Efficacy and safety of L0133 in the treatment of dermatomyositis and polymyositis: prospective, randomised, double-blind, placebo-controlled study

INTERVENTION: The study will comprise three periods: 1. Run‐in period: observational period, in which patients under conventional therapies (GS, IS) will be followed. Only patients with an insufficient improvement on muscle strength will be allowed to enter Period I. 2. Period I: randomised, double‐blind, placebo‐controlled, two‐parallel groups design (stratification between DM and PM patients). 3. Period II: open‐labelled, non comparative, one‐arm design. 1. L0133 product: 2 g/Kg (40 ml/Kg) IV per month, delivered in two consecutive days (1 g/Kg daily or 20 ml/Kg daily) during period I and period II 2. Placebo: 40 ml/Kg IV per month, delivered in two consecutive days (20 mL/Kg daily) during period I only CONDITION: Dermatomyositis (DM) and polymyositis (PM) ; Skin and Connective Tissue Diseases ; Systemic connective tissue disorders PRIMARY OUTCOME: 1. Muscle strength intensity, as defined by the BMRC.; 2. Treatment response will be defined as an improvement from baseline of BMRC score at the end of Period I. SECONDARY OUTCOME: 1. Time course evaluation of muscle strength using BMRC index (run‐in period, Period I and Period II).; 2. Physical function recorded by the patients, as measured by the Health Assessment Questionnaire (HAQ) scale.; 3. Visual Analogue Scale (VAS) global disease activity made by the Investigators and the patients; 4. Serum activity of muscle enzymes ‐ Measurement outcome as defined by International Myositis Assessment and Clinical Studies Group (IMACS).; 5. Cutaneous signs severity, according to the modified three‐point scale from Göttfried ; 6. Other organ involvement (cardiac, pharyngeal, gastro‐intestinal, joint, pulmonary, others) assessed by the Investigators, using clinical and paraclinical examinations.; 7. Consumption of prednisone during the run‐in period, Period I and Period II.; 8. Consumption of IS during period II.; 9. Routine blood laboratory tests (haematology, chemistry).; 10. Adverse events. INCLUSION CRITERIA: Current inclusion criteria as of 14/08/2009: 1. Male or female patients of at least 18 years of age 2. Patients fulfilling the diagnostic criteria (definite or probable) of the European Neuromuscular Committee (ENMC) for idiopathic DM and PM 3.1. Patients with an active DM or PM disease who received conventional therapies for at least 14 weeks: oral prednisone 1 mg/kg per day for at least 4 weeks, with or without immunosuppressors (IS), followed by IS at stable dose and prednisone for at least 10 weeks, or 3.2. Patients with a contra‐indication or a major side‐effect to prednisone or methotrexate/other IS, or 3.3. Patients under biotherapy with a documented deterioration of their British Medical Research Council (BMRC) score, or 3.4. DM patients under biotherapy having a documented deterioration of their cutaneous signs, or 3.5. Patients under biotherapy with an onset of visceral involvement 4. Patients with no significant improvement of mu