Co-blocking TIGIT and PVRIG Using a Novel Bispecific Antibody Enhances Antitumor Immunity.

T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) and poliovirus receptor-related immunoglobulin domain (PVRIG) are immune checkpoints co-expressed on activated T and NK cells, contributing to tumor immune evasion. Simultaneous blockade of these pathways may enhance therapeutic efficacy, positioning them as promising dual targets for cancer immunotherapy. This study aimed to develop a bispecific antibody (BsAb) to co-target TIGIT and PVRIG. Expression of TIGIT and PVRIG was assessed on tumor-infiltrating lymphocytes from patients with various cancers, including non-small cell lung cancer (n = 63) and colorectal cancer (n = 26). The BsAb was engineered by fusing anti-PVRIG nanobodies to the N terminus of anti-TIGIT antibodies. Functional characterization of the BsAb was performed in vitro and in vivo, including assessments of T- and NK-cell activation and cytotoxicity. Pharmacokinetics and safety profiles were evaluated in cynomolgus monkeys. Statistical analyses were conducted using the Student t test. The results showed that the BsAb effectively blocked TIGIT and PVRIG from binding their respective ligands, CD155 and CD112, leading to significant increases in T-cell activation (2.8-fold; P < 0.05) and NK-cell cytotoxicity (1.8-fold; P < 0.05). In vivo, the BsAb demonstrated potent antitumor activity, both as a monotherapy and in combination with anti-PD-1 or anti-PD-L1, in humanized peripheral blood mononuclear cell-reconstituted and transgenic mouse models. Pharmacokinetic studies in cynomolgus monkeys revealed a favorable profile, with no dose-limiting toxicities observed after four repeated doses of 200 mg/kg. These findings provide compelling preclinical evidence for the therapeutic potential of targeting the TIGIT-PVRIG axis with a BsAb. This approach shows promise for enhancing antitumor immunity and warrants further investigation in clinical trials.