Benzopyranone DNA-PK inhibitors

A compound of formula I wherein: R1, R2 = H, an optionally substituted alkyl, heterocyclic or aryl group, or together with the N an optionally substituted heterocyclic group, preferably a morpholino group; and one of R3, R4 or R5 = an optionally substituted phenyl and the others are H. Most preferably the compound has formula II. The compound is used as an adjunct in cancer therapy and in the treatment of retroviral diseases.