Pharmacological inhibition of MutT homolog 1 (MTH1) in allergic airway inflammation as a novel treatment strategy.

Background: Despite progress in the treatment of asthma, there is an unmet need for additional therapeutic strategies, not least to avoid side-effects of corticosteroids. The enzyme MutT homolog 1 (MTH1) hydrolyzes oxidized purines and prevents their insertion to DNA. Small molecule inhibition of MTH1 has shown promising therapeutic effects in both cancer and inflammatory conditions. In this study, a small molecule inhibitor of MTH1 (TH1579), was investigated in models of allergic inflammation.

Methods: In vitro, effects on T cell proliferation and apoptosis were investigated. Furthermore, a murine model, using female BALB/c mice, of OVA-induced allergic airway inflammation was used to investigate effects from MTH1-inhibition in vivo.

Results: Inhibition of MTH1 prevented T cell proliferation in vitro and induced apoptosis in isolated human CD4⁺ T cells. However, the viability of isolated human eosinophils was unaffected by MTH1 inhibition in vitro. Pharmacological inhibition of MTH1 in a murine model of allergic airway inflammation reduced mucus production, recruitment of inflammatory cells, such as T cells and eosinophils in the BAL fluid and lung tissue, reduced plasma levels of total IgE and OVA-specific IgE, IgG, and IgG1, as well as reduced IL-13 levels in BAL fluid, lung tissue and plasma.

Conclusion: MTH1 inhibition reduced proliferation and promoted apoptosis of T cells in vitro. In vivo, TH1579 dampened the type 2 associated immune response in a murine model. These findings suggest that MTH1 could serve as a novel target to treat allergic airway inflammation.