Yes, MIFEPRISTONE is a Scrabble word!

Letter values in Scrabble US: M 3, I 1, F 4, E 1, P 3, R 1, I 1, S 1, T 1, O 1, N 1, E 1.

Is it a valid word?

MIFEPRISTONE is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

an abortion-inducing drug (trade name RU_486) developed in France; when taken during the first five weeks of pregnancy it blocks the action of progesterone so that the uterus sloughs off the embryo

Also: abortion pill, ru 486.