Recombinant human GM-CSF oncolytic herpes simplex virus type 2 (Binhui Bio)

Prostate cancer (PCa) is a prevalent malignancy with limited treatment options for advanced stages. Oncolytic virotherapy represents a promising immunotherapeutic approach, but its efficacy and underlying mechanisms in PCa, particularly concerning immune checkpoint regulation, remain unclear.

The antitumor effects of the oncolytic virus oncolytic herpes simplex virus type 2 (OH2) were evaluated in PCa cell lines and mouse models. Transcriptome sequencing, western blot, chromatin immunoprecipitation-sequencing-quantitative PCR, and flow cytometry were employed to investigate the mechanism of programmed death 1 ligand 1 (PD-L1) regulation. A targeted delivery system, reactive oxygen species (ROS)-responsive aptamer-conjugated anti-prostate-specific membrane antigen (PSMA) extracellular vesicles (RRA-AP-EVs), was engineered from anti-PSMA single chain variable fragment (scFv)-modified extracellular vesicles and an ROS-responsive PD-L1 blocking aptamer. OH2 was loaded via membrane extrusion, and the resulting OH2@RRA-AP-EVs were tested for targeting and therapeutic efficacy following intravenous administration.

OH2 effectively killed PCa cells but simultaneously activated the IKK/I-κBα/p65 pathway, leading to PD-L1 upregulation and adaptive immune resistance. While combining OH2 with anti-PD-L1 improved outcomes, clinical translation was hindered by delivery challenges. The novel OH2@RRA-AP-EVs system demonstrated precise tumor targeting and ROS-triggered local PD-L1 blockade. Intravenous injection of OH2@RRA-AP-EVs showed superior tumor control (inhibiting tumor growth by 70% vs free OH2) and enhanced CD8+T cell infiltration and function compared with free OH2 (greater than twofold increase in intratumoral CD8+T cell infiltration along with over twofold upregulation of key effector molecules).

This study identifies a mechanism of OH2-induced PD-L1 expression in PCa and provides a versatile, targeted delivery platform that enables effective intravenous viro-immunotherapy, overcoming key translational barriers.

Oncolytic virus therapy is a novel and promising approach in tumor immunotherapy. We have developed the oncolytic virus OH2 and completed its preclinical studies. This oncolytic virus is currently undergoing clinical trials in China (NMPA, 2018L02743) and the United States (FDA IND 27137) targeting various solid tumors. One of the main mechanisms by which the oncolytic virus exerts its antitumor effect is through the direct killing of tumor cells. In our previous studies, we found that the structural protein VP5 of oncolytic virus OH2 can induce apoptosis in A549 cells via the TP53I3 molecule. This study further investigates the solid tumor cell lines involved in the clinical trials of oncolytic virus OH2. We found that VP5 protein exhibits different functions depending on the tumor cell type. Stable expression of VP5 protein enhanced the cytotoxicity of UV-OH2 against BGC823, LoVo, and CT26 cells, while inhibiting its cytotoxicity against 4T1 and HeLa cells. To explore the differences in the cytotoxicity induced by VP5 protein in different tumor cells, we performed transcriptome sequencing on 4T1-VP5 cells and OH2-stimulated 4T1-VP5 cells, comparing them with 4T1 cells and OH2-stimulated 4T1 cells, respectively. We also compared the transcriptome sequencing results with those of A549 cells from previous studies. Through this, we identified nectin-3 as a differentially expressed gene associated with tumor cell killing induced by VP5 protein. Further studies on nectin-3 revealed that the structural protein VP5 of oncolytic virus OH2 regulates the expression of nectin-3 in tumor cells, thereby promoting or inhibiting tumor cell apoptosis.