Applicable to all patients: - Male or female, at least 18 years of age; able to understand the purpose and risks of the program, and provides written informed consent to participate. - Not eligible for or otherwise able to obtain access to avexitide via a clinical trial, and does not have access to satisfactory, alternative treatment options. - If female, cannot be breastfeeding or lactating, and if of childbearing potential must agree to use a highly effective method of birth control during EAP participation. A negative urine pregnancy test is required at time of entry. - If male, must agree to use a highly effective method of birth control during EAP participation. For Category A: - Have completed the LUCIDITY trial through the Week 48 OLE Part B end-of-treatment visit on avexitide. For Category B: - Have clinical diagnosis of PBH, and underwent documented RYGB ≥ 12 months prior to EAP eligibility assessment. - Has body mass index (BMI) of up to 40 kg/m2. - Treating physician confirmation of either participation in previous avexitide clinical trials conducted in PBH following RYGB; or documented LUCIDITY participant who signed ICF and was eligible for LUCIDITY based on screening and run-in, but was unable to be randomized due to completion of recruitment.

Applicable to all patients: - Use of GLP-1 receptor agonists, glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor dual agonists, and other GLP-1 receptor agonist combination therapies. - Presence of any clinically relevant condition which, per the judgment of the treating physician, may preclude the patient from safe treatment. For Category B: - Have received another investigational drug for any indication within 5 half-lives of that drug or have participated in another interventional clinical study within 30 days prior to entry visit. - History of upper GI surgery affecting RYGB anatomy or function, other than RYGB. - Any known or suspected allergy to the investigational medicinal product (avexitide) or any related product (e.g., exenatide). - Abnormal liver function defined as AST and/or ALT > 5 times the upper limit of the normal and/or bilirubin level >3 times the upper limit of the normal within 12 weeks from entry. - Renal impairment, defined as an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m2 within 12 weeks from entry. - History or presence of insulinoma or other cause of endogenous hyperinsulinism other than PBH. - Presence of acute or chronic pancreatitis, history of idiopathic acute pancreatitis, or pancreatic cancer.