Ridley Scott has morphed his planned Alien prequel into a whole new ‘Prometheus' IP:

While Alien was indeed the jumping off point for this project, out of the creative process evolved a new, grand mythology and universe in which this original story takes place. The keen fan will recognize strands of Alien’s DNA, so to speak, but the ideas tackled in this film are unique, large and provocative.

My first thought was “damn”, but on reflection the fact that he is able to change it so easily means that the “Alien-ness” of the planned movie must have been photoshopped in just to sell the script to the suits. So this is probably a good thing - and potentially a better movie will come out of the change.