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a secondary goal of the study. Other goals were positive changes, as seen in brain images, of amyloid levels in the brain and the volume of the hippocampus, the part of the brain associated with long-term memory. Earlier this month, Eisai and Biogen reported success on these fronts, without any significant safety issues. The most common side effects were considered mild: infusion-site reactions and brain swelling. Tariot said this swelling is expected in a treatment that works to remove plaque in the brain, and it’s seen in other antibody drugs, including aducanumab.
The BAN2401 study used an “adaptive” design, which allowed investigators to step in and tweak the study midstream, an approach intended to more quickly identify the best dose. Speaking at AAIC, Lynn Kramer, Eisai’s chief of clinical development and chief medical officer, said the top dose was given to the most number of patients. That dose was tested in 414 total patients, 253 of which received the drug monthly, and another 161 who received the drug bi-weekly. The drug’s effect on amyloid was strongest in the group that received this high dose bi-weekly, with 81 percent of these patients showing reduction in the protein buildup at 18 months.
One tweak made midstream was moving patients to different treatment groups. While these changes might have helped Eisai and Biogen more quickly find and test the best dose, they may have also affected the statistical analysis. Kramer said that in 2014, a health authority outside of the U.S. asked that patients who carry Apo-E4, a gene considered a risk factor in developing Alzheimer’s, not to be randomized to the bi-weekly, high-dose group. Also, patients who have that gene but had yet to reach six months of treatment were to discontinue treatment at that dose. Tariot noted that those steps might have removed patients most likely to show decline, affecting the results seen in this key test group.
The removal of the Apo-E4 patients prompted Evercore ISI analyst Umer Raffat to ask whether BAN2401 worked as well in Apo-E4 carriers as in other patients, and if it didn’t, whether removing those patients from the high-dose group might have actually pumped up the observed effect of the drug. Carriers of the gene did not respond as well to tests of earlier experimental drugs, he wrote in a research note.
Still, he noted some points that weigh in BAN2401’s favor and played down the role of the Apo-E4 gene in efficacy. If the gene was the key factor in the BAN2401 results, the patient group that received the highest dose of the drug monthly—which had more carriers of the gene compared to the placebo group—should have performed worse than those receiving the high dose biweekly. It didn’t.
Howard Fillit, chief science officer of the Alzheimer’s Drug Discovery Foundation, said he was not too surprised that the clinical trial had different results at 18 months than it did at 12. Alzheimer’s is a slowly progressive disease, and an additional six months of treatment might have made a difference, he said.
Fillit added that the study supports new approaches for enrolling and evaluating patients in clinical trials. He points to cancer, where patients are matched to clinical trials based on biological indicators. Fillit says that when he was involved in Alzheimer’s clinical trials in the early 1980s, researchers had no idea whether the patients enrolled in the study had the disease. Decades since, that approach hasn’t changed much. In Eli Lilly’s tests of solanezumab, brain imaging found that as many as 35 percent of patients in the studies had no amyloid plaque and did not have Alzheimer’s, he said. But in the BAN2401 study, measuring amyloid provided a biomarker useful for both enrolling patients and also evaluating the efficacy of the drug.
“A modern clinical trial [for Alzheimer’s] is going to be more like precision medicine, the way we do it in cancer,” Fillit said.
Though BAN2401’s results at 18 months are encouraging, its success was seen only on the secondary goals. Both Fillit and Tariot say the drug needs more testing. That means the companies will probably need to prepare for a larger Phase 3 clinical trial. Eisai’s Kramer said that the companies plan to talk with regulators to find out what will be necessary to move the drug forward.
Eisai and Biogen have been working together in an Alzheimer’s alliance since 2014. The companies are sharing in the development of four drugs, including BAN2401. Aducanumab, currently in Phase 3 testing, is another. And at AAIC, Eisai and Biogen also presented data from a mid-stage study of a third, elenbecestat.