Based on the hoarding there, it looks like a project by BHI Group. There's also a rendering posted onto it, which doesn't appear to be found anywhere online though.
Anyways, 6 storeys is a good level of increase for some lowkey mid-block intensification. Although, interesting that they're going for office spaces here. Wouldn't mind see a lot more of these gentle increases around these parts of Yonge Street for more residential too.