Macrocyclic ureas as potent and selective Chk1 inhibitors: An improved synthesis, kinome profiling, structure–activity relationships, and preliminary pharmacokinetics

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Abstract

A new series of potent macrocyclic urea-based Chk1 inhibitors are described. A detailed SAR study on the 4-position of the phenyl ring of the 14-member macrocyclic ureas 1a and d led to the identification of the potent Chk1 inhibitors 2, 57, 10, 13, 14, 1921, 25, 27, and 3134. These compounds significantly sensitize tumor cells to the DNA-damaging antitumor agent doxorubicin in a cell-based assay and efficiently abrogate the doxorubicin-induced G2/M and camptothecin-induced S checkpoints, indicating that the potent biological activities of these compounds are mechanism-based through Chk1 inhibition. Kinome profiling analysis of a representative macrocyclic urea 25 against a panel of 120 kinases indicates that these novel macrocyclic ureas are highly selective Chk1 inhibitors. Preliminary PK studies of 1a and b suggest that the 14-member macrocyclic inhibitors may possess better PK properties than their 15-member counterparts. An improved synthesis of 2 and 20 by using 2-(trimethylsilyl)ethoxycarbonyl (Teoc) to protect the amino group not only readily provided the desired compounds in pure form but also facilitated the scale up of potent compounds for various biological studies.

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Acknowledgments

The authors thank Drs. Zhenping Tian and Daniel Plata for scaling up a pyrazine-containing intermediate, Drs. Le Wang, Kent D. Stewart, and Chang Park for helpful discussion on the design of macrocyclic kinase inhibitors. The authors also thank the Department of Structural Chemistry for measuring NMR and MS spectra, the High-Through-Put Purification Group for analytical LC–MS.

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