The discovery and development of transthyretin amyloidogenesis inhibitors: what are the lessons?

Transthyretin (TTR) is associated with several human amyloid diseases. Various kinetic stabilizers have been developed to inhibit the dissociation of TTR tetramer and the formation of amyloid fibrils. Most of them are bisaryl derivatives, natural flavonoids, crown ethers and carborans. In this review article, we focus on TTR tetramer stabilizers, genetic therapeutic approaches and fibril remodelers. The binding modes of typical bisaryl derivatives, natural flavonoids, crown ethers and carborans are discussed. Based on knowledge of the binding of thyroxine to TTR tetramer, many stabilizers have been screened to dock into the thyroxine binding sites, leading to TTR tetramer stabilization. Particularly, those stabilizers with unique binding profiles have shown great potential in developing the therapeutic management of TTR amyloidogenesis.

Overcoming GNA/RNA base-pairing limitations using isonucleotides improves the pharmacodynamic activity of ESC+ GalNAc-siRNAs.

We recently reported that RNAi-mediated off-target effects are important drivers of the hepatotoxicity observed for a subset of GalNAc-siRNA conjugates in rodents, and that these findings could be mitigated by seed-pairing destabilization using a single GNA nucleotide placed within the seed region of the guide strand. Here, we report further investigation of the unique and poorly understood GNA/RNA cross-pairing behavior to better inform GNA-containing siRNA design. A reexamination of published GNA homoduplex crystal structures, along with a novel structure containing a single (S)-GNA-A residue in duplex RNA, indicated that GNA nucleotides universally adopt a rotated nucleobase orientation within all duplex contexts. Such an orientation strongly affects GNA-C and GNA-G but not GNA-A or GNA-T pairing in GNA/RNA heteroduplexes. Transposition of the hydrogen-bond donor/acceptor pairs using the novel (S)-GNA-isocytidine and -isoguanosine nucleotides could rescue productive base-pairing with the complementary G or C ribonucleotides, respectively. GalNAc-siRNAs containing these GNA isonucleotides showed an improved in vitro activity, a similar improvement in off-target profile, and maintained in vivo activity and guide strand liver levels more consistent with the parent siRNAs than those modified with isomeric GNA-C or -G, thereby expanding our toolbox for the design of siRNAs with minimized off-target activity.

Repositioning of the Anthelmintic Drugs Bithionol and Triclabendazole as Transthyretin Amyloidogenesis Inhibitors.

Transthyretin (TTR) is a causative protein of TTR amyloidosis (ATTR amyloidosis), a general term for diseases characterized by deposition of TTR amyloid fibrils in specific organs. ATTR amyloidosis can be ameliorated by stabilization of the TTR tetramer through the binding of small molecules. Here, we show that the clinical anthelmintic drugs bithionol (42) and triclabendazole (43) potently inhibit aggregation of the amyloidogenic variant V30M-TTR. A competitive binding assay using a fluorescence probe showed that the binding affinity of 42 with V30M-TTR was significantly higher than that of the first-in-class drug tafamidis (1), and the binding affinity of 43 was similar to that of 1. The crystallographic and thermodynamic analysis revealed that 42 efficiently occupied the halogen-binding grooves of TTR, resulting in the favorable binding entropy. Multifaceted in vitro studies of anthelmintic drugs have the potential to reposition these drugs as ATTR amyloidosis inhibitors.

Targeting transthyretin in Alzheimer's disease: Drug discovery of small-molecule chaperones as disease-modifying drug candidates for Alzheimer's disease.

Transthyretin (TTR) has a well-established role in neuroprotection in Alzheimer's Disease (AD). We have setup a drug discovery program of small-molecule compounds that act as chaperones enhancing TTR/Amyloid-beta peptide (Aß) interactions. A combination of computational drug repurposing approaches and in vitro biological assays have resulted in a set of molecules which were then screened with our in-house validated high-throughput screening ternary test. A prioritized list of chaperones was obtained and corroborated with ITC studies. Small-molecule chaperones have been discovered, among them our lead compound Iododiflunisal (IDIF), a molecule in the discovery phase; one investigational drug (luteolin); and 3 marketed drugs (sulindac, olsalazine and flufenamic), which could be directly repurposed or repositioned for clinical use. Not all TTR tetramer stabilizers behave as chaperones in vitro. These chemically diverse chaperones will be used for validating TTR as a target in vivo, and to select one repurposed drug as a candidate to enter clinical trials as AD disease-modifying drug.

