ATTR amyloidosis is caused by the deposition of transthyretin in the form of amyloid fibrils in virtually every organ of the body, including the heart. This systemic deposition leads to a phenotypic variability that has not been molecularly explained yet. In brain amyloid conditions, previous studies suggest an association between clinical phenotype and the molecular structures of their amyloid fibrils. Here we investigate whether there is such an association in ATTRv amyloidosis patients carrying the mutation I84S. Using cryo-electron microscopy, we determined the structures of cardiac fibrils extracted from three ATTR amyloidosis patients carrying the ATTRv-I84S mutation, associated with a consistent clinical phenotype. We found that in each ATTRv-I84S patient, the cardiac fibrils exhibited different local conformations, and these variations can co-exist within the same fibril. Our finding suggests that one amyloid disease may associate with multiple fibril structures in systemic amyloidoses, calling for further studies.

The recent approval of three drugs for the treatment of amyloid transthyretin (ATTR) amyloidosis, both hereditary and wild-type, has opened a new era in the care of these diseases. ATTR amyloidosis is embedded in its pathophysiology, and the drugs target critical steps of the amyloid cascade. In addition to liver transplant, which removes the pathogenic variants, the introduction of gene silencers has allowed the suppression of both wild type and mutant transthyretin (TTR), thus extending the potential therapeutic range to wild-type cardiac amyloidosis. The kinetic stabilisation of TTR using small molecules has proved to be clinically effective both for amyloid neuropathy and cardiomyopathy. Gene silencers and kinetic stabilizers were recently approved on the basis of the outcome of phase III trials; however, comparative trials have not been performed, making it difficult to draw recommendations. Indications for liver transplantation have narrowed considerably. Here, guidelines for therapy are proposed based on expert consensus, acknowledging that the several drugs currently undergoing clinical trials will probably change in the near future the therapeutic armamentarium and, consequently, the therapeutic strategy. Indications for monitoring disease progression and drug efficacy are also provided for the management of these complexes, but now very treatable, diseases.

A reliable diagnosis of amyloidosis is usually based on a tissue biopsy. With increasing options for specific treatments of the different amyloid diseases, an exact and valid diagnosis including determination of the biochemical fibril nature is imperative. Biopsy sites as well as amyloid typing principles vary and this paper describes methods employed at some laboratories specialised in amyloidosis in Europe, Japan and USA.

Background Hereditary transthyretin amyloidosis (hATTR/ATTRv) results from the deposition of misfolded transthyretin (TTR) throughout the body, including peripheral nerves. Inotersen, an antisense oligonucleotide inhibitor of hepatic TTR production, demonstrated a favorable efficacy and safety profile in patients with the polyneuropathy associated with hATTR in the NEURO-TTR (NCT01737398) study. We report longer-term efficacy and safety data for inotersen, with a median treatment exposure of 3 years. Methods Patients who satisfactorily completed NEURO-TTR were enrolled in its open-label extension (OLE) study. Efficacy assessments included the modified Neuropathy Impairment Score + 7 (mNIS + 7), Norfolk Quality of Life–Diabetic Neuropathy (Norfolk QoL-DN) questionnaire total score, and the Short Form 36 (SF-36v2) Health Survey Physical Component Summary score. Safety and tolerability were also assessed. Efficacy is reported for patients living in Europe and North America (this cohort completed the study approximately 9 months before the remaining group of patients outside these regions); safety is reported for the full safety dataset, comprising patients living in Europe, North America, and Latin America/Australasia. This study is registered with ClinicalTrials.gov, identifier NCT02175004. Results In the Europe and North America cohort of the NEURO-TTR study, 113/141 patients (80.1%) completed the study, and 109 patients participated in the OLE study. A total of 70 patients continued to receive inotersen (inotersen–inotersen) and 39 switched from placebo to inotersen (placebo–inotersen). The placebo–inotersen group demonstrated sustained improvement in neurological disease progression as measured by mNIS + 7, compared with predicted worsening based on projection of the NEURO-TTR placebo data (estimated natural history). The inotersen–inotersen group demonstrated sustained benefit, as measured by mNIS + 7, Norfolk QoL-DN, and SF-36v2, compared with estimated natural history as well as compared with the placebo–inotersen group. With a maximum exposure of 6.2 years, inotersen was not associated with any additional safety concerns or increased toxicity in the OLE study. Platelet and renal monitoring were effective in reducing the risk of severe adverse events in the OLE study. Conclusion Inotersen treatment for > 3 years slowed progression of the polyneuropathy associated with hATTR, and no new safety signals were observed.

