A study of a new drug to treat advanced cases of multiple sclerosis suggests it may be possible to delay progression of the disease in the short term, although the effects were small.
In a trial of 1,327 people, in The Lancet, 26% saw their disability worsen after three months taking siponimod compared with 32% taking a dummy drug.
No drugs currently exist for secondary-progressive multiple sclerosis.
An MS expert expressed caution, saying other new treatments were still needed.
About 100,000 people in the UK have MS – a lifelong, progressive condition. Most are diagnosed between the ages of 20 and 70.
MS affects the central nervous system and can cause problems with:
Most cases start as relapsing-remitting MS and most of these develop into secondary-progressive MS within 15-20 years.
Patients in this trial, which was funded by drug company Novartis, had had MS for an average of 17 years – four years with secondary MS, the advanced stage.
Most needed assistance with walking before the trial began.
When standard measures of disability were used to track their progress, there was a 21% lower risk of walking or arm movements getting worse for those given the drug, compared with those taking the placebo.
But the international research team found the drug had no effect on maintaining patients' walking speed and it had some side-effects, although it was still thought to be safe.
Lead author Prof Ludwig Kappos, from the University of Basel, said: "This is not a breakthrough result
"Although the results are not as good as we wanted to see, it is a very large study, which is robust.
"It means siponimod is one option to delay the disease in the advanced stage."
Dr Susan Kohlhaas, director of research at the MS Society, said: "These results bring us closer to the first ever treatment for people with secondary-progressive MS – so it's big news.
"This trial showed that siponimod had a modest but significant effect in slowing disability progression, which is incredibly encouraging."
But Dr Luanne Metz, from the University of Calgary, in Canada, said a second trial was needed to confirm the benefits of the drug and its impact beyond three to six months.
She said: "Although siponimod seems to reduce the time to confirmed disability in secondary-progressive MS, the treatment effect was small.
"In our opinion… the absence of a significant difference for the key secondary clinical outcome are disappointing results and do not suggest that siponimod is an effective treatment for secondary-progressive MS."
She added: "Trials of other novel treatments that target non-inflammatory mechanisms are still needed."
Before the drug becomes available on the NHS, it would need to be approved by the European Medicines Agency and then recommended as cost-effective by bodies in the UK.