The FDA has issued a Complete Response Letter (CRL) for Sobi’s NASP biologics application in uncontrolled gout, citing manufacturing and CMC deficiencies while raising no concerns about clinical safety or efficacy.
Written By: Nalam Karthik, PharmD
Reviewed By: Pharmacally Editorial Team
The U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) to Sobi for its Biologics License Application (BLA) for NASP (nanoencapsulated sirolimus plus pegadricase), an investigational therapy for adults with uncontrolled gout. The agency requested additional chemistry, manufacturing, and controls (CMC) information and remediation of deficiencies at contract manufacturing facilities but did not identify any clinical safety or efficacy issues that would affect the therapy’s approvability.
The regulatory setback delays potential approval but does not alter the positive clinical profile reported for NASP. Sobi plans to meet with the FDA to clarify the agency’s requirements before resubmitting the application.
NASP combines immune modulation with uric acid reduction
NASP is an investigational two-component infusion administered every four weeks. It combines nanoencapsulated sirolimus with pegadricase, a uricase enzyme that lowers serum uric acid.
The nanoencapsulated sirolimus component helps reduce the formation of anti-drug antibodies, a common challenge with biologic uricase therapies that can limit long-term treatment effectiveness. By maintaining enzyme activity, NASP aims to provide sustained reductions in serum uric acid in patients whose disease remains uncontrolled despite conventional oral urate-lowering therapies.
Uncontrolled gout affects an estimated 200,000 people in the United States. These patients continue to experience elevated serum uric acid levels, recurrent painful gout flares, and deposits of urate crystals known as tophi despite standard treatment. Persistent hyperuricemia can lead to irreversible joint damage and is associated with kidney, cardiovascular, and metabolic complications.
Clinical program supports efficacy without new safety concerns
According to the FDA’s CRL, the agency did not identify concerns related to NASP’s clinical efficacy or safety that would prevent approval. Instead, the review focused primarily on manufacturing controls for the biologic component and deficiencies at third-party contract manufacturing facilities.
Clinical studies have shown that NASP produced meaningful reductions in serum uric acid levels in adults with uncontrolled gout, supporting its potential as a treatment option for patients with limited therapeutic alternatives. Sobi did not report any new safety findings in connection with the FDA’s decision.
Company preparing for resubmission
Chief Medical Officer Lydia Abad-Franch, MD, MBA, said the company remains confident in NASP’s clinical value for patients with uncontrolled gout. She noted that the FDA’s feedback provides a clear and actionable roadmap for addressing the remaining manufacturing requirements.
Sobi will request a meeting with the FDA to review the CRL in detail and determine the most appropriate resubmission strategy. The company also plans to work closely with its contract manufacturing organizations to resolve the identified deficiencies.
If the manufacturing issues are successfully addressed, NASP could return to regulatory review without the need to resolve additional clinical efficacy or safety concerns, potentially accelerating the path toward approval.
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About the Writer
Nalam Karthik (LinkedIn) is a healthcare writer and PharmD graduate with interests in pharmacovigilance, drug safety, clinical data analysis, and quality assurance. He is passionate about translating clinical and pharmaceutical knowledge into accessible healthcare content while staying engaged with advancements in drug development and patient safety initiatives.