Efficacy of Rituximab in Refractory Inflammatory Myopathies Associated with Anti- Synthetase Auto-Antibodies: An Open-Label, Phase II Trial

Abstract

Objective: Anti-synthetase syndrome (anti-SS) is frequently associated with myositis and interstitial lung disease (ILD). We evaluated prospectively, in a multicenter, open-label, phase II study, the efficacy of rituximab on muscle and lung outcomes.

Methods: Patients were enrolled if they were refractory to conventional treatments (prednisone and at least 2 immunosuppressants). They received 1 g of rituximab at D0, D15, and M6. The primary endpoint was muscular improvement based on manual muscular testing (MMT10, Kendall score in 10 muscles) at M12. Secondary endpoints were normalization of creatine kinase (CK) level, ILD improvement based on forced vital capacity and/or diffuse capacity for carbon monoxide, and number and/or doses of associated immunosuppressants.

Results: Twelve patients were enrolled, and 10 completed the study. Only 2 patients presented an improvement of at least 4 points on at least two muscle groups (primary end-point). Overall, seven patients had an increase of at least 4 points on MMT10. CK level decreased from 399 IU/L (range, 48-11,718) to 74.5 IU/L (range, 40-47,857). Corticosteroid doses decreased from 52.5 mg/d (range, 10-70) to 9 mg/d (range, 7-65) and six patients had a decrease in the burden of their associated immunosuppressants. At baseline, all 10 patients presented with ILD. At M12, improvement of ILD was observed in 5 out of the 10 patients, stabilization in 4, and worsening in 1.

Conclusions: This pilot study of rituximab treatment in patients with refractory anti-SS provided data on evolution of muscular and pulmonary parameters. Rituximab should now be evaluated in a larger, controlled study for this homogenous group of patients.

Trial registration: Clinicaltrials.gov NCT00774462.

Fig 1. Flowchart.

Fig 2. Evolution of strength and CK levels from baseline to months 18.

(A) MMT10 using Kendall score. (B) CK level. The continuous line and the dotted line represent the median Kendall score and the median CK level, respectively.

Fig 3. Interstitial lung disease evolution.

Lung CT scans, before enrolment (M0) and 1 year later (M12), of the only patient with and nonspecific interstitial pneumonia improving after rituximab infusions.

Fig 4. Forced vital capacity evolution.

Forced vital capacity (FVC) is represented for each patient who terminated the study and had interstitial lung disease (ILD). FVC is represented 6 months before enrolment (M−6), when available, and 6 and 12 months (M6 and M12) after the first rituximab infusion (arrow, M0). The grey area represents a decrease of ≥ 10% in absolute FVC at baseline compared with M−6. (*) Represents an increase or a decrease of ≥ 10% of absolute FVC or ≥ 15% of DLCOcor at M12 compared with M0.

Fig 5. SF-36 scores measuring parameters of mobility.

For each score (ranging from 0 to 100) the mean values (± SD) are represented at different time points: baseline (M0); months 6, 12 and 18 after rituximab infusion (M6, M12 and M18). The asterisk represents a significant increase (more than 10 points) compared with baseline.

Fig 6. Anti-Jo-1 titer variation and B-lymphocyte depletion.

Anti-Jo-1 titer was monitored for the 9 patients who terminated the study (the tenth had anti-PL-7). On the right side, 4 boxes represent the status at M12 (vs M0) concerning manual muscular testing (MM10), creatine kinase level (CK), treatment modification (treatment), and forced vital capacity (FVC). Black represents worsening, grey area represent no change, and white represents an improvement. Concerning CK, black shows an increased level at M12 and white a normal level.