Hereditary transthyretin amyloidosis (hATTR), a progressive, debilitating, and ultimately fatal disease, causes multisystem dysfunction. We report long-term efficacy and safety for inotersen, an antisense oligonucleotide inhibitor of transthyretin protein production.

Background Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is a fatal condition, leading to heart failure (HF) and ultimately death. ATTR-CM is caused by misfolding and aggregation of transthyretin (TTR), a protein produced by the liver. Depending on the presence or absence of a destabilizing mutation in the TTR gene, the disease can be classified as hereditary ATTR-CM (hATTR-CM) or wild-type ATTR-CM (wtATTR-CM), respectively. Despite the treatment with a TTR stabilizer, tafamidis, recently approved in the United States for the treatment of ATTR-CM, disease progression still occurs. AKCEA-TTR-LRX (ION-682884) is an antisense oligonucleotide (ASO) that inhibits the production of TTR. It has a similar design and sequence as inotersen (the parent compound), but is conjugated to a triantennary N-acetyl galactosamine (GalNAc3) moiety for selective receptor-mediated delivery to hepatocytes, the principal source of systemically circulating TTR. This delivery approach has yielded an up to 30-fold increase in potency and improved the safety and tolerability profiles of ASOs in human clinical trials. Conjugation of this ligand allows the use of a lower dose to achieve improved pharmacodynamic results. In a phase 1, randomized, placebo-controlled study, AKCEA-TTR-LRX given at a 45 mg, 60 mg or 90 mg dose, by subcutaneous (SC) injection every four weeks in 36 healthy volunteers achieved a mean pre-steady state reduction in serum TTR of 86%, 91% and 94%, respectively, compared to baseline. The dosage regimen of 45 mg SC every four weeks (27-fold lower exposure vs the inotersen dose in NEURO-TTR trial) was chosen for the pivotal phase 3 study. Methods CARDIO-TTRansform (ClinicalTrials.gov NCT04136171) is a Phase 3 global, double-blind, randomized, placebo-controlled study assessing the efficacy and safety of AKCEA-TTR-L Rx in hATTR-CM or wtATTR-CM patients receiving available background standard of care (SoC) therapy. Approximately 750 patients around the world with a history of HF due to ATTR-CM will be randomized 1:1 to receive either AKCEA-TTR-LRx 45 mg or placebo administered by SC injection once every 4 weeks. Key inclusion criteria include diagnosis of ATTR-CM by biopsy or positive PYP/DPD/HMDP scan, interventricular septum thickness >12mm, NT-proBNP > 600 pg/mL, NYHA class I-III and 6-minute walk distance (6MWD) >150 m. Key exclusion criteria include, platelet count < 125 × 109\L and urine protein/creatinine ratio >= 750 mg/g. Concomitant treatment with tafamidis as SoC for ATTR-CM is allowed. The study consists of a 120-week Treatment Period. Primary efficacy endpoint is the composite of cardiovascular (CV) mortality and recurrent CV clinical events at Week 120 study visit using the Andersen-Gill method. Secondary endpoints include the change from baseline in the 6MWD, KCCQ score, CV clinical events, CV death and all-cause of mortality at Week 120. Conclusions Despite recent advances, additional efficacious, safe and convenient treatment options for ATTR-CM are needed. The CARDIO-TTRansform trial is a large Phase 3 trial designed to evaluate the clinical efficacy and safety of AKCEA-TTR-LRx compared to placebo in patients with ATTR-CM receiving available SoC therapy. Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is a fatal condition, leading to heart failure (HF) and ultimately death. ATTR-CM is caused by misfolding and aggregation of transthyretin (TTR), a protein produced by the liver. Depending on the presence or absence of a destabilizing mutation in the TTR gene, the disease can be classified as hereditary ATTR-CM (hATTR-CM) or wild-type ATTR-CM (wtATTR-CM), respectively. Despite the treatment with a TTR stabilizer, tafamidis, recently approved in the United States for the treatment of ATTR-CM, disease progression still occurs. AKCEA-TTR-LRX (ION-682884) is an antisense oligonucleotide (ASO) that inhibits the production of TTR. It has a similar design and sequence as inotersen (the parent compound), but is conjugated to a triantennary N-acetyl galactosamine (GalNAc3) moiety for selective receptor-mediated delivery to hepatocytes, the principal source of systemically circulating TTR. This delivery approach has yielded an up to 30-fold increase in potency and improved the safety and tolerability profiles of ASOs in human clinical trials. Conjugation of this ligand allows the use of a lower dose to achieve improved pharmacodynamic results. In a phase 1, randomized, placebo-controlled study, AKCEA-TTR-LRX given at a 45 mg, 60 mg or 90 mg dose, by subcutaneous (SC) injection every four weeks in 36 healthy volunteers achieved a mean pre-steady state reduction in serum TTR of 86%, 91% and 94%, respectively, compared to baseline. The dosage regimen of 45 mg SC every four weeks (27-fold lower exposure vs the inotersen dose in NEURO-TTR trial) was chosen for the pivotal phase 3 study. CARDIO-TTRansform (ClinicalTrials.gov NCT04136171) is a Phase 3 global, double-blind, randomized, placebo-controlled study assessing the efficacy and safety of AKCEA-TTR-L Rx in hATTR-CM or wtATTR-CM patients receiving available background standard of care (SoC) therapy. Approximately 750 patients around the world with a history of HF due to ATTR-CM will be randomized 1:1 to receive either AKCEA-TTR-LRx 45 mg or placebo administered by SC injection once every 4 weeks. Key inclusion criteria include diagnosis of ATTR-CM by biopsy or positive PYP/DPD/HMDP scan, interventricular septum thickness >12mm, NT-proBNP > 600 pg/mL, NYHA class I-III and 6-minute walk distance (6MWD) >150 m. Key exclusion criteria include, platelet count < 125 × 109\L and urine protein/creatinine ratio >= 750 mg/g. Concomitant treatment with tafamidis as SoC for ATTR-CM is allowed. The study consists of a 120-week Treatment Period. Primary efficacy endpoint is the composite of cardiovascular (CV) mortality and recurrent CV clinical events at Week 120 study visit using the Andersen-Gill method. Secondary endpoints include the change from baseline in the 6MWD, KCCQ score, CV clinical events, CV death and all-cause of mortality at Week 120. Despite recent advances, additional efficacious, safe and convenient treatment options for ATTR-CM are needed. The CARDIO-TTRansform trial is a large Phase 3 trial designed to evaluate the clinical efficacy and safety of AKCEA-TTR-LRx compared to placebo in patients with ATTR-CM receiving available SoC therapy.

