The purpose of this study is to determine the efficacy and safety of ALLN-177 in patients with enteric hyperoxaluria.

This is a phase 3, multicenter, randomized, double-blind, placebo-controlled study. This study is designed to determine whether treatment with ALLN-177 for 28 days can reduce urinary oxalate excretion in patients with enteric hyperoxaluria and to evaluate the safety of ALLN-177 in this patient population compared to placebo.

Inclusion Criteria:

1. Provided informed consent
2. Age 18 or older
3. History of hyperoxaluria secondary to a known underlying enteric disorder associated with malabsorption (e.g., bariatric surgery, Crohn's disease, short bowel syndrome, or other malabsorption syndrome)
4. Urinary Oxalate ≥ 50mg/24h

Exclusion Criteria:

1. Acute renal failure or estimated glomerular filtration rate (eGFR) < 30mL/min/1.73 m2
2. Unable or unwilling to discontinue Vitamin C supplementation