U.S. health officials approved a drug Thursday that is supposed to treat the deadly illness known as Lou Gehrig's disease.

The approval Thursday follows an intense lobbying campaign by patients and advocates, though it's also likely to raise questions about the standards used to review experimental medicines.

The Food and Drug Administration approved the medication from Amylyx Pharmaceuticals based on results from one small, mid-stage study.

“This approval provides another important treatment option for ALS, a life-threatening disease that currently has no cure,” said Billy Dunn, M.D., director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research in a news release. “The FDA remains committed to facilitating the development of additional ALS treatments.”

The agency's internal scientists repeatedly said the company's results were not convincing.

But thousands of patients have urged the FDA to be flexible and grant patients' access.

Lou Gehrig’s disease has no cure and most patients die within five years of initial symptoms.

According to Bloomberg, this marks the third major medication U.S. health officials have authorized.