* Five-year follow-up data consistent with four-year data
* No new cases of serious side effects were reported
* Genzyme sees drug as more valuable than Sanofi does (Adds description of disease, analyst comment, side effect details)
By Toni Clarke
BOSTON, Oct 14 (Reuters) - Genzyme Corp GENZ.O presented new data from a trial of its experimental multiple sclerosis drug alemtuzumab on Thursday that continued to show strong efficacy with no new or worsening side effects.
Genzyme believes the drug, if approved, could become the new standard of care for treating the disease and gain a significant portion of a market the company estimates will be worth roughly $13 billion by the end of this year.
Alemtuzumab, also known as Campath, is a key pawn in the battle between Genzyme and French drugmaker Sanofi-Aventis SA (SASY.PA) which has made a hostile, $18.5 billion bid for the company. [nLDE69302S]
Sanofi is keen to downplay the drug's value in order to justify offering what Genzyme considers to be an unrealistically low price for the company. [nN06220936]
Sanofi Chief Executive Chris Viehbacher has tentatively forecast peak annual sales of the drug at $700 million, a figure he said is in line with market expectations, based on forecasts from seven brokerages.
But independent market research group BioMedTracker predicts sales more than double that, at $1.6 billion in 2019. And some analysts predict peak sales closer to $2 billion.
Results from late-stage trials of the drug will be available by the middle of next year and the company expects to file for approval in early 2012 and receive a decision from U.S. regulators by the second half of that year.
Multiple sclerosis is an autoimmune disease in which white blood cells, which are supposed to fight infection or disease, misguidedly attack the body's own cells, causing damage to the myelin sheath that protects nerves in the brain and spinal cord.
The disease, which some groups estimate affects between 350,000 and 400,000 patients in the United States, can cause a variety of symptoms including impaired mobility, fatigue, cognitive, speech and other difficulties.
Follow-up data from a mid-stage trial, presented at the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) on Thursday, showed that 87 percent of patients treated with Campath experienced no worsening of symptoms of disability after five years.
By comparison, only 62 percent of patients taking Rebif, a rival drug made by EMD Serono, an affiliate of Germany's Merck KGaA (MRCG.DE) and Pfizer Inc (PFE.N), experienced no worsening of disability.
"The most remarkable thing about this data is that it hasn't changed much from the four-year data," said Michael Panzara, who oversees clinical development of Genzyme's multiple sclerosis and immune system drugs.
Most analysts and investors seem to agree that the drug is highly efficacious. The question is whether it is sufficiently safe to win approval and achieve widespread commercial success.
Initial three-year results, reported in 2008, showed that six patients developed immune thrombocytopenic purpura (ITP), an autoimmune disease in which low blood platelet levels can lead to bruising and bleeding. One patient in the trial died of a cerebral hemorrhage. The remainder were diagnosed more quickly and successfully treated.
Encouragingly, no new cases of the condition were reported in the latest data.
Another potential side effect of the drug is Goodpasture syndrome, a rare disease that can quickly cause kidney failure. In the initial clinical trial, one patient developed the disease. That patient was treated and has recovered normal kidney function, Panzara said.
Two other patients who were given the drug outside the confines of a clinical trial also developed the syndrome. Campath is currently approved to treat cancer, but physicians are allowed to prescribe it for conditions for which it has not been approved on a so-called off-label basis.
No additional cases of the condition were reported in the latest data.
"Since rare autoimmune events are of people's concern, the fact that there aren't any is positive," said Michael Yee, an analyst at RBC Capital Markets. "Everything is on track."
Genzyme said that as of its last meeting in September, an independent safety monitoring committee had reported no cases of ITP or Goodpasture syndrome in the Phase III clinical trials.
Panzara said it is unclear why no new cases have been observed, and said the company is still working to fully understand the drug's mechanism of action. But one theory is that the drug resets the body's immune system in some fundamental way, allowing it to function more normally even when the drug is no longer being taken.
The latest data showed patients taking Campath had an annualized relapse rate of 0.11, compared with a relapse rate of 0.35 for Rebif, which indicates that on average, approximately one in every 10 patients who received Campath had a relapse in any given year, compared with about one in every three patients taking Rebif.
The Campath group, moreover, on average saw an improvement in disability scores as opposed to a worsening among those on Rebif.
"This is unique and starts us thinking, are these people in remission?" said Panzara. "Is this what remission in MS looks like?"
Genzyme is co-developing the drug in multiple sclerosis with German drugmaker Bayer (BAYGn.DE). (Reporting by Toni Clarke, Additional reporting by Bill Berkrot, editing by Dave Zimmerman and Matthew Lewis)