In a major development for patients and the biotechnology industry, the U.S. Food and Drug Administration (FDA) approved the use of a new drug, Aduhelm (aducanumab), for treating early Alzheimer’s disease.

But the new drug, made by the biotechnology company Biogen, has been marred by controversy throughout its development history, with prominent Alzheimer’s disease specialists arguing the drug’s benefits are unlikely to outweigh the risk of serious side effects.

“This is the first time the FDA has conditionally approved a drug for the early treatment of Alzheimer’s in 20 years,” says Dr. Jennifer Ashston, ABC chief medical correspondent. “This is something that is potentially encouraging news for the 1 in 9 Americans over the age of 65 who are facing a diagnosis of Alzheimer’s.”

According to the Alzheimer’s Association, more than 5 million Americans have Alzheimer’s disease, and this number is expected to more than double by 2050 as the U.S. population continues to age. Before the SARS-CoV-2 pandemic, Alzheimer’s disease was the sixth-leading cause of death in the United States, with the Centers for Disease Control and Prevention reporting more than 120,000 deaths in 2019 alone.

“Some of the potential side effects are brain swelling and some tiny bleeding in the brain,” says Joel Salinas, MD, MBA, neurologist at the Pearl I. Barlow Center for Memory Evaluation and Treatment at NYU Langone Health who specializes in dementia and Alzheimer’s disease. Dr. Salinas, who is also the Lulu P. and David J. Levidow Assistant Professor of Neurology, was not involved with the clinical trials for Aduhelm.

“This is still light years from where we were. I think studies should continue now that the drug is approved. For people who get the treatment, even if it just means having a couple years of stability, that’s still incredibly meaningful for them,” says Dr. Salinas.

Read more from ABC News.