"In the conduct of clinical trials for pharmaceutical research, access to investigational medicines following clinical trials is often necessary for the continued health and well-being of the trial participants; it is an ethical obligation under some circumstances, as outlined in the Declaration of Helsinki 2013 Article 34." From Cambridge Quarterly of Healthcare Ethics, Jan/19. 

I'm no expert but it would appear to me that it is just conforming to this and gives the opportunity to collect more data. Nothing would preclude them from doing it again past 2022 either.