Parsaclisib for the treatment of primary autoimmune hemolytic anemia: Results from a phase 2, open‐label study

Abstract Autoimmune hemolytic anemia (AIHA) is a group of acquired autoimmune disorders characterized by red blood cell hemolysis. In a phase 2, open‐label, multicenter study, adults with warm AIHA, cold agglutinin disease, or mixed‐type AIHA were administered once‐daily 1.0 or 2.5 mg parsaclisib (selective phosphoinositide 3‐kinase δ inhibitor) orally for 12 weeks, followed by an extension period. Dose increases (for AIHA worsening) or decreases (for tolerability) were permitted. Primary efficacy endpoint was the proportion of patients with complete (≥12 g/dL hemoglobin [Hgb]) or partial (10–12 g/dL Hgb or ≥2 g/dL increase from baseline) response at any visit during weeks 6–12 not attributable to transfusion. Among 25 enrolled patients (median age, 63 y), 16 (64%) achieved a partial or complete Hgb response during weeks 6–12. Responses were observed by week 1 in 52.0% of patients with incremental improvements during weeks 6–12 and sustained responses during the extension period. Responses were higher among patients with warm AIHA versus other types (75.0% vs. 44.4%). Clinically meaningful improvements in Functional Assessment of Chronic Illness Therapy‐Fatigue scores were observed at weeks 6 and 12. All patients had treatment‐emergent adverse events (TEAEs), most commonly diarrhea (32.0%) and pyrexia (28.0%). Grade ≥3 TEAEs occurred in 13 patients (52.0%). TEAEs considered possibly related to treatment occurred in 11 patients (44.0%). No dose reductions were required; six patients (24%) discontinued for a TEAE. In summary, parsaclisib was well tolerated and resulted in substantial improvements in Hgb response at week 1, with durable responses through the extension period. Clinical trial registration This trial was registered at ClinicalTrials.gov (NCT03538041).