1. Practice true abstinence* (which must be reviewed at applicable study visits) or agree to use a condom during sexual contact while participating in the study, during dose interruptions and for at least 28 days following PNK-007 discontinuation, even if he has undergone a successful vasectomy. * True abstinence is acceptable when this is in line with the preferred and usual lifestyle of the subject. (Periodic abstinence [eg, calendar, ovulation, symptothermal, post ovulation methods] and withdrawal are not acceptable methods of contraception]).