the Lessee.
      In particular, this shall include the replacement of electrical fuses as
      well as shattered panes of glass, maintenance of electrical switches and
      sockets, gas and water taps, drains and door locks etc.

9.22  The Lessee shall be responsible for the upkeep of all structural
      modifications effected by him in accordance with Art. 2.4 c and
      appliances.

9.23  Defects which the Lessee is not responsible for remedying shall be
      notified to the Lessor immediately. Failure to notify these shall render
      the Lessee liable for any damage arising therefrom.

10.   Structural modifications

10.1  Modifications and renovations to and in the rented premises, the mounting
      of shutters, company signs or advertising devices etc. are permitted only
      with the Lessor's prior consent in writing. The Lessee is obliged to
      execute such work professionally. The fitting of devices to the facade
      (advertising signs and hoardings, shutters, display cases, aerials etc.)
      shall be in keeping with the leased property and the surroundings.

10.2. The Lessee's appointments (Art. 2.4c) shall remain his property. The plans
      and designs as well as the costing estimates shall be presented to the
      Lessor for his written permission.

10.3. It shall be incumbent on the Lessee to secure any official authorizations
      needed. The Lessee further undertakes to take out the customary building
      insurance policies and to bear the costs thereof and defray any extra
      premium on property and non-life insurance.


<PAGE>   11
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                  Page 11 of 14
--------------------------------------------------------------------------------

10.4. The Lessor is entitled to demand from the Lessee security or a financing
      statement for the foreseeable structural costs entered into by the Lessee,
      particularly with a view to promptly averting any builders' and
      tradesmen's right of lien.

      If third-party claims are made on the Lessor for immissions arising as a
      result of the Lessee's structural modifications or appointments, the
      Lessee shall be liable to compensate the Lessor for the damage sustained.

10.5  Upon conclusion of the lease the Lessee shall restore the premises to
      their original condition at his own cost or by mutual arrangement assign
      his appointments to the Lessor free of charge in accordance with subitem
      2.4c.

11.   Subletting / cession of the leasehold contract.

      Partial or full subletting of the rented premises (or cession of the
      leasehold contract) shall require the consent of the Lessor in writing.

12.   Lessor's right of access

12.1  The Lessor or his representative shall be entitled to enter the leased
      property with a view to protecting his rights (re-letting, sale, repairs,
      renovations etc.) during the customary hours of business after giving 48
      hours' notification in advance.

12.2  In the absence of the Lessee the keys shall be kept available.

13.   Insurance

13.1  The Lessor shall take out the compulsory fire insurance, property-owner's
      liability insurance and property water-damage insurance.

13.2  The Lessee shall bear the risk of damage to or loss of his appointments,
      his furniture or his goods, particularly as a result of fire, explosion,
      water, burglary or theft. He undertakes to take out an employer's
      liability insurance policy.

13.3  The Lessor assumes no liability for any display windows, showcases, panes,
      glass panelling, company signs, luminous signs etc. Adequate insurance
      against such damage shall be the concern of the Lessee.

14.   Furnishing of security


<PAGE>   12
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                  Page 12 of 14
--------------------------------------------------------------------------------

14.1  Within 14 days of signing the contract the Lessee shall furnish for the
      entire duration of the lease + 3 months the following securities in the
      form of a bank guarantee for the following amount:

      CHF  60,000.00  until the availability of planning permission
      CHF 140,000.00  from the availability of planning permission.

      In the event of the Lessor asserting legal claims against the Lessee
      arising from the tenancy, the bank guarantee must remain valid until the
      settlement of the legal dispute. In this case the Lessor must advise the
      bank.

14.2  Once planning permission becomes available, the Lessee shall furnish a
      financing statement for the extension work by the Lessee in accordance
      with subitem 2.4c.

15.   Return of the leased property.

15.1  The Lessee shall hand over the rented premises, complete with all keys, no
      later than the last day of the lease term, by 12 noon. Any additional keys
      made shall be handed over to the Lessor without compensation. Where the
      deadline for return falls on a Saturday, Sunday or bank holiday, the
      premises shall be returned on the following working day (by 12 noon).

15.2  When surrendering the leased property, the Lessee shall again remove the
      completed extensions executed by the Lessee without compensation. The
      additional extensions provided by the Lessor (subitem 2.4b) shall remain
      part of the leased property. Where installations made by the Lessee
      (subitem 2.4c) are able to remain in the leased property with the consent
      of the Lessor, the Lessor shall pay no compensation for such.

15.3  Refurbishment and cleaning work to be undertaken by the Lessee shall be
      commenced on time so as to be completed by the end of the tenancy.

      Where, for reasons to be supported by the Lessee, the leased property
      cannot be handed over to the successor on time, the Lessee shall be liable
      to the Lessor for any damages arising as a result.

15.4  When surrendering the property, the Lessor--preferably in the presence of
      the Lessee--shall provide a restitution log, recording the state of the
      leased property and, in particular, defects and damage for which the
      Lessee is to pay. The log shall be signed by the Lessee or delivered to
      him without delay by registered letter. If it is not possible for the
      Lessee to sign the log, the Lessor can also have a record drawn up by an
      official expert at the Lessee's expense. Again, this is to be brought to
      the attention of the Lessee by registered letter. If the Lessee raises no
      objection within 30 days of delivery of the log, it shall be deemed to
      have been approved by him.


<PAGE>   13
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                  Page 13 of 14
--------------------------------------------------------------------------------

      Hidden defects can be asserted by the Lessor subsequently. However, he
      must inform the Lessee thereof by registered letter immediately after
      ascertaining such.

16.   Final provisions

16.1  Contractual amendments

      Any amendment to the contract shall be made in writing.

16.2  Postal domicile

      Until revoked by registered letter to the other party, the following
      addresses shall be valid as the effective postal domiciles of the parties
      to the contract within the meaning of this contract:

<TABLE>
<CAPTION>
<S>                                  <C>
      Lessee's postal domicile:      Stadtweg 4, CH-4910 Rheinfelden

      Lessor's postal domicile:      Spiegelgasse 2, CH-4002 Basel
</TABLE>

16.3  Legal venue

      For all disputes arising from this leasehold contract the location of the
      rented property shall be held to be the legal venue.

16.4  Entry in the land register

      The Lessee has the right to have this leasehold contract entered in the
      register at his own expense for the duration of the contract.

16.5  Residential property

      In the event of the property being divided up into freehold flats, the
      Lessor is prepared to guarantee the Lessee a purchase option for the
      duration of the tenancy.


<PAGE>   14
Leasehold contract BKB/Discovery Technologies AG, Gewerbestrasse 14 - 2nd floor,
CH-4123 Allschwil                                                  Page 14 of 14
--------------------------------------------------------------------------------

The above leasehold contract to be drafted and signed in triplicate.


Basel, 18 June 1997
                                          /s/ Rheinfelden, 19.6.97
                                          -------------------------------------

The Lessor:                               The Lessee:
Basler Kantonalbank                       Discovery Technologies AG

                                          /s/ illegible
                                          -------------------------------------
/s/ illegible                             /s/ illegible
-------------------------------------     -------------------------------------


17.   Appendix:

      Floor plan recording rented premises.