Epelsiban is a potent and selective oxytocin receptor antagonist in development for enhanced implantation rates during in-vitro fertilization (IVF). This study a non-randomized, open label study designed to assess the safety, tolerability and pharmacokinetics of additional repeat doses of epelsiban in healthy females, and will be the first dosing experience of greater than 200 milligram (mg) as a single dose with this compound. Data from this study will inform the selection of doses of epelsiban to be used in future clinical studies. This study will be composed of 3 periods: Screening, Treatment, and Follow-up. The total duration that a subject involved in the study will be up to 6 weeks. At least 2 cohorts of subjects will be enrolled in this study and cohorts will be conducted sequentially. Additional cohorts will be enrolled if determined necessary. A sufficient number of subjects will be screened for the study to obtain approximately 6 evaluable subjects per cohort.

Inclusion Criteria:

• Females between 18 and 55 years of age inclusive, at the time of consent.
• Healthy as determined by the Investigator or medically qualified designee based on a medical evaluation including medical history, review of medications previously used, physical examination, laboratory tests and ECG.
• Body mass index (BMI) within the range 18-35 kilogram per square meter( kg/m^2) (inclusive).
• Female subject is eligible to participate if she is not pregnant (as confirmed by a negative serum human chorionic gonadotropin [hCG] test), not lactating, and at least one of the following conditions applies: Non-reproductive potential or postmenopausal.

Exclusion Criteria

• Alanine Transferase (ALT) and bilirubin >1.5x upper limit of normal(ULN) (isolated bilirubin >1.5xULN is acceptable if bilirubin is fractionated and direct bilirubin <35%).
• Current or chronic history of liver disease, or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones).
• Corrected QT (QTc) > 450 milliseconds (msec). - History of regular alcohol consumption within 3 months of dosing on Day 1 defined as: an average weekly intake of >7 drinks for females. One drink is equivalent to 12 gram of alcohol: 12 ounces (360 milliliter [mL]) of beer, 5 ounces (150 mL) of wine or 1.5 ounces (45 mL) of 80 proof distilled spirits.
• Urinary cotinine levels indicative of smoking or history or regular use of tobacco- or nicotine-containing products within 6 months prior to screening.
• History of sensitivity to any of the study medications, or components thereof or a history of drug or other allergy that, in the opinion of the Investigator or Medical Monitor, contraindicates their participation.
• Presence of hepatitis B surface antigen (HBsAg), positive hepatitis C antibody test result at screening or within 3 months prior to first dose of Study Treatment. For potent immunosuppressive agents, subjects with presence of hepatitis B core antibody (HBcAb) should also be excluded.
• A positive pre-study drug/alcohol screen.
• A positive test for human immunodeficiency virus antibody.
• Where participation in the study would result in donation of blood or blood products in excess of 500 mL within 3 months.
• The subject has participated in a clinical trial and has received an investigational product within the following time period prior to the first dosing day in the current study: 30 days, 5 half-lives or twice the duration of the biological effect of the investigational product (whichever is longer).
• Exposure to more than four new chemical entities within 12 months prior to the first dosing day.

IPD for this study will be made available via the Clinical Study Data Request site.

IPD is available via the Clinical Study Data Request site (click on the link provided below)

Access is provided after a research proposal is submitted and has received approval from the Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension can be granted, when justified, for up to another 12 months.