Background
Phase III, international, double-blind, randomized, placebo-controlled trial (ENERGIZE). 194 adults (≥18 years) with non-transfusion-dependent (NTD) alpha-thalassemia or NTD beta-thalassemia and hemoglobin ≤10 g/dL at 70 hospitals in 18 countries. Mitapivat is an oral activator of red blood cell pyruvate kinase (PKR), targeting the metabolic defect in thalassemia that contributes to ineffective erythropoiesis and hemolytic anemia. No oral disease-modifying therapies were approved for NTD beta-thalassemia at study initiation; no agents approved for alpha-thalassemia.
Interventions and follow up
Arm A: Mitapivat 100 mg orally twice daily x 24 weeks (n=130)
Arm B: Placebo BID x 24 weeks (n=64)
Primary endpoint: Hemoglobin response (≥1.0 g/dL increase in mean Hgb from baseline at weeks 12–24)
mFollow up: 24 weeks (double-blind) + open-label extensio
Arm B: Placebo BID x 24 weeks (n=64)
Primary endpoint: Hemoglobin response (≥1.0 g/dL increase in mean Hgb from baseline at weeks 12–24)
mFollow up: 24 weeks (double-blind) + open-label extensio
Results
Hgb response: 42% (55/130) vs 2% (1/64), LS mean difference 41%, 95% CI 32–50%, P<.0001
Fatigue improvement: Reported as secondary endpoint (specific data in full publication)
Fatigue improvement: Reported as secondary endpoint (specific data in full publication)
Adverse events
Main adverse events: AEs 83% (mitapivat) vs 79% (placebo). Most common with mitapivat: headache (22% vs 10%), initial insomnia (14% vs 5%), nausea (12% vs 8%), upper respiratory infection (11% vs 6%). No deaths reported in double-blind period. Tolerable profile.
Conclusions
Mitapivat significantly improved hemoglobin levels in adults with NTD alpha- or beta-thalassemia, providing the first evidence of an effective oral disease-modifying therapy for these conditions. FDA approved mitapivat for non-transfusion-dependent thalassemia in December 2025 (brand name Pyrukynd extended indication).
Key Limitations
Key Limitations: Short 24-week treatment period does not establish long-term durability. NTD thalassemia is heterogeneous — responders vs non-responders and genotype-specific responses need characterization. Hgb response threshold (1.0 g/dL) as surrogate endpoint; patient-reported outcomes and clinical event reduction are longer-term goals. Comparator is placebo only — no comparison with chelation, hydroxyurea, or transfusion-based management.
Clinical Context
Mitapivat (Pyrukynd, Agios) was previously approved for pyruvate kinase deficiency. ENERGIZE expands the indication to the much larger NTD thalassemia population. This is the first oral disease-modifying therapy approved for alpha-thalassemia. A companion trial (ENERGIZE-T) evaluated mitapivat in transfusion-dependent thalassemia. The mechanism (PKR activation improving RBC survival) applies broadly across hemolytic anemias.
References
References: Taher AT et al, Lancet 2025 (ENERGIZE)