FDA Rejects Sobi's Gout Drug 'NASP' Due to Issues with Contract Manufacturing Facility
The FDA has issued a Complete Response Letter (CRL) for NASP (developmental name SEL-212), a new gout treatment from Swedish Orphan Biovitrum AB (Sobi), effectively rejecting its approval. The primary reason for the rejection is not related to clinical efficacy or safety, but rather to deficiencies identified in the manufacturing process and quality control (CMC) at the contract manufacturing organization (CMO). The FDA has requested additional data regarding the manufacturing control strategy for the active biological ingredient in NASP. Sobi stated that these issues are readily addressable and that they will work closely with the FDA to expedite the resubmission process.
This FDA decision temporarily protects Amgen's market-leading drug, Krystexxa (pegoliticase), in the gout treatment market. Krystexxa generated approximately USD 1.34 billion in US sales in 2025. The delay in the launch of NASP provides Amgen with additional time to defend its market share. NASP was considered a strong contender to challenge Krystexxa's dominance, so this regulatory delay means that the market will likely remain dominated by Amgen for the foreseeable future.
NASP offers improved convenience with its mechanism of action, which involves sequentially administering nanoencapsulated sirolimus (to prevent anti-drug antibody formation) and pegadricase (to break down uric acid). Unlike Krystexxa, which requires bi-weekly administration and weekly co-administration of the immunosuppressant methotrexate, NASP requires only monthly administration and has demonstrated sufficient uric acid-lowering effects. NASP could have been a valuable alternative for patients with severe liver and kidney disease who cannot take methotrexate, but this approval delay means that these patients will have to wait several more months to access this treatment option.
Although the regulatory approval of NASP has been delayed, Sobi is diversifying its gout portfolio by acquiring Arthrosi Therapeutics for up to USD 1.5 billion, which includes another gout pipeline product, pozdeutinurad. Pozdeutinurad is an oral uric acid transporter 1 (URAT1) inhibitor that is taken once daily and has recently shown very positive topline results in a Phase 3 trial (Reduce-2). Sobi estimates that pozdeutinurad could generate peak sales of over 1 billion Swedish krona (approximately USD 1.03 billion), so even with the CMC issues with NASP, the company's long-term growth prospects remain strong.
The FDA's rejection of NASP approval will temporarily extend the market dominance of Amgen's Krystexxa (AMGN) in the approximately USD 3.2 billion annual gout market, with Krystexxa generating USD 1.34 billion in US sales in 2025. This case, where a drug that has passed Phase 3 trials is delayed due to CMC deficiencies at the CMO, highlights that control over the manufacturing process is as critical as clinical data in determining the value of a biotech company. While Sobi (SOBIVO) will experience a delay in achieving its projected peak sales of USD 410-620 million for NASP, the recent acquisition of Arthrosi for up to USD 1.5 billion and the positive Phase 3 results for pozdeutinurad are strengthening its mid- to long-term portfolio. Complex combination drugs like NASP, which include immunomodulatory functions, require meticulous management of production process documentation and CMO relationships from the early stages of development to mitigate the risk of commercialization timeline delays.