Henderson omalizumab study
A considerable proportion of patients with H1-antihistamine-resistant chronic spontaneous urticaria (CSU) fails to respond to omalizumab. However, there is yet no available biomarker that accurately predicts such a response outcome.  The utility of blood basophil and eosinophil levels and exosomal and basophil micro(mi)RNAs as biomarkers of response to omalizumab in CSU was explored. In this prospective cohort study of twenty patients with antihistamine-resistant CSU, subjects were treated with 3-monthly doses of omalizumab, and their response assessed using the weekly urticaria activity score (UAS7) for a period of 12-weeks. Basophil and eosinophil levels in the blood and differentially expressed exosomal and basophil miRNAs of complete responders compared to non-responders were identified at baseline.  Canonical pathways, altered by differentially expressed miRNAs, were identified using Ingenuity Pathway Analysis (IPA). Complete responders had higher baseline basophil levels (=21 cells/?L) in the peripheral blood compared to non-responders (P = 0.005). Baseline levels of eosinophils did not differ between the study groups. Complete responders in comparison to non-responders had an expression profile characterized by a significantly higher expression of six exosomal miRNAs (miR-6499-5p, miR-7848, miR-4494-3p, miR-450a-2-3p, miR-6877-3p, and miR-3976) and lower expression of miR-141-3p. Complete responders also had higher expression of three basophil miRNAs (miR-1200, miR-1236-3p, and miR-4496). The exosomal miRNA expression profile was predicted by IPA to alter Tec Kinase Signaling pathway activity (P = 0.003). Overall design: This was a single center, prospective cohort study, to investigate biomarkers of response to omalizumab in 22 adult patients (=18 years) with CSU who had remained symptomatic despite the use of high dose H1-antihistamines (ClinicalTrials.gov ID: NCT02814630). The study protocol was approved by the Western Institutional Review Board. The clinical part of the study was conducted at ASTHMA Inc. Clinical Research Center, Seattle, WA  (now named Seattle Allergy & Asthma Research Institute; https://seattleallergy.org). Before inclusion in the study, all patients provided written informed consent. Inclusion criteria were: 1) at least 6 weeks of CSU with itching despite current use of up to x4 H1-antihistamines49 and 2) an urticaria activity score (UAS) during a 7-day period (UAS7) of  =16 (on a scale ranging from 0 to 42, with higher scores indicating greater activity)50 during the 7 days before the first treatment with omalizumab. Exclusion criteria were: 1) a clearly defined underlying cause for chronic urticaria, 2) routine administration (i.e., daily or every other day for =5 consecutive days) of systemic glucocorticoids, hydroxychloroquine, methotrexate, cyclosporine, cyclophosphamide, or intravenous immune globulin within the previous 30 days, 3) the use of any H2-antihistamine or leukotriene-receptor antagonist within 7 days preceding the screening visit, 4) treatment with omalizumab within the previous year, or a known hypersensitivity to omalizumab, 5) a history of cancer, or 6) women who were pregnant or nursing or unable to use an effective method of contraception during dosing with omalizumab. After initial screening within two weeks of study start, patients received one subcutaneous injection of omalizumab (Xolair®; Genentech, South San Francisco, CA) at a dose of 300 mg on Days 0, 30, and 60 (Figure 1A).  This dose was based on results of two international, multicenter, randomized, double-blind, placebo-controlled Phase 3 studies, ASTERIA I25 and ASTERIA II17 that demonstrated that omalizumab significantly decreased clinical symptoms and signs of chronic urticaria in patients who had remained symptomatic despite the use of H1-antihistamines.25 Patients were closely monitored for 2 hours after each dose of omalizumab with epinephrine administered if evidence of anaphylaxis per the joint task force guidelines of the American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma & Immunology. Patients were provided with an epinephrine injector for self-administration of epinephrine if development of anaphylaxis after discharge from the CRC.  Plasma samples were collected at baseline (Day 0, prior to omalizumab injection) for isolation of basophils and exosomes (Figure 1A). Patients completed a twice-daily diary that was used to determine UAS7. Patients were classified as complete responder, partial responder or non-responder based on their UAS7 score.