Abstract Background/Introduction Cardiomyopathy (CM) with associated heart failure and polyneuropathy (PN) are common manifestations of hereditary transthyretin amyloidosis (ATTRv), a progressive, debilitating, and fatal disease that results from the deposition of misfolded transthyretin (TTR) protein throughout the body. NEURO-TTR (NCT01737398) showed that inotersen, an antisense oligonucleotide inhibitor of TTR protein production, slowed the progression of PN and maintained quality of life in patients with ATTRv. Purpose To report efficacy and safety from the open-label extension (OLE) of the NEURO-TTR study in patients with ATTRv PN overall and in CM subgroups. Methods Patients who completed NEURO-TTR, enrolled in the OLE (NCT02175004), and either switched from placebo in NEURO-TTR to inotersen in the OLE (placebo-inotersen) or received inotersen in NEURO-TTR and remained on inotersen in the OLE (inotersen-inotersen) were included. Assessments included the modified Neuropathy Impairment Score +7 composite score (mNIS+7 [range –22.3 to 346.3], a measure of neuropathy with higher scores indicative of poorer function), TTR levels, and safety monitoring. Utilizing patients from Europe and North America (EU+NA) as of 28 July 2020, this post hoc analysis examined two subgroups: CM ECHO and severe CM ECHO. CM was defined as a diagnosis of ATTRv CM at study entry or all of the following criteria: a left ventricular wall thickness of ≥1.3 cm on transthoracic echocardiography at baseline, no known history of persistent hypertension (systolic blood pressure ≥150 mm Hg) within 12 months before study screening, and evaluable baseline ECHO obtained by central assessment. Severe CM was defined as an interventricular septum thickness ≥1.5 cm at baseline. Descriptive statistics are reported. Results In the overall population and both CM subgroups, the placebo-inotersen group demonstrated slowing of neurological disease progression compared with natural history based on NEURO-TTR placebo projection (estimated natural history will be presented). Furthermore, in the overall population and both CM subgroups, the inotersen-inotersen group demonstrated sustained benefit compared with the placebo-inotersen group (Table). Change in serum TTR levels will be presented. There have been no reports of grade 4 thrombocytopenia or acute glomerulonephritis under enhanced monitoring in patients in the EU+NA despite the increased duration of exposure. No new safety concerns were identified. Conclusions Inotersen treatment for >3 years slowed the progression of PN associated with ATTRv in patients with CM, including severe CM. In both subgroups, greater neurological preservation was observed in those who initiated inotersen earlier (inotersen-inotersen group), underscoring the benefits of early treatment. No new safety signals were detected in this OLE analysis; enhanced monitoring is successful in managing the risk for thrombocytopenia and acute glomerulonephritis. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): This study was sponsored by Akcea Therapeutics, an affiliate of Ionis Pharmaceuticals, Inc.

