<qa>  What is the only way men must refrain from donating sperm?- For men: agreement to remain abstinent refrain from heterosexual intercourse or use contraceptive measures and agreement to refrain from donating sperm. With female partners of childbearing potential, men must remain abstinent or use a condom plus an additional contraceptive method that together result in a failure rate of 1 per year during the treatment period and for at least 7 months plus 90 days a spermatogenesis cycle after the last dose of study drug. Men must refrain from donating sperm during this same period. With pregnant female partners, men must remain abstinent or use a condom during the treatment period and for at least 7 months after the last dose of study drug. 