BioWorld International Correspondent

LONDON - Antisoma plc's share price was halved Monday after the company announced its lead product, R1549, failed in a Phase III ovarian cancer trial - survival of R1549-treated patients was no better than patients in the comparative arm.

Glyn Edwards, CEO, told BioWorld Today: "Obviously we are very disappointed and disappointed for cancer patients as well. But that's the way this business goes. There was no significant difference in survival and no trends that we would consider [significant enough] to take the product forward."

R1549 is partnered to F. Hoffmann-La Roche Ltd., of Basel, Switzerland, and William Burns, head of the pharmaceutical division at Roche, said, "We remain committed to our long-term relationship with Antisoma, which is based on multiple products."

Edwards said he was surprised at the outcome of the trial, given the results R1549 achieved in Phase II. "We have no explanation, but that's why the regulators have you carry out these big Phase III trials," he said.

R1549, an antibody-targeted radiotherapeutic, also is in a Phase II study for the treatment of gastric cancer. Its failure leaves Antisoma with three other compounds in the clinic, with the most advanced, AS1404, a small-molecule vascular-targeting agent, expected to begin a series of Phase II combination studies later this year.

"This takes out our most advanced product, so it will have an effect on the [company's] valuation." Edwards said. "But [we're] not like other companies that go under when they have products fail in Phase III because we've got a strong cash position."

At the end of March, the company had £40 million (US$71.5 million) in cash. Antisoma shares (LSE:ASM) fell 24.5 pence Monday, or 55.1 percent, to close at 20 pence.

Edwards does not believe the failure will undermine Antisoma's relationship with Roche, pointing to the multiproduct, multiyear collaboration comment made by Burns. Roche has put more emphasis on R1550, a humanized monoclonal antibody in Phase I for the treatment of breast cancer. "The failure of R1549 has no impact on R1550 because it is a different mechanism of action and a different disease area," Edwards said.

London-based Antisoma signed its deal with Roche, which has a total potential value of $500 million, in November 2002. The agreement covered four products then in clinical trials and six in preclinical development. One product, AS1405, in Phase I for the treatment of glioma, was excluded from the deal and is unpartnered.

"Our next most advanced product may only be starting Phase II," Edwards said, "But Phase II is not as long as Phase III, and when we move into Phase III we get significant milestones from Roche and they take on development costs."

Analysts have singled out the Phase III results for R1549 as an event that would impact overall sentiment toward the UK biotech sector, but Edwards said: "Rationally, there shouldn't be a knock-on to the rest of the sector. This is not a general issue, it is a company issue."

Despite the fall in Antisoma, shares in 10 other biotechnology companies held steady in the first hour of trading on Monday.

Edwards said Antisoma now will move onward and upward, "though from a different base." R1549 had been handed over to Roche and so the failure will not affect what Antisoma employees are doing. The company raised £15.2 million in a placing in December to fund the acquisition of new products and intensify development of existing programs.

Antisoma licensed R1549 from Imperial Cancer Research Technologies (now Cancer Research UK) in 1996. Phase II studies indicated a 75 percent 10-year survival rate for R1549-treated women who go into remission, compared to a 30 percent 10-year survival rate for those who go into remission following conventional treatment.

Recruitment of the Phase III trials began in 1998, and the product was expected to receive approval in 2002. But in June 2001 the FDA told Antisoma to increase the number of patients in the trial. The completion point of 116 deaths in the 420-patient trial was predicted previously for the second half of 2004.