FDA Approves New Treatment for Hemolytic Anemia in Adults With PK Deficiency

The Food and Drug Administration approved mitapivat (Pyrukynd, Agios) on Thursday to treat hemolytic anemia in adult patients with pyruvate kinase (PK) deficiency. Mitapivat is the first FDA-approved disease-modifying therapy for PK deficiency, a rare, inherited blood disorder that may cause red cell destruction.

Investigators evaluated the effectiveness of mitapivat in two studies: a randomized, double-blind, placebo-controlled clinical study of 80 adults with PK deficiency who did not receive regular blood transfusions and a single-arm study of 27 adults with PK deficiency who received regular blood transfusions. Participants received 50 mitapivat for an average duration of about 24 weeks in the randomized study and an average duration of about 40 weeks in the single-arm study.

In the randomized study, the effectiveness of mitapivat was based upon hemoglobin response (defined as a 1.5 g/dL or greater increase in hemoglobin concentration that was sustained at two or more scheduled assessments). At the end of the study, 40% of participants in the treatment group had a hemoglobin response, compared with zero participants in the placebo group.

In the single-arm study, effectiveness was based on reduction in transfusion burden (at least a 33% reduction in the number of RBC units transfused during the last 24 weeks of treatment compared with the historical transfusion burden on the individual participant). Thirty-three percent of participants who received mitapivat met this reduction in transfusion burden; 22% of participants did not require any transfusions during the last 24 weeks of treatment.

In the approval notice, FDA noted that abruptly stopping mitapivat could worsen premature red blood cell destruction.