AA amyloidosis is a disease caused by extracellular deposition of insoluble β-pleated sheet fibrils composed of amyloid A (AA) protein, an amino (N)-terminal fragment of serum amyloid A (SAA). The deposits disrupt tissue structure and compromise organ function. Although the disease is systemic, deposition in kidney glomeruli is the most common manifestation. The leading cause of AA amyloidosis is sustained or recurrent inflammation accompanied by elevated levels of SAA. Factors determining the conversion of SAA to AA amyloid fibrils have yet to be fully resolved. Herein, we present liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis of AA proteins purified from eight patients with AA amyloidosis. For the first time, post-translational modifications (PTM), including carbamylation, acetylation and oxidation, were identified on AA peptides; all eight samples showed some degree of PTM. The amyloid in 6 samples comprised peptides derived from SAA1 with few or none from SAA2, while the other two samples contained both SAA1- and SAA2-derived peptides. N-terminal AA peptides beginning with Arg1 as well as AA peptides starting with Ser2 were present in five of the eight samples, while all or nearly all of the N-terminal peptides in the other three samples lacked Arg1. These data demonstrate that multiple species of AA amyloid proteins can comprise the subunits in amyloid fibrils and raise the possibility that PTM may play a role in fibrillogenesis.

AKCEA-TTR-LRx is a ligand-conjugated antisense (LICA) drug in development for the treatment of hereditary transthyretin amyloidosis (hATTR), a fatal disease caused by mutations in the transthyretin (TTR) gene. AKCEA-TTR-LRx shares the same nucleotide sequence as inotersen, an antisense medicine approved for use in hATTR polyneuropathy (hATTR-PN). Unlike inotersen, AKCEA-TTR-LRx is conjugated to a triantennary N-acetylgalactosamine moiety that supports receptor-mediated uptake by hepatocytes, the primary source of circulating TTR. This advanced design increases drug potency to allow for lower and less frequent dosing. The NEURO-TTRansform study will investigate whether AKCEA-TTR-LRx is safe and efficacious, with the aim of improving neurologic function and quality of life in hATTR-PN patients. Approximately 140 adults with stage 1 (independent ambulation) or 2 (requires ambulatory support) hATTR-PN are anticipated to enroll in this multicenter, open-label, randomized, phase 3 study. Patients will be assigned 6:1 to AKCEA-TTR-LRx 45 mg subcutaneously every 4 weeks or inotersen 300 mg once weekly until the prespecified week 35 interim efficacy analysis, after which patients receiving inotersen will receive AKCEA-TTR-LRx 45 mg subcutaneously every 4 weeks. All patients will then receive AKCEA-TTR-LRx through the remainder of the study treatment period. The final efficacy analysis at week 66 will compare the AKCEA-TTR-LRx arm with the historical placebo arm from the phase 3 trial of inotersen (NEURO-TTR). The primary outcome measures are between-group differences in the change from baseline in serum TTR, modified Neuropathy Impairment Score + 7, and Norfolk Quality of Life—Diabetic Neuropathy questionnaire. NEURO-TTRansform is designed to determine whether targeted delivery of AKCEA-TTR-LRx to hepatocytes with lower and less frequent doses will translate into clinical and quality-of-life benefits for patients with hATTR-PN. The study is registered at ClinicalTrials.gov (NCT04136184) and EudraCT (2019-001698-10).

