Prothena presents data from phase 3 VITAL study

Prothena Corporation presented data from the completed phase 3 VITAL study demonstrating that in a post hoc analysis of patients with Mayo Stage IV AL amyloidosis, a statistically significant survival benefit was observed in those treated with birtamimab at 9 months. The survival benefit of birtamimab in VITAL remained consistent across all key baseline variables in patients with Mayo Stage IV AL amyloidosis. The data were presented in an oral presentation at the 64th American Society of Hematology Annual Meeting and Exposition in New Orleans, LA.Birtamimab is a potential best-in-class amyloid depleter treatment for AL amyloidosis. Based on the totality of the VITAL study data, Prothena has advanced birtamimab into the confirmatory Phase 3 AFFIRM-AL study in patients with Mayo Stage IV AL amyloidosis under a Special Protocol Assessment agreement with the U.S. FDA with a primary endpoint of all-cause mortality at pless than or equal to0.10. Confirmatory Phase 3 AFFIRM-AL topline data is expected in 2024. A post hoc analysis of patients with Mayo Stage IV AL amyloidosis showed a statistically significant survival benefit of 74 percent in patients treated with birtamimab versus a survival benefit of 49 percent in patients on placebo at 9 months. The survival benefit of birtamimab in VITAL remained consistent across all key baseline variables in Mayo Stage IV patients, reinforcing the strength of the survival data in these patients at high risk of early mortality. The sensitivity analysis was performed as part of the post hoc analysis of patients with Mayo Stage IV AL amyloidosis. After adjusting for baseline demographic, clinical, and laboratory variables, the adjusted hazard ratios ranged from 0.336 to 0.465, with no upper bounds of the 90% confidence interval crossing 1, indicating a consistent survival benefit with birtamimab at 9 months. Birtamimab also demonstrated statistically significant improvement over placebo in post hoc analyses of quality of life and cardiac function. Patients treated with birtamimab showed a mean difference of 4.65 in the SF-36v2 PCS over placebo at 9 months. Mayo Stage IV patients treated with birtamimab after 9 months demonstrated an increase of 15.22 meters in the 6-minute walk test, whereas patients treated with placebo had a decrease of 21.15 meters. Birtamimab was generally safe and well tolerated in the overall patient population and in Mayo Stage IV patients. The rates of treatment emergent adverse events were balanced between treatment arms. The rates of treatment-related TEAEs were similar or lower with birtamimab than in the placebo arm of both the overall population and in Mayo Stage IV patients. Consistent with AL amyloidosis, cardiac disorder was the most common class of fatal TEAEs. There were no fatal TEAEs that were considered treatment related.