AT13387 is a novel, high-affinity, and non-geldanamycin inhibitor of the molecular chaperone Hsp90(heat-shock protein 90) by fragment based drug design. AT13387 can potently inhibit Hsp90 with IC50 of 18 nM in A375 cells. In vitro, AT13387 shows activity against a wide array of tumor cell lines, including lung cancer cell lines. AT13387 showed a median EC50 value of 41 nM against the PPTP and exhibited activity consistent with a cytotoxic effect.AT13387 can induce the degradation of specific HSP90 client proteins for up to 7 days in tumor cell lines in vitro. AT13387 caninhibit the proliferation of imatinib-sensitive (GIST882, GIST-T1) and -resistant (GIST430, GIST48) cell lines, including those resistant to the geldanamycin analogue HSP90 inhibitor, 17-AAG.
In vivo
In vivo, administered orally twice weekly, AT13387 induced significant differences in EFS distribution compared to controls in 17% evaluable solid tumor xenografts, but in none of the ALL xenografts. Once weekly administration in human lung carcinoma xenografts, treatment with AT13387 also can induce a long duration of client protein knockdown and suppression of phospho-signaling. Antitumor activity of AT13387 was showed in both the imatinib-sensitive, GIST-PSW, xenograft model and a newly characterized imatinib-resistant, GIST430, xenograft model.