(407) MUC-031 as novel mucolytic agent for the treatment of cystic fibrosis

Background: Airway mucus plugging plays a key role in the initiation and progression of cystic fibrosis (CF) lung disease. We previously demonstrated that increased oxidation of free sulfhydryl groups of mucin monomers leads to abnormal cross-linking of mucins by disulfide bond formation and increases elasticity of the CF mucus gel. Thiol modified carbohydrate compounds (thiol-saccharides) cleave these bonds to decrease the elasticity of sputum. In this study, we investigated the effects of a thiol-saccharide, MUC-031, on viscoelastic properties of sputum from patients with CF and on airway mucus obstruction and inflammation in βENaC-Tg mice with CF-like lung disease.

Methods: The elastic modulus (G’) of CF sputum samples was measured using a cone-and-plate rheometer with baseline measures followed by addition (10% v/v) of MUC-031 (5 mM), Pulmozyme (20µg/mL), or PBS control, and repeated measures at 2 minute intervals for 30 minutes. At least 20 sputum samples were tested per condition, and mucolytic efficacy outcomes at 30 minutes included: (i) % decrease in G’; (ii) number of samples in which the starting G’ decreased by > 50%. Mucolytic and anti-inflammatory efficacy in vivo was determined in βENaC-Tg mice using acute, preventive and rescue therapy protocols. MUC-031 or vehicle alone was applied to βENaC-Tg mice and wild-type (WT) littermates by intratracheal (i.t.) or intranasal (i.n.) instillation in a volume of 1 µl/g body weight. To determine acute therapeutic effects of MUC-031, adult βENaC-Tg and WT mice were treated with MUC-031 or vehicle three times in one day. To evaluate effects of rescue therapy, adult βENaC-Tg and WT mice with chronic CF-like lung disease were treated with i.t. instillations two times a day (b.i.d.) for 2 weeks. To determine effects of preventive therapy, neonatal βENaC-Tg and WT mice from birth were treated with i.n. instillations b.i.d. for 2 weeks.

Results: The average % decrease in G’ at 30 minutes for MUC-031, Pulmozyme and PBS treated sputum samples was 73%, 55%, and 45%, respectively, and the number of samples in which the starting G’ decreased by half or more at 30 minutes was 95% for MUC-031, 60% for Pulmozyme and 35% for PBS. In adult βENaC-Tg mice, acute treatment with MUC-031 vs. vehicle alone reduced airway mucus content (7.21 ± 1.21 vs. 18.50 ± 3.21 nl/mm², P< 0.01) and BAL total cell counts (47,679 ± 7,736 vs. 73,833 ± 6,930 cells/ml, P< 0.05). Rescue therapy by 2-week treatment with MUC-031 vs. vehicle alone reduced airway mucus content (9.08 ± 1.19 vs. 14.91 ± 2.21 nl/mm², P< 0.05) and BAL total cell counts (76,895 ± 9,906 vs. 121,298 ± 13,091 cells/ml, P< 0.01). Preventive treatment with MUC-031 vs. vehicle for 2 weeks in neonatal βENaC-Tg mice resulted in decreased airway mucus content (15.81 ± 1.98 vs. 26.69 ± 3.16 nl/mm², P< 0.01), lower BAL total cell counts (216,321 ± 19,218 vs. 291,813 ± 30,066 cells/ml, P< 0.01) and lower mortality (21% vs. 37%, p< 0.05). No adverse effects of MUC-031 were seen in WT mice.

Conclusions: MUC-031 is a potent and fast acting mucolytic in CF sputum and reduces airway mucus plugging in adult and neonatal βENaC-Tg mice. These data provide strong rationale for further development of MUC-031 as a novel mucolytic drug for patients with CF and other muco-obstructive lung diseases. The improvement in airway inflammation in MUC-031-treated βENaC-Tg mice indicates that an increase in mucus clearance results in decreases in airway inflammation.

Acknowledgements: This study was supported by P01HL128191 from the NHLBI.

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