FDA Issues Complete Response Letter to Sobi for Gout Therapy NASP Over Manufacturing Deficiencies
On June 26, 2026, Swedish Orphan Biovitrum AB (Sobi) announced that the U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) regarding the company’s Biologics License Application (BLA) for NASP (nanoencapsulated sirolimus plus pegadricase) for the treatment of adult patients with uncontrolled gout.
The CRL represents a regulatory delay for Sobi's highly anticipated gout therapy, which is positioned to challenge Amgen's blockbuster gout drug Krystexxa. Crucially, the FDA's rejection was entirely focused on manufacturing issues rather than clinical outcomes:
- The FDA requested additional data related to the chemistry, manufacturing, and controls (CMC), specifically the manufacturing control strategy of the biological component of NASP.
- The FDA cited deficiencies at contract manufacturing facilities.
- The Agency identified no clinical safety or efficacy concerns that impact the approvability of NASP.
Lydia Abad-Franch, MD, MBA, Chief Medical Officer at Sobi, emphasized the company's commitment to resolving the issues:
"Sobi will 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 deficiencies... We continue to believe strongly in NASP’s potential to address the significant unmet need faced by people living with uncontrolled gout."
NASP is a novel two-component infusion therapy administered every four weeks. It combines tolerogenic nanoencapsulated sirolimus (NAS)—which acts as a built-in immunomodulator to prevent the formation of anti-drug antibodies (ADAs)—with pegadricase, a uricase enzyme that rapidly reduces serum uric acid (sUA) levels. The prevention of ADAs is a key differentiator, as antibody formation often limits the long-term effectiveness of current uricase therapies. Sobi will now work with its third-party manufacturing partners to resolve the FDA's concerns before resubmitting the BLA.