Rituximab therapy in patients with treatment-refractory hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) presents with a highly variable clinical course, and traditional treatment includes systemic corticosteroids and strict antigen avoidance. The objective of this study was to evaluate the therapeutic potential of Rituximab in patients with progressive hypersensitivity pneumonitis who do not respond to antigen avoidance and conventional immunosuppressive therapy. In this cohort prospective study, 30 patients with refractory HP were enrolled. Forced Vital Capacity (FVC) was assessed at three time points: six months before Rituximab initiation (M - 6), at treatment initiation (M0), and six months later (M + 6). FVC% predicted significantly declined from (58.57 ± 10.9) at M - 6 to (51.03 ± 11.06%) at M0 [p < 0.001], but showed a minimal, non-significant drop to 50.1 ± 12.7% at M + 6 [p = 0.405]. The rate of decline slowed markedly post-Rituximab, from - 7.54% (M - 6 to M0) to - 0.93% (M0 to M + 6). Dyspnea, measured by the mMRC scale, improved from 2.77 ± 0.5 at M0 to 1.83 ± 0.85 at M + 6 [p = 0.001]. 6MWD also increased from 258.67 ± 77 m to 307 ± 99 m [p = 0.001]. There were no reported cases of mortality. Rituximab demonstrates potential as an emerging therapeutic option for patients with treatment-refractory hypersensitivity pneumonitis and is well-tolerated.Trial registration: Retrospectively registered, registration number is NCT07035561, date of registration 16/06/2025.