A Study to Evaluate the Pharmacokinetics of an Oral Contraceptive When Co-administered With GSK2248761 in Healthy Adult Female Subjects.

This study is a two-period, double-blind study in healthy adult female subjects. Each subject will participate in an oral contraceptive Run-in period prior to the treatment periods. The length of the Run-in Period will be 28 days or longer, depending on the timing of the subject's menstrual cycle and on whether the subject is taking an OC. Each subject will participate in this run-in period (if needed), followed by two treatment periods. Treatment Periods 1 and 2 must be conducted successively. Subjects will be randomized in a cross-over fashion to either YASMIN with GSK2248761 or Placebo for 10 days and switch GSK2248761 or placebo for another 10 days. Subjects will return to the study center for final follow up evaluations 7 - 14 days after the final dose of study medication.