The invention addresses in particular the problem resistant pathogens and cancer cells. A method is provided of applying a composition to a human or non-human individual or to an object or a surface area and a pharmaceutical composition with a regimen of administering it to a human or non-human individual is provided. The composition comprises an active chemical component for killing of or retarding proliferation of target cells including pathogens, infected cells and cancer cells. The application of the composition and the regimen of administration of the composition are accompanied by at least one exposure to electromagnetic radiation in a range of wavelength, in which the active chemical component absorbs and which has a lower limit of 190 nm thereby photo-activating the active component.