Around 3,000 people with a severe form of multiple sclerosis (MS) are set to benefit after the National Institute for Health and Clinical Excellence (NICE) approved a new drug.
The regulator said Tysabri (natalizumab) can be given on the NHS to sufferers of rapidly evolving, severe relapsing-remitting MS.
MS is an autoimmune disease which destroys the protective fatty sheath surrounding nerve fibres.
There is no known cure at the moment, but a number of drugs that affect the immune system are used to reduce the symptoms.
The MS Society said that after two years of treatment, the drug showed a 42% reduction in the risk of a sustained increase in disability, and a 68% fall in the risk of relapse compared with a placebo.
Simon Gillespie, the MS Society's chief executive, said: "We welcome confirmation of NICE's decision to approve Tysabri, which represents a vital treatment option for people with highly active relapsing-remitting MS.
"The health trusts now have three months to make Tysabri available and we hope there are no unnecessary delays.
"We will be keeping a close eye on prescribing to make sure that people who stand to benefit from Tysabri are able to get the drug locally, and we hope no-one finds their access limited by local funding concerns."