P127 A retrospective cohort study assessing outcomes and safety in patients receiving low dose vs high dose cyclophosphamide in myositis interstitial lung disease

Abstract Background/Aims Interstitial lung disease (ILD) is associated with poor survival in patients with idiopathic inflammatory myopathies (IIM). Cyclophosphamide is often used in the management of myositis-associated ILD (IIM-ILD). The EUROLUPUS (0.5g IV fortnightly for 6 doses) regime has previously been shown to be as effective as high dose regimes in lupus nephritis. This study aims to evaluate whether the low dose EUROLUPUS (LD) cyclophosphamide regime vs a high dose (HD) regime (600 mg/m2 IV every 4 weeks from day 0 to week 20) was associated with the same outcomes and better safety profiles in patients with IIM-ILD. Methods A retrospective analysis of notes was undertaken for patients attending the King’s Health Partners ILD service across two hospital sites (King’s College Hospital and Guy’s Hospital) with a diagnosis of ILD and myositis or ILD and myositis specific antibodies. Adult patients who received cyclophosphamide with at least 18 months of follow-up lung function and HRCT data were analysed. Patients whose therapy was started on ITU were excluded. The primary outcome was the change in forced vital capacity (FVC) and transfer factor for carbon monoxide (TLCO) over 18 months. Descriptive statistics were used to compare the differences between the two regimes. Results 92 patients received cyclophosphamide for IIM-ILD. 53 (57.6%) patients received the HD regime vs 39 (42.3%) in the LD arm. The mean age was 53 (13). 61 (66.3%) patients were female. Anti-Jo-1 antibody was positive in 41.5% in the high dose group vs 25.6% in the low dose group. All-cause mortality was 11% in the HD arm vs 21% in the LD arm (p = 0.23). Change in FVC from baseline to 18 months was 0.5 (-0.1-1.1) in the HD arm vs 0.1 (-0.0-0.4) in the LD arm (p = 0.048). Change in TLCO was 0.4 (-0.1-1.9) in the HD arm vs -0.2 (-0.6-0.6) in the LD arm (p = 0.24). 9.4% in the HD arm had a serious infection vs 26.3% in the LD arm (p = 0.32). Lymphopenia was higher in the HD arm vs LD arm (43.4% vs 25.6%, p = 0.079). Patients in the LD arm had a longer duration of ILD, more non-specific interstitial pneumonia, less organizing pneumonia, more frequent mycophenolate mofetil use, more pulmonary hypertension, less frequent concomitant rituximab and a significantly higher creatine kinase at baseline, suggesting more severe/systemic disease. Conclusion HD cyclophosphamide was associated with a significant improvement in FVC vs LD cyclophosphamide at 18 months. All-cause mortality numerically favoured high dose cyclophosphamide and there were significantly fewer serious infections in the HD arm. This study serves as an initial exploratory analysis for the use of low dose cyclophosphamide regimes in IIM-ILD but larger randomised trials would be needed to assess the efficacy and safety of this regime. Disclosure S. Ali: None. A. Lawrence: None. K. Bechman: None. A.S. Patel: None. S. Birring: None. S. Steer: None. A. Mahto: None. K. Myall: None. L. Pollard: None. M. Naqvi: None. A.M. Holloway: None. R. Salerno: None. F. Dell’Accio: None. S. Agarwal: None. B. Lams: None. A. West: None. P. Gordon: Other; Alexion (Primary investigator at King’s college hospital for the NCT04999020 study (ALXN1210-DM-310). No personal payment) Argenx (PI at King’s College Hospital for study ARGX-113-2007 and Study ARGX-.

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