Trial Outcomes & Findings for A Study to Test Bioavailability of of 2 New Formulations of UCB0599 in Healthy Participants in Part A and to Test Safety, Tolerability, and Pharmacokinetic (PK) of UCB0599 in Healthy Japanese and Chinese Participants in Part B (NCT NCT05845645)

Last Updated: 2025-12-22

Results Overview

AUC(0-t) was area under the plasma concentration-time curve from time 0 to the last quantifiable concentration of UCB0599.

Recruitment status

COMPLETED

Study phase

PHASE1

Target enrollment

73 participants

Primary outcome timeframe

Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, and 6 in Part B

Results posted on

2025-12-22

Participant Flow

The study started to enroll participants in May 2023 and concluded in April 2024.

The Participant Flow refers to the Randomized Set Part A and Randomized Set Part B. Part A: P1, P2, P3, P4, P5, and P6 refer to period 1 to 6.

Participant milestones

Participant milestones
Measure	Part A: Treatment Sequence: ABC Participants received a single dose of UCB0599 180 milligrams (mg) capsule (reference) (Treatment A) under fasting conditions on Day 1 in Period (P) 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: ACB Participants received a single dose of UCB0599 180 mg capsule (reference) (Treatment A) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: BCA Participants received a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: BAC Participants received a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg capsule under fasting conditions (Treatment A) on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Period 4,5 and 6 (elevated gastric pH) esomeprazole 40 mg once daily was coadministered from day 14 to 33. Each treatment period was followed by a 4-day Washout Period.	Part A: Treatment Sequence: CAB Participants received a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: CBA Participants received a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part B: Treatment Sequence: Placebo 90 mg/Placebo 180 mg Participants received a single dose of UCB0599 matching placebo 90 mg capsule on Day 1 in Period 1, followed by a single dose of UCB0599 matching placebo 180 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a washout period of 4 days.	Part B: Treatment Sequence: UCB0599 90 mg/UCB0599 180 mg Participants received a single dose of UCB0599 90 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 180 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: Placebo 180 mg/Placebo 360 mg Participants received a single dose of UCB0599 matching placebo 180 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 matching placebo 360 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: UCB0599 180 mg/ UCB0599 360 mg Participants received a single dose of UCB0599 180 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 360 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence:Placebo 360 mg/Placebo 90 mg Participants received a single dose of UCB0599 matching placebo 360 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 matching placebo 90 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: UCB0599 360 mg/ UCB0599 90 mg Participants received a single dose of UCB0599 360 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 90 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.
Part A: P1 (Day 1, Normal Gastric pH) STARTED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P1 (Day 1, Normal Gastric pH) COMPLETED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P1 (Day 1, Normal Gastric pH) NOT COMPLETED	0	0	0	0	0	0	0	0	0	0	0	0
Part A: P2 (Day 6, Normal Gastric pH) STARTED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P2 (Day 6, Normal Gastric pH) COMPLETED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P2 (Day 6, Normal Gastric pH) NOT COMPLETED	0	0	0	0	0	0	0	0	0	0	0	0
Part A: P3 (Day 11, Normal Gastric pH) STARTED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P3 (Day 11, Normal Gastric pH) COMPLETED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P3 (Day 11, Normal Gastric pH) NOT COMPLETED	0	0	0	0	0	0	0	0	0	0	0	0
Part A: P4 (Day 19,Elevated Gastric pH) STARTED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P4 (Day 19,Elevated Gastric pH) COMPLETED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P4 (Day 19,Elevated Gastric pH) NOT COMPLETED	0	0	0	0	0	0	0	0	0	0	0	0
Part A: P5 (Day 24,Elevated Gastric pH) STARTED	7	7	7	7	7	7	0	0	0	0	0	0
Part A: P5 (Day 24,Elevated Gastric pH) COMPLETED	7	7	6	7	7	7	0	0	0	0	0	0
Part A: P5 (Day 24,Elevated Gastric pH) NOT COMPLETED	0	0	1	0	0	0	0	0	0	0	0	0
Part A: P6 (Day 29,Elevated Gastric pH) STARTED	7	7	6	7	7	7	0	0	0	0	0	0
Part A: P6 (Day 29,Elevated Gastric pH) COMPLETED	7	7	6	7	7	7	0	0	0	0	0	0
Part A: P6 (Day 29,Elevated Gastric pH) NOT COMPLETED	0	0	0	0	0	0	0	0	0	0	0	0
Part B- Period 1 (Day 1) STARTED	0	0	0	0	0	0	2	8	2	9	2	8
Part B- Period 1 (Day 1) Japnese Participants	0	0	0	0	0	0	1	4	1	4	1	4
Part B- Period 1 (Day 1) Chinese Participants	0	0	0	0	0	0	1	4	1	5	1	4
Part B- Period 1 (Day 1) COMPLETED	0	0	0	0	0	0	2	8	2	8	2	8
Part B- Period 1 (Day 1) NOT COMPLETED	0	0	0	0	0	0	0	0	0	1	0	0
Part B- Period 2 (Day 6) STARTED	0	0	0	0	0	0	2	8	2	8	2	8
Part B- Period 2 (Day 6) Japnese Participants	0	0	0	0	0	0	1	4	1	4	1	4
Part B- Period 2 (Day 6) Chinese Participants	0	0	0	0	0	0	1	4	1	4	1	4
Part B- Period 2 (Day 6) COMPLETED	0	0	0	0	0	0	2	8	2	8	2	8
Part B- Period 2 (Day 6) NOT COMPLETED	0	0	0	0	0	0	0	0	0	0	0	0

