Raleigh, N.C. — Researchers in Great Britain say a drug used to treat leukemia can halt and even reverse the debilitating effects of multiple sclerosis. However, some very serious side effects could delay its availability to MS patients.

Pro golfer Tony Johnstone has MS. He thought he'd never play golf again.

"I got to the point, I couldn't walk 500 yards – really," Johnstone said.

Four years ago, doctors diagnosed Johnstone with multiple sclerosis, an autoimmune disease that attacks sight, mobility and memory. A drug designed to treat leukemia has Johnstone back on the golf course, however – and he recently won a PGA seniors tournament in Europe.

"To be told that you're never going to play again and then to get out there and to be able to compete doing the thing you love the most, I'm a very, very lucky chap," Johnstone said.

In a recent study, co-sponsored by the drug's maker, Alemtuzumab was about 70 percent more effective than the standard treatment for early MS.

"Very few of the patients have had any more attacks. And very few of them have built up any extra disability. In fact, many of them have even started to get better,” said professor Alastair Compston, a neurology expert.

MS causes the body to attack its own central nervous system. The drug protects battered nerves by temporarily depleting the body of white blood cells.

That is what can be risky. Patients could suffer bleeding disorders, thyroid disease, and infections. One participant in the British story died, but experts insist Alemtuzumab’s benefits outweigh the risks.

Dr. Lee Dunster, head of research for the MS Society in Great Britain, said, "To have a drug that reduces the risk of disability progression and possibly reverses some of the disability will be the single most important breakthrough in treatment of early, relapsing-remitting MS that we have seen to date.”

“More work is needed to prove the drug’s long-term effectiveness, and we are very much looking forward to the results of the next stage of this important research, which is already under way,” Dunster said in a {{a href=”external_link-1”}}statement on the society’s Web site{{/a}}

With that extra testing, the drug could be widely available in a few years. For Johnstone, though, it's a hole in one right now.