I'm take lisinopril and coreg to maintain my heart. I also use a sleep apnea machine when I sleep in order to maintain my respitory muscles. I also have an internal cardiac defibrillator (icd).

I'm doing okay, I am in a wheelchair though, haha. I went into one around the time I was in 4th grade. I'm here to let everyone know that life still can be good in this situation even though it can be quite difficult.

Hey there!
Sorry for the lat response, I don't know much about steroid treatment as I have not had any during the course of my disease so I don't know a lot about the side affects. It might be a good idea to do some research and weigh out the pros and cons for steroid therapy. I do know from experience that consistent physical therapy is important because it will maintain range of motion and help slow the process of phibrosis.
Also again, I'm sorry that I'm not familiar with that drug on trial and I don't know that it will completely cure dmd, it doesn't seem that medicine has arrived at a full cure but I can tell you that there have been huge breakthroughs and that diseases like this will be cured some day and it's quite possible that this could happen in your nephews lifetime.
Also something else that is of great importance is that your nephew should be seeing a cardiologist and a pulmonologist who have a background in treating patients with dmd as the heart and respiratory muscles are the very most important muscles and the treatment to maintain them will greatly extend your nephews life span. Men with dmd are now able to live well into their 40's because of all of the treatments that are available today. I hope this helps!