Therefore, its known narrative elements are not a part of the Doctor Who universe. It may have been the basis for a similar story in another medium, however — and that story may indeed be a part of the DWU.
Alixion was a story that was to have been a part of Season 27 had Doctor Who continued to be produced beyond Survival. It would have been written by Robin Mukherjee.
Alixion was a three-part story that had been commissioned for Season 26, but was not produced due to the relative greenness of the writer in terms of television drama writing at the time.
DWM 255 depicted an image of Richard Griffiths in the role of the Doctor, which would have been either in this story or the one that proceeded.