Mechanism of Action Study for Psoriasis

The objective of this study is to compare the mechanism of action between adalimumab and methotrexate in subjects with psoriasis.

Both methotrexate and adalimumab are FDA-approved drugs for the treatment of moderate to severe psoriasis. The two treatments, methotrexate and adalimumab, both show efficacy for psoriasis, however their profiles differ. In the CHAMPION Study, more adalimumab-treated, moderate to severe psoriasis patients achieved a PASI 75 after 16 weeks compared to those treated with methotrexate (80% vs. 36%). The reason for this difference is poorly understood. No direct comparative mechanism of action studies in psoriasis patients between methotrexate and adalimumab (or any tumor necrosis factor blocker) has been reported. With etanercept, another tumor necrosis factor blocker, the in vivo mechanism has been studied with some scientific rigor. These studies demonstrate that etanercept down regulates multiple pro-inflammatory pathways (as shown in Table 1 of the protocol). To date, there are no similar studies with adalimumab or methotrexate. In order to understand the molecular and cellular basis for the differential clinical efficacy of adalimumab and methotrexate, it is essential to compare their mechanisms of action in psoriatic plaques. Biopsies will be performed, and we will study biomarkers in this proposal with immunohistochemistry, real-time polymerase chain reaction, and gene arrays.