COQ4 and COQ8A Primary Deficiencies: A Review of Proposed Therapeutic Strategies

In this article we have reviewed potential therapeutic strategies relating to two of the primary coenzyme Q10 (CoQ10) deficiencies, COQ4 and COQ8A; these disorders have been grouped together because of their complimentary roles in stabilising the CoQ10 enzyme complex, Complex Q, as well as the difficulty in treating either of these disorders using conventional oral supplementation, as exemplified by two previously unreported case histories. Alternative strategies reviewed include methods to potentially improve blood-brain barrier access, including the identification of suitable inhibitors or activators of LRP1 or SRB1 transporters respectively. Other potential therapeutic strategies include the potential stabilisation of Complex Q using agents such as cardiolipin, targeted gene therapy using CRISPR/Cas9 gene-editing or AAV vector gene delivery, or mitochondrial transplantation. All of the strategies outlined above are at an early preclinical stage with regard to their potential application in primary CoQ10 deficiency, and remain areas for ongoing research.