In vitro neuronal electrical activity can predict in vivo acute neurotoxicity of ASO

For ASOs (AntiSense Oligonucleotide) to be administrated via the IT route in patients, acute tolerability is evaluated in vivo in mice by behavioral side effects observation using Functional Observational Battery (FOB) performed 1 h following the single ICV (Intra Cerebro Ventricular) bolus injection.To support the 3R initiative and reduce the number of ASO tested in vivo, our objective was to develop an in vitro assay able to predict acute neurotoxicity observed in vivo.

To establish the vitro/vivo correlation, we measured effect of 35 ASOs on electrical activity of primary neurons using Micro Electrode Array (MEA) technology and compared it to 1 h FOB score. ASOs were incubated 30 min at 1, 3 and 10 μM. Electrical activity was recorded for 5 min at the end of each incubation period.

Among the >50 parameters recorded, number of network bursts was the one showing the best correlation with tolerability score (FOB 1 h). The concentration of 3 μM displayed the best predictivity for safe ASOs and for very toxic ASOs in vivo. No false positive was observed at this concentration, so no ASO would be discarded in the in vitro assay while it is safe in vivo.

In vivo acute toxicity of ASO showed a good correlation with desynchronization of the electrical activity of the neural network in vitro. This MEA in vitro assay performed before in vivo safety assessment would allow to divide the number of ASOs to be tested in animals by almost 2.