Abstract Aims Amyloidogenic transthyretin (ATTR) amyloidosis is a fatal disease characterized by progressive cardiomyopathy and/or polyneuropathy. AKCEA‐TTR‐LRx (ION‐682884) is a ligand‐conjugated antisense drug designed for receptor‐mediated uptake by hepatocytes, the primary source of circulating transthyretin (TTR). Enhanced delivery of the antisense pharmacophore is expected to increase drug potency and support lower, less frequent dosing in treatment. Methods and results AKCEA‐TTR‐LRx demonstrated an approximate 50‐fold and 30‐fold increase in potency compared with the unconjugated antisense drug, inotersen, in human hepatocyte cell culture and mice expressing a mutated human genomic TTR sequence, respectively. This increase in potency was supported by a preferential distribution of AKCEA‐TTR‐LRx to liver hepatocytes in the transgenic hTTR mouse model. A randomized, placebo‐controlled, phase 1 study was conducted to evaluate AKCEA‐TTR‐LRx in healthy volunteers (ClinicalTrials.gov: NCT03728634). Eligible participants were assigned to one of three multiple‐dose cohorts (45, 60, and 90 mg) or a single‐dose cohort (120 mg), and then randomized 10:2 (active : placebo) to receive a total of 4 SC doses (Day 1, 29, 57, and 85) in the multiple‐dose cohorts or 1 SC dose in the single‐dose cohort. The primary endpoint was safety and tolerability; pharmacokinetics and pharmacodynamics were secondary endpoints. All randomized participants completed treatment. No serious adverse events were reported. In the multiple‐dose cohorts, AKCEA‐TTR‐LRx reduced TTR levels from baseline to 2 weeks after the last dose of 45, 60, or 90 mg by a mean (SD) of −85.7% (8.0), −90.5% (7.4), and −93.8% (3.4), compared with −5.9% (14.0) for pooled placebo (P < 0.001). A maximum mean (SD) reduction in TTR levels of −86.3% (6.5) from baseline was achieved after a single dose of 120 mg AKCEA‐TTR‐LRx. Conclusions These findings suggest an improved safety and tolerability profile with the increase in potency achieved by productive receptor‐mediated uptake of AKCEA‐TTR‐LRx by hepatocytes and supports further development of AKCEA‐TTR‐LRx for the treatment of ATTR polyneuropathy and cardiomyopathy.

The outlook for transthyretin amyloidosis (ATTR) is changing with the availability of new and emerging treatments. ATTR now appears to be more common than previously thought and is no longer viewed as an obscure diagnosis with a grim prognosis. Now more than ever, there is growing emphasis on the need for early diagnosis because the treatments appear to be most effective if started in earlier stages of the disease. Diagnosing ATTR is a challenge as it may initially present with nonspecific symptoms and it is often thought of as a diagnosis of exclusion. Increased awareness is imperative as new treatments offer hope and have the potential to change the disease trajectory. ATTR commonly presents with neurological and cardiac features. Transthyretin (TTR) is a protein produced in the liver which misfolds either due to genetic mutations or due to aging and results in deposition of amyloid fibrils in organs and tissues. Apart from the traditional imaging modalities, newer techniques including echocardiographic strain imaging, magnetic resonance imaging (MRI), and nuclear scintigraphy, as well as the increased availability of genetic testing are aiding in making a timely diagnosis. In this review, we present the current understanding of the ATTR disease process, diagnostic and surveillance approaches, newer treatment modalities, and the future directions.

Objective To examine the impact on quality of life (QOL) of patients with hATTR amyloidosis with polyneuropathy treated with inotersen (Tegsedi™) versus placebo. Methods Data were from the NEURO-TTR trial (ClinicalTrials.gov Identifier: NCT01737398), a phase 3, multinational, randomized, double-blind, placebo-controlled study of inotersen in patients with hATTR amyloidosis with polyneuropathy. At baseline and week 66, QOL measures—the Norfolk-QOL-Diabetic Neuropathy (DN) questionnaire and SF-36v2 ® Health Survey (SF-36v2)—were assessed. Treatment differences in mean changes in QOL from baseline to week 66 were tested using mixed-effect models with repeated measures. Responder analyses compared the percentages of patients whose QOL meaningfully improved or worsened from baseline to week 66 in inotersen and placebo arms. Descriptive analysis of item responses examined treatment differences in specific activities and functions at week 66. Results Statistically significant mean differences between treatment arms were observed for three of five Norfolk-QOL-DN domains and five of eight SF-36v2 domains, with better outcomes for inotersen than placebo in physical functioning, activities of daily living, neuropathic symptoms, pain, role limitations due to health problems, and social functioning. A larger percentage of patients in the inotersen arm than the placebo arm showed preservation or improvement in Norfolk-QOL-DN and SF-36v2 scores from baseline to week 66. Responses at week 66 showed more substantial problems with daily activities and functioning for patients in the placebo arm than in the inotersen arm. Conclusion Patients with hATTR amyloidosis with polyneuropathy treated with inotersen showed preserved or improved QOL at 66 weeks compared to those who received placebo.

Peripheral neuropathies are among the most common inherited neurologic diseases. Neuropathy may be the key feature of an inherited disease or overshadowed by the other manifestations of a syndrome. Inherited demyelinating neuropathies are usually caused by mutations in genes expressed by myelinating Schwann cells. Inherited axonal neuropathies are mainly caused by mutations in genes expressed by neurons, with some important exceptions, such as the genes that cause familial amyloidotic neuropathies. Mutations in more than 100 different genes cause nonsyndromic neuropathies, and mutations in 200 other genes cause neuropathy that is part of a syndrome.