Leptomycin B

Leptomycin B (CAS 87081-35-4) is a small molecule that selectively inhibits the nuclear export receptor CRM1 (exportin 1), a protein essential for mediating nuclear export of various proteins involved in cancer progression, such as p53, c-Abl, and FOXO-3A. Leptomycin B treatment causes CRM1 redistribution, disrupting its nuclear-cytoplasmic transport function. In cellular assays, Leptomycin B shows potent antiproliferative activity, with IC50 values typically between 0.1 and 10 nM in diverse cancer cell lines, and approximately 4.23 nM averaged across multiple sarcoma-derived lines. Despite clear in vitro activity, its in vivo anti-tumor efficacy has been relatively limited, accompanied by notable toxicity, highlighting its importance primarily as a research tool for studying nuclear export mechanisms and associated cancer biology.