AvidinOx-Lu-177-DOTA-Biotin

Oxidized form of avidin, named AvidinOX, provides stable fixation of biotinylated molecules in tissues thus representing a breakthrough in topical treatment of cancer. AvidinOX proved to be a stable receptor for radiolabeled biotin, biotinylated antibodies and cells. In order to expand applicability of the AvidinOX-based delivery platform, in the present study we investigated the possibility to hold biotinylated chemotherapeutics in AvidinOX-treated sites. A novel biotinylated gimatecan-derived camptothecin, coded ST8161AA1, was injected at suboptimal doses into human tumors xenografted in mice alone or pre-complexed to AvidinOX. Significantly higher growth inhibition was observed when the drug was anchored to AvidinOX suggesting the potential utility of this delivery modality for the local treatment of inoperable tumors.

AvidinOX, the oxidized derivative of Avidin, is a chemically modified glycoprotein, being currently under clinical investigation for targeted delivery of radioactive biotin to inoperable tumors. AvidinOX is produced by 4-hydroxyazobenzene-2-carboxylic acid (HABA)-assisted sodium periodate oxidation of Avidin. The peculiar property of the periodate-generated glycol-split carbohydrate moieties to form Schiff's bases with amino groups of the tissue proteins allows to achieve a tissue half-life of 2 weeks compared to 2 h of native Avidin. Carbohydrate oxidation, along with possible minor amino acid modifications, introduces additional microheterogeneity in the glycoprotein structure, making its characterization even more demanding than for native glycoproteins. Aiming at the elucidation of the effects of oxidation conditions on the AvidinOX protein backbone and sugars, this microheterogeneous glycoprotein derivative was characterized for the first time using a combination of different analytical methods, including colorimetric methods, mass spectrometry, hollow-fiber flow field-flow fractionation with UV and multi-angle laser scattering detection (HF5-UV-MALS), and NMR. The proposed integrated approach reveals structural features of AvidinOX relevant for its biological activity, e.g., oxidized sites within both carbohydrate moieties and protein backbone and conformational stability, and will be considered as an analytical tool for AvidinOX industrial preparations. It is worth noting that this study enriches also the structural data of native Avidin published up-to-date (e.g., glycan structure and distribution, peptide fingerprint, etc.). Graphical abstract Scheme of phenylacetic hydrazide/MALDI-TOF approach for quantification of aldehydes in AvidinOX based on the determination of the number of hydrazone adducts between hydrazide reagent and aldehyde groups of protein.