Long-term Safety and Efficacy of Odevixibat in Patients With Alagille Syndrome

Inclusion Criteria:

Cohort 1 :

1. Completion of the 24-week Treatment Period of Study A4250-012

2. Signed informed consent and assent as appropriate. Patients who turn 18 years of age (or legal age per country) during the study will be required to re-consent to remainon the study

3. Caregivers (and age-appropriate patients) must be willing and able to use anelectronic diary (eDiary) device as required by the study

4. Sexually active males and females must agree to use a reliable contraceptive methodwith ≤1% failure rate (such as hormonal contraception, intra-uterine device, orcomplete abstinence) from signed informed consent through 90 days after last dose ofstudy drug.

Cohort 2 :

1. Infant with clinically confirmed ALGS , ≤11 months of age at Study Day 1

2. Body weight ≥2 kg at Study Day 1

3. Gestational age ≥36 weeks. For children born with gestational age between 32 and 36weeks, a postmenstrual age of ≥36 weeks is required .

4. Signed parent/legal guardian informed consent.

Exclusion Criteria:

Cohort 1 :

1. Decompensated liver disease, history or presence of clinically significant ascites,variceal hemorrhage, and/or encephalopathy

2. Patients who were not compliant with study drug treatment or procedures in StudyA4250-012

3. Any other conditions or abnormalities which, in the opinion of the investigator, maycompromise the safety of the patient, or interfere with the patient participating inor completing the study

4. Known hypersensitivity to any components of odevixibat

Cohort 2 :

1. Patient with past medical history or ongoing presence of other types of liverdisease including, but not limited to, the following:

2. Biliary atresia of any kind

3. Progressive familial intrahepatic cholestasis (PFIC)

4. Benign recurrent intrahepatic cholestasis

5. Patient with a past medical history or ongoing presence of any other disease orcondition known to interfere with the absorption, distribution, metabolism (specifically bile acid metabolism), or excretion of drugs in the intestine,including but not limited to, inflammatory bowel disease

6. Patient with past medical history or ongoing chronic diarrhea requiring intravenousfluid or nutritional intervention for treatment of the diarrhea and/or its sequelae

7. Patient has a confirmed past diagnosis of infection with human immunodeficiencyvirus or other present and active, clinically significant chronic infection

8. Recent infection requiring hospitalization or treatment with parenteralanti-infective within 4 weeks of Study Day 1 or completion of oral anti-infectivetreatment within 2 weeks prior to the Screening Visit

9. Cancer diagnosis (except for basal cell carcinoma)

10. Chronic kidney disease with an impaired renal function and a glomerular filtrationrate <70 mL/min/1.73 m2

11. Patient with surgical history of disruption of the enterohepatic circulation (biliary diversion surgery) within 6 months prior to the Screening Visit

12. Patient has had a liver transplant, or a liver transplant is planned within 6 monthsof Study Day 1

13. Decompensated liver disease, history or presence of clinically significant ascites,variceal hemorrhage, and/or encephalopathy

14. International normalized ratio (INR) >1.4 (the patient may be treated with VitaminK, and if INR is ≤1.4 at resampling the patient may be enrolled)

15. Serum alanine aminotransferase (ALT) >10 × upper limit of normal (ULN) at Screening

16. Serum ALT >15 × ULN at any time point during the last 6 months unless an alternateetiology was confirmed for the elevation

17. Total bilirubin >15 × ULN at Screening

18. Patient suffers from uncontrolled, recalcitrant pruritic condition other than ALGS.Examples include, but not limited to, refractory atopic dermatitis or other primarypruritic skin diseases.

19. Patient exposed to alcohol or substance abuse in utero

20. Bile acid or lipid binding resins and medications that slow gastrointestinalmotility

21. Patient has had investigational exposure to a drug, biologic agent, or medicaldevice within 30 days prior to the Screening Visit, or 5 half-lives of the studyagent, whichever is longer

22. Any other conditions or abnormalities which, in the opinion of the investigator maycompromise the safety of the patient, or interfere with the patient participating inor completing the study