Swedish Orphan Biovitrum (Sobi) has received a complete response letter from the US Food and Drug Administration (FDA) regarding its biologics licence application for nanoencapsulated sirolimus plus pegadricase (NASP), an investigational therapy intended for adults with uncontrolled gout.
The FDA has requested further information, primarily focusing on the manufacturing control strategy of the biological component of NASP and on deficiencies related to contract manufacturing facilities.
It did not identify concerns about the clinical efficacy or safety of NASP that would affect its potential for approval.
Sobi has stated that it intends to request a meeting with the FDA to discuss the feedback, consider the necessary steps for resubmission and work closely with contract manufacturing organisations (CMOs) to address the outlined deficiencies.
Sobi chief medical officer Lydia Abad-Franch said: “We continue to believe strongly in NASP’s potential to address the significant unmet need faced by people living with uncontrolled gout. 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.”
NASP is a sequential, two-component infusion therapy administered every four weeks.
It combines tolerogenic nanoencapsulated sirolimus, designed to reduce the formation of anti-drug antibodies, with pegadricase, a uricase that lowers serum uric acid levels.
The treatment is being investigated for its potential to help people with uncontrolled gout, a form of inflammatory arthritis that affects around 200,000 individuals in the US, who continue to experience high uric acid and debilitating flares despite oral therapies.
In December 2025, Sobi signed an agreement to acquire US-based biotechnology company Arthrosi Therapeutics, a move that will expand Sobi’s presence in the gout treatment market.
