In the US, like much of the developed world, cancer is the second most common cause of death after cardiovascular disease. Together between 1970 and 1994, Lung, Colon, Breast, Prostate and Pancreatic cancers claimed more than 5 million lives in the US alone. Considering these statistics and the often sub-optimal treatment options, it is unsurprising that anti-cancer drugs have received more attention from the pharmaceutical industry than any other drugs. 

The overall aim of cancer therapies is to reduce uncontrolled proliferation and spread, and naturally occurring molecules have traditionally received considerable attention in this respect. One group of molecules, the casomorphins are particularly exciting. These molecules were first identified in milk and were found to be potent inhibitors of proliferation. More recently a peptide sequence of opioid receptors has been identified with similar activity. At fentomolar concentrations they bind to opioid (notably kappa) and somatostatin receptors and reduce proliferation of a number of cancer types including prostate and breast cancer. The use of somatostatin in the treatment of cancer has already been rationalized through the development of molecules such as octreotide, however the development of anti-cancer opioid receptor ligands has lagged behind and no mixed kappa/somatostatin ligands have been reported. Kappa opioid ligands have been developed but as analgesics. 

The casomorphins are therefore novel and offer the unique possibility of reducing both the progression of tumors and the common occurrence of pain reported in cancer patients. The casomorphins have been well characterized and their chemical optimization or modeling offers excellent opportunities to companies involved in either cancer or pain research.