The purpose of this study is to evaluate the safety, tolerability, and efficacy of different doses of ALLN 177 for reducing urinary oxalate excretion in patients with secondary hyperoxaluria and recurrent 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 7 days of treatment with a dose ALLN-177 or placebo and following a washout period, crossed over to an alternate treatment. Urinary oxalate excretion will be assessed by 24-hr urine collections throughout the study.

The study allows for up to 60 subjects.

Inclusion Criteria:

• History of enteric or idiopathic hyperoxaluria and at least one kidney stone within the past 2 years
• Hyperoxaluria at screening
• May be taking drugs for the prevention of stone disease

Exclusion Criteria:

• Hyperuricosuria
• Glomerular filtration rate < 55 mL/min/1.73m2
• Hypercalcemia or hypothyroidism
• Obstructive uropathy, chronic urosepsis, renal failure, renal tubular acidosis, primary hyperparathyroidism, primary hyperoxaluria, pure uric acid and cystine stones, and/or medullary sponge kidney
• Treatment with cholestyramine
• Average daily dietary intake of oxalate <75 mg per day