Sum and Rapp et al. developed a bispecific FAP-targeted molecule containing two domains of agonistic CD40 antibody (FAP-CD40) that is only triggered upon binding to FAP-expressing cancer-associated fibroblasts and fibroblastic reticular cells in the tumor or lymph node (LN), to prevent systemic toxicity. In mice, FAP-CD40 activated DCs in the tumor and LN, and increased tumoral infiltration and activation of T cells, even in a T cell-excluded model. This induced tumor remission, even upon rechallenge, after a single dose. A high dose was essential for efficacy, which was well tolerated in mice and in dose-escalating studies in cynomolgus monkeys.
Contributed by Maartje Wouters
Purpose: CD40 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.
Experimental design: 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 (s.c.) MC38-FAP and KPC-4662-huCEA murine tumor models.
Results: 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 non-targeted 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 non-targeted 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 non-targeted CD40 agonists displayed strong systemic but limited intratumoral effects.
Conclusions: FAP-CD40 abrogates the systemic toxicity associated with non-targeted CD40 agonists. This enables administration of high doses, essential for overcoming CD40 sink effects and inducing anti-tumor immunity. Consequently, FAP-targeted CD40 agonism represents a promising strategy to exploit the full potential of CD40 signaling for CIT.
Author Info: (1) Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (2) Roche Innovation Center Munich (RICM), Roche Pharmaceutical Research and
Author Info: (1) Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (2) Roche Innovation Center Munich (RICM), Roche Pharmaceutical Research and Early Development (pRED). (3) Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (4) Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (5) Roche Innovation Center Munich (RICM), Roche Pharmaceutical Research and Early Development (pRED). (6) PS, Pathology, Roche Innovation Center Zurich. (7) Pharmacology, Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (8) Pharmacology, Roche Innovation Center Zürich. (9) Pharmacology, Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (10) Pharmacology, Roche Innovation Center Zürich. (11) Roche Innovation Center Zurich, Roche Pharma  Research and Early Development, F.Hoffman-LaRoche LTD. (12) Pharmaceutical Sciences, Roche Innovation Center Basel (RICB), Roche Pharmaceutical Research and Early Development (pRED). (13) Pharma Research and Early Development, Roche Diagnostics GmbH. (14) Pharmacology, Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (15) Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (16) Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (17) Pharma Reasearch and Early Development, Roche Innovation Center Zurich. (18) Large Molecule Research, Roche Pharmaceutical Research & Early Development, Roche Innovation Center Zurich, Wagistrasse 10, CH-8952 Schlieren. (19) Molecular Biology, Roche Innovation Center Zurich (RICZ), Roche Pharmaceutical Research and Early Development (pRED). (20) Division of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), University of Navarra and Instituto de Investigacion Sanitaria de Navarra (IdISNA). (21) Pharmaceutical Sciences, Roche Innovation Center Basel (RICB), Roche Pharmaceutical Research and Early Development (pRED). (22) Roche Innovation Center Munich (RICM), Roche Pharmaceutical Research and Early Development (pRED). (23) Roche Innovation Center Basel (RICB), Roche Pharmaceutical Research and Early Development (pRED). (24) Roche Innovation Center Munich (RICM), Roche Pharmaceutical Research and Early Development (pRED). (25) Department of Oncology, University of Lausanne. (26) Roche Innovation Center Zurich, Roche Pharmaceutical Research and Early Development christine.trumpfheller@roche.com. (27) Roche Pharmaceutical Research and Early Development, Roche Innovation Center Zurich.
