A novel oncolytic HSV co-expressing IL-12 and anti-PD-1 for glioblastoma

Glioblastoma (GBM), the most common primary malignant brain tumor, is an invariably lethal cancer under the current standard of care.1Nguyen H.M. Guz-Montgomery K. Lowe D.B. Saha D. Pathogenetic Features and Current Management of Glioblastoma.Cancers. 2021; 13856https://www.ncbi.nlm.nih.gov/pubmed/33670551Crossref Scopus (28) Google Scholar Even systemic immune checkpoint blockade (ICB) anti-programmed death 1 (PD-1) immunotherapy, although approved in many other cancers, has failed in clinical trials for GBM.1Nguyen H.M. Guz-Montgomery K. Lowe D.B. Saha D. Pathogenetic Features and Current Management of Glioblastoma.Cancers. 2021; 13856https://www.ncbi.nlm.nih.gov/pubmed/33670551Crossref Scopus (28) Google Scholar The treatment failure is likely due to the immunosuppressive nature of the GBM microenvironment, referred to as "immunologically cold,"1Nguyen H.M. Guz-Montgomery K. Lowe D.B. Saha D. Pathogenetic Features and Current Management of Glioblastoma.Cancers. 2021; 13856https://www.ncbi.nlm.nih.gov/pubmed/33670551Crossref Scopus (28) Google Scholar which can be reversed by intratumoral administration of oncolytic herpes simplex virus (oHSV),2Saha D. Martuza R.L. Rabkin S.D. Macrophage Polarization Contributes to Glioblastoma Eradication by Combination Immunovirotherapy and Immune Checkpoint Blockade.Cancer Cell. 2017; 32: 253-267.e5https://www.ncbi.nlm.nih.gov/pubmed/28810147Abstract Full Text Full Text PDF PubMed Scopus (395) Google Scholar,3Nguyen H.M. Bommareddy P.K. Silk A.W. Saha D. Optimal timing of PD-1 blockade in combination with oncolytic virus therapy.Semin. Cancer Biol. 2022; 86: 971-980https://www.ncbi.nlm.nih.gov/pubmed/34033895Crossref PubMed Scopus (13) Google Scholar a promising anticancer approach approved in Japan for recurrent GBM. Intralesional delivery of ICB and interleukin-12 (IL-12) can be effective against cancer preclinically, but both are toxic when given systemically.4Melero I. Castanon E. Alvarez M. Champiat S. Marabelle A. Intratumoural administration and tumour tissue targeting of cancer immunotherapies.Nat. Rev. Clin. Oncol. 2021; 18: 558-576https://www.ncbi.nlm.nih.gov/pubmed/34006998Crossref PubMed Scopus (199) Google Scholar Considering oHSV's capacity for foreign transgene expression, several oHSVs have been engineered for local co-expression of IL-12 and anti-PD-1. T3855, expressing IL-12 plus anti-PD-1, has shown promise in preclinical studies but has not been evaluated in GBM.5Yan R. Zhou X. Chen X. Liu X. Tang Y. Ma J. Wang L. Liu Z. Zhan B. Chen H. et al.Enhancement of oncolytic activity of oHSV expressing IL-12 and anti PD-1 antibody by concurrent administration of exosomes carrying CTLA-4 miRNA.Immunotherapy. 2019; 0535248Google Scholar STI-1386 (Seprehvec), expressing IL-12, anti-PD-1 single chain fragment variant (scFv), and a transforming growth factor β receptor 2 decoy, is undergoing clinical trial, albeit not for GBM (ClinicalTrials.gov: NCT05361954). In this study, Wang et al. developed a similar oHSV co-expressing human IL-12 and anti-PD-1 antigen-binding fragment (C5252) and evaluated its oncolytic activity in vitro and safety and antitumor efficacy in vivo in GBM models.6Wang L. Zhou X. Chen X. Liu Y. Huang Y. Cheng Y. Ren P. Zhao J. Zhou G.G. Enhanced Therapeutic Efficacy for Glioblastoma Immunotherapy with a New Generation Oncolytic Herpes Simplex Virus Armed with Anti-PD-1 Antibody and IL-12.Mol. Ther. Oncol. 