[kadet.89]

In case somebody needs it. The pointer can be cast to IServerEntity. This interface has a method to get the entity index:
(IServerEntity -> IServerUnknown -> IHandleEntity -> GetRefEHandle)
const CBaseHandle& baseHandle = baseEntity_->GetRefEHandle();
int index = baseHandle.GetEntryIndex();

Then the info can be received this way:
IGamePlayer * player = playerhelpers->GetGamePlayer(index);