Tocilizumab has demonstrated lung function preservation in two randomized controlled trials in early systemic sclerosis (SSc). This effect has yet to be characterized in terms of quantitative radiographic lung involvement. In this post-hoc analysis, we assess tocilizumab's impact on lung function preservation, stratifying treatment arms by the degree of radiographic lung involvement.

The focuSSced trial was a phase 3, randomized placebo-controlled trial of tocilizumab in patients with SSc and progressive skin disease. Participants had baseline and serial spirometry along with high resolution chest CT at baseline and week 48. Quantitative interstitial lung disease and fibrosis were derived using computer software. We divided quantitative interstitial lung disease in mild (5-10%), moderate (>10-20%), or severe (>20%) categories.

Of 210 participants recruited in the trial, 136 [65%] had interstitial lung disease. The majority of these participants had moderate-to-severe involvement defined by >10% lung involvement (77%). The tocilizumab arm demonstrated preservation of forced vital capacity over 48 weeks (least squared mean change in %predicted = -0.1) compared to placebo (-6.3%). For mild, moderate, and severe QILD, the mean decline in the %pFVC in the tocilizumab arm at 48 weeks were -4.1, 0.7, and 2.1, and in the placebo group were -10.0, -5.7, and -6.7, respectively. Similar treatment-related preservation findings were seen independent of fibrosis severity.

Tocilizumab in early SSc- associated interstitial lung disease with progressive skin disease stabilized forced vital capacity over 48 weeks, independent of the extent of quantitative radiographic interstitial lung disease or fibrosis.