I was on Entyvio (Vedolizimab) for a year or so for UC. It is an experimental drug here in Oz (so it was part of a trial, not blind so 100% guaranteed of getting the drug). Within two weeks of the first infusion I was in complete remission. This was fantastic. 12 Months later I had a colonoscopy which further confirmed the remission. Two weeks after that saw signs of blood and mucous and within a month UC was back. I was told there were patients who had been on it for several years and maintained remission. I was also told that, for patients where it worked quickly, it seemed to lose its efficacy after a year or so (me I guess). So nothing working and essentially now pan-colitis after only being 25cm-35cm for many years previously. Colon removed 9 July 2014, takedown 15 October 2014.
I do not know if the colonoscopy unsettled things, my GI says no, but appears to be too much of a coincidence (conspiracy theory).
Note also that is not guaranteed to work, I believe there is something like a 65% (don't quote me) success rate and much better than Humira. Regardless, when it was working, it was working 100% and there were no side effects. Some of the major side effects of the other biologicals are not evident in Vedolizimab so I wouldn't worry about using it (not a medical opinion).
Good luck with the treatment.