A study conducted on the effects of omalizumab in treatment-resistant systemic and cutaneous mastocytosis yielded a mixed picture of the benefits of this treatment in this group of patients, according to a paper published in The Journal of Allergy and Clinical Immunology: In Practice. 

Omalizumab is a novel drug that binds to free immunoglobulin E, which restricts its binding to mast cells. This drug has been shown to demonstrate efficacy in the treatment of chronic spontaneous urticaria and severe allergic asthma. Scientists therefore sought to investigate if the benefits of this drug extend to the treatment of mastocytosis. The authors of the study were encouraged by previous studies that suggest a positive role for omalizumab in the treatment of mastocytosis. 

They conducted a single-center, double-blind, randomized phase 2 study investigating both the safety and efficacy of omalizumab in adult patients with systemic/cutaneous mastocytosis who were resistant to standard therapies. The dose was 375 mg, administered every 4 weeks over 6 months.

The research team recruited patients with indolent, smoldering, aggressive systemic, or cutaneous mastocytosis according to the World Health Organization criteria; patients must also have demonstrated “mastocytosis in the skin.” Participants must also have experienced breakthrough symptoms despite being on maximal tolerated conventional medications. 

Read more about systemic mastocytosis etiology 

Participants were randomized in a 1:1 ratio to receive omalizumab or placebo. Various laboratory parameters were measured and clinical photography of skin manifestations were taken at regular follow-up visits. All adverse events were documented for the evaluation of drug safety. 

The primary endpoint of the study was changes in the symptoms from baseline to 4 weeks after the final dose of omalizumab. Various laboratory parameters were also measured as secondary endpoints. Analyses were conducted based on intention-to-treat. 

One hundred twenty-three patients were eligible for the study. The research team reported that changes in symptom severity were greater among the treatment group compared with the placebo. However, dermatological clinical endpoints did not differ significantly between the 2 groups. Nevertheless, omalizumab was well tolerated. 

“The lack of improvement in parameters other than the overall [symptomatic] score likely represents the breadth of the score and the diversity of symptoms in mastocytosis,” the authors wrote. The results of this study, while inconclusive, warrant further studies with a larger population group. 


McComish JS, Slade CA, Buizen L, et al. Randomised controlled trial of omalizumab in treatment-resistant systemic and cutaneous mastocytosis (ROAM)J Allergy Clin Immunol Pract. Published online April 21, 2023. doi:10.1016/j.jaip.2023.04.008