Evaluate the safety, tolerability, and efficacy of 28 days of treatment with ALLN-177 for reducing urinary oxalate excretion in patients with secondary hyperoxaluria and kidney stones.

This is a multicenter, randomized, double-blind, placebo controlled study to evaluate the efficacy of ALLN 177 compared with placebo in reducing the urinary excretion of oxalate in subjects with secondary hyperoxaluria and kidney stones. ALLN-177 is an orally administered form of oxalate decarboxylase. The goal of therapy with ALLN-177 is to reduce urinary oxalate excretion by decreasing the absorption of oxalate from the gastrointestinal tract.

Eligible subjects will be randomized to 28 days of treatment with ALLN-177 (7,500 units) or placebo three times daily with meals. Urinary oxalate excretion will be assessed by 24-hr urine collections throughout the study.

The study allows for approximately 66 subjects. The number of enrolled subjects may be increased to a maximum of 100 following an interim analysis.

Inclusion Criteria:

• History of enteric or idiopathic hyperoxaluria or kidney stones
• Urinary oxalate ≥ 50 mg/24 hours

Exclusion Criteria:

• Hyperuricosuria
• Glomerular filtration rate < 45 mL/min/1.73m2
• Hypercalcemia or hyperthyroidism
• Autoimmune disorder requiring systemic steroids
• Acute renal colic, primary hyperoxaluria, pure uric acid and/or cysteine stones, renal tubular acidosis, chronic urinary tract infection, or acute renal failure