March 9, 1999
Via Fax

Anders Hove
Biotech Target S.A.
Swiss Bank Tower
Panama 1
Republic of Panama

Dear Anders:

Pursuant to Section 4.1 of the Purchase and Registration Rights Agreement
between Algos Pharmaceutical Corporation ("Algos") and Biotech Target S.A.
("Biotech"), dated November 9, 1998, Algos agreed to file a Registration
Statement for the shares of common stock sold to Biotech Target S.A. under such
agreement on or prior to March 9, 1999. Biotech has agreed to waive this
registration requirement until March 12, 1999. In the event that such
Registration Statement is not filed on or prior to March 12, 1999, this waiver
shall be null and void, and Biotech will not be deemed to have waived any rights
under the Purchase and Registration Rights Agreement. This waiver concerns only
the date of filing of such Registration Statement and Biotech shall not be
deemed to waive any other rights under the Purchase and Registration Rights
Agreement.

Sincerely yours,



/s/ John W. Lyle

John W. Lyle
President and Chief Executive Officer

I confirm that Biotech Target S.A. has
agreed to the foregoing waiver:



By: /s/ A. HOVE
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Printed Name: A. Hove
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Title: Signatory Authority
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Date: 9 March, 1999
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