Anti-MMAF monoclonal antibody

CD133/prominin-1 is a pentaspan transmembrane glycoprotein overexpressed in various solid tumours including colorectal and glioblastomas. CD133 was found here to be highly expressed in >= 50% of pancreatic, gastric and intrahepatic cholangiocarcinomas. Quantitative flow cytometric analysis showed that a panel of established hepatocellular, pancreatic and gastric cancer cell lines expressed CD133 at levels higher than normal epithelial cells or bone marrow progenitor cells. A murine anti-human CD133 antibody (AC133) conjugated to a potent cytotoxic drug, monomethyl auristatin F (MMAF), effectively inhibited the growth of Hep3B hepatocellular and KATO III gastric cancer cells in vitro with IC(50) values of 2-7 ng ml(-1). MMAF induced apoptosis in the cancer cells as measured by caspase activation. The anti-CD133-drug conjugate (AC133-vcMMAF) was shown to internalise and colocalised with the lysosomal marker CD107a in the sensitive cell lines. In contrast, in the resistant cell line Su.86.86, the conjugate internalised and colocalised with the caveolae marker, Cav-I. Addition of ammonium chloride, an inhibitor of lysosomal trafficking and processing, suppressed the cytotoxic effect of AC133-vcMMAF in both Hep3B and KATO III. Anti-CD133-drug conjugate treatment resulted in significant delay of Hep3B tumour growth in SCID mice. Anti-CD133 antibody-drug conjugates warrant further evaluation as a therapeutic strategy to eradicate CD133+tumours.

Protein poly-ADP-ribosylation (PARylation) plays vital roles in many aspects of physiology and pathophysiology. This posttranslational modification is catalyzed by poly-ADP-ribose polymerases (PARPs) through additions of ADP-ribose from nicotinamide adenine dinucleotide (NAD(+)) to protein residues, forming linear or branched poly-ADP-ribose (PAR) polymers. In this study, we explored a new concept of utilizing functionalized PAR polymers for targeted drug delivery. This was achieved by rapid and efficient generation of auto-PARylated PARP1 with 3 '-azido ADP-riboses and subsequent conjugations of anti-human epidermal growth factor receptor 2 (HER2) antibodies and monomethyl auristatin F (MMAF) payloads. This designed PARylated PARP1-antibody-MMAF conjugate could potently kill HER2-expressing cancer cells in high specificity. This proof-of-principle work demonstrates the feasibility of production of PAR polymer-based antibody-drug conjugate and its application in targeted delivery. The PAR polymer-based conjugates may lead to new types of therapeutics with potentially improved physicochemical and pharmacological properties.