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iStock, Alona Horkova Unicycive Therapeutics and Sobi received complete response letters for kidney disease and gout filings, respectively, after the FDA found fault with their manufacturing partners. Manufacturing has derailed two filings for FDA approval, with the agency hitting Unicycive Therapeutics with a second rejection on production grounds and also issuing a complete response letter to Sobi. A year ago, the FDA rejected Unicycive’s request for approval of oxylanthanum carbonate (OLC) for treating hyperphosphatemia in patients with chronic kidney disease on dialysis. The rejection reflected problems at a third-party manufacturing plant. Unicycive worked with a second vendor in preparation for refiling, only to stick with the original service provider in light of its progress toward compliance. That decision backfired. On Tuesday, Unicycive revealed that the FDA issued a complete response letter because of deficiencies previously identified at the third-party manufacturing vendor. The FDA has yet to inspect the vendor as part of its review of the approval filing, according to Unicycive. Unicycive refiled for approval in the belief that the vendor was making progress on the deficiencies identified by the FDA and demonstrating inspection readiness. The FDA discussed the vendor with Unicycive at a meeting in September and did not express any concerns about the third-party manufacturer’s progress, the biotech said. Manufacturing was a worry for investors, though. Last month, Guggenheim Securities analysts spoke to Unicycive CEO Shalabh Gupta after the biotech’s share price dropped 12.6% in the wake of comments by Vishnukant Bhutada, the managing director of contract manufacturing partner Shilpa Pharma. On an earnings call in May, Bhutada said Shilpa would complete Unicycive’s validation batches this quarter. The timeline “may have worried investors,” Guggenheim analysts said in a note last month, but Unicycive “stressed that this was likely a misunderstanding.” The validation batches were from a plant needed for later market expansion, with another facility supporting the initial launch, Unicycive told the analysts. Gupta remained confident that everything was on track for an on-time approval, the analysts said. On Tuesday, Gupta said in a statement that he is “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.” News of the complete response letter sent Unicycive’s share price down 47% to $4.09 in early trading Tuesday, although there is potential for the biotech to recover quickly. “Management says that the inspection has now been ‘assigned’ and should take place in the coming weeks,” Guggenheim analysts said in a note Tuesday. “Assuming that goes well, then the OLC NDA can be resubmitted shortly after that and will likely receive a two-month review, suggesting the product could still be approved later this year.” Unicycive’s news emerged days after Sobi revealed that the FDA rejected its request for approval of a gout drug on manufacturing grounds. The Swedish drugmaker applied for approval of nanoencapsulated sirolimus plus pegadricase (NASP) in adults with uncontrolled gout. The FDA issued a complete response letter and asked for additional data, Sobi said. The additional data mainly relate to the manufacturing control strategy of the biological component of NASP and to deficiencies at a contract manufacturing facility. Sobi plans to meet with the FDA to discuss the path to resubmission and work with the contract manufacturing organizations to address the deficiencies. Complete response letters Published FDA rejections point to manufacturing, data gaps as key stumbling blocks The FDA’s decision last year to make complete response letters public provides new insight into why therapies sometimes fail to get the regulatory greenlight. Analysts say the information could help sponsors refine their regulatory strategies. May 11, 2026 · 8 min read · Tristan Manalac Read more