Yes DLP 12.1.5 support mac agent
Endpoint Agent
The Symantec Data Loss Prevention Endpoint Agent is supported on the following operating systems and virtualized environments:
- Apple Mac OS X 10.8, 10.9
- Microsoft Windows 7, 8.0, 8.1; Server 2003, Server 2008
- Citrix XenApp 4.5, 6.0, 6.5; XenDesktop 3.0, 4.0, 5.0, 5.6
- Microsoft Hyper-V
- VMware Workstation 6.5; VMware View 4.6
http://www.symantec.com/en/in/data-loss-prevention/system-requirements/
See this linda_park blog
IMPROVED! DLP Endpoint Agent discovers data stored on Mac OS X; discovers, monitors and prevents events on Microsoft Windows 8.1 Desktop; monitors virtual desktops and applications hosted by Citrix XenApp 6.5, VMware View and Microsoft Hyper-V; and monitors data transferred through the Microsoft Remote Desktop Protocol (RDP
https://www-secure.symantec.com/connect/blogs/5-reasons-upgrade-data-loss-prevention-125