Elevated thyrotropin level was observed at a slightly higher frequency in this trial compared with the PD trial of verdiperstat.26 Of note, hypothyroidism was monitored as an AE of special interest in this trial based on preclinical studies showing that verdiperstat has off-target effects on thyroid peroxidase, which is structurally similar to MPO. The gene discussed is TPO; the disease is hypothyroidism.