Response to treatment indicated by either improvement(decrease from baseline) or stabilization(change from baseline of 0 to less than[<] 2) in NIS-LL score,based on mean of 2 scores in 1 week period.NIS-LL assessed muscle weakness,reflexes,sensation.Each item scored separately for left,right limbs.Components of muscle weakness:0(normal)-4(paralysis),higher score=more weakness;reflexes,sensation:0=normal,1=decreased,or 2=absent.Total NIS-LL score range 0-88,higher score=more impairment. For tafamidis-tafamidis group, NIS-LL baseline value of previous study FX-005(NCT00409175) used as reference.

Intent-to-treat (ITT) population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure.

Response to treatment indicated by either improvement(decrease from baseline) or stabilization(change from baseline of 0 to less than[<] 2) in NIS-LL score,based on mean of 2 scores in 1 week period.NIS-LL assessed muscle weakness,reflexes,sensation.Each item scored separately for left,right limbs.Components of muscle weakness:0(normal)-4(paralysis),higher score=more weakness;reflexes,sensation:0=normal,1=decreased,or 2=absent.Total NIS-LL score range 0-88,higher score=more impairment. For tafamidis-tafamidis group, NIS-LL baseline value of previous study FX-005(NCT00409175) used as reference.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies those participants who were evaluable for this measure.

Norfolk QOL-DN: 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy; Item 1 to 7: related to symptoms and presence of symptoms was assessed as 1 and absence was assessed as 0. Item 8-35: related to activities of daily living and scored on a 5-point Likert scale, where 0= no problem and 4= severe problem (except item 32, where -2= much better, 0=about the same, 2=much worse). TQOL= sum of all the items, total possible score range= -2 to 138, where higher score=worse quality of life.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure.

Norfolk QOL-DN: 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy; Item 1 to 7: related to symptoms and presence of symptoms was assessed as 1 and absence was assessed as 0. Item 8-35: related to activities of daily living and scored on a 5-point Likert scale, where 0= no problem and 4= severe problem (except item 32, where -2= much better, 0=about the same, 2=much worse). TQOL= sum of all the items, total possible score range= -2 to 138, where higher score=worse quality of life.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure.

NIS-LL: assessed muscle weakness, reflexes and sensation; scored separately for left and right limbs. Components of muscle weakness (hip and knee flexion, hip and knee extension, ankle dorsiflexors, ankle plantar flexors, toe extensors, toe flexors) are scored on scale 0 (normal) to 4 (paralysis), higher score=greater weakness. Components of reflexes (quadriceps femoris, triceps surae) and sensation (touch pressure, pin-prick, vibration, joint position) were scored 0 = normal, 1= decreased, or 2 = absent. Total possible NIS-LL score range 0-88, higher score=greater impairment.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants for this measure at specified time point for each arm group.

Norfolk QOL-DN: 35-item participant-rated questionnaire to assess impact of DN on QOL; Item 1-7:scored as 1=symptoms present, 0=symptoms absent. Item 8-35:scored on 5-point Likert scale: 0=no problem,4=severe problem (except item 32: -2=much better, 0=about same, 2=much worse). Norfolk QOL-DN summarized in 5 domains(score range):physical functioning/large fiber neuropathy(-2 to 58), activities of daily living(ADLs) (0 to 20), symptoms(0 to 32), small fiber neuropathy(0 to 16), autonomic neuropathy(0 to 12); higher score=greater impairment,for each. Total score=-2 to138(higher score=worse QOL).

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants for this measure at specified time point for each arm group.

Summated 7 score: composite score included five Nerve Conduction Studies (NCS) attributes (peroneal nerve distal motor latency, peroneal nerve compound muscle action potential, peroneal nerve motor conduction velocity, tibial nerve distal motor latency, and sural nerve sensory nerve action potential amplitude) along with Vibration Detection Threshold (VDT) obtained in great toes, and Heart Rate Response to Deep Breathing (HRDB) value. Score was determined through reference to normal values for age, sex and height. Total score range= -26 to 26, where higher score=worse nerve function.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants for this measure at specified time point for each arm group.

