Effect of plinabulin, a novel late-clinical stage immunotherapeutic agent on the adaptive and innate immune system.

Abstract

8 Background: Plinabulin (Plin) is a small molecule Dendritic Cell modulator, which in the presence of antigen, increases T-cell proliferation in an antigen-dependent manner marrow. The addition of Plin to Docetaxel (Doc) improved mOS with 4.6 months vs Docetaxel monotherapy, and prolonged DoR with more than 1 year (p < 0.05), which is indicative of an immune-mediated mechanism of action (Mohanlal, ASCO-SITC 2017). Neutrophils are our first line of innate immune defense against foreign invaders. We previously reported that Plinabulin prevents chemotherapy (Chemo) Induced Neutropenia (CIN) in patients receiving Doc or TAC throughout the cycle (Doc, Doxorubicin, Cyclophosphamide) (Blayney ASH 2018, St Gallen 2019). Here we analyzed the onset time of neutrophil increase following Plin administration. In addition, we analyzed the impact of Plin on plasma haptoglobin, which is an acute phase protein with anti-inflammatory effects together with immune-enhancing effects and is an integral part of innate immunity (Kristiansen Nature 2001). Methods: Absolute neutrophil count (ANC) and haptoglobin data were analyzed from Phase 2 study BPI-2358-106 (NCT03294577) with 10 (n = 15), 20 (n = 15) and 30 mg/m2 (n = 12) Plin in Breast Cancer patients receiving TAC. Plin was administered on Day 1. ANC and Haptoglobin were analyzed by a Central Laboratory (Covance), from blood draws at predose, and post-dose Plin at Day 2,3,6,7,8,9,10,11,12,13 and 15, and changes relative to predose value were evaluated. Results: Plin dose-dependently increased ANC within 1 day (P < 0.001) and Haptoglobin within 3 days (P < 0.03) of dosing. Mean haptoglobin (P < 0.0005) and ANC (P < 0.001) levels increased with ~two-fold vs baseline levels. ANC levels remained increased for approximately 1 week and haptoglobin levels for > 3 weeks. Conclusions: Based on Plinabulin’s ability to stimulate the innate system, together with its previously reported evidence as a potent activator of the adaptive immune system (Mohanlal, ASCO-SITC 2017), it is concluded that Plinabulin is a potent stimulator of the adaptive and innate immune system. Clinical trial information: NCT03294577.