BGS649 Monotherapy in Moderate to Severe Endometriosis Patients

Inclusion Criteria:

- Premenopausal women with documented moderate to severe endometriosis. Occurrence of
three sequential menstrual cycles of 24-35 days duration prior to enrollment.

- Laparoscopically proven diagnosis of moderate to severe endometriosis (diagnosed
within the past 10 years before screening).

- Patients not planning to become pregnant within one year after the screening visit and
willing to use two effective methods of non-hormonal, barrier birth control for the
duration of the study or who are surgically sterile.

- Patients must have a score of at least 4 on the numerical rating scale (NRS) for one
of the following three pain measurements: pelvic pain, menstrual pain and dyspareunia

Exclusion Criteria:

- Estrogen replacement therapy using either prescription medications or
estrogen-containing OTC nutritional/herbal supplements such as soy extracts or topical
estrogens.

- Aromatase inhibitor therapy (includes Femara (letrozole), Aromasin (exemestane) or
Arimidex (anastrozole) within the past 12 months.

- Oral bisphosphonate therapy (i.e. Fosamax (alendronate)) within the past 6 months or
intravenous bisphosphonate (i.e., Reclast, pamidronate) < 15 months from screening.

- Systemic glucocorticoid therapy within the past 4 weeks.

- Contra-indications to oral contraceptive use.

Other protocol-defined inclusion/exclusion criteria may apply