I saw this news article (here is the article about it in a medical journal) and began to wonder if the cure for gray hair is on the way. Those immunotherapy drugs can restore hair color only in people with cancer?, And what about the safety? It is dangerous to healthy people more than to cancer patients?. The scientists now need to investigate the process behind the repigmentation of white hairs in those cases and develop a whole new drug for this?, or simply look for a way to make the existing drugs safer for treatments for white hairs?.
I haven't read the article, only the abstract, but what it's saying is that, for people with grey or white hair, darkening of hair color is an indication that anti–PD-1/anti–PD-L1 treatment for lung cancer is working. This is almost entirely unrelated to reversing age-related hair depigmentation.
(As a side note, I consider the Daily Mail to be comparable to The Onion when it comes to accuracy in medical reporting.)