Revealing a Mutant-Induced Receptor Allosteric Mechanism for the Thyroid Hormone Resistance

Roxadustat has risks of reversible central hypothyroidism in patients undergoing hemodialysis: a single-center retrospective cohort study

Roxadustat, a hypoxia-inducible factor-prolyl hydroxylase inhibitor, has proven efficacy in the treatment of renal anemia; however, evidence indicates that it may cause central hypothyroidism. The prevalence and reversibility of roxadustat-induced central hypothyroidism in patients undergoing hemodialysis remain unclear. Here, we retrospectively analyzed thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels in 51 patients (mean age: 72.3 ± 10.7 years; 58.8% male) undergoing hemodialysis before, during, and after halting roxadustat treatment. TSH levels were significantly decreased from a median of 2.46 (interquartile range:1.60-4.51) mU/L before roxadustat treatment to 1.36 (0.72-2.41) mU/L during treatment (p < 0.001), and improved to 2.56 (1.78-4.63) mU/L after halting roxadustat (p < 0.001). Similarly, FT4 levels decreased from 1.11 (0.97-1.24) ng/dL before roxadustat treatment to 0.92 (0.71-1.03) ng/dL during treatment (p < 0.001) and improved to 1.05 (0.93-1.17) ng/dL after halting roxadustat (p < 0.001). FT3 levels were 2.04 (1.78-2.31) pg/mL before starting roxadustat, 1.97 (1.69-2.27) pg/mL during treatment, and 1.90 (1.63-2.18) pg/mL after halting roxadustat, with no significant difference between each group. Moreover, 2.0% of patients exhibited extremely low TSH levels (≤0.1 mU/L) and low TSH levels (>0.1 mU/L to <0.4 mU/L) before starting roxadustat and that percentage increased to 5.9% and 7.8%, respectively, during treatment. After roxadustat cessation, extremely low or low TSH levels recovered in all patients. Taken together, the results indicate that roxadustat can cause reversible central hypothyroidism in patients undergoing hemodialysis.

A Case of Thyroid Hormone Resistance Syndrome with a Novel Mutation (c.947G>a) in the THRB Gene: Experience in Diagnosis and Treatment

Background

Thyroid hormone resistance syndrome (RTH) is a rare hereditary endocrine disease that can manifest as hyperthyroidism, hypothyroidism, or remain asymptomatic. It can easily be confused with other types of thyroid diseases. The diagnosis of the disease depends on genetic testing.

Case Report

We report a 19-year-old male patient with elevation of thyroid hormones. Serological examination showed elevated thyroid hormone levels, and thyroid-stimulating hormone levels within the reference interval. The patient was finally diagnosed with RTH after genetic testing that identified a gene mutation inherited from his mother. Due to timely diagnosis, the patient's condition has been well controlled, and his prognosis is good.

Conclusion

The clinical manifestations of RTH lack specificity, and serological examination typically shows elevated thyroid hormone levels and unsuppressed thyrotropin levels. Differential diagnosis requires a combination of serological examination, imaging studies, and functional tests to distinguish RTH from other conditions. The purpose of this treatment is to improve symptoms and should not involve the blind administration of antithyroid drugs, thyroid surgery, or radiotherapy.

Automated design of multi-target ligands by generative deep learning

Generative deep learning models enable data-driven de novo design of molecules with tailored features. Chemical language models (CLM) trained on string representations of molecules such as SMILES have been successfully employed to design new chemical entities with experimentally confirmed activity on intended targets. Here, we probe the application of CLM to generate multi-target ligands for designed polypharmacology. We capitalize on the ability of CLM to learn from small fine-tuning sets of molecules and successfully bias the model towards designing drug-like molecules with similarity to known ligands of target pairs of interest. Designs obtained from CLM after pooled fine-tuning are predicted active on both proteins of interest and comprise pharmacophore elements of ligands for both targets in one molecule. Synthesis and testing of twelve computationally favored CLM designs for six target pairs reveals modulation of at least one intended protein by all selected designs with up to double-digit nanomolar potency and confirms seven compounds as designed dual ligands. These results corroborate CLM for multi-target de novo design as source of innovation in drug discovery.

