405 CDX1140–01, a phase 1 dose-escalation/expansion study of CDX-1140 alone (Part 1) and in combination with CDX-301 (Part 2) or pembrolizumab (Part 3)

Background CDX-1140 is an agonist anti-CD40 mAb selected to optimize systemic exposure and hence tumor microenvironment (TME) ingress. CDX-1140 activity may be enhanced by combining with CDX-301 (recombinant Flt3L), a dendritic cell growth factor, or with pembrolizumab, an anti-PD-1 mAb. Methods Patients with advanced solid or hematologic (Part 1 only) tumors are enrolled. Part 1 dose-escalation results have been presented (SITC 2019). In Part 2, CDX-1140 dose-escalation (0.09–1.5 mg/kg q4w) is in combination with CDX-301 (75 mcg/kg sc QD x 5 for 2 cycles). In Part 3, CDX-1140 dose-escalation (0.72–1.5 mg/kg q3w) is in combination with pembrolizumab 200 mg q3w. Part 1 and 2 expansion cohorts are dosed at the CDX-1140 MTD, 1.5 mg/kg q4w. Part 3 expansion cohorts are planned. Peripheral blood and tumor biomarkers analysis are ongoing. Results 92 patients have been treated (Part 1 n=57, Part 2 n=31, Part 3 n=4). Part 1 expansion cohorts in SCCHN (n=7) and RCC (n=5) are fully enrolled. Part 2 dose-escalation completed to the highest CDX-1140 dose and a SCCHN expansion cohort is ongoing. Part 3 dose-escalation recently initiated. Safety data is available for 23 and 10 patients at the MTD in Part 1 and 2, respectively. In general, the safety profiles were similar, with arthralgia (52% vs. 50%), pyrexia (44% vs 50%), fatigue (30% vs. 50%), chills (39% vs. 40%), vomiting (30% vs. 20%), nausea (26% vs 40%), myalgia (22% vs. 30%), increased ALT (22% vs. 20%), and increased AST (22% vs. 30%) being the most common drug related AEs at the MTD in Part 1 and 2, respectively. Most AEs were low grade. Across all cohorts, cytokine release syndrome (CRS) (G2 n=4, G3 n=2) occurred in 6 (Part 1 n=2; Part 2 n=4) and pneumonitis (G3) occurred in 5 (Part 1 n=4; Part 2 n=1) patients. Immune activation in the TME consistent with CD40 agonism and increases serum inflammatory cytokines were observed. Evidence of anti-tumor activity/clinical benefit include SD (n=13), tumor cavitation (n=2) and a uPR in solid tumors. A patient with follicular lymphoma has an ongoing durable complete metabolic response. Conclusions The CDX-1140 MTD dose of 1.5 mg/kg, a dose level expected to provide good systemic exposure and TME penetration, is generally well tolerated alone and with CDX-301. Transaminitis and CRS have generally been low grade and infrequent. A cohort combining CDX-1140 with chemotherapy will be initiated in patients with previously untreated metastatic pancreatic adenocarcinoma. Trial Registration NCT03329950 Ethics Approval The study was approved by the following: Providence St. Joseph Health IRB, approval number MOD2020001128; WIRB, approval number 1188814 (Hauke, Gabrail, Bordoni & Gordon); University of Pennsylvania IRB, approval number UPCC 18917; Mount Sinai School of Medicine IRB, approval number 18-00202; Memorial Sloan Kettering Cancer Center IRB, approval number 18-225A; Houston Methodist IRB, approval number MOD00000836 http://dx.doi.org/10.1136/jitc-2020-SITC2020.040