A call to arms

A paper by Genmab A/S researchers proposing a mechanism by which antibodies with IgG4 backbones may elicit side effects caught the attention of PanGenetics B.V., which is running a Phase I psoriatic arthritis trial of PG102, an antibody with an IgG4 backbone that targets CD40. PanGenetics suspected the article might result in a flurry of questions from either investors or regulators on whether such backbones possess a class effect that could lead to safety issues.

PanGenetics put together data to support its contention that antibody backbones were actually a red herring and that a better place to look for the source of side effects would be a mAb's mechanism. Indeed, PanGenetics is not alone in developing antibodies with IgG4 backbones-there are at least 2 such antibodies on the market and 10 more in the clinic (see Table 1, "IgG4 antibodies")...