Did Irenaeus believe in transubstantiation?
It looks like Irenaeus (c. AD 202) did not believe in transubstantiation:
It was all spiritual for him. He believed like many of his time, in the spiritual participation in Christ. But, in noway he believed in literal transformation of bread and wine to blood and flesh as many would believe now under the influence of Catholic Church. Other than that, he would be a liar if he denies the accusation by Romans that Christians eat flesh and drink blood as he mentioned here.
For when the Greeks, having arrested the slaves of Christian catechumens, then used force against them, in order to learn from them some secret thing [practiced] among Christians, these slaves, having nothing to say that would meet the wishes of their tormentors, except that they had heard from their masters that the divine communion was the body and blood of Christ, and imagining that it was actually flesh and blood, gave their inquisitors answer to that effect. Then these latter, assuming such to be the case with regard to the practices of Christians, gave information regarding it to other Greeks, and sought to compel the martyrs Sanctus and Blandina to confess, under the influence of torture, [that the allegation was correct]. To these men Blandina replied very admirably in these words: ‘How should those persons endure such [accusations], who, for the sake of the practice [of piety], did not avail themselves even of the flesh that was permitted [them to eat]?’” (Irenaeus , Fragment 13)