This is a multiple Ascending dose (MAD) study with GRC 27864 in Healthy and Elderly Subjects.

Inclusion Criteria:

1. Male or female subjects, aged ≥18 to <55 years (> 65 years for elderly cohort) at the time of informed consent
2. Body mass index (BMI) within the range 18.5-32 kg/m2 (inclusive); weight must be >50 kg
3. Subjects who are healthy and free from clinically significant illness or disease
4. Females must be of non-childbearing potential, surgically sterile.
5. Male subjects whose partners are of childbearing potential or have undergone tubal ligation must agree to use 2 highly effective methods of contraception

Exclusion Criteria:

1. Systolic blood pressure (SBP) <90 mmHg or >140 mmHg, diastolic blood pressure (DBP) <45 mmHg or >90 mmHg, resting pulse rate <40 beats per minute (bpm) or >100 bpm
2. Subjects who have the presence of active peptic ulcer disease, gastrointestinal (GI) bleeding, chronic gastritis, inflammatory bowel disease, chronic diarrhoea or positive 13C urea breath/faecal test for Helicobacter pylori at Screening.
3. Subjects with inherited or acquired disorders of platelet function, bleeding or coagulation.
4. Presence of any clinically relevant acute or chronic disease that could interfere with the subject's safety during the clinical study, expose the subject to undue risk.