Safety and efficacy of lirentelimab in patients with refractory indolent systemic mastocytosis: a first-in-human clinical trial.

BACKGROUND: Indolent systemic mastocytosis (ISM) is characterized by excessive mast cell (MC) accumulation and MC-driven signs and symptoms. Currently used therapies are not approved and have limited efficacy. Lirentelimab (AK002) is a monoclonal antibody against sialic acid-binding immunoglobulin-like lectin (Siglec)-8 that inhibits MC activation. OBJECTIVES: To determine the safety, tolerability and efficacy of lirentelimab in reducing the symptoms of ISM. METHODS: At a specialty centre for mastocytosis in Germany, we conducted a phase I first-in-human single-ascending and multidose clinical trial of lirentelimab in patients with ISM. Eligible adults had World Health Organization-confirmed ISM and an unsatisfactory response to available treatment. In part A, patients received a single dose of lirentelimab 0.0003, 0.001, 0.003, 0.01 or 0.03 mg kg-1; in part B, patients received one lirentelimab dose of 0.3 mg kg-1 or 1.0 mg kg-1; and in part C, patients received either 1.0 mg kg-1 lirentelimab every 4 weeks for 6 months or ascending doses of lirentelimab (one dose of 1 mg kg-1 followed by five doses of 3-10 mg kg-1 every 4 weeks). The primary endpoint was safety/tolerability. Secondary endpoints included changes from baseline in Mastocytosis Symptom Questionnaire (MSQ), Mastocytosis Activity Score (MAS) and Mastocytosis Quality of Life Questionnaire (MC-QoL) scores at 2 weeks after the final dose. RESULTS: In 25 patients with ISM (13 in parts A + B and 12 in part C; median age 51 years, 76% female, median 4.6 years from diagnosis), the most common treatment-related adverse events (AEs) were feeling hot (76%) and experiencing a headache (48%). No serious AEs occurred. Median MSQ and MAS symptom severity scores in part C improved (vs. baseline) across all symptoms [MSQ: skin (38-56%), gastrointestinal (49-60%), neurological (47-59%), musculoskeletal (26-27%); MAS: skin (53-59%), gastrointestinal (72-85%), neurological (20-57%), musculoskeletal (25%)]. Median MC-QoL scores improved across all domains: symptoms (39%), social life/functioning (42%), emotions (57%) and skin (44%). CONCLUSIONS: Lirentelimab was generally well tolerated and improved symptoms and quality of life in patients with ISM. The therapeutic potential of lirentelimab should be considered for ISM.

Lirentelimab for severe and chronic forms of allergic conjunctivitis.

BACKGROUND: Allergic conjunctivitis (AC) is an ocular inflammatory disease with symptoms driven by eosinophils and mast cells. Allergic comorbidities are common. Current treatments are often ineffective in severe AC and limited by potential side effects. Lirentelimab is an anti-sialic acid-binding immunoglobulin-like lectin-8 mAb that depletes eosinophils and inhibits mast cells. OBJECTIVE: We sought to determine safety and preliminary efficacy of lirentelimab in an open-label, phase 1b study. METHODS: Patients with chronic, severely symptomatic atopic keratoconjunctivitis, vernal keratoconjunctivitis, and perennial AC, and who had history of topical or systemic corticosteroid use, were enrolled to receive up to 6 monthly lirentelimab infusions (dose 1: 0.3 mg/kg, dose 2: 1 mg/kg, subsequent doses: 1 or 3 mg/kg). Changes from baseline in peripheral blood eosinophils, changes in patient-reported symptoms (measured by daily Allergic Conjunctivitis Symptom Questionnaire, including atopic comorbidities), changes in investigator-reported ocular signs and symptoms (Ocular Symptom Scores), changes in quality of life, and changes in tear cytokine and chemokine levels were assessed. RESULTS: Thirty patients were enrolled (atopic keratoconjunctivitis n = 13, vernal keratoconjunctivitis n = 1, perennial AC n = 16), 87% of whom had atopic comorbidities. After lirentelimab treatment, mean improvement was observed in Allergic Conjunctivitis Symptom Questionnaire score (-61%; 95% CI, -75% to -48%) and Ocular Symptom Scores (-53%; 95% CI, -76% to -31%), consistent across atopic keratoconjunctivitis, vernal keratoconjunctivitis, and perennial AC groups. There was substantial improvement in atopic comorbidities, with -55% (95% CI, -78% to -31%), -50% (95% CI, -82% to -19%), and -63% (95% CI, -87% and -38%) reduction in symptoms of atopic dermatitis, asthma, and rhinitis, respectively. Levels of key mediators of inflammation were reduced in patient tears after lirentelimab treatment. The most common adverse effects were mild to moderate infusion-related reactions. CONCLUSIONS: Lirentelimab was well tolerated, improved severe AC and concomitant atopic symptoms, and reduced inflammatory mediators in patient tears.