Study of the Safety and Efficacy of STI-6129 in Patients With Relapsed or Refractory Systemic AL Amyloidosis

Inclusion Criteria: * Confirmed diagnosis of AL amyloidosis by tissue biopsy of an involved organ, or a surrogate site such as abdominal fat demonstrating amyloid deposition by mass spectrometry * The presence of a monoclonal light chain protein in serum * Relapsed or refractory AL amyloidosis is defined as patients who have received ≥ 2 lines of treatment. Patients must have received at least one proteasome inhibitor during their prior therapy. Patients who have received prior daratumumab treatment or prior stem cell transplantation remain eligible. Patients may have relapsed with disease progression or have been refractory to their last prior line of treatment. Progression of disease that develops \> 60 days after the last dose of a treatment regimen in a patient who achieved at least a partial response (PR) defines a relapse. Refractory systemic AL amyloidosis is defined as the development of disease progression during therapy with an anti-AL amyloidosis treatment regimen or within 60 days of the last dose of an anti-AL amyloidosis treatment regimen or the achievement of less than a PR after ≥ 2 cycles * Measurable disease defined as the finding by serum-free light chain (FLC) assay that the difference between the involved and uninvolved FLC (dFLC) is ≥ 50 mg/L * Pulse oximetry ≥ 92% on room air * ECOG performance status of 0, 1, or 2 * Willing to comply with the study schedule and all other protocol requirements * Females of childbearing potential (FCBP) must have 2 nega…