NET
12 Not that I have already attained this—that is, I have not already been perfected—but I strive to lay hold of that for which Christ Jesus also laid hold of me.
Darby
12 Not that I have already obtained [the prize], or am already perfected; but I pursue, if also I may get possession [of it], seeing that also I have been taken possession of by Christ [Jesus].
KJV
12 Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus.