Phage Display-Derived Cyclic Peptides Target TREM2 and Modulate Microglial Responses Under Amyloid Stress

Triggering receptor expressed on myeloid cells 2 (TREM2) is a key regulator of microglial function and a promising therapeutic target in Alzheimer's disease. While current strategies have largely focused on antibody-based agonists, alternative modalities capable of modulating TREM2 signaling remain underexplored. Here, we report the discovery of TREM2-binding cyclic peptides using a disulfide-constrained phage display library. Screening and biophysical validation identified multiple binders, with TREM2-6 and TREM2-12 exhibiting micromolar affinity. Both peptides modulated microglial responses in human iPSC-derived model of amyloid stress and in neuron-microglia cocultures. Molecular dynamics simulations supported stable peptide-TREM2 interactions, with TREM2-12 displaying a more constrained binding mode. In vitro pharmacokinetic profiling revealed favorable plasma and intestinal stability but limited permeability, consistent with cyclic peptide scaffolds. Together, these findings establish cyclic peptides as a viable modality for targeting TREM2 and provide a foundation for the development of tunable neuroimmune therapeutics.