European orphan drug designation is designed to encourage companies to develop and market treatments for rare, life-threatening medical conditions that affect fewer than five people in every 10,000 in the European Union.
In addition to potential ten-year European market exclusivity following marketing approval, orphan drug status provides opportunities for regulatory assistance, reduced regulatory fees associated with applying for marketing approval, and protocol assistance.
The small-molecule drug, AP23573, is designed to starve cancer cells and shrink tumors by inhibiting the critical cell-signaling protein, mTOR, which regulates the response of tumor cells to nutrients and growth factors, and controls tumor blood supply and angiogenesis through effects on vascular endothelial growth factor (VEGF) in tumor and endothelial cells.
AP23573 also blocks the proliferation and migration of vascular smooth muscle cells, the primary cause of narrowing and reblockage of injured arteries, and is an analog of sirolimus, another mTOR inhibitor that has been approved for use in drug-eluting stents. AP23573 is currently in phase I and II clinical trials in patients with solid tumors and hematologic cancers. AP23573 has been designated both as a fast-track product and an orphan drug by the FDA for the treatment of soft-tissue and bone sarcomas.