Each subject will receive five intramuscular injections for a total of 0.5 mL of study drug in the glabellar area, during each treatment visit. Participation takes place over a maximum of 14 months, including Part 1 (Cycle 1 and 2) and Part 2 (Cycle 3). The number of clinic visits will vary from person to person depending upon the subject's response to the study drug, but will range from approximately 9 to 19 clinic visits. There will also be up to 4 telephone follow-up contacts.