This is a phase 1, multi-center, open-label, drug-drug interaction (DDI) and PK study in subjects with moderate to severe plaque psoriasis. It is designed to evaluate the effect of brodalumab on midazolam PK in addition to assessing single dose PK of brodalumab in subjects with moderate to severe plaque psoriasis.

Approximately 30 subjects will be enrolled into two groups. Group 1 consists of 20 subjects and will receive 2 oral doses of midazolam and a single subcutaneous (SC) dose of brodalumab. Group 2 consists of 10 subjects and will receive a single SC dose of brodalumab.

Inclusion Criteria:

• Subject has had stable moderate to severe plaque psoriasis for at least 6 months
• body mass index (BMI) between ≥ 18.0 and ≤ 38.0 kg/m2
• body weight between ≥ 50 and ≤ 130 kg
• no known history of active tuberculosis

Exclusion Criteria:

• Female subjects who are lactating/breastfeeding
• History or evidence of clinically significant disorder, condition or disease that, in the opinion of the investigator or Amgen physician would pose a risk to subject safety or interfere with the study evaluation, procedures or completion.