Pills to treat multiple sclerosis could be available for the first time within two years following promising trial results.
A leading charity described the development as "great news" for people with the auto-immune disease, who currently have to undergo regular injections.
Two rival medicines are going head-to-head in the race to be the world's first oral treatments for MS.
Both dampen the immune response that causes MS-related nerve damage.
One, fingolimod, is a once-a-day treatment made by pharmaceutical giant Novartis. The other, cladribine, is produced by the German-based drug company Merck, and has longer lasting effects. A total of 20 to 40 tablets are taken over the course of a year.
Clinical studies of both drugs were published at the same time in the New England Journal of Medicine.
Each of the treatments appeared to be similarly effective at reducing relapse rates for patients with the most common form of "intermittent" MS, and holding back progression of the disease.
Both drugs cut the chances of progressing to a worse form of the disease by about a third, and neither produced significant side effects.