Part 1 is the open label, dose-escalation phase Ib portion of the study to establish an MTD/RP2D of APG-115 in combination with toripalimab. Dose levels/schedule of APG115 will be tested: 50mg, 100mg, 150mg, and 200mg, QOD with 2 weeks on 1 week off as a cycle of 21 days (3 weeks), toripalimab will administrated with label dose.~Part 2 is the phase II portion of the study to evaluate the clinical efficacy and safety of the RP2D of APG-115 in combination with label dose of toripalimab in patients with advanced liposarcoma. In this part, Simon's two-stage design (Simon R (1989). Controlled Clinical Trials 10: 1-10.) will be used. The null hypothesis that the true response rate of combination is 30% or lower will be tested against a one-sided alternative. In the first stage, 19 patients will be accrued. If there are 3 or fewer responses in these patients, the study will be stopped. Otherwise, 15 additional patients will be accrued for a total of 34. The null hypothesis will be rejected if 7 or more responses are observed in 34 patients. This design yields a type I error rate of 0.05 and power of 90%.
Part 1 is a phase Ib standard 3 + 3 design, will be employed to determine the MTD of APG-115 by assessing the DLT of APG-115 in combination with PD-1 inhibitor(toripalimab) in advanced solid tumors.~Part 2 is a Simon two-stage phase II study design. At RP2D of APG-115 in combination with toripalimab in advanced liposarcoma, approximately 34 patients will be treated with the combination until disease progression, unacceptable toxicity, or another discontinuation criterion is met.