From identification to functional characterization of cyriotoxin-1a, an antinociceptive toxin from the spider Cyriopagopus schioedtei.

BACKGROUND AND PURPOSE: The NaV 1.7 channel is highly expressed in dorsal root ganglia of the sensory nervous system and plays a central role in the pain signalling process. We investigated a library prepared from original venoms of 117 different animals to identify new selective inhibitors of this target. EXPERIMENTAL APPROACH: We used high throughput screening of a large venom collection using automated patch-clamp experiments on human voltage-gated sodium channel subtypes and then in vitro and in vivo electrophysiological experiments to characterize the active peptides that have been purified, sequenced, and chemically synthesized. Analgesic effects were evaluated in vivo in mice models. KEY RESULTS: We identified cyriotoxin-1a (CyrTx-1a), a novel peptide isolated from Cyriopagopus schioedtei spider venom, as a candidate for further characterization. This 33 amino acids toxin belongs to the inhibitor cystine knot structural family and inhibits hNaV 1.1-1.3 and 1.6-1.7 channels in the low nanomolar range, compared to the micromolar range for hNaV 1.4-1.5 and 1.8 channels. CyrTx-1a was 920 times more efficient at inhibiting tetrodotoxin (TTX)-sensitive than TTX-resistant sodium currents recorded from adult mouse dorsal root ganglia neurons and in vivo electrophysiological experiments showed that CyrTx-1a was approximately 170 times less efficient than huwentoxin-IV at altering mouse skeletal neuromuscular excitability properties. CyrTx-1a exhibited an analgesic effect in mice by increasing reaction time in the hot-plate assay. CONCLUSIONS AND IMPLICATIONS: The pharmacological profile of CyrTx-1a paves the way for further molecular engineering aimed to optimize the potential antinociceptive properties of this peptide.

SAR228810: an antibody for protofibrillar amyloid ß peptide designed to reduce the risk of amyloid-related imaging abnormalities (ARIA).

BACKGROUND: Anti-amyloid ß (Aß) immunotherapy represents a major area of drug development for Alzheimer's disease (AD). However, Aß peptide adopts multiple conformations and the pathological forms to be specifically targeted have not been identified. Aß immunotherapy-related vasogenic edema has also been severely dose limiting for antibodies with effector functions binding vascular amyloid such as bapineuzumab. These two factors might have contributed to the limited efficacy demonstrated so far in clinical studies. METHODS: To address these limitations, we have engineered SAR228810, a humanized monoclonal antibody (mAb) with limited Fc effector functions that binds specifically to soluble protofibrillar and fibrillar forms of Aß peptide and we tested it together with its murine precursor SAR255952 in vitro and in vivo. RESULTS: Unlike gantenerumab and BAN2401, SAR228810 and SAR255952 do not bind to Aß monomers, low molecular weight Aß oligomers or, in human brain sections, to Aß diffuse deposits which are not specific of AD pathology. Both antibodies prevent Aß42 oligomer neurotoxicity in primary neuronal cultures. In vivo, SAR255952, a mouse aglycosylated IgG1, dose-dependently prevented brain amyloid plaque formation and plaque-related inflammation with a minimal active dose of 3 mg/kg/week by the intraperitoneal route. No increase in plasma Aß levels was observed with SAR255952 treatment, in line with its lack of affinity for monomeric Aß. The effects of SAR255952 translated into synaptic functional improvement in ex-vivo hippocampal slices. Brain penetration and decoration of cerebral amyloid plaques was documented in live animals and postmortem. SAR255952 (up to 50 mg/kg/week intravenously) did not increase brain microhemorrhages and/or microscopic changes in meningeal and cerebral arteries in old APPSL mice while 3D6, the murine version of bapineuzumab, did. In immunotolerized mice, the clinical candidate SAR228810 demonstrated the same level of efficacy as the murine SAR255952. CONCLUSION: Based on the improved efficacy/safety profile in non-clinical models of SAR228810, a first-in-man single and multiple dose administration clinical study has been initiated in AD patients.