Similar Huntington’s Therapies Have Different Adherence Rates: Study
People with Huntington’s disease are more likely to take Austedo (deutetrabenazine) as directed, compared to the similar drug Xenazine (tetrabenazine), according to a new study.
The study also found lower discontinuation rates with Austedo, which may suggest that between these two treatments for chorea, Austedo tends to be better tolerated.
“Real-World Adherence to Tetrabenazine or Deutetrabenazine in Patients with Huntington’s Disease: A Retrospective Database Analysis»Was published in Neurology and therapy. It was sponsored by Teva Pharmaceuticalswhich markets Austedo.
One of the hallmarks of Huntington’s disease is chorea, or sudden, involuntary movements. Austedo and Xenazine (by Lundbeck Pharmaceutical) both are approved to treat chorea associated with Huntington in the United States
These two drugs work in the same way, reducing the release of a signaling molecule called dopamine from nerve cells, thereby reducing abnormal movement. However, due to the pharmacological differences between the two therapies, Austedo leads to more consistent drug exposure throughout the body. This allows for less frequent dosing and may also give Austedo a better safety / tolerability profile than Xenazine. However, there is little actual data comparing the two drugs.
Here, a team led by scientists from Teva performed analysis of insurance data in the United States to study the patterns of adherence between the two drugs. “Compliance” basically means taking medication as directed.
The database used, Integrated Dataverse from Symphony Health Solutions, “captures approximately 90% of all prescription claims filled at US retail pharmacies, representing over 75% of the US population,” wrote the researchers.
In the database, the team identified 281 Huntington’s patients who started treatment with Austedo between 2017 and 2019. For comparison, they also identified 101 patients who started taking Xenazine during this time.
The two groups were demographically similar: most patients were between 38 and 65 years old and more than half were women. However, more patients in the Austedo group than Xenazine had commercial insurance, while patients on Xenazine were more often insured with Medicaid. In addition to Austedo / Xenazine, many patients were also treated with other medicines, such as antidepressants or antipsychotics.
The researchers estimated adherence rates by calculating the proportion of covered days, or COD, based on when prescriptions were filled. As a simple example, if a patient was given medication for 30 days and then refilled after 35 days, then the PDC is 30 out of 35, or about 86%.
The results of the analysis showed that the PDC was significantly higher with Austedo compared to Xenazine (78.5% versus 69.3%). The proportion of patients with a PDC greater than 80% was also higher in the Austedo group, although the difference was not statistically significant.
Further statistical analyzes indicated that, within the Austedo group, adherence was more common among Medicare-insured patients than among those with commercial insurance. Compared with non-adherent patients, adherent patients tended to start treatment later, had a longer duration of illness, and a shorter duration of follow-up. They were also more likely to use antidepressants, anticonvulsants, anti-anxiety drugs, and drugs to reduce fat.
The proportion of patients who stopped the respective treatment within six months of the first month of treatment was significantly lower in the Austedo group than in the Xenazine group (25.4% vs. 37.2%), with differences similar to shorter moments.
“The results of this real-world analysis using data from a large claims database in the United States showed that patients with HD [Huntington’s disease] in deutetrabenazine [Austedo] cohort had greater adherence and lower dropout rates compared to patients in the tetrabenazine group [Xenazine] cohort, ”the scientists concluded.
The team added that these differences “may reflect differences in dosing regimen and tolerability profiles,” although they noted the need for further investigation into the factors underlying the differences in adherence.
One noted limitation of this study, according to the scientists, was the use of insurance data, which is necessarily less precise than clinical information. The team also noted that assessing when prescriptions are filled cannot, by definition, provide definitive information about when and whether patients actually took the drugs.