The public doesn't know what ZMapp's "secret serum" does. But this description from a USAMRIID (Fort Detrick, MD) press release in July 2013 (referenced in today's CNN story on ebola) is intriguing to me:
"MB-003 is a “cocktail” of monoclonal antibodies that help bind to and inactivate the virus. In addition, said Pettitt, the antibodies recognize infected cells and trigger the immune system to kill them off. No side effects of the antibodies were observed in the surviving animals."
Bavituximab could still be involved -- as part of the cocktail. It's too early to rule it out, IMO.