A Study of TAK-625 for the Treatment of Alagille Syndrome (ALGS)

Inclusion Criteria:

1. The participant is Japanese male or female with a body weight >=3.0 kilograms (kg) and who is >=1 month of age at the time of informed consent.
2. The participant is diagnosed with ALGS.

The participant has one or more of the following evidences of cholestasis:

1. Total serum bile acid (sBA) >3^ upper limit of the normal range (ULN) for age.
2. Direct bilirubin (conjugated) >1 mg/dL.
3. Lipid soluble vitamin (LSV) deficiency otherwise unexplainable.
4. Gamma-glutamyl transferase (GGT) >3^ ULN for age.
5. Intractable pruritus explainable only by liver disease.
6. The participant is expected to have a consistent caregiver(s) for the duration of the study.
7. The participant has an access to phone for scheduled calls from study site.
8. Both a caregiver and participant above the age of assent are capable of reading and understanding the questionnaires.
9. Caregivers (and age-appropriate participants) must be willing and able to use an eDiary device during the study.
10. Caregivers (and age-appropriate participants) must complete at least 10 eDiary reports (morning or evening) during each of 2 consecutive weeks of the screening period (maximum possible reports=14 per week), even if the participant is an adult (over 18 years old).
11. Average daily score >2 on the ItchRO questionnaire (maximum possible daily score of 4) for 2 consecutive weeks in the screening period, prior to dosing. A daily score is the higher of the scores for the morning and evening ItchRO. The average daily score is the sum of all daily scores divided by the number of days the ItchRO was completed. Since it is difficult to evaluate pruritus in infants, participants <12 months of age at screening whose pruritus is unavoidably difficult to be evaluated are not necessarily required to meet the above score.

Exclusion Criteria:

1. The participant has chronic diarrhea requiring ongoing intravenous (IV) fluid or nutritional intervention.
2. The participant has a previous history of surgical interruption of the enterohepatic circulation.
3. The participant has a previous liver transplant.
4. The participant decompensated cirrhosis (ALT >15^ ULN, international normalized ratio [INR] >1.5 [unresponsive to vitamin K therapy], albumin <3.0 g/dL, history or presence of clinically significant ascites, variceal hemorrhage, and/or encephalopathy).
5. The participant has a history or presence of other concomitant liver disease.
6. The participant has a history or presence of any other disease or condition known to interfere with the absorption, distribution, metabolism, or excretion of drugs, including bile salt metabolism in the intestine (eg, inflammatory bowel disease).
7. The participant has a history or presence of gallstones or kidney stones.
8. The participant has a possible malignant liver mass in imaging, including screening ultrasound.
9. The participant has cancers, except for in situ carcinoma, or cancers treated at least 5 years prior to screening with no evidence of recurrence.
10. The participant has received bile acid/lipid binding resins or IBAT inhibitors within 28 days prior to screening and throughout the trial.
11. The participant who has received sodium phenylbutyrate for less than 6 months at the initiation of screening.