Reasons for withdrawal

Reasons for withdrawal
Measure	Part A: Treatment Sequence: ABC Participants received a single dose of UCB0599 180 milligrams (mg) capsule (reference) (Treatment A) under fasting conditions on Day 1 in Period (P) 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: ACB Participants received a single dose of UCB0599 180 mg capsule (reference) (Treatment A) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: BCA Participants received a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: BAC Participants received a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg capsule under fasting conditions (Treatment A) on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Period 4,5 and 6 (elevated gastric pH) esomeprazole 40 mg once daily was coadministered from day 14 to 33. Each treatment period was followed by a 4-day Washout Period.	Part A: Treatment Sequence: CAB Participants received a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: CBA Participants received a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part B: Treatment Sequence: Placebo 90 mg/Placebo 180 mg Participants received a single dose of UCB0599 matching placebo 90 mg capsule on Day 1 in Period 1, followed by a single dose of UCB0599 matching placebo 180 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a washout period of 4 days.	Part B: Treatment Sequence: UCB0599 90 mg/UCB0599 180 mg Participants received a single dose of UCB0599 90 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 180 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: Placebo 180 mg/Placebo 360 mg Participants received a single dose of UCB0599 matching placebo 180 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 matching placebo 360 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: UCB0599 180 mg/ UCB0599 360 mg Participants received a single dose of UCB0599 180 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 360 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence:Placebo 360 mg/Placebo 90 mg Participants received a single dose of UCB0599 matching placebo 360 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 matching placebo 90 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: UCB0599 360 mg/ UCB0599 90 mg Participants received a single dose of UCB0599 360 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 90 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.
Part A: P5 (Day 24,Elevated Gastric pH) Consent Withdrawn (not due to adverse event)	0	0	1	0	0	0	0	0	0	0	0	0
Part B- Period 1 (Day 1) Adverse Event	0	0	0	0	0	0	0	0	0	1	0	0

Baseline Characteristics

A Study to Test Bioavailability of of 2 New Formulations of UCB0599 in Healthy Participants in Part A and to Test Safety, Tolerability, and Pharmacokinetic (PK) of UCB0599 in Healthy Japanese and Chinese Participants in Part B

