Combined effects of scanning ultrasound and a tau-specific single chain antibody in a tau transgenic mouse model.

Alzheimer's disease is characterized by the deposition of amyloid-ß as extracellular plaques and hyperphosphorylated tau as intracellular neurofibrillary tangles. Tau pathology characterizes not only Alzheimer's disease, but also many other tauopathies, presenting tau as an attractive therapeutic target. Passive tau immunotherapy has been previously explored; however, because only a small fraction of peripherally delivered antibodies crosses the blood-brain barrier, enters the brain and engages with tau that forms intracellular aggregates, more efficient ways of antibody delivery and neuronal uptake are warranted. In the brain, tau exists as multiple isoforms. Here, we investigated the efficacy of a novel 2N tau isoform-specific single chain antibody fragment, RN2N, delivered by passive immunization in the P301L human tau transgenic pR5 mouse model. We demonstrate that, in treated mice, RN2N reduces anxiety-like behaviour and phosphorylation of tau at distinct sites. When administration of RN2N was combined with focused ultrasound in a scanning mode (scanning ultrasound), RN2N delivery into the brain and uptake by neurons were markedly increased, and efficacy was significantly enhanced. Our study provides evidence that scanning ultrasound is a viable tool to enhance the delivery of biologics across the blood-brain barrier and improve therapeutic outcomes and further presents single-chain antibodies as an alternative to full-length antibodies.

Understanding nanomedicine treatment in an aggressive spontaneous brain cancer model at the stage of early blood brain barrier disruption.

Personalised nanomedicine is an advancing field which has developed significant improvements for targeting therapeutics to aggressive cancer and with fewer side effects. The treatment of gliomas such as glioblastoma (or other brain tumours), with nanomedicine is complicated by a commonly poor accumulation of drugs in tumour tissue owing to the partially intact blood-brain barrier (BBB). Nonetheless, the BBB becomes compromised following surgical intervention, and gradually with disease progression. Increased vasculature permeability generated by a tumour, combined with decreased BBB integrity, offers a mechanism to enhance therapeutic outcomes. We monitored a spontaneous glioma tumour model in immunocompetent mice with ongoing T2-weighted and contrast-enhanced T1-weighted magnetic resonance imaging gradient echo and spin echo sequences to predict an optimal "leakiness" stage for nanomedicine injections. To ascertain the effectiveness of targeted nanomedicines in treating brain tumours, subsequent systemic administration of targeted hyperbranched polymers was then utislised, to deliver the therapeutic payload when both the tumour and brain vascularity had become sufficiently susceptible to allow drug accumulation. Treatment with either doxorubicin-loaded hyperbranched polymer, or the same nanomedicine targeted to an ephrin receptor (EphA2) using a bispecific antibody, resulted in uptake of chemotherapeutic doxorubicin in the tumour and in reduced tumour growth. Compared to vehicle and doxorubicin only, nanoparticle delivered doxorubicin resulted in increased tumour apoptosis, while averting cardiotoxicity. This suggests that polyethylene based (PEGylated)-nanoparticle delivered doxorubicin could provide a more efficient treatment in tumours with a disrupted BBB, and that treatment should commence immediately following detection of gadolinium permeability, with early detection and ongoing 'leakiness' monitoring in susceptible patients being a key factor.

Tau antibody isotype induces differential effects following passive immunisation of tau transgenic mice.

One of the main pathological hallmarks of Alzheimer's disease (AD) is the intraneuronal accumulation of hyperphosphorylated tau. Passive immunotherapy is a promising strategy for the treatment of AD and there are currently a number of tau-specific monoclonal antibodies in clinical trials. A proposed mechanism of action is to engage and clear extracellular, pathogenic forms of tau. This process has been shown in vitro to be facilitated by microglial phagocytosis through interactions between the antibody-tau complex and microglial Fc-receptors. As this interaction is mediated by the conformation of the antibody's Fc domain, this suggests that the antibody isotype may affect the microglial phagocytosis and clearance of tau, and hence, the overall efficacy of tau antibodies. We therefore aimed to directly compare the efficacy of the tau-specific antibody, RN2N, cloned into a murine IgG1/κ framework, which has low affinity Fc-receptor binding, to that cloned into a murine IgG2a/κ framework, which has high affinity Fc-receptor binding. Our results demonstrate, for RN2N, that although enhanced microglial activation via the IgG2a/κ isotype increased extracellular tau phagocytosis in vitro, the IgG1/κ isoform demonstrated enhanced ability to reduce tau pathology and microgliosis following passive immunisation of the P301L tau transgenic pR5 mouse model.

Targeted camptothecin delivery via silicon nanoparticles reduces breast cancer metastasis.

In advanced breast cancer (BCa) patients, not the primary tumor, but the development of distant metastases, which occur mainly in the organ bone, and their adverse health effects are responsible for high mortality. Targeted delivery of already known drugs which displayed potency, but rather unfavorable pharmacokinetic properties, might be a promising approach to overcome the current limitations of metastatic BCa therapy. Camptothecin (CPT) is a highly cytotoxic chemotherapeutic compound, yet poorly water-soluble and non-specific. Here, CPT was loaded into porous silicon nanoparticles (pSiNP) displaying the epidermal growth factor receptor (EGFR)-targeting antibody (Ab) cetuximab to generate a soluble and targeted nanoscale delivery vehicle for cancer treatment. After confirming the cytotoxic effect of targeted CPT-loaded pSiNP in vitro on MDA-MB-231BO cells, nanoparticles were studied in a humanized BCa bone metastasis mouse model. Humanized tissue-engineered bone constructs (hTEBCs) provided a humanized microenvironment for BCa bone metastases in female NOD-scid IL2Rgnull (NSG) mice. Actively targeted CPT-loaded pSiNP led to a reduction of orthotopic primary tumor growth, increased survival rate and significant decrease in hTEBC and murine lung, liver and bone metastases. This study demonstrates that targeted delivery via pSiNP is an effective approach to employ CPT and other potent anti-cancer compounds with poor pharmacokinetic profiles in cancer therapy.

Ultrasound-mediated blood-brain barrier opening enhances delivery of therapeutically relevant formats of a tau-specific antibody.

The microtubule-associated protein tau is an attractive therapeutic target for the treatment of Alzheimer's disease and related tauopathies as its aggregation strongly correlates with disease progression and is considered a key mediator of neuronal toxicity. Delivery of most therapeutics to the brain is, however, inefficient, due to their limited ability to cross the blood-brain barrier (BBB). Therapeutic ultrasound is an emerging non-invasive technology which transiently opens the BBB in a focused manner to allow peripherally delivered molecules to effectively enter the brain. In order to open a large area of the BBB, we developed a scanning ultrasound (SUS) approach by which ultrasound is applied in a sequential pattern across the whole brain. We have previously shown that delivery of an anti-tau antibody in a single-chain variable fragment (scFv) format to the brain is increased with SUS allowing for an enhanced therapeutic effect. Here we compared the delivery of an anti-tau antibody, RN2N, in an scFv, fragment antigen-binding (Fab) and full-sized immunoglobulin G (IgG) format, with and without sonication, into the brain of pR5 tau transgenic mice, a model of tauopathy. Our results revealed that the full-sized IgG reaches a higher concentration in the brain compared with the smaller formats by bypassing renal excretion. No differences in either the ultrasound-mediated uptake or distribution in the brain from the sonication site was observed across the different antibody formats, suggesting that ultrasound can be used to successfully increase the delivery of therapeutic molecules of various sizes into the brain for the treatment of neurological diseases.