Preclinical evaluation and phase 1 study of the PI3Kα/δ inhibitor TQ-B3525 in Chinese patients with advanced cancers

BackgroundPhosphatidylinositol 3-kinase (PI3K) inhibitors transformed management of various malignancies. This study preclinically characterized TQ-B3525 (dual PI3K alpha/delta inhibitor) and assessed the recommended phase 2 dose (RP2D), safety, efficacy, and pharmacokinetics in relapsed or refractory (R/R) lymphoma or advanced solid tumors (STs).MethodsOral TQ-B3525 was given at eight dose levels on a 28-day cycle. Primary end points were dose-limiting toxicity (DLT), maximum tolerated dose (MTD), and safety.ResultsTQ-B3525 showed high selectivity and suppressed tumor growth. Between June 12, 2018, and November 18, 2020, 80 patients were enrolled (63 in dose-escalation cohort; 17 in dose-expansion cohort). Two DLTs occurred in two (two of 63, 3.2%) DLT-evaluable patients; MTD was not identified. TQ-B3525 at 20 mg once daily was selected as RP2D. Grade 3 or worse treatment-related adverse events mainly included hyperglycemia (16.3%), neutrophil count decreased (15.0%), and diarrhea (10.0%). Two (2.5%) treatment-related deaths were reported. Sixty patients with R/R lymphoma and 11 advanced STs demonstrated objective response rates of 68.3% and 9.1%, disease control rates of 91.7% and 54.6%, median progression-free survivals of 12.1 and 1.1 months; median overall survivals were not reached.ConclusionTQ-B3525 exhibited rapid absorption and a nearly proportional increase in exposure. Acceptable safety and promising efficacy support further investigation of TQ-B3525 (20 mg once daily) for R/R lymphoma. Considering the black-box warnings associated with several phosphatidylinositol 3-kinase (PI3K) inhibitors, it remains crucial to develop novel PI3K inhibitors with reduce toxicities. This study presents the results of the preclinical and phase 1 study of TQ-B3525, suggesting that TQ-B3525 may be a feasible therapeutic approach in patients with relapsed or refractory lymphomas, with a comparable safety and efficacy profile.