Crohn's and UC are treated with infliximab, among a lot of other drugs like corticosteroids and methotrexate, but the results vary from patient-to-patient and the improvement is often transitory.
Yes. http://www.remicade-crohns.com/ is approved for Crohns but it is also approved for RA and I can't find a breakdown of sales. I suspect most of the $1 Billion plus sales it achieved is in RA.