3094 Background: The carcinomembryonic antigen cell adhesion molecule 1 (CEACAM1, CD66a) is a member of the CEA gene family. CEACAM1 interacts homophilically and heterophilically with CEACAM5, and is involved in various anti-proliferative activities. CEACAM1 is expressed on a variety of epithelial and hematological cells, including multiple types of cancer and activated lymphocytes. High CEACAM1 expression in some tumor types is known to be associated with poor disease prognosis. Recently it was demonstrated CEACAM1 is co-expressed on exhausted lymphocytes with other immune checkpoints such as TIM-3 and may regulate downstream activity. CM24 is a novel humanized α-CEACAM1-specific antibody with nM affinity to the N terminal domain of CEACAM1, which blocks intercellular CEACAM1 interactions. Methods: The primary objective was to test the safety and tolerability of CM24 in adult patients with advanced or recurrent cancer. Secondary objectives included assessment of CM24 PK and PD profiles, anti-tumor response and the recommended Phase 2 dose. Patient received IV infusion of CM24 at 7 dose levels ranging between 0.01 and 10 mg/kg in a cycle of 4 doses administered q2wks followed by a 6-week observation only period and additional 6 cycles. Results: 27 patients (median pretreatment of 4 prior regimens; range 2-8, 11 colorectal, 7 melanoma, 4 ovarian, 3 gastric, 2 NSCLC; 13 males, 14 females, mean age of 60 years), were included. Treatment with CM-24 was overall well-tolerated without DLTs up to 10 mg/kg. The most frequent AE was grade 1-3 increased alanine aminotransferase (7 subjects) and the most severe AE was grade 3/4 increase in gamma-glutamyltransferase (4 subjects). Drug-related AEs were observed in 63% of the subjects with grade 3-5 occurred in 3.7%. Eight subjects (29.6%) had stable disease as the best overall response. Median overall survival was 4 (3.4, 8.0) and 6.2 (2.7, 10.2) months for the 3 and 10 mg/kg doses, suggesting dose response. Cmax, AUC and t1/2 increased with increasing dose with the longest t1/2 of 11.2 days obtained at 10mg/kg. The average target occupancy of CM24 at 3mg/kg and 10mg/kg were 75% and 93%, respectively. Conclusions: PK and target-mediated drug disposition analysis suggest that doses higher than 10mg/kg are needed for target saturation at a q2 week regimen while a q3 week regimen is less optimal. A phase 1/2 clinical trial testing CM24 in combination with anti-PD-1 therapy in patients with NSCLC including assessment of CEACAM1 expression is warranted. Clinical trial information: NCT02346955 .
