(nmDMD), according to study results presented at the 2020 CNS-ICNA Conjoint Meeting, held virtually this year. Because so few patients in the study reached one of the negative pulmonary endpoints, longer follow-up will be needed to assess more conclusively the effect of ataluren on pulmonary function, said Francesco Bibbiani, MD, vice president of clinical development at PTC Therapeutics.
Dr. Francesco Bibbiani
DMD is a rare and fatal neuromuscular disorder that causes progressive muscle weakness. Between 10% and 15% of patients with DMD have a nonsense mutation in the DMD gene. This mutation creates a premature stop codon that prevents the translation of a full-length dystrophin protein. Ataluren is designed to promote readthrough of this premature stop codon, thus enabling the production of a full-length dystrophin protein. An oral formulation of the drug has been approved in several European and South American countries.
Comparing treatment and standard of care
Study 019 was a phase 3, multicenter, open-label, long-term safety study of ataluren that enrolled international patients with nmDMD, most of whom had participated previously in a trial of ataluren. Dr. Bibbiani and colleagues conducted a post hoc analysis of Study 019 data to determine whether patients with nmDMD who received ataluren and standard of care for as long as 240 weeks had a different time to loss of ambulation and to decline of pulmonary function, compared with patients who received standard of care alone. Patients who were eligible to participate in Study 019 were male, had nmDMD, and had completed the blinded study drug treatment in a previous PTC-sponsored study. Treatment consisted of two 10-mg/kg doses and one 20-mg/kg dose of ataluren per day.
Dr. Bibbiani and colleagues used participants in the Cooperative International Neuromuscular Research Group Duchenne Natural History Study (CINRG DNHS) as a control group. CINRG DNHS was a prospective, longitudinal study of patients with DMD who received standard of care at 20 centers worldwide from 2006 to 2016. Dr. Bibbiani and colleagues used propensity-score matching to pair participants in this study with participants in Study 019. They matched patients with respect to age at onset of first symptoms, age at initiation of corticosteroid use, duration of deflazacort use, and duration of use of other corticosteroids. These factors are established predictors of disease progression in DMD.
Patients were eligible for inclusion in the post hoc analysis if they had available data for age, loss of ambulation, and the covariates selected for matching. Of 94 Study 019 participants, 60 were eligible for propensity-score matching with participants in CINRG DNHS. Forty-five nonambulatory patients were eligible for matching in the analysis of age at the decline in pulmonary function because data for age at loss of ambulation and for the three pulmonary endpoints measured were available for them. Thus, comparable population sizes were available for each analysis.
Treatment delayed disease milestones
Kaplan–Meier analysis indicated that the median age at various disease milestones was higher among patients who received ataluren and standard of care, compared with those who received standard of care alone. The median age at loss of ambulation was 15.5 years for Study 019 participants and 13.3 years for CINRG DNHS patients. The median age at predicted forced vital capacity (FVC) of less than 60% was 18.1 years for Study 019 participants and 15.8 years for CINRG DNHS participants. The median age at predicted FVC of less than 50% was 19.1 years for Study 019 participants and 17.9 years for CINRG DNHS participants. Finally, the median age at FVC of less than 1 L was not calculable for Study 019 participants and 23.8 years for CINRG DNHS participants.
The Study 019 and CINRG DNHS study groups are sponsored by PTC Therapeutics, which developed ataluren. Dr. Bibbiani is an employee of PTC Therapeutics.
SOURCE: McDonald C, et al. CNS-ICNA 2020. Abstract PL69.