Merck has reformulated the top selling MS drug without human- or animal-derived serum albumin, and has reported improved tolerability and immunogenicity with the revamped treatment, with injection-site reactions three times less likely than with other treatments. The new formulation will be available in the same strengths and forms as the current product, and is due to be launched across the EU from September this year. Originally approved back in 1998, Rebif is the company's best-selling product, bringing in a record €312m over the second quarter this year alone thanks to increased sales in the US. However, the relapsing MS treatment market is a tight-knit crowd, with several interferon-based drugs shuffling shoulder to shoulder at the top of the tree. Biogen Idec's Avonex (interferon beta-1a) is currently the market leader, generating sales of $462m (€339m) over Q2, though Bayer Schering's Betaseron/Betaferon (interferon beta-1b) is still a player, bringing in €256m over the second quarter. Rebif itself is facing various patent expiries over the next six years, but this latest reformulation represents a tactical piece of life-cycle management and may help alleviate the threat of generic competition. More imminent problems may in fact come from Tysabri (natalizumab), Biogen/Elan's infamous MS drug that was taken off the market in 2004 following cases of a life-threatening brain infection in patients. The drug has since been allowed back onto the market (though with its use governed by strict guidelines), and according to analysts Moody's Investors Services may cause more near term competition for Merck's Rebif franchise. However, in recent weeks a new kid on the block has emerged, with Swiss firm Biopartners filing for EU approval of its new interferon beta-1a product, Biferonex. This new drug could prove a challenge to the reigning MS treatments, with its developers emphasising the fact that it is formulated without human serum albumin and is pH neutral. These features should make the formation of stimulating neutralising antibodies (known to limit treatment efficacy) in MS patients less likely. Merck Serono would not comment on the potential impact this new competitor could have on its Rebif franchise. Within the next few years, however, analysts see a new threat in the form of more user friendly oral drugs for the treatment of MS, which could spell the beginning of the end for the current injectable treatments. Merck is indeed just one of the companies racing to create an oral treatment and currently has its oral cladribine formulation in Phase III trials, representing "the most important drug in Phase III as it will be key in the long term replacement of Rebif," according to Moody's. However, there is no guarantee that the Merck oral formulation will be approved, let alone be first to market (though the company believes it is on track to hit this target), so protecting the Rebif franchise as best it can in the meantime makes perfect sense. The company will be hoping that the new formulation approved today will support the strong competitive position enjoyed by the existing Rebif product, and at least stave off competition for a little longer. As for plans for the new product in the US, the company says it is currently working with the US Food and Drug Administration (FDA) to address queries raised by the agency regarding the reformulation, but maintains its intentions to bring the new Rebif to the US market.