Patisiran e Inotersen en amiloidosis familiar mediada por transtiretina / Patisiran and Inotersen in familial amyloidosis transthyretin-mediated

CONTEXTO: La amiloidosis constituye un amplio espectro de enfermedades que se caracterizan por el depósito extracelular de un material fibrilar, generando depósitos insolubles y tóxicos en diferentes tejidos en forma de haces con conformación anómala de láminas beta cruzada, conocida como amiloide. El amiloide acumulado puede provocar daño celular y deterioro de la función de los órganos. Se sabe que al menos 30 proteínas humanas forman fibrillas amiloides. Una de sus formas es, la amiloidosis por transtiretina (ATTR), una enfermedad multisistémica, progresiva, que resulta del mal plegamiento, agregación y depósito de la proteína transportadora transtiretina (TTR), en varios tejidos del cuerpo. La Sociedad Internacional de Amiloidosis ha definido dos formas principales de este tipo de amiloidosis: la amiloidosis ATTR adquirida, denominada amiloidosis ATTRwt (wt por por sus siglas en inglés, wild-type) y la amiloidosis ATTR hereditaria, denominada hATTR (de sus siglas en inglés hereditary transthyretin amyloidosis), que se desarrolla como resultado de mutaciones en el gen TTR; que en consecuencia desestabiliza la proteína. Se estima que su prevalencia global es de 0,87 a 1,1 por millón de personas. Aproximadamente, 50000 personas padecen esta enfermedad en todo el mundo. Su presentación suele darse entre, la tercera y quinta década de la vida y de no tratarse, los síntomas de la ATTR son progresivos pudiendo llegar a causar la muerte, la que suele producirse entre tres y 15 años después de la presentación. TECNOLOGÍA: Los inhibidores de los precursores de amiloide, son fármacos conocidos como oligonucleótidos, que actúan en el interior de la célula a nivel del ARN. Tienen la capacidad de degradar o "silenciar" el ARN mensajero (ARNm), de esta forma, inhiben la síntesis hepática de la proteína TTR por interferência del ARNm. Por consiguiente, se bloquea la expresión de la proteína TTR, reduciendo la síntesis de la proteína precursora del amiloide. OBJETIVO: El objetivo del presente informe es evaluar la evidencia disponible acerca de la eficacia, seguridad y aspectos relacionados a las políticas de cobertura del uso de patisiran e inotersen en pacientes con amiloidosis familiar mediada por transtiretina. MÉTODOS: Se realizó una búsqueda en las principales bases de datos bibliográficas, en buscadores genéricos de internet, y financiadores de salud. Se priorizó la inclusión de revisiones sistemáticas (RS), ensayos clínicos controlados aleatorizados (ECAs), evaluaciones de tecnologías sanitarias (ETS), evaluaciones económicas, guías de práctica clínica (GPC) y políticas de cobertura de diferentes sistemas de salud. RESULTADOS: Se incluyeron tres ECAs, dos RS, tres GPC,siete evaluaciones económicas, y ocho informes de políticas de cobertura de patisirán e inotersen para amiloidosis familiar mediada por transtiretina. CONCLUSIONES: Evidencia de moderada calidad muestra que el uso de patisiran en pacientes con polineuropatia (estadio 1 y estadio 2) por amiloidosis familiar hereditaria mediada por transtiretina, probablemente presente una mejoría considerable de la polineuropatía y calidad de vida con respecto al cuidado usual. Si bien el patisirán presentó efectos adversos leves o moderados, estos fueron bien tolerados. No se observaron diferencias significativas en la mortalidad entre el patisiran y el cuidado usual. Evidencia de moderada calidad muestra que el uso de inotersen en pacientes con polineuropatia (estadio 1 y estadio 2) por amiloidosis familiar hereditaria mediada por trasntiretina, probablemente presente una mejoría considerable de la polineuropatía y calidad de vida con respecto a no usarlo. El uso de inotersen en comparación con el cuidado usual más placebo presentó efectos adversos importantes, tales como a glomerulonefritis y plaquetopenia. No se ha encontrado evidencia que compare en forma directa el patisiran con el inotersen, ni con otras drogas activas para el tratamiento de la amiloidosis familiar hereditaria mediada por transtiretina. Es por ello que la interpretación de la magnitud del beneficio neto de cada una fue realizada de manera indirecta y a través del juicio de valores del equipo de investigación. Por lo que estos efectos "comparativos" deben ser evaluados con cautela debido a las importantes diferencias entre los estudios, en cuanto a su población, tiempo de tratamiento y mínimas diferencias en las escalas utilizadas para la evaluación de la severidad de la polineuropatía. Esta evidencia sugeriría que probablemente el uso de patisiran podría favorecer a una reducción en la progresión de la polineuropatía y una mejoría en la calidad de vida en comparación con el inotersen. Hasta la fecha, no hay estudios que evalúen la seguridad y la eficacia de estas drogas en el subgrupo de pacientes con amiloidosis cardiaca. Solamente existe información basada en análisis de subgrupos de los ensayos clínicos disponibles, de los cuales no se obtuvieron resultados concluyentes. El patisiran e inotersen no se encuentran aprobadas aún en Argentina, por lo que su uso es compassivo o en el contexto de estudios clínicos. Ambas drogas se encuentran aprobadas por la Agencia Europea de Medicamentos y la Administración de Alimentos y Medicamentos de los Estados Unidos. Existe un consenso entre las guías de práctica clínica relevadas en recomendar el uso de patisiran o inotersen para el tratamiento de pacientes con polineuropatía (estadio 1 y estadio 2) en amiloidosis familiar hereditaria medida por transtiretina, considerando que la enfermedad es devastadora tanto para el paciente como para los familiares y que los resultados de los estudios, si bien, no son a largo plazo, fueron significativos para evitar la progresión de la polineuropatía. No se dispone de información económica respecto a estas drogas en Argentina, los datos son relevados de principalmente de sistemas de salud internacionales, tales como el sistema de salud del Reino Unido, que previo a un acuerdo comercial confidencial -por lo que se desconoce el precio convenido- , consideraron que ambas drogas resultaron costo efectivas para el umbral de pago de ese sistema de salud para el caso de enfermedades severas ultrararas, en las que contemplan umbrales de costo-efectividad hasta diez veces superiores al estándar. Sin embargo, no es posible realizar esa asunción para el sistema de salud de Argentina.

