Leontius of Byzantium and Transubstantiation

Q. Did Leontius advocate the Roman dogma of transubstantiation?

Leontius, Monk of Byzantium (c. 485-543 A.D.):

The supernatural leads up and elevates the natural, and empowers it for more perfect actions, such as it could not accomplish if it remained within the limits of the natural. The supernatural therefore does not destroy the natural but educes and stimulates it both in its capacity for actions of its own and in its receiving power for those things which are beyond this capacity. (J. P. Minge, Patrologiæ Cursus Completus, [1860], Patrologiæ Græcæ, Tomus LXXXVI, Leontii Byzantini, Contra Nestor. Et Eutych., Liber Secundus, Col. 1333). Here Trans. (Darwell Stone, A History of the Doctrine of the Holy Eucharist, [1909], Volume I, p. 135). Here

Compare with the United States Conference of Catholic Bishops:

4. Does the bread cease to be bread and the wine cease to be wine?

Yes. In order for the whole Christ to be present—body, blood, soul, and divinity—the bread and wine cannot remain, but must give way so that his glorified Body and Blood may be present. Thus in the Eucharist the bread ceases to be bread in substance, and becomes the Body of Christ, while the wine ceases to be wine in substance, and becomes the Blood of Christ. As St. Thomas Aquinas observed, Christ is not quoted as saying, " This bread is my body," but " This is my body" (Summa Theologiae, III q. 78, a. 5). Source

~ Soli Deo Gloria