Phase Ib/II Clinical Trial of Topical Verapamil Hydrochloride for Chronic Rhinosinusitis With Nasal Polyps

CRSwNP is a prevalent disease associated with major direct and indirect costs. Acute and Chronic Rhinosinusitis are estimated to affect up to 16% of the US population. They account for approximately 11 million or 1% of all office visits per year in the US and are the most common cause for antibiotic prescriptions in the community. CRS alone impacts more than 30 million Americans resulting in $6.9 to $9.9 billion in annual healthcare expenditures and $12.8 billion in productivity costs. The subset of patients in Europe with CRSwNP has been estimated to be between 2 and 4.3% and is thought to be similar in the US. This population remains one of the most challenging subgroups of CRS to manage effectively.

Recent evidence has focused on the sinonasal epithelial cell as a primary driver of the local dysregulated immune response through secretion of type 2 helper T-cell(Th2) promoting cytokines. While these studies suggest that epithelial cells are capable of orchestrating a local immune response, the mechanisms responsible for regulating cytokine secretion are poorly understood and may be influenced by the efflux function of epithelial P-glycoprotein(P-gp). Studies by the investigator's group have demonstrated that P-gp is overexpressed in the mucosa of patients with Th2 skewed CRS endotypes including CRSwNP and is capable of regulating the secretion of Th2 polarizing cytokines. Together, these findings suggest that P-gp participates in the non-canonical regulation of cytokine secretion within CRSwNP and may thereby represent a druggable target.

The investigator's group therefore undertook a randomized, double-blind, placebo-controlled trial to test the efficacy of low dose oral Verapamil HCl, a known first generation P-gp inhibitor, for the treatment of CRSwNP. Our findings demonstrated significant efficacy in both of the primary and secondary endpoints with no significant side effects. However, a logistic regression analysis revealed two important relationships between baseline characteristics and efficacy. First, patients with elevated BMI had significantly lower improvements in the Sinonasal Outcome Test (SNOT-22) (p=0.01). The second is that patients with the highest total mucus P-gp levels experienced less benefit(p=0.01).

While Verapamil HCl has significant potential for the treatment of CRSwNP through P-gp inhibition, higher doses must be achieved to extend the effect to patients with elevated BMIs and the highest levels of P-gp expression. As increasing oral dosing could result in cardiac side effects, topical delivery represents a promising alternative. As exosome bound P-gp may be more stable and representative of disease state than total mucus P-gp concentration, exosomal P-gp demands further exploration as a novel biomarker of disease severity and drug response.