AT13387, an inihibitor of HSP90 with options for oral delivery, is currently being administered as an intravenous formulation in a Phase II trial for patients with gastrointestinal stromal tumor (GIST cancer) in combination with imatinib, and also in a Phase I study in cancer patients with solid tumors.
Definition from NCI Drug Directory: A synthetic, orally bioavailable, small-molecule inhibitor of heat shock protein 90 (Hsp90) with potential antineoplastic activity. Hsp90 inhibitor AT13387 selectively binds to Hsp90, thereby inhibiting its chaperone function and promoting the degradation of oncogenic signaling proteins involved in tumor cell proliferation and survival. Hsp90, a chaperone protein upregulated in a variety of tumor cells, regulates the folding, stability and degradation of many oncogenic signaling proteins
The HSP90 inhibitor, AT13387, demonstrates potent anti-tumor activity in both imatinib-sensitive and imatinib-resistant gastrointestinal stromal tumor models.
Smyth et al poster number A217 presented in November 2011 at AACR/NCI/EORTC conference on Molecular Targets and Cancer Therapeutics.
Here is a quote from the abstract: "In vivo, the efficacy of AT13387 was tested in imatinib-sensitive (GIST-PSW) and imatinib-resistant (GIST430) xenograft models. AT13387, dosed once a week, inhibited the growth of both xenografts; depletion of phospho-KIT and inhibition of KIT signalling were again seen in these tumors. As expected, treatment with imatinib caused significant regression of the GIST-PSW tumors but not of GIST430. The combination of imatinib and AT13387 significantly enhanced tumor growth inhibition (T/C 21%) over either of the monotherapies (T/C 30% for AT13387, 46% for imatinib) in the GIST430 xenograft. Importantly, the combination was well tolerated."