Background/Purpose: Rituximab (RTX), a monoclonal B cell depleting antibody, is one of the few new drugs that has been shown to have beneficial effects on the fibrotic process in patients with systemic sclerosis (SSc). Whether long-time treatment with RTX might lead to hypogammaglobulinemia or lymphopenia that increase the susceptibility to infections in these patients is unknown. The purpose of this observational study was to analyse the levels of IgG and IgM as well as the number of lymphocytes and the frequency of serious infections in our cohort of SSc patients.

Methods: SSc patients (n=24; 18 female) with signs of alveolitis in the CT scan where started on a continuous intensified RTX treatment (500mg within 2 weeks every 3 months). The serum levels of IgG, IgM and the total lymphocyte counts were determined before the first RTX application and before the last RTX cycle within this year. Mean duration (95%CI) of RTX therapy was 40 months (30-50). Serious infections were evaluated by analyzing the medical records for hospitalisation because of infections. In addition, the European Scleroderma Study Group (EScSG) activity index as well as the modified Rodnan skin score (mRSS) and the diffusing capacity for carbon monoxide (DLCO) were used to estimate the therapeutic efficacy of RTX.

Results: : The EScSG activity index decreased significantly (p<0.0001), with a mean (±SE) of 3.5 (±0.3) at baseline and 0.4 (±0.1) after the last RTX cycle. In addition, the mean (±SE) mRSS was significantly lower in the last visit (8.0 ±1.4) compared to baseline value (23.9 ±2.4; p<0.0001). The DLCO (95% CI) value improved from 69.2% (61.4-77.5%) to 72.3% (64.5-80.1%), but did not reach significant levels (p=0.1612). The mean number of lymphocytes per 10⁹/L (±SE) was not significantly altered during the treatment period (p=0.0890) and ranged from 1.58 ±0.12 at the beginning and 1.42 ±0.1 after the last cyle (normal range 1.0 to 4.8). The mean IgG and IgM levels ±SE decreased significantly from 12.9g/L ±0.4 and 1.3g/L ±0.1 to 10.4 ±0.4 (p=0.0002) and 0.7 ±0.1 (p<0.0001), respctively. Interestingly, only 3 patients had IgM levels below the normal range of 0.4g/L. None of our patient had to be admitted to the hospital because of serious infections.

Conclusion: The intensified RTX protocol is an effective and safe therapeutic option for SSc patients. In contrast to patients with rheumatoid arthritis, in our SSc patients the total number of lymphocytes was not related to the clinical response to RTX.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/safety-and-efficacy-of-long-time-intensified-rituximab-treatment-in-patients-with-systemic-sclerosis/