Low cholesterol levels are good markers for central hypothyroidism in case with dialysis using roxadustat

Recently, hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitors have been used for renal anemia, but side effects have also been reported. We report on the association of central hypothyroidism and cholesterol with roxadustat. Based on this case and previous reports, we believe that patients receiving roxadustat should have their thyroid function and cholesterol levels checked regularly.

Effects of roxadustat on thyroid hormone levels and blood lipid metabolism in patients undergoing hemodialysis: a retrospective study

Background: Roxadustat is commonly used to treat renal anemia. However, the potential effects of roxadustat on metabolism and organs other than the kidneys have recently attracted increased attention. Objective: This study aimed to examine the regulatory effects of roxadustat on thyroid hormones and blood lipid metabolism in patients with end-stage kidney disease (ESKD) undergoing hemodialysis. Methods: Eighty ESKD patients on hemodialysis and taking roxadustat were enrolled. Hemoglobin, thyroid hormones (TSH, FT3, FT4), and blood lipid profiles (TC, LDL-C, TG, HDL-C) were assessed before and after treatment. Changes in these parameters were compared, and relevant causative factors were analyzed. Results: Roxadustat significantly increased Hb, lowered TSH, FT4, TC, and LDL-C levels (all P<0.001). Patients were categorized into three groups based on post-treatment TSH inhibition percentage: Q1(≥70%), Q2(30%-70%), Q3(≤30%). Pre-treatment TSH decreased with reduced TSH inhibition (P<0.05). Post-treatment, TC, LDL-C, TSH, FT3, and FT4 increased with reduced TSH inhibition (all P<0.05).TC and LDL-C significantly decreased post-treatment in Q1 and Q2 (P<0.05). Correlation analysis showed a positive correlation between ΔTSH and pre-treatment TSH levels (r=0.732, P<0.001). The proportion of patients with ≥70% TSH inhibition increased with higher pre-treatment TSH levels (P for trend <0.05). ΔLDL-C and ΔTSH were positively correlated (r=0.278, P<0.05), with ΔTSH identified as an influencing factor in multiple linear regression (β=0.133, 95% CI [0.042, 0.223], P<0.05). Conclusion: Roxadustat effectively improves anemia in ESKD patients while inhibiting TSH and FT4 secretion and reducing TC and LDL-C levels. Decreases in TSH levels correlate with baseline TSH levels, and lowered blood lipid levels are associated with decreased TSH levels.

Cerebral Infarction After Switching From Roxadustat to Daprodustat in a Patient With Renal Anemia

Renal anemia is generally caused by a decrease in the production of erythropoietin in kidney due to renal dysfunction, and this may be associated with the increase in mortality and cardiovascular events in addition to subjective symptoms such as fatigue and wobbliness. We report a case of an 87-year-old man with type 2 diabetes, hypertension, and dyslipidemia who had received roxadustat (a hypoxia-inducible factor (HIF) prolyl hydroxylase (PH) inhibitor) for renal anemia due to diabetic nephropathy and in whom roxadustat was switched to daprodustat (another HIF-PH inhibitor) due to the onset of central hypothyroidism. About three weeks after this change, the patient developed acute asymptomatic cerebral infarction with an elevation of hemoglobin (Hb). It is unclear if the change to daprodustat was involved in the onset of cerebral infarction. However, this case suggests that particular caution should be paid to unexpected acute elevation of Hb after a change from one HIF-PH inhibitor to another, especially in a patient at high risk for cardiovascular events.

Association between roxadustat use and suppression of thyroid function: a systematic review and meta-analysis

BACKGROUND

Based on several case reports and observational studies, there is a growing concern regarding the potential association between roxadustat, a hypoxia-inducible factor prolyl-hydroxylase inhibitor, and suppression of thyroid function. In this systematic review and meta-analysis (PROSPERO: CRD42023471516), we aimed to evaluate the relationship between roxadustat use and suppression of thyroid function.

METHODS

We conducted a comprehensive search of MEDLINE via PubMed, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials databases using the search term "roxadustat" to identify all relevant studies. The study population comprised adults with renal anemia who participated in a randomized controlled trial or observational study, with roxadustat as the intervention and a placebo or erythropoiesis-stimulating agent (ESA) as the comparator. The primary outcome was suppression of thyroid function and the secondary outcome was hypothyroidism. A meta-analysis was conducted using the DerSimonian-Laird random effects model based on the size of the intention-to-treat population, and the odds ratio (OR) and 95% confidence interval (CI) were calculated. Two reviewers independently screened the articles, extracted data, and assessed studies using the ROBINS-I tool.

