The transthyretin (TTR) amyloidoses are a group of degenerative diseases caused by TTR aggregation, requiring rate-limiting tetramer dissociation. Kinetic stabilization of TTR, by preferential binding of a drug to the native tetramer over the dissociative transition state, dramatically slows the progression of familial amyloid polyneuropathy. An established method for quantifying the kinetic stability of recombinant TTR tetramers in buffer is subunit exchange, in which tagged TTR homotetramers are added to untagged homotetramers at equal concentrations to measure the rate at which the subunits exchange. Herein, we report a subunit exchange method for quantifying the kinetic stability of endogenous TTR in human plasma. The subunit exchange reaction is initiated by the addition of a substoichiometric quantity of FLAG-tagged TTR homotetramers to endogenous TTR in plasma. Aliquots of the subunit exchange reaction, taken as a function of time, are then added to an excess of a fluorogenic small molecule, which immediately arrests further subunit exchange. After binding, the small molecule reacts with the TTR tetramers, rendering them fluorescent and detectable in human plasma after subsequent ion exchange chromatography. The ability to report on the extent of TTR kinetic stabilization resulting from treatment with oral tafamidis is important, especially for selection of the appropriate dose for patients carrying rare mutations. This method could also serve as a surrogate biomarker for the prediction of the clinical outcome. Subunit exchange was used to quantify the stabilization of WT TTR from senile systemic amyloidosis patients currently being treated with tafamidis (20 mg orally, once daily). TTR kinetic stability correlated with the tafamidis plasma concentration.

Transthyretin (TTR) cardiac amyloidosis is an important, often under-recognized and potentially modifiable cause of heart failure with a preserved ejection fraction. The only proven treatment is liver or combined heart/liver transplantation, which, although effective, is not suitable for the vast majority of older adults with this condition. Diflunisal, a nonsteroidal anti-inflammatory drug, can stabilize the TTR tetramer in vitro and may prevent misfolding monomers and dimers from forming amyloid deposits in the heart. It is one of two small molecules assessed in animal safety studies and human clinical trials of TTR polyneuropathy. The authors conducted a single-arm, open-label investigation with a mean follow-up of 0.9±0.3 years to determine the safety and efficacy of diflunisal administration in a cohort of 13 patients with confirmed wild-type or mutant TTR cardiac amyloidosis. Diflunisal was well tolerated from a hematologic standpoint, although a 6% decline in estimated glomerular filtration rate was noted. Therapy was discontinued in one patient who rapidly developed volume overload. There was no significant mean change in cardiac structure (left ventricular mass: −53 g/m2 change, P=.36), function (ejection fraction: −2% change, P=.61), or biomarkers (Troponin I: +0.03 ng/mL, P=.08; BNP: +93 pg/mL change, P=.52) during the course of therapy. These data suggest that at low dosages and with careful monitoring, diflunisal can be safely administered to compensated patients with cardiac TTR amyloidosis. Further study in a randomized placebo-controlled trial is warranted.

Background: In patients with heart failure (HF), malnutrition and dietary sodium excess are common and may worsen outcomes. No prior studies have provided low-sodium, nutritionally-complete meals following HF hospitalization. Methods and Results: The Geriatric OUt-of-hospital Randomized MEal Trial in Heart Failure (GOURMET-HF) study randomized patients discharged from HF hospitalization to four weeks of home-delivered sodium-restricted Dietary Approaches to Stop Hypertension meals (DASH/SRD; 1,500 mg sodium/day) vs. usual care. The primary outcome was the between-group change in the Kansas City Cardiomyopathy Questionnaire (KCCQ) Summary Score from discharge to four weeks post-discharge. Additional outcomes included changes in the KCCQ Clinical Summary Score and cardiac biomarkers. All patients were followed 12 weeks for death/all-cause readmission and potential diet-related adverse events (symptomatic hypotension, hyperkalemia, acute kidney injury). 66 patients were randomized 1:1 at discharge to DASH/SRD vs. usual care (age 71±8 years, 30% female, ejection fraction 39±18%). The KCCQ Summary Score increased similarly between groups (DASH/SRD 46±23 to 59±20 vs. usual care 43±19 to 53±24, p=0.38) but the KCCQ Clinical Summary Score increase tended to be greater in DASH/SRD participants (47±22 to 65±19 vs. 45±20 to 55±26, p=0.053). Potentially diet-related adverse events were uncommon; 30-day HF readmissions (11% vs. 27%, p=0.06) and days rehospitalized within that timeframe (17 vs. 55, p=0.055) trended lower in DASH/SRD participants. Conclusions: Home-delivered DASH/SRD following HF hospitalization appeared safe in selected patients, and had directionally favorable effects on HF clinical status and 30-day readmissions. Larger studies are warranted to clarify the effects of post-discharge nutritional support in patients with HF. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT02148679

TTR stabilizers are associated with decreased death and OHT in TTR cardiac amyloidosis. These results need to be confirmed by ongoing randomized clinical trials.