FDA Issues Complete Response Letter for Sobi's Gout Therapy NASP, Citing Manufacturing Issues Only
Key Insights
The FDA issued a Complete Response Letter to Sobi for its BLA for NASP (nanoencapsulated sirolimus plus pegadricase) (search) for uncontrolled gout (search), requesting additional CMC and manufacturing facility data.
No clinical safety or efficacy concerns were identified that impact approvability, and the FDA's feedback provides what Sobi's CMO called "a clear and actionable path forward."
NASP is a novel every-4-week infusion therapy combining tolerogenic nanoencapsulated sirolimus with pegadricase, designed to reduce serum uric acid in patients with uncontrolled gout (search).
Swedish Orphan Biovitrum AB (Sobi) announced on June 26, 2026 that the U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) for the company's Biologics License Application (BLA) for NASP (nanoencapsulated sirolimus plus pegadricase) (search), an investigational therapy for adult patients with uncontrolled gout (search).
The FDA's letter requested additional data primarily related to the manufacturing control strategy of the biological component of NASP and asked the company to address deficiencies identified at contract manufacturing facilities. Critically, the agency raised no concerns regarding the clinical efficacy or safety of NASP that would impact approvability.
"We continue to believe strongly in NASP's potential to address the significant unmet need faced by people living with uncontrolled gout (search)," said Lydia Abad-Franch, MD, MBA, Chief Medical Officer at Sobi. "The clinical data generated to date have demonstrated meaningful reductions in serum uric acid levels in patients with uncontrolled gout. The FDA's feedback provides a clear and actionable path forward and we will work closely with them towards a resubmission. We remain committed to bringing NASP to patients."
Sobi intends to request a meeting with the FDA to discuss the feedback, determine the appropriate steps toward resubmission, and work with the contract manufacturing organizations to address the identified deficiencies.
The Burden of Uncontrolled Gout
Gout is the most common form of inflammatory arthritis, with more than 12 million people in the United States having been diagnosed. The condition is caused by elevated levels of uric acid in the body that accumulate around joints and other tissues, resulting in flares that cause intense pain.
Approximately 200,000 people in the United States suffer from uncontrolled gout (search), defined by serum uric acid (sUA) levels above 6 mg/dL and persistent, debilitating flares and/or tophi despite treatment with oral urate-lowering therapies. Elevated sUA levels have also been associated with diseases of the heart, vascular system, metabolism, kidney, and joint damage.
NASP: A Novel Dual-Component Approach
NASP is a novel, investigational medicine designed to reduce serum uric acid levels in people living with uncontrolled gout (search). By lowering uric acid, the therapy may help reduce harmful urate deposits in tissues, which, when left untreated, can lead to irreversible joint damage, increased cardiometabolic and renal comorbidities, and substantial quality-of-life burden.
The therapy is administered every 4 weeks as a sequential, two-component, infusion therapy with a built-in immunomodulator. It consists of tolerogenic nanoencapsulated sirolimus (NAS), which mitigates the formation of anti-drug antibodies (ADAs), and a uricase component, pegadricase (P), which reduces serum uric acid.
Path Forward
With no clinical safety or efficacy concerns raised by the FDA, the regulatory path for NASP remains clearly defined. Sobi's next steps include engaging with the FDA to align on the requirements for resubmission and addressing the manufacturing-related observations. The company has expressed continued confidence in the program and its commitment to delivering the therapy to the approximately 200,000 U.S. patients living with uncontrolled gout (search) who currently have limited treatment options.