Gallen (elbow) threw two innings and 35 pitches to live hitters Thursday, Alex Weiner of Arizona Sports reports.
Gallen is next scheduled to throw a bullpen session Saturday after which the club will decide next steps. Arizona manager Torey Lovullo said there is a target date for Gallen and fellow injured starter Corbin Burnes (elbow), but the manager wasn't ready to reveal it and prefers to take the progression step-by-step before making any announcements.