Why Is Prothena Stock Trading Lower On Tuesday?

Core Viewpoint - Prothena Corporation plc announced disappointing results from the Phase 3 AFFIRM-AL clinical trial for birtamimab, leading to the decision to discontinue its development [3][4]. Group 1: Clinical Trial Details - The Phase 3 AFFIRM-AL trial involved 207 newly diagnosed patients, with birtamimab administered every 28 days at a dose of 24 mg/kg, not exceeding 2500 mg [2]. - Both active and control groups received a bortezomib-containing chemotherapy regimen, with the use of daratumumab permitted [2]. Group 2: Trial Outcomes - The trial did not meet its primary endpoint of time to all-cause mortality (HR=0.915, p-value=0.7680) [3][4]. - Secondary endpoints, including the 6-minute walk test distance (nominal p-value=0.5288) and Short Form-36 version 2 Physical Component Score (nominal p-value=0.9597), were also not met [5]. Group 3: Company Response and Future Plans - Prothena's CEO expressed surprise and disappointment at the trial results, stating that discontinuing birtamimab's development was the most appropriate action [4]. - The company plans to reduce spending, including a substantial workforce reduction, and will evaluate business options to benefit shareholders [6]. - Upcoming data from the Phase 1 ASCENT clinical trials on PRX012 in Alzheimer's disease is expected in August, with additional program updates from partners anticipated in the coming years [6]. Group 4: Market Reaction - Following the announcement, Prothena's stock (PRTA) fell by 26.80%, trading at $4.82 during the premarket session [7].