Genzyme Corp has presented data from a mid-stage trial of alemtuzumab, the drug seen as the jewel in its pipeline, which demonstrates the already-marketed leukaemia treatment's long-term efficacy for multiple sclerosis.

Alemtuzumab, which is marketed as Campath for the treatment of B-cell chronic lymphocytic leukaemia, is being tested by Genzyme and partner Bayer in MS. Data presented at the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) meeting in Gothenburg, Sweden, noted that nearly 90% of patients receiving the drug were free of sustained accumulation of disability and maintained improved mean disability scores and a low risk of relapse over the 60-month follow-up period.

In a study comparing alemtuzumab to Merck KGaA's blockbuster Rebif (interferon beta-1a), five-year findings revealed that 13% of patients on the Genzyme/Bayer drug experienced a sustained increase in disability compared with 38% on Rebif. In a second abstract presented at ECTRIMS, after 36-months of follow-up, the annualised relapse rate was 0.09 in patients receiving alemtuzumab as compared with 0.47 in those on Rebif, a reduction of 81%.

One concern for Genzyme, however, is some of the safety concerns thrown up by the Phase II trial. Immune thrombocytopenic purpura was identified in six alemtuzumab-treated patients and one Rebif patient and the symptoms of ITP "went unrecognised in the first alemtuzumab case and led to the onset of a fatal cerebral haemorrhage".

Also, 30% of alemtuzumab-treated patients developed an autoimmune thyroid-related adverse event. and one was identified to have anti-glomerular basement membrane (anti-GBM) disease, an autoimmune kidney disease. The patient was successfully treated and is in remission. Genzyme did note that patients who experienced an autoimmune adverse event, including ITP, experienced improved control of their MS consistent with alemtuzumab’s effect in the overall study population.

Genzyme is conducting two Phase III trials to evaluate alemtuzumab for MS and the data are expected to be available in 2011. The company, which is the subject of a hostile $18.50  takeover bid from Sanofi-Aventis, believes that the drug could become the new standard of care for treating the disease and bring in up to $2 billion in annual peak sales.

Sanofi is not convinced and believes sales will be half that or less. The value of alemtuzumab has been a sticking point between the two companies as to what is a realistic price for the French drugmaker to pay.