Evaluate the Efficacy and Safety of FB704A in Adult With Severe Asthma

Approximately 20 subjects who meet the criteria for study entry are planned to be enrolled to the study. Eligible subjects will be randomized to receive placebo or FB704A in a 1:1 ratio, with an estimated 10 subjects per treatment arm. Eligibility will be checked in patients with severe asthma during the 4-week screening period. Potential candidates should provide signed informed consent forms before starting the screening activities. The subjects will receive four dose of 4 mg/kg FB704A or placebo. The study drug will be administered as a 1-hour IV infusion. Patients may administer Short-acting beta agonists (SABAs), such as albuterol as rescue medications as needed throughout the study. Subjects will have site visits after receiving study drug for efficacy, safety, PK, and biomarker evaluation (see Study Flow Chart). Subjects who prematurely withdraw from the study will have an end of study (EOS) visit within 7 days. Relative change in pre-bronchodilator FEV 1 , post-bronchodilator FEV 1, exhaled NO and asthma symptom s will be evaluated during the study.