After a 2-week placebo lead-in period, exenatide will be given in an esclating dose along with the subject's current therapy regimen

After a 2-week placebo lead-in period, subjects will be given placebo (in equivalent amounts to exenatide) in addition to their current therapy regimen.

After a 2-week placebo lead-in period (twice daily, given subcutaneously) in addition to their current therapy regimen, subjects will administer 20 mcg of exenatide (2 units [5 μg] ), twice daily by subcutaneous injection, for the first 4 weeks of therapy, and then 40 μL of study drug (4 units [10 μg] of exenatide) twice daily by subcutaneous injection, for the remaining 12 weeks of therapy.

Change in HbA1c from Baseline (Visit 3) to study termination at Week 16, and at all study visits in between

Change from Baseline to Week 16 in FSG and glucose measured at different times throughout the day derived from 7-point self-monitored glucose (SMG) profile (glucose measurements before and 2 hours after the start of the morning, midday, and evening meals, and at bedtime)

The percentage of subjects reaching the target HbA1c (<7%) will be summarized and compared by treatment