Pfizer reported data from an open-label, 12-month extension study (Fx-006) of the pivotal phase II/III (Fx-005) trial. This extension study evaluated the long-term clinical outcomes of tafamidis, an oral, investigational compound being studied as a treatment for patients with Transthyretin Familial Amyloid Polyneuropathy (TTR-FAP), a rare and fatal neurodegenerative disease. These data showed that slowing of disease progression was sustained over 30 months.
Fx-006 was conducted to evaluate long-term safety and efficacy, in which patients who completed the 18-month pivotal study (Fx-005) were eligible to enroll. In this analysis, earlier treatment with tafamidis resulted in better outcomes. Patients treated with tafamidis for 30 months had less neurologic deterioration than patients who began tafamidis 18 months later (i.e. placebo-tafamidis group), showing a 55.9 percent preservation of function as measured by the Neuropathy Impairment Score-Lower Limb (NIS-LL), or a mean change from baseline of 3.0 for those treated for 30 months versus 6.8 for those initiating treatment 18 months later (p=0.04).
In addition, patients treated with tafamidis over 30 months showed preservation in large (66% preservation or 1.6 versus 4.7 for those treated 18 months later, p=0.007) and small nerve fiber function (45.5% or 1.2 versus 2.2 for those treated 18 months later, p=ns). Despite having more severe disease (i.e. those patients initiating treatment 18 months later), initiation of tafamidis in patients previously on placebo resulted in slowing of disease progression. A total of 86 patients were enrolled in this extension study. No new safety concerns as compared to the pivotal study were observed over 30 months and no patients discontinued due to adverse events.