Shares in Elan surged yesterday after test results showed that, when combined with another product, its suspended multiple sclerosis (MS) drug Tysabri reduced the disease's progress.

The addition of Tysabri to Biogen's Avonex drug resulted in a 24 per cent reduction in the risk of disability progression compared to the effect provided by Avonex alone, Elan said.

The tests, which were carried out prior to the February suspension of Tysabri trials, also found there was a 56 per cent reduction in clinical relapses when the two products were used together.

In Dublin, the shares rose 9.3 per cent, or 56 cents, to €6.57, their highest closing price since the drug was withdrawn from the market on February 28th. In the US, the stock was up 1.67 per cent, to reach $7.92.

The withdrawal and subsequent suspension of all Tysabri trials followed reports of a rare and potentially fatal disease of the central nervous system in patients taking the drug. PML, as the disease is known, attacks the protective sheath over cells in the central nervous system.

Tysabri, which is designed to help relieve the symptoms of MS, Crohn's disease and rheumatoid arthritis, has since been linked to the death of two of the patients. In total, five cases of PML or suspected PML are being investigated.

Although Elan is still conducting a safety review and has yet to make a decision about returning the drug to market, head of research Lars Ekman confirmed yesterday that the drug does continue to show benefits in the treatment of immune-meditated diseases. He said the company remains strongly committed to defining Tysabri's benefit-risk profile and determining the appropriate path forward.

His comments were reiterated by Burt Adelman, head of development at Biogen, who said the company continues to believe in the therapeutic benefit of Tysabri in the treatment of MS. He also said the investigation into the drug's safety is on track and that they hope to have the findings by the end of the summer.

Separately, rival drugmaker Teva said yesterday that sales of its MS drug hit a record in the second quarter, up 29 per cent on the year-earlier period. Teva, of Israel, markets its Copaxone drug jointly with Sanofi-Aventis.

Elan is due to report its second-quarter results on July 28th.