Fusion peptide is superior to co-expressing subunits for arming oncolytic herpes virus with interleukin 12

Abstract

Background G47∆ is a triple-mutated oncolytic herpes simplex virus type 1 (HSV-1) recently approved as a new drug for malignant glioma in Japan. As the next-generation, we develop armed oncolytic HSV-1 using G47∆ as the backbone. Because oncolytic HSV-1 elicits specific antitumor immunity, interleukin 12 (IL-12) can function as an effective payload to enhance the efficacy. Methods We evaluate the optimal methods for expressing IL-12 as a payload for G47∆-based oncolytic HSV-1. Two new armed viruses are generated for evaluation by employing different methods to express IL-12: T-mfIL12 expresses murine IL-12 as a fusion peptide, with the genes of two subunits (p35 and p40) linked by bovine elastin motifs, and T-mIL12-IRES co-expresses the subunits, with the two genes separated by an internal ribosome entry site (IRES) sequence. Results T-mfIL12 is significantly more efficient in producing IL-12 than T-mIL12-IRES in all cell lines tested, whereas the expression methods do not affect the replication capabilities and cytopathic effects. In two syngeneic mouse subcutaneous tumor models of Neuro2a and TRAMP-C2, T-mfIL12 exhibits a significantly higher efficacy than T-mIL12-IRES when inoculated intratumorally. Furthermore, T-mfIL12 shows a significantly higher intratumoral expression of functional IL-12, causing stronger stimulation of specific antitumor immune responses than T-mIL12-IRES. Conclusions The results implicate that a fusion-type expression of IL-12 is a method superior to co-expression of separate subunits, due to higher production of functional IL-12 molecules. This study led to the creation of triple-mutated oncolytic HSV-1 armed with human IL-12 currently used in phase 1/2 trial for malignant melanoma.

Cytokine-armed oncolytic herpes simplex viruses: a game-changer in cancer immunotherapy?

“…In addition to the aforementioned oHSV-IL-12s, several other oHSVs encoding IL-12 and often other transgenes, such as VT1092M (+anti-PD-1), 64 T2850 (+anti-PD-1), 65 T-mfIL-12, 66 and vHsv-IL-12, 67 were developed and tested in various cancer models. IL-12, alongside GM-CSF, is a leading cytokine in the context of engineered oHSV therapy for cancer, consistently demonstrating safety, superior anticancer efficacy, and beneficial antitumor immunity compared with non-IL-12-expressing oHSVs.…”