A Study to Evaluate the Efficacy and Safety of Birtamimab in Mayo Stage IV Patients With AL Amyloidosis

This is a Phase 3 multicenter, global, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of birtamimab in Mayo Stage IV patients with AL amyloidosis (i.e., Double-blind Phase), followed by a long-term, open-label extension (i.e., Open-label Extension \[OLE\] Phase). The primary objective of the Double-blind Phase is to evaluate the efficacy of birtamimab by assessing time to all-cause mortality. All patients will receive bortezomib-containing chemotherapy regimen as standard of care. For the Double-blind Phase of the study, approximately 220 newly diagnosed Mayo Stage IV patients with AL amyloidosis will be enrolled and randomized in a 2:1 ratio to birtamimab or placebo. Subjects will remain on study until study completion, when the pre-defined number of events (all-cause mortality) have been reached. After completion of the Double-blind Phase, eligible subjects may enter the optional OLE Phase, in which all subjects will receive open-label birtamimab treatment, regardless of Double-blind Phase randomized treatment assignment. Treatment in the OLE Phase will continue for an additional 24 months or until birtamimab is commercially available in a subject's country of residence, whichever occurs first (in accordance with country-specific regulations). The primary objective of the OLE Phase is to evaluate the long-term safety of birtamimab plus standard of care in Mayo Stage IV subjects with AL amyloidosis.