Eisai Biogen: Alzheimer’s drug Leqembi reveals advantages over three years

The newly FDA-approved Alzheimer's drug Leqembi is prepared on Tuesday, November 7, 2023, at Abington Neurological Associates in Abington, PA.

Hannah Yoon | The Washington Post |

The breakthrough Alzheimer's drug Leqembi slowed the progression of the disease in patients over three years, highlighting the need for long-term treatment, according to new data released Tuesday by Japanese pharmaceutical company Eisai.

The study results on Leqembi, which Eisai Biogenalso found that a patient's Alzheimer's disease worsened after stopping treatment. The incidence of adverse events associated with Leqembi, including brain bleeding and swelling, decreased after six months of treatment, Dr. Lynn Kramer, Eisai's chief clinical officer for advanced human biology studies, told CNBC.

This decline is critical: These brain side effects have raised concerns among some doctors and are the main reason why a European drug regulator advised against approving Leqembi last week.

The study contains the longest available data on Leqembi's efficacy and safety to date. Since approval last summer, the market launch in the US has been bumpy, partly due to bottlenecks in requirements for diagnostic tests and regular brain scans. Eisai published 24-month data on Leqembi in November.

Eisai presented the results on Tuesday at the Alzheimer's Association International Conference in Philadelphia, the world's largest conference on dementia research. The results provide a first glimpse of what the future might look like for Alzheimer's patients with therapies such as Leqembi, which is currently administered twice a month by infusion.

The drug is a monoclonal antibody that targets toxic plaques in the brain called amyloid, a hallmark of Alzheimer's disease, and is designed to slow the progression of the disease in its early stages. Leqembi also works by eliminating protofibrils, the building blocks of amyloid plaques.

The data demonstrate the importance of early and sustained treatment for people living with this notoriously difficult-to-treat brain disease – even after a drug has cleared a patient's amyloid plaques.

“Continued treatment is important if you want to maintain your cognitive abilities and functionality for longer,” Kramer said.

Although Leqembi is not a cure, “if you start early enough, it can benefit you for years,” he said.

Kramer added that Eisai expects that patients will eventually be able to switch to a maintenance dose of Leqembi after approximately 18 to 24 months of treatment, which would allow less frequent or more convenient way to take the medicine over a longer period of time.

Eisai and Biogen are seeking regulatory approval for a once-monthly infusion of Leqembi, with a decision expected in January. The drugmakers also plan to launch an injectable form of Leqembi that patients can take once a week at home.

“These two things will change the paradigm, make it easier for the patient, make it easier for the entire medical system,” Kramer said in an interview.

Nearly 7 million Americans are affected by the disease, the fifth leading cause of death among adults over 65, according to the Alzheimer's Association. By 2050, the number of Alzheimer's patients in the U.S. is expected to rise to nearly 13 million.

Details of the long-term study

The results are based on extensive research on selected participants in mid- and late-stage Leqembi studies.

A phase three study called Clarity AD studied three different groups of patients for 36 months.

One group of participants took Leqembi for three years, while another group received a placebo for the first 18 months before switching to Eisai's drug for the same duration. Eisai monitored a final group of patients outside the study who received no treatment for three years.

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Patients who started treatment with Leqembi early continued to benefit from the drug over three years and showed slower cognitive decline compared to the other two groups, according to a presentation by Eisai.

According to Kramer, the difference in cognitive decline between the “early onset” Leqembi group and those who received nothing throughout the study period became larger between 18 and 36 months.

Leqembi “interrupts the natural course of the disease and has an increasingly powerful effect,” he said, adding: “The earlier you detect the disease, the better.”

Patients who started on a placebo experienced slower cognitive decline after they switched to Leqembi after 18 months, but their Alzheimer's disease was still worse than in the group that took Leqembi earlier in the 36-month period.

A sub-study of the study looked at patients who had no or very low levels of another protein called tau, which accumulates in the brain and is considered a marker of the severity of Alzheimer's disease. People with low levels of this protein are in the early stages of the disease.

After three years of taking Leqembi, 59 percent of people with no or very low tau levels showed no progress at all in their Alzheimer's disease, the presentation said. Just over half of these patients actually saw their condition improve.

A Phase 2 study called Study 201 has now examined patients who temporarily stopped treatment with Leqembi.

For 18 months, one group of participants took Leqembi and the other group took a placebo. The groups then took nothing for an average of two years before all patients began treatment with Leqembi for another 18 months.

The positive effect of Leqembi on a patient's disease was maintained even after treatment was stopped, the presentation said.

But the rate of cognitive decline in patients who stopped taking Leqembi returned to the rate in people who took a placebo during the break, showing that the disease continues to progress even when amyloid plaques are removed and a patient stops taking Leqembi, Eisai said in a news release.

“The idea is: If you stop, you’ll get worse,” Kramer said.

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