The pharmaceutical industry has not won FDA approval for a new drug to treat Alzheimer’s disease since 2003. But for the first time in more than a decade, there may be hope on the horizon.

At the Alzheimer’s Association International Conference in Chicago on Wednesday (July 25), representatives from Biogen, a Cambridge-based pharmaceutical company, and it’s partner Eisai, a Japanese company, provided more details about a recent phase II clinical trial they had teased earlier this month. Though no group in the trial had seen significant improvement in the first year, after 18 months, the companies had observed more promising results.

For the trial, a compound known as BAN2401 was given through an IV to six groups of adults with early stages of Alzheimer’s disease (five groups received various doses of the drug, and one received a placebo). BAN2401 works by reducing the chunks of amyloid buildup in the brain, which have long been thought to be one of the causes of brain degradation from Alzheimer’s.

After 18 months, the 161 people receiving the highest dose of BAN2401 showed significant improvement both with the reduction of amyloid buildups and improved cognition compared to the placebo, according to STAT.

There were a handful of instances of brain swelling as an adverse side effect, and some people experienced an allergic reaction where the IV was inserted.

Although amyloid proteins have always been suspected to play a significant role in Alzheimer’s disease, this study is only the second to find a concrete connection between reduced amyloid buildups and improved cognitive function. It suggests that targeting these proteins may be a good way to combat the disease in future trials.

Amyloid proteins were reduced by as much as 93% in some trial participants, making 81% of participants in the successful group what researchers call “amyloid negative.” Although this doesn’t mean these patients were cured, it’s a big deal. Additionally, the team compared the cognitive decline of this group to those who received the placebo using multiple metrics. They found that participants taking the highest dose of BAN2401 performed 30% better on a new cognition test called ADCOMS than those taking the placebo. ADCOMS is not the typical scale used to assess cognitive decline, but has been shown to be more sensitive (paywall) to changes in cognitive ability. When the group used a more common, longer-standing scale, participants in the highest dosage group performed 47% better than the placebo.

It’s not clear how long the road to FDA approval for BAN2401 is. Although the results are promising, this trial was fairly small, and as Vox points out, it’s frowned upon in the research community to change your end results midway through a trial. At the moment, the FDA requires new drugs targeting Alzheimer’s to go through two phase III trials, showing a reduction of both a biological marker for the disease and cognitive decline. In March of this year, the organization published a draft report that said in the future they would accept only a reduction of biomarkers, without a reduction in cognitive decline, a decision has been supported by the research community. This is because in early cases of Alzheimer’s, patients may have the biological indicators of the disease without actually showing symptoms.

Lynn Kramer, the chief medical officer for neurology at Eisai, said that the company and its partner plan to ask the FDA to accelerate BAN2401’s approval, based on these new phase II trial results.