Emi1 regulates progression through early mitosis by preventing premature APC activation. Depleting Emi1 from cycling cells strongly delays cyclin B accumulation and mitotic entry, while expression of a stabilized form of Emi1 stabilizes APC substrates and causes a mitotic block. Emi1 binds the APC activators Cdc2O and Cdh1 and inhibits APC activation by Cdc20 or Cdh1. Hence, products that modulate the expression and/or activity of Emi1 have a therapeutic effect in the treatment of cancer, leukemia, solid tumors, chronic or acute inflammatory disease, restenosis, diabetes, neurological disorders, arthritis and osteoporosis, among other indications.