Background
TGF-β has potent profibrotic activity in vitro and has long been implicated in systemic sclerosis (SSc), as expression of TGF-β-regulated genes is increased in the skin and lungs of patients with SSc. Therefore, inhibition of TGF-β may benefit these patients.
Conclusion
The rapid inhibition of TGF-β-regulated gene expression in response to fresolimumab strongly implicates TGF-β in the pathogenesis of fibrosis in SSc. Parallel improvement in the MRSS indicates that fresolimumab rapidly reverses markers of skin fibrosis.
Methods
Patients with early, diffuse cutaneous SSc were enrolled in an open-label trial of fresolimumab, a high-affinity neutralizing antibody that targets all 3 TGF-β isoforms. Seven patients received two 1 mg/kg doses of fresolimumab, and eight patients received one 5 mg/kg dose of fresolimumab. Serial mid-forearm skin biopsies, performed before and after treatment, were analyzed for expression of the TGF-β-regulated biomarker genes thrombospondin-1 (THBS1) and cartilage oligomeric protein (COMP) and stained for myofibroblasts. Clinical skin disease was assessed using the modified Rodnan skin score (MRSS).
Results
In patient skin, THBS1 expression rapidly declined after fresolimumab treatment in both groups (P = 0.0313 at 7 weeks and P = 0.0156 at 3 weeks), and skin expression of COMP exhibited a strong downward trend in both groups. Clinical skin disease dramatically and rapidly decreased (P < 0.001 at all time points). Expression levels of other TGF-β-regulated genes, including SERPINE1 and CTGF, declined (P = 0.049 and P = 0.012, respectively), and a 2-gene, longitudinal pharmacodynamic biomarker of SSc skin disease decreased after fresolimumab treatment (P = 0.0067). Dermal myofibroblast infiltration also declined in patient skin after fresolimumab (P < 0.05). Baseline levels of THBS1 were predictive of reduced THBS1 expression and improved MRSS after fresolimumab treatment.
Trial registration
Clinicaltrials.gov NCT01284322.