Proof-of-concept Study of Forward Pharma (FP)187 in Patients With Mild/Moderate Psoriatic Arthritis

Inclusion Criteria: * documented clinical diagnosis of mild to moderate psoriatic arthritis of at least 3 months * active psoriatic arthritis with at least 2 tender and 2 swollen joints * signed informed consent * willingness and ability to comply with study procedures * besides psoriatic arthritis, patient must be in good general health in the opinion of the investigator, as determined by medical history, physical examination, vital signs, electrocardiography and clinical laboratory parameters * if patients are using methotrexate, they should be on a stable dosis of not more the 20mg per week for at least 90 days prior to study entrance and should present no serious toxic side effects attributable to methotrexate * female of childbearing age must be either surgically sterile or use a highly effective medically accepted contraceptive method Exclusion Criteria: * female patients who are pregnant of breast-feeding or planning to become pregnant during the entire trial period * male patients planning pregnancy with their partner during the entire trial period, or practicing unprotected sexual relationship during the entire trial period * known allergy to any of the constituents of the products being tested * known immunosuppressive diseases (e.g. HIV, AIDS) * known history of latent or active granulomatous infection including tuberculosis, histoplasmosis or coccidioidomycosis * presence of another inflammatory disease including but not limited to rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematous or Lyme disease * presence of chronic widespread pain syndrome * patients with pustular forms of psoriasis, erythrodermic or guttate psoriasis * patients with another non-psoriatic arthropathy (e.g. osteoarthritis) * presence of another serious or progressive disease including skin malignancy * presence or history of any malignancy (except for basal cell carcinoma, squamous cell carcinoma in situ of the skin treated with no evidence of recurrence within 5 years, or cervix cancer in situ treated with no evidence of recurrence.) * use at any time of an biological Disease Modifying Antirheumatic Drug (bDMARD) such as etanercept, adalimumab, golimumab, certolizumab pegol or infliximab * corticosteroid injections within 12 weeks * use of any dimethyl fumarate (DMF) containing product within 12 weeks * use of any retinoid treatments, other immunosuppressive treatments, cytostatics or drugs with known harmful effects on the kidneys within the last 3 months * use of cyclosporine, corticosteroids or psoralen + UVA (PUVA) treatment within 4 weeks * ongoing stomach or intestinal problems (e.g. gastritis or peptic ulcer) * Aspartate transaminase (AST) or Alanine transaminase (ALT) \> 2x upper normal normal limit (UNL) or Gamma Glutamyl Transferase (gamma-GT) results \>2.5 UNL * estimated creatinine clearance (Cockcroft-Gault) \< 60ml/min * leucopenia (leucocyte count \< 3.5/nl), eosinophilia (\>750 / micro l) or lymphocytopenia (\<1.02 / nl) * protein detected by urine stick test * participation in another clinical trial during the last 2 months or participation in a trial with another psoriatic arthritis treatment within 6 months