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Part A: Treatment Sequence: ABC n=7 Participants Participants received a single dose of UCB0599 180 milligrams (mg) capsule (reference) (Treatment A) under fasting conditions on Day 1 in Period (P) 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: ACB n=7 Participants Participants received a single dose of UCB0599 180 mg capsule (reference) (Treatment A) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: BCA n=7 Participants Participants received a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: BAC n=7 Participants Participants received a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg capsule under fasting conditions (Treatment A) on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Period 4,5 and 6 (elevated gastric pH) esomeprazole 40 mg once daily was coadministered from day 14 to 33. Each treatment period was followed by a 4-day Washout Period.	Part A: Treatment Sequence: CAB n=7 Participants Participants received a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part A: Treatment Sequence: CBA n=7 Participants Participants received a single dose of UCB0599 180 mg encapsulated tablet (Treatment C) under fasting conditions on Day 1 in Period 1 (normal gastric pH) and Day 19 in Period 4 (elevated gastric pH), followed by a single dose of UCB0599 180 mg non-encapsulated tablet (Treatment B) under fasting conditions on Day 6 in Period 2 (normal gastric pH) and Day 24 in Period 5 (elevated gastric pH), further followed by a single dose of UCB0599 180 mg capsule (Treatment A) under fasting conditions on Day 11 in Period 3 (normal gastric pH) and Day 29 in Period 6 (elevated gastric pH). In Periods 4, 5, and 6 (elevated gastric pH), esomeprazole 40 mg was coadministered once daily from Day 14 to Day 33. Each treatment period was followed by a 4-day Washout period.	Part B: Treatment Sequence: Pooled Placebo n=6 Participants Participants received UCB0599 matching placebo, 90 mg capsule, on Day 1 in Period 1 followed by UCB0599 matching placebo, 180 mg capsule, on Day 6 in Period 2; received UCB0599 matching placebo, 180 mg capsule, on Day 1 in Period 1 followed by UCB0599 matching placebo, 360 mg capsule, on Day 6 in Period 2; and UCB0599 matching placebo, 360 mg capsule, on Day 1 in Period 1 followed by UCB0599 matching placebo, 90 mg capsule, on Day 6 in Period 2. Arm sequences were pooled for placebo in Part B.	Part B: Treatment Sequence: UCB0599 90mg/UCB0599 180 mg n=8 Participants received a single dose of UCB0599 90 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 180 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: UCB0599 180 mg/ UCB0599 360 mg n=9 Participants Participants received a single dose of UCB0599 180 mg capsule on Day 1 in Period 1 followed by a single dose of UCB0599 360 mg capsule on Day 6 in Period 2 under fasting conditions. Periods 1 and 2 were separated by a wash out period of 4 days.	Part B: Treatment Sequence: UCB0599 360mg/ UCB0599 90mg n=8 Participants Participants received UCB0599 360 mg capsule, on Day 1 in Period 1 followed by UCB0599 90 mg capsule, on Day 6 in Period 2.	Total n=73 Participants Total of all reporting groups
Age, Categorical <=18 years	0 Participants n=18 Participants	0 Participants n=102 Participants	0 Participants n=30 Participants	0 Participants n=37 Participants	0 Participants n=127 Participants	0 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	0 Participants n=14 Participants
Age, Categorical Between 18 and 65 years	7 Participants n=18 Participants	7 Participants n=102 Participants	7 Participants n=30 Participants	7 Participants n=37 Participants	7 Participants n=127 Participants	7 Participants n=77 Participants	6 Participants n=37 Participants	8 Participants n=35 Participants	9 Participants n=15 Participants	8 Participants n=14 Participants	73 Participants n=14 Participants
