ETAVOPIVAT TREATMENT FOR UP TO 12 WEEKS IN PATIENTS WITH SICKLE CELL DISEASE IS WELL TOLERATED AND IMPROVES RED BLOOD CELL HEALTH

ABSTRACT

Background: Etavopivat, an investigational, once-daily, selective, activator of erythrocyte pyruvate kinase (PKR) increases PKR activity, resulting in decreased 2,3-DPG and increased ATP in red blood cells (RBCs) of healthy volunteers and patients (pts) with sickle cell disease (SCD).1,2 Aims: We report results of an open-label (OL) extension cohort from a Phase 1 study (NCT03815695) designed to characterize the safety and clinical activity of etavopivat at a maximal pharmacodynamic dose in pts with SCD. Methods: 15 pts were enrolled to receive etavopivat 400 mg once daily for 12 wks, followed by a 4-wk follow-up. Assessments included safety, pharmacokinetics, pharmacodynamics, RBC health parameters and systemic markers of SCD pathophysiology. Results: Of 15 pts (age 32.3 ±10.1 yr;HbSS/SC n=13/2), 14 completed 12-wks of treatment (tx);1 pt discontinued tx after ∼2 wks. Etavopivat 400 mg once daily was generally well tolerated. Adverse events (AEs) reported during tx and follow-up were commonly low grade (Gr) and consistent with pts' SCD. Gr1-2 AEs in >2 pts (n [%]) were sickle cell pain events (9 [60%]);headache (5 [33%]);and upper respiratory tract infection (3 [20%]). The Gr3-4 AE in >1 pt was sickle cell vaso-occlusion (VOC;4 [27%]). On-tx serious adverse events (SAEs;1 pt each) were Gr3 VOC post Gr3 COVID (not tx-related) and Gr3 left femoral deep vein thrombosis (possibly related, resulting in tx discontinuation as stated above). SAEs (1 pt each) during the 4-wk follow-up were Gr3 acute chest syndrome + Gr3 VOC, Gr3 non-cardiac chest pain and Gr3 syncope (all unrelated). Observed increases in ATP and decreases in 2,3-DPG were durable over 12 wks of etavopivat tx. Etavopivat tx normalized hemoglobin (Hb)S-oxygen affinity to that of HbA. Etavopivat tx over 12 wks improved overall sickle RBC health, demonstrated by a reduction in point of sickling as well as improved measures of deformability and hydration of sickle RBCs (all P<0.01;Figure). Etavopivat tx over 12 wks was associated with a sustained significant increase in Hb compared with baseline (BL;P<0.0001), with mean maximal increase of 1.5 (range 0.7-2.3) g/dL. Ontx increase in Hb >1g/dL was achieved in 11 (73%) pts, for whom the mean maximal Hb increase was 1.8 (1.2-2.3) g/dL. Absolute reticulocytes, indirect bilirubin and lactate dehydrogenase significantly decreased from BL and were sustained over the 12wk period (all P<0.05), indicative of increased RBC lifespan and decreased hemolysis. Several markers of disease activity significantly decreased from BL during daily etavopivat tx, including the inflammatory marker tumor necrosis factor-α , which decreased by 35% (P<0.001). Based on preliminary exploratory analysis with an aggregate duration of etavopivat exposure of 3.32 pt-yrs in the OL cohort, a decrease in the trend for VOC Hospitalizations was observed annualized historical and on-tx VOC Hospitalization rates were 0.93 and 0.30, respectively;the 1 on-tx VOC Hospitalization was COVID-related. Summary/Conclusion: Etavopivat 400 mg once daily for up to 12 wks demonstrated a tolerable safety profile and showed improvements in various markers of RBC health in pts with SCD. Rapid and sustained increases in Hb were associated with decreases in reticulocyte counts and markers of hemolysis, supporting increased sickle RBC lifespan and improved anemia. Together, these results support further evaluation of etavopivat in the Phase 2/3 Hibiscus Study (NCT04624659) currently enrolling pts. (Figure Presented).