AB Science trumpets phase 3 ALS data, but investors seem unmoved

New data come as EU regulators turn the drug down for another indication.

After years of disappointment, things might seem to be looking up for the amyotrophic lateral sclerosis patient community. Two weeks ago they got a new drug approved by the FDA, and now French biotech AB Science says its drug candidate masitinib slowed down progression in a late-stage trial.

Shares in the Paris firm barely shifted on the news, however, perhaps reflecting the fact that AB has a terrible history when it comes to masitinib—the drug chalked up another rejection in the EU yesterday—and also because the French regulatory authorities have been probing the company's adherence to clinical trial best practices, notes Forbes.

The new data on masitinib have just been presented at the European Network for the Cure of ALS (ENCALS) meeting in Slovenia, and the results show that adding an oral daily dose of the drug to background therapy with Sanofi's Rilutek—for years the only therapy available for the devastating neurodegenerative disease—slowed symptom progression by 27% compared to riluzole plus placebo.

According to the trial's international coordinator, Jesus Mora of the Hospital San Rafael, Madrid, the data back up interim results reported last year, which prompted a leap in AB Science's share price and also led it to suggest it would move forward with regulatory filings for masitinib in the U.S. and Europe. It has already filed for conditional approval with the EMA.

Not only did the drug slow down the loss of function in ALS patients over a 48-week follow-up period, it also helped them live longer without their disease progressing, according to the figures.

The trouble for AB Science is that for some time masitinib has been a drug in search of an indication. It's been sold for some years as a drug to treat mast cell tumors in dogs, but AB's efforts to find a human use have repeatedly ended in failure.

In the past, masitinib has been turned down by EU regulators for pancreatic cancer and gastrointestinal stromal tumors (GIST), with the EMA poking holes in AB Sciences' clinical trial design.

The biotech submitted the drug to the EMA for rare disease severe indolent systemic mastocytosis last year, but that application was knocked back just yesterday by the EU's Committee for Medicinal Products for Human Use (CHMP)—once again because of concerns about its adherence to good clinical practices.

AB Science says it will ask the committee to re-examine its mastocytosis decision, but going on experience to date investors could be forgiven for not leaping at the latest clinical data for masitinib in ALS. The company says it is setting up a second clinical trial to try to replicate the findings of its first study.

For ALS patients, the recent approval of Mitsubishi Tanabe Pharma's Radicava (edaravone), which was filed at the urging of the FDA, provides a more tangible near-term prospect as it is heading for launch in August. It also suggests, however, that the agency is open to approving ALS drugs with a lower evidence threshold, so expect further twists and turns in the masitinib story as it unfolds in the coming months.

Masitinib is an oral tyrosine kinase inhibitor targeting CSF1R and is thought to protect neurons from degenerating by targeting misfunctioning microglial cells—a type of white blood cell found in the brain and spinal cord—and reducing inflammation.

In addition to ALS, AB Science is also testing the drug in Alzheimer's disease, multiple sclerosis, asthma, rheumatoid arthritis and various cancers.