The Ultrastructure of Tissue Damage by Amyloid Fibrils.

Amyloidosis is a group of diseases that includes Alzheimer's disease, prion diseases, transthyretin (ATTR) amyloidosis, and immunoglobulin light chain (AL) amyloidosis. The mechanism of organ dysfunction resulting from amyloidosis has been a topic of debate. This review focuses on the ultrastructure of tissue damage resulting from amyloid deposition and therapeutic insights based on the pathophysiology of amyloidosis. Studies of nerve biopsy or cardiac autopsy specimens from patients with ATTR and AL amyloidoses show atrophy of cells near amyloid fibril aggregates. In addition to the stress or toxicity attributable to amyloid fibrils themselves, the toxicity of non-fibrillar states of amyloidogenic proteins, particularly oligomers, may also participate in the mechanisms of tissue damage. The obscuration of the basement and cytoplasmic membranes of cells near amyloid fibrils attributable to an affinity of components constituting these membranes to those of amyloid fibrils may also play an important role in tissue damage. Possible major therapeutic strategies based on pathophysiology of amyloidosis consist of the following: (1) reducing or preventing the production of causative proteins; (2) preventing the causative proteins from participating in the process of amyloid fibril formation; and/or (3) eliminating already-deposited amyloid fibrils. As the development of novel disease-modifying therapies such as short interfering RNA, antisense oligonucleotide, and monoclonal antibodies is remarkable, early diagnosis and appropriate selection of treatment is becoming more and more important for patients with amyloidosis.

A human antibody selective for transthyretin amyloid removes cardiac amyloid through phagocytic immune cells.

