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Gene therapy, which got its start in the 1960s, is finally starting to take hold.
Nicole Trask, PharmD, clinical consultant pharmacist at University of Massachusetts Pharmacy Services in Shrewsbury, MA, opened her session at the Academy of Managed Care Pharmacy Managed Care and Specialty Pharmacy (AMCP) Annual Meeting, in Boston April 24, by defining gene therapy as the administration of genetic material to modify or manipulate the expression of genes or alter the biological properties of living cells. She added that gene therapy can be used to accomplish one of the following actions:
The first clinical study on gene therapy, which included five participants, was published in 1990. In that study, a retroviral vector was used to transfer a neomycin resistance marker gene into tumor-infiltrating lymphocytes for the treatment of metastatic melanoma. In the study, lymphocytes were removed and expanded, she said.
Trask attributed gene therapy’s slow clinical progress largely to safety concerns and vector inefficiencies.
One of the challenges with gene therapy is the need for precision in delivery to the appropriate cells and/or tissues. Further, the gene must be either activated or remain inactivated. Delivery to the wrong cells and/or tissues could be catastrophic.
That’s why focusing on safety is wise. In 1999, one patient died after experiencing an adenovirus gene transfer in ornithine transcarbamylase deficiency, a rare genetic disorder characterized by a complete or partial lack of the enzyme ornithine. And in 2000, two patients with SCID-XI, an inherited disease impacting the immune system, were successfully treated using the MoMLV vector; these were two of 11 patients involved in the clinical trial, where three patients developed leukemia as a result of the gene transfer procedure, according to Trask.
Gene therapy current focus
Investigational indications for gene therapy include conditions such as:
FDA approved in 2017 Luxturna (voretigene neparvovec-rzyl) for the treatment of confirmed biallelic RPE65-mediated retinal dystrophy. The treatment, which is associated with significant improvements in functional vision, costs $425,000 per eye, or $850,000 for most patients, she added.
Trask also highlighted gene therapies that are in late-stage development, including:
While expressing enthusiasm for these therapies, Trask also noted their challenges for payers, including their extremely high costs-as much as $700,000 to $1,000,000 per patient-and the reality that some gene therapies may be associated with safety risks.