- Women of childbearing potential are required to have a negative serum pregnancy test (with a sensitivity of at least 25 milli 0international unit/microliter (mL) within 10-14 days prior to treatment start and be required to agree to have the test repeated within 24 hours prior to the first dose of GDC-0449 (serum or urine); a pregnancy test (serum or urine) will be administered every 4 weeks if their menstrual cycles are regular or every 2 weeks if their cycles are irregular while on study within the 24-hour period prior to the administration of GDC-0449; a positive urine test must be confirmed by a serum pregnancy test; prior to dispensing GDC-0449, the investigator must confirm and document the patient's use of two contraceptive methods, dates of negative pregnancy test, and confirm the patient's understanding of the teratogenic potential of GDC-0449; women of childbearing potential are defined as follows: