Sickle cell disease (SCD) is an incurable genetic blood disorder that reduces patients’ lifespan and quality of life. Many patients live into their 40s or 50s. Yet, throughout their lives, patients are plagued by lethargy, unpredictable painful crises, and frequent hospitalizations. For nearly 20 years, clinicians only had one drug to treat SCD. Since 2017, three new drugs have been approved, but their costs and lack of long-term data have spawned questions regarding access and benefit.
“SCD reduces lifespan by 30 years, and that’s very hard to quantify,” says, professor of medicine and pediatrics and director of Sickle Cell Disease Enterprise at the Levine Cancer Institute at Atrium Health in Charlotte, N.C. “If you put a dollar amount on what someone would make working for 30 adult years, that would be more reflective of the true cost of treating the disease.”
In 1984, hydroxyurea (Hydrea, Droxia) became the first drug to treat SCD in adults.
Originally developed as a myelosuppressive antineoplastic, hydroxyurea is used to treat resistant chronic myeloid leukemia and certain head and neck cancers. In SCD, it increases levels of hemoglobin and fetal hemoglobin.
Despite its benefit, hydroxyurea has two major drawbacks: It is only effective in two genotypes – HbSS or HbS/Beta0thal.
HbSS or HbS/Beta0thal genotypes account for 60% of the SCD population, but further studies are required to elucidate hydroxyurea’s effect in other forms of SCD, according to Dr. Osunkwo.
Secondly, hydroxyurea only reduces the frequency of painful episodes by 50% – not enough to ameliorate the pain, said, associate professor of medicine at Duke University School of Medicine.
Newer therapies offer the potential to enhance the effects of hydroxyurea when used concomitantly. They also give clinicians additional options for patients who either fail hydroxyurea therapy or for whom it is inappropriate.
The amino acid L-glutamine (Endari) became the second drug approved for sickle cell in 2017. Indicated for patients 5 years of age and older, Dr. Osunkwo says many patients were thrilled to have a nonchemotherapeutic option available. However, the medical community received the drug with some skepticism. “The data show Endari is moderately effective at best,” said Dr. Strouse. “Also, the mechanism of action is unclear.”
Additionally, the drug’s powder form and twice-daily dosing regimen make adherence more challenging than swallowing a few hydroxyurea tablets or capsules once a day. In Dr. Osunkwo’s experience, patients who respond best to Endari tend to be those who are naturally motivated individuals who are intentional in their efforts at optimizing their nutrition and self-care.
“It takes a lot to be adherent to Endari,” she said. “You have to work at it.”
On Nov. 15, 2019, the FDA approved crizanlizumab-tmca (Adakveo) for patients 16 years of age and older to decrease the occurrence of vasoocclusive crises.
The drug works by blocking selectin – a protein involved in the painful vascular pathophysiology. Patients receive a loading dose of 5 mg/kg administered via intravenous infusion over 30 minutes at the initiation of therapy, as well as weeks 2 and 4. After that, patients undergo treatment once a month. Nausea, back pain, pyrexia, and arthralgia are the most frequently reported adverse reactions. Clinicians must monitor patients for signs and symptoms of infusion-related reactions.
Ten days later, the FDA approved voxelotor (Oxbryta) for patients ages 12 years and up. The drug inhibits hemoglobin S polymerization and increases hemoglobin levels. Like hydroxyurea, the drug offers the convenience of once-daily dosing, and the tablet can be taken without regard to food. The drug dose requires adjustment for patients with severe hepatic impairment. Headache, fatigue, rash, and gastrointestinal disturbances such as diarrhea, nausea, and abdominal pain fall among the most commonly reported side effects.
Endari, Adakveo, and Oxbryta can all be used as monotherapy. They also provide additional benefits in reducing pain and hospitalizations and improving anemia when used concomitantly with hydroxyurea.
Like so many drugs, these novel therapies are expensive. The cost of these novel treatments has raised some eyebrows.
Annual costs of generic hydroxyurea range in the neighborhood of $1,200. In a 2017, Endari manufacturer Emmaus stated that it aimed to keep drug costs under $20,000 a year. Annual costs for Adakveo and Oxbryta costs are in the neighborhood of $100,000. Adakveo manufacturer Novartis reportedly priced vials at $2,347. Most patients will require at least three of the maximum four vials per treatment. In a press release, Global Therapeutics stated that Oxbyta would cost $10,417 a month.
However, Dr. Osunkwo says the benefits of these new drugs far exceed the costs from both monetary and quality of life standpoints.
“Sickle cell disease is costly to manage,” she said in an interview. “One hospitalization can cost $10,000.”
Additionally, many SCD patients are publicly insured because of the profound disability and loss of productive work they encounter as a direct consequence of their disease and its complications. Those too sick to complete their high school and postsecondary education find limited employment opportunities.
Those fortunate enough to secure employment face significantly fewer years they can work because their pain, fatigue, frequent hospitalizations, and cumulative organ damage result in permanent disability. Only a smaller number of patients with less severe disease manifestations can secure steady employment and pursue careers that allow them to obtain private insurance.
Even if the newer therapies can help cut some costs, clinicians should be aware that prior authorizations can delay patient access to Adakveo and Oxbyta.
“We wrote the first prescription for Oxbryta in November of 2019, but the prior authorization wasn’t approved until February of 2020,” she said. Adding Adakveo to her institution’s formulary required several months of navigation. Given the arduous process, Dr. Osunkwo anticipates it will take at least year after approval before Adakveo is available for all eligible patients.
The long-term impact of these drugs also remains to be seen, so hydroxyurea will likely remain the drug of choice for many patients, according to Dr. Strouse.
Dr. Osunkwo believes SCD needs more drugs in order to truly optimize outcomes, contain costs, and enhance the patient experience.
Dr. Osunkwo reports consultancy and being on the speaker’s bureau and participating in the advisory board for Novartis, which markets Adakveo, and relationships with a variety of other pharmaceutical companies. She is the editor in chief for Hematology News. Dr. Strouse reports consultancy for Global Therapeutics, which markets Oxbryta.