Gene Therapy

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Note from the editor

Twenty-two years ago, Jesse Gelsinger died after receiving an experimental gene therapy in a clinical trial seeking a cure for the rare disease he inherited.

His death reverberated throughout the scientific community, spurring investigations of the University of Pennsyvlania center that conducted the study. Gene therapy development, which had been charging ahead on the promise of replacing faulty genes, slowed considerably.

Two decades later, the technology is again at the forefront of biomedical research, catalyzed by advances in safer delivery of genes to cells.

Two genetic fixes for inherited diseases have won U.S. approval, one for a type of childhood blindness and the other for a fatal neuromuscular condition. By one count, nearly 300 experimental gene-based therapies are in clinical testing, including one aimed at OTC deficinecy, the disease from which Gelsinger suffered. By 2025, the Food and Drug Administration expects it will be clearing 10 to 20 cell and gene therapy products a year.

Along with progress have come several major setbacks, though. Recently, two cancer cases in a study of a sickle cell gene therapy renewed safety concerns, although the developer later said its treatment was not the cause. Last fall, three patients with a rare neuromuscular disorder died due to liver complications in a trial of another gene therapy, a tragedy that brought with it echoes of Gelsinger's death.

And just a few months before then, a hemophilia gene therapy that was widely expected to win U.S. approval was rejected by the FDA, which asked for more data from drugmaker BioMarin Pharmaceutical to prove the benefit observed was durable. 

Gene therapy's effects on a healthcare system designed around chronic treatment, meanwhile, are just beginning to be worked out. The two medicines now approved cost $850,000 and $2.1 million per patient, respectively, and those advancing through development are expected to command similar price tags. In a sign of pushback to such price tags, Bluebird bio recently said it would wind down operations in Europe after failing to reach agreements with payers there for its two gene therapies cleared by European regulators. 

Science may also move quickly past gene replacement therapy to gene editing via CRISPR and other methods, an approach in which the unknowns are even greater and clinical work has just begun.

Ned Pagliarulo Lead Editor

Key questions facing gene therapy in 2021

• Published Jan. 8, 2021

Record funding is flowing into cell, gene therapy companies

• Published March 16, 2021

Intellia delivers a 'landmark' for CRISPR gene editing

• Published June 26, 2021

Gene therapy for Fabry: early stages, promising results

• Published July 22, 2021

Bluebird to wind down business in Europe amid gene therapy struggles

• Published Aug. 9, 2021

FDA gene therapy holdups suggest closer scrutiny by agency

• Published Nov. 5, 2020

Gene therapy for sickle cell disease: progress and competition

• Published July 8, 2021

A cure for hemophilia seemed closer than ever. For many patients, it's now further out of reach

• Published Aug. 18, 2020 • Updated Aug. 19, 2020

Big pharma shied away from gene therapy for years. Academia picked up the slack

• Published March 17, 2020

How 2 scientific pioneers teamed up to run AskBio, Bayer's new gene therapy division

• Published Jan. 21, 2021

The latest developments on the gene therapy frontier

Five years from now, the Food and Drug Administration expects it will be clearing 10 to 20 cell and gene therapy products a year. Yet while the arrival of gene therapy's moment may be clear, its effects on a healthcare system designed around chronic treatment are not.

included in this trendline
  • Trends and challenges in the world of gene therapy today
  • Intellia delivers a 'landmark' for CRISPR gene editing
  • Gene therapy for Fabry: early stages, promising results