(Bloomberg) -- Neurologists at the biggest Alzheimer’s research meeting in the US experienced something this week they hadn’t in years: optimism.

Just months after Eisai Co.’s Alzheimer’s drug Leqembi received full US approval, normally dour neurologists were buoyed by hints of easier-to-use therapies and the possibility of responding to the disease faster and on multiple fronts over the next few years. 

“People have been so pessimistic and so negative,” in the past because of the many failed Alzheimer’s trials, Harvard Medical School neurologist Dennis Selkoe said. Now, “there’s rightful optimism.” Neurologists are learning to have conversations with patients and their caregivers about therapies risks and benefits, said Selkoe, a welcome change.

At the Clinical Trials on Alzheimer’s Disease meeting in Boston, Eisai researchers reported early results on a new injected Leqembi formulation that could be administered at home, potentially eliminating long drives to infusion centers. Eisai also showed data suggesting patients might benefit more if treated in the early stages of the disease; rival Eli Lilly & Co. offered a similar analysis on its similar, but still experimental, drug. Together, the studies suggest that early cases of Alzheimer’s might some day be halted or slowed dramatically, researchers said. 

The change has been a long time coming. Less than 10 years ago, the specialty was in a state of near-despair as one Alzheimer’s trial after another flopped, while researchers questioned whether they understood anything at all about what causes the disease and how to treat it. Finally, Leqembi has given doctors and drugmakers a foothold that they’re looking to transform into a full-on assault on the brain-destroying disease that affects some 6 million people in the US alone, and is the main contributor to annual dementia costs of about $345 billion.

“I’ve been in the field a long time and we have a momentum that I’ve never seen,” said Jeffrey Cummings, an Alzheimer’s researcher at the University of Nevada, Las Vegas’s department of brain health. “We have successes and they are important and they are also first steps.”

Read More: Eisai Alzheimer Drug Shows Promise in Injected-At-Home Form 

The key advance over the last few years has been the vindication of the theory that amyloid, an abnormal brain protein, plays a role in causing Alzheimer’s disease and reducing its levels would help slow the damage. Now that a large trial has shown that Leqembi, the amyloid-lowering drug from Eisai and Biogen Inc., slows the disease, the tide has turned, Harvard’s Selkoe said. 

The way forward is far from clear. Taking Leqembi requires an intensive regimen of twice-monthly infusions. It’s accompanied by brain scans, first to establish that there’s amyloid in the patient’s brain and then to watch for side effects like brain swelling and bleeding that require careful monitoring. The drug is the first shown to slow the advance of the disease, but only by about 27%. 

But the evidence that Alzheimer’s can be slowed has invigorated the field. Biogen highlighted preliminary trial results from an experimental drug that targets another Alzheimer’s-linked protein called tau, saying it saw “favorable trends” in measures of cognition and daily activity. Drugs that hit the disease on different fronts like tau could potentially one day be combined with anti-amyloid agents for a bigger effect, doctors said.

Read More: Biogen’s Experimental Alzheimer’s Drug Shows ‘Favorable Trends’

Selkoe said he was particularly intrigued by new findings from an earlier Eisai trial that looked at patients with low levels of tau. According to results presented Wednesday at the meeting, roughly 60% of low-tau patients who received Leqembi improved after 18 months on the drug, compared to just 28% of those on placebo. 

“All the data that we heard today suggests that the longer you treat, the more likely it is you get a benefit,” Selkoe said in an interview Wednesday evening. “And in some cases, if you have very mild disease at the beginning, you might even have some improvement, which is something we’ve never been allowed to say.” 

Roche Holding AG, one of the companies whose earlier attempts to develop amyloid lowering drugs failed, also reported positive results at the meeting. In an early test of an antibody technology called “brainshuttle,” amyloid was completely cleared from the brains of 75% of patients who got the highest dose after just 28 weeks, the company reported. Patients in the ongoing trials have seen relatively low rates of brain swelling and brain bleeding so far, Roche said. 

Progress is coming so fast that researchers are starting to compare Alzheimer’s with another dreaded disease where new drugs are extending lives. 

“We really think this field is going to look like cancer five years from now,” said Howard Fillit, chief science officer at the Alzheimer’s Drug Discovery Foundation.

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