Supplementary Figure 1 shows more details on the mode of action and design of the used antibodies. Supplementary Figure 2 displays additional APC activation data of the human and murine FAP-CD40 molecules. Supplementary Figure 3 shows additional data for FRC in vitro assays and the OVA vaccination study. Supplementary Figure 4 shows additional data on the in vivo study comparing FAP-huCD40 and SGN40 moIgG1. Supplementary Figure 5 displays additional data on the in vivo comparison of selicrelumab and FAP-huCD40. Supplementary Figure 6 shows the data of a FAP-huCD40 dose escalation study in cynomolgus monkeys.
ARTICLE ABSTRACTCD40 agonists hold great promise for cancer immunotherapy (CIT) as they enhance dendritic cell (DC) activation and concomitant tumor-specific T-cell priming. However, the broad expression of CD40 accounts for sink and side effects, hampering the efficacy of anti-CD40 antibodies. We hypothesized that these limitations can be overcome by selectively targeting CD40 agonism to the tumor. Therefore, we developed a bispecific FAP-CD40 antibody, which induces CD40 stimulation solely in presence of fibroblast activation protein α (FAP), a protease specifically expressed in the tumor stroma.
FAP-CD40's in vitro activity and FAP specificity were validated by antigen-presenting cell (APC) activation and T-cell priming assays. In addition, FAP-CD40 was tested in subcutaneous MC38-FAP and KPC-4662-huCEA murine tumor models.
FAP-CD40 triggered a potent, strictly FAP-dependent CD40 stimulation in vitro. In vivo, FAP-CD40 strongly enhanced T-cell inflammation and growth inhibition of KPC-4662-huCEA tumors. Unlike nontargeted CD40 agonists, FAP-CD40 mediated complete regression of MC38-FAP tumors, entailing long-term protection. A high dose of FAP-CD40 was indispensable for these effects. While nontargeted CD40 agonists induced substantial side effects, highly dosed FAP-CD40 was well tolerated. FAP-CD40 preferentially accumulated in the tumor, inducing predominantly intratumoral immune activation, whereas nontargeted CD40 agonists displayed strong systemic but limited intratumoral effects.
FAP-CD40 abrogates the systemic toxicity associated with nontargeted CD40 agonists. This enables administration of high doses, essential for overcoming CD40 sink effects and inducing antitumor immunity. Consequently, FAP-targeted CD40 agonism represents a promising strategy to exploit the full potential of CD40 signaling for CIT.