Safety and Efficacy of B-Cell Depletion with Rituximab for the Treatment of Systemic Sclerosis Associated Pulmonary Arterial Hypertension: A Multi-center, Double-blind, Randomized, Placebo-controlled Trial.

Systemic sclerosis-pulmonary arterial hypertension (SSc-PAH) is one of the most prevalent and deadly forms of PAH. B cells may contribute to SSc pathogenesis.
We investigated the safety and efficacy of B-cell depletion for SSc-PAH.
In an NIH-sponsored, multi-center, double-blinded, randomized, placebo-controlled, proof-of-concept trial, 57 SSc-PAH patients on stable-dose standard medical therapy received two infusions of 1000 mg of rituximab or placebo administered two weeks apart. The primary outcome measure was the change in six-minute walk distance (6MWD) at 24 weeks. Secondary endpoints included safety and invasive hemodynamics. We applied a machine learning approach to predict drug-responsiveness.
We randomized 57 subjects from 2010-2018. In the primary analysis, using data through week 24, the adjusted mean change in 6MWD at 24 weeks favored the treatment arm but did not reach statistical significance (23.6±11.1m vs. 0.5±9.7m, p=0.12). While a negative study, when data through week 48 were also considered, the estimated change in 6MWD at week 24 was 25.5±8.8m for rituximab and 0.4±7.4m for placebo (p=0.03). Rituximab treatment appeared to be safe and well tolerated. Low levels of rheumatoid factor (RF), IL-12, and IL-17 were sensitive and specific as favorable predictors of a rituximab response as measured by an improved 6MWD (ROC AUC 0.88-0.95).
B cell depletion therapy is a potentially effective and safe adjuvant treatment for SSc-PAH. Future studies in these patients can confirm whether the identified biomarkers predict rituximab-responsiveness. Clinical trial registration available at www.clinicaltrials.gov, ID: NCT01086540.