O049 Maintaining long-term functional optogenetic stimulation for OSA therapy in a rodent model

Abstract Introduction Obstructive sleep apnoea (OSA) patients are often sub-optimally treated due to poor tolerance and/or incomplete responses to established therapies. Our novel therapy sensitises upper airway muscles to light (optogenetics) and allows their activation during sleep. Previous work has demonstrated that an adeno-associated viral vector (AAV) driven by a muscle-specific promoter produces strong expression of light-sensitive proteins (opsins) in the tongue, and strong light-evoked muscle activation 3-weeks after administration. Here we determine whether this response persists over 12-weeks, and whether immunosuppression is required. Methods Rats received intralingual injections of the AAV. After 12-weeks, opsin expression in the tongue was quantified via confocal imaging. Light-evoked muscle activation was recorded in a model of sleep-associated muscle hypotonia. This was repeated in three additional groups of animals. Group 1 received rapamycin (4 mg/kg/day) and cyclosporin (5 mg/kg/day), group 2 received prednisolone (1 mg/kg/day, tapering 10%/week from week 9), and group 3 received daily vehicle intrapleural injections. Results Without immunosuppression, opsin expression decreased ~4-fold in the tongue between 3- and 12-weeks post-AAV administration (two-way RM ANOVA, p=0.01). Subsequently, light-evoked muscle-activation also declined (linear mixed model, time*stimulation, p<0.001). With rapamycin/cyclosporin administration, light stimulation at 12-weeks was able to increase muscle-activation ~2-fold (p<0.001). Prednisolone and vehicle administration did not facilitate light-evoked muscle-activation at 12-weeks (p>0.05; LMM, group*stimulation p<0.001). Discussion Rapamycin/cyclosporin administration allows persistent opsin expression and light-evoked muscle activation. As all existing clinically approved AAV-mediated gene therapies require initial immune suppression, this requirement is not a barrier to clinical translation of an optogenetics-based therapy for OSA.