6. Pregnant or lactating women. All pre-menopausal women being screened must have a negative serum pregnancy test within 14 days prior to commencement of dosing. Women of non-childbearing potential may be included if they are either surgically sterile or have been postmenopausal for >/= 1 year. Fertile men and women must use an effective method of contraception during treatment and for at least 6 months after completion of treatment as directed by their physician.