While Vyndaqel (tafamidis) has been shown to improve symptoms of familial amyloid polyneuropathy (FAP), it likely does not protect against anemia — a common problem among patients with the disease, a small Japanese study found.
The data suggests that physicians may need to pay attention not only to patients’ neurological symptoms, but also their blood values.
Nonetheless, the research team admitted that the observed gradual decline in hemoglobin levels, which may lead to anemia, may not be a feature shared by all FAP patients. Larger and longer studies are needed to further explore the issue, argued the team from Kumamoto University Hospital and Graduate School of Medical Sciences in Japan.
The study, “Unwanted road to anemia in transthyretin familial amyloid polyneuropathy may continue irrespective of tafamidis treatment,” was published in the journal Annals of Clinical Biochemistry.
Vyndaqel, developed by Pfizer, is approved in more than 40 countries, including those in the European Union and in Japan, for the treatment of FAP, also called transthyretin (TTR) amyloidosis. In the U.S., the treatment is under development by Pfizer for TTR heart disease.
Results from clinical trials show Vyndaqel delays disease progression in FAP patients with the Val30Met genetic mutation. A recent study also confirmed Vyndaqel’s benefits in FAP patients with other mutations.
It acts by stabilizing TTR protein, preventing it from forming the toxic amyloid aggregates.
The research team now explored the treatment’s impact on a host of blood parameters in 33 FAP patients with a variety of mutations in the TTR gene. None had undergone a liver transplant, and all were treated with Vyndaqel.
Researchers sampled blood on three occasions — six months before beginning Vyndaqel treatment, six months after the start of treatment, and one year after they started treatment.
They measured a host of parameters, including blood cell counts, hemoglobin levels, and TTR protein levels.
Taking into account the age at which patients started treatment, sex, FAP stage, and baseline values, they noted that TTR blood levels increased with treatment. This increase is expected, and researchers believe that it mirrors Vyndaqel’s stabilizing effect.
The median hemoglobin levels of the group were in the lower normal range six months before treatment began. Over the course of the study, the levels of hemoglobin decreased. At the last measurement a year after treatment, levels were bordering on what is considered normal.
The data show that while patients may improve on Vyndaqel, doctors might need to monitor patients’ blood values to further improve their symptoms.
“Unfortunately, progression to anemia may occur regardless of tafamidis treatment,” the researchers concluded. “Because anemia is sometimes present in TTR-FAP, attention should be paid to longitudinal changes in commonly used blood data, irrespective of tafamidis treatment.”
However, since the study was small and only examined two time points after treatment, the team underscored that more studies are needed to validate the findings.