Multiple sclerosis sufferers may be offered the first pills to prevent relapses within two years, as two medicines report favourable trial results.
Both have a similar success rate in dampening the immune response that causes nerve damage related to MS, although they work differently.
German-based pharmaceutical company Merck developed cladribine, which patients must take between 20 and 40 times per year as the pills have longer lasting effects than Novartis' rival drug fingolimod, which must be taken daily.
The two companies are racing to become the first with an authorised oral medication for MS, and development of cladribine and fingolimod are progressing at similar rates.
The New England Journal of Medicine published results from clinical studies for both drugs at the same time on its website, adding to the competition.
Findings revealed patients with the most common form of "intermittent" MS had similar results with the treatments, which lowered relapse rates and halted the disease's progression.
Fingolimod test subjects were between 54% and 60% less likely to suffer a relapse than patients taking a daily placebo pill, while cladribine findings showed a reduction in relapse rate of 55% to 58% compared to patients given "dummy" drugs.
Neither medicine caused any significant side-effects in patients, and both reduced the likelihood of the disease progressing to a more severe form by about 33%.
Although it is thought fingolimod and cladribine will be commercially available by the end of 2011, it is not yet known whether they will meet the cost-effectiveness standards required for NHS prescription.