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

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 (Ki 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.

本文报道了靶向WD重复结构域5（WD repeat domain 5, WDR5）、并阻断其与混合谱系白血病（mixed lineage leukemia, MLL）蛋白相互作用的大环拟肽类化合物的设计、合成与活性评价。化合物18（MM-589）对WDR5的结合活性IC₅₀值达0.90 nM（抑制常数Ki <1 nM），并以12.7 nM的IC₅₀值抑制MLL的组蛋白H3赖氨酸4甲基转移酶（H3K4 methyltransferase, HMT）活性。化合物18可强效且选择性地抑制携带MLL易位的人白血病细胞系的细胞增殖，其活性优于此前报道的化合物MM-401达40倍以上。化合物16与18分别与WDR5形成共晶复合物，其晶体结构为二者与WDR5的高亲和力结合提供了结构基础。此外，本研究开发并优化了一种基于AlphaLISA的MLL HMT功能检测方法，以助力上述设计化合物的功能评价。化合物18是目前已报道的靶向WDR5-MLL相互作用的最强效抑制剂，对其进行进一步优化有望为急性白血病治疗提供全新的候选疗法。