A phase II, multicenter, single-arm study of parsaclisib, a PI3K delta inhibitor, in relapsed or refractory follicular lymphoma in China: Updated data from the study.

7574 Background: For Follicular lymphoma (FL) patients (pts) of 3rd or higher line, treatment options are limited. Parsaclisib is a potent, highly-selective, next-generation PI3Kδ inhibitor. Initial safety and efficacy data were previously presented (Zhong Zheng et al. ASH 2021; NCT04298879). Here, we report safety, efficacy and survival data of the multicenter, open-label phase 2 study of parsaclisib in 3rd or higher line FL pts in China. Methods: Key eligibility included, age ≥ 18 years, histologically confirmed FL grade 1, 2, or 3a, ≥ 2 prior systemic therapies, ECOG PS ≤ 2, and ineligible for hematopoietic stem cell transplantation (HSCT). Pts received parsaclisib 20 mg once daily (QD) for 8 weeks followed by 2.5 mg QD, till disease progression (PD), unacceptable toxicity, death or withdrawn consent. Prophylaxis for Pneumocystis jirovecii pneumonia (PJP) was required. Primary endpoint was objective response rate (ORR) evaluated by an Independent Review Committee (IRC) according to Lugano 2014 criteria, secondary endpoints included: duration of response (DOR), PFS, OS, and safety and tolerability. Results: As of the data cutoff date (Dec 12, 2021), 61 pts (median age: 50yr; male [n = 35, 57.4%]) were enrolled. Forty-eight pts remained on treatment and 13 pts had discontinued study treatment mainly due to PD (n = 11). With a median follow-up time 9.5 months (range 6.0-19.7months), the median duration of treatment was 251.0 days (range: 23.0-589.0 days). All 61 pts were evaluable for response, the ORR and complete response rate (CRR) were 86.9% (n = 53, 95% CI: 75.8-94.2%) and 31.1% (n = 19, 95% CI: 19.9-43.3%), respectively. The median time to response (TTR) was 8.0 weeks (95% CI: 7.9-8.0%), and the median DOR was not reached (95% CI: 9.2 months-NC), and 43 of 53 pts with CR or PR still retained CR or PR. As data cutoff, eleven (17.9%) pts had disease progression, the median PFS was not achieved. Three pts died data as data cutoff, the median OS was not achieved. Among the 61 treated pts, 48 (95.1%) pts experienced at least 1 treatment-emergent adverse events (TEAEs), with the most common TEAEs being neutrophil count decreased (49.2%), white blood cell count decreased (32.8%). Twenty-seven patients (44.3%) experienced grade ≥ 3 TEAEs, the most common grade ≥ 3 TEAEs was neutrophil count decreased (n = 10, 16.4%). Conclusions: Parsaclisib demonstrated promising efficacy, and acceptable safety profile. These results suggest that parsaclisib could benefit 3rd or higher line Follicular lymphoma patients. Clinical trial information: NCT04298879.