A Study to Evaluate the Efficacy and Safety of DC-806 in Participants With Moderate to Severe Plaque Psoriasis

Key Inclusion Criteria:

• Male or female, 18 to 70 years of age

• Body mass index (BMI) of 18 to 40 kg/m2

• All of the following psoriasis criteria:

• Clinical diagnosis of plaque psoriasis for ≥6 months before the Baseline visit

• Stable moderate to severe chronic plaque psoriasis, defined as ≥10% BSApsoriasis involvement, sPGA score of ≥3, and PASI score ≥12 at the Screeningand Baseline visits

• Candidate for phototherapy or systemic therapy, as assessed by the Investigator

• Women of childbearing potential (WOCBP) and men who are sexually active with WOCBPmust be willing to use a highly effective method of contraception during the studyand for ≥30 days after the last dose of study drug

• Willing to discontinue topical and/or systemic therapies for psoriasis before thefirst dose of study drug

Key Exclusion Criteria:

• Have had a clinically significant flare of psoriasis during the 12 weeks before theBaseline visit, as assessed by the Investigator

• History of erythrodermic psoriasis, generalized or localized pustular psoriasis,predominantly guttate psoriasis, medication-induced or medication-exacerbatedpsoriasis

• History of chronic infections including human immunodeficiency virus (HIV) or viralhepatitis (hepatitis B virus [HBV], hepatitis C virus [HCV])

• History of active tuberculosis (TB)

• History or evidence of active infection (including but not limited to coronavirusdisease 2019 [COVID-19] infection) and/or febrile illness within 7 days, seriousinfections leading to hospitalization and intravenous antibiotic treatment within 90days, or serious infection requiring antibiotic treatment within 30 days before thefirst dose of study drug

• History of malignancy or lymphoproliferative disease except resected cutaneoussquamous cell or basal cell carcinoma that has been treated without recurrence

• Presence of active suicidal ideation, or positive suicide behavior using the "Baseline/Screening" version of the Columbia Suicide Severity Rating Scale (C-SSRS)and with either of the following criteria:

• History of suicide attempt (including an actual attempt, interrupted attempt,or aborted attempt) within 5 years before the Screening visit

• Suicidal ideation in the past month before the Screening visit as indicated bya positive response ("Yes") to either Question 4 or Question 5 of the "Baseline/Screening" version of the C-SSRS

• Participant has experienced primary failure (no response at approved doses after ≥3months of therapy) to one or more therapeutic agents targeted to IL-17 (includingbut not limited to secukinumab, ixekizumab, brodalumab, bimekizumab)

• Systemic use of known strong and moderate cytochrome P450 (CYP)3A4 inhibitors orstrong CYP3A4 inducers from Screening through the end of the study

• A 12-lead electrocardiogram (ECG) at Screening that demonstrates clinicallysignificant abnormalities or criteria associated with QT interval abnormalitiesincluding prolongation of QT interval corrected for heart rate using Fridericia'sformula (QTcF) (>500 msec)

• Laboratory values meeting the following criteria within the screening period beforethe first dose of study drug:

• Serum aspartate transaminase ≥2× upper limit of normal (ULN)

• Serum alanine transaminase ≥2×ULN

• Serum total, direct, or indirect bilirubin ≥2.0 mg/dL; except for participantswith isolated elevation of indirect bilirubin relating to a confirmed diagnosisof Gilbert syndrome

• Estimated glomerular filtration rate (GFR) by simplified 4-variableModification of Diet in Renal Disease (MDRD) formula <45 mL/min/1.73m2

• Total white blood cell count <3000/μL

• Absolute neutrophil count <1500/μL

• Platelet count <100,000/μL

• Hemoglobin <9 g/dL

• In the opinion of the Investigator or Sponsor, have any uncontrolled clinicallysignificant laboratory abnormality that would affect interpretation of study data orthe participant's enrollment in the study