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# Prothena Scraps Birtamimab After Phase 3 Miss
- URL: https://www.fdaweb.com/prothena-scraps-birtamimab-after-phase-3-miss/
- Published: 2025-05-27T12:00:00.000Z
- Updated: 2026-09-14T15:12:43.000Z
- Author: David McFarland
- Tags: FDA Policy/General, #legacy-id-D5159248

Prothena says it will discontinue the development of birtamimab, its investigational treatment for AL amyloidosis, after the drug failed to meet the primary or secondary endpoints in a Phase 3 clinical trial. AL amyloidosis, which also known as [immunoglobulin light chain amyloidosis](https://www.google.com/search?client=firefox-b-1-d&sca%5Fesv=4b995b00999b8af2&sxsrf=AE3TifP883OD2QL7uMUVjlIA96GV7dS-Jg%3A1748372798439&q=immunoglobulin+light+chain+amyloidosis&sa=X&ved=2ahUKEwix2tecrMSNAxWxGlkFHSCMB2gQxccNegQIEhAB&mstk=AUtExfCCnm-ye-P0i4XG0%5F3CrPLrgU3AA8QsU%5F2pANrTjoa%5Fn6I395vcAZEzxUqllSJywH9F2GcSRtdkJcxtf1c2glcDrLqNyERu3muGYRzBqWhbxlhcDgSD%5FcTCX%5FYI57Zn3gtS3o-1NwCGShNjebWlkRSjBv5TqgENlIRiuMvTzmJ2NfRSuAxJRqwfelNOMjCtrKh30Ao-Ly2pmZ73IKE2T509ZAiTOuzjxyLUXe5radyFVYVFzcdXyzx5IflwxwP5BIhwkW3do3sfQq0QeUak2jeH&csui=3&ref=fdaweb.com), is a condition where abnormal protein deposits (amyloid) build up in various organs and tissues, causing damage and organ dysfunction.

The company says its AFFIRM-AL study, which evaluated birtamimab in 207 patients with newly diagnosed Mayo Stage 4 AL amyloidosis, did not show a statistically significant benefit in reducing all-cause mortality compared to placebo. Secondary measures, including a six-minute walk test and a physical health score, also failed to show improvement.

In addition, the company said it will shut down the open-label extension of the AFFIRM-AL trial and begin taking steps to cut operating costs, including a significant reduction in workforce.