A small molecule that can control an immune process that is crucial in the development of cancer and autoimmune disorders has been discovered by the University of Illinois at Chicago researchers.

Their discovery is reported in an Angewandte Chemie paper titled "Discovery of the First Selective Nanomolar Inhibitors of ERAP2 by Kinetic Target-Guided Synthesis." They first investigated how the immune system functions and why some diseases can be resistant to treatments before discovering the molecule, an enzyme inhibitor.

"Tumors have the ability to present cell-surface markers in the form of non-self peptide antigens, or neoantigens, which renders them exquisitely sensitive to recognition and elimination by T-cells, a form of immune cells that kill tumour cells upon recognition of neoantigens," said study corresponding author Marlene Bouvier, UIC professor of microbiology and immunology at the College of Medicine.

"The visibility of a tumour to T-cells is, therefore, a critical aspect of whether a T-cell-based immunotherapy treatment will be successful. Unfortunately, most tumours have low expression levels of neoantigens on their surfaces and, consequently, are resistant to immunotherapies."

Endoplasmic reticulum aminopeptidases 1 and 2, also known as ERAP1 and ERAP2, are proteins that are in charge of trimming and over-trimming peptide antigens and neoantigens inside of cells. For the study, the team examined these enzymes.

"Over-trimming of neoantigens in tumours by ERAPs represents missed opportunities to 'illuminate' tumours for recognition and destruction by T-cells," Bouvier said.

"As such, the modulation of ERAP1 and ERAP2 function with small molecule inhibitors offers an exciting approach to tone down their over-trimming function, increase tumour visibility, and enhance immune responses against tumours." The UIC team describes the first highly effective and specific small molecule ERAP2 inhibitors that were found in their study.

"We used kinetic target-guided synthesis to discover such inhibitors," Bouvier said. "We then used X-ray crystallography to reveal at the atomic level the binding mode of the small molecules, which allowed us to improve their design for greater potency and selectivity. We also showed that some optimised analogues represent lead compounds for drug discovery efforts."

According to the researchers, such small molecules of ERAP2 may be used in conjunction with other cancer therapies as well as for the treatment of autoimmune and infectious diseases, as well as other conditions that depend on antigen presentation on the cell surface.