Development of a bispecific antibody that inhibits EGFR and B7H3 in NSCLC

The overexpression of epidermal growth factor receptor (EGFR) and B7 homolog 3 protein (B7H3) are known to drive the growth and proliferation of non-small cell lung cancer (NSCLC), thereby positioning them as promising therapeutic targets. This study aimed to explore the co-expression of B7H3 and EGFR in NSCLC, and thereafter develop a bispecific antibody (bsAb) targeting B7H3 and EGFR. We evaluated the co-expression of B7H3 and EGFR in 222 advanced NSCLC tissue samples, and investigated its association with the microenvironment, as well as with patient survival. Four bsAbs were designed with varying affinities to B7H3 and EGFR, and their pharmacological activities including competitive binding with EGFR, EGFR signaling blockade, and antibody-dependent cell-mediated cytotoxicity (ADCC) were evaluated. Based on the results, FH-EB02 was selected to assess the tumor growth inhibition effects with two cell line-derived xenograft (CDX) mouse models and four patient-derived xenograft (PDX) mouse models. B7H3 and EGFR were co-expressed in 62.6% of advanced NSCLC and were negatively correlated with the infiltration of CD8+ T cells and positively associated with Foxp3+ Tregs. Besides, patients with positive co-expression had shorter PFS (median 7.9 vs. 14.2 months, HR = 0.50) and OS (median 17.2 vs. 37.4 months, HR = 0.47) compared to those with negative co-expression. Furthermore, by combining two anti-EGFR arms with three anti-B7H3 arms, four bsAbs were designed. The bsAbs exhibited stronger tumor cell binding capacity, more effectively EGFR signaling blockade, and more potent ADCC effects compared to cetuximab in B7H3 and EGFR double-positive cells. Among them, FH-EB02 was selected for further investigation duo to the highest binding capacity. In vivo, FH-EB02 treatment significantly inhibited tumor growth in CDX and two PDX mouse models bearing tumors coexpressing EGFR and B7H3, but showed no efficacy in PDX models expressing EGFR alone. In addition, toxicology studies in cynomolgus monkeys showed that FH-EB02 was well tolerated. Co-expression of EGFR and B7H3 is highly prevalent in NSCLC and correlates with poorer survival. Meanwhile, FH-EB02 is a promising B7H3/EGFR bsAb with significant anti-tumor activity and tolerable toxicities, which warrants further clinical investigation.