Some ebola variants that affect monkeys, for example, don't seem to affect people (Ebola Reston).
You would need sick people to even test the efficacy of a 'cure', or a vaccine.
Pretty limited opportunities for testing.
Whether there have been efforts to create a cure in case someone uses weaponized filoviruses (Ebola, Marburg) against us I do not pretend to know, but being able to just whip out a cure would mean not only familiarity with a variant which is not the same as previous variants, but have the ability to be certain the serum would work.
“Where would you test such a serum?”
Finding human guinea pigs has NEVER been problem, ever.