RESULTS

Of the six studies eligible for inclusion, a meta-analysis was performed using data from two observational studies comparing roxadustat and ESA. The meta-analysis showed that the incidence of suppression of thyroid function was significantly higher with roxadustat use than with ESA use (OR: 6.45; 95% CI: 3.39-12.27; I2 = 12%). Compared with ESA, roxadustat seemed to potentially increase the risk for suppression of thyroid function in patients with renal anemia.

CONCLUSIONS

Our findings highlighted the importance of monitoring thyroid function in patients treated with roxadustat. The results of this review may enhance the safety of using roxadustat to treat renal anemia through advance recognition of the risk for suppression of thyroid function.

Roxadustat-Induced Central Hypothyroidism in Renal Anemia Patients: Insights From Antineutrophil Cytoplasmic Antibody-Related Vasculitis Cases

The introduction of hypoxia-inducible factor-prolyl hydroxylase (HIF-PH) inhibitors in Japan in 2019 for treating renal anemia in hemodialysis patients has resulted in an adverse event: central hypothyroidism. Although this adverse event was not widely recognized by the public, it was first documented in Japan in 2021. Despite limited case reports on roxadustat, an oral HIF-PH inhibitor that induces central hypothyroidism, this condition typically improves rapidly upon discontinuation of the drug. In this report, we present rare cases of roxadustat-induced central hypothyroidism in two patients: a woman in her 80s and a man in his 60s, neither of whom had prior thyroid disease. Both patients developed central hypothyroidism shortly after starting roxadustat treatment for renal anemia associated with antineutrophil cytoplasmic antibody-related vasculitis. Notably, neither patient had pituitary tumors or other pituitary hormone disorders. Thyroid function improved with levothyroxine treatment, even when oral roxadustat was continued. Roxadustat may induce central hypothyroidism, highlighting the importance of regularly measuring and evaluating thyroid function when administering this drug to monitor possible changes in thyroid hormone levels.

Thyroid receptor β: A promising target for developing novel anti-androgenetic alopecia drugs

Androgenetic alopecia (AGA) significantly impacts the self-confidence and mental well-being of people. Recent research has revealed that thyroid receptor β (TRβ) agonists can activate hair follicles and effectively stimulate hair growth. This review aims to comprehensively elucidate the specific mechanism of action of TRβ in treating AGA from various perspectives, highlighting its potential as a drug target for combating AGA. Moreover, this review provides a thorough summary of the research advances in TRβ agonist candidates with anti-AGA efficacy and outlines the structure-activity relationships (SARs) of TRβ agonists. We hope that this review will provide practical information for the development of effective anti-alopecia drugs.

Truncated variants of thyroid hormone receptor beta display disease-inflicting malfunctioning at cellular level

Thyroid hormone receptor β (THRβ) is a member of the nuclear receptor superfamily of ligand-modulated transcription factors. Upon ligand binding, THRβ sequentially recruits the components of transcriptional machinery to modulate target gene expression. In addition to regulating diverse physiological processes, THRβ plays a crucial role in hypothalamus-pituitary-thyroid axis feedback regulation. Anomalies in THRβ gene/protein structure are associated with onset of diverse disease states. In this study, we investigated disease-inflicting truncated variants of THRβ using in-silico analysis and cell-based assays. We examined the THRβ truncated variants on multiple test parameters, including subcellular localization, ligand-receptor interactions, transcriptional functions, interaction with heterodimeric partner RXR, and receptor-chromatin interactions. Moreover, molecular dynamic simulation approaches predicted that shortened THRβ-LBD due to point mutations contributes proportionally to the loss of structural integrity and receptor stability. Deviant subcellular localization and compromised transcriptional function were apparent with these truncated variants. Present study shows that 'mitotic bookmarking' property of some THRβ variants is also affected. The study highlights that structural and conformational attributes of THRβ are necessary for normal receptor functioning, and any deviations may contribute to the underlying cause of the inflicted diseases. We anticipate that insights derived herein may contribute to improved mechanistic understanding to assess disease predisposition.

