Abstract: The present invention relates to innovative protoparvoviruses (PV) expressing RNAi effectors, preferably shRNAs, against the CDK9 gene which display improved anticancer activity. These new viruses are based on the ?H-1PVsilencer platform that consists of a protoparvovirus H-1PV featuring an in-frame deletion within the NS region (?H-IPV) and harbouring a shRNA expression cassette in which the expression of the shRNA is controlled by the HI Polymerase III promoter. In this invention the inventors aimed to use the ?H-1PVsilencer to silence the CDK9 gene whose activity is often dysregulated in cancer cells and known to contribute to tumorigenesis. The present invention also provides cells or organisms comprising said parvovirus.