This study is a double-blind, randomized, placebo-controlled, 2-period, crossover study to evaluate safety and PK of 3 doses of CVT 301 levodopa (l-dopa) in adults with asthma.

Inclusion Criteria:

• Eligible subjects will be men or women in good general health with a diagnosis of mild or moderate asthma;
• On a stable regimen of asthma medications for at least 30 days prior to screening;
• Body mass index (BMI) 18 to 32 kg/m2;
• Forced expiratory volume in one second (FEV1) ≥60% of predicted for race, age, sex, and height;
• FEV1/FVC (forced vital capacity) ratio ≥70%.

Exclusion Criteria:

• More than 2 hospitalizations or emergency room visits, or more than 3 courses of systemic steroids in the past 12 months or 1 course within the past 8 weeks for respiratory illness;
• Asthma exacerbation within 8 weeks before screening;
• Unscheduled or urgent visit to any medical facility for asthma-related problems within 8 weeks before screening;
• History of intubation or intensive care unit admission for asthma in the past 5 years;
• History of chronic obstructive pulmonary disorder (COPD) requiring intermittent or continuous use of any oral or inhaled medication therapy within last 3 years;
• Renal impairment as defined by a calculated creatinine clearance of ≤ 80 mL/minute.