If an ulcerative colitis patient has a 90 percent response to a biologic or small molecule after over 12 months, would you consider switching medication to a different class in hopes of getting a complete response, versus trying adjunctive therapy?

I am not sure what you mean by “90%” response. Is that clinical, laboratory, or endoscopic? Perfection is the enemy of good, so you'd better have a compelling reason to make a patient add another therapy.

In this situation, it partly depends on how significant that remaining 10% of inflammation is to the patient.

If we are talking about 90% endoscopic response (for instance, just minimal inflammation remaining in the rectosigmoid colon), I may not make any changes based on this alone, but would have ...

A 90% response is quite good. If the patient is doing well clinically and other objective evidence confirms the 90% response (C-reactive protein [CRP] decreased, fecal markers significantly improved, or colonoscopy or imaging shows mostly healed), then I would continue current therapy and would not ...