user: Question: What is Trial Start Date, when Candidate Name is PBT2?
Columns: ['Target/Approach', 'Candidate Name', 'Trial Phase', 'Trial Start Date', 'Expected End Date']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Gamma Secretase Modulator/NSAID', 'MPC-7869', 'Phase III', 'Feb 2005', 'May 2008']
SQL:

assistant: SELECT "Trial Start Date" FROM "Table" WHERE "Candidate Name" = 'PBT2';