People with secondary progressive multiple sclerosis who took the drug siponimod for one to two years had improved cognitive processing speed compared to those who did not take the drug, according to a new study by researchers at the University of Buffalo, in New York.

For the study, 1,651 people with secondary progressive MS with an average age of 48 were followed for up to two years. Two-thirds of the group was prescribed two milligrams a day of siponimod. One-third of the group was prescribed a placebo. All people in the study were given cognitive tests at the start of the study and again every six months.

One of those tests, the Symbol Digit Modalities Test, measures cognitive processing speed. It is widely recognized as a particularly sensitive and reliable test in MS studies. Researchers found on average the group of people taking siponimod improved their scores on this test after one year, 18 months, and again at two years, compared to the group of people taking placebo, in whom the score stayed the same.

People taking siponimod had a 28 percent higher chance of having a sustained improvement of four or more points compared to those taking a placebo. An increase or decrease of four or more points is considered clinically meaningful and is associated with quality of life outcomes and disability progression. People taking siponimod also had a 21 percent lower chance of having a four-point or lower decrease in score.

Among all participants, 35 percent of people taking siponimod improved their scores by four or more points compared to 27 percent of people taking a placebo, 41 percent taking siponimod had no change compared to 42 percent taking a placebo, and 25 percent taking siponimod had lower scores by four or more points compared to 32 percent of people taking a placebo.

Scores on two other thinking and memory tests did not differ between the two groups.

A limitation of the study was that researchers did not systematically collect information on education or MS symptoms – such as fatigue and depression – that possibly could influence the effect of siponimod on cognition. Education and depression have been shown to influence scores on the Symbol Digit Modalities Test.

The study was published in Neurology, the medical journal of the American Academy of Neurology.