ERAP1 is a multifunctional enzyme trimming N-terminal amino acids of peptides. Its most characterised function is its role in generating peptide ligands in the endoplasmic reticulum for loading onto MHC class I (MHCI) molecules for presentation at the cell surface. Here it acts as an antigenic peptide editor influencing the peptide repertoire displayed at the cell surface to circulating CD8+ T cells and NK cells. ERAP1 modulates the immunopeptidome and could play a key role in tumor antigenicity.

ERAP1 is a highly dynamic enzyme and its conformation is crucial for intracellular immuno-signals and also various extracellular functions. The precise molecular mechanisms behind the secretion and conformational status of ERAP1 remain unclear. To study ERAP1, we combined a VHH and a small molecule approach. After Lama immunization, the selected ERAP1 binders were filtered for functional activity. To measure ERAP1 activity with relevant substrates, we developed a mass spectrometry assay and a fluorogenic substrate mimicking ERAP1 peptidic substrates. Nanobodies modulators of ERAP1 activity are currently used for structural studies.

In addition to the mechanistic studies, the team also developed ERAP1 small molecule modulators to induce or restore tumor immunogenicity. Herein, we report a chemical family of potent ERAP1 inhibitors that demonstrate structure activity relationship.

The nanobodies and small molecule modulators we developed provide useful tools to better understand the biology of ERAP1 in immune responses.

Citation Format: Nicolas Basse. A combined VHH and small molecule approach to modulate the antitumor immunity function of ERAP1 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6621.