Irreversible inhibitors of the EGF receptor may circumvent acquired resistance to gefitinib

Non-small cell lung cancers (NSCLCs) with activating mutations in the kinase domain of the epidermal growth factor receptor (EGFR) demonstrate dramatic, but transient, responses to the reversible tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva). Some recurrent tumors have a common secondary mutation in the EGFR kinase domain, T790M, conferring drug resistance, but in other cases the mechanism underlying acquired resistance is unknown. In studying multiple sites of recurrent NSCLCs, we detected T790M in only a small percentage of tumor cells. To identify additional mechanisms of acquired resistance to gefitinib, we used NSCLC cells harboring an activating EGFR mutation to generate multiple resistant clones in vitro. These drug-resistant cells demonstrate continued dependence on EGFR and ERBB2 signaling for their viability and have not acquired secondary EGFR mutations. However, they display increased internalization of ligand-activated EGFR, consistent with altered receptor trafficking. Although gefitinib-resistant clones are cross-resistant to related anilinoquinazolines, they demonstrate sensitivity to a class of irreversible inhibitors of EGFR. These inhibitors also show effective inhibition of signaling by T790M-mutant EGFR and killing of NSCLC cells with the T790M mutation. Both mechanisms of gefitinib resistance are therefore circumvented by irreversible tyrosine kinase inhibitors. Our findings suggest that one of these, HKI-272, may prove highly effective in the treatment of EGFR-mutant NSCLCs, including tumors that have become resistant to gefitinib or erlotinib

Induction of BIM Is Essential for Apoptosis Triggered by EGFR Kinase Inhibitors in Mutant EGFR-Dependent Lung Adenocarcinomas

Using a panel of human drug-sensitive EGFR mutant lung cancer cells, William Pao and colleagues show that induction of BIM, a member of the BCL2 family, is essential for apoptosis triggered by EGFR kinase inhibitors

Oncogenic Transformation by Inhibitor-Sensitive and -Resistant EGFR Mutants

BACKGROUND: Somatic mutations in the kinase domain of the epidermal growth factor receptor tyrosine kinase gene EGFR are common in lung adenocarcinoma. The presence of mutations correlates with tumor sensitivity to the EGFR inhibitors erlotinib and gefitinib, but the transforming potential of specific mutations and their relationship to drug sensitivity have not been described. METHODS AND FINDINGS: Here, we demonstrate that EGFR active site mutants are oncogenic. Mutant EGFR can transform both fibroblasts and lung epithelial cells in the absence of exogenous epidermal growth factor, as evidenced by anchorage-independent growth, focus formation, and tumor formation in immunocompromised mice. Transformation is associated with constitutive autophosphorylation of EGFR, Shc phosphorylation, and STAT pathway activation. Whereas transformation by most EGFR mutants confers on cells sensitivity to erlotinib and gefitinib, transformation by an exon 20 insertion makes cells resistant to these inhibitors but more sensitive to the irreversible inhibitor CL-387,785. CONCLUSION: Oncogenic transformation of cells by different EGFR mutants causes differential sensitivity to gefitinib and erlotinib. Treatment of lung cancers harboring EGFR exon 20 insertions may therefore require the development of alternative kinase inhibition strategies

Data from TTI-237: A Novel Microtubule-Active Compound with <i>In vivo</i> Antitumor Activity

