The trial was prematurely terminated on 01April2014 due to safety concerns.

PF-05180999 is a phosphodiesterase-2 inhibitor that is hypothesized to be able to reduce vascular permeability. The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and effects on histamine-induced wheal of single doses of PF-05180999 in healthy adult subjects. Histamine-induced wheals are biomarkers of vascular permeability.

Inclusion Criteria:

• Healthy male subjects between the ages of 18 and 55 years
• No history of clinically-relevant atopic or dermatological disease
• Positive reaction to intradermal injection of histamine

Exclusion Criteria:

• Subjects with screening laboratory test results that deviate from the upper and/or lower limits of the reference or acceptable range. The exception is that all liver function tests must not exceed the upper limit of normal.
• Subjects with evidence of, or history of, hepatic disorder, including acute or chronic hepatitis B or hepatitis C
• Intolerance to intradermal histamine injection.
• Subjects with dark skin (Part B only).