After Eisai and Biogen’s Alzheimer’s disease medicine Leqembi debuted to a somewhat tepid market reaction, the companies have pointed to more convenient diagnosis and administration as two factors set to eventually accelerate the rollout.
With the FDA approval of the first blood-based test to help diagnose Alzheimer’s, the first component of that plan has been set in motion. But, in a note to clients Monday, Mizuho analyst Salim Syed argued that bending the Leqembi sales curve may still take time.
The FDA on Friday approved Fujirebio Diagnostics’ Lumipulse test for diagnosing Alzheimer’s. The biomarker test measures the plasma ratio between pTau217 and beat amyloid 1-42 for the early detection of amyloid plaques, which are targeted by Leqembi and Eli Lilly’s rival treatment Kisunla.
To Syed, while the nod is welcome news for the entire Alzheimer’s space, payer reimbursement for the test and physician user behavior remain key factors for Leqembi.
To determine whether Leqembi is the right treatment for a patient, doctors use either an amyloid PET scan or a cerebrospinal fluid (CSF) test to confirm the presence of amyloid plaques. These diagnostic methods are costly, time consuming or invasive, and their availability is limited by healthcare infrastructure, which Eisai and Biogen suggest have hindered Leqembi’s rollout.
Fujirebio’s Lumipulse could potentially replace PET scans or CSF tests “in the context of other clinical information,” Syed pointed out in his Monday note.
As the FDA flagged in a press release, Lumipulse is “not intended as a screening or stand-alone diagnostic test and other clinical evaluations or additional tests should be used for determining treatment options.”
To win the FDA’s clearance, Lumipulse showed a positive predictive value of 91.7% and a negative predictive value of 97.3%. The higher the scores, the fewer false positive reports or erroneous negative readouts, respectively.
The better concordance on negative results means that doctors might be more inclined to follow up and confirm a positive diagnosis with additional PET scans or CSF tests, effectively using Lumipulse as a “rule-out” test, Syed figured.
Under this scenario, while patients may still need one of those cumbersome tests before getting on Leqembi, the blood-based test could free up resources by triaging most ineligible patients.
About 50% of patients who get into a neurologist’s office are not eligible for anti-amyloid treatment such as Leqembi because their disease is too advanced, Biogen CEO Chris Viehbacher said during an investor call in February.
“If we could actually triage some of these patients, particularly at the primary care level, then we can actually get a higher quotient of patients who visit neurologists actually being eligible for treatment,” he explained while referencing blood-based tests.
Even with the Lumipulse FDA approval, physicians may need education on its use and interpretation of the test results, especially if the goal is to potentially use it in place of PET and CSF tests, Syed added.
Before Lumipulse, some lab-developed blood tests were commercially available for Alzheimer’s. But they weren’t able to replace PET or CSF tests because many doctors don’t trust them, Biogen’s head of North America, Alisha Alaimo, said during an investor event in March, as quoted by Mizuho. Conversely, doctors may embrace an FDA-approved test with accuracy above 90%, she noted.
The next big piece is reimbursement: Lumipulse will likely need coverage to make a significant impact on the Leqembi launch, Syed said.
An FDA approval likely won’t impact reimbursement dynamics unless the maker of the test pursues an “advanced diagnostic laboratory test” (ADLT) designation by the Centers for Medicare & Medicaid Services, a Leerink Partners team led by Puneet Souda said in a Friday note. ADLTs are priced separately from other clinical diagnostic lab tests.
“I think the next stage will be generating data so that payers and others are confident that it can adequately represent the Medicare population, which tends to be the broader population,” Biogen’s head of development, Priya Singhal, M.D., said of blood-based tests on the company’s February call.
FDA approvals for blood-based diagnostics and a subcutaneous drug formulation are the two key elements that Eisai and Biogen hope could drive Leqembi’s long-term growth. For the 12 months that ended in March, Eisai recorded 26.1 billion Japanese yen ($171 million) in U.S. Leqembi revenue. The company has forecast the number will rise to 40 billion Japanese yen for the current fiscal year ending in March 2026.