A Data and Safety Monitoring Board (DSMB) will be appointed to provide an independent evaluation of all safety data, including all laboratory results and serious adverse events (SAEs). The DSMB will conduct its review after 4 subjects in the 270 µg dose group have completed at least 6 doses, at any time death is reported, or at the request of the DSMB. The DSMB will also conduct an additional review at the End of Study.