Abstract 561: Preclinical efficacy data for the anti-CEACAM5-DM4 ADC SAR408701 supports further development in lung and gastro-intestinal cancers

Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is a cell-surface glycoprotein highly expressed in several tumor types including non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and gastric cancer (GC). SAR408701 is an antibody-drug conjugate (ADC) which consists of anti-CEACAM5 antibody conjugated to the maytansinoid DM4 cytotoxic agent, a highly potent tubulin inhibitor. SAR408701 was investigated in a First in Human trial (FIH) in patients with advanced solid tumors. During the early dose escalation phase, preliminary anti-tumor activity was observed with objective response reported in 3 patients with CRC and 1 patient with GC. In an interim analysis of an ongoing expansion cohort of patients with non-squamous NSCLC and with CEACAM5 expression in ≥ 50% of tumor cells, 25% overall response rate (ORR) (8/32 evaluable patients) and 37.5% (12 patients) stable disease were observed. In parallel to FIH trial, several preclinical studies were performed to support the clinical development of SAR408701 in NSCLC, CRC and GC. A single mouse trial (SMT) was carried out on a panel of 28 patent-derived xenografts (PDX) covering the top 3 indications. The SMT format employs a single mouse per PDX model and treatment arm and uses RECIST criteria as readout. Results showed an efficacy profile in the preclinical trial close to that obtained in clinic with an ORR of 10% in CRC, of 50% in lung cancers and of 37.5% in GC. The efficacy of SAR408701 is correlated with CEACAM5 expression in lung and gastric indications. To further assess the potential of SAR408701 in NSCLC, preclinical investigations have been done to determine if an ADC-DM4 could be beneficially combined with immune checkpoint inhibitors (ICIs). The capacity of DM4-treated tumor cells to immunize immune competent mice to the tumor was evaluated, indicating that DM4 can induce immunogenic cell death. This result supports the development of SAR408701 in combination with ICIs in NSCLC. The combination of SAR408701 with 4 different standard of care (SoC) therapies were tested in 2 CRC PDX models, one sensitive and one resistant to SAR408701 alone. Combinations of SAR408701 were evaluated with either FOLFOX regimen, FOLFIRI regimen, TAS-102 or cetuximab. All combinations resulted in significantly better antitumor activity than single agent arms in both resistant and sensitive PDXs without an increase in toxicity and showed a therapeutic synergy. These results suggest that SAR408701 c