Hypoxia-inducible Factor Prolyl Hydroxylase Inhibitors and Hypothyroidism: An Analysis of the Japanese Pharmacovigilance Database

BACKGROUND/AIM

Hypothyroidism induced by roxadustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, was recently reported; however, information regarding roxadustat-associated hypothyroidism is still lacking. We explored the risk and time to onset of hypothyroidism associated with HIF-PH inhibitors using the Japanese Adverse Drug Event Report (JADER), a pharmacovigilance database.

PATIENTS AND METHODS

The participants of this study were registered in the JADER database between April 2004 and March 2023. The association between HIF-PH inhibitors and hypothyroidism was evaluated using the reporting odds ratio (ROR) and information component (IC). We also calculated the period from the start of drug administration to the onset of hypothyroidism and determined the onset pattern using Weibull distribution.

RESULTS

Roxadustat had positive signals for hypothyroidism among the HIF-PH inhibitors based on the ROR [31.03, 95% confidence interval (CI)=27.81-34.62] and IC (4.51, 95%CI=4.36-4.67) values, and a strong relationship was confirmed. In addition, the median time to roxadustat-associated hypothyroidism onset was 92 days, and over 50% of cases occurred within 100 days of starting treatment. Furthermore, the onset pattern was an early failure type.

CONCLUSION

There is a possible association between roxadustat and hypothyroidism. Therefore, enhanced thyroid function testing within 100 days of treatment initiation may help detect roxadustat-associated hypothyroidism. However, further research is required to confirm these findings, considering study limitations using databases of spontaneous adverse event reports.

Effect of Roxadustat on Thyroid Function in Patients With Renal Anemia

CONTEXT

Roxadustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, a recently developed class of drugs for treatment of anemia in chronic kidney disease (CKD), is reported to have a structure unlike that of other HIF-PH inhibitors but similar to that of triiodothyronine and bind to the thyroid hormone receptor in vitro. However, reports on the effects of roxadustat on thyroid function are limited and not detailed, and it remains unknown whether other HIF-PH inhibitors also affect thyroid function.

OBJECTIVE

To compare the effect of roxadustat with daprodustat, another HIF-PH inhibitor, on thyroid function in patients with renal anemia in CKD.

METHODS

This retrospective observational study included a total of 26 patients with anemia in CKD who were treated with roxadustat or daprodustat; thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured before and after treatment with the drugs.

RESULTS

After initiation of roxadustat, TSH showed a significant decrease (2.4732 [1.7858-4.9016] μIU/mL before treatment and 0.659 [0.112-2.005] μIU/mL after treatment, P < .05); FT4 showed a significant decrease (0.93 [0.84-1.05] ng/dL before treatment and 0.70 [0.53-0.85] ng/dL after treatment, P < .01). After daprodustat initiation, neither TSH nor FT4 showed a significant change (TSH: 3.044 [1.853-4.171] μIU/mL before treatment and 2.893 [1.866-4.894] μIU/mL after treatment, P = .635; FT4 was 0.93 [0.81-1.00] ng/dL before treatment and 0.97 [0.87-1.05] ng/dL after treatment, P = .328).

CONCLUSION

Roxadustat decreases TSH and FT4 levels while daprodustat does not.

Thyroid function analysis after roxadustat or erythropoietin treatment in patients with renal anemia: a cohort study

PURPOSE

This cohort study was designed to explore whether roxadustat or erythropoietin could affect thyroid function in patients with renal anemia.

METHODS

The study involved 110 patients with renal anemia. Thyroid profile and baseline investigations were carried out for each patient. The patients were divided into two groups: 60 patients taking erythropoietin served as the control group (rHuEPO group) and 50 patients using roxadustat served as the experimental group (roxadustat group).

RESULTS

The results indicated that there were no significant differences in serum total thyroxine (TT4), total triiodothyronine (TT3), free triiodothyronine (FT3), free thyroxine (FT4) or thyroid stimulating hormone (TSH) between the two groups at baseline. After treatment, TSH, FT3, and FT4 were significantly lower in the roxadustat group than in the rHuEPO group (p < 0.05). After adjusting for age, sex, dialysis modality, thyroid nodules and causes of kidney disease, Cox regression showed that roxadustat was an independent influencing factor on thyroid dysfunction (HR 3.37; 95% CI 1.94-5.87; p < 0.001). After 12 months of follow-up, the incidence of thyroid dysfunction was higher in the roxadustat group than in the rHuEPO group (log-rank p < 0.001).