2024; 32200799https://www.sciencedirect.com/science/article/pii/S2950329924000419Google Scholar The C5252 virus efficiently produces IL-12 and anti-PD-1 upon infection of Vero cells. Compared to control R3616 (an oHSV with no transgene expression and lacking both copies of the γ34.5 genes), C5252 (lacking both copies of the γ34.5 genes and having a deletion of the internal repeat region, which could further attenuate the virus) shows reduced viral yields but higher cytotoxic activity in human GBM cells in vitro. It is not clear how lower replication correlates with increased cytotoxicity; one possible explanation could be that human IL-12, released from C5252 infection in the culture supernatant, may have induced cytotoxicity. C5252-induced oncolysis was associated with a significant increase in caspase-3/7 activity (vs. R3616 or wild-type HSV) via downregulation of ciliary neurotrophic factor receptor α(CNTFRα), a receptor for CNTF required for survival of neuronal cells.6Wang L. Zhou X. Chen X. Liu Y. Huang Y. Cheng Y. Ren P. Zhao J. Zhou G.G. Enhanced Therapeutic Efficacy for Glioblastoma Immunotherapy with a New Generation Oncolytic Herpes Simplex Virus Armed with Anti-PD-1 Antibody and IL-12.Mol. Ther. Oncol. 2024; 32200799https://www.sciencedirect.com/science/article/pii/S2950329924000419Google Scholar The safety of C5252 was confirmed in BALB/c nude mice. Mice injected intracranially with C5252 survived a significantly higher dose than wild-type HSV-1 (F strain) mice and exhibited no physical or behavioral abnormalities. Furthermore, C5252 did not establish latency, and its reactivation was reduced. C5252's median lethal dose (>105 plaque-forming units) and inability to establish latency suggest that it is safe for GBM treatment. These safety characteristics likely stem from the deletion of the neurovirulence gene γ34.5 and the internal repeat. In GBM xenograft models (both subcutaneous and orthotopic), intratumoral injections of C5252 demonstrated significantly better control of the tumor burden than R3616, which is somewhat surprising since both human IL-12 and anti-human PD-1 are not active in mice. This transgene inactivity and the lack of an intact immune system in xenograft models means that the immunotherapeutic potential of C5252 cannot be assessed preclinically. To address this, a murine version of C5252 (C8282) expressing murine IL-12 and anti-murine PD-1 was constructed and tested in immunocompetent syngeneic GBM models in mice. In the orthotopic CT-2A-GFP-Luc model, intratumoral treatment with C8282 significantly extended median survival, with 25% long-term survivors, which is promising. However, the study lacked important control groups, such as unarmed oHSV, to distinguish the impact of transgene expression from oncolysis, and oHSVs expressing single transgenes, to define the roles of IL-12 or anti-PD-1 in treatment efficacy. In a somewhat artificial subcutaneous CT-2A-GFP-Luc model, C8282 treatment reduced the tumor burden significantly compared to its parental unarmed C1212, indicating a role of IL-12 and/or anti-PD-1, and increased intratumoral IFN-γ and tumor necrosis factor alpha. IL-12 and anti-PD-1 expression likely induced IFN-γ and recruited immune cells into the tumor, which may have contributed to antitumor efficacy (as depicted in Figure 1). However, the authors did not measure tumoral transgene expression or evaluate immune cell infiltration. In conclusion, the authors have constructed new armed oHSVs (human C5252 and murine C8282) and demonstrated their safety and efficacy. Given the multifaceted immune mechanisms of IL-12 and anti-PD-1 in enhancing antitumor immunity (Figure 1), further research evaluating the effects of C8282 on the tumor immune microenvironment and the requirement for specific immune cells is necessary to understand the antitumor mechanisms of action of C5252/C8282. K.A. prepared the figure. X.F. commented on this commentary. D.S. conceived and wrote the commentary. The authors declare no competing interests.