David A Fruman, Christian Rommel
Department of Molecular Biology and Biochemistry and Institute for Immunology, University of California, Irvine, Irvine, California 92697-3900, USA. dfruman@uci.edu
Cancer discovery 2011 DecSeveral phosphoinositide 3-kinase (PI3K) inhibitors are in the clinic and many more are in preclinical development. CAL-101, a selective inhibitor of the PI3Kδ isoform, has shown remarkable success in certain hematologic malignancies. Although PI3Kδ signaling plays a central role in lymphocyte biology, the degree of single-agent therapeutic activity of CAL-101 during early-phase development has been somewhat unexpected. CAL-101 works in part by blocking signals from the microenvironment that normally sustain leukemia and lymphoma cells in a protective niche. As PI3Ks enter the arena of molecular-targeted therapies, CAL-101 provides proof of principle that isoform-selective compounds can be effective in selected cancer types and patient populations. Significance: A key question is whether compounds targeting a single PI3K catalytic isoform can provide meaningful single agent efficacy in cancer cells that express multiple isoforms. Clinical studies of the drug CAL-101 have provided a significant advance by showing that selective targeting of PI3Kδ achieves efficacy in chronic lymphocytic leukemia, in part through targeting the tumor microenvironment.
David A Fruman, Christian Rommel. PI3Kδ inhibitors in cancer: rationale and serendipity merge in the clinic. Cancer discovery. 2011 Dec;1(7):562-72
PMID: 22586681
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