Pharmacotherapeutic group: Other nervous system drugs, ATC code: N07XX08
Mechanism of action
Tafamidis is a selective stabiliser of TTR. Tafamidis binds to TTR at the thyroxine binding sites, stabilising the tetramer and slowing dissociation into monomers, the rate-limiting step in the amyloidogenic process.
Pharmacodynamic effects
Transthyretin amyloidosis is a severely debilitating condition induced by the accumulation of various insoluble fibrillar proteins, or amyloid, within the tissues in amounts sufficient to impair normal function. The dissociation of the transthyretin tetramer to monomers is the rate-limiting step in the pathogenesis of transthyretin amyloidosis. The folded monomers undergo partial denaturation to produce alternatively folded monomeric amyloidogenic intermediates. These intermediates then misassemble into soluble oligomers, profilaments, filaments, and amyloid fibrils. Tafamidis binds with negative cooperativity to the two thyroxine binding sites on the native tetrameric form of transthyretin preventing dissociation into monomers. The inhibition of TTR tetramer dissociation forms the rationale for the use of tafamidis in ATTR-CM patients.
A TTR stabilisation assay was utilised as a pharmacodynamic marker, and assessed the stability of the TTR tetramer.
Tafamidis stabilised both the wild-type TTR tetramer and the tetramers of 14 TTR variants tested clinically after once-daily dosing with tafamidis. Tafamidis also stabilised the TTR tetramer for 25 variants tested ex vivo, thus demonstrating TTR stabilisation of 40 amyloidogenic TTR genotypes.
In a multicentre, international, double-blind, placebo-controlled, randomised study (see Clinical efficacy and safety section), TTR stabilisation was observed at Month 1 and was maintained through Month 30.
Biomarkers associated with heart failure (NT-proBNP and Troponin I) favoured Vyndaqel over placebo.
Clinical efficacy and safety
Efficacy was demonstrated in a multicentre, international, double-blind, placebo-controlled, randomised 3-arm study in 441 patients with wild-type or hereditary ATTR-CM.
Patients were randomised to either tafamidis meglumine 20 mg (n=88) or 80 mg [administered as four 20 mg tafamidis meglumine capsules] (n=176) or matching placebo (n=177) once daily, in addition to standard of care (e.g. diuretics) for 30 months. Treatment assignment was stratified by the presence or absence of a variant TTR genotype as well as by baseline severity of disease (NYHA Class). Table 1 describes the patient demographics and baseline characteristics.
Table 1: Patient demographics and baseline characteristics
| Characteristic | Pooled Tafamidis N=264 | Placebo N=177 |
| Age — year |
| Mean (standard deviation) | 74.5 (7.2) | 74.1 (6.7) |
| Median (minimum, maximum) | 75 (46, 88) | 74 (51, 89) |
| Sex — number (%) |
| Male | 241 (91.3) | 157 (88.7) |
| Female | 23 (8.7) | 20 (11.3) |
| TTR genotype — number (%) |
| ATTRm | 63 (23.9) | 43 (24.3) |
| ATTRwt | 201 (76.1) | 134 (75.7) |
| NYHA Class — number (%) | | |
| NYHA Class I | 24 (9.1) | 13 (7.3) |
| NYHA Class II | 162 (61.4) | 101 (57.1) |
| NYHA Class III | 78 (29.5) | 63 (35.6) |
Abbreviations: ATTRm=variant transthyretin amyloid, ATTRwt=wild-type transthyretin amyloid, NYHA=New York Heart Association.
The primary analysis used a hierarchical combination applying the method of Finkelstein-Schoenfeld (F-S) to all-cause mortality and frequency of cardiovascular-related hospitalisations, which is defined as the number of times a subject is hospitalised (i.e., admitted to a hospital) for cardiovascular-related morbidity. The method compared each patient to every other patient within each stratum in a pair-wise manner that proceeds in a hierarchical fashion using all-cause mortality followed by frequency of cardiovascular-related hospitalisations when patients cannot be differentiated based on mortality.
This analysis demonstrated a significant reduction (p=0.0006) in all-cause mortality and frequency of cardiovascular-related hospitalisations in the pooled tafamidis 20 mg and 80 mg dose group versus placebo (Table 2).
Table 2: Primary analysis using Finkelstein-Schoenfeld (F-S) Method of all-cause mortality and frequency of cardiovascular-related hospitalisations
| Primary analysis | Pooled Tafamidis N=264 | Placebo N=177 |
| Number (%) of subjects alive* at month 30 | 186 (70.5) | 101 (57.1) |
| Average cardiovascular-related hospitalisations during 30 months (per patient per year) among those alive at month 30† | 0.297 | 0.455 |
| p-value from F-S Method | 0.0006 |
* Heart transplantation and cardiac mechanical assist device implantation are considered indicators of approaching end stage. As such, these subjects are treated in the analysis as equivalent to death. Therefore, such subjects are not included in the count of “Number of Subjects Alive at Month 30” even if such subjects are alive based on 30 month vital status follow-up assessment.
† Descriptive mean among those who survived the 30 months.
Analysis of the individual components of the primary analysis (all-cause mortality and cardiovascular-related hospitalisation) also demonstrated significant reductions for tafamidis versus placebo.
