A Phase 3 clinical trial evaluating AB Science’s masitinib as a treatment for progressive multiple sclerosis can continue without having to add patients, an independent review board has decided.

The decision indicates that the therapy has been effective enough that its population base does not need to be expanded, the company said.

Although AB Science has been conducting the trial for U.S. regulators, those taking part are from the Barcelona area.

The AB07002 trial (NCT01433497) has been looking at the safety and effectiveness of masitinib as a treatment for people with primary progressive MS (PPMS) and relapse-free secondary progressive MS (SPMS).

Around 60 percent of MS patients have a progressive form of the disease. It accounts for about  400,000 patients in the United States and the European Union combined.

Masitinib is an oral therapy that inhibits enzymes called tyrosine kinases. They play an important role in cell growth, differentiation into other cells, energy conversion and death. The drug targets immune system components known as mast cells and macrophages.

Masitinib’s unique mechanism of action makes it a possible treatment for cancer and inflammatory diseases as well as central nervous system disorders.

It immunotherapy properties mean it has the potential to counter cancer, either alone or in combination with chemotherapy. Its ability to marshal immune cells against invaders and its anti-inflammatory properties make it a possible therapy for neurological and inflammatory disorders.

AB Science enrolled 656 patients in the Phase 3 trial. It has been measuring changes in patients’ disability over 96 weeks with an index known as the Expanded Disability Status Scale for MS.

The company said in a press release that it had planned to do an interim analysis of results once half of the patients had completed 96 weeks of treatment. Although the trial had yet to cover half the patients, the review board used a statistical method to predict that the probability of the therapy being successful was above 80 percent. This meant that the trail could continue without increasing the participant base, its said.

A key finding from the results so far is that masitinib has not raised any safety concerns.

Final results of the study are expected in the second quarter of 2019.

AB Science is also conducting Phase 3 trials of masitinib as a treatment for metastatic prostate cancer, metastatic pancreatic cancer, severe asthma, ALS, and Alzheimer’s.