A surgical window of opportunity trial evaluating the effect of the PCSK9 inhibitor evolocumab on tumoral MHC-I expression and CD8+infiltration in glioma
Authors: Singh Kirit , Foster Matthew W. , Violette Marlene J. , Corcoran Anna M. , Hotchkiss Kelly M. , Railton Chelsea O. , Blandford Emily E. , Blethen Kathryn E. , Thomas Elizabeth L. , Ashley David M. , Desjardins Annick , Friedman Henry S. , Johnson Margaret O. , Friedman Allan , Keir Stephen , Buckley Evan D. , Herndon James E. , McLendon Roger E. , Sampson John H. , Calabrese Evan , Lopez Giselle Y. , Grant Gerald A. , Patel Anoop P. , Gregory Simon G. , Li Chuan-Yuan , Fecci Peter E. , Khasraw Mustafa 
Published: June 2024

ABSTRACTBackgroundMany 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 (mAbs) have limited blood brain/tumor barrier penetrance (BBB/BTB). The aim of this window-of-opportunity trial was to evaluate evolocumab’s BBB/BTB penetrance and biological effect in glioma (PesKE;NCT04937413).MethodPatients with newly diagnosed/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 subcutaneous evolocumab 4-14 days pre-procedure. 4/6 intervention participants provided research tissue.ResultsNo 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 mAbs. Evolocumab quantitation was 4.44x 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,FASLGandGZMAtranscription was observed in high titer tissue compared to low titer tissue/untreated controls.ConclusionsPre-resection evolocumab is well tolerated but exhibits BBB/BTB penetrance akin to other mAbs. 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.Key pointsPCSK9 promotes MHC-I degradation and is increased in gliomaEvolocumab (PCSK9 mAb inhibitor) exhibits BBB penetrance akin to other mAbsTumoral evolocumab titers correlates with tumor cell surface MHC-I expressionImportance of the studyThis tissue-based study evaluates the pre-clinical finding that PCSK9 inhibition (PCSK9i) increases cell surface MHC-I expression in the clinical glioma setting. Of note, PCSK9 is specifically elevated in glioma, a tumor which is known for low MHC-I expression and typically possesses few tumor-infiltrating lymphocytes. PCSK9i was achieved by means of a peripherally administered monoclonal antibody (mAb, evolocumab). Though uptake of evolocumab across the blood-brain/tumor barrier (BBB/BTB) was similar to other mAbs, dose-response relationships between intratumoral evolocumab and MHC-I subtypes were observed. Having observed that PCSK9i can induce biological changes within tumor, we will rationalize our approach to explore combination with BBB/BTB opening therapies such as low-intensity focused ultrasound. Window-of-opportunity studies like PesKE demonstrate how tissue-based trials permit rapid evaluation of a drugs pharmacokinetic (PK) and pharmacodynamic (PD) properties in glioma. Here, we find evidence of PD (biological) effect and will now explore combination approaches to enhance PK parameters (tumoral uptake).Graphical Abstract