Suppression of Tumor or Host Intrinsic CMTM6 Drives Antitumor Cytotoxicity in a PD-L1-Independent Manner.

CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6) is known to be a regulator of membranal programmed death ligand 1 (PD-L1) stability and a factor associated with malignancy progression, but the effects and mechanisms of CMTM6 on tumor growth, as well as its potential as a target for therapy, are still largely unknown. Here, we show that CMTM6 expression increased with tumor progression in both patients and mice. Ablation of CMTM6 significantly reduced human and murine tumor growth in a manner dependent on T-cell immunity. Tumor CMTM6 suppression broke resistance to immune-checkpoint inhibitors and remodeled the tumor immune microenvironment, as specific antitumor cytotoxicity was enhanced and contributed primarily to tumor inhibition. Without the PD-1/PD-L1 axis, CMTM6 suppression still significantly dampened tumor growth dependent on cytotoxic cells. Furthermore, we identified that CMTM6 was widely expressed on immune cells. T-cell CMTM6 levels increased with sustained immune activation and intratumoral immune exhaustion and affected T cell-intrinsic PD-L1 levels. Host CMTM6 knockout significantly restrained tumor growth in a manner dependent on CD8+ T cells and not entirely dependent on PD-L1. Thus, we developed and evaluated the antitumor efficacy of CMTM6-targeting adeno-associated virus (AAV), which effectively mobilized antitumor immunity and could be combined with various antitumor drugs. Our findings reveal that both tumor and host CMTM6 are involved in antitumor immunity with or without the PD-1/PD-L1 axis and that gene therapy targeting CMTM6 is a promising strategy for cancer immunotherapy.

Development of a bridging ELISA for detection of antibodies against ZV0203 in cynomolgus monkey serum.

Immunogenicity has been a major concern in the safety evaluation of therapeutic proteins. The assessment of the unwanted immunogenicity of the therapeutic proteins performed in animals prior to clinical trials has been a regulatory requirement. In preclinical studies of therapeutic proteins, cynomolgus monkeys are usually the most relevant animal species. ZV0203, a recombinant humanized anti-human epidermal growth factor receptor 2 monoclonal antibody covalently bound to a cytotoxic drug (Duo-5), possesses a novel format of antibody drug conjugates. In this study, we reported the development, validation, and application of a bridging enzyme-linked immunosorbent assay for the detection of antibodies against ZV0203 in cynomolgus monkey serum. Drug interference at low positive control (18.0 ng/mL) and high positive control (130 ng/mL) of anti-ZV0203 antibodies was not observed when ZV0203 concentration is below 1.74 µg/mL and 1.49 µg/mL, respectively. In addition, no interference was found from mouse IgG1, but interference was observed with human IgG1. No effect of hemolysis was found on the analysis results of the testing samples present in 100% pooled rabbit serum containing 2% (V/V) erythrocyte hemolysates. Besides, spiked anti-ZV0203 antibody in rabbit serum was stable after 5 freeze/thaw cycles. The results showed that the method is suitable for the detection of anti-ZV0203 antibodies in cynomolgus monkey serum. The assay was also successfully applied in the repeated dose study of ZV0203.

CoVac501, a self-adjuvanting peptide vaccine conjugated with TLR7 agonists, against SARS-CoV-2 induces protective immunity.

Safe, effective, and economical vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to achieve adequate herd immunity and end the pandemic. We constructed a novel SARS-CoV-2 vaccine, CoVac501, which is a self-adjuvanting peptide vaccine conjugated with Toll-like receptor 7 (TLR7) agonists. The vaccine contains immunodominant peptides screened from the receptor-binding domain (RBD) and is fully chemically synthesized. It has been formulated in an optimized nanoemulsion formulation and is stable at 40 °C for 1 month. In non-human primates (NHPs), CoVac501 elicited high and persistent titers of protective neutralizing antibodies against multiple RBD mutations, SARS-CoV-2 original strain, and variants (B.1.1.7 and B.1.617.2). Specific peptides booster immunization against the B.1.351 variant has also been shown to be effective in improving protection against B.1.351. Meanwhile, CoVac501 elicited the increase of memory T cells, antigen-specific CD8+ T-cell responses, and Th1-biased CD4+ T-cell immune responses in NHPs. Notably, at an extremely high SARS-CoV-2 challenge dose of 1 × 107 TCID50, CoVac501 provided near-complete protection for the upper and lower respiratory tracts of cynomolgus macaques.