Retaspimycin (IPI-504) was previously under development by manufacturer Infinity Pharmaceuticals in conjunction with MedImmune, a part of AstraZeneca. Retaspimycin is a small-molecule inhibitor of heat shock protein 90 (HSP90) with antiproliferative and antineoplastic activities. Retaspimycin binds to and inhibits the cytosolic chaperone functions of HSP90, which maintains the stability and functional shape of many oncogenic signaling proteins and may be overexpressed or overactive in tumor cells. Retaspimycin-mediated inhibition of HSP90 promotes the proteasomal degradation of oncogenic signaling proteins in susceptible tumor cell populations, which may result in the induction of apoptosis. Orphan drug designation was assigned to the compound by the FDA for the treatment of gastrointestinal stromal cancer (GIST). Infinity Pharmaceuticals has discontinued the development of retaspimycin (IPI-504) an inhibitor of the HSP-90) complex, for the treatment of cancer due to lack of efficacy in 1913.

Retaspimycin (IPI-504) was previously under development by manufacturer Infinity Pharmaceuticals in conjunction with MedImmune, a part of AstraZeneca. Retaspimycin is a small-molecule inhibitor of heat shock protein 90 (HSP90) with antiproliferative and antineoplastic activities. Retaspimycin binds to and inhibits the cytosolic chaperone functions of HSP90, which maintains the stability and functional shape of many oncogenic signaling proteins and may be overexpressed or overactive in tumor cells. Retaspimycin-mediated inhibition of HSP90 promotes the proteasomal degradation of oncogenic signaling proteins in susceptible tumor cell populations, which may result in the induction of apoptosis. Orphan drug designation was assigned to the compound by the FDA for the treatment of gastrointestinal stromal cancer (GIST). Infinity Pharmaceuticals has discontinued the development of retaspimycin (IPI-504) an inhibitor of the HSP-90) complex, for the treatment of cancer due to lack of efficacy in 1913.