Age, Categorical >=65 years	0 Participants n=18 Participants	0 Participants n=102 Participants	0 Participants n=30 Participants	0 Participants n=37 Participants	0 Participants n=127 Participants	0 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	0 Participants n=14 Participants
Age, Continuous	36.1 years STANDARD_DEVIATION 7.1 • n=18 Participants	42.6 years STANDARD_DEVIATION 7.4 • n=102 Participants	37.0 years STANDARD_DEVIATION 10.9 • n=30 Participants	30.9 years STANDARD_DEVIATION 5.5 • n=37 Participants	33.1 years STANDARD_DEVIATION 8.8 • n=127 Participants	31.9 years STANDARD_DEVIATION 8.7 • n=77 Participants	39.5 years STANDARD_DEVIATION 9.8 • n=37 Participants	39.3 years STANDARD_DEVIATION 7.9 • n=35 Participants	30.7 years STANDARD_DEVIATION 6.5 • n=15 Participants	40.1 years STANDARD_DEVIATION 9.0 • n=14 Participants	36.0 years STANDARD_DEVIATION 8.7 • n=14 Participants
Sex: Female, Male Female	4 Participants n=18 Participants	6 Participants n=102 Participants	3 Participants n=30 Participants	1 Participants n=37 Participants	3 Participants n=127 Participants	4 Participants n=77 Participants	1 Participants n=37 Participants	2 Participants n=35 Participants	1 Participants n=15 Participants	2 Participants n=14 Participants	27 Participants n=14 Participants
Sex: Female, Male Male	3 Participants n=18 Participants	1 Participants n=102 Participants	4 Participants n=30 Participants	6 Participants n=37 Participants	4 Participants n=127 Participants	3 Participants n=77 Participants	5 Participants n=37 Participants	6 Participants n=35 Participants	8 Participants n=15 Participants	6 Participants n=14 Participants	46 Participants n=14 Participants
Race/Ethnicity, Customized Asian	0 Participants n=18 Participants	0 Participants n=102 Participants	0 Participants n=30 Participants	0 Participants n=37 Participants	0 Participants n=127 Participants	0 Participants n=77 Participants	6 Participants n=37 Participants	8 Participants n=35 Participants	9 Participants n=15 Participants	8 Participants n=14 Participants	31 Participants n=14 Participants
Race/Ethnicity, Customized Black	3 Participants n=18 Participants	1 Participants n=102 Participants	1 Participants n=30 Participants	5 Participants n=37 Participants	1 Participants n=127 Participants	2 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	13 Participants n=14 Participants
Race/Ethnicity, Customized Native Hawaiian or other Pacific Islander	0 Participants n=18 Participants	0 Participants n=102 Participants	0 Participants n=30 Participants	0 Participants n=37 Participants	0 Participants n=127 Participants	0 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	0 Participants n=14 Participants
Race/Ethnicity, Customized White	4 Participants n=18 Participants	6 Participants n=102 Participants	6 Participants n=30 Participants	2 Participants n=37 Participants	5 Participants n=127 Participants	5 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	28 Participants n=14 Participants
Race/Ethnicity, Customized Other or Mixed	0 Participants n=18 Participants	0 Participants n=102 Participants	0 Participants n=30 Participants	0 Participants n=37 Participants	1 Participants n=127 Participants	0 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	1 Participants n=14 Participants
Race/Ethnicity, Customized Hispanic or Latino	3 Participants n=18 Participants	3 Participants n=102 Participants	3 Participants n=30 Participants	1 Participants n=37 Participants	3 Participants n=127 Participants	3 Participants n=77 Participants	0 Participants n=37 Participants	0 Participants n=35 Participants	0 Participants n=15 Participants	0 Participants n=14 Participants	16 Participants n=14 Participants
Race/Ethnicity, Customized Not Hispanic or Latino	4 Participants n=18 Participants	4 Participants n=102 Participants	4 Participants n=30 Participants	6 Participants n=37 Participants	4 Participants n=127 Participants	4 Participants n=77 Participants	6 Participants n=37 Participants	8 Participants n=35 Participants	9 Participants n=15 Participants	8 Participants n=14 Participants	57 Participants n=14 Participants

