Ireland’s Elan Corporation received a boost on both ides of the Atlantic on news that its withdrawn multiple sclerosis drug, Tysabri (natalizumab), boosts the efficacy of partner Biogen Idec’s MS offering, Avonex (interferon beta-1a).

According to two-year Phase III clinical trial data, the addition of Tysabri to Avnoex slowed the progression of disability in patients with relapsing forms of MS, resulting in a 24% reduction in the risk of disability progression, versus Avonex alone. The 1,171-patient study, dubbed Sentinel, also showed that the addition of Tysabri to Avonex led to a 56% relative reduction in the rate of clinical relapses compared to that provided by Avonex alone. The firms note that reduction in relapse rate was statistically significant and sustained over the entire two-year study period.

Elan and Biogen Idec voluntarily pulled the plug on Tysabri early this year after it was linked to a rare, but potentially fatal, brain infection [[01/03/05a]]. It had widely been expected that Tysabri would be the catalyst behind the Irish company’s turnaround. The firm, which teetered on the brink of bankruptcy a couple of years ago [[08/02/02b]], had been optimistic of a return to profitability in 2006 at the hands of Tyasabri [[28/10/04c]].

Although Elan’s share price climbed by as much as 9% on the New York Stock Exchange yesterday and was rising steadily in Dublin this morning, analysts at Jefferies caution that the news pales into insignificance with the side effect issues still hanging over the drug. The firms are conducting a thorough safety evaluation and hope to report their findings by the end of the summer.