DR P. MARAZZI/SCIENCE PHOTO LIBRARY

An experimental drug for the most severe forms of multiple sclerosis has slowed brain shrinkage by nearly a half.

There are dozens of therapies approved for the relapsing form of MS, a disease of the nervous system, in which people can be symptom-free for months before another attack. But there are very few for people suffering from more severe forms of the disease – known as primary progressive and secondary progressive MS and in which there is rarely any respite from disabling symptoms.

A clinical trial has now published its results, showing that the drug ibudilast …