I found it also interesting to note in PF-06939926 similar...

I found it also interesting to note in PF-06939926 similar muscle fat benefit via MRI results as ATL-1102, leading to post-trial enthusiasm and potentially phase quickening aspect, at High Dose (low dose no effect), whereas ATL-1102 had beneficial muscle fat ratio at what we would all consider low dose, and based on other ATL-1102 trails higher doses are well tolerated. So, extrapolate from that what you will.

PF-06939926 "A second exploratory analysis using MRI showed a reduction in fat fraction in the thighs of boys treated with the high dose at 12 months post-treatment. Boys with DMD typically exhibit a progressive loss of contractile or lean muscle and replacement with fat and fibrotic tissue. In this study, a reduction in fat fraction was observed in boys from the high dose-treated cohort when compared to an external placebo group, suggesting that gene therapy may have improved muscle fiber health and quality in these boys. No reduction in fat fraction was seen in the low dose group."