With Eisai and Biogen’s Leqembi and Eli Lilly’s Kisunla launching onto the market, the 2024 Clinical Trials of Alzheimer’s Disease conference focused on the role these drugs might play, as well as combination therapies and innovative new treatment options.
Riding the momentum generated by the approvals and rollout of Eisai and Biogen’s Leqembi and Eli Lilly’s Kisunla, Alzheimer’s researchers gathered last month in Madrid for the 2024 Clinical Trials of Alzheimer’s Disease (CTAD) conference. One key topic of conversation was how these anti-amyloid antibodies will be used in the overall treatment scheme.
“This is a breakthrough time when disease-modifying agents are starting to come of age for Alzheimer’s disease,” Howard Fillit, co-founder and chief science officer at the Alzheimer’s Drug Discovery Foundation, told BioSpace. “I saw several sessions on some new ideas about using these drugs as maintenance therapy . . . and how we’re going to use [in] combination therapy.”
Also on display at the conference were ongoing efforts to improve safety and efficacy, the potential of combination treatments and promising data readouts of novel therapies. With 500,000 people diagnosed with Alzheimer’s every year in the U.S. alone, the global therapeutics market is expected to reach $9.2 billion by 2030. After decades of failure, the space is progressing at speeds unseen in the past.
“After years and years and years of investment, it sort of feels like a lot of things are coming to a head in a positive way,” said Lisa Ricciardi, CEO of Cognition Therapeutics.
A Key Role for Anti-Amyloid Antibodies
Fillit believes the future of Alzheimer’s treatment lies in combination therapies—a topic on which he led a roundtable discussion at CTAD. While currently approved anti-amyloid antibodies Leqembi and Kisunla are expected to become the standard of care for the disease, removing amyloid plaques is not the whole story.
“The monoclonal antibodies show a 30% slowing of Alzheimer’s progression, but the goal is to reach 100%,” Fillit said. “Combination therapies could be a step towards this.”
For example, he continued, future treatment paths may combine anti-amyloid antibodies with anti-tau and anti-inflammatory therapies. Around a quarter of novel drugs currently in development address the neuroinflammation aspect of Alzheimer’s, he noted.
Another topic of interest, Fillit said, is adjusting the protocols for Leqembi and Kisunla for therapeutic maintenance. Kisunla is currently dosed until amyloid has been cleared from the brain. Leqembi can be dosed indefinitely, though most data at this point goes only to 18 months.
“Even though the PET scans turn negative and the amyloid plaques are gone, the disease seems to march on,” Fillit said. Continuous treatment, such as once a month at a reduced dosage, could potentially maintain the equivalent of a remission in disease to keep beta-amyloid from reaccumulating, according to Fillit.
Lowering ARIA Risk
R. Nolan Townsend, CEO of Lexeo Therapeutics, told BioSpace that finding ways to reduce the rates of amyloid-related imaging abnormalities (ARIA)—brain swelling associated with amyloid-targeting therapies—was a primary emphasis at CTAD.
Lilly presented results from its TRAILBLAZER-ALZ 6 study, which sought to assess how different doses of Kisunla might influence the frequency of ARIA. The company found that a modified titration arm significantly lowered ARIA-E, a type of swelling caused by fluid leakage.
Notably, Leqembi and Kisunla are considered higher risk for patients who carry two copies of the APOE4 gene, a genetic variation that leads to a high risk of developing Alzheimer’s and accounts for about 15% of all cases of the disease, as these individuals are at an increased risk for ARIA.
At CTAD, Lexeo presented data from the first clinical trial to target the underlying genetic cause of APOE4-associated Alzheimer’s. LX1001 is a one-time gene therapy that delivers the protective APOE2 allele to the central nervous system of patients carrying two copies of APOE4. APOE2 is associated with significantly lower risk of Alzheimer’s disease onset and slower disease progression.
