In the Summa Theologiae (particularly Ia IIae), Saint Thomas Aquinas repeatedly refers to Gregory of Nyssa and quotes from his work On Human Nature. However, Thomas is mistaken concerning the identity of the author. The author is not Gregory of Nyssa, but rather Nemesius (ca. 390). Nemesius was a Syrian Christian and the bishop of Emesa.
As far as I know, Nemesius' On Human Nature is the first major treatise dedicated to Christian anthropology.