Prothena Halts Drug and Plans Major Layoffs After Second Rare Disease Trial Failure

Prothena has permanently stopped development of birtamimab, its anti-amyloid antibody, after the drug failed to meet the primary endpoint of improving all-cause mortality in the Phase III AFFIRM-AL trial for AL amyloidosis. It also missed all key secondary endpoints, including physical health outcomes and the six-minute walk test.135

This is the second late-stage failure for birtamimab, after the drug also missed goals in a previous mid-stage study.13

In response to the trial's failure, Prothena will initiate 'substantial' layoffs and other spending cuts, with specifics on workforce reduction to be announced in June. The company had 163 employees at the end of December 2024.123

Prothena's board is evaluating broader business options with financial advisors to act in the best interest of its shareholders, with further updates to come after review.13

Despite this setback, Prothena still has partnered programs with Bristol Myers Squibb, Novo Nordisk, and Roche, and expects initial Phase 1 data for its Alzheimer's disease candidate PRX012 in August 2025.1

The company reported $418.8 million in cash at the end of March 2025, with previous projections to end the year with $301 million before the trial failure and anticipated cost cuts.1

Sources:

1. https://www.fiercebiotech.com/biotech/prothena-reburies-drug-after-second-swing-rare-disease-misses-plans-substantial-layoffs

2. https://endpts.com/prothenas-amyloidosis-drug-flops-again-spending-and-staff-cuts-are-on-the-way/

3. https://www.biospace.com/drug-development/prothena-looks-at-business-options-as-phase-iii-al-amyloidosis-trial-fails

5. https://m.fastbull.com/en/news-detail/prothena-stock-plummets-following-failed-phase-3-trial-news73000202521848243