Plinabulin, a novel small molecule clinical stage IO agent with anti-cancer activity, to prevent chemo-induced neutropenia and immune related AEs.

Abstract

126 Background: Plinabulin (Plin) is a small molecule with tumor-inhibiting and immune-enhancing effects by targeting Dendritic Cells (DCs). In preclinical studies, Plin induces DC maturation and the production of MHCII, CD40, CD80 and CD86 and related antigen-specific T-cell activation. Plin had synergistic anticancer efficacy with PD1+CTLA4inhibitors in animal models. In addition, Plin increases expression of IL-1β, IL-6, IL-12 in DC cell, which cytokines protect neutrophils against apoptosis. In a Phase 2 (Ph2) trial, the addition of Plin to Docetaxel (Plin+Doc; n = 38) in NSCLC patients (pts) with a measurable lesion, improved mOS with 4.6 mo vs Doc alone (n = 38). DOR (a marker of immune effect) was ~1 yr longer (P < 0.05) with Plin+Doc vs Doc alone. Plin exerted immune-enhancing effects (DOR), without increasing Immune-Related AEs (IR-AEs). This may suggest that Plin exerts immune-enhancing and anti-inflammatory effects. Methods: Prospective, randomized Ph2 clinical trial (NCT00630110) and non-clinical studies. Results: In-vitro screens showed that Plin is a PDE4-inhibitor, and clinical evidence (p < 0.03; n = 90) of PDE4-inhibition with Plin was observed in Ph2. PDE4-inhibitors have steroid-like effects and are approved for the treatment of Inflammatory disorders, and thus have the potential to prevent IR-AEs. In addition, Plin prevented chemo-induced Neutropenia (CIN), through a mechanism, different from G-CSF, in non-clinical (with various chemotherapies) and Ph2. In Ph2, Gr 4 Neutropenia occurred in 5% with Plin+Doc vs 33 % off pts with Doc (p < 0.0003) in Cycle 1, day 8. Plin is given 30 min after chemo (on the same day of chemo), and does not cause bone pain. G-CSF is given 24 hr after chemo, and causes bone pain in most pts. Conclusions: Plin exerts anticancer immune-enhancing effects, combined with anti-inflammatory effects, due to PDE4-inhibition. Plin holds the promise of an agent with anti-cancer efficacy, while also mitigating IR-AEs and CIN. Therefore, Plin is an attractive candidate for combination therapy with PD1-inhibitors (or PD-L1 inhibitors), PD1+CTLA-inhibitor, or PD1-inhibitor/chemotherapy.