Which is more grammatically correct:
an XXX-inhibiting drug, or
an XXX inhibitor drug?
It would seem to me that the use of the verbal noun ("inhibiting") as a modifier is more grammatically acceptable than the deverbal form ("inhibitor"). I say this based on the observation that verbal nouns are generally more grammatically flexible since they retain verbal characteristics. However, I most often see cases of "inhibitor drug" in the literature than instances of "inhibiting drug".