FDA issues CRL to Sobi’s NASP over manufacturing failings

Edited by Robert McTiernan··2 min read

Sweden-based Swedish Orphan Biovitrum AB (STO: SOBI) disclosed on June 26, 2026, that the US FDA issued a Complete Response Letter (CRL) for the company’s Biologics License Application (BLA) for NASP (nanoencapsulated sirolimus plus pegadricase) for the treatment of adult patients with uncontrolled gout. The FDA’s action delays a launch that Sobi projected could bring in SEK 4-6 billion in sales. The FDA identified no concerns regarding clinical efficacy or safety that affect approvability.

The FDA required Sobi to provide additional data primarily related to the manufacturing control strategy for the biological component of NASP and to address deficiencies identified at contract manufacturing facilities. The agency did not request new clinical studies, and the absence of safety or efficacy concerns narrows the resubmission scope to manufacturing-related documentation and facility remediation. Before the BLA can be approved, Sobi must satisfy the agency that the manufacturing control strategy for the biological component meets applicable standards and that the contract manufacturing organizations have addressed the cited deficiencies.

The manufacturing issues are particularly notable given the history of the asset. NASP originated as SEL-212 at Selecta Biosciences, which Sobi licensed in June 2020 for global rights excluding China. In November 2023, Selecta formally transferred ImmTOR manufacturing and clinical operations to Sobi, meaning the biological component manufacturing now flagged by the FDA had only been under Sobi’s contract manufacturing organization oversight for approximately two and a half years at the time of the CRL. Selecta subsequently merged with Cartesian Therapeutics and no longer exists as an independent entity. No prior CRLs have been issued for this BLA.

Uncontrolled gout affects an estimated 200,000 patients in the US who fail conventional urate-lowering therapy. The only approved intravenous uricase therapy is Amgen’s Krystexxa, whose clinical utility can be limited by immunogenicity. NASP was designed to improve treatment durability through immune tolerance induction.

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NASP combines nanoencapsulated sirolimus, which is intended to reduce anti-drug antibody formation, with pegadricase, a PEGylated uricase. The FDA’s manufacturing concerns relate to the biological component.

Sobi said it will request a meeting with the FDA to discuss the feedback and determine the appropriate steps toward resubmission. The company stated it will work with its contract manufacturing organisations to address the facility deficiencies. Chief Medical Officer Lydia Abad-Franch said the clinical data generated to date had demonstrated meaningful reductions in serum uric acid levels and that the FDA’s feedback provides a clear and actionable path forward. No resubmission timeline has been disclosed. The CRL does not affect Sobi’s other approved or marketed products. No timeline for resubmission has been disclosed.

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