Patients taking cladribine were between 55% and 58% less likely to suffer a relapse than those given a “dummy” placebo pill.
Patients treated with fingolimod and compared with those given a placebo experienced a reduction in relapse rate of 54% to 60%.
They are said to be more effective than expensive “disease modifying” MS drugs such as beta interferon and glatiramer acetate, which have to be injected.
The drugs are expected to be available by the end of 2011. However, it remains to be seen whether they are regarded as cost effective enough to be prescribed on the NHS.
The MS Society said it would be lobbying for the drugs to reach patients in the UK.
Doug Brown, the charity's biomedical research manager, said: “This is great news for people with MS and signifies a shifting tide in the treatment of the condition.
“Availability of oral therapies will give people greater choice, and being able to take a tablet instead of unpleasant injections will come as a welcome relief.
“The evidence is now there and we will be working with the relevant authorities to make sure those who will benefit can get access.”
Controversy already surrounds the availability of beta interferon and other disease modifying drugs.
It costs between £7,260 and £12,000 a year to treat a single patient with beta interferon. Despite a “risk sharing” scheme under which drug manufacturers agree to bear the cost if an individual course of treatment fails, access to the drugs is still “patchy”, according to the MS Society. Many patients who could benefit from the drugs are still being denied them, it is claimed.
Cladribine is currently used in an injected form to treat certain types of leukaemia, which may speed up its availability.
An estimated 100,000 people in the UK suffer from MS, which occurs when the protective myelin sheath that coats nerve fibres in the brain is stripped away.
Without myelin, nerve messages are not transmitted properly and the nerve itself is vulnerable to damage.
Symptoms of the disease may range from mild tingling sensations to major paralysis or loss of vision. Most patients have the “relapse remitting” form of MS marked by healthy periods punctuated by episodes of symptoms.
Professor Gavin Giovanonni, from Queen Mary, University of London, who led the cladribine trial involving more than 1,300 MS patients, said: “The introduction of an oral therapy, particularly one that has no short-term side effects and is as easy to use as oral cladribine, will have a major impact on the treatment of MS.
“However, the use of this drug as a first-line therapy will have to be weighed up against the potential long-term risks which have yet to be defined.”
Consultant neurologist Eli Silber, an investigator on the fingolimod trial based at King's College Hospital, London, said: “These data are exciting because fingolimod is an oral therapy and a new class of drug.
“It has good efficacy and could offer patients with relapsing-remitting MS another treatment choice.”