Discovery of a Highly Potent, Cell-Permeable Macrocyclic Peptidomimetic (MM-589) Targeting the WD Repeat Domain 5 Protein (WDR5)–Mixed Lineage Leukemia (MLL) Protein–Protein Interaction

Abstract

We report herein the design, synthesis, and evaluation of macrocyclic peptidomimetics that bind to WD repeat domain 5 (WDR5) and block the WDR5-mixed lineage leukemia (MLL) protein-protein interaction. Compound 18 (MM-589) binds to WDR5 with an IC₅₀ value of 0.90 nM (K_i value <1 nM) and inhibits the MLL H3K4 methyltransferase (HMT) activity with an IC₅₀ value of 12.7 nM. Compound 18 potently and selectively inhibits cell growth in human leukemia cell lines harboring MLL translocations and is >40 times better than the previously reported compound MM-401. Cocrystal structures of 16 and 18 complexed with WDR5 provide structural basis for their high affinity binding to WDR5. Additionally, we have developed and optimized a new AlphaLISA-based MLL HMT functional assay to facilitate the functional evaluation of these designed compounds. Compound 18 represents the most potent inhibitor of the WDR5-MLL interaction reported to date, and further optimization of 18 may yield a new therapy for acute leukemia.