Figure 5.

Dose-dependent cardiac FXN levels following AAVrh.10hFXN treatment of MCK mice (A, B) and NHPs (C, D) and correlation of these to estimated cardiac FXN levels in FA homozygotes and heterozygotes. (A) Dose-dependent human cardiac FXN levels in MCK mice intravenously administered AAVrh.10hFXN at 1.8 × 10¹¹, 5.7 × 10¹¹, and 1.8 × 10¹² gc/kg (3 male and 3 female/dose, except the highest dose group 4 male/4 female). PBS-administered mice (3 male/3 female) served as negative control. At sacrifice, hFXN levels in the heart were assessed. The AAV-expressed human FXN levels in the treated mouse hearts (left ventricular wall) were measured in triplicate by ELISA and expressed as ng/mg total protein (mean ± SEM) of male and female combined for each dose group. Human FXN levels are shown versus AAVrh.10hFXN dose (log scale). (B) Estimated FXN cardiac levels in FA homozygotes based on the AAVrh.10FXN dose-dependent cardiac levels achieved in the MCK mice. The human FXN levels obtained in the MCK mouse in (A) were combined with the estimated endogenous human heart FXN levels in FA homozygotes (Fig. 1). The vector-derived hFXN levels observed in MCK mice (red bars) were added to the estimated endogenous cardiac FXN levels of 9.4 ng/mg estimated in FA homozygotes (blue bars), which allows for the estimation of the FXN levels obtained from a given dose of AAVrh.10hFXN. The gray shading represents the FXN level range estimated in FA carriers (heterozygotes). (C) NHP cardiac FXN levels following dose-dependent administration of AAVrh.10hFXN. Shown is the average of FXN protein levels in the heart (5 samples/NHP) assessed by ELISA of n = 4 (2 male, 2 female) NHPs administered 5.7 × 10¹¹ gc/kg and n = 4 (2 male, 2 female) administered 1.8 × 10¹² gc/kg. Data shown as mean ± SEM of 5 heart regions combined, for all animals for each dose group, with the mean values above each bar. The human FXN ELISA assay detects endogenous FXN in the NHP heart. The baseline NHP FXN levels were subtracted (using PBS controls levels, mean 45.3 ng/mg obtained from 1 male/1 female). (D) Extrapolation from the NHP data of the dose-dependent levels of FXN that would be achieved in the heart of the average FA patient following administration of AAVrh.10hFXN. The mean human FXN levels quantified in the treated NHPs (C) added to the estimated human FA homozygote data (Fig. 1B) allow for the estimation of the theoretical efficacy of the AAVrh.10hFXN vector dosing. The vector-derived hFXN levels observed in NHP (red bars) were added to the hFXN level baseline of 9.4 ng/mg estimated in FA homozygotes (blue bars). The gray shading represents the FXN level range seen in FA carriers (heterozygotes). NHP, nonhuman primate.