Single-dose inhaled CF gene therapy shows sustained benefits in primate study

A team at Johns Hopkins University has demonstrated that a single inhaled dose of gene therapy can sustain its effects in the lungs of primates for at least six months—a finding that could reshape how researchers think about treating cystic fibrosis over a patient's lifetime.

The therapy, called AAV1-delivered delta27-264 CFTR, works through a mechanism called transcomplementation. Rather than replacing the faulty CFTR gene outright, it delivers a modified version designed to restore function to a patient's own defective CFTR protein by improving how the protein folds and behaves. This is a meaningful distinction: it means the therapy could theoretically work for people with any CF-causing mutation, not just the subset who respond to existing drugs.

Four juvenile rhesus macaques received a single dose sprayed directly into the airway. Two untreated animals served as controls. Six months later, tissue analysis revealed that the genetic material from the therapy had spread throughout the airways and lungs of all treated animals. It also appeared in organs beyond the lungs—the liver, pancreas, intestine, spleen, lymph nodes, heart, and kidneys—with the highest concentrations in the liver. The researchers found elevated levels of CFTR messenger RNA across all these tissues in treated animals compared to controls, and CFTR protein itself was measurably increased in the airways, lung tissue, and liver.

The therapy's effects were particularly pronounced in two cell types that researchers consider crucial targets: basal cells, which replenish the airway lining, and ionocytes, specialized cells that express high levels of CFTR and help regulate fluid on the airway surface. Treated animals showed significantly higher CFTR levels overlapping with markers of both cell types compared to untreated animals.

One of the central challenges in gene therapy is that the body can develop neutralizing antibodies against the viral vector used to deliver the therapy, potentially rendering it ineffective over time or with repeated doses. By the end of the six-month study, all treated animals had indeed developed such antibodies. However, the immune response to the outer shell of the AAV vector remained low across the group. One animal showed a response at least three times higher than controls, but the remaining treated animals showed responses at or below the threshold. Levels of inflammatory signaling proteins and molecules remained similar between treated and untreated animals, suggesting no systemic inflammation. All animals gained weight normally, and blood tests revealed no abnormalities linked to the treatment.

This immune profile matters enormously for the future of CF gene therapy. If a therapy can be given once and maintain its effects while triggering only minimal immune activation, patients might need dosing only at extended intervals rather than repeatedly throughout their lives. The researchers wrote that their findings "support the potential feasibility of extended dosing intervals and inform the development of repeatable AAV-based gene therapies for CF."

The study, published in the journal Human Gene Therapy, represents a preclinical proof of concept. Cystic fibrosis has long resisted gene therapy approaches despite decades of research. Approved CFTR modulator drugs have improved outcomes for many patients, but they work only for people carrying specific mutations. A therapy that could help all CF patients regardless of their genetic variant has remained elusive. These primate results suggest that the path forward may involve not a single cure-all dose, but a carefully spaced series of treatments that the body tolerates well enough to allow meaningful intervals between them.