It relates to the compounds of formula (I), or their pharmaceutically or veterinary acceptable salts, or their stereoisomers or mixtures of stereoisomers, wherein R is a radical selected from the group consisting of formula (A), formula (B), formula (C), formula (D), and formula (E), and R1, R2, and R3 are as defined herein, which are inhibitors of one or more DNMTs selected from the group consisting of DNMT1, DNMT3A and DNMT3B. It also relates to pharmaceutical or veterinary compositions containing them, and to their use in medicine, in particular in the treatment and/or prevention of cancer, fibrosis and/or immunomodulation.