By Randall Osborne

Two years after extending their collaboration to develop genetic code-blocking technology, Glaxo Wellcome plc and Gilead Sciences Inc. have ended the deal.

"It was pretty much a joint decision," said Lana Lauher, spokeswoman for Foster City, Calif.-based Gilead. "Both we and Glaxo have programs that are significantly larger than the antisense [program]."

For example, Gilead's reverse transcriptase inhibitor, Preveon (adefovir dipivoxil), is in multiple Phase III trials for AIDS. The company last week reported one study showing the drug demonstrated antiviral activity in Phase II/III trial patients who had developed resistance to the common HIV drugs AZT (zidovudine) and 3TC (lamivudine).

Glaxo last week submitted new drug applications to the FDA for AIDS and hepatitis B drugs.

In the code-blocker deal, Gilead got about $20 million in research and development payments over the course of the collaboration with London-based Glaxo, which also purchased an $8 million equity stake in Gilead in 1990.

The partnership was extended in 1996 for five years, but. Glaxo had an option to end the deal after two years. (See BioWorld Today, March 28, 1996, p. 1.)

"They were modest payments, about $3 million a year," Lauher said. "Those will be ending, but we'll no longer have corresponding expenses either." She said the company will suffer no financial impact from the deal's termination.

The code-blocker program included development of antisense and triple-helix compounds. Antisense compounds bind to a specific portion, or string, of RNA.

Triple-helix compounds are designed to bind to a portion of double-stranded DNA. The principle behind code blockers is that a chain of nucleotides — the building blocks of RNA and DNA — could be designed to bind to specific portions of DNA or RNA and inhibit the production of disease-causing proteins.

With the end of the collaboration, each company retains rights to any technology developed jointly.

"Even though we were jointly doing work in the area, Glaxo may have made some advancements on its own and we may have done the same," Lauher said. Each company keeps its rights to those advancements.

Gilead is discussing the code blocker technology with other potential collaborators.

"We will no longer be doing that research here, but we still think it's an important, promising technology," Lauher said.

Gilead's stock (NASDAQ:GILD) closed Friday at $34.625, up $0.875. *