PRIMARY outcome

Timeframe: Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, 6, 11, 19, 24 and 29 in Part A

Population: Pharmacokinetic Set Part A (PKS A) included all randomized participants who received at least 1 total dose of study medication and have at least 1 observable PK measurement. Here, "number analyzed" signifies participants who were evaluable for specified categories.

Cmax was maximum (peak) observed drug concentration following a single dose administration of UCB0599 under normal and elevated gastric pH condition.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Maximum Plasma Concentration (Cmax) of UCB0599 in Part A Normal	876.2 nanograms per milliliter (ng/mL) Geometric Coefficient of Variation 30.2	724.6 nanograms per milliliter (ng/mL) Geometric Coefficient of Variation 39.4	618.0 nanograms per milliliter (ng/mL) Geometric Coefficient of Variation 38.2	—	—	—	—	—
Maximum Plasma Concentration (Cmax) of UCB0599 in Part A Elevated	449.3 nanograms per milliliter (ng/mL) Geometric Coefficient of Variation 54.9	694.4 nanograms per milliliter (ng/mL) Geometric Coefficient of Variation 43.8	631.4 nanograms per milliliter (ng/mL) Geometric Coefficient of Variation 42.8	—	—	—	—	—

PRIMARY outcome

Timeframe: Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, 6, 11, 19, 24 and 29 in Part A

Population: PKS A included all randomized participants who received at least 1 total dose of study medication and have at least 1 observable PK measurement. Here, "number analyzed" signifies participants who were evaluable for specified categories.

AUC(0-t) was area under the plasma concentration-time curve from time 0 to the last quantifiable concentration of UCB0599 under normal and elevated gastric pH condition.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Area Under the Plasma Concentration-time Curve From Time 0 to the Last Quantifiable Concentration (AUC(0-t)) of UCB0599 in Part A Normal	5774 hour nanograms per milliliter (h*ng/mL) Geometric Coefficient of Variation 35.5	5503 hour nanograms per milliliter (h*ng/mL) Geometric Coefficient of Variation 41.0	5324 hour nanograms per milliliter (h*ng/mL) Geometric Coefficient of Variation 43.1	—	—	—	—	—
Area Under the Plasma Concentration-time Curve From Time 0 to the Last Quantifiable Concentration (AUC(0-t)) of UCB0599 in Part A Elevated	5489 hour nanograms per milliliter (h*ng/mL) Geometric Coefficient of Variation 49.2	5779 hour nanograms per milliliter (h*ng/mL) Geometric Coefficient of Variation 43.9	5641 hour nanograms per milliliter (h*ng/mL) Geometric Coefficient of Variation 41.3	—	—	—	—	—

PRIMARY outcome

Timeframe: Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, 6, 11, 19, 24 and 29 in Part A

Population: PKS A included all randomized participants who received at least 1 total dose of study medication and have at least 1 observable PK measurement. Here, "overall number of participants analyzed" signifies participants who were evaluable for this outcome measure and "number analyzed" signifies participants who were evaluable for specified categories.

AUC inf was area under the plasma concentration-time curve from time 0 to infinity of UCB0599 under normal and elevated gastric pH condition.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=40 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=39 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Area Under the Plasma Concentration-time Curve From Time 0 to Infinity (AUC Inf) of UCB0599 in Part A Normal	5829 h*ng/mL Geometric Coefficient of Variation 36.8	5561 h*ng/mL Geometric Coefficient of Variation 42.3	5374 h*ng/mL Geometric Coefficient of Variation 44.5	—	—	—	—	—
Area Under the Plasma Concentration-time Curve From Time 0 to Infinity (AUC Inf) of UCB0599 in Part A Elevated	5538 h*ng/mL Geometric Coefficient of Variation 49.5	5835 h*ng/mL Geometric Coefficient of Variation 44.9	5720 h*ng/mL Geometric Coefficient of Variation 41.4	—	—	—	—	—

PRIMARY outcome

Timeframe: From Baseline (Day 1) to Safety Follow-up Period of Part B (up to Day 15)

Population: Safety Set Part B (SS B) included all study participants who were randomized and received full or partial study medication according to the treatment that the participants actually received.

