One little known difference for atacicept is it deals with not only BLyS and APRIL, but also a heterotrimer that has been shown to induce B-cell proliferation in vitro. If that heterotrimer indeed has some causality in vivo, then only atacicept has the ability to get at it.
Unless otherwise indicated, this is the personal viewpoint of David Miller and not necessarily that of Biotech Stock Research, LLC