Men or women aged 18 years or older
Patients with moderate‐to‐severe chronic plaque psoriasis with or without psoriatic arthritis AND who had started any first line of anti‐TNF alpha according to the labelling of these drugs BEFORE the study (i.e. the study will be restricted to anti‐TNF alpha‐naïve patients (first course). Patients who have been previously treated with any other non‐anti‐TNFA alpha biopharmaceutical (ustekinumab or anti IL17‐ secukinumab, ixekizumab, brodalumab) as a first line of biotherapy for psoriasis could be enrolled) after a washout period of at least 5 half‐lifetimes of the drug i.e. 16 weeks before inclusion
No significant anomalies from a blood sampling performed within 15 days before patient selection that could lead to MTX contraindication
Patients with an EARLY start of anti‐TNF alpha, i.e. within the 7 days preceding the first study drug (methotrexate or placebo) administration
Men or women agreeing to use a reliable method of birth control during the study. Men agreeing to use a reliable method of birth control during the study i.e. preservative and for at least 6 months following the last dose of investigational product, the patient's partner treated by methotrexate must be notified of the teratogenic risk of methotrexate and should be under effective contraception throughout the study. Female patients are women of childbearing potential who are negatively tested for pregnancy and agree to use a reliable method of birth control (every month) or remain abstinent during the study and for at least 6 months following the last dose of investigational product, whichever is longer. Methods of contraception considered acceptable include oral contraceptives, contraceptive patch, intrauterine device, vaginal ring.
Negative serum b‐Human Chorionic Gonadotrophin (B‐HCG) test at screening, or women of non‐childbearing potential, defined as: women who have had a surgical sterilisation (hysterectomy, bilateral oophorectomy, or tubal ligation) Or women ≥ 60 years of age or women ≥ 40 and < 60 years who have had a cessation of menses for ≥ 12 months and a follicle stimulating hormone (FSH) test confirming non‐childbearing potential
Patients with isolated pustular, erythrodermic and or guttate forms of psoriasis
Patients with prior use of any anti TNF alpha
Patients who have known active liver disease (with the exception of a simple liver steatosis, transaminases and/or alkaline phosphatases > 2 ULM ) or history of liver disease in the past 2 years, whatever the related diagnosis but which could interfere with MTX safety and according to the summary of the SmPC
Intake of restricted medications (cf section VIII.5.) or other drugs considered likely to interfere with the safe conduct of the study, as assessed by the investigator and according to the Summary of the Product Characteristics (SmPC), including any drug intakes that could interfere with methotrexate metabolism or that could enhance liver and/or haematologic toxicity and according to the SmPC
Patient with evidence or positive test for HIV, Hepatitis C virus, Hepatitis B virus (patients who are negative for hepatitis B surface antigen but positive for anti‐hepatitis B anti body (HBsAb+ and HBcAb+) and negative for serum HBV DNA may participate in the study
High alcohol intake, defined as more than 60 g of daily intake (approx daily intake of 0.5 l of wine or equivalent)
Patients who have a known allergy or hypersensitivity to MTX
Patients who have a known serious adverse event with MTX prior to the trial leading to MTX discontinuation in the past
Presence of significant haematologic or renal disorder or abnormal laboratory values at screening that, in the opinion of the investigator is associated with an unacceptable risk to the patient to participate in the study
Clinical laboratory test results at screening that are outside a normal reference rating for the population and are considered clinically significant, or/and have any of the following specific abnormalities: Total white blood cell count < 3G/L; Neutrophil count < 1.5 G/l; Lymphocytes count < 0.5G/l. Platelet count < 100 G/l; Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) > 3 times the upper limit of normal (ULM); Haemoglobin < 8.5 g/dL (85.0 g/L); Creatinine clearance < 40 ml/min (Cockcroft formula)
For women: pregnant or breast feeding
Patients who have an active or serious infection or history of infections (bacterial, viral, fungal or mycobacteria), requiring hospitalisation or intravenous anti‐infectives infusion within 4 weeks prior to the baseline
Patients who have primary or secondary active immunodeficiency
Patients who had live vaccine administration within 4 weeks prior to baseline
Patients who have any current or active cancer (with the exception of patient with successfully treated basal cell carcinoma or in situ cervix carcinoma)
Patients who had history of malignancy within 5 years prior to the trial that could contraindicate the use of an immunosuppressant
Patients who will not be available for protocol which requires study visits or procedures
Patients who is not affiliated to the French Social Security system
Patients unable to give informed consent and/or comply with all required study procedures
