The U.S. Food and Drug Administration has approved Kresladi, the first gene therapy for Leukocyte Adhesion Deficiency Type I (LAD-I), a rare genetic immune disorder that once meant children faced life-threatening infections with few treatment options. This breakthrough offers hope to children born with mutations in the ITGB2 gene, which normally allows white blood cells to travel through the bloodstream and reach sites of infection. Without this ability, their immune systems cannot properly fight bacteria or fungi, leading to severe, recurrent infections that historically made survival beyond childhood uncommon .

What Is Leukocyte Adhesion Deficiency Type I and Why Does It Matter?

LAD-I is an extremely rare pediatric disorder, affecting roughly one in a million children worldwide . The condition stems from mutations in the ITGB2 gene, which produces proteins essential for white blood cells to move through the bloodstream and reach infected tissues. When this mechanism fails, children experience recurrent and severe infections, including bacterial and fungal infections that can be life-threatening. Before this gene therapy approval, treatment options were severely limited, and many children did not survive into adulthood without a successful bone marrow transplant, which carries its own risks.

How Does the New Gene Therapy Treatment Work?

Kresladi uses an innovative approach developed through decades of research led by Donald Kohn at UCLA . The treatment process involves collecting a child's own blood stem cells, inserting a healthy copy of the defective ITGB2 gene into those cells, and then returning the modified cells to the patient's body. Once inside the body, these corrected cells generate functioning immune cells capable of fighting infections and healing wounds. Because the therapy uses the patient's own cells, it avoids complications often associated with donor transplants, such as immune rejection or graft-versus-host disease, where the transplanted cells attack the recipient's own tissues.

What Did the Clinical Trial Show?

The FDA approval was based on results from a clinical trial conducted across several international sites involving nine children between five months and nine years old . The results were remarkable. All nine patients survived without requiring bone marrow transplantation, a major achievement for a condition that historically had limited survival options. The trial also documented sustained expression of the restored immune proteins and improved immune function in treated children, meaning the therapy's benefits persisted over time.

• Survival Rate: All nine trial participants survived without needing bone marrow transplantation, compared to the historical standard of care.
• Immune Rejection: No cases of immune rejection or graft failure occurred, eliminating a major risk associated with traditional donor transplants.
• Infection Reduction: Severe infections requiring hospitalization dropped significantly in treated children, reducing the burden of recurrent life-threatening illness.

How Does This Compare to Previous Treatment Options?

Before Kresladi's approval, bone marrow transplantation was the primary treatment option for LAD-I, but it carried substantial risks. Transplants from donors can trigger immune rejection, where the recipient's body attacks the transplanted cells, or graft-versus-host disease, where transplanted cells attack the recipient's own tissues. Gene therapy using a patient's own cells eliminates these rejection risks entirely. Additionally, the therapy allows children to avoid the intensive chemotherapy and radiation conditioning often required before bone marrow transplantation, reducing overall treatment burden and side effects.

Steps to Understanding Gene Therapy for Rare Immune Disorders

• Identify the Genetic Defect: Doctors first confirm the specific gene mutation causing the immune disorder through genetic testing, which determines whether a child is a candidate for gene therapy.
• Collect Patient Cells: Medical teams extract the patient's own blood stem cells, which serve as the foundation for the therapy and eliminate rejection risks.
• Insert the Healthy Gene: Scientists use advanced techniques to insert a functional copy of the defective gene into the collected cells in a laboratory setting.
• Return Modified Cells: The corrected cells are reintroduced into the patient's body, where they establish themselves and begin producing functioning immune cells.
• Monitor Long-Term Outcomes: Patients undergo ongoing clinical follow-up studies and registry monitoring to confirm sustained benefits and catch any long-term complications early.

The approval of Kresladi represents a significant milestone in immunology and regenerative medicine. The work was supported in part by the California Institute for Regenerative Medicine, which funds stem cell and gene therapy research . While the therapy has shown remarkable promise in the clinical trial, researchers emphasize that long-term monitoring of treated patients will continue through clinical follow-up studies and registries to confirm its sustained benefits and identify any late-emerging effects.

This breakthrough opens the door to broader applications of gene therapy for other rare childhood diseases. If similar successes follow, gene therapy could transform how many rare genetic immune disorders are treated, turning once-fatal conditions into manageable or even curable disorders. For families of children with LAD-I, Kresladi offers access to treatment through specialized medical centers, providing hope where few options existed before.