15P - CBL E3 ubiquitin ligases are key inhibitory regulators in PD-1/LAG-3 co-signaling in human cancers, targeted through bispecific co-blockade

Background

A significant number of cancer patients do not benefit from PD-L1/PD-1 blockade immunotherapies. PD-1 and LAG-3 co-upregulation in T-cells is one of the major mechanisms of resistance by establishing a highly dysfunctional state in T-cells.

Methods

A high-throughput screening was performed of PD-1/LAG-3 multiomic expression profiles in public databases of human cancer biopsies, to establish relationships between infiltrating tumor-infiltrating PD-1/LAG-3 T cells with biomarkers both in T cells and within the tumour microenvironment. These results were validated in engineered T-cell lines with constitutively active PD-1, LAG-3 pathways, and their combination, analysed by high-throughput quantitative proteomics and validated by conventional molecular techniques on primary T cells from NSCLC patients.

Results

The high-throughput multiomic human cancers screening and the experimental proteomic T cell lines uncovered a strong PD-1/LAG-3 dysfunctionality signature that was found which regulated immune, proteomic, metabolic, genetic, and epigenetic pathways. These mainly relied on differential regulation of E3 ubiquitin ligases CBL-B and C-CBL. Notably, LAG-3 expression has never been associated to CBL ubiquitin ligases before.

Conclusions

PD-1/LAG-3 co-signaling profile uncovers a highly dysfunctional regulated programme. Co-blockade with a bispecific drug but not with a combination of anti-PD-1/anti-LAG-3 antibodies achieved both CBL-B and C-CBL inhibition, reverting T-cell dysfunctionality in lung cancer patients resistant to PD-L1/PD- 1 blockade. These results will help identifying the mechanisms of intrinsic resistance to PD-1 blockade mediated by LAG-3 co-signaling.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Navarrabiomed.

Funding

This research was supported by: The Spanish Association against Cancer (AECC), PROYE16001ESCO; Instituto de Salud Carlos III (ISCIII)-FEDER Project grants FIS PI20/00010, COV20/00000, and TRANSPOCART ICI19/00069; Biomedicine Project Grant from the Department of Health of the Government of Navarre-FEDER funds (BMED 050-2019, 51-2021); Strategic projects from the Department of Industry, Government of Navarre (AGATA, Ref. 0011-1411-2020-000013; LINTERNA, Ref. 0011-1411-2020-000033; DESCARTHES, 0011-1411-2019-000058); European Union Horizon 2020 ISOLDA project, under grant agreement ID: 848166. L.C. is financed by Instituto de Salud Carlos III (ISCIII), co-financed by FEDER funds, "Contratos PFIS: contratos predoctorales de formación en investigación en salud" (FI21/00080); M.E. is financed by the Navarrabiomed- Fundación Miguel Servet predoctoral contract.

Disclosure

C.J. Edwards: Other, Personal, Other, Declares to be inventor of the Humabody CB213 (WO/2019/158942. 603 Crescendo Biologics Ltd.): Crescendo Biologics. J. Leggs: Other, Declares to be e inventor of the Humabody CB213 (WO/2019/158942. 603 Crescendo Biologics Ltd.): Crescendo Biologics. D. Escors: Other, Declares to be e inventor of the Humabody CB213 (WO/2019/158942. 603 Crescendo Biologics Ltd.): Navarrabiomed. All other authors have declared no conflicts of interest.