Long-term mitapivat treatment is safe and efficacious in patients with sickle cell disease

In a phase 1 open-label study (ClinicalTrials.gov identifier: NCT04000165), mitapivat, a pyruvate kinase (PK) activator that is approved by the US Food and Drug Administration for treating anemia of PK deficiency, showed promise as a disease-modifying therapy for sickle cell disease (SCD). We now report updated findings from a phase 1/2 study with a median follow-up of 132 weeks (2.53 years), involving 15 patients, 13 from the initial study and 2 new to mitapivat. Patients with hemoglobin SS (HbSS) aged ≥18 years started mitapivat 50 mg twice daily for 4 weeks followed by a dose escalation to 100 mg twice daily for another 20 weeks to complete a 24-week core period. Nine patients continued treatment for >120 weeks, resulting in 1884 patient-weeks of exposure to mitapivat. Common treatment-emergent adverse events (TEAEs) included vaso-occlusive crises (VOCs), decreased hormone levels, arthralgia, cough, and COVID-19 infection. Changes in laboratory values were not clinically significant. Serious TEAEs were mainly VOCs in 10 patients, and lung infections in 3; all VOCs were linked to known triggers. No TEAEs led to discontinuation of mitapivat. Of 15 patients, 14 (93%) had at least a 1 g/dL increase in Hb at some point within the 24-week core period, with a mean increase of 1.38 ± 0.88 g/dL. Improvements in Hb, hemolytic markers, oxygen affinity, sickling kinetics, and the ratio of adenosine triphosphate to 2,3-diphosphoglycerate were sustained during the extension period. These findings suggest that long-term mitapivat is safe and effective for patients with SCD, warranting further investigation in the ongoing phase 3 study (RISE UP; ClinicalTrials.gov identifier: NCT05031780). This trial was registered at www.ClinicalTrials.gov as #NCT04610866.