 In Part 1 of the base study Week 0 to Week 12, participants will be randomized to one of 4 study arms Arm A: tildrakizumab 200 mg matching placebo to etanercept; Arm B: tildrakizumab 100 mg matching placebo to etanercept; Arm C: matching placebo to tildrakizumab matching placebo to etanercept; Arm D: matching placebo to tildrakizumab etanercept 50 mg. 