The purpose of this study is to evaluate the safety and effectiveness of oral administration of four dose regimens of JNJ-26113100 prepared in a capsule formulation administered for 6 weeks in the treatment of adult atopic dermatitis that is moderate in severity.

A multi-center, exploratory study will be done to evaluate the safety and effectiveness of JNJ-26113100 in the treatment of adult atopic dermatitis, including its effect on biomarkers. Approximately 140 adults with atopic dermatitis will take part in the study. After screening, they will be randomly (patients are assigned different treatments based on chance) assigned to one of four treatment groups in a sequential fashion to receive JNJ-26113100 50 mg once daily, 100 mg once daily, 100 mg twice daily or 250 mg twice daily or matching placebo. Study medication will be dispensed in a blinded fashion. The patient, the study doctor and the study sponsor will not know the treatment to which the patient has been assigned. The first dose will be administered in the clinic. Depending on the treatment group, patients will take medication either once or twice daily for six weeks. Study visits will be conducted at the end of Week 1, Week 2, Week 3, Week 4, Week 5 and Week 6. A study termination visit will be conducted at the end of Week 8. The patient's skin will be assessed at following visits: screening, randomization, week 1, week 2, week 3, week 4, week 5, week 6 and at study termination. Medical history, physical examination, blood pressure, heart rate, respiratory rate, temperature and electrocardiograms will be checked periodically during the study. Blood and urine samples will be collected for standard safety laboratory tests, to measure the level of drug and to learn about the effect of the drug on markers of inflammation. Two skin biopsies from atopic dermatitis lesions will be collected during the study to assess changes in the inflammatory disease state. Patients developing flares of their disease may be treated with triamcinolone acetonide 0.1% ointment twice daily for up to 7 days. Patients will receive JNJ-26113100 50 mg once daily, 100 mg once daily, 100 mg twice daily or 250 mg twice daily or matching placebo capsules for 6 weeks.

Inclusion Criteria:

• Adults with atopic dermatitis involving >= 10% body surface area
• in good general health (well-controlled asthma, allergic rhinitis and food allergies will be allowed)
• willing to use highly effective birth control methods throughout the study

Exclusion Criteria:

• Use of specific systemic medications or phototherapy for atopic dermatitis within four weeks of dosing
• use of specific topical medications for atopic dermatitis within one week of dosing
• frequent acetaminophen or ibuprofen use
• active infection