SummaryStem cell factor (SCF), also known as mast cell growth factor, kit ligand, and Steel factor, is the ligand for the tyrosine kinase receptor (SCFtL) that is encoded by the c-kit proto-oncogene. We analyzed the effects of recombinant human SCF (r-hSCF, 5-50 btg/kg/day, injected subcutaneously) on mast cells and melanocytes in a phase I study of 10 patients with advanced breast carcinoma. A wheal and flare reaction developed at each r-hSCF injection site; by electron microscopy, most dermal mast cells at these sites exhibited extensive, anaphylactic-type degranulation. A 14-d course ofr-hSCF significantly increased dermal mast cell density at sites distant to those injected with the cytokine and also increased both urinary levels of the major histamine metabolite, methyl-histamine, and serum levels of mast cell 0rFive subjects developed areas of persistent hyperpigmentation at r-hSCF injection sites; by light microscopy, these sites exhibited markedly increased epidermal melanization and increased numbers of melanocytes. The demonstration that r-hSCF can promote both the hyperplasia and the functional activation of human mast cells and melanocytes in vivo has implications for our understanding of the role of endogenous SCF in health and disease. These findings also indicate that the interaction between SCF and its receptor represents a potential therapeutic target for regulating the numbers and functional activity of both mast cells and cutaneous melanocytes.

Pyruvate kinase deficiency is a chronic hemolytic anemia caused by mutations in PK-R, a key glycolytic enzyme in erythrocytes. These 2 phase 1 randomized, placebo-controlled, double-blind healthy-volunteer studies assessed the safety, tolerability, and pharmacokinetics/pharmacodynamics of AG-348, a first-in-class allosteric PK-R activator. Twelve sequential cohorts were randomized 2:6 to receive oral placebo or AG-348, respectively, as a single dose (30-2500 mg) in the single-ascending-dose (SAD) study (ClinicalTrials.gov: NCT02108106) or 15-700 mg every 12 hours or 120 mg every 24 hours, for 14 days in the multiple-ascending-dose (MAD) study (ClinicalTrials.gov: NCT02149966). All 48 subjects completed the fasted SAD part; 44 of 48 completed the MAD (2 discontinued because of adverse events [AEs], 2 withdrew consent). The most common treatment-related AEs in AG-348-treated subjects were headache (16.7% [SAD] and 13.9% [MAD]) and nausea (13.9%, both studies). AE frequency increased at AG-348 doses ≥ 700 mg (SAD) and at 700 mg every 12 hours (MAD); 1 grade ≥ 3 AE occurred in the latter cohort. Pharmacokinetics were favorable with low variability. Dose-dependent changes in blood glycolytic intermediates consistent with glycolytic pathway activation were observed at all MAD doses, supporting future trials investigating the potential of AG-348 for treating PK deficiency or other anemias.

No abstract

INTRODUCTION: Pyruvate kinase deficiency (PKD) is an inborn error of metabolism affecting children and adults that results in lifelong hemolytic anemia and is associated with serious long-term comorbidities such as poor growth and development in children and chronic iron overload in adults. PKD is caused by a functional deficiency of the R-isoform of pyruvate kinase (PK-R) caused most often by a missense mutation. As a result of deficiency of this terminal enzyme in glycolysis, blood 2,3-DPG levels are elevated and ATP levels are low. AG-348 is a novel, first-in-class, small molecule allosteric activator of PK-R that directly targets the underlying metabolic defect in PKD. Preclinical studies demonstrated that AG-348 increases the activity of both wild type and various mutated PK-R enzymes. The key objectives of these first-in-human, Phase I, randomized, double-blind, placebo-controlled single (SAD) and multiple ascending dose (MAD) studies are to identify a safe and pharmacodynamically-active dose and schedule for AG-348 to be used in subsequent clinical studies in subjects with PKD [NCT02108106; NCT202149966]. METHODS: In the SAD, healthymen and women (non-childbearing potential) aged 18-60 years were randomized to receive a single oral dose of AG-348 or placebo (P). Six cohorts were evaluated, each containing 8 subjects (6 AG-348, 2 P), starting with 30 mg in cohort 1 followed by 120, 360, 700, 1400 and 2500 mg in cohorts 2-6, respectively. In the ongoing MAD, 2 cohorts (120 mg bid and 360 mg bid) of 8 subjects each (6 AG-348, 2 P) have completed 14 days of dosing and 2 weeks of follow-up. In both studies, safety assessments included adverse events (AEs), vital signs, ECG and clinical laboratory parameters. Serial blood samples are drawn for assessment of PK and PD parameters (2,3-DPG and ATP) pre-dose and at regular intervals thereafter at multiple doses in both the SAD and MAD studies. Preliminary results are reported here; final results will be available at the time of presentation. RESULTS: In the SAD, all 48 subjects enrolled completed the study (47 males and 1 female; mean age 40 years). A preliminary analysis of safety data indicated that 19/48 (39%) subjects receiving AG-348 or placebo under fasted and/or fed conditions experienced at least 1 treatment-emergent AE during the study. All AEs were mild or moderate (Grade 1 and 2) in severity, and the most common were nausea (n=5; 10%) and headache (n=7; 14%). In the 2 completed MAD cohorts (13 males; 3 females; mean age 44 years), 8/16 (50%) of subjects receiving AG-348 or P experienced 11 AEs. All AEs were mild (n=10) or moderate (n=1) and the most frequent were venipuncture bruises. Frequency of AEs by treatment group will be presented. There were no serious AEs, discontinuations due to AEs, or dose-limiting toxicities in either study. Maximum tolerated dose was not reached in the SAD and dose escalation continues in the MAD. In SAD cohorts 1-6, exposure to single doses of AG-348 increased in a dose-proportional manner (mean plasma Cmax, AUC0-12hr and AUC0-72hr) (Figure 1 SAD study). Absorption was rapid, with a median Tmax of 0.75–4.0 h. Expected changes in pharmacodynamic markers including decrease in 2,3-DPG concentration (SAD [Figure 2] and MAD studies) and increase in ATP concentration (MAD study) were observed and will be presented in greater detail. CONCLUSION: AG-348 had a favorable safety profile and was well tolerated in healthy subjects based on preliminary analysis of subjects receiving a single dose up to 2500 mg or multiple bid doses up to 360 mg for up to 14 days. AG-348 also demonstrated a desirable PK profile, with rapid absorption, low PK variability and dose-proportional exposure with PD effect as demonstrated on 2,3-DPG (Figure 2) and ATP. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures Yang: Agios Pharmaceuticals: Employment, Stockholder Other. Merica:Agios Pharmaceuticals: Employment, Stockholder Other. Chen:Agios Pharmaceuticals: Employment, Stockholder Other. Cohen:Agios Pharmaceuticals: Consultancy. Goldwater:PAREXEL International: Employment. Hill:Agios Pharmaceuticals: Employment, Stockholder Other. Kim:Agios Pharmaceuticals: Employment, Stockholder Other. Kosinski:Agios Pharmaceuticals: Employment, Stockholder Other. Kung:Agios Pharmaceuticals: Employment, Stockholder Other. Silver:Agios Pharmaceuticals: Consultancy. Utley:Agios Pharmaceuticals: Employment, Stockholder Other. Agresta:Agios Pharmaceuticals: Employment, Stockholder Other.