A surgical window of opportunity trial evaluating the effect of the PCSK9 inhibitor evolocumab on tumoral MHC-I expression and CD8<sup>+</sup> infiltration in glioma.

Abstract

Many cancers evade immunosurveillance by downregulating surface major histocompatibility class (MHC)-I. Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes MHC-I degradation and is elevated in glioma. Evolocumab is a clinically approved PCSK9 inhibitor which restores MHC-I expression in pre-clinical cancer models. However, monoclonal antibodies have limited blood brain/tumor barrier penetrance (BBB/BTB). We conducted a window-of-opportunity trial, evaluating evolocumab's BBB/BTB penetrance and biological effect (PesKE; NCT04937413). Patients with newly diagnosed or recurrent glioma undergoing a clinically indicated biopsy or resection were enrolled (n = 32, M: 16, F: 16; control average age: 51.85, evolocumab: 53). Intervention participants (n = 6) received a single subcutaneous evolocumab dose pre-procedure, of which 4 provided research tissue. No significant adverse events were observed. Evolocumab was detected in all analyzed intervention tissue, with an average tumor: blood ratio of 0.0222 (SD ± 0.0190), akin to other monoclonals. Evolocumab quantitation was 4.44× greater in contrast-enhancing (mean 0.0068 fmol/mcg (SD ± 0.001)) vs non-contrast enhancing cases (mean 0.0015 fmol/mcg (SD ± 0.0004)). Proteomic analysis found positive trends between evolocumab and MHC-I subtypes (HLA-A-C, E-G), with a significant positive correlation with HLA-H (R² = 0.9584, p = 0.021*). Tumor tissue with higher evolocumab titers demonstrated increased surface MHC-I and CD8⁺ T cell infiltration. Increased CD8⁺ TNF, FASLG and GZMA transcription was observed in high titer tissue compared to low titer tissue and untreated controls. Pre-resection evolocumab is well tolerated but exhibits BBB/BTB penetrance akin to other monoclonal antibodies. Increased tumoral evolocumab/PCSK9i may enhance tumoral MHC-I/effector CD8⁺ infiltration. Future work will explore combining evolocumab with BBB/BTB opening therapies like low-intensity focused ultrasound.