An agent isolated from tissues of the dogfish shark is proving to be a real contender in the battle against cancer in preclinical studies. Squalamine is a natural aminosterol, originally isolated from the liver of the dogfish shark and has previously been shown to have anti-infective properties. It has since been discovered that squalamine is also an angiogenesis inhibitor. Compared with cyclosporin alone, a combination of squalamine plus cyclophosphamide increased complete response rates and delayed tumour recurrence in a mouse model of breast cancer, according to results presented at the 20th Annual San Antonio Breast Cancer Symposium [Texas, US; December 1997]. Phase I clinical testing of squalamine is now underway.