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AB Science told investors last February that its experimental drug masitinib improved symptoms of patients with amyotrophic lateral sclerosis, also known as Lou Gehrig's disease, greater than a placebo, achieving the primary endpoint of a phase III study.

The magnitude of masitinib's benefit for ALS patients was not disclosed at that time, but that's about to change. On May 18, the doctors who conducted the clinical trial for AB Science will present the masitinib data at an ALS research meeting in Slovenia.

The French drug maker, which trades on Euronext Paris under the ticker AB, filed an approval application for masitinib with the European Medicines Agency. A decision is expected in the second half of the year. The May 18 presentation will be the first time investors see the data under review by European regulators.

It also follows close behind the arrival of the first new medicine to treat ALS in 22 years. On Friday, FDA approved Radicava (generic name: edavarone) from MT Pharma America, the U.S. subsidiary of Japanese drug maker Mitsubishi Tanabe Pharmaceuticals.

ALS is a progressive disease which destroys nerve cells in the brain and the spinal cord. Most ALS patient die from muscle paralysis that stops them from breathing. Before Radicava, the last drug to treat ALS was Riluzole in 1995.

The urgent need for new medicines to treat ALS spurred FDA to take an unusually active role in securing Radicava's approval. The agency encouraged MT Pharma to submit a U.S. marketing application based on a clinical trial conducted in Japan, where the drug was approved first.

AB Science has not disclosed how or when it will submit a marketing application to the FDA but the company clearly hopes European regulators are as welcoming with masitinib as the FDA was with Radicava.

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The study to be presented on May 18 enrolled 394 ALS patients randomized to treatment with a high or low dose of masitinib on top of Riluzole or placebo plus Riluzole. Treatment lasted for 48 weeks, after which the relative improvement of ALS symptoms was assessed using the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALFRS-R), a 48-point measure of ALS disease severity.

AB Science designed its study to detect an approximate three-point average difference in the ALSFRS between masitinib and placebo, assuming placebo patients deteriorate by about one point per month. That would represent a 25% slowing of ALS disease progression favoring masitinib over placebo.

For comparison, Radicava secured FDA approval based on a study of 137 patients treated for six months that showed, on average, a 2.5-point difference (improvement) on the ALSFRS.

AB Science has already announced the high dose of masitinib (4.5 mg/kg per day) achieved the study's primary endpoint, but how big of change relative to placebo awaits the May 18 presentation. The masitinib low dose (3.5 mg/kg per day) failed to separate significantly from placebo, the company said.

Secondary efficacy endpoints from the study, including progression-free survival and improvements in lung function, will also be examined closely, as will the drug's safety.

AB Science suffers from a credibility problem because of previous failures related to masitinib's clinical development. European regulators have rejected the drug twice already, turning away applications to treat two types of cancer, GIST and pancreatic.

The company claims to be conducting 13 phase III studies of masitinib in different cancer indications plus diseases like asthma, Alzheimer's and rheumatoid arthritis. But the current status of many of these masitinib clinical trials is listed as "Unknown" on ClinicalTrials.gov.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.