This is a randomized, double-blinded, placebo-controlled, Phase 3 study to evaluate the efficacy and safety of tildrakizumab compared to placebo in anti-TNF naïve subjects with active PsA .

Inclusion Criteria:

1. Subject has provided written informed consent.
2. Subject is ≥ 18 years of age at time of Screening.
3. Subject has a diagnosis of active PsA for at least 6 months before the first administration of the study agent and has active PsA at Screening or Baseline.
4. Rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP Ab) negative.
5. Subjects must have no prior exposure to anti-tumor necrosis factor (anti-TNF) agent(s) use for the treatment of PsO or PsA.

Exclusion Criteria:

1. The subject has a planned surgical intervention between Baseline and the Week 52 evaluation for a pretreatment condition.

2. Subject has an active infection or history of infections as follows:

   • any active infection for which systemic anti-infectives were used within 28 days prior to first IMP dose, with the last dose having been received within 7 days of Screening,
   • a serious infection, defined as requiring hospitalization or intravenous (IV) anti-infectives within 8 weeks prior to the first IMP dose, with the last dose having been received within 7 days of Screening,
   • recurrent or chronic infections, e.g., chronic pyelonephritis, chronic osteomyelitis, bronchiectasis, or other active infection that, in the opinion of the Investigator, might cause this study to be detrimental to the subject.

3. Subject has any concurrent medical condition or uncontrolled, clinically significant systemic disease (e.g., renal failure, heart failure, hypertension, liver disease, diabetes, or anemia) that, in the opinion of the Investigator, could cause this study to be detrimental to the subject.

4. Subject has a known history of infection with hepatitis B, hepatitis C, or human immunodeficiency virus.

5. Subject had myocardial infarction, unstable angina pectoris, or ischemic stroke within the past 6 months prior to the first IMP dose.

6. Subject has any active malignancy, including evidence of cutaneous basal or squamous cell carcinoma or melanoma.

7. Subjects with a history of alcohol or drug abuse in the previous 2 years.

8. Female subjects of childbearing potential who do not agree to abstain from heterosexual activity or practice a dual method of contraception, for example, a combination of the following: (1) oral contraceptive, depo progesterone, or intrauterine device; and (2) a barrier method (condom or diaphragm). Male subjects with female partners of childbearing potential who are not using birth control as described above must use a barrier method of contraception (e.g., condom) if not surgically sterile (i.e., vasectomy). Contraceptive methods must be practiced upon signing the Informed Consent and through 24 weeks after the last dose of IMP. If a subject discontinues prematurely, the contraceptive method must be practiced for 17 weeks following final administration of IMP. A follicle-stimulating hormone (FSH) test should be performed to confirm menopause (per reference values of the laboratory) for those women with no menses for less than 1 year.

9. Subject currently enrolled in another investigational device/procedure or drug study, or Baseline of this study is less than 30 days or 5 half-lives (whichever is longer) since ending another investigational device/procedure or drug study(s), or receiving other investigational agent(s).

10. Subject previously has been enrolled (randomized) in this study.

11. Subject has any kind of disorder that, in the opinion of the Investigator, may compromise the ability of the subject to give written informed consent and/or to comply with all required study procedures.

12. Donation or loss of 400 milliliter (mL) or more of blood within 8 weeks before first dose of IMP.

13. Subjects who have been placed in an institution on official or judicial orders.

14. Subjects who are related to or dependent on the Investigator, Sponsor, or study site such that a conflict of interest could arise.