Effect of Vitamin D as add-on Therapy for Vitamin D Insufficient Patients With Severe Asthma

Patients with severe asthma represent the greatest unmet medical need among the asthmatic population, in particular due to their high risk of severe exacerbations. A substantial proportion of these patients does not achieve asthma control despite even high-dose ICS and LABA treatment, necessitating add-on therapy. For these patients oral corticosteroids (OCS) are a preferred treatment modality, which will inevitably lead to severe side effects. A high Proportion of patients with severe Asthma are Vitamin D insufficient (\< 30 ng/ml). It is therefore tempting to speculate that vitamin D substitution in vitamin D insufficient patients who continue to experience suboptimal asthma control on ICS and LABA or ICS/LABA plus OCS treatment may boost corticosteroid responsiveness, thereby potentially reducing corticosteroid dose requirements and improving key parameters of asthma control. The present study is a multicenter, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of treatment with vitamin D at a dose of 4000 IU/day administered daily following a single loading dose of 100 000 IU upon study entry over a period of 24 weeks in patients with severe asthma and vitamin D insufficiency. During the study, all patients will remain on their existing maintenance asthma therapy throughout the study, in addition to the study treatment, while reducing inhaled or oral steroids according to study protocol. The study consists of a 2-week run-in period, a 24 week double-blind treatment period including a 12 week steroid stable phase and two steroid reduction phases, followed by a follow-up visit 4 weeks after last study medication intake. The active treatment arm in this study will be standard of care plus vitamin D (loading dose of 100 000 IU upon study entry, to be followed by 4000 IU/day for the rest of the study period) while the comparator arm will be standard of care plus placebo.