CONCLUSION

Roxadustat may lead to a higher risk of thyroid dysfunction, including low TSH, FT3 and FT4, than rHuEPO in patients with renal anemia.

Hypoxia-induced signaling in the cardiovascular system: pathogenesis and therapeutic targets

Hypoxia, characterized by reduced oxygen concentration, is a significant stressor that affects the survival of aerobic species and plays a prominent role in cardiovascular diseases. From the research history and milestone events related to hypoxia in cardiovascular development and diseases, The "hypoxia-inducible factors (HIFs) switch" can be observed from both temporal and spatial perspectives, encompassing the occurrence and progression of hypoxia (gradual decline in oxygen concentration), the acute and chronic manifestations of hypoxia, and the geographical characteristics of hypoxia (natural selection at high altitudes). Furthermore, hypoxia signaling pathways are associated with natural rhythms, such as diurnal and hibernation processes. In addition to innate factors and natural selection, it has been found that epigenetics, as a postnatal factor, profoundly influences the hypoxic response and progression within the cardiovascular system. Within this intricate process, interactions between different tissues and organs within the cardiovascular system and other systems in the context of hypoxia signaling pathways have been established. Thus, it is the time to summarize and to construct a multi-level regulatory framework of hypoxia signaling and mechanisms in cardiovascular diseases for developing more therapeutic targets and make reasonable advancements in clinical research, including FDA-approved drugs and ongoing clinical trials, to guide future clinical practice in the field of hypoxia signaling in cardiovascular diseases.

Disproportionality Analysis on Hypothyroidism With Roxadustat Using the Japanese Adverse Drug Event Database

Hypoxia-inducible factor prolyl-hydroxylase inhibitor (HIF-PHI) is a novel agent for the treatment of renal anemia. HIF-PHI increases endogenous erythropoietin production by inhibiting the degradation of an erythropoietin transcription factor. Although beneficial effects are expected from HIF-PHI, its novel mechanism raises concerns regarding the risk of potential adverse events. The cases of hypothyroidism, which had not been reported in clinical trials, were reported after the administration of roxadustat in a real-world setting. However, the effects of HIF-PHIs on thyroid function have not yet been fully evaluated. This study aimed to assess the clinical impact of HIF-PHIs on thyroid function using the Japanese Adverse Drug Event Report database, a spontaneous reporting system in Japan, because HIF-PHIs were made available in Japan before they were available in other countries. Although a disproportionality signal for hypothyroidism was detected with roxadustat (reporting odds ratio [ROR]:22.1, 95% confidence interval [CI]:18.3-26.7, no signals were detected with another HIF-PHI, daprodustat (ROR:1.3, 95%CI:0.3-5.4), and epoetin beta pegol (ROR:1.2, 95%CI:0.5-2.7). Signals of hypothyroidism due to roxadustat were also detected regardless of age or sex. Approximately 50% of hypothyroidism cases were reported within 50 days of starting roxadustat use. These results indicate that roxadustat use may be related to the development of hypothyroidism. The need for monitoring of thyroid function should be alerted during roxadustat administration regardless of age or sex.

Evolving Strategies in the Treatment of Anaemia in Chronic Kidney Disease: The HIF-Prolyl Hydroxylase Inhibitors

