When evaluated in vitro, the anti-CD38-IFNα(wt) immunocytokine proved highly effective at inhibiting CD38 positive ARP1 MM cell proliferation, with a similar potency as that of unmodified, wild type IFNα (hereafter referred to as native IFNα) (IC50s of 3.39 pM vs 4.92 pM, respectively; Fig 3A). Here, CD38 is linked to Miyoshi myopathy.