Search

Transferrin receptor 1 (TfR1) mediated transcytosis is an attractive strategy to enhance brain uptake of protein drugs, but translation remains a challenge. Here, a single domain shark antibody VNAR fragment (TXB2) with similar affinity to murine and human TfR1 was used to shuttle protein cargo into the brain. TXB2 was fused to a human IgG1 Fc domain (hFc) or to the amyloid-β (Aβ) antibody bapineuzumab (Bapi). TXB2-hFc displayed 20-fold higher brain concentrations compared with a control VNAR-hFc at 18 hours post-injection in wt mice. At the same time point, brain concentrations of Bapi-TXB2 was threefold higher than Bapi. In transgenic mice overexpressing human Aβ, the brain-to-blood concentration ratio increased with time due to interaction with intracerebral Aβ deposits. The relatively stable threefold difference between Bapi-TXB2 and Bapi was observed for up to 6 days after injection. PET imaging and ex vivo autoradiography revealed more parenchymal distribution of Bapi-TXB2 compared with Bapi. In conclusion, the TXB2 VNAR shuttle markedly increased brain uptake of protein cargo and increased brain concentrations of the Aβ binding antibody Bapi.

achieve this, selected changes to the heterocyclic nucleus, the linking atoms and the pendant aromatic rings were undertaken. Results: It is evident from this work that structure activity relationships exist around analogues of RS-0406 and that structural changes can result in significant improvements in its drug-like nature. We have discovered that modifications to the structure of RS-0406 have led to improvement in potency in both fibrillogenesis and cell viability assays. A new analogue, SEN1269, has been identified in which the central pyridazine ring has been replaced by a pyrimidine ring and an ether link was introduced along with the phenolic-OH replacement in one of the pendant aromatic rings. SEN1269 is more potent than RS-0406 and shows greater cell penetration, an improved in vitro ADME profile and absorption following oral dosing. In vivo, SEN1269 is also effective in rescuing the deficit in LTP caused by naturally-secreted oligomers of A . Furthermore, in an acute model of cognitive function in the rat using an alternating-lever cyclic-ratio paradigm, SEN1269 is effective in a dose-related manner in protecting against the deficit in cognitive behaviour induced by exogenously applied (ICV) naturally-secreted oligomers of A . Conclusions: SEN1269 represents a significant lead in the quest for a small molecule inhibitor of amyloid toxicity and supports the proposal that further evaluation of this chemical series is warranted.

Amyloid-beta (Abeta) protofibrils are known intermediates of the in vitro Abeta aggregation process and the protofibrillogenic Arctic mutation (APPE693G) provides clinical support for a pathogenic role of Abeta protofibrils in Alzheimer's disease (AD). To verify their in vivo relevance and to establish a quantitative Abeta protofibril immunoassay, Abeta conformation dependent monoclonal antibodies were generated. One of these antibodies, mAb158 (IgG2a), was used in a sandwich ELISA to specifically detect picomolar concentrations of Abeta protofibrils without interference from Abeta monomers or the amyloid precursor protein (APP). The specificity and biological significance of this ELISA was demonstrated using cell cultures and transgenic mouse models expressing human APP containing the Swedish mutation (APPKN670/671ML), or the Swedish and Arctic mutation in combination. The mAb158 sandwich ELISA analysis revealed presence of Abeta protofibrils in both cell and animal models, proving that Abeta protofibrils are formed not only in vitro, but also in vivo. Furthermore, elevated Abeta protofibril levels in the Arctic-Swedish samples emphasize the usefulness of the Arctic mutation as a model of enhanced protofibril formation. This assay provides a novel tool for investigating the role of Abeta protofibrils in AD and has the potential of becoming an important diagnostic assay.