An orally bioavailable, synthetic, second-generation small-molecule inhibitor of heat shock protein 90 (Hsp90) with potential antineoplastic activity. Hsp90 inhibitor MPC-3100 selectively binds to Hsp90, thereby inhibiting its chaperone function and promoting the degradation of oncogenic signaling proteins involved in tumor cell proliferation and survival; this agent may inhibit the growth and survival of a wide variety of cancer cell types. Hsp90, a chaperone protein upregulated in a variety of tumor cells, regulates the folding, stability, and degradation of many oncogenic signaling proteins.