- Females of childbearing potential, unless surgically sterile (ie, bilateral tubal ligation, bilateral oophorectomy, or complete hysterectomy), has sterile male partner, is at least 2 years post menopause, or practices abstinence, must use 2 effective methods of avoiding pregnancy (including oral, transdermal, or implanted contraceptives, intrauterine device, female condom with spermicide, diaphragm with spermicide, cervical cap, or use of a condom with spermicide by the sexual partner), from screening, and must agree to continue using such precautions through the Early Discontinuation Visit/End of Study (Day 85, single-dose cohorts); cessation of birth control should not occur until 5 half-lives post-cessation of MEDI-551, 5 half-lives is estimated to be 75 days