Switzerland’s Serono said yesterday that it is seeking US and European approval to market a new and improved form of its top-selling multiple sclerosis drug Rebif (interferon beta-1a).

The company says that trials in patients with the relapsing remitting form of MS have shown a “substantial improvement in overall tolerability” on measures such as injection site reactions. Furthermore, the data have also thrown up a reduced incidence of antibody formation – proteins generated by the body that recognise the drug as foreign and raise an immune response to it - which the company says could “translate into additional benefits to the patient.”

Rebif already pulls not-insignificant sums for Serono (some $335 million for the fourth quarter of 2005) but is facing growing competition, most notably from Biogen Idec and Elan’s Tysabri (natalizumab) – which could soon make its return to the market after a global suspension following links to a rare brain disorder. The US Food and Drug Administration’s advisory committee recently gave its backing to the re-launch of Tysabri onto the market, although the final decision has now been put back until June.

MS is a chronic inflammatory condition of the nervous system and affects some 2 million people worldwide, primarily hitting people in young adulthood. Additional data on the new formulation of Rebif will be presented at a medical meeting during the latter half of the year, says Serono.