FDA delays review of Savara's molgramostim inhalation solution for autoimmune PAP to November

The US FDA has extended its review period for the Biologics License Application (BLA) submitted by Savara Inc. for molgramostim inhalation solution (molgramostim), a recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) delivered by inhalation for autoimmune pulmonary alveolar proteinosis (autoimmune PAP). The PDUFA target action date has been extended by three months to November 22, 2026, shifting from the original August 2026 deadline.

The FDA determined that Savara's responses to recent information requests constituted a major amendment to the BLA, triggering the three-month extension under standard agency procedures. The company said the FDA did not cite any safety, efficacy, or manufacturing concerns in its correspondence. The application remains under Priority Review, a designation reflecting the absence of any approved pharmacological therapy for autoimmune PAP in the United States.

Molgramostim holds Breakthrough Therapy and Fast Track designations from the FDA, as well as Orphan Drug Designation from both the FDA and the European Medicines Agency. The UK's Medicines and Healthcare Products Regulatory Agency has granted Innovation Passport and Promising Innovative Medicine designations. The drug is administered via an eFlow Nebulizer System developed by PARI Pharma GmbH and designed specifically for inhaled delivery of large molecules.

The clinical evidence supporting the BLA draws on two randomized controlled trials. The Phase II IMPALA study (NCT02702180), a double-blind, placebo-controlled trial sponsored by Savara, generated the first peer-reviewed evidence of efficacy, published in the New England Journal of Medicine in 2020 by Trapnell et al. The Phase III IMPALA-2 trial (NCT04544293) enrolled 160 adults randomized to once-daily inhaled molgramostim or placebo over 48 weeks. A 2024 conference abstract by McCarthy et al. reported that molgramostim improved pulmonary gas exchange in the Phase III population. Safety and tolerability data across the programme were presented separately at the 2022 European Respiratory Society congress, with findings characterized as acceptable in the autoimmune PAP population.

Autoimmune PAP is a rare lung disease in which autoantibodies against GM-CSF impair alveolar macrophage function, causing surfactant to accumulate in the alveoli and progressively impairing gas transfer. Patients experience breathlessness, cough, and fatigue, with risk of secondary infection, lung fibrosis, and, in severe cases, the need for lung transplantation. The condition affects an estimated 7 to 27 people per million. No FDA-approved drug exists for the disease; the current standard of care is whole-lung lavage, an invasive procedure performed under general anaesthesia that removes accumulated surfactant mechanically but does not address the underlying immunological defect. Inhaled molgramostim is designed to replace the GM-CSF neutralised by autoantibodies, restoring macrophage-mediated surfactant clearance through a non-invasive route.

The three-month review extension is a procedural outcome that occurs when sponsor responses to FDA information requests are classified as a major amendment. It does not reflect a new signal in the benefit-risk profile of the candidate. The extension places a final agency decision in Q4 2026, with the programme also supporting a pediatric Phase III study (NCT06431776) currently recruiting. An expanded access protocol (NCT06546098) is also in place. The autoimmune PAP field has seen limited pharmacological development activity; inhaled sargramostim, a glycosylated recombinant GM-CSF, received approval in Japan in 2024, though full details of that regulatory action have not been confirmed from primary sources. Both molecules share the same mechanistic class, positioning GM-CSF replacement via inhalation as the central therapeutic approach in a disease where the only established intervention remains a surgical procedure with no disease-modifying effect.

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