Background/Purpose: Interstitial lung disease (ILD) is the major cause of mortality among scleroderma (systemic sclerosis, SSc) patients. Although immunosuppressive agents and several other drugs such as recently approved nintedanib and tocilizumab may stabilize lung function in some patients, long-term treatment is required, significant toxicity often occurs, and many patients will fail to respond. Therefore, there is an urgent and unmet need for new therapeutic approaches that would be more effective and less toxic than current treatments. We recently identified a unique 10 amino acid peptide (M10) characterized by potent antifibrotic and anti-inflammatory properties. In this study, we investigate efficacy, immunogenicity, and toxicity of M10 in rodents and in human cells.

Methods: Efficacy of M10 was studied in the bleomycin-induced therapeutic mouse model of SSc-ILD; immunogenicity was investigated in primary CD4+ T cells (ATCC® PCS-800-016) and cellular toxicity was studied in primary lung fibroblasts; single dose toxicity and maximum tolerated dose (MTD) of M10 was studied in C57BL/6 mice. Statistical analysis was performed using GraphPad Prism 7 software.

Results: In the bleomycin-induced therapeutic mouse model of SSc-ILD, M10 in a dose of 1mg/kg subcutaneously every 24 h noticeably reduced fibrosis of lung. A semi-quantitative evaluation of histopathology by Ashcroft scale demonstrated a significant (p < 0.01) decrease in bleomycin-induced fibrosis of M10-treated mice as compared to mice treated with scrambled peptide. We observed that M10 in doses of 1 µg/ml, 10 µg/ml, and 100 µg/ml for 24 h does not affect secretion of IFN-γ by CD4+ T cells, suggesting that M10 does not induce immunogenicity under the conditions tested. In contrast, phytohaemagglutinin-activated CD4+ T cells (used as a positive control) increased the secretion of IFN-γ from 45.2±9.7 pg/ml to 529±82.4 pg/ml, p < 0.001. M10 had no effects on cellular viability in all studied doses in normal and SSc-ILD lung fibroblasts. The experimentally determined MTD of subcutaneously delivered M10 in rodents was equal to 1000 mg/kg. We have not observed any mortality or critical weight loss of mice including those receiving the highest tested dose of 1000mg/kg within all 14 days of observation.

Conclusion: Lack of immunogenicity and low toxicity in combination with high efficacy of M10 peptide in an animal model of lung fibrosis suggest that M10 may be a safe and effective treatment for SSc-ILD that warrants further development.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/evaluation-of-efficacy-immunogenicity-and-toxicity-of-a-novel-drug-candidate-for-scleroderma-associated-interstitial-lung-disease/