Anti-angiogenic drugs target a common underlying biological aspect — the aberrant growth of blood vessels — in otherwise unrelated diseases. Although studied most extensively in oncology, anti-angiogenesis therapies have theoretical promise in multiple therapeutic areas1, posing several commercial challenges for the development of cross-therapeutic area (cross-TA) drugs. This is exemplified by Avastin (bevacizumab; Genentech). Avastin is a monoclonal antibody that targets vascular endothelial growth factor (VEGF), which was approved for the treatment of colon cancer in 2004, but also shows off-label activity in age-related macular degeneration (AMD). For the field of AMD, this has created an interesting scenario in which Lucentis (ranibizumab; Genentech/Novartis), an Avastin-related drug approved for AMD, competes directly with the off-label dosing of Avastin. The case study of Avastin versus Lucentis provides an excellent illustration of the commercial pitfalls of cross-TA drug development, and the possible approaches to manage these.