Mavrilimumab, a Fully Human Granulocyte-Macrophage Colony-Stimulating Factor Receptor α Monoclonal Antibody: Long-Term Safety and Efficacy in Patients With Rheumatoid Arthritis.

Objective: Mavrilimumab, a human monoclonal antibody, targets granulocyte-macrophage colony-stimulating factor receptor α. We undertook to determine the long-term safety and efficacy of mavrilimumab in rheumatoid arthritis patients in 2 phase IIb studies (1071 and 1107) and in 1 open-label extension study (ClinicalTrials.gov identifier: NCT01712399).

Methods: In study 1071, patients with an inadequate response to disease-modifying antirheumatic drugs (DMARDs) received mavrilimumab (30, 100, or 150 mg) or placebo every other week plus methotrexate. In study 1107, patients with an inadequate response to anti-tumor necrosis factor agents and/or DMARDs received 100 mg mavrilimumab every other week or 50 mg golimumab every 4 weeks plus methotrexate. Patients entering the open-label extension study received 100 mg mavrilimumab every other week plus methotrexate. Long-term safety and efficacy of mavrilimumab were assessed.

Results: A total of 442 patients received mavrilimumab (14 of 245 patients from study 1071, 9 of 70 patients from study 1107, and 52 of 397 patients from the open-label extension study discontinued mavrilimumab treatment throughout the studies). The cumulative safety exposure was 899 patient-years; the median duration of mavrilimumab treatment was 2.5 years (range 0.1-3.3 years). The most common treatment-emergent adverse events (AEs) were nasopharyngitis (n = 69; 7.68 per 100 patient-years) and bronchitis (n = 51; 5.68 per 100 patient-years). At weeks 74 and 104, 3.5% and 6.2% of patients, respectively, demonstrated reduction in forced expiratory volume in 1 second, while 2.9% and 3.4% of patients, respectively, demonstrated reduction in forced vital capacity (>20% reduction from baseline to <80% predicted). Most pulmonary changes were transient and only infrequently associated with AEs. Mavrilimumab at 100 mg every other week demonstrated sustained efficacy; at week 122, 65.0% of patients achieved a Disease Activity Score in 28 joints using the C-reactive protein level (DAS28-CRP) of <3.2, and 40.6% of patients achieved a DAS28-CRP of <2.6.

Conclusion: Long-term treatment with mavrilimumab maintained response and was well-tolerated with no increased incidence of treatment-emergent AEs. Safety data were comparable with those from both phase IIb qualifying studies.