FDA places clinical hold on Tysabri's drug class

GlaxoSmithKline said US regulators had halted clinical trials on multiple sclerosis drugs in the same class as recently withdrawn treatment Tysabri, including its experimental product '699.

Tysabri, which was developed by Ireland's Elan Corp and US-based Biogen Idec, was pulled from the market after a patient died from a rare and often fatal infection of the central nervous system.

Both Tysabri and '699, which GSK is developing with Japan's Tanabe Seiyaku, work by inhibiting alpha-4 integrin (VLA-4), a substance implicated in the disease.

"The FDA has taken the precautionary measure of placing a clinical hold on investigational new drugs in the alpha-4 integrin antagonist class being tested on human subjects, which includes '699," a GSK spokesman said.

GSK said it was not aware of any problems with its drug similar to those experienced with Tysabri.

"Whilst '699 has the same molecular target as natalizumab (Tysabri), '699 is chemically unrelated to natalizumab," the spokesman said. GSK and Tanabe's drug is taken as a pill while Tysabri is given as a monthly infusion.

GSK had been expected to report phase II trial results with '699 by the end of this year, ahead of an anticipated filing for regulatory approval in 2008.

Antisense implications

Australia's Antisense Therapeutics (ASX:ANP), which last week halted the Phase IIa trial of its lead drug candidate for multiple sclerosis, ATL1102, also targeting VLA-4, has said that the ruling has no implications for ATL1002 studies.

"It only applies to studies in the US," said Antisense chief executive Mark Diamond. "We'll still continue as planned to put the advisory group together and consult with them."