&lt;div&gt;Abstract&lt;p&gt;5-Chloro-6-[2,6-difluoro-4-[3-(methylamino)propoxy]phenyl]-&lt;i&gt;N&lt;/i&gt;-[(1&lt;i&gt;S&lt;/i&gt;)-2,2,2-trifluoro-1-methylethyl]-[1,2,4]triazolo[1,5-&lt;i&gt;a&lt;/i&gt;]pyrimidin-7-amine butanedioate (TTI-237) is a microtubule-active compound of novel structure and function. Structurally, it is one of a class of compounds, triazolo[1,5a]pyrimidines, previously not known to bind to tubulin. Functionally, TTI-237 inhibited the binding of [&lt;sup&gt;3&lt;/sup&gt;H]vinblastine to tubulin, but it caused a marked increase in turbidity development that more closely resembled the effect observed with docetaxel than that observed with vincristine. The morphologic character of the presumptive polymer is unknown at present. When applied to cultured human tumor cells at concentrations near its IC&lt;sub&gt;50&lt;/sub&gt; value for cytotoxicity (34 nmol/L), TTI-237 induced multiple spindle poles and multinuclear cells, as did paclitaxel, but not vincristine or colchicine. Flow cytometry experiments revealed that, at low concentrations (20–40 nmol/L), TTI-237 produced sub-G&lt;sub&gt;1&lt;/sub&gt; nuclei and, at concentrations above 50 nmol/L, it caused a strong G&lt;sub&gt;2&lt;/sub&gt;-M block. The compound was a weak substrate of multidrug resistance 1 (multidrug resistance transporter or P-glycoprotein). In a cell line expressing a high level of P-glycoprotein, the IC&lt;sub&gt;50&lt;/sub&gt; of TTI-237 increased 25-fold whereas those of paclitaxel and vincristine increased 806-fold and 925-fold, respectively. TTI-237 was not recognized by the MRP or MXR transporters. TTI-237 was active &lt;i&gt;in vivo&lt;/i&gt; in several nude mouse xenograft models of human cancer, including LoVo human colon carcinoma and U87-MG human glioblastoma, when dosed i.v. or p.o. Thus, TTI-237 has a set of properties that distinguish it from other classes of microtubule-active compounds. [Cancer Res 2008;68(7):2292–300]&lt;/p&gt;&lt;/div&gt;</jats:p

Supplementary Tables 1-5, Figures 1-5 from TTI-237: A Novel Microtubule-Active Compound with &lt;i&gt;In vivo&lt;/i&gt; Antitumor Activity

Supplementary Tables 1-5, Figures 1-5 from TTI-237: A Novel Microtubule-Active Compound with &lt;i&gt;In vivo&lt;/i&gt; Antitumor Activity</jats:p

Supplementary Tables 1-5, Figures 1-5 from TTI-237: A Novel Microtubule-Active Compound with &lt;i&gt;In vivo&lt;/i&gt; Antitumor Activity

Supplementary Tables 1-5, Figures 1-5 from TTI-237: A Novel Microtubule-Active Compound with &lt;i&gt;In vivo&lt;/i&gt; Antitumor Activity</jats:p

Data from TTI-237: A Novel Microtubule-Active Compound with &lt;i&gt;In vivo&lt;/i&gt; Antitumor Activity

&lt;div&gt;Abstract&lt;p&gt;5-Chloro-6-[2,6-difluoro-4-[3-(methylamino)propoxy]phenyl]-&lt;i&gt;N&lt;/i&gt;-[(1&lt;i&gt;S&lt;/i&gt;)-2,2,2-trifluoro-1-methylethyl]-[1,2,4]triazolo[1,5-&lt;i&gt;a&lt;/i&gt;]pyrimidin-7-amine butanedioate (TTI-237) is a microtubule-active compound of novel structure and function. Structurally, it is one of a class of compounds, triazolo[1,5a]pyrimidines, previously not known to bind to tubulin. Functionally, TTI-237 inhibited the binding of [&lt;sup&gt;3&lt;/sup&gt;H]vinblastine to tubulin, but it caused a marked increase in turbidity development that more closely resembled the effect observed with docetaxel than that observed with vincristine. The morphologic character of the presumptive polymer is unknown at present. When applied to cultured human tumor cells at concentrations near its IC&lt;sub&gt;50&lt;/sub&gt; value for cytotoxicity (34 nmol/L), TTI-237 induced multiple spindle poles and multinuclear cells, as did paclitaxel, but not vincristine or colchicine. Flow cytometry experiments revealed that, at low concentrations (20–40 nmol/L), TTI-237 produced sub-G&lt;sub&gt;1&lt;/sub&gt; nuclei and, at concentrations above 50 nmol/L, it caused a strong G&lt;sub&gt;2&lt;/sub&gt;-M block. The compound was a weak substrate of multidrug resistance 1 (multidrug resistance transporter or P-glycoprotein). In a cell line expressing a high level of P-glycoprotein, the IC&lt;sub&gt;50&lt;/sub&gt; of TTI-237 increased 25-fold whereas those of paclitaxel and vincristine increased 806-fold and 925-fold, respectively. TTI-237 was not recognized by the MRP or MXR transporters. TTI-237 was active &lt;i&gt;in vivo&lt;/i&gt; in several nude mouse xenograft models of human cancer, including LoVo human colon carcinoma and U87-MG human glioblastoma, when dosed i.v. or p.o. Thus, TTI-237 has a set of properties that distinguish it from other classes of microtubule-active compounds. [Cancer Res 2008;68(7):2292–300]&lt;/p&gt;&lt;/div&gt;</jats:p