The present invention pertains generally to the field of therapeutic compounds, and more specifically to 3-substituted-8-substituted-3H-imidazo[5,1-d][1,2,3,5]tetrazin-4-one compounds of the following formula, wherein -A and —B are as defined herein (collectively referred to herein as 38TM compounds): The present invention also pertains to pharmaceutical compositions comprising such compounds, and the use of such compounds and compositions, both in vitro and in vivo, to inhibit cell proliferation, and in the treatment of proliferative disorders such as cancer, etc., and methods of preparing such compounds.