Examining the Viability of a Nanobody-Oligo Conjugate for Drug Delivery to Muscle


Pre-Clinical Research

Poster Number: T351


Jenny Xu, Yale University, Kaiyue Ma, Yale, Angela Lek, PhD, MDA, Monkol Lek, PhD, Yale

Developing therapies for muscular dystrophies remains a significant challenge in the field of biomedical research. Antisense oligonucleotides (ASOs) such as PMOs have been explored as potential treatments, but suffer from low cellular uptake. Several antibody-oligonucleotide conjugates comprised of monoclonal antibodies (mAb) to the transferrin receptor (TfR) have shown potential to increase uptake and are in clinical trial as muscular dystrophy treatments. However, the use of mAbs means these therapies remain reliant on mammalian cell-based platforms for production. Replacing mAbs with the much smaller nanobodies (Nbs), which can be expressed in E. coli, may resolve this concern. We hypothesize that a Nb-PMO conjugate would present a viable, novel option for muscle-specific drug delivery. We aimed to examine the potential of a lab-produced Nb to TfR, as well as a Nb-albumin binding domain (ABD) fusion expected to improve half-life in the body, to be taken up via endocytosis. To create Nb, a 6xHis tag was added to a sequence from the Chou lab; to produce Nb-ABD, the G148-ABD3 sequence was fused between the Nb and the 6xHis tag. TfR Nb and Nb-ABD were produced and purified in E. coli. To confirm uptake via the endocytic pathway, immunofluorescence (IF) staining comparing Nb/Nb-ABD and commercial mAb was performed in human myoblasts overexpressing GFP-tagged Rab5/Rab7, endocytic markers known to colocalize with transferrin. Initial testing in fixed Rab5/Rab7-GFP cells revealed similar, vesicular colocalization for Nb and mAb, suggesting that TfR Nb is able to bind to a vesicular protein likely to be TfR. Live-uptake IF on Rab5-GFP cells revealed promising vesicular staining for Nb, Nb-ABD and mAb, although optimization may be necessary to confirm colocalization. Ultimately, we aim to examine the ability of a Nb-PMO conjugate for drug delivery to muscle, as well as produce a novel nanobody to a more muscle-specific receptor.