Amulirafusp alfa

CD47, as the 'don't eat me' signal, interacts with the inhibitory signal-regulatory protein alpha (SIRPα) receptor expressed by myeloid cells and activated NK cells and is overexpressed in different malignancies, causing tumors to escape the phagocytosis of macrophages.Here, we describe the antitumor mechanism of IMM0306, a fusion protein of CD20 monoclonal antibody (mAb) with the CD47 binding domain of SIRPα , by activating both macrophages and NK cells via blockade of CD47-SIRPα interaction and FcγR engagement by simultaneously binding to CD47 and CD20 of B cells in different mouse xenograft tumor models.IMM0306 is a fusion protein of CD20 mAb with the CD47 binding domain of SIRPα on both heavy chains, that was constructed and produced using an inhouse developed CHO-K1 cell expression system; whose binding activity was analyzed by flow cytometry.The phagocytosis and in vitro anti-tumor activity of IMM0306 were evaluated by antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cell-mediated cytotoxicity (ADCC), and complement-dependent cytotoxicity (CDC) assays.The ADCC assay showed that IMM0306 has strong ADCC induced by activating NK cells through enhanced Fc/ FcγRRIIIa interaction.In conclusion, our data demonstrated that IMM0306, a fusion protein of CD20 mAb with the CD47 binding domain of SIRPα , exerts excellent cancer killing efficacy by activating both macrophages and NK cells via blockade of CD47-SIRPα interaction and FcγR engagement by simultaneously binding to CD47 and CD20 of B cells.We conclude the mechanism of action of IMM0306 by blocking the CD47 'don't eat me' signal and activating the Fc-receptor 'eat me' signal of CD20 with a strong ADCP to make the B-cell fully killed, whereas CD47 mAbs and rituximab can only either block the CD47 'don't eat me' signal or activate the Fc-receptor 'eat me' signal of CD20 with limited ADCP to make the limited B-cell killed.The Fc segment of the recombinant protein in IMM0306 is IgG1 and has been modified by ADCC-enhanced genetic engineering.Therefore, it has strong in vivo efficacy (through ADCC and ADCP).For other CD47 BsAbs, because the CD47 antibody itself combines with red blood cells, IgG1 cannot be selected; otherwise, it will have severe anemia toxicity.Therefore, this data revealed that IMM0306 has a safer profile and superior therapeutic potential than other CD47 mAbs and BsAbs.