Immunoglobulin G (IgG) antibodies have been studied and applied as biopharmaceuticals for decades, and they remain dominant in the monoclonal antibody (MAb) pipeline. By contrast, immunoglobulin M (IgM) molecules are much larger and consequently more challenging for biomanufacturing and therapeutic application. Essentially, they appear as clusters of the familiar Y-shaped IgG molecules, joined at their bases in pentameric (Figure 1) or hexameric forms. That structure gives them 10 and 12 binding moieties, respectively, which translate to superior binding power (avidity)…