CD16a x MSLN

The tumor-shed antigen CA125 has recently been found to bind certain monoclonal antibodies (mAbs) and suppress immune-effector mediated killing through perturbation of the Fc domain with CD16a and CD32a Fc-γ activating receptors on immune-effector cells. Amatuximab is a mAb targeting mesothelin whose mechanism of action utilizes in part antibody-dependent cellular cytotoxicity (ADCC). It is being tested for its therapeutic activity in patients with mesothelioma in combination with first line standard-of-care. To determine if CA125 has immunosuppressive effects on amatuximab ADCC and associated clinical outcomes, post hoc subgroup analysis of patients from a Phase 2 study with primary diagnosed stage III/IV unresectable mesothelioma treated with amatuximab plus cisplatin and pemetrexed were conducted. Analysis found patients with baseline CA125 levels no greater than 57 U/m (∼3X the upper limit of normal) had a 2 month improvement in progression free survival (HR = 0.43, p = 0.0062) and a 7 month improvement in overall survival (HR = 0.40, p = 0.0022) as compared to those with CA125 above 57 U/mL. In vitro studies found that CA125 was able to bind amatuximab and perturb ADCC activity via decreased Fc-γ-receptor engagement. These data suggest that clinical trial designs of antibody-based drugs in cancers producing CA125, including mesothelioma, should consider stratifying patients on baseline CA125 levels for mAbs that are experimentally determined to be bound by CA125.

Although natural killer (NK) cells are endowed with intrinsic cytotoxicity, their therapeutic application often faces limitations because of their lack of tumor-specific targeting ability and limited ability to infiltrate solid tumors. To overcome these limitations, we developed anti-mesothelin (MSLN) uCAR-like NK cells, which are designed to enhance both the targeting specificity and tumor infiltration capacity, thereby improving the antitumor efficacy of NK cell-based therapies. We constructed, purified, and validated a tetravalent bispecific cell engager (MSLN×CD16A) via the SpyTag/SpyCatcher system. Cytokine-induced memory-like NK cells, induced by IL-12, IL-15, and IL-18, were precomplexed with MSLN×CD16A to generate anti-MSLN CAR-like NK cells. To further enhance tumor penetration, the tumor-penetrating peptide uCendR was integrated into the system to construct anti-MSLN uCAR-like NK cells. In vitro, anti-MSLN CAR-like NK cells demonstrated selective cytotoxicity against MSLN-positive tumor cells through stable binding with MSLN×CD16A while sparing MSLN-negative cells. In xenograft models bearing MSLN-positive tumors, anti-MSLN CAR-like NK cells exhibited significant antitumor activity, with favorable tolerability and no significant body weight loss or toxicity. Notably, anti-MSLN uCAR-like NK cells, which integrate a tumor-penetrating peptide, displayed enhanced intratumor penetration and superior therapeutic efficacy. Overall, this study establishes a modular, nongenetically engineered uCAR-like NK platform that couples targeted recognition with enhanced tissue access. These findings highlight the potential of anti-MSLN CAR-like NK cells, particularly uCAR-like NK cells with enhanced tumor penetration, as promising therapeutic strategies for MSLN-positive solid tumors and lay the foundation for future clinical applications.