Structure-Based Rational Design of Constrained Peptides as TIM‑3 Inhibitors

Blocking the immunosuppressive function
of T-cell immunoglobulin
mucin-3 (TIM-3) is an established therapeutic strategy to maximize
the efficacy of immune checkpoint inhibitors for cancer immunotherapy.
Currently, effective inhibition of TIM-3 interactions relies on monoclonal
antibodies (mAbs), which come with drawbacks such as immunogenicity
risk, limited tumor penetration, and high manufacturing costs. Guided
by the X-ray cocrystal structures of TIM-3 with mAbs, we report an in silico structure-based rational design of constrained
peptides as potent TIM-3 inhibitors. The top cyclic peptide from our
study (P2) binds TIM-3 with a KD value of 166.3 ± 12.1 nM as determined by surface plasmon
resonance (SPR) screening. Remarkably, P2 efficiently
inhibits key TIM-3 interactions with natural TIM-3 ligands at submicromolar
concentrations in a panel of cell-free and cell-based assays. The
capacity of P2 to reverse immunosuppression in T-cell/cancer
cell cocultures, coupled with favorable in vitro pharmacokinetic
properties, highlights the potential of P2 for further
evaluation in preclinical models of immuno-oncology.