Inclusion Criteria:

• Able and willing to provide written informed consent to participate in the study
• Be male or female aged 18 to 80 years (inclusive)
• Have a diagnosis of clinically confirmed, stable (without recent documented flare within 30 days prior to the Screening Visit), plaque-type psoriasis for at least 6 months involving ≥10% of body surface area
• Have a baseline PASI of ≥10
• Be a candidate for systemic psoriasis therapy, in the opinion of the investigator
• If a female subject of child-bearing potential, be willing to use reliable contraception for the duration of the study, through the 30 day safety follow up telephone call
• Be willing and able to comply with the protocol for the duration of the study

Exclusion Criteria:

• Has received systemic non-biologic psoriasis therapy or PUVA phototherapy within 4 weeks prior to the Screening Visit, or had topical psoriasis treatment or UVB phototherapy within 2 weeks prior to the Screening Visit
• Has received previous treatment with biologic agents within 5 drug half-lives (or within 3 months if half-life is unknown) prior to the first dose of SRT2104
• Has received a live vaccination within 4 weeks prior to the Screening Visit or intends to have a live vaccination during the course of the study
• Use of any other non-psoriatic prescription drug therapy, with the exception of any prescription medication administered at a stable dose for at least 6 weeks prior to the Screening Visit; however, the administration of proton pump inhibitors during the study dosing period is prohibited
• Use of any dietary or herbal supplements, with the exception of those administered at a stable dose for at least 6 weeks prior to the Screening Visit
• Has received any investigational drug or experimental procedure within 30 days prior to the first dose of SRT2104
• Has an active infection (e.g., sepsis, pneumonia, abscess, etc.) or be at high risk of developing an infection, in the opinion of the investigator, prior to the first dose of SRT2104
• Has a history of a positive tuberculosis test or a positive tuberculosis test at the Screening Visit that cannot be attributed to a prior BCG inoculation
• Has a positive pre-study Hepatitis B surface antigen or positive Hepatitis C antibody result within 3 months of the Screening Visit
• Has a positive test for HIV antibody
• Has an abnormal chest x-ray at the Screening Visit which, in the opinion of the investigator, would preclude entry into the trial
• Has a 12-lead electrocardiogram (ECG) with changes considered to be clinically significant on medical review including prolonged QTc intervals as defined below:
• QTcB ≥450 msec (based on single or average QTc value of triplicate ECGs obtained over a brief period)
• QTcB ≥480 msec in subjects with Bundle Branch Block
• Has renal or liver impairment, defined as:
• Serum creatinine level of ≥ 1.4 mg/dL for females and ≥ 1.5 mg/dL for males
• AST and ALT ≥ 2xULN or
• Alkaline phosphatase and bilirubin > 1.5xULN (an isolated bilirubin >1.5xULN is acceptable if bilirubin is fractionated and direct bilirubin is <35%)
• Has active neoplastic disease or history of neoplastic disease within 5 years of study entry (except for basal or squamous cell carcinoma of the skin, or carcinoma in situ which have been definitively treated with standard of care approaches)
• Is pregnant or breast-feeding. Confirmation that a female subject is not pregnant must be established by negative pregnancy tests at Screening and Day 1
• Has a significant history of alcoholism or drug/chemical abuse, or consumes more than 3 standard units/day of alcohol. A standard unit of alcohol is defined as 250 mL of beer, 25 mL of spirit, or 125 mL of wine
• History of sensitivity to any of the study medications, or components thereof, or a history of drug or other allergy that, in the opinion of the investigator or medical monitor, contraindicates their participation
• Has an acute or chronic illness which, in the opinion of the investigator, could pose a threat or harm to the subject