Is there any historical evidence that Gnosticism disappeared because Gnostics converted to Christianity?

In his article "Mysticism in the Early Church, in *The American Journal of Theology*, Aurther C McGiffert says, >Closely connected with Paul, John, and Ignatius are the Gnosics, the most famous heretics and the ablest thinkers of the second century who represent the later Platonic tendency in philosophy. Gnostics, like all the later Platonists, were dualists, primarily interested in the redemption of the spirit of man from his material environment; and they became Christians because they were convinced that in Christianity were to be found as nowhere else the means of such redemption. Christ, they believed, in revealing God to man, had placed redemption within the grasp of those capable of receiving and understanding his message, and through the knowledge imparted by him he had brought about a union with God, which means ultimately a complete and permanent break with the flesh and the world and an eternal life in the spiritual realm. Is there any historical evidence that Gnosticism disappeared because Gnostics converted to Christianity?