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Research Into Gene Therapies Could Bring More Options
Specialty Pharmacy Pipeline | Drugs to Watch
Anticipated Launches | Q1 2020 – Q2 2020
About 100,000 Americans have sickle cell disease (SCD).
About 90 percent of people with SCD in the U.S. live to adulthood, but nearly all experience acute painful episodes, called vaso-occlusive crises (VOCs), when sickled red blood cells block small blood vessels.
|A patient with sickle cell disease is estimated to face an average of nearly $1 million in total lifetime health care costs.
The U.S. Food and Drug Administration (FDA) recently approved two new treatments for SCD that could expand treatment options for patients. Research is also ongoing for gene therapies that could provide an alternative to bone marrow transplant — currently the only available cure for SCD.
The FDA approved Adakveo (crizanlizumab), a monoclonal antibody developed by Novartis, on November 15, 2019.
In a pivotal trial, patients receiving Adakveo had about half as many VOCs leading to health care visits compared to the control group receiving placebo, regardless of whether they received hydroxyurea. They also had a longer time before their first VOC, and the percentage of patients who had no VOCs during treatment was triple the rate for patients receiving placebo — 37.5 percent compared to 12.2 percent.
Dosage depends on the patient’s weight. Depending on the dosage needed, Adakveo will cost between $7,000 and $9,500 per month and will be covered under the medical benefit.
The FDA approved Oxbryta (voxelotor), developed by Global Blood Therapeutics, 10 days after Adakveo, on November 25, 2019. Roughly one quarter of patients with SCD experience a stroke by the age of 45.
In a phase III trial, hemoglobin levels increased by more than one gram per deciliter in 51 percent of patients receiving high-dose voxelotor, compared with 7 percent of those on placebo.
The list price for Oxbryta is $10,417 a month and it will be covered under the pharmacy benefit.
Ensuring Appropriate Use
With new therapies coming to market, it is important to ensure appropriate use to help plan sponsors balance member access and cost. We have developed clinical criteria for sickle cell treatments to help clients manage this category.
- Endari currently is approved for members, aged five years or older, with sickle cell disease if they have either tried and failed hydroxyurea or have a contraindication to it, or for concurrent use with hydroxyurea.
- Adakveo is approved to help reduce frequency of VOCs among members aged 16 years and older with sickle cell disease and prior vasooclusive crises.
- Oxbryta treatment is approved for members 12 years of age and older with sickle cell disease and a pretreatment hemoglobin level of 10.5 g/dL or less.
Gene Therapy for SCD
Currently the only cure for SCD is a bone marrow transplant. However, finding a bone marrow match can be challenging, and the treatment is complex, requiring the patient’s own marrow to be eliminated with chemotherapy.
Researchers are now looking for potential gene therapies to help cure SCD.
The first approach is to harvest the patient’s stem cells, replace the faulty HBB gene with a healthy copy in the lab, and transplant the cells back into the patient using a viral vector.
The NIH announced a new and improved viral vector that was up to 10X more efficient at incorporating corrective genes into marrow stem cells.
Another approach is using the CRISPR gene-editing technique to boost the production of fetal hemoglobin by genetically altering another gene in hematopoietic stem cells. Fetal hemoglobin — a form of hemoglobin produced by babies from about seven months before birth to about six months after birth — represses sickling of cells in patients with sickle cell anemia, but most people only produce a tiny amount of it after infancy.
However, some patients with SCD — those not badly affected by symptoms — have genetic variations that enable them to produce fetal hemoglobin into adulthood. Fetal hemoglobin binds more strongly to oxygen. By using a highly specific enzyme to remove one of the genes that stops production of fetal hemoglobin, scientists aim to boost the production of fetal hemoglobin in adult patients with SCD. Researchers aim to increase production of fetal hemoglobin in stem cells by using a highly specific enzyme to cut the cell’s DNA in the section containing one of the genes that suppress production of fetal hemoglobin.
Among the companies working to develop gene therapies for SCD are Bluebird Bio, Sangamo Therapeutics, and Vertex and CRISPR Therapeutics, who recently announced a deal for the development of up to six gene therapies, including potential candidates for SCD.
This document contains references to brand-name prescription drugs that are trademarks or registered trademarks of pharmaceutical manufacturers not affiliated with CVS Health.
Image source: Licensed from Getty Images, 2020.
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