Efficacy and safety of Oxalobacter formigenes in patients with primary hyperoxaluria: A systematic review and meta-analysis of randomized controlled trials.

Background and objective: Primary hyperoxaluria (PH), a rare autosomal recessive disorder, results in defective metabolism of oxalate, leading to increased oxalate levels. Oxalobacter formigenes (O. formigenes) is a nonpathological anaerobic bacterium that uses oxalate for its survival and thus decreases the plasma oxalate levels. We aimed to use randomized controlled trials (RCTs) to evaluate the efficacy of O. formigenes in treating PH.

Methods: A literature review was conducted for synthesizing the evidence from RCTs on Scopus, Web of Science, Embase, PubMed, and CENTRAL until January 2023. The outcomes were pooled using mean difference (MD) for continuous data and odds ratios (OR) for dichotomous data along with confidence interval (CI). The systematic review is registered with Prospero ID CRD42023404421.

Results: We included five RCTs with 208 patients. The pooled analysis did not favor O. formigenes over placebo in reducing the plasma oxalate levels (MD: -0.00 mmol/day; 95% CI: [ - 0.01-0.00]; P = 0.06). Similar results were observed for urinary oxalate levels (MD: -0.01 mmol/day; 95% CI: [ - 0.12-0.10]; P = 0.86). There were no significant adverse events (OR: 0.44; 95% CI: [0.14-1.39]; P = 0.16) or serious adverse events (OR: 0.80; 95% CI: [0.29-2.25]; P = 0.67).

Conclusion: O. formigenes was ineffective in reducing the serum and urine oxalate levels in patients with PH but has an acceptable safety profile. As PH is a relatively rare disease and few patients consent for the trials, stringent protocols are required in the future to achieve data accuracy pertinent for making conclusive recommendations on the efficacy of O. formigenes in patients with PH.