Pharmacokinetic/pharmacodynamic (PK/PD) profile of AG-120 in patients with IDH1-mutant cholangiocarcinoma from a phase 1 study of advanced solid tumors.

4082 Background: Somatic mutations in isocitrate dehydrogenase 1 (IDH1) produce the oncometabolite D-2-hydroxyglutarate (2-HG). AG-120 is a first-in-class selective inhibitor of mutant IDH1 (mIDH1) under evaluation in an ongoing phase 1 study in patients with mIDH1 advanced solid tumors, including cholangiocarcinoma (CC) (NCT02073994). Objectives for this abstract were to 1) characterize the PK profile of AG-120 and the relationship between AG-120 exposure and 2-HG suppression, and 2) evaluate the influence of intrinsic patient factors on AG-120 clearance, in patients with mIDH1 CC. Methods: AG-120 was administered orally once daily (QD) or twice daily (BID) in continuous 28-day cycles. As of Dec 5, 2016, 60 of 73 patients enrolled with mIDH1 CC had PK/PD samples available for analysis at 100 mg BID, 300 mg QD, 400 mg QD, 500 mg QD, 800 mg QD, and 1200 mg QD in dose escalation (n = 24) and 500 mg QD (n = 36) in dose expansion. Blood (n = 60) and fresh tumor biopsy samples (n = 14) were collected to assess AG-120 and 2-HG using qualified liquid chromatography-tandem mass spectrometry methods. Results: Following both single and multiple doses, AG-120 plasma exposure increased less than dose proportionally from 100 to 1200 mg. Mean terminal half-life was 38.4–85.8 h, supporting a QD dosing regimen. Following multiple doses, steady state was reached within 15 days, with approximately 2-fold accumulation in plasma AG-120 exposure. No patient-specific factors were identified as clinically significant covariates affecting AG-120 plasma clearance. After multiple doses, plasma 2-HG levels were reduced (up to 98.4% inhibition, achieving levels similar to those in healthy volunteers) and tumor biopsy 2-HG levels were also substantially reduced (by up to 99.9%) at all dose levels tested. The 500 mg QD dose resulted in the largest magnitude of 2-HG inhibition vs. other dose levels. Conclusions: AG-120 demonstrated a long half-life in patients with mIDH1 CC and robustly inhibited 2-HG in plasma and tumor samples. These PK/PD data, along with emerging safety and clinical activity data, support the selection of 500 mg QD for future clinical investigation. Clinical trial information: NCT02073994.