Mitapivat

Mitapivat (AG-348) is a first-in-class, orally bioavailable, small molecule allosteric activator of the red blood cell pyruvate kinase isoenzyme (PKR) and, with similar potency, the liver (PKL) and tumor-associated (PKM2) isoforms. The compound was discovered at Agios Pharmaceuticals through a rational drug design program targeting the glycolytic defect that underlies pyruvate kinase deficiency (PKD), a rare autosomal recessive enzymopathy characterized by reduced adenosine triphosphate (ATP) production, shortened erythrocyte lifespan, and chronic hemolytic anemia. Mitapivat binds at a pocket on the dimer-dimer interface of the PKR tetramer, distinct from the endogenous allosteric activator fructose-1,6-bisphosphate (FBP) binding domain, and induces the active R-state conformation of the enzyme, thereby increasing its affinity for the substrate phosphoenolpyruvate (PEP) and enhancing the catalytic conversion of PEP and adenosine diphosphate to pyruvate and ATP [1, 2]. This allosteric activation is effective across both wild-type PKR and a broad range of PKLR-mutant enzymes, restoring enzymatic activity, improving protein thermostability, and increasing intracellular ATP levels while reducing the glycolytic intermediate 2,3-diphosphoglycerate (2,3-DPG) in patient-derived erythrocytes [3].

The compound received its first regulatory approval from the United States Food and Drug Administration on 17 February 2022 under the trade name PYRUKYND for the treatment of hemolytic anemia in adults with pyruvate kinase deficiency who are not regularly transfused, on the basis of the Phase 3 ACTIVATE trial, in which 40 percent of patients randomized to mitapivat achieved a sustained hemoglobin increase of 1.5 g/dL or greater compared with zero percent in the placebo arm (p < 0.0001) [4, 5]. The companion Phase 3 ACTIVATE-T trial in regularly transfused PKD adults demonstrated a 37 percent transfusion reduction rate [6]. In December 2024, the FDA granted a second approval under the trade name AQVESME for the treatment of anemia in adults with alpha- or beta-thalassemia (both transfusion-dependent and non-transfusion-dependent), supported by the Phase 3 ENERGIZE trial in non-transfusion-dependent thalassemia (42 percent hemoglobin response versus 2 percent placebo, p < 0.0001) and the Phase 3 ENERGIZE-T trial in transfusion-dependent thalassemia (significant transfusion burden reduction) [7, 8, 9]. Mitapivat is additionally under Phase 2/3 clinical investigation for sickle cell disease (RISE UP trial), where the orthogonal mechanism of PKR activation (increasing ATP and decreasing 2,3-DPG to reduce hemoglobin S polymerization and red blood cell sickling) offers a mechanistically distinct approach from hydroxyurea and gene therapy [10, 11].

Pharmacokinetics in humans are characterized by high oral bioavailability (73 percent), rapid absorption (median time to peak concentration 1.75 hours), extensive plasma protein binding (approximately 98 percent), a large volume of distribution (42.5 liters at steady state), and a terminal elimination half-life of approximately 46 hours after oral dosing [12]. Metabolism is predominantly hepatic via cytochrome P450 3A4 (CYP3A4), yielding 17 characterized metabolites, none of which individually exceeds 10 percent of circulating radioactivity; elimination proceeds through both urine (50 percent) and feces (40 percent), with less than 3 percent excreted unchanged in urine [12]. The compound induces CYP2B6, CYP2C8, CYP2C9, CYP2C19, and UGT1A1, and is a substrate and inhibitor of P-glycoprotein, producing clinically significant drug-drug interactions with strong CYP3A4 inhibitors and inducers and with narrow-therapeutic-index substrates of the induced enzymes [13]. The recommended dosing schedule is a 4-week titration from 5 mg in the published literature to 20 mg in the published literature and then to the target maintenance dose of 50 mg in the published literature; abrupt discontinuation is contraindicated owing to a risk of acute hemolysis, and a structured tapering schedule is mandated in the prescribing label [13].

This monograph reviews the chemistry, structural class, and synthesis of mitapivat; the allosteric mechanism of PKR activation in molecular detail; the comprehensive human pharmacokinetic record; the preclinical pharmacology across PKLR genotypes; the clinical evidence base in pyruvate kinase deficiency, thalassemia, and sickle cell disease; sourcing and quality verification considerations for research-grade material; reconstitution and handling; stack-interaction implications for combination research; the adverse-event and safety profile including the acute hemolysis discontinuation signal and the hormonal effects in males; and a comparative assessment of five alternative agents (etavopivat, voxelotor, luspatercept, hydroxyurea, crizanlizumab) against mitapivat on five competency standards. Mitapivat is approved by the United States Food and Drug Administration for two indications. It is additionally available as a research-grade preparation from multiple chemical suppliers for in vitro and preclinical investigation; investigators should obtain analytical confirmation of identity and purity on every lot.