FT-4202, an oral PKR activator, has potent antisickling effects and improves RBC survival and Hb levels in SCA mice

Abstract

Sickle cell anemia (SCA) results from an abnormal sickle hemoglobin (HbS). HbS polymerizes upon deoxygenation, resulting in red blood cell (RBC) sickling and membrane damage that cause vaso-occlusions and hemolysis. Sickle RBCs contain less adenosine triphosphate and more 2,3-diphosphoglycerate than normal RBCs, which allosterically reduces hemoglobin (Hb) oxygen (O2) affinity (ie, increases the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen [P50]), potentiating HbS polymerization. Herein, we tested the effect of investigational agent FT-4202, an RBC pyruvate kinase (PKR) activator, on RBC sickling and membrane damage by administering it to Berkeley SCA mice. Two-week oral FT-4202 administration was well tolerated, decreasing HbS P50 to levels similar to HbA and demonstrating beneficial biological effects. In FT-4202–treated animals, there was reduced sickling in vivo, demonstrated by fewer irreversibly sickled cells, and improved RBC deformability, assessed at varying shear stress. Controlled deoxygenation followed by reoxygenation of RBCs obtained from the blood of FT-4202–treated mice showed a shift in the point of sickling to a lower partial pressure of oxygen (pO2). This led to a nearly 30% increase in RBC survival and a 1.7g/dL increase in Hb level in the FT-4202–treated SCA mice. Overall, our results in SCA mice suggest that FT-4202 might be a potentially useful oral antisickling agent that warrants investigation in patients with SCA.

Safety, Pharmacokinetics, and Pharmacodynamics of Etavopivat (FT‐4202), an Allosteric Activator of Pyruvate Kinase‐R, in Healthy Adults: A Randomized, Placebo‐Controlled, Double‐Blind, First‐in‐Human Phase 1 Trial

“…Because ATP and 2,3-DPG are endogenous molecules present in whole blood at high levels, the low, middle, and high quality-control calibration standards were prepared in deionized water (surrogate matrix). Whole blood samples (15 μL) were spiked with stable isotope-labeled internal standard ( 13 C 10 , 15 N 5 -ATP, and D 3 -2,3-DPG), processed by protein precipitation extraction, and analyzed using ZIC-pHILIC separation with Turbo Ion Spray tandem mass spectrometry detection. The high-performance liquid chromatography column (2.1 × 50 mm SeQuant ZIC-pHILIC) was kept at 40 o C. Negative (M-H) − ions for ATP and 2,3-DPG and their respective internal standards, 13 C 10 , 15 N 5 -ATP, and D 3 -2,3-DPG, were monitored in multiple reaction monitoring mode (mass transitions monitored were m/z 506.0>159.0 and 521.0>159.0 for ATP and 13 C 10 , 15 N 5 -ATP, and 265.0>166.8 and 268.0>169.8 for 2,3-DPG and D 3 -2,3-DPG).…”

“…In SCA models, etavopivat treatment reduced RBC sickling and deformability, leading to an increase in RBC survival of nearly 30%. 15 In RBCs from previously untreated patients with homozygous HbS, etavopivat increased the oxygen affinity of hemoglobin, with a mean decrease of 2.33 mm Hg in the partial pressure of oxygen at which Hb-oxygen saturation of 50% is achieved (P 50 ). 16 In vitro, no safety signals for etavopivat were identified by the human ether-à-go-go-related gene patch clamp assay (data on file at Forma).…”

“…The chemical structure is shown in Figure S1. In SCA models, etavopivat treatment reduced RBC sickling and deformability, leading to an increase in RBC survival of nearly 30% 15 . In RBCs from previously untreated patients with homozygous HbS, etavopivat increased the oxygen affinity of hemoglobin, with a mean decrease of 2.33 mm Hg in the partial pressure of oxygen at which Hb‐oxygen saturation of 50% is achieved (P 50 ) 16 …”

Diagnosis, monitoring, and management of pyruvate kinase deficiency in children

“…While phase III trials for mitapivat use in adults are complete, there will need to be further investigation of its safety, tolerability, and efficacy in children due to its known side effects in addition to aromatase inhibition, which has been seen in male subjects 44–47 . Additionally, there are other PK activators in clinical development that may be available to adults and children in the future 48,49 . If PK activators such as mitapivat are efficacious and safe in children, trialing a PK activator in young children, particularly with at least one PKLR missense mutation, may prevent the future need for splenectomy.…”

“…[44][45][46][47] Additionally, there are other PK activators in clinical development that may be available to adults and children in the future. 48,49 If PK activators such as mitapivat are efficacious and safe in children, trialing a PK activator in young children, particularly with at least one PKLR missense mutation, may prevent the future need for splenectomy.…”