ADC3680 was safe and well tolerated in healthy male volunteers at single doses up to 200 mg, at doses up to 90 mg administered once daily for 7 days and in post-menopausal female volunteers at a single dose of 25 mg. ADC3680 was also well tolerated in male and female subjects with atopic asthma (22.73 mg once daily for 28 days). Most adverse events reported were mild or moderate and were considered to be unrelated to treatment. There were no clinically significant changes in laboratory safety parameters noted. No other safety issues of clinical relevance were identified that were considered likely to be treatment-related.