Reverse transcriptase inhibitors in Aicardi-Goutières syndrome: A crossover clinical trial.

Aim: To extend the findings of a previous clinical trial suggesting combined abacavir (ABC), lamivudine (3TC), and zidovudine (AZT) reduces type I interferon (IFN) signalling in Aicardi-Goutières syndrome (AGS).

Method: This was an open label, non-placebo-controlled phase II clinical trial (NCT04731103) in patients less than 16 years with any of five AGS genotypes. The effect of ABC or 3TC individually, or of combined ABC + 3TC + AZT, on IFN-stimulated gene (ISG) expression (primary outcome) and IFN-alpha protein (secondary outcome) in blood was assessed.

Results: Thirteen patients were recruited. Compliance was poor in the ABC + 3TC + AZT arm. No statistically significant effects were observed with ABC or 3TC, or with ABC + 3TC + AZT over 6 weeks. A statistically significant reduction of ISG expression was recorded after 3 weeks of ABC + 3TC + AZT, which was not mirrored by changes in IFN-alpha protein.

Interpretation: There is insufficient evidence that ABC or 3TC is either effective or ineffective in reducing type I IFN signalling in AGS over 6 weeks. The effect of ABC + 3TC + AZT at 3 weeks supports data from a previous clinical trial of the effect of ABC + 3TC + AZT in reducing type I IFN signalling, although there was insufficient evidence of an effect at 6 weeks. Time to local research and development (R&D) approval, and to sponsor authorization after R&D approval, severely limited patient recruitment.