An AE was any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study medication, whether or not considered related to the study medication. A TEAE was defined as AEs starting on/after the date/time of first treatment \& upto including 4 days after last treatment or any unresolved event already present before administration of treatment that worsens in intensity following exposure to treatment.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=3 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) n=8 Participants Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) n=3 Participants All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) n=9 Participants Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Percentage of Study Participants With Treatment-emergent Adverse Events (TEAEs) in Part B	33.3 percentage of participants	25.0 percentage of participants	0 percentage of participants	0 percentage of participants	33.3 percentage of participants	12.5 percentage of participants	33.3 percentage of participants	25.0 percentage of participants

PRIMARY outcome

Timeframe: From Baseline (Day 1) to Safety Follow-up Period of Part B (up to Day 15)

Population: SS B included all study participants who were randomized and received full or partial study medication according to the treatment that the participants actually received.

Serious TEAEs were any untoward medical incidence in a participant during administered study treatment, whether or not these events were related to study treatment and additionally were emergent untoward medical occurrence that at any dose: 1. Results in death 2. Is life-threatening 3. Required in patient hospitalisation or prolongation of existing hospitalisation 4. Results in persistent disability/incapacity 5. Was a congenital anomaly or birth defect 6. Important medical events

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=3 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) n=8 Participants Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) n=3 Participants All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) n=9 Participants Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Percentage of Study Participants With Serious Treatment-emergent Adverse Events (Serious TEAEs) in Part B	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants

PRIMARY outcome

Timeframe: From Baseline (Day 1) to Safety Follow-up Period of Part B (up to Day 15)

Population: SS B included all study participants who were randomized and received full or partial study medication according to the treatment that the participants actually received.

: An AE was any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study medication, whether or not considered related to the study medication. A TEAE was defined as AEs starting on/after the date/time of first treatment \& upto including 4 days after last treatment or any unresolved event already present before administration of treatment that worsens in intensity following exposure to treatment.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=3 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) n=8 Participants Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) n=3 Participants All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) n=9 Participants Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Percentage of Study Participants With Treatment-emergent Adverse Events (TEAEs) Leading to Withdrawal From Study in Part B	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants	0 percentage of participants

PRIMARY outcome

Timeframe: Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, and 6 in Part B

Population: Pharmacokinetic Set Part B (PKS B) included randomized participants who received at least 1 total dose of study medication and have at least 1 observable PK measurement.

Cmax was maximum (peak) observed drug concentration following a single dose administration of UCB0599.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) n=8 Participants Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) n=9 Participants All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Maximum Plasma Concentration (Cmax) of UCB0599 in Part B	502.5 ng/mL Geometric Coefficient of Variation 29.8	602.9 ng/mL Geometric Coefficient of Variation 42.4	1757 ng/mL Geometric Coefficient of Variation 36.4	483.2 ng/mL Geometric Coefficient of Variation 42.6	737.5 ng/mL Geometric Coefficient of Variation 35.7	1525 ng/mL Geometric Coefficient of Variation 24.8	—	—

PRIMARY outcome

Timeframe: Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, and 6 in Part B

Population: The PKS B included randomized participants who received at least 1 total dose of study medication and have at least 1 observable PK measurement.

AUC(0-t) was area under the plasma concentration-time curve from time 0 to the last quantifiable concentration of UCB0599.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) n=8 Participants Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) n=9 Participants All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Area Under the Plasma Concentration-time Curve From Time 0 to the Last Quantifiable Concentration (AUC(0-t)) of UCB0599 in Part B	3363 h*ng/mL Geometric Coefficient of Variation 29.5	5242 h*ng/mL Geometric Coefficient of Variation 23.6	12010 h*ng/mL Geometric Coefficient of Variation 36.5	3795 h*ng/mL Geometric Coefficient of Variation 23.5	6689 h*ng/mL Geometric Coefficient of Variation 28.6	14020 h*ng/mL Geometric Coefficient of Variation 25.2	—	—

PRIMARY outcome

Timeframe: Predose and at 0.25, 0.5, 1, 1.5, 2, 4, 8, 12, 24, 36, 48, 72, and 96 hours after UCB0599 administration on Days 1, and 6 in Part B

Population: The PKS B included randomized participants who received at least 1 total dose of study medication and have at least 1 observable PK measurement. Here, "overall number of participants analyzed" signifies participants who were evaluable for this outcome measure.

