Must an IRB review a study conducted after submission of a (510(k)) to FDA but prior to FDA’s decision on that submission?

Yes. During FDA’s review of the premarket notification submission, the device remains an investigational product. Therefore, the human subject protection (informed consent and additional safeguards for children in research), IRB, and IDE regulations apply. The device may not be distributed, except for investigational use, unless FDA clears the device for marketing.

Source: USFDA