Oncolytic HSV-1 Encoding IL-12 and Anti-PD-1 Reprograms CNS Immunity: Open-Label Study of MVR-C5252 for Safety, Tolerability, and Efficacy (PuMP)

Introduction/Rationale: To overcome immunosuppression in glioblastoma (GBM), we evaluated MVR-C5252, an HSV-1 expressing interleukin-12 (IL-12) and an anti–PD-1 antibody fragment, coupling oncolysis with Th1 polarization and checkpoint blockade.

Methods: Stage 1 of PuMP (NCT06126744) established safety of a single convection-enhanced intratumoral infusion of MVR-C5252 in adults with recurrent IDH-wildtype GBM (5×10⁶ or 1×10⁸ PFU; n=6). A reservoir in the contralateral ventricle collected CSF at baseline, 1 h, and 28 d post-infusion. Pre- and post-treatment tumors were analyzed by Xenium spatial transcriptomics and CODEX proteomics, whole-genome sequencing (WGS) of tumor and CSF quantified ctDNA and viral genome. LC–MS metabolomics targeted IFN-γ–linked tryptophan/kynurenine and arginine/NO pathways. Stage 2, now ongoing, uses an implanted SynchroMed pump for immune priming and boosting via repeat dosing.

Results: Adverse events were grade 1–2 only with no viral shedding in urine or saliva by PCR. At 28 d, CSF immune cells exhibited sustained IFN-γ–driven transcriptional programs. Dendritic cells upregulated cross-presentation genes (TAP1, TAPBP, CD83). CD8⁺ T cells expressed increased IFNG, GZMB, and PRF1 with minimal PDCD1 or LAG3 reinduction. NK cells showed transient suppression at 1 h followed by recovery of cytotoxic and IFN-γ–responsive programs (GZMB, PRF1, STAT1), indicating reactivation of antigen-presenting and effector circuits.

Conclusion: Analyses will relate immune and metabolic remodeling to viral kinetics and ctDNA dynamics. Single-cell and spatial profiling (CODEX, Xenium), LC–MS/MS metabolomics, and CSF–tumor–blood analyses to define immune–metabolic interactions. These findings establish a mechanistic model of localized IL-12/anti–PD-1 virotherapy converting an immunologically quiescent GBM microenvironment into a Th1-polarized, cytotoxic state. Stage 3 will refine dosing and schedule, and Stage 4 will expand at the Phase 2 dose to evaluate efficacy.