There are 3 approaches to combining observations from different points:
1) Multiple SET statements with WHERE clause
2) Transpose statement to convert all rows to a single row
3) SQL to combine to a single statement

However, it's important to remember that, for clinical trials, usually you want the "long skinny" organization with multiple observations per individual, because the appropriate tools are MIXED/GENMOD/GLIMMIX, which all require a TIME/VISIT variable under the SUBJECT. So all of this is changing the correct organization into an incorrect organization.