Morpholino oligonucleotide (MORF) (MORF)

Morpholino oligonucleotides (MORFs) are synthetic nucleic acid analogs where the ribose sugar is replaced by a morpholine ring and the phosphate backbone is replaced by non-ionic phosphorodiamidate linkages, making them highly resistant to nuclease degradation (Liu et al., 2002, Bioconjugate Chem). In the context of 'Complementary MORF oligonucleotide on other Fab'-MORF constructs,' this refers to a synthetic pretargeting system used in nuclear medicine and oncology. A primary antibody fragment (Fab') conjugated to a MORF sequence is first administered to localize at a tumor site by binding to a specific biological antigen. After the antibody has cleared from the blood, a secondary, complementary MORF (cMORF) carrying a diagnostic or therapeutic payload is administered, which binds to the localized MORF tag via high-affinity hybridization (He et al., 2010, Q J Nucl Med Mol Imaging). This strategy is designed to improve the tumor-to-background ratio by decoupling the slow targeting of the antibody from the rapid delivery and clearance of the effector molecule (Mang'era et al., 2001, Eur J Nucl Med). While a powerful tool for drug delivery, the MORF sequence itself is a synthetic linker and not a biological therapeutic target.

Other names

Phosphorodiamidate morpholino oligomercMORFComplementary MORFPMOMorpholino

Hybridization-based pretargeting via Watson-Crick base pairing between a synthetic MORF tag on a localized antibody and a subsequently administered complementary MORF probe.