SOMERVILLE, Mass. — Bruce Rosenblum knows the drug Relyvrio won’t save his life. It might not even make a difference.

But after using a make-your-own version for months, he stopped being able to get it early this summer and he’s eager to start up again.

Late Thursday, the Food and Drug Administration approved the use of Relyvrio to treat amyotrophic lateral sclerosis, more commonly known as ALS. Rosenblum said he’s thrilled by the decision and immediately requested a prescription for it.

Early trial data suggests the drug is particularly helpful early in the fatal disease that gradually robs people of their ability to control their movement, eventually including breathing.

Rosenblum and others with ALS don’t have a lot of other options.

There are only five other drugs approved to treat ALS, the most recent in 2017, but none has been shown to stop the inexorable loss of muscle control. Only one has been shown in some people to extend life, but by just three months on average.

Data on Relyvrio’s effectiveness remains preliminary. A six-month trial in 137 patients, half of whom received a placebo and half the active drug, suggested Relyvrio could slow the rate of decline. A follow-up found that patients on the active drug lived longer than those who got the placebo.

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An FDA advisory committee voted in March that the data was too thin to justify approval, but in a second meeting earlier this month, the committee reversed its position and recommended approval. The drug was approved in Canada in June.

A larger trial is due to be completed next year. The company has promised to take Relyvrio off the market if the more definitive study shows the drug doesn’t work. 

“We can all agree that this drug is not going to stop the disease in its tracks,” Clive Svendsen, an ALS researcher at Cedars-Sinai in Los Angeles, said before the FDA’s approval. A lot of drugs look promising in small trials, said Svendsen, who was not involved in Relyvrio’s development, because ALS progresses at different rates in different people.