Will my client [name withheld] be able to tolerate Entyvio, as her doctors feel this is the best choice to bring some relief for her because she has not tolerated any other medication? Would azathioprine be as good and also safer from potential downside consequences, or would it have more side effects?

She will tolerate the Entyvio and this will be a blessing to achieve remission in her case. The use of azathioprine can be considered as a follow-up if there is recurrence, but it may be manageable with Entyvio entirely. Combination therapy can be used if that proves to not work out or an alteration of the two medications is another strategy that can work just as well. This is little appreciated by the medical community. They are often switching medications, but usually when there is a significant shortfall in efficacy and less so when there is a proven beneficial agent. There may be a necessity for withdrawing treatment if side effects begin to develop, but there will be little appreciation of what can be done with rotating different agents to, in effect, give a drug holiday both in terms of the chemical toxicity as well as the negative side effects due to the mode of action on the immune system in this case. It is unlikely her doctors will be enlightened enough to consider such a regimen, but at least you can learn something from this and have this in your thinking as it may come in handy if there is an opportunity to be an advocate.