U.K. reinstates Tysabri as multiple sclerosis therapy

Tysabri has been reinstated for use by select multiple sclerosis sufferers in Britain, where it competes with Teva Pharmaceuticals' (TASE, Nasdaq: TEVA) Copaxone as a therapy for the incurable neuri-degenerative disease.

The drug, developed by Biogen Iden in collaboration with the Irish drug company Elan Pharmaceuticals, had been launched in November 2004. Mere months later, in February 2005, it was banned not only for use but from clinical trials after being implicated in the development of a deadly viral condition attacking the brain.

Two MS patients taking Tysabri died after developing progressive multifocal leucoencephalopathy, a serious neurodegenerative disease.

However, further to more tests, Tysabri has staged a gradual comeback, mostly based on its sheer efficacy, not to mention the convenience of use. Other MS treatments such as Copaxone are typically administered by daily injection, while Tysabri is given as a monthly infusion.

Teva, by the way, didn't manage to develop an effective oral version of Copaxone and is working on another oral MS drug, Laquinimod, together with the Swedish drug company Lundbeck.

As for Tysabri, some patients who had taken the drug had tearfully begged U.S. regulators to reinstate the drug, saying they were aware of the risks and preferred to assume them rather than accept other drugs. In June 2006, U.S. regulators agreed to allow Tysabri's marketing to resume, under stringent supervision and with other strings attached.

Tysabri, a monotherapy - not administered in conjunction with other drugs - comes in new packaging sporting new warnings. Namely, that taking it increases the risk of developing PML, which the Tysabri website describes as: "an opportunistic viral infection of the brain that usually leads to death or severe disability."

It also notes that the known cases of the viral development were limited to patients with recent or concomitant exposure to immunomodulators or immunosuppressants, which left them more vulnerable to infections. But there were not enough cases to rule out the possibility that PML may occur with Tysabri monotherapy, the website warns.

Multiple sclerosis is a degenerative disease of the nervous system. Its progress is unpredictable. Its symptoms include muscle weakness in extremities and difficulty with coordination and balance.