Middle-aged man with idiopathic HES (negative workup including bone marrow studies, gene testing). No PDGFR mutation though has NF1 mutation, and there are case reports of an association. Regardless, I started mepolizumab with minimal response (WBC 23, eos 22%->WBC 25, eos 10%). No improvement with Hydrea 500 mg twice daily, unable to tolerate higher doses, and now unable to tolerate imatinib 400 mg daily. Any ideas of what else I should try?
Are you using the higher dose mepolizumab (300mg) because I find that usually works well. You can increase up to a max dose of 700mg monthly. Alternatively if that doesn't work I would try benralizumab 30mg q 4 weeks as this often works. Omalizumab and dupilumab are other options but seem to work less frequently. MMF and cyclosporine can be added on but the monitoring and side effects make them less desirable unless you really need them.
Yes, he's been on 300 mg monthly coming up to six months of therapy. I didn't know we could increase to 700 mg monthly. He had no issues with this medication. Do you ever combine mepolizumab with other agents?
You can combine mepolizumab with either cyclosporine or MMF. I usually try MMF first. If insurance will pay for it you could increase the mepolizumab first to see if that helps at all. Here is some literature to support the dose increase:
Gleich, Gerald J., et al. "Safety and efficacy of mepolizumab in hypereosinophilic syndrome: an open-label extension study." The Journal of Allergy and Clinical Immunology: In Practice 9.12 (2021): 4431-4440.
Chen, Michael M., et al. "An international, retrospective study of off-label biologic use in the treatment of hypereosinophilic syndromes." The Journal of Allergy and Clinical Immunology: In Practice 10.5 (2022): 1217-1228.
