There are disclosed certain 1-[2-(aminomethyl)benzyl]-2-thioxo-1,2,3,5-tetrahydro-4H-pyrrolo[3,2-d]pyrimidin-4-one compounds of formula (I), and pharmaceutically acceptable salts thereof, together with compositions containing them and their use in therapy. The compounds are inhibitors of the enzyme MPO and are thereby particularly useful in the treatment or prophylaxis of cardiovascular disorders such as heart failure and coronary artery disease related conditions.