CD3-CSPG4 bispecific T cell engager: A novel platform for malignant melanoma therapy

Malignant melanoma (MM) is a highly aggressive malignancy that readily metastasizes to lymph nodes and distant sites through hematogenous spread, leading to poor clinical outcomes. Therefore, there is an urgent need to develop novel therapeutic strategies. Chondroitin sulfate proteoglycan 4 (CSPG4) is one of the most frequently overexpressed proteins on malignant melanoma cells, whereas it is only expressed at very low levels in normal tissues. In this study, a novel bispecific T‑cell engager, CD3‑CSPG4/BiTE, was constructed by linking single‑chain antibodies directed against CSPG4 and CD3. In vitro assays assessed its simultaneous and specific binding to CSPG4 ⁺ melanoma cells and T cells, its capacity to drive T-cell proliferation and activation, and its ability to redirect T-cell cytotoxicity toward CSPG4 ⁺ targets. Additionally, in NOD/SCID mice bearing established human melanoma xenografts, the antitumor efficacy and systemic toxicity of the molecule were evaluated. CD3-CSPG4/BiTE was successfully generated and was shown to simultaneously bind CSPG4 ⁺ melanoma cells and T cells. Flow-cytometric analysis revealed that, compared with control constructs, CD3-CSPG4/BiTE markedly enhanced T-cell proliferation and activation (as evidenced by up-regulated CD25 and CD69) and effectively redirected T-cell-mediated lysis of CSPG4 ⁺ targets in vitro. In NOD/SCID mice bearing human melanoma xenografts, the BiTE significantly suppressed tumor growth without eliciting detectable toxicity in major organs. In summary, this study successfully developed a novel bispecific T-cell engager, CD3-CSPG4/BiTE, and demonstrated its potent antitumor activity against malignant melanoma both in vitro and in vivo. These findings provide a preclinical foundation for the clinical translation and further optimization of BiTE-based immunotherapy for melanoma.