Research ArticleCancer

Discovery and pharmacological characterization of AZD3229, a potent KIT/PDGFRα inhibitor for treatment of gastrointestinal stromal tumors

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Science Translational Medicine  29 Apr 2020:
Vol. 12, Issue 541, eaaz2481
DOI: 10.1126/scitranslmed.aaz2481

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Getting the GIST of treatment

Gastrointestinal stromal tumor, or GIST, can be targeted by inhibiting KIT and platelet-derived growth factor α (PDGFRα). Unfortunately, the therapeutic effects do not always last, as the tumors develop resistance mutations that are not susceptible to existing drugs. Banks et al. report the design of AZD3229, a compound that combines selectivity for KIT and PDGFRα with broad activity against a variety of disease-causing mutations. Its selectivity decreases the risk of off-target toxicity, which has been a problem for multiple other KIT/PDGFRα inhibitors. AZD3229 showed promising activity and safety in a range of drug-resistant GIST mouse models, suggesting its potential for clinical translation.

Abstract

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma driven by mutations in KIT or platelet-derived growth factor α (PDGFRα). Although first-line treatment, imatinib, has revolutionized GIST treatment, drug resistance due to acquisition of secondary KIT/PDGFRα mutations develops in a majority of patients. Second- and third-line treatments, sunitinib and regorafenib, lack activity against a plethora of mutations in KIT/PDGFRα in GIST, with median time to disease progression of 4 to 6 months and inhibition of vascular endothelial growth factor receptor 2 (VEGFR2) causing high-grade hypertension. Patients with GIST have an unmet need for a well-tolerated drug that robustly inhibits a range of KIT/PDGFRα mutations. Here, we report the discovery and pharmacological characterization of AZD3229, a potent and selective small-molecule inhibitor of KIT and PDGFRα designed to inhibit a broad range of primary and imatinib-resistant secondary mutations seen in GIST. In engineered and GIST-derived cell lines, AZD3229 is 15 to 60 times more potent than imatinib in inhibiting KIT primary mutations and has low nanomolar activity against a wide spectrum of secondary mutations. AZD3229 causes durable inhibition of KIT signaling in patient-derived xenograft (PDX) models of GIST, leading to tumor regressions at doses that showed no changes in arterial blood pressure (BP) in rat telemetry studies. AZD3229 has a superior potency and selectivity profile to standard of care (SoC) agents—imatinib, sunitinib, and regorafenib, as well as investigational agents, avapritinib (BLU-285) and ripretinib (DCC-2618). AZD3229 has the potential to be a best-in-class inhibitor for clinically relevant KIT/PDGFRα mutations in GIST.

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