Inhibition of the T790M gatekeeper mutant of the epidermal growth factor receptor by EXEL-7647.

PURPOSE: Agents inhibiting the epidermal growth factor receptor (EGFR) have shown clinical benefit in a subset of non-small cell lung cancer patients expressing amplified or mutationally activated EGFR. However, responsive patients can relapse as a result of selection for EGFR gene mutations that confer resistance to ATP competitive EGFR inhibitors, such as erlotinib and gefitinib. We describe here the activity of EXEL-7647 (XL647), a novel spectrum-selective kinase inhibitor with potent activity against the EGF and vascular endothelial growth factor receptor tyrosine kinase families, against both wild-type (WT) and mutant EGFR in vitro and in vivo. EXPERIMENTAL DESIGN: The activity of EGFR inhibitors against WT and mutant EGFRs and their effect on downstream signal transduction was examined in cellular assays and in vivo using A431 and MDA-MB-231 (WT EGFR) and H1975 (L858R and T790M mutant EGFR) xenograft tumors. RESULTS: EXEL-7647 shows potent and long-lived inhibition of the WT EGFR in vivo. In addition, EXEL-7647 inhibits cellular proliferation and EGFR pathway activation in the erlotinib-resistant H1975 cell line that harbors a double mutation (L858R and T790M) in the EGFR gene. In vivo efficacy studies show that EXEL-7647 substantially inhibited the growth of H1975 xenograft tumors and reduced both tumor EGFR signaling and tumor vessel density. Additionally, EXEL-7647, in contrast to erlotinib, substantially inhibited the growth and vascularization of MDA-MB-231 xenografts, a model which is more reliant on signaling through vascular endothelial growth factor receptors. CONCLUSIONS: These studies provide a preclinical basis for clinical trials of XL647 in solid tumors and in patients bearing tumors that are resistant to existing EGFR-targeted therapies.

The Selective PI3K Inhibitor XL147 (SAR245408) Inhibits Tumor Growth and Survival and Potentiates the Activity of Chemotherapeutic Agents in Preclinical Tumor Models.

Dysregulation of PI3K/PTEN pathway components, resulting in hyperactivated PI3K signaling, is frequently observed in various cancers and correlates with tumor growth and survival. Resistance to a variety of anticancer therapies, including receptor tyrosine kinase (RTK) inhibitors and chemotherapeutic agents, has been attributed to the absence or attenuation of downregulating signals along the PI3K/PTEN pathway. Thus, PI3K inhibitors have therapeutic potential as single agents and in combination with other therapies for a variety of cancer indications. XL147 (SAR245408) is a potent and highly selective inhibitor of class I PI3Ks (α, ß, γ, and δ). Moreover, broad kinase selectivity profiling of >130 protein kinases revealed that XL147 is highly selective for class I PI3Ks over other kinases. In cellular assays, XL147 inhibits the formation of PIP3 in the membrane, and inhibits phosphorylation of AKT, p70S6K, and S6 in multiple tumor cell lines with diverse genetic alterations affecting the PI3K pathway. In a panel of tumor cell lines, XL147 inhibits proliferation with a wide range of potencies, with evidence of an impact of genotype on sensitivity. In mouse xenograft models, oral administration of XL147 results in dose-dependent inhibition of phosphorylation of AKT, p70S6K, and S6 with a duration of action of at least 24 hours. Repeat-dose administration of XL147 results in significant tumor growth inhibition in multiple human xenograft models in nude mice. Administration of XL147 in combination with chemotherapeutic agents results in antitumor activity in xenograft models that is enhanced over that observed with the corresponding single agents.

Characterization of the activity of the PI3K/mTOR inhibitor XL765 (SAR245409) in tumor models with diverse genetic alterations affecting the PI3K pathway.

Activation of the PI3K (phosphoinositide 3-kinase) pathway is a frequent occurrence in human tumors and is thought to promote growth, survival, and resistance to diverse therapies. Here, we report pharmacologic characterization of the pyridopyrimidinone derivative XL765 (SAR245409), a potent and highly selective pan inhibitor of class I PI3Ks (α, ß, γ, and δ) with activity against mTOR. Broad kinase selectivity profiling of >130 protein kinases revealed that XL765 is highly selective for class I PI3Ks and mTOR over other kinases. In cellular assays, XL765 inhibits the formation of PIP(3) in the membrane, and inhibits phosphorylation of AKT, p70S6K, and S6 phosphorylation in multiple tumor cell lines with different genetic alterations affecting the PI3K pathway. In a panel of tumor cell lines, XL765 inhibits proliferation with a wide range of potencies, with evidence of an impact of genotype on sensitivity. In mouse xenograft models, oral administration of XL765 results in dose-dependent inhibition of phosphorylation of AKT, p70S6K, and S6 with a duration of action of approximately 24 hours. Repeat dose administration of XL765 results in significant tumor growth inhibition in multiple human xenograft models in nude mice that is associated with antiproliferative, antiangiogenic, and proapoptotic effects.