Gene Therapy Challenges and Compendia Implications

Gene therapy is an emerging topic in the medical field with new innovations and successes documented daily. The FDA shared their prediction that, based on the current pipeline, they expect to approve anywhere from 10-20 gene and cellular therapy products each year beginning in 2025.

Gene therapy works by replacing a disease-causing gene, inactivating genes that are not functioning correctly, or adding genes to treat a disease. This is often confused with cellular therapy, which administers living cells to trigger an anti-tumor response of the patients’ own cells. Unlike most medications, which manage or prevent diseases, gene therapies can be curative.

Challenges arise in various stages of gene therapy development and marketing. One of the challenges is manufacturing related; after testing in a lab, these processes are being pushed into large scale manufacturing. Robust and reproducible technique is vital for efficient and accurate data during the development of these drugs. Manufacturers may struggle with the space and investment needed for the development of these therapies. Current gene therapies are often indicated for rare and underserved indications, potentially creating a less attractive investment in expensive equipment needed for large-scale production.  An additional challenge includes finding qualifying patients for clinical trials, since the target population is often very small. Patients are often required to travel frequently for their treatments and follow-ups.

In addition to manufacturing and patient obstacles with gene therapy, insurance companies are providing push back as well. In the United States, the average person changes insurers every 3-5 years. In most cases, gene therapy is a one-time infusion that is accompanied by a large cost. Insurance companies may not see the cost benefit until years later, during which time they may have lost that patient. Reform is being proposed to offer insurance companies options on the payment timing, spreading payments out over a period of time, for gene therapy.

One challenge PHSL has focused on is the inclusion of gene therapy products in the drug compendia. Gene therapies have unique strengths, dosing, and mechanisms of action that can be interpreted differently in their listings. The strengths of current genetic therapies use measurements such as genome copies (GC), vector genomes (VG), viral particles (VP), or plaque forming units (PFU). Due to the high number of units being delivered, the strength of gene therapy agents may be displayed using scientific notation. For products with weight-based dosing, multiple NDCs may be available for a gene therapy agent to meet the needs of each patient. Compendia often differentiate between NDCs of the same product by including the number of milliliters contained in the package. Both the number of units and the number of vials for these products may be variable from package to package.  See the below table reviewing how key factors can differ for various gene therapy agents.


There is a need for these products to be classified separately from other products treating similar disease states. Fortunately, compendia have included “Gene Therapy” and “Cellular Therapy” within therapeutic classification descriptions, though the format is not always consistent.  PHSL anticipates that the compendia will continue to refine their process for listing gene therapy agents as new therapies are developed. If you have a new gene therapy in development, contact PHSL to learn how we can use our knowledge and experience to assist in preparation for compendia submission.


Posted January 2024

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