Prothena Corporation plc (NASDAQ:PRTA) released data from the Phase 3 AFFIRM-AL clinical trial evaluating birtamimab in patients with AL amyloidosis on Friday.
AL (amyloid light-chain) amyloidosis is a systemic disease where abnormal proteins, called amyloid fibrils, accumulate in various organs. It’s the most common type of systemic amyloidosis.
The Phase 3 AFFIRM-AL trial enrolled 207 newly diagnosed patients. Birtamimab was given to the active arm every 28 days at a dose level of 24 mg/kg (maximum dose not to exceed 2500 mg).
Patients in both the active and control arms received a bortezomib-containing chemotherapy regimen as the standard of care, and the use of daratumumab was allowed.
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The trial 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 disappointed by these results…,” said Gene Kinney, President and Chief Executive Officer, Prothena. “With these results, we believe that the most appropriate action is to discontinue all development of birtamimab.”
In the Phase 3 AFFIRM-AL clinical trial, the primary endpoint of time to all-cause mortality was not met for patients treated with birtamimab.
In addition, neither of the secondary endpoints: 6-minute walk test distance (nominal p-value=0.5288) and Short Form-36 version 2 Physical Component Score (nominal p-value=0.9597).
Birtamimab was generally safe and well-tolerated, consistent with its established safety profile.
“While we are all disappointed with today’s results, Prothena has meaningful data readouts and pipeline updates over the next 18 months,” said Daniel G. Welch, Chair of Prothena’s Board of Directors.
“We look forward to initial data from the Phase 1 ASCENT clinical trials on PRX012 in Alzheimer’s disease expected in August, and program updates from our partners at Roche expected mid-year, Novo Nordisk expected in 2H25, and Bristol Myers Squibb expected in 2026. The company and board have begun the work to thoughtfully and expeditiously decrease spend, including but not limited to an expected substantial workforce reduction, and evaluate with its financial advisors business options in the best interest of its shareholders.”
In June, the company expects to provide details of plans to reduce ongoing operating expenses. Once the analysis and plans are finalized, the company will communicate the results of reviewing its business options as appropriate.
Price Action: At the last check on Tuesday, PRTA stock was down 26.80% at $4.82 during the premarket session.
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