The Food and Drug Administration approved on Monday BiogenicThe Alzheimer’s drug aducanumab is the first drug approved by the US authorities to slow cognitive decline in people with Alzheimer’s and the first new drug for the disease in almost two decades.

The FDA’s decision was eagerly awaited. The drug, which is marketed under the name Aduhelm, is also expected to generate billions in sales for the company offers new hope to friends and families of patients living with the disease.

“We are aware of the attention associated with this approval,” said Dr. Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research, in a press release. “We know that Aduhelm has drawn the attention of the press, the Alzheimer’s patient community, our elected officials and other interested stakeholders.”

“With treatment for a serious, life-threatening disease in balance, it makes sense that so many people followed the outcome of this review,” added Cavazzoni.

The FDA said it would continue to monitor the drug when it hits the US market. The agency granted approval on the condition that Biogen conduct another clinical study.

Alzheimer’s disease is a progressive neurodegenerative disease that slowly destroys memory and thinking skills. More than 6 million Americans are reportedly living with it Alzheimer’s Association estimates. According to the group, this number is expected to rise to almost 13 million by 2050.

To date, there have been no FDA-approved drugs that can slow the mental decline of Alzheimer’s, the sixth leading cause of death in the United States. The agency has approved Alzheimer’s drugs that are aimed at relieving symptoms rather than slowing the disease itself down.

Federal agencies have come under intense pressure from friends and family members of Alzheimer’s patients to speed up aducanumab, but the road to regulatory approval has been controversial since it showed promise in 2016.

In March 2019, Biogen stopped work on the drug after analysis by an independent group found it was unlikely to work. The company then shocked investors a few months later by announcing that it would apply for regulatory approval for the drug after all.

Biogen’s shares rose in November after gaining support from FDA staff, who said the company had shown very “compelling” evidence of aducanumab’s effectiveness and that it had “an acceptable safety profile that would support its use in people with Alzheimer’s disease”.

But two days later, an external panel of experts advises the US authorities unexpectedly declined to support the experimental drug citing inconclusive data. It also criticized the agency’s staff for rating it too positively.

When Biogen filed for approval for the drug in late 2019, its scientists said a new analysis of a larger data set showed that aducanumab “reduces clinical decline in patients with early-stage Alzheimer’s disease.”

Alzheimer’s experts and Wall Street analysts were immediately skeptical, wondering whether the clinical trial data was enough to prove the drug works and whether approval could make it difficult for other companies to enroll patients in their own drug trials.

Some doctors said they won’t prescribe it the drug when it hits the market due to the mixed data package that supports the company’s application.

Supporters, including advocacy groups and family members of patients desperately looking for a new treatment, have admitted the data is not perfect. However, they argue that it could help some patients with Alzheimer’s, a progressive and debilitating disease.

Biogen’s drug targets a “sticky” compound in the brain known as beta-amyloid that scientists expect to play a role in the devastating disease. The company previously estimated that approximately 1.5 million people with early-stage Alzheimer’s in the United States could be candidates for the drug, according to Reuters.

The FDA’s decision is expected to reverberate across the biopharmaceutical sector, RBC Capital Markets analyst Brian Abrahams said in a June 1 announcement to customers.

The US agency said Monday that it had determined that there was “substantial evidence” that the drug was helping patients. “With Aduhelm approved by the FDA, an important and critical new treatment is available to patients with Alzheimer’s disease to combat the disease,” it said.