Study to Evaluate Pharmacokinetics, Pharmacodynamics, and Safety of Sargramostim Administered Subcutaneously, Intravenously, or by Inhalation

This single center, single ascending dose (SAD) and repeat dose study in healthy adults comprises 2 parts. Part 1 will consist of 6 SAD cohorts, in which different dose levels of sargramostim will be given by intravenous (IV) infusion, subcutaneous (SC) injection, or inhalation (IH) administration. Part 2 will consist of 1 repeat dose cohort in which sargramostim will begiven by SC administration. Blood samples for PK assessment will be collected before and over 24 hours after each study drug administration. Blood samples for PD assessment will be collected before and up to 14 days after drug administration in Part 1, as well as before the first and up to 14 days after the second drug administration in Part 2. Safety and tolerability will be assessed throughout the study. For Cohort 5 of Part 1 only, 3 subjects will provide a CSF sample for PK assessmen tonce after SC drug administration.