The purpose of the study is to investigate how effective VA111913 is at preventing menstrual pain in women with primary dysmenorrhoea.

Dysmenorrhoea is suffered by between 50% and 90% of women of child bearing age. Up to 30% of these women are non-responsive to the currently prescribed therapies. As such it represents an area of unmet medical need. VA111913 inhibits vasopressin-induced contractions of human myometrial strips and human myometrial blood vessels in vitro. By this mechanism, it is anticipated that the pain of dysmenorrhoea, a condition in which myometrial tone and contractions are increased and blood flow to the uterus is decreased compared to normal, may be reduced.

Subjects will be dosed with VA111913 TS and placebo in a cross over design during two consecutive menstrual cycles. They will be dosed for up to a maximum of 6 days, beginning 2 days before the onset of menstruation. Subjects will then assess the menstrual pain, bleeding and amount of analgesia required to treat symptoms during each cycle

Inclusion Criteria:

• Women between 18 and 35 years old
• Not pregnant
• History of primary dysmenorrhoea
• Regular menstrual cycles
• Signed informed consent

Exclusion Criteria:

• Known secondary dysmenorrhoea
• Concomitant use of regular prescription or non prescription medications or herbal remedies
• Any clinically significant medical history or active disease
• Participation in another clinical study in the last 3 months
• Contraindication to chosen rescue medications or allergy to their constituents
• Other protocol defined eligibility criteria may apply