Transthyretin amyloid (ATTR) cardiomyopathy is a debilitating disease leading to heart failure and death. It is characterized by the deposition of extracellular ATTR fibrils in the myocardium. Reducing myocardial ATTR load is a therapeutic goal anticipated to translate into restored cardiac function and improved patient survival. For this purpose, we developed the selective anti-ATTR antibody NI301A, a recombinant human monoclonal immunoglobulin G1. NI301A was cloned following comprehensive analyses of memory B cell repertoires derived from healthy elderly subjects. NI301A binds selectively with high affinity to the disease-associated ATTR aggregates of either wild-type or variant ATTR related to sporadic or hereditary disease, respectively. It does not bind physiological transthyretin. NI301A removes ATTR deposits ex vivo from patient-derived myocardium by macrophages, as well as in vivo from mice grafted with patient-derived ATTR fibrils in a dose- and time-dependent fashion. The biological activity of ATTR removal involves antibody-mediated activation of phagocytic immune cells including macrophages. These data support the evaluation of safety and tolerability of NI301A in an ongoing phase 1 clinical trial in patients with ATTR cardiomyopathy.

Syntheses of Morpholine-Based Nucleotide Analogs for Hepatic siRNA Targeting and Stabilization.

A morpholine-based nucleotide analog was developed as a building block for hepatic siRNA targeting and stabilization. Attachment of an asialoglycoprotein-binding GalNAc ligand at the morpholine nitrogen was realized with different linkers. The obtained morpholino GalNAc scaffolds were coupled to the sense strand of a transthyretin-targeting siRNA and tested for their knockdown potency in vitro and in vivo. A clear structure-activity relationship was developed with regard to the linker type and length as well as the attachment site of the morpholino GalNAc moieties at the siRNA sense strand. Further, simple alkylation of the morpholine nitrogen led to a nucleotide analog, which increased siRNA stability, when used as a double 3'-overhang at the sense strand sequence. Combination of the best morpholino GalNAc building blocks as targeting nucleotides with an optimized stabilizing alkyl-substituted morpholine as 3'-overhangs resulted in siRNAs without any phosphorothioate stabilization in the sense strand and clearly improved the duration of action in vivo.

Optimization of kinetic stabilizers of tetrameric transthyretin: A prospective ligand efficiency-guided approach.

In the past few years, attempts have been made to use decision criteria beyond Lipinski's guidelines (Rule of five) to guide drug discovery projects more effectively. Several variables and formulations have been proposed and investigated within the framework of multiparameter optimization methods to guide drug discovery. In this context, the combination of Ligand Efficiency Indices (LEI) has been predominantly used to map and monitor the drug discovery process in a retrospective fashion. Here we provide an example of the use of a novel application of the LEI methodology for prospective lead optimization by using the transthyretin (TTR) fibrillogenesis inhibitor iododiflunisal (IDIF) as example. Using this approach, a number of compounds with theoretical efficiencies higher than the reference compound IDIF were identified. From this group, ten compounds were selected, synthesized and biologically tested. Half of the compounds (5, 6, 7, 8 and 10) showed potencies in terms of IC50 inhibition of TTR aggregation equal or higher than the lead compound. These optimized compounds mapped within the region of more efficient candidates in the corresponding experimental nBEI-NSEI plot, matching their position in the theoretical optimization plane that was used for the prediction. Due to their upstream (North-Eastern) position in the progression lines of NPOL = 3 or 4 of the nBEI-NSEI plot, three of them (5, 6 and 8) are more interesting candidates than iododiflunisal because they have been optimized in the three crucial LEI variables of potency, size and polarity at the same time. This is the first example of the effectiveness of using the combined LEIs within the decision process to validate the application of the LEI formulation for the prospective optimization of lead compounds.

Transthyretin Amyloidogenesis Inhibitors: From Discovery to Current Developments.

Transthyretin (TTR) is a homotetrameric protein in human plasma. The dissociation of the TTR tetramer and misfolding of the TTR monomer result in the formation of amyloid fibrils. Hereditary TTR amyloidosis is characterized by the extracellular deposition of amyloid fibrils containing TTR variants. The development of small molecules that kinetically stabilize the TTR tetramer is one of the effective strategies for the treatment of hereditary TTR amyloidosis. So far, several stabilizers have been discovered. Tafamidis is the only approved stabilizer for treatment of hereditary TTR amyloidosis, although two nucleic acid medicines that inhibit TTR synthesis, inotersen and patisiran, were recently approved for treatment of this disorder. In this Perspective, we seek to describe the representative kinetic stabilizers from discovery to development, interweaving the crystallographic study of the complex structures.

Investigating the pharmacodynamic durability of GalNAc-siRNA conjugates.

