The maker of the newest treatment approved for amyotrophic lateral sclerosis said Thursday that it would withdraw the drug from the market because a large clinical trial did not produce evidence that the treatment worked.

The company, Amylyx Pharmaceuticals, said in a statement that it had started the process of withdrawing the drug in the United States, where it is called Relyvrio, and in Canada, where it is called Albrioza. As of Thursday, no new patients will be able to start the drug, while current patients who wish to continue taking the medication can be transitioned to a free drug program, the company said.