Summated 3 Nerve Tests Small Fiber Normal Deviates Score (NTSFnds) included cooling threshold for the lower limbs, heat pain threshold for the lower limbs and HRDB. Total score range= -11.2 to 11.2, where higher score=worse nerve function.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants for this measure at specified time point for each arm group.

BMI was calculated by weight divided by height squared. mBMI was calculated by multiplying BMI by serum albumin levels to compensate for edema formation. A progressive decline in mBMI indicated worsening of disease severity.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants for this measure at specified time point for each arm group.

Troponin I was biomarker of cardiac stress (myocardial necrosis and increased filling pressures/ left ventricular [LV] wall stress).

Safety population included participants who received at least one dose of study medication. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants evaluable for this measure at the specified time point for each arm group.

NT-proBNP was biomarker of cardiac stress (myocardial necrosis and increased filling pressures/ LV wall stress).

Safety population included participants who received at least one dose of study medication. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants evaluable for this measure at the specified time point for each arm group.

IENF density was quantified in 3 millimeter (mm) immunostained skin punch biopsies containing epidermis and superficial dermis to evaluate the amount and morphological appearance of small diameter nerve fibers, both somatic and autonomic, in sensory neuropathies. It is used in diagnosing various neuropathic conditions.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure.

TTR tetramer was assessed using a validated immunoturbidimetric assay. The Fraction of Initial (FOI) is the ratio of the measured TTR tetramer concentration after denaturation to the measured TTR tetramer concentration before denaturation. TTR tetramer stabilization is based on the difference between the on-treatment FOI and the baseline FOI expressed as a percentage of the baseline FOI.

ITT population included all participants who received at least one dose of study medication and had no more than 2 months interruption between studies FX-005 and FX-006. 'N' (number of participants analyzed) signifies participants evaluable for this measure.

An Adverse Event (AE) was any untoward medical occurrence in participant who received study drug without regard to possibility of causal relationship. SAE: AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent/significant disability/incapacity; congenital anomaly. Treatment-emergent were events between first dose of study drug, up to 30 days after last dose that were absent before treatment or that worsened relative to pretreatment state.

Safety population included participants who received at least one dose of study medication.

AE=any untoward medical occurrence in participant who received study drug without regard to possibility of causal relationship. Grade 3 (Severe) events=unacceptable or intolerable events, significantly interrupting usual daily activity, require systemic drug therapy/other treatment. Grade 4 (Life-threatening) events caused participant to be in imminent danger of death. Grade 5 (Death) events=death related to an AE. Treatment-emergent events=between first dose of study drug and up to 30 days after last dose that were absent before treatment or that worsened relative to pretreatment state.

Safety population included participants who received at least one dose of study medication.

Clinically significant ECHO findings included: LV posterior wall thickness greater than or equal to (>=)13 mm, LV septal thickness >= 13 mm, right ventricular thickness >= 7 mm, ratio of peak mitral early diastolic and atrial contraction velocity (E/A ratio) >= 2, prime septal (E/E) >15, ejection fraction < 50 percent (%), E deceleration time <= 150 millisecond (ms), isovolumic relaxation time (IVRT) <= 70 ms, any valve thickening (> trace regurgitation in mitral, aortic, pulmonary, or tricuspid valves), abnormal respiratory variation of inferior vena cava, pericardial effusion.

Safety population included participants who received at least one dose of study medication. 'N' (number of participants analyzed) signifies participants evaluable for this measure. 'n' signifies participants evaluable for this measure at the specified time point for each arm group.

Clinically significant ECG findings included: corrected QT (QTc) > 450 ms, QTc >500 ms, change in QTc between 30 and 60 ms, change in QTc greater than or equal to 60 ms.

Safety population included participants who received at least one dose of study medication. 'n' signifies participants for this measure at specified time point for each arm group.

Clinically significant Holter monitor findings included: atrial fibrillation/flutter, atrial tachycardia, non-sustained ventricular tachycardia (<30 beats), sustained ventricular tachycardia (>= 30 beats), sinus pause (RR >2.0 second, where RR=60/heart rate), ventricular premature contractions.

Safety population included participants who received at least one dose of study medication. 'n' signifies participants for this measure at specified time point for each arm group.

An AE was any untoward medical occurrence attributed to study drug in a participant who received study drug. An SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly.

Safety population included participants who received at least one dose of study medication.