Local Alzheimer’s patients, caregivers, advocates, and researchers, hailed the approval of Cambridge-based Biogen’s drug aducanumab on Monday as the first treatment that could slow the progression of the disease.

Greg O’Brien of Brewster is a former investigative reporter, and now an author who has lived with early onset Alzheimer’s for about a decade. He says he testified before an FDA panel last year in favor of aducanumab’s approval, which he calls “an answered prayer.”

Although he doesn’t think the drug will help him, because he is not in the early stages of the disease, O’ Brien tells GBH News, he supports the drug, “on the basis of hope.”

“If it clearly can be helpful and there's no harm, throw us a lifeline, give us some hope,” O’Brien said. "And they did. And so I am so thrilled and so pleased and honored by what the FDA did.”

O’Brien said Alzheimer’s has plagued many close relatives in his family, including his mother, who he says suffered with it for years before telling anyone. He said giving people hope will encourage people to come forward with their diagnosis, which can lead to greater awareness and better funding for research.

“There is still a stigma connected with Alzheimer's and dementia,” said Jim Wessler, CEO of the Massachusetts-New Hampshire chapter of the Alzheimer's Association. He says polling confirms that, "this is the most feared disease in America. It's more feared than cancer or heart disease.”

Wessler said his organization believes that only about 50-percent of those who have Alzheimer's are diagnosed; and of those who are diagnosed, only about half of those are told of their diagnosis.

“Now we have the first medication that will begin to make a difference… if I was a clinician and I had no tools that I thought really made a difference, I'm going to be less inclined to jump into this because I don't think I can help my patients. Now, there is something that they can do that at least can begin to start helping to attack this disease.”

Wessler said having the first drug that clears out amyloid, a sort of sticky protein that accumulates in the brains of people with Alzheimer’s, could promise to give those people more time, especially those in early stages of the disease.

“And who wouldn't grab that time to see your daughter married, or visit a grandchild in another city,” Wessler said.

Kevin Reynolds of South Boston is a long-distance caregiver for his mother in the Atlanta area, and he’s also on the board of the Massachusetts-New Hampshire chapter of the Alzheimer's Association.

“When my mother was diagnosed 12 years ago, it was such a dark diagnosis,” Reynolds said. “So now if you have a drug that can treat this awful disease, you might also lead to more early diagnosis… this brings a lot of hope. And as you can imagine, when there's one drug, there should be more to follow.”

Alzheimer researcher Dr. Rudy Tanzi agrees; he’s a professor of neurology at Harvard Medical School and chair of the Cure for Alzheimer's Fund. He says drug breakthroughs for other diseases helped accelerate treatments, and he believes this will be the same for Alzheimer's.

“That's as big a day for Alzheimer's patients and families as it was for getting cholesterol medications out to reduce heart disease,” Tanzi said.

Wessler says the approval of aducanumab heralds a day when Alzheimer’s could be a chronic condition, as HIV is now.

“It's not a cure and it's not going to add twenty five years of cognitive health,” said Wessler, “but it is a step in the right direction. We’re in baseball season and this is a single, a solid single and we'll keep going for the next single. Maybe someday we'll have a grand slam.”

Marilyn Schairer contributed to this report.