Hi Chessman,
I'm not aware of a single Anti-Nicene writer that believed OSAS. What you posted from Irenaeus doesn't show He believed OSAS. In order for anyone to prove OSAS, they must prove that man cannot change his mind once saved. That is the crux of the OSAS argument. What you've highlighted doesn't prove OSAS because it's referring to the believer. No one is suggesting that the believer will be lost, it's the one who turns from believing that will be lost..
Here is Irenaeus actually addressing this issue.
These men of old time, …. for whom the Son of God had not yet suffered, when they committed any sin and served fleshly lusts, were rendered objects of great disgrace. Accordingly, what will the men of the present day suffer, who have despised the Lord's coming, and have become the slaves of their own lusts? Truly, the death of the Lord brought healing and remission of sins to the former. However, Christ will not die again on behalf of those who now commit sin. For death will no more have dominion over Him …. We should not, therefore, as that presbyter remarks, be puffed up, nor be severe upon those of olden times. Rather, we should fear ourselves, least perchance, after [we have come to] the knowledge of Christ, if we do things displeasing to God, we obtain no further forgiveness of sins, but are shut out from His kingdom. And for that reason, Paul said, “for if [God] spared not the natural branches, [take heed] lest he also not spare you.” Irenaeus (c.180, E/W), 1.499.
According to nature, then — that is, according to creation, so to speak — we are all sons of God, because we have all been created by God. But with respect to obedience and doctrine we are not all the sons of God: those only are so who believe in Him and do His will. And those who do not believe, and do not obey His will, are sons and angels of the devil, because they do the works of the devil. And that such is the case He has declared in Isaiah: “I have begotten and brought up children, but they have rebelled against Me.” And again, where He says that these children are aliens: “Strange children have lied unto Me.” According to nature, then, they are [His] children, because they have been so created; but with regard to their works, they are not His children.
3. For as, among men, those sons who disobey their fathers, being disinherited, are still their sons in the course of nature, but by law are disinherited, for they do not become the heirs of their natural parents; so in the same way is it with God, — those who do not obey Him being disinherited by Him, have ceased to be His sons.
Early Church Fathers - – Ante-Nicene Fathers: The Writings of the Fathers Down To A.D. 325.
These passages are addressing the issue of those who do not continue in following Christ. There are no inferences in these passages.