There is no reason to say that it does not include Valentinus himself.

Positive evidence is wanting, but negative evidence still more.

Apart from evidence to the contrary, there must be a presumption against the introduction of a new work which becomes at once a frequently quoted authority midway in the history of a school.
But to keep to facts apart from presumptions.

Irenaeus represents Ptolemaeus as quoting largely from the Prologue to the Gospel.

But Ptolemaeus, as we have seen, had already gathered a school about him when Irenaeus became acquainted with him.