Sound science would be the sole basis for safe and effective traditional therapies to be adopted, it said.
Any traditional remedies that are judged effective could be fast-tracked for large-scale manufacturing.
Madagascar's leader has been promoting an untested product he says can cure the disease despite the WHO warning against using untested remedies.
The WHO said the new rules were aimed at helping and empowering scientists in Africa to conduct proper clinical trials.
The move comes as the number of confirmed cases of coronavirus worldwide passes 30 million, with reported global deaths standing at more than 957,000. In Africa there have been more than 1.3 million cases and than 33,000 reported deaths.