CD7-targeting pro-apoptotic extracellular vesicles: A novel approach for T-cell haematological malignancy therapy.

T-cell haematological malignancies progress rapidly and have a high mortality rate and effective treatments are still lacking. Here, we developed a drug delivery system utilizing 293T cell-derived extracellular vesicles (EVs) modified with an anti-CD7 single-chain variable fragment (αCD7/EVs). Given the challenges of chemotherapy resistance in patients with T-cell malignancy, we selected cytochrome C (CytC) and Bcl2 siRNA (siBcl2) as therapeutic agents and loaded them into αCD7/EVs (αCD7/EVs/CytC/siBcl2). We found that αCD7/EVs efficiently targeted and were internalized by human T-ALL Molt-4 cells. In addition, the interaction between αCD7 and CD7 switched the EV entry pathway in Molt-4 cells from macropinocytosis-dependent endocytosis to clathrin-mediated endocytosis, thereby reducing EV-lysosome colocalization, ultimately improving CytC delivery efficiency and increasing the cytotoxicity of nascent EVs from EV-treated Molt-4 cells. Notably, αCD7/EVs/CytC/siBcl2 demonstrated similar efficacy against both Molt-4 and chemotherapy-resistant Molt-4 cells (CR-Molt-4). Furthermore, αCD7/EVs/CytC/siBcl2 exhibited high safety, low immunogenicity and minimal impact on human T cells. Therefore, αCD7/EVs/CytC/siBcl2 are promising therapeutic approaches for treating CD7 T-cell malignancies.