Hydrophobic weak base compounds such as hydrophobic weak base chemotherapeutic agents (which are not an anthracycline) for use in the treatment of medical conditions such as proliferative disease or disorder in a subject, in combination with illumination of a region in a body of the subject which is characterized by the presence of proliferating cells, are disclosed. The hydrophobic weak base compound and a wavelength of illumination are selected such that the hydrophobic weak base compound acts as a therapeutically effective photosensitizer when exposed to the illumination.