Selective PI3Kδ Inhibitor Parsaclisib Combined with HDAC Inhibitor Chidamide in Patients with Relapsed/Refractory Peripheral T-Cell Lymphoma: Preliminary Results of a Phase Ib/Ⅱ Study

Background: Peripheral T-cell lymphoma (PTCL) is a highly heterogenous non-Hodgkin lymphoma with poor survival. Pts with relapsed/refractory PTCL (r/r PTCL) have extremely poor prognosis and limited treatment options. Conventional salvage treatments have a median progression-free survival (PFS) of only 3-4 months. Parsaclisib, a potent, highly-selective, next-generation PI3Kδ inhibitor has shown encouraging efficacy and favorable safety profile in B-cell malignancies. We developed a phase Ib/II study to evaluate the safety and efficacy of parsaclisib with HDAC inhibitor (HDACi) chidamide in r/r PTCL (NCT05083208). Here, we report the preliminary results of this study.

Method: Eligible pts were ≤ 75 years old adults with histologically confirmed PTCL who received ≥ prior line of systemic therapy. Phase Ib dose-escalation study determined the maximum tolerated dose (MTD) of parsaclisib with chidamide using a 3 + 3 design. Parsaclisib was administered once daily at 3 dose levels (dose-level (DL) 1: 10 mg; DL2: 15 mg; DL3: 20mg) in the first 8 weeks followed by 2.5 mg QD in the subsequent treatment. Chidamide was administered at a fixed dose of 20 mg twice a week throughout the study. Once the MTD was established, pts were enrolled into phase 2 study to further characterize safety and efficacy. MTD of parsaclisib and objective response rate (ORR) were the primary endpoints; complete response rate (CRR), PFS, overall survival (OS) and tolerability were secondary endpoints. Prophylaxis for Pneumocystis jirovecii pneumonia (PJP) and cytomegalovirus (CMV) infection in the first 8 weeks were required.

Results: From March 2022 to July 27, 2023 (date cut-off), 11 pts were recruited with a median age of 52 (39-74) years old. The median number of prior systemic therapies was 2 (1-5). Of 6 pts treated at DL1, 1 had dose-limiting toxicity (DLT) (grade 3 elevation of ALT/AST). No DLT was observed in 3 pts at DL2 and 2 at DL3. The DLT was resolved subsequently but the patient died from lymphoma progression. Treatment-emergent adverse events (TEAEs) were observed in all pts. The TEAEs were mainly hematologic toxicities and gastrointestinal reactions, most of which were grade 1/2. Grade 3/4 TEAEs were neutropenia (n=4), leukopenia (n=1), elevation of ALT/AST (n=1), and diarrhea (n=1) (Table 1). TEAE led to dose interruption in one patient. In 9 pts evaluable for responses (1 withdrew from this study and 1 was unevaluable), 5 (55.6%) pts achieved complete response (CR) and one (11.1%) partial response at the first efficacy assessment. In 7 pts previously exposed to chidamide, 4 pts achieved CR and 2 of them had a PFS > 16 months (Table 2 and Figure 1).

Conclusion: Preliminary data demonstrated that selective PI3Kδ Inhibitor parsaclisib with HDACi chidamide was tolerable and produced promising responses in r/r PTCL, including patients previously exposed to chidamide. This trial is currently ongoing.