Two is better than one in the Alzheimer’s market

That might be the case for midsize biotech Biogen and its Japanese partner Eisai. Their Alzheimer’s drug, Leqembi, was approved by the Food and Drug Administration last year but it has failed to make major inroads. It might do better once Big Pharma gets into the field as well.

Last week, a panel of independent advisers to the FDA unanimously voted in support of Eli Lilly’s donanemab, a competitor in the same class of drugs that target amyloid plaques in the brain. The FDA is expected to decide on whether to approve the drug by the end of the year.

Life expectancies around the world have surged in recent decades, increasingly putting people at risk of dementia. About one in nine seniors has Alzheimer’s disease, the most common cause of the condition, which works out to some seven million Americans. One might think that a therapy that slows down patients’ decline would immediately create a huge opportunity, similar to what is happening in the obesity market. But adoption is moving at a snail’s pace. Leqembi brought in $19 million in revenue last quarter—a very modest sum for a drug category that Wall Street expects to reach billions of dollars in annual sales.

There are several reasons for the slow uptake. For starters, the clinical benefit of the drug is modest and there are non-negligible safety concerns, such as brain bleeding and swelling. The companies say so themselves.

“We fully recognize that this is an important, but ultimately incremental step in the treatment of Alzheimer’s disease," David Hyman, Eli Lilly’s chief medical officer, told the FDA advisers panel last week. “Patients deserve more, and we continue to work on additional approaches to address this disease."

It is also incredibly cumbersome. Instead of pills or even an injection, treatment requires infusions, an evaluation by a specialist, a spinal tap or PET scan and regular MRI scans to check for swelling and bleeding. And at the moment, there is a shortage of the medical infrastructure needed to enable the treatment of patients on a massive scale. On the regulatory side, there is a Centers for Medicare and Medicaid Services requirement to collect patient data in a registry, which adds another layer of complexity for doctors.

Biogen and Eisai are very much at an early stage of building awareness of their drug while lobbying for less stringent reimbursement rules from the government. Having pharma’s biggest company by market value going to bat together with you is therefore probably a good thing.

“Our view currently is that the more anti-amyloid therapy approvals, the better the disease awareness/therapeutic education will be, and this should be a tailwind for the ongoing Leqembi launch," said Myles Minter, an analyst at William Blair.

Underscoring that point, Biogen’s shares are up slightly more than Lilly’s since the FDA panel meeting.

Leqembi and donanemab both work in Alzheimer’s patients with mild cognitive impairment by targeting amyloid plaques—abnormal clumps of protein that can build up in the brain, disrupting cell function. The drugs are far from a cure, but they can potentially slow the disease’s progression and give patients several more months, or even years, of a normal life. In the study of more than 1,730 patients, Lilly’s donanemab slowed patients’ decline by 35% compared with placebo over 18 months of treatment.

Hyman, Lilly’s chief medical officer, told the FDA panel that the company is working on targeting patients earlier on in the process, with the goal of preventing symptomatic Alzheimer’s. Given that the plaques build up in the brain over decades, the idea of earlier prevention is worth testing out. The best-case scenario would be for amyloid therapies to work the way drugs such as statins do for cholesterol, helping to prevent strokes or heart attacks.

At this point, getting two drugs with moderate benefits out into the market has other advantages for the broader field as well. As these drugs start to generate a return for the pharmaceutical industry, investors and companies will feel more confident in researching newer therapies. There are currently 19 drugs in mid- or late-stage testing, with several of them undertaking approaches that extend beyond the anti-amyloid hypothesis, HSBC analysts note. Six trials, for instance, are focused on targeting tau, another protein implicated in the condition. As the therapeutic landscape emerges, doctors and patients will shift from coping with the disease to treating it as well.

The job of building a market for Alzheimer’s won’t be easy. More therapeutic options are good for patients as well as for drug companies.

Write to David Wainer at david.wainer@wsj.com