 In Part 3 of the base study Week 28 to Week 52, participants in Arm A with Psoriasis Area Sensitivity Index of 75 PASI-75 response at Week 28 will be re-randomized to either continue tildrakizumab 200 mg or receive tildrakizumab 100 mg at study Weeks 28, 40, and 52. Participants with PASI-50 response but PASI-75 response will continue to receive tildrakizumab 200 mg every 12 weeks and those participants with PASI-50 response will be discontinued from the study. Participants in Arm B with PASI-75 response at Week 28 will continue to receive tildrakizumab 100 mg every 12 weeks. Those with PASI-50 response but PASI-75 response will be re-randomized to receive continued tildrakizumab 100 mg or tildrakizumab 200 mg every 12 weeks. Participants in Arm B with PASI-50 response will be discontinued from the study. Participants in Arm C will continue to receive treatment every 12 weeks according to their re-randomized treatment assignment. Participants in Arm D that achieve PASI-75 response at Week 28 will be discontinued from the study. Those participants with PASI-75 response at Week 28 will be crossed over to tildrakizumab 200 mg to receive doses at Weeks 32, 36 and 48. 