Chronic kidney disease (CKD) affects approximately 10% of the worldwide population; anaemia is a frequent complication. Inadequate erythropoietin production and absolute or functional iron deficiency are the major causes. Accordingly, the current treatment is based on iron and erythropoiesis stimulating agents (ESAs). Available therapy has dramatically improved the management of anaemia and the quality of life. However, safety concerns were raised over ESA use, especially when aiming to reach near-to-normal haemoglobin levels with high doses. Moreover, many patients show hypo-responsiveness to ESA. Hypoxia-inducible factor (HIF) prolyl hydroxylase domain (PHD) inhibitors (HIF-PHIs) were developed for the oral treatment of anaemia in CKD to overcome these concerns. They simulate the body's exposure to moderate hypoxia, stimulating the production of endogenous erythropoietin. Some molecules are already approved for clinical use in some countries. Data from clinical trials showed non-inferiority in anaemia correction compared to ESA or superiority for placebo. Hypoxia-inducible factor-prolyl hydroxylase domain inhibitors may also have additional advantages in inflamed patients, improving iron utilisation and mobilisation and decreasing LDL-cholesterol. Overall, non-inferiority was also shown in major cardiovascular events, except for one molecule in the non-dialysis population. This was an unexpected finding, considering the lower erythropoietin levels reached using these drugs due to their peculiar mechanism of action. More data and longer follow-ups are necessary to better clarifying safety issues and further investigate the variety of pathways activated by HIF, which could have either positive or negative effects and could differentiate HIF-PHIs from ESAs.

Hypoxia-Inducible Factor-Prolyl Hydroxyl Domain Inhibitors: From Theoretical Superiority to Clinical Noninferiority Compared with Current ESAs?

Anemia is a common complication of chronic kidney disease; it is mainly treated with erythropoiesis-stimulating agents (ESAs) and iron. Experimental studies extensively investigated the mechanisms involved in the body's response to hypoxia and led to the discovery of the hypoxia-inducible factor (HIF) pathway and the enzymes regulating its function. HIF-prolyl-hydroxyl domain (PHD) inhibitors are a new class of oral drugs developed to treat anemia in chronic kidney disease. By inhibiting the function of PHD enzymes, they mimic the exposure to moderate hypoxia and stimulate the production of endogenous erythropoietin and very likely increase iron availability. Some data also suggest that their efficacy and, consequently, dose needs are less influenced by inflammation than ESAs. Overall, data from phases 2 and 3 clinical development showed efficacy in anemia correction and maintenance for all of the class molecules compared with placebo (superiority) or erythropoiesis-stimulating agents (noninferiority). Three molecules, roxadustat, vadadustat, and daprodustat, underwent extensive clinical investigation to assess their safety on hard cardiovascular end points, mortality, and special interest events (including cancer and thrombosis). Aside from vadadustat in the nondialysis population, at the prespecified primary analyses, all three molecules met the noninferiority margin for the risk of major cardiovascular events compared with erythropoiesis-stimulating agents or placebo. The reason for this discrepancy is difficult to explain. Other safety signals came from secondary analyses of some of the other randomized clinical trials, including a higher incidence of thrombosis. A more extensive clinical experience with post-marketing data on hard safety issues is needed to define better when and how to use HIF-PHD inhibitors compared with already available ESAs.

Thyroid hormone resistance: Mechanisms and therapeutic development

As an essential primary hormone, thyroid hormone (TH) is indispensable for human growth, development and metabolism. Impairment of TH function in several aspects, including TH synthesis, activation, transportation and receptor-dependent transactivation, can eventually lead to thyroid hormone resistance syndrome (RTH). RTH is a rare syndrome that manifests as a reduced target cell response to TH signaling. The majority of RTH cases are related to thyroid hormone receptor β (TRβ) mutations, and only a few RTH cases are associated with thyroid hormone receptor α (TRα) mutations or other causes. Patients with RTH suffer from goiter, mental retardation, short stature and bradycardia or tachycardia. To date, approximately 170 mutated TRβ variants and more than 20 mutated TRα variants at the amino acid level have been reported in RTH patients. In addition to these mutated proteins, some TR isoforms can also reduce TH function by competing with primary TRs for TRE and RXR binding. Fortunately, different treatments for RTH have been explored with structure-activity relationship (SAR) studies and drug design, and among these treatments. With thyromimetic potency but biochemical properties that differ from those of primary TH (T3 and T4), these TH analogs can bypass specific defective transporters or reactive mutant TRs. However, these compounds must be carefully applied to avoid over activating TRα, which is associated with more severe heart impairment. The structural mechanisms of mutation-induced RTH in the TR ligand-binding domain are summarized in this review. Furthermore, strategies to overcome this resistance for therapeutic development are also discussed.

