Phase 1 Single and Multiple Ascending Dose Study to Assess the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of AG-946 in Healthy Volunteers
Authors: Iyer Varsha , Merica Elizabeth , Ronseaux Sebastien , Gamache Tressa , Mulrow Nancy J. , Belcijan Anja , Callaghan Michael U. 
Published: November 2021

Abstract
Background: Glycolysis is the primary source of ATP in red blood cells (RBCs), which is critical for maintaining RBC health. Pyruvate kinase red cell isoform (PKR) catalyzes the final step of glycolysis to generate ATP. Enhancing ATP production via PKR activation is under investigation as a potential therapeutic approach in hemolytic anemias. Increased levels of the glycolytic metabolite 2,3-diphosphoglycerate (2,3-DPG) in sickle cell disease (SCD) decreases hemoglobin oxygen affinity and results in increased RBC sickling. PKR activation has been shown to reduce 2,3-DPG. In previous clinical studies in pyruvate kinase deficiency, thalassemia and SCD, treatment with mitapivat, a PKR activator, led to improvements in hemoglobin and markers of hemolysis.
AG-946 is an investigational, next-generation, oral small molecule activator of wild-type and mutant PKR isoforms, with high potency. Modelling from preclinical studies suggest that AG-946 is likely to have a pharmacokinetic (PK) profile that allows for once daily (QD) dosing and long duration of pharmacodynamic (PD) effects in humans. Here we report preliminary blinded results from an ongoing study assessing the safety, tolerability, PK and PD of AG-946 in healthy volunteers (NCT04536792).
Methods: In this phase 1, randomized, double-blind, placebo (P)-controlled study, single ascending oral doses (SAD) or multiple ascending oral doses (MAD) of AG-946 were administered under fasting conditions to healthy men and women (18-55 years of age) in sequential cohorts. In SAD (4 cohorts of 8 subjects each) and in MAD (2 cohorts of 8 subjects each) subjects were planned to be randomized to receive either AG-946 (n=6) or P (n=2). The dose levels studied so far are 1, 3, 10, and 30 mg in SAD and 1 mg QD and 2 mg QD for 14 days in MAD. Safety assessments included vital signs, physical exams, electrocardiograms, clinical laboratory parameters and adverse events (AEs). Serial blood samples were drawn for PK and PD (2,3-DPG; ATP) assessments at regular intervals throughout the study period.
Results: As of June 02, 2021, 39 (median age 33 years; n = 33 male) subjects in SAD and 17 (median age 36 years; all male) subjects in MAD received AG-946 or P. There were 6 (SAD, n = 5; MAD, n = 1) early discontinuations; all were unrelated to study treatment. In SAD, 4/39 (10.3%) subjects experienced ≥ 1 treatment-emergent AE (TEAE); all TEAEs were assessed as mild (Grade [Gr] 1). In MAD 4/17 (23.5%) subjects experienced ≥ 1 TEAE; the majority of the TEAEs were mild (Gr 1), with 1 subject experiencing a serious AE (Gr 2) of exercise-induced rhabdomyolysis 14 days after last dose, considered unrelated to study treatment. All other AEs in SAD and MAD were also considered unrelated to study treatment.
In both SAD and MAD, AG-946 exhibited rapid absorption with median T max (time to maximum concentration) ranging from 0.5 to 1 hour. Following SAD, dose-normalized AG-946 exposures (AUC and C max [area under the curve and maximum concentration observed]) increased with increasing AG-946 doses, suggesting a greater than dose proportional increase in exposure over the tested dose range. Following MAD, AG-946 exposures were higher on Day 14 compared with Day 1, with mean accumulation ratios based on AUC of 3.6 at 1 mg QD and 3.3 at 2 mg QD, and mean accumulation ratios based on C max of 1.95 at 1 mg QD and 1.6 at 2 mg QD.
In both SAD and MAD, an increase in AG-946 dose was associated with a decrease in 2,3-DPG concentrations (Figure 1), and an increase in ATP concentrations (Figure 2). The PD changes were sustained up to 168 hours after a single dose and &gt; 7 days after the last day of multiple QD dosing, consistent with the slow off-rate from PKR.
As expected, no clinically significant changes in Hb have been observed in the SAD or MAD cohorts, to date.
Conclusions: AG-946, a highly potent PKR activator, was well tolerated in healthy volunteers following single dose administrations up to 30 mg and multiple 14-day dosing with 1 mg QD and 2 mg QD. The PK profile of AG-946 supports QD dosing, and is accompanied by sustained dose-dependent increases in ATP and decreases in 2,3-DPG, consistent with activation of the glycolytic pathway. Enrollment into additional SAD and MAD cohorts is ongoing and will be followed by an open-label phase in subjects with SCD.
Figure 1 Figure 1.

Disclosures
Iyer: Novartis: Current equity holder in publicly-traded company; Agios Pharmaceuticals: Current Employment, Current holder of stock options in a privately-held company. Ronseaux: Agios Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Gamache: Agios Pharmaceuticals: Current Employment. Callaghan: Agios Pharmaceuticals: Current Employment.