An Extension of Study Fx-005 Evaluating Long-Term Safety And Clinical Outcomes Of Fx-1006A In Patients With Transthyretin Amyloid Polyneuropathy

This study is designed to determine the long-term safety and tolerability of Fx-1006A as well as the effects of Fx-1006A on clinical outcomes in patients with ATTR-PN. All patients who enroll in this extension study will receive once-daily oral 20 mg Fx-1006A for 12 months; therefore, patients randomized to placebo in Study Fx-005 will cross over to active drug (Fx-1006A 20 mg) during this study. However, patients and their families as well as clinical Investigators and their clinical site staff will remain blinded to the original Fx-005 treatment assignment. It is intended that there will be no interruption in study medication administration between the two studies. The majority of safety and clinical outcomes assessments will be identical to those evaluated in Study Fx-005. Additional assessments for this open-label extension study include 24-hour Holter monitoring and skin biopsy for IENF; patients will be required to provide written informed consent to participate in this open-label extension study prior to having these additional procedures performed. The values obtained from procedures and evaluations conducted during the Month 18 visit of Study Fx-005 will be used as the Baseline values for this open-label extension study. The Baseline assessments of IENF and Holter monitoring may be conducted at either day of the Month 18 visit days of Study Fx-005, but prior to the first Fx-1006A dose in this open-label extension study. Clinic Visits will be conducted at Week 6 (± 2 days), and Month 3 (± 1 week), Month 6 (± 2 weeks), and Month 12 (± 2 weeks). Monthly telephone contacts (± 1 week of the scheduled date) will be made during months in which no investigative site visits are scheduled (Months 2, 4, 5, 7, 8, 9, 10, and 11) for assessment of adverse events and concomitant medications. Neurological evaluation by NIS-LL will be performed at Months 6 and 12. The NIS-LL will be assessed by utilizing the average of two successive NIS-LL clinical assessment scores obtained at least 24 hours apart within a one week period for each study visit. A dedicated neurologist will be required to perform NIS-LL scoring across all time-points for each individual patient enrolled in the study. Quality of life utilizing the Norfolk QOL-DN will be assessed at Months 6 and 12 (based on the total score as well as the five individual domains of the questionnaire). QST (utilizing CASE IV), NCS, HRDB, mBMI, and echocardiography will be conducted at Months 6 and 12. Holter monitoring will be conducted at Baseline and Months 6 and 12. Biopsies for IENF will be obtained at Baseline only. Assessments of troponin I and NT-pro-BNP levels will be made at each study visit. Blood samples for pharmacokinetic assessments (Fx-1006A concentrations as well as calculated steady-state parameters) and pharmacodynamic assessments (TTR stabilization) will be collected at Week 6 and Months 6 and 12. Safety and tolerability will be assessed throughout the study. Vital signs, 12-lead ECG, blood and urine samples for clinical laboratory tests (serum chemistry, hematology, coagulation panel, urinalysis, and urine pregnancy testing), adverse events, and concomitant medications will be assessed at each study visit. Eye examinations (including fundal photography) will be conducted at Months 6 and 12. Abbreviated physical examinations will be conducted at Week 6, and Months 3 and 6, and a complete physical examination will be conducted at Month 12. All patients will be contacted by telephone 30 days (± 1 week) after the last dose of study medication for assessment of adverse events and concomitant medications. Patients who complete the Month 12 visit of this open-label study may be allowed to continue receiving Fx-1006A under a compassionate use program. Patients who discontinue from the study at any time after enrollment (i.e., early termination) will have final safety assessments performed at the time of discontinuation. Any patient discontinuing after the Month 6 visit will have all safety and clinical outcomes assessments scheduled for the Month 12 visit performed.