Discovery of a Highly Selective and H435R-Sensitive Thyroid Hormone Receptor β Agonist

The design and development of agonists selectively targeting thyroid hormone receptor β (TRβ) and TRβ mutants remain challenging tasks. In this study, we first adopted the strategy of breaking the "His-Phe switch" to solve two problems, simultaneously. A structure-based design approach was successfully utilized to obtain compound 16g, which is a potent TRβ agonist (EC₅₀: 21.0 nM, 85.0% of the maximum efficacy of 1) with outstanding selectivity for TRβ over TRα and also effectively activates the TRβ^H435R mutant. Then, we developed a highly efficient synthetic method for 16g. Our serials of cocrystal structures revealed detailed structural mechanisms in overcoming subtype selectivity and rescuing the H435R mutation. 16g also showed excellent lipid metabolism, safety, metabolic stability, and pharmacokinetic properties. Collectively, 16g is a well-characterized selective and mutation-sensitive TRβ agonist for further investigating its function in treating dyslipidemia, nonalcoholic steatohepatitis (NASH), and resistance to thyroid hormone (RTH).

Structural overview and perspectives of the nuclear receptors, a major family as the direct targets for small-molecule drugs

The nuclear receptors (NRs) are an evolutionarily related family of transcription factors, which share certain common structural characteristics and regulate the expressions of various genes by recognizing different response elements. NRs play important roles in cell differentiation, proliferation, survival and apoptosis, rendering them indispensable in many physiological activities including growth and metabolism. As a result, dysfunctions of NRs are closely related to a variety of diseases, such as diabetes, obesity, infertility, inflammation, the Alzheimer's disease, cardiovascular diseases, prostate and breast cancers. Meanwhile, small-molecule drugs directly targeting NRs have been widely used in the treatment of above diseases. Here we summarize recent progress in the structural biology studies of NR family proteins. Compared with the dozens of structures of isolated DNA-binding domains (DBDs) and the striking more than a thousand of structures of isolated ligand-binding domains (LBDs) accumulated in the Protein Data Bank (PDB) over thirty years, by now there are only a small number of multi-domain NR complex structures, which reveal the integration of different NR domains capable of the allosteric signal transduction, or the detailed interactions between NR and various coregulator proteins. On the other hand, the structural information about several orphan NRs is still totally unavailable, hindering the further understanding of their functions. The fast development of new technologies in structural biology will certainly help us gain more comprehensive information of NR structures, inspiring the discovery of novel NR-targeting drugs with a new binding site beyond the classic LBD pockets and/or a new mechanism of action.

Resistance to Thyroid Hormone Beta: A Focused Review

Resistance to thyroid hormone (RTH) is a clinical syndrome defined by impaired sensitivity to thyroid hormone (TH) and its more common form is caused by mutations in the thyroid hormone receptor beta (THRB) gene, termed RTHβ. The characteristic biochemical profile is that of elevated serum TH levels in absence of thyrotropin suppression. Although most individuals are considered clinically euthyroid, there is variability in phenotypic manifestation among individuals harboring different THRB mutations and among tissue types in the same individual due in part to differential expression of the mutant TRβ protein. As a result, management is tailored to the specific symptoms of TH excess or deprivation encountered in the affected individual as currently there is no available therapy to fully correct the TRβ defect. This focused review aims to provide a concise update on RTHβ, discuss less well recognized associations with other thyroid disorders, such as thyroid dysgenesis and autoimmune thyroid disease, and summarize existing evidence and controversies regarding the phenotypic variability of the syndrome. Review of management addresses goiter, attention deficit disorder and "foggy brain". Lastly, this work covers emerging areas of interest, such as the relevance of variants of unknown significance and novel data on the epigenetic effect resulting from intrauterine exposure to high TH levels and its transgenerational inheritance.

Suppression of thyrotropin secretion during roxadustat treatment for renal anemia in a patient undergoing hemodialysis

Background

Inhibition of hypoxia-inducible factor prolyl hydroxylase (HIF-PH) is a novel choice for the treatment of renal anemia, and an oral HIF-PH inhibitor roxadustat was approved for renal anemia. Roxadustat has high affinity to thyroid hormone receptor beta, which may affect thyroid hormone homeostasis.

Case presentation

We present here a patient undergoing hemodialysis with primary hypothyroidism receiving levothyroxine replacement, who showed decreased free thyroxine (FT4) and thyroid stimulating hormone (TSH) