Prothena decimated as it drops development of AL amyloidosis drug

Shares of Irish biotech firm Prothena (Nasdaq: PRTA) dropped as much as 70% to $11.15 on Monday after its main drug for treating the rare disease AL amyloidosis failed in a crucial clinical trial.

As a result, the company is discontinuing development of NEOD001, an investigational antibody that was being evaluated for the treatment of AL amyloidosis. The decision was based on results from the Phase IIb PRONTO study and a futility analysis of the Phase III VITAL study.

Based on the results from the Phase IIb PRONTO study, which did not meet its primary or secondary endpoints, the company asked the independent data monitoring committee (DMC) of the Phase III VITAL study to review a futility analysis of the ongoing VITAL study. The DMC recommended discontinuation of the VITAL study for futility. Prothena therefore decided to discontinue all development of NEOD001, including the VITAL study as well as the open label extension studies.