Background/Purpose: To investigate the safety and preliminary efficacy of rituximab (RTX) in patients with refractory mixed connective tissue disease (MCTD)

Methods: We evaluated 9 patients in this observational cohort study. All received RTX (off label use) in addition to concomitant immunosuppressive agents. RTX treatment consisted of two endovenous infusions of 1 g1 g on days 1 and 15 per treatment cycle separated by a two-week interval. All the patients received premedication to prevent infusion reactions. The endpoint of patient follow-up was the date of the last clinic visit.

Results: All nine patients were women, with a mean age at the time of evaluation of 31 years (SD: 10; range 18-48). The indication for RTX was severe active polyarthritis in 5 cases, progressive nonspecific interstitial pneumonitis (evidence of clinical and functional decline) and inadequate articular response (DAS28 > 3.2) in 2, and autoimmune thrombocytopenia in 1 patient.

The median time to RTX treatment after MCTD diagnosis was 26 months (SD: 34.3; range 5-98 months). Concomitant immunosuppressive agents (azathioprine, mycophenolate, or methotrexate) were used in all patients and hydroxychloroquine in 6. The median follow-up time was 36 months (range, 5 – 80). When data were collected, patients had received a mean of 1.7 cycles (1-5) of RTX, with a dosing interval which ranged from 6 to 15 months.

In general, disease activity declined during therapy. All patients with arthritis achieved clinical remission (DAS28 < 2.6) or low activity (DAS28 ≤ 3.2) by week 16-20, although relapses of disease were frequent with re-treatment being required 6-7 months later. In the 2 patients with NSIP clinical improvement was accompanied by a parallel stabilization or mild improvement in pulmonary function tests (PFT). The autoimmune thrombocytopenia resolved completely after 1 cycle of treatment, without relapses after a follow-up period of 80 months.

The concomitant oral steroid dose could be reduced in more than half of the initial dose.

No cases of significant adverse events occurred and none of the patients suffered severe bacterial or opportunistic infections

Conclusion: Our preliminary results suggest that RTX seems to be a safe and useful therapeutic alternative in patients with active MTCD in whom previous treatments have failed, with a steroid-sparing effect.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rituximab-in-refractory-mixed-connective-tissue-disease-an-observational-study/