The hazard ratio from the all-cause mortality Cox-proportional hazard model for pooled tafamidis was 0.698 (95% CI 0.508, 0.958), indicating a 30.2% reduction in the risk of death relative to the placebo group (p=0.0259). A Kaplan-Meier plot of time to event all-cause mortality is presented in Figure 1.
Figure 1: All-cause mortality*

* Heart transplants and cardiac mechanical assist devices treated as death. Hazard ratio from Cox-proportional hazards model with treatment, TTR genotype (variant and wild-type), and New York Heart Association (NYHA) Baseline classification (NYHA Classes I and II combined and NYHA Class III) as factors.
There were significantly fewer cardiovascular-related hospitalisations with tafamidis compared with placebo with a reduction in risk of 32.4% (Table 3).
Table 3: Cardiovascular-related hospitalisation frequency
| | Pooled Tafamidis N=264 | Placebo N=177 |
| Total (%) number of subjects with Cardiovascular-related hospitalisations | 138 (52.3) | 107 (60.5) |
| Cardiovascular-related hospitalisations per year* | 0.4750 | 0.7025 |
| Pooled tafamidis versus placebo treatment difference (relative risk ratio)* | 0.6761 |
| p-value* | < 0.0001 |
Abbreviation: NYHA=New York Heart Association.
* This analysis was based on a Poisson regression model with treatment, TTR genotype (variant and wild-type), New York Heart Association (NYHA) Baseline classification (NYHA Classes I and II combined and NYHA Class III), treatment-by-TTR genotype interaction, and treatment-by-NYHA Baseline classification interaction terms as factors.
The treatment effect of tafamidis on functional capacity and health status was assessed by the 6-Minute Walk Test (6MWT) and the Kansas City Cardiomyopathy Questionnaire-Overall Summary (KCCQ-OS) score (composed of the Total Symptom, Physical Limitation, Quality of Life, and Social Limitation domains), respectively. A significant treatment effect favouring tafamidis was first observed at Month 6 and remained consistent through Month 30 on both the 6MWT distance and KCCQ-OS score (Table 4).
Table 4: 6MWT and KCCQ-OS and component domain scores
| Endpoints | Baseline Mean (SD) | Change from Baseline to Month 30, LS mean (SE) | Treatment difference from placebo LS mean (95% CI) | p-value |
| Pooled Tafamidis N=264 | Placebo N=177 | Pooled Tafamidis | Placebo |
| 6MWT* (metres) | 350.55 (121.30) | 353.26 (125.98) | -54.87 (5.07) | -130.55 (9.80) | 75.68 (57.56, 93.80) | p< 0.0001 |
| KCCQ-OS* | 67.27 (21.36) | 65.90 (21.74) | -7.16 (1.42) | -20.81 (1.97) | 13.65 (9.48, 17.83) | p< 0.0001 |
* Higher values indicate better health status.
Abbreviations: 6MWT=6-Minute Walk Test; KCCQ-OS=Kansas City Cardiomyopathy Questionnaire-Overall Summary; LS=least squares; CI=confidence interval.
Results from F-S method represented by win ratio for the combined endpoint and its components (all-cause mortality and frequency of cardiovascular-related hospitalisation) consistently favoured tafamidis versus placebo by dose and across all subgroups (wild-type, variant and NYHA Class I & II, and III) except for cardiovascular-related hospitalisation frequency in NYHA Class III (Figure 2) which is higher in the tafamidis treated group compared to placebo (see section 4.2). Analyses of 6MWT and KCCQ-OS also favoured tafamidis relative to placebo within each subgroup.
Figure 2: Results from F-S Method and components by subgroup and dose

Abbreviations: ATTRm=variant transthyretin amyloid, ATTRwt=wild type transthyretin amyloid, F-S=Finkelstein-Schoenfeld, CI=Confidence Interval.
* F-S results presented using win ratio (based on all-cause mortality and frequency of cardiovascular hospitalisation). The Win ratio is the number of pairs of treated-patient “wins” divided by number of pairs of placebo patient “wins.”
Heart transplants and cardiac mechanical assist devices treated as death.
In applying the F-S method to each dose group individually, tafamidis reduced the combination of all-cause mortality and frequency of cardiovascular-related hospitalisations for both the 80 mg and 20 mg doses compared to placebo (p=0.0030 and p=0.0048, respectively). Results of the primary analysis, 6MWT at Month 30 and KCCQ-OS at Month 30 were statistically significant for both the tafamidis meglumine 80 mg and 20 mg doses versus placebo, with similar results for both doses.
Efficacy data for tafamidis 61 mg are not available as this formulation was not evaluated in the double-blind, placebo-controlled, randomised phase 3 study. The relative bioavailability of tafamidis 61 mg is similar to tafamidis meglumine 80 mg at steady-state (see section 5.2).
A supra-therapeutic, single, 400 mg oral dose of tafamidis meglumine solution in healthy volunteers demonstrated no prolongation of the QTc interval.
The licensing authority has waived the obligation to submit the results of studies with tafamidis in all subsets of the paediatric population in transthyretin amyloidosis (see section 4.2 for information on paediatric use).