Genex lost a major G. D. Searle & Co. contract.

The Rockville, Md., biotechnology firm said its contract to produce ingredients for Searle’s popular sweetener, aspartame, will not be renewed when it expires Oct. 31. Genex has often been listed as one of the nation’s five most promising biotechnology companies. Its sales to Searle in 1984 accounted for $20.2 million of Genex’s product sales of $20.6 million and 58% of the company’s total revenue of $34.8 million. Both companies declined to comment on why the contract will not be extended.