Lexeo’s Phase I/II study enrolled 15 homozygous APOE4 patients with mild cognitive impairment or mild to moderate Alzheimer’s disease. After a single dose of the gene therapy, all participants showed APOE2 protein expression in the cerebrospinal fluid (CSF) at 12 months, a majority experienced stabilization in amyloid pathology and more than two-thirds saw consistent reductions across CSF tau biomarkers, Lexeo reported. So far, no signs of ARIA have been observed or are expected to be seen with Lexeo’s gene therapy.
“Any step forward for [Alzheimer’s] patients is helpful,” Townsend said. “To be able to provide a complete therapy with no ARIA, that’s even more helpful.”
Lexeo plans to engage with the FDA and sees a potential path to accelerated approval using surrogate endpoints, such as APOE2 expression and tau PET imaging, Chief Development Officer Sandi See Tai told BioSpace. The company is considering an initial focus on moderate patients, an area of unmet need where the gene therapy has shown greater signaling data, she added.
A Daily Oral Option
While Lexeo progresses its one-time gene therapy, Cognition Therapeutics is taking a different approach with CT1812, a daily pill. CT1812 is an oligomer antagonist that penetrates the blood-brain barrier and binds to the sigma-2 receptor complex to displace toxic amyloid beta oligomers. This approach targets the disease earlier in the Alzheimer’s cascade before the oligomers have a chance to bind to the synapses and cause neural injury.
If approved, “we feel like this would be a great drug to start [treatment] with,” Ricciardi said, pointing to the small molecule’s accessibility, clean safety profile and “low overhead.”
At CTAD, Cognition presented a pre-specified analysis from its Phase II SHINE study, which tested CT1812 in patients with mild to moderate Alzheimer’s. Participants with lower baseline readings of the P-tau217 protein—an established blood-based biomarker for Alzheimer’s—saw a 95% slowing of cognitive decline as measured by the ADAS-Cog 11 and 108% slowing of decline on the MMSE, two different tests used to measure cognitive impairment.
P-tau217 is key, Ricciardi told BioSpace, because patients who can benefit the most can now be easily identified with a simple blood test. “It’s a game changer,” she said.
Cognition is looking ahead to a meeting with the FDA following the completion of the Phase II trial where the company will develop a Phase III study approach, Ricciardi said.
Could Stem Cells Treat Alzheimer’s?
At Regeneration Biomedical (RBI), founder and president Christopher Duma is trying something way outside the box, delivering stem cells directly into the brains of Alzheimer’s patients. RBI presented data at CTAD from three patients treated in a Phase I study of its adipose-derived stem cells administered into the lateral ventricles of the brain. At 12 weeks, levels of p-tau and beta-amyloid were reduced and MMSE scores trended toward cognition improvements in two of three subjects, the company reported. No safety signals were observed in the first cohort.
“Alzheimer’s disease is a disease of the whole brain,” Duma told BioSpace. “You can’t just target one area of the brain and fix [it].” Duma wanted an approach that would have a bathing effect on the brain that could bypass the blood-brain barrier while also targeting the spinal cord. “It’s all connected by one thing—the ventricular system in the brain.”
RBI’s therapeutic approach starts with removing stem cells via liposuction from a patient’s fat tissue. The stem cells are then taken to a lab where the cells expressing Wnt, a signaling protein known to stimulate other stem cells, are expanded. Those expanded stem cells are then administered back into the patient via a port just under the scalp that delivers the stem cells directly to the brain. The administered Wnt-expressing cells potentially “wake up” the existing stem cells in the brain to trigger regrowth of brain tissue, stop inflammation and repair the waste disposal system, Duma explained.
Duma likened the stem cells to a vaccine. “You’re going to need boosters to keep reminding the stem cells to get going again,” he said.
He also sees potential for combining the stem cell therapy with an anti-amyloid that would clear the plaques out to increase the stem cells’ efficacy. “Perhaps the synergy of those two would be very exciting. We’re open to a clinical trial with that.”
