MENLO PARK, California, May 20, 2026
ReCode Therapeutics announced positive clinical data from its RCT1100 inhaled mRNA therapy program for Primary Ciliary Dyskinesia (PCD) during the American Thoracic Society (ATS) 2026 International Conference, marking what the company described as the first demonstration of biologic activity for a genetic medicine in patients with PCD. The findings represent a potentially major breakthrough for the rare respiratory disease community because no approved disease-modifying therapies currently exist for PCD, a progressive inherited disorder that causes chronic lung infections, impaired mucus clearance, and long-term respiratory damage. The data also provide one of the clearest indications yet that inhaled mRNA therapeutics can successfully deliver functional proteins directly into the human airway, an area that has remained technically challenging for the biotechnology industry despite growing investment in genetic medicines and lipid nanoparticle delivery technologies.
Results from the multinational RCT1100-103 Phase 1b clinical trial, conducted across clinical sites in Denmark, Germany, and the United States, showed that 57% of treated patients achieved meaningful improvement in mucociliary clearance (MCC) after 12 weeks of therapy. Bronchoscopy evaluations confirmed both restoration of protein expression and renewed ciliary activity within airway tissues, demonstrating that the inhaled therapy not only reached target lung cells but also produced measurable biologic effects associated with improved airway function. Researchers additionally observed that restoration of protein expression correlated with improvements in mucociliary clearance, supporting the potential disease-modifying impact of the therapy. The treatment was reported to be safe and well tolerated, with no serious adverse events identified during the study, reinforcing confidence in the platform’s clinical feasibility for repeated pulmonary administration.
Clinical Data Validate Inhaled Genetic Medicine Delivery to the Lung
The latest findings are considered highly significant because effective delivery of mRNA therapeutics into lung tissue has historically posed substantial scientific and engineering barriers. Unlike liver-targeted therapies where lipid nanoparticles naturally accumulate after systemic administration, inhaled therapies must survive aerosolization, penetrate airway mucus, enter target cells efficiently, and produce sustained protein translation in highly sensitive respiratory tissue. ReCode’s proprietary Selective Organ Targeting (SORT) lipid nanoparticle platform was developed specifically to overcome those challenges and enable precision delivery of genetic medicines directly into organs and tissues implicated in disease. According to the company, the Phase 1b results provide strong clinical validation that the SORT LNP platform can successfully support inhaled mRNA delivery in humans.
Company executives described the results as a major milestone for both the platform and the broader future of respiratory genetic medicine. Chief Executive Officer Shehnaaz Suliman stated that the study demonstrated the promise of inhaled genetic medicine delivery and opened the door to an entirely new treatment paradigm for PCD patients. Chief Medical Officer John Matthews highlighted the extensive collaboration between researchers, clinicians, and patient communities involved in advancing the program. The current study builds upon earlier Phase 1a and Phase 1b trials that previously established favorable safety and tolerability profiles for RCT1100 across multiple dosing levels. Earlier studies showed no serious or Grade 3 treatment-emergent adverse events even with repeated dosing schedules of up to 5 mg administered three times weekly, further strengthening the therapy’s safety profile heading into future development stages.
PCD Remains a Major Unmet Need in Rare Respiratory Medicine
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Primary Ciliary Dyskinesia is a rare inherited disease caused by mutations in more than 50 different genes that impair the function of cilia, the microscopic hair-like structures responsible for clearing mucus and pathogens from the respiratory tract. Defective mucociliary clearance leads to chronic respiratory infections, bronchiectasis, declining lung function, and progressive lung destruction over time. ReCode estimates that approximately 45,000 people in the United States may be affected by PCD, although nearly 80% of cases are believed to remain undiagnosed because of limited screening and disease awareness. Current treatment options focus primarily on symptom management and infection control rather than addressing the underlying genetic cause of the disease.
The successful demonstration of biologic activity from inhaled mRNA therapy could have implications extending beyond PCD into broader respiratory medicine and genetic therapy development. Industry researchers increasingly view pulmonary delivery of mRNA and gene-editing therapies as a potentially transformative approach for diseases including cystic fibrosis, chronic obstructive pulmonary disease, and other inherited lung disorders. ReCode’s latest clinical data therefore represent not only a potential milestone for PCD treatment development but also a broader proof-of-concept for the future of inhaled genetic medicines targeting complex respiratory diseases.
Source: ReCode Therapeutics press release
