In May 2020, after dosing 3 DMD boys at the low dose (1 × 1014 vg/kg) and 6 at the high dose (3 × 1014 vg/kg), Pfizer announced that PF-06939926 had a manageable safety profile and showed preliminary effectiveness in terms of dystrophin expression and motor function (Pfizer, 2020b). The gene discussed is DMD; the disease is Duchenne muscular dystrophy.