The European Commission has officially approved Pfizer's (PFE 0.62%) drug Vyndaqel as a treatment for transthyretin amyloidosis in adult patients with cardiomyopathy (ATTR-CM), a disease characterized by the buildup of misfolded TTR protein in the heart. Vyndaqel is designed to stabilize the protein and keep it from misfolding.

The drug was previously approved at a lower dose for ATTR patients with a buildup of the misfolded protein in their nervous system, but sales of the drug were limited due to relatively lackluster efficacy data for patients with the polyneuropathy version of the disease.

By contrast, the results for ATTR-CM were outstanding. Over the 30 months that patients took the drug, Vyndaqel reduced the risk of death by 30% compared to placebo. It also reduced the frequency of cardiovascular-related hospitalization by 32%.

Doctor listening to a patient's heart with a stethoscope

Image source: Getty Images.

The dose for the ATTR-CM is four times higher than the dose for the polyneuropathy version, so Pfizer developed a single-pill free acid form, which it calls Vyndamax in the U.S., so patients don't have to take four pills every day.

Vyndaqel was launched in the U.S. last May, while Vyndamax was launched in September. Pfizer has been able to ramp up sales relatively quickly; it generated $104 million in combined U.S. sales of Vyndaqel and Vyndamax in the fourth quarter.

The launch in Europe may take longer as the pharmaceutical company will have to negotiate with payers in each country in the EU. There's some indication that the demand for the drug is there; sales in developed Europe doubled year over year in the fourth quarter from $25 million to $53 million, suggesting some doctors have been prescribing the drug off-label before it received official approval.