Study to investigate the safety profile of AZD4721 after single doses at different dose levels

A study to investigate safety and tolerability of single ascending doses of AZD4721 given to healthy volunteers. Including a bioequivalence part to compare a solution of AZD4721 with a suspension.

Inclusion Criteria:

1. Healthy male and/or female Caucasian (neither Black/African American nor Japanese) volunteers aged 18-50 years. ("Healthy" is as determined by medical history and physical examination, clinical laboratory parameters, and ECG )
2. Females must have a negative pregnancy test at screening and on admission to the unit, must not be lactating and must be of nonchildbearing potential
3. Volunteers should have a BMI between 18 and 30 kg/m2 (inclusive) and weigh at least 50 kg and no more than 100 kg (inclusive).

Exclusion Criteria:

1. History of any clinically important disease or disorder which, in the opinion of the Investigator, may either put the volunteer at risk because of participation in the study, or influence the results or the volunteer's ability to participate
2. Current smokers or those who have smoked or used nicotine products within the previous 3 months

2.Clinically significant lower respiratory tract infection not resolved within 4 weeks prior to Visit 1, as determined by the Investigator

4. Other latent or chronic infections (eg, recurrent sinusitis, genital or ocular herpes, urinary tract infection) or at risk of infection (surgery, trauma, or significant infection) in previous 90 days, or history of skin abscesses within the previous