English to German Medical Medical: Pharmaceuticals Oncology

An oncological treatment is described as "a phase-derived IgG1 antibody targeting human PD-L1."

This is a study patient card informing doctors about their patient participating in a clinical study and taking this study drug. The entire study protocol does not even once mention "phase-derived" (nor any other clue with respect to the nature of the study drug and the meaning of "phase-derived"). Neither does the SmPC of the drug.

Even Google draws a blank on "phase-derived antibody", "phase-derived immunoglobulin" and similar searches. I have no idea if this is about study phases I, II, III, or phases of an immunologic reaction, and I even don't seem able to come up with a vague translation covering any eventualities.

Has anybody come across this term in context with antibodies or oncological treatments?

VDIV!