An Eisai drug that addresses an underlying mechanism associated with Alzheimer’s disease progression has won FDA approval, a regulatory decision that echoes a prior drug approval in the neurodegenerative disorder while also establishing new safeguards and monitoring standards to protect patients.
The drug, lecanemab, is an antibody designed to break up amyloid beta, a protein that forms sticky plaques on the brains of Alzheimer’s patients. Eisai will commercialize its new drug under the name “Leqembi.” It’s the second FDA-approved therapy that works by targeting amyloid and the second product to reach the market from a multi-drug partnership that Japan-based Eisai has with Biogen. Review of Leqembi, an intravenously infused drug administered every two weeks, was separate from that of the Biogen drug, Aduhelm. But the imprint of Aduhelm is evident in the FDA’s Leqembi approval.
The Leqembi regulatory decision was based on the results of a placebo-controlled Phase 2 trial that enrolled 825 patients. The main study goal was to measure the change in score according to a scale used to assess Alzheimer’s patients. However, in granting accelerated approval to Leqembi, the FDA used what’s called a surrogate endpoint, an indicator that a drug might be working.
The surrogate endpoint for the Eisai drug was a reduction in amyloid plaque as assessed by an imaging scan of the brain. Those results showed a statistically significant reduction of amyloid plaque that was dose and time dependent. In documents explaining Leqembi’s review, the FDA said its prior evaluation of Aduhelm led it to determine that a reduction in amyloid plaque, as measured by medical imaging, is reasonably likely to predict clinical benefit. The agency thus concluded it is reasonable another therapy that also reduced amyloid has the potential to benefit patients.
“This is exactly the situation for which accelerated approval exists—where the evidentiary criteria for accelerated approval are met, it can provide earlier access to a promising drug to patients with unmet needs,” the FDA said in the Leqembi summary review. “There is substantial evidence that lecanemab reduces Aβ plaques, and this reduction is reasonably likely to result in clinical benefit for patients.”
The accelerated approval pathway enables the FDA to permit a drug to reach the market with less evidence than what’s required in a standard review. Such decisions require companies to confirm a drug’s benefit by conducting additional clinical testing. Aduhelm landed its accelerated approval without having a confirmatory study underway. The Phase 3 clinical trial that serves as Leqembi’s confirmatory study already has results. In addition to being larger study than the Phase 2 trial, the Phase 3 study evaluated patients for longer—18 months versus 12 months for the mid-stage test.
A Deep-dive Into Specialty Pharma
A specialty drug is a class of prescription medications used to treat complex, chronic or rare medical conditions. Although this classification was originally intended to define the treatment of rare, also termed “orphan” diseases, affecting fewer than 200,000 people in the US, more recently, specialty drugs have emerged as the cornerstone of treatment for chronic and complex diseases such as cancer, autoimmune conditions, diabetes, hepatitis C, and HIV/AIDS.
Like the Phase 2 trial, brain imaging was used to assess amyloid in Phase 3. But measuring change in score according to the Alzheimer’s assessment was the main goal of this confirmatory trial. According to that measure, Eisai reported in November that treatment with Leqembi led to a statistically significant 27% slowing of cognitive decline compared to the placebo group. Within hours of Leqembi’s accelerated approval on Friday, Eisai submitted an application seeking full approval of the drug based on the Phase 3 results.
An estimated 6.2 million Americans 65 and older have Alzheimer’s. Not all of them are eligible for Leqembi. The drug’s approval covers early Alzheimer’s with mild cognitive impairment or mild dementia. Leqembi will cost $26,500 a year, a discount to the $37,600 annual price Eisai calculated would reflect the drug’s value. That value was determined using a formula that accounts for the measure of how well and how long a patient lives while taking the drug, patient willingness to pay, offsetting costs compared to the standard of care, and the time a patient is under treatment.
“We would like to give back over half of the societal value to the American people,” Eisai, Inc. Chairman and CEO Ivan Cheung said, speaking during a Saturday briefing with journalists.
In addition to falling below Eisai’s calculated value of the drug, Leqembi’s price is also less than the $28,000 annual cost for Aduhelm (though that represents a 50% cut Biogen made last year to boost sales after many insurers balked at the drug’s initial $56,000 price). But the new Eisai drug’s price is still higher than the $8,500 to $20,600 per year range in which the Institute for Clinical and Economic Review (ICER) calculated the medicine would be cost effective. The drug price watchdog group has expressed skepticism about the drug. In an Alzheimer’s drugs draft report released last month, ICER said while it’s possible that the way the Eisai drug works led to cognitive benefit, “we do not feel that evidence is adequate at this point to assume that clearance of amyloid will necessarily improve cognitive outcomes.”
Amir Tahami, Eisai’s head of global value & pricing, and health economics and outcomes research, said the company used a higher dollar threshold in its calculations. In serious diseases with a high unmet need, there is a higher willingness to pay, he explained. In addition, Eisai’s calculation accounts for the costs associated with the disease and the productivity lost—for patients and their caregivers. Cheung said other think tanks—as well as ICER’s draft report—have also calculated value using higher thresholds of willingness to pay.
Leqembi’s price will not be covered by Medicare, at least not yet. Last year, the Centers for Medicare and Medicaid Services concluded coverage of the class of anti-amyloid antibody drugs would be limited to beneficiaries enrolled in a CMS-approved clinical trial. For more Medicare patients to access Leqembi, Cheung said it will be important to answer CMS’s questions about the drug. He added that Eisai will ask the agency to review the Phase 3 data with FDA in order to open up access to the drug as soon as it secures full regulatory approval.
The Leqembi label does not carry the FDA’s strictest warning. In recent months, three deaths were reported in the open-label extension part of the Phase 3 study. All three patients were reportedly taking blood thinners while receiving lecanemab, which sparked questions about whether the FDA should place a black box warning on the drug’s label. In the summary review, the FDA said the brain bleeding risks can be addressed on the label, which urges caution when using clot-busting drugs in patients who are taking Leqembi. The FDA’s approval letter directs Eisai to conduct additional post-marketing monitoring to assess the bleeding risk associated with the drug. The agency also asked the company to provide twice-yearly reports of such cases.
In a research note sent to investors, William Blair analyst Myles Minter wrote that
while Leqembi’s approval was expected, the decision came with some key differences compared with Aduhelm. For example, the drug label states that the presence of amyloid must be confirmed before starting treatment, a condition not required of Aduhelm. The prescribing information also has stronger monitoring recommendations for managing the brain bleeding complications.
“Eisai has largely maintained the position that the drug is relatively safe, particularly given the comorbidities in the elderly patient population and overall risk/benefit for a progressive neurodegenerative disease,” Minter said. “However, we could see additional warnings in a full approval label, if granted, as more data becomes available particularly from the ongoing open-label safety trial.”
Photo by Eisai
