• Improvement in appearance of the control fingernail, improvement of the target fingernail using mNAPSI (a modification of the Nail Psoriasis Severity Index), and comparison of improvement of mNAPSI of the target and control fingernails. [ Time Frame: Monthly ] [ Designated as safety issue: No ]
• Information on the relative changes in nail psoriasis severity of the other affected fingernails will be collected. [ Time Frame: Monthly ] [ Designated as safety issue: No ]
• Comparison of nail growth of the target and control fingernails as determined from nail notch movement measured on nail photographs will be performed. [ Time Frame: Monthly ] [ Designated as safety issue: No ]
• Assess safety, i.e., the frequency and severity of adverse events associated with MQX-5902, MQX-5904 and MQX-5906 in the treatment of patients with fingernail psoriasis. [ Time Frame: Monthly ] [ Designated as safety issue: Yes ]

The purpose of this clinical study is to compare the efficacy and safety of three concentrations of topical methotrexate for the treatment of fingernail psoriasis.

The purpose of this clinical study is to compare, in a controlled fashion, the response to three concentrations of methotrexate in novel topical formulations in the treatment of subjects with psoriasis of the fingernails. Such a determination will be used as the basis for evidence of efficacy and safety of these formulations as a therapeutic treatment for fingernail psoriasis.

Inclusion Criteria:

• Diagnosed moderate fingernail psoriasis of at least two fingernails.
• Stable and unchanged psoriasis therapies for 2 months and must not have received methotrexate for 3 months prior to screening.
• Female patients who are not 5 years post menopausal or surgically sterile must use appropriate birth control for specified time periods and have negative pregnancy tests.

Exclusion Criteria:

• Target or control fingernails that are thicker than 2mm, abnormal or infected (bacterial or fungal).
• Patients with immunosuppression, HIV, or neuropathies of the hand.
• Use of any methotrexate preparation, any topical anti-psoriatic medications or ultraviolet treatment within 2 months of study visit 1.
• Use of more that one 2-week course of oral corticosteroid therapy or one injection during 3 months prior to the screening visit.
• Use of manicures or cosmetic nail products during and within 7 days of the start of treatment.
• Use of any drug known to have potential for toxicity to a major organ during and within 90 days prior to the start of treatment.
• Patients who are nursing, pregnant or plan to become pregnant or father a child within the study time frame including within three months of the last dose of study medication.