EX-99.1 2 d891971dex991.htm EX-99.1 EX-99.1 Exhibit 99.1 PRESS RELEASE Prothena Announces Phase 3 AFFIRM-AL Clinical Trial for Birtamimab in Patients with AL Amyloidosis Did Not Meet Primary Endpoint Birtamimab did not meet the primary endpoint of time to all-cause mortality or the secondary endpoints Birtamimab development will be discontinued, including stopping the open label extension of the AFFIRM-AL clinical trial Company will decrease ongoing operating expenses, including an expected substantial reduction in organizational size, and plans to provide a further update in June ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────── DUBLIN, Ireland, May 23, 2025 - Prothena Corporation plc (NASDAQ:PRTA) today announced the Phase 3 AFFIRM-AL clinical trial evaluating birtamimab in patients with AL amyloidosis did not meet its primary endpoint (HR=0.915, p-value=0.7680). Based on these results, the Company will discontinue the development of birtamimab, including stopping the open label extension of the AFFIRM-AL clinical trial. “This is not the outcome that we expected, and we are surprised and disapp…
Open exhibit ↗Current Report · Items 8.01, 9.01 · 8-K
PROTHENA CORP PUBLIC LTD CO
PRTANASDAQEQUITYCurrent
Other Events
Item 8.01 Other Events. On May 23, 2025, Prothena Corporation plc issued a press release announcing results from the Phase 3 AFFIRM-AL clinical trial for birtamimab in patients with AL amyloidosis and the discontinuation of further development of birtamimab. A copy of that press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.
Company context
Prothena Corporation plc is a late-stage clinical biotechnology company with expertise in protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare peripheral amyloid diseases. Fueled by its deep scientific expertise built over decades of research, Prothena is advancing a pipeline of therapeutic candidates for a number of indications and novel targets for which its ability to integrate scientific insights around neurological dysfunction and the biology of misfolded proteins can be leveraged. Prothena’s pipeline includes both wholly-owned and partnered programs being developed for the potential treatment of diseases including ATTR amyloidosis with cardiomyopathy, Alzheimer’s disease, Parkinson’s disease and a number of other neurodegenerative diseases. For more information, please visit the Company’s website at www.prothena.com and follow the Company on X (formerly Twitter) @ProthenaCorp.