A Study of BMN 255 in Participants With Non-Alcoholic Fatty Liver Disease And Hyperoxaluria

1. History of NAFLD with a liver fat content ≥ 8.0%, as determined by Fibroscan (transient elastography) or magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) during screening.
2. Hyperoxaluria, as defined by 24-hour urine oxalate excretion ≥ 45 mg/24 hours/1.73m2 at 2 independent assessments during screening. The pre-dose 24-hour urine oxalate measure at Day 1 will be used for baseline but will not be required for inclusion in the study
3. History of kidney stones (at least 1 stone prior to screening based on medical history); participants with a known personal or family history of cystinuria or cystine kidney stones, calcium phosphate stones, struvite stones, or urate stones should not be included.
4. Contraceptive use by men and women use throughout the study period
5. Participants must be capable of giving signed informed consent

Exclusion Criteria:

1. Clinical history (including family history) or genetic analyses consistent with primary hyperoxaluria (Type 1, 2, or 3).
2. History or current evidence of inflammatory bowel disease (including, but not limited to: Crohn's disease, ulcerative colitis, celiac disease / gluten-sensitive enteropathy) or evidence of chronic fat malabsorption (steatorrhea) due to any cause (eg, pancreatic insufficiency).
3. Significant history or clinical manifestation of any other allergic, dermatological, hepatic, renal, hematological, pulmonary, cardiovascular, gastrointestinal, neurological, respiratory, endocrine, or psychiatric disorder, as determined by the investigator. Participants with Type II diabetes will be permitted to enroll but must meet the concomitant therapy requirements listed below.

4. Use or intend to use any prescription medications/products within 14 days prior to Period 1 check-in, other than permitted oral medications to treat controlled hypertension, dyslipidemia and/or to lower triglycerides, and oral anti-hyperglycemic agents (AHAs), including, but not limited to, metformin, sulfonylureas, and dipeptidyl peptidase IV (DPP-IV) inhibitors, if approved by the investigator. Participants who require insulin injections, glucagon-like peptide-1 agonists, pioglitazone, or vitamin E ≥ 800 mg should not be included in the study.

   Note: Participants receiving lipid-modifying therapies and participants with controlled hypertension and/or diabetes must have been on a stable treatment regimen (medication, dose strength, dose interval) for 12 weeks prior to screening and no change in that regimen should be anticipated for the entire duration of this study (ie, from screening to final follow-up visit).

5. Confirmed diagnosis or NASH or evidence of hepatic cirrhosis, based on clinical assessment (eg, physical examination), historical liver biopsy or other prior imaging study, or a liver stiffness value ≥ 14 kPa during the FibroScan® examination at screening.