Teriflunomide levels in women whose male sexual partner is on teriflunomide for relapsing multiple sclerosis

For small molecules such as teriflunomide, used to treat relapsing multiple sclerosis (MS), that are potentially embryotoxic, there is a theoretical risk of transmission of the medication from males on the drug to female sexual partners. However, that risk has been undefined up to now.

Teriflunomide concentrations were assayed concomitantly in ten sexually active couples, not using barrier methods of contraception, in whom the male partner with MS was on treatment with teriflunomide 14 mg daily for at least two months. These results were compared by male and female age, teriflunomide concentrations and reported average number of incidences of sexual intercourse per month. The threshold level of detection of teriflunomide was 0.020 µg/ml in females.

The average age of the cohort was 46.70 for males and 47.10 for females. Four of ten females had detectible teriflunomide concentrations (mean 0.046 µg/ml (range 0.22-0.077, standard deviation 0.025). Male age and both female teriflunomide positive threshold and female teriflunomide concentration were inversely correlated (r = 0.67, R²=0.45, p = 0.034) for the former and (r = 0.62, R²=0.39, p = 0.05, ns) for the latter. No significant correlations were observed for female age, male teriflunomide concentrations, or reported mean monthly episodes of sexual intercourse.

This limited study suggests that the small risk that low levels of teriflunomide can be transmitted from male to female partners via sexual intercourse is related to male age. This supports the recommendations found in the United States Product Insert (USPI) stating that men taking teriflunomide who do not wish to father a child, and their female partners, should use reliable contraception. Men wishing to father a child should discontinue use of teriflunomide and undergo an accelerated elimination procedure to reduce the plasma concentrations of the medication to less than 0.02 mg/L (0.02 µg/ml¹.