FDA Issues CRL for Oxylanthanum Carbonate in Hyperphosphatemia for CKD Patients on Dialysis

The US Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) to Unicycive Therapeutics for oxylanthanum carbonate (OLC) in the treatment of hyperphosphatemia in patients with chronic kidney disease (CKD) on dialysis.¹

The decision, announced on June 30, 2026, by Unicycive Therapeutics, is based on deficiencies previously identified at a third-party manufacturing vendor, with the company noting an FDA inspection of the third-party facility did not occur during the New Drug Application (NDA) resubmission review. According to the announcement, the FDA did not raise any concerns regarding clinical efficacy or safety data and no additional data was requested from Unicycive Therapeutics.

“We remain confident in the efficacy and safety of OLC,” said Shalabh Gupta, MD, chief executive officer of Unicycive Therapeutics. “We are in active and ongoing discussion with the FDA regarding label and packaging, and we are optimistic that there will be a successful inspection of the third-party manufacturing vendor and that we will be able to expeditiously resubmit the NDA.”

Clinical Data Supporting the NDA

The NDA was supported by 3 clinical studies: a phase 1 pharmacokinetic study in healthy volunteers, a bioequivalence study comparing OLC with reference lanthanum carbonate, and a tolerability study in patients with CKD receiving dialysis.¹

The FDA previously issued a Complete Response Letter for OLC in June 2025 because of manufacturing deficiencies identified during an inspection of a third-party manufacturing facility. The company stated at the time that the agency did not identify concerns related to the drug's preclinical, clinical, or safety data, and the current approval resolves that regulatory review process.^1,2

According to the June 30, 2026, announcement, the latest communication received by the company from the FDA occurred on June 29, and they are actively engaged in labeling discussions.¹

What OLC Offers Patients With CKD on Dialysis

Hyperphosphatemia is a common complication of end-stage renal disease (ESRD) requiring dialysis. Reduced renal phosphate clearance leads to elevated serum phosphorus, contributing to secondary hyperparathyroidism, vascular calcification, cardiovascular complications, and increased hospitalization risk. Although more than 450,000 people in the United States require pharmacologic phosphate management each year, maintaining target phosphate levels remains challenging for many patients.¹

A major contributor to that challenge is treatment adherence. Conventional phosphate binders are typically taken with every meal and snack, adding substantially to the medication burden already faced by patients on dialysis. OLC uses a proprietary nanoparticle formulation intended to reduce pill burden through smaller tablets and fewer tablets than existing lanthanum carbonate formulations while maintaining phosphate-binding efficacy.¹

That formulation advantage was reflected in phase 2 patient-reported outcomes presented at the National Kidney Foundation Spring Clinical Meetings in April 2025. Patients reported greater treatment satisfaction with OLC than with their previous phosphate-lowering therapy and identified tablet size and pill count as the primary barriers to consistent phosphate binder use. Whether these improvements translate into sustained phosphate control in routine clinical practice remains to be established, but the findings suggest the formulation may address an important contributor to non-adherence.³

Where OLC Could Fit in the Current Treatment Landscape

Available phosphate binders include calcium-based agents, sevelamer carbonate (Renvela), and lanthanum carbonate (Fosrenol), among others. OLC enters this landscape as a nanoparticle formulation of lanthanum carbonate intended to reduce tablet size and pill burden while maintaining the phosphate-binding properties of the reference compound.³

For nephrologists, OLC may provide an additional treatment option for patients whose phosphate control has been limited by the burden of existing binder regimens. Whether the formulation's adherence advantages translate into improved long-term phosphate control or clinical outcomes will require additional postmarketing data and real-world experience, and head-to-head comparative studies against currently approved phosphate binders have not yet been reported.³

References

1. Unicycive Therapeutics. Unicycive Therapeutics Receives Complete Response Letter from FDA Regarding Resubmitted Oxylanthanum Carbonate (OLC) New Drug Application (NDA). Unicycive Therapeutics, Inc. Published June 30, 2026. Accessed June 30, 2026. https://ir.unicycive.com/news/detail/123/unicycive-therapeutics-receives-complete-response-letter

2. Brooks A. FDA Accepts Oxylanthanum Carbonate NDA Resubmission for Hyperphosphatemia in CKD, Dialysis. Hcplive.com. Published January 29, 2026. Accessed June 30, 2026. https://www.hcplive.com/view/fda-accepts-oxylanthanum-carbonate-nda-resubmission-for-hyperphosphatemia-in-ckd-dialysis

3. Brooks A. Oxylanthanum Carbonate May Offer Desirable Alternative to Current Phosphate Binders. HCPLive. April 10, 2025. https://www.hcplive.com/view/oxylanthanum-carbonate-may-offer-desirable-alternative-current-phosphate-binders