AUC inf was area under the plasma concentration-time curve from time 0 to infinity of UCB0599.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=6 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=8 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) n=8 Participants Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) n=9 Participants All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) n=8 Participants Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Area Under the Plasma Concentration-time Curve From Time 0 to Infinity (AUC (Inf)) of UCB0599 in Part B	3425 h*ng/mL Geometric Coefficient of Variation 29.6	5151 h*ng/mL Geometric Coefficient of Variation 27.5	12100 h*ng/mL Geometric Coefficient of Variation 36.7	3847 h*ng/mL Geometric Coefficient of Variation 23.2	6741 h*ng/mL Geometric Coefficient of Variation 28.5	14070 h*ng/mL Geometric Coefficient of Variation 25.1	—	—

SECONDARY outcome

Timeframe: From Baseline (Day 1) to Safety Follow-up Period of Part A (up to Day 39)

Population: Safety Set Part A (SS A) included all study participants who were randomized and received full or partial study medication according to the treatment that the participants actually received.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Percentage of Study Participants With Treatment-emergent Adverse Events (TEAEs) in Part A	38.1 percentage of participants	31.0 percentage of participants	35.7 percentage of participants	—	—	—	—	—

SECONDARY outcome

Timeframe: From Baseline (Day 1) to Safety Follow-up Period of Part A (up to Day 39)

Population: SS A included all study participants who were randomized and received full or partial study medication according to the treatment that the participants actually received.

Outcome measures

Outcome measures
Measure	Part A: UCB0599: Capsule 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg capsule under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), Day 29 in Period 6 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), and Day 24 in Period 5 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg capsule in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Non-encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg non-encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg non-encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part A: UCB0599: Encapsulated Tablet 180 mg n=42 Participants All participants who received a single dose of UCB0599 180 mg encapsulated tablet under fasting conditions on Day 1 in Period 1 (normal gastric pH), Day 19 in Period 4 (elevated gastric pH), Day 6 in Period 2 (normal gastric pH), Day 24 in Period 5 (elevated gastric pH), Day 11 in Period 3 (normal gastric pH), and Day 29 in Period 6 (elevated gastric pH). Esomeprazole was coadministered with UCB0599 180 mg encapsulated tablet in Treatment Periods 4, 5, and 6 (elevated gastric pH).	Part B: UCB0599 360 mg (Japanese Participants) Japanese participants who received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: Pooled Placebo (Chinese Participants) All the Chinese participants who received placebo (matching to UCB0599 90 mg, 180 mg, 360 mg) on Day 1 of Period 1 and Day 6 of Period 2. Pooled data is reported for the placebo group.	Part B: UCB0599 90 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 90 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 180 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 180 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.	Part B: UCB0599 360 mg (Chinese Participants) Chinese participants received a single dose of UCB0599 360 mg capsule on Day 1 of Period 1 and Day 6 of Period 2. Period 1 and Period 2 were separated by a washout period of 4 days.
Percentage of Study Participants With Serious Treatment-emergent Adverse Events (TEAEs) in Part A	0 percentage of participants	0 percentage of participants	0 percentage of participants	—	—	—	—	—

SECONDARY outcome

Timeframe: From Baseline (Day 1) to Safety Follow-up Period of Part A (up to Day 39)

Population: SS A included all study participants who were randomized and received full or partial study medication according to the treatment that the participants actually received.