A multicenter open-label phase 1 study evaluating the safety and tolerability of HMPL-306 in patients with locally advanced or metastatic solid tumors with IDH mutations.

Abstract

TPS3159 Background: Isocitrate dehydrogenase (IDH) is a rate-limiting tricarboxylic acid cycle enzyme with 3 isoforms. Mutations in IDH1 and IDH2 result in gain-of-function activity that can cause tumor formation and/or progression and have been associated with various tumor types. Therefore, selective, single mutant IDH (mIDH) isotype inhibitors (mIDH1 or mIDH2) can lead to insufficient efficacy and the potential for tumor resistance. HMPL-306 is an innovative, small-molecule, orally available, highly selective, potent inhibitor of both mIDH1 and mIDH2. Clinical development of a compound that concurrently targets, inhibits, and suppresses multiple mIDHs could lead to significant and durable clinical benefit for patients (pts) with solid tumors harboring IDH mutations. Methods: This is a phase 1, open-label, dose escalation (Part 1) and dose expansion (Part 2) study to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of HMPL-306 in pts ≥18 years with locally advanced or metastatic solid tumors with any IDH mutations. HMPL-306 will be administered orally, once daily in a 28-day continuous dosing treatment cycle. The HMPL-306 dose will be escalated in Part 1 according to the modified toxicity probability interval-2 (mTPI-2) design in 4 cohorts in approximately 15-20 pts: 50, 100, 150, and 200 mg. Eligible pts must have locally advanced or metastatic solid tumors with IDH1 or IDH2 mutations. The primary objectives are to evaluate safety, dose limiting toxicities (DLTs), tolerability, maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), and PK. Approximately 95 pts will be enrolled at the RP2D in Part 2 to further characterize the safety, tolerability, PK, PD, and preliminary anti-tumor activities of HMPL-306. Part 2 will include 5 dose expansion cohorts: cholangiocarcinoma (n = 20), skeletal chondrosarcoma (n = 20), low-grade glioma (n = 20), perioperative low-grade glioma (n = 15), any other solid tumor harboring an IDH1/2 mutation (n = 20). All pts will continue treatment until disease progression, unacceptable toxicity, withdrawal of consent, or at the investigator’s discretion. Safety will be assessed based on reports of adverse events including clinical laboratory testing, vital signs, physical examinations, and electrocardiograms. All pts who receive any study treatment will be included in safety and efficacy analyses. Antitumor activity based on investigator-assessed overall response will be evaluated using descriptive analyses. Objective response rate will be calculated with 95% confidence interval using the Clopper-Pearson method. The Kaplan-Meier method will be used to summarize the time-to-event data such as progression-free survival and duration of response. No statistical hypothesis testing is planned. Enrollment started February 2021.