A Study to Assess the Clinical Effects of Navarixin in Participants With Psoriasis (MK-7123-009)

Inclusion Criteria:

• Body Mass Index (BMI) 19 to 34, BMI = weight (kg)/height (m^2).
• Must have a diagnosis of psoriasis vulgaris (PASI >8) present for at least 1 year. Participants with an on-therapy PASI <=8 at Screening may be considered for inclusion. Participants must be discussed with the Sponsor prior to enrollment and the subject must have indicated that they are not satisfied with current therapy. To be included, participants must have a PASI >8 following washout of their current psoriasis therapy.
• Target lesion selected must be located on the head, trunk, arms or legs and be at least 10 cm^2 in size. The lesion's total numerical ratings for erythema, infiltration, and desquamation must be at least 6 out of the possible 12. Severity score for desquamation must be at least 2.
• Vital sign measurements (taken after ~3 minutes in a supine position) must be within the following ranges: oral body temperature between 35.0°C to 37.5°C; systolic blood pressure, 90 to 160 mm Hg; diastolic blood pressure, 45 to 90 mm Hg; pulse rate, 40 to 100 bpm.
• Have stable disease (ie, off treatment PASI during Screening period and Baseline PASI should not differ by more than 40%).
• Clinical laboratory tests (CBC, blood chemistries, and urinalysis) must be within normal limits or clinically acceptable to the investigator/sponsor. Participants must have a neutrophil count of at least 2 x 10^9/L to be included.
• Free of any clinically significant disease (other than psoriasis).
• Willing to give written informed consent and able to adhere to dose and visit schedules.
• For female participants: Negative serum pregnancy test (beta-hCG) and urine pregnancy test. Agree to use medically accepted methods of contraception during and for an appropriate pre-study period while receiving protocol specified medication, and for 1 month after stopping medication. Female participants of non-childbearing potential must be surgically sterilized or be postmenopausal.
• Male subject must agree to use an adequate form of contraception for the duration of the study.
• At Screening, ECG conduction intervals must be within gender specific normal range (ie, QTc for males <430 msec and females <450 msec) or if not within the normal range, the values must be considered clinically insignificant by the investigator and sponsor.

Exclusion Criteria:

• Female participants who are pregnant, intend to become pregnant (within 3 months of ending the study), or are breastfeeding.
• Participants who, in the opinion of the investigator, will not be able to participate optimally in the study.
• Any surgical or medical condition which might significantly alter the absorption, distribution, metabolism or excretion of any drug.
• History of any infectious disease within 4 weeks prior to drug administration and/or are positive for hepatitis B surface antigen, hepatitis C antibodies or human immunodeficiency virus (HIV).
• Immunocompromised participants.
• Positive screen for drugs with a high potential for abuse or have a history of drug or alcohol abuse in the past 2 years.
• History of mental instability or who have been treated for mood disorders.
• Donated blood in the past 60 days.
• Previous treatment with study medication.
• Currently participating in another clinical study or have participated in a clinical study within 30 days.
• Part of the study staff personnel or family members of the study staff personnel.
• Demonstrated clinically significant (requiring intervention) allergic reactions or who are known to be allergic to components of local anesthetics.