Phase 1 clinical trial of the PI3Kδ inhibitor YY-20394 in patients with B-cell hematological malignancies

YY-20394, an oral phosphatidylinositol 3-kinase delta (PI3Kδ) inhibitor, was investigated in a first-in-human study of patients with relapsed or refractory B-cell malignancies. During dose escalation, 25 patients received 20–200 mg of YY-20394 daily. The primary outcome measures were tolerability and dose-limiting toxicity (DLT). The secondary outcomes were pharmacokinetic parameters, progression-free survival (PFS) and the objective response rate (ORR). Since no patients experienced DLT, the maximum tolerated dose (MTD) was not reached. The majority (≥ 5%) of drug-related adverse events were ≥ grade III, being neutropenia (44.0%), pneumonia (16.0%), hyperuricemia (12.0%), lymphocythemia (8.0%), leukopenia (8.0%) and pneumonitis (8.0%). The overall ORR was 64.0% (95% confidence interval (CI): 45.2, 82.8%) including 5 patients with complete remission (CR), 11 with partial remission (PR), 2 with stable disease (SD) and 7 with progressive disease (PD), while the disease control rate (DCR) was 72.0% (95% CI: 54.4, 89.6%). The ORR of 10 patients with follicular lymphoma was 90%. The median PFS time was 255 days. One PR patient with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) who received 40 mg q.d. had a durable response of around 36 months. The median PFS time of 10 patients with follicular lymphoma was 300 days. A recommended phase 2 dose of 80 mg q.d. was established. Considering that YY-20394 was well-tolerated with promising preliminary efficacy, further development is warranted. Trial registration clinicaltrials.gov, NCT03757000, retrospectively registered, November 28, 2018, https://clinicaltrials.gov/ct2/show/NCT03757000?term=NCT03757000&draw=2&rank=1 .