The present disclosure relates to a group B adenovirus comprising a sequence of formula (I): 5′ITR-B1-BAB2-BX-BB-BY-B3-3′ITR wherein: B1 is bond or comprises: E1A, E1B or E1AE1B; BA comprises: E2B-L1-L2-L3-E2A-L4; B2 is a bond or comprises: E3; BX is a bond or a DNA sequence comprising: a restriction site, one or more transgenes or both; BB comprises L5; BY is a bond or a DNA sequence comprising: a restriction site, one or more transgenes or both; B3 is a bond or comprises: E4; wherein at least one of BX or BY is not a bond, pharmaceutical compositions comprising the same and use of the viruses and compositions in treatment, particularly in the treatment of cancer. The disclosure also extends to plasmids and processes employed to prepare the said viruses.