One hallmark of trivalent N-acetylgalactosamine (GalNAc)-conjugated siRNAs is the remarkable durability of silencing that can persist for months in preclinical species and humans. Here, we investigated the underlying biology supporting this extended duration of pharmacological activity. We found that siRNA accumulation and stability in acidic intracellular compartments is critical for long-term activity. We show that functional siRNA can be liberated from these compartments and loaded into newly generated Argonaute 2 protein complexes weeks after dosing, enabling continuous RNAi activity over time. Identical siRNAs delivered in lipid nanoparticles or as GalNAc conjugates were dose-adjusted to achieve similar knockdown, but only GalNAc-siRNAs supported an extended duration of activity, illustrating the importance of receptor-mediated siRNA trafficking in the process. Taken together, we provide several lines of evidence that acidic intracellular compartments serve as a long-term depot for GalNAc-siRNA conjugates and are the major contributor to the extended duration of activity observed in vivo.

Immunogenicity Assessment of Inotersen, a 2'-O-(2-Methoxyethyl) Antisense Oligonucleotide in Animals and Humans: Effect on Pharmacokinetics, Pharmacodynamics, and Safety.

Inotersen (TEGSEDI™) is a 2'-O-(2-methoxyethyl)-modified antisense oligonucleotide, intended for treating hereditary transthyretin (TTR) amyloidosis with polyneuropathy. The potential immunogenicity (IM) response to inotersen was evaluated in chronic nonclinical safety studies and the pivotal phase 2/3 clinical study. The evaluation was designed to assess the characteristics of antidrug antibodies (ADAs) and their effects on the pharmacokinetics, pharmacodynamics, clinical efficacy, and safety in animals and humans. No immunogenic response was observed after long-term treatment with inotersen in mice. In monkeys, the incidence rate of IM to inotersen appeared to be dose dependent, with 28.6%-50.0% of animals developing ADAs after 36 weeks of treatment. This was characterized as late onset (median onset of 185 days) with low titers (median titer of 8, or 400 if minimum required dilution of 50 is included). The overall incidence rate of patients who developed ADAs was 30% after 65 weeks of treatment with median onset of 203 days and median peak titer of 300. IM had minimal effect on plasma peak (Cmax) and total exposure (i.e. area under curve, AUC) of inotersen, but showed elevated plasma trough levels in both IM-positive animals and humans. However, ADAs had no effect on tissue exposure, TTR messenger RNA, or plasma TTR levels in the long-term monkey study. Similarly, IM showed no effect on plasma TTR levels in clinical studies. Thus, ADAs antibodies were binding antibodies, but not neutralizing antibodies. Finally, no association was observed between IM and toxicity findings (eg, platelet, complement activation, and histopathology findings) in the inotersen 9-month monkey study. In humans, no difference was observed in hematology, including platelets, kidney function tests, or incidence of adverse events between IM-positive and -negative patients. Overall, IM showed no effect on toxicity or safety of inotersen evaluated in both monkeys and humans. ClinicalTrials.gov Identifier: NCT01737398.

TTR gene silencing therapy in post liver transplant hereditary ATTR amyloidosis patients.

OBJECTIVE: Patients with hereditary transthyretin (TTR) amyloidosis (hATTR) often experience disease progression after orthotopic liver transplant (POLT) due in part to wild type ATTR amyloid deposition. The management strategy is not defined. We propose that TTR gene silencing with an antisense oligonucleotide or a small interfering ribonucleic acid may be a treatment for these patients. METHODS: We reviewed the charts of hATTR patients POLT treated with a TTR gene silencing agent at 7 different Amyloid Clinics between 2018-2020. RESULTS: Nine hATTR patients with POLT were treated with TTR gene silencing therapy (Inotersen). The median age was 61 years. The median time from OLT to initiation of TTR gene silencing therapy was 7.5 years. The median duration of therapy was 12 months. Neuropathy impairment score remained stable or improved in all patients. Five patients stopped treatment: 3 because of thrombocytopenia, 2 because of reversible liver rejection. Three patients who discontinued treatment subsequently experienced worsening of their neuropathy. CONCLUSION: TTR gene silencing therapy in hATTR patients with POLT could be a treatment option. Vigilant monitoring of renal, liver and bone marrow functions is necessary because of frequent complications. Further studies are needed to determine efficacy.

Population Pharmacokinetic-Pharmacodynamic Modeling of Inotersen, an Antisense Oligonucleotide for Treatment of Patients with Hereditary Transthyretin Amyloidosis.

A population pharmacokinetic (PK) and pharmacodynamic (PD) model was developed for inotersen to evaluate exposure-response relationships and to optimize therapeutic dosing regimen in patients with hereditary transthyretin (TTR) amyloidosis polyneuropathy (hATTR-PN). Inotersen PK and TTR level (PD) data were composed of one Phase 1 study in healthy subjects, one Phase 2/3 study in hATTR patients, and its one open-label extension study. Effects of intrinsic and extrinsic factors (covariates) on PK and PK/PD of inotersen were evaluated using a full model approach. Inotersen PK was characterized by a two-compartment model with elimination from the central compartment. The population PK analysis identified disease status and lean body mass (LBM) as significant covariates for inotersen PK. Nonetheless, the contribution of disease status and LBM on PK was small, as the difference in clearance (CL/F) was 11.1% between healthy subjects and patients with hATTR-PN and 38% between the lowest and highest LBM quartiles of the patient population. Age, race, sex, baseline renal function estimated glomerular filtration rate, and hepatic function markers (baseline albumin, bilirubin, and alanine aminotransferase values) were not statistically significant covariates affecting inotersen PK. An inhibitory effect indirect-response model (inhibition of TTR production) was used to describe the drug effect on TTR-time profiles, with baseline TTR included as a covariate. The overall population Imax and IC50, together with 95% confidence interval, was estimated to be 0.913 (0.899-0.925) and 9.07 (8.08-10.1) ng/mL, respectively. V30M mutation showed no effect on the estimated IC50 value for hATTR patients. The final population PK and PK/PD model was used to simulate four different treatment regimens. The population PK/PD model developed well described the PK and PD of inotersen in patients with hATTR-PN and has been used for label recommendation and trial simulations.

Population Pharmacokinetic-Pharmacodynamic Model of Serum Transthyretin Following Patisiran Administration.

Hereditary transthyretin-mediated amyloidosis is an inherited, rapidly progressive, life-threatening disease caused by mutated transthyretin (TTR) protein. Patisiran is a small interfering RNA (siRNA) formulated in a lipid nanoparticle that inhibits hepatic TTR protein synthesis by RNA interference. We have developed an indirect-response pharmacokinetic-pharmacodynamic model relating plasma siRNA (ALN-18328) levels to serum TTR reduction across five clinical studies. A sigmoidal function described this relationship, with estimated Hill coefficient of 0.548, and half maximal inhibitory concentration (IC50), IC80, and IC90 values of 9.45, 118.5, and 520.5 ng/mL, respectively. Following patisiran 0.3 mg/kg every 3 weeks (q3w), steady-state plasma ALN-18328 exposures were between IC80 and IC90, yielding average serum TTR reductions of 80%-90% from baseline. Covariate analysis indicated similar TTR reduction across evaluated intrinsic and extrinsic factors, obviating the need for dose adjustment. Modeling results support the recommended patisiran dosing schedule of 0.3 mg/kg q3w, with a maximum dose of 30 mg for patients weighing ≥100 kg.

Undiscovered Roles for Transthyretin: From a Transporter Protein to a New Therapeutic Target for Alzheimer's Disease.

Transthyretin (TTR), an homotetrameric protein mainly synthesized by the liver and the choroid plexus, and secreted into the blood and the cerebrospinal fluid, respectively, has been specially acknowledged for its functions as a transporter protein of thyroxine and retinol (the latter through binding to the retinol-binding protein), in these fluids. Still, this protein has managed to stay in the spotlight as it has been assigned new and varied functions. In this review, we cover knowledge on novel TTR functions and the cellular pathways involved, spanning from neuroprotection to vascular events, while emphasizing its involvement in Alzheimer's disease (AD). We describe details of TTR as an amyloid binding protein and discuss its interaction with the amyloid Aß peptides, and the proposed mechanisms underlying TTR neuroprotection in AD. We also present the importance of translating advances in the knowledge of the TTR neuroprotective role into drug discovery strategies focused on TTR as a new target in AD therapeutics.

Patisiran Pharmacokinetics, Pharmacodynamics, and Exposure-Response Analyses in the Phase 3 APOLLO Trial in Patients With Hereditary Transthyretin-Mediated (hATTR) Amyloidosis.

Hereditary transthyretin-mediated (hATTR) amyloidosis is an inherited, rapidly progressive, life-threatening disease caused by deposition of abnormal transthyretin protein. Patisiran is an RNA interference therapeutic comprising a novel, small interfering ribonucleic acid (ALN-18328) formulated in a lipid nanoparticle targeted to inhibit hepatic transthyretin protein synthesis. The lipid nanoparticle also contains 2 novel lipid excipients (DLin-MC3-DMA and PEG2000 -C-DMG). Here we report patisiran pharmacokinetics (PK), pharmacodynamics (PD), and exposure-response analyses from the phase 3 APOLLO trial, in which patients with hATTR amyloidosis with polyneuropathy were randomized 2:1 to receive patisiran 0.3 mg/kg or placebo intravenously every 3 weeks over 18 months. In patisiran-treated patients, mean maximum reduction in serum transthyretin level from baseline was 87.8%. Patisiran PK exposure was stable following chronic dosing. There were no meaningful differences in PK exposure, serum transthyretin reduction, and efficacy (change from baseline in modified Neuropathy Impairment Score+7) across all subgroups analyzed (age, sex, race, body weight, genotype status of valine-to-methionine mutation at position 30 [V30M] and non-V30M, prior use of tetramer stabilizers, mild/moderate renal impairment, and mild hepatic impairment). transthyretin reduction and efficacy were similar across the interpatient PK exposure range for ALN-18328. There was no trend in the incidence of adverse events or serious adverse events across the interpatient PK exposure range for all 3 analytes. Incidence of antidrug antibodies was low (3.4%) and transient, with no impact on PK, PD, efficacy, or safety. The patisiran dosing regimen of 0.3 mg/kg every 3 weeks is appropriate for all patients with hATTR amyloidosis.

Comparative Serum Proteomic Analysis of the Effects of Sodium Selenate on a Mouse Model of Alzheimer's Disease.

Selenium (Se), as a nutritionally essential trace element, has been shown to decrease with age and is closely related to Alzheimer's disease (AD). To probe the effects of Se on AD pathology, two-dimensional fluorescence difference gel electrophoresis was applied to the serum samples collected from the wild-type (WT) mice and the triple transgenic (PS1M146V/AßPPSwe/TauP301L) AD mice (3xTg-AD), treated with or without sodium selenate in drinking water for 4 months beginning at 2 months of age. Proteomics results revealed 17 differentially expressed proteins between WT and 3xTg-AD mice. It was found that the administration of selenate reversed the alterations of the differentially expressed serum proteins by up-regulating 13 proteins and down-regulating 2 proteins which were reported to be involved in the key pathogenesis of AD, including regulation of Aß production, lipid metabolism regulation, and anti-inflammation. These results suggested that a dietary supplement with selenate is effective for prevention and treatment of AD, and the mechanism was maybe related to its role in Aß regulation, lipid metabolism, and anti-inflammation. Moreover, we also presented that α-2 macroglobulin, transthyretin, haptoglobin, alpha-2-HS-glycoprotein, and alpha-1-antitrypsin in the serum can be used to evaluate the effect of selenate on AD pathology.

A pair of peptides inhibits seeding of the hormone transporter transthyretin into amyloid fibrils.

The tetrameric protein transthyretin is a transporter of retinol and thyroxine in blood, cerebrospinal fluid, and the eye, and is secreted by the liver, choroid plexus, and retinal epithelium, respectively. Systemic amyloid deposition of aggregated transthyretin causes hereditary and sporadic amyloidoses. A common treatment of patients with hereditary transthyretin amyloidosis is liver transplantation. However, this procedure, which replaces the patient's variant transthyretin with the WT protein, can fail to stop subsequent cardiac deposition, ultimately requiring heart transplantation. We recently showed that preformed amyloid fibrils present in the heart at the time of surgery can template or seed further amyloid aggregation of native transthyretin. Here we assess possible interventions to halt this seeding, using biochemical and EM assays. We found that chemical or mutational stabilization of the transthyretin tetramer does not hinder amyloid seeding. In contrast, binding of the peptide inhibitor TabFH2 to ex vivo fibrils efficiently inhibits amyloid seeding by impeding self-association of the amyloid-driving strands F and H in a tissue-independent manner. Our findings point to inhibition of amyloid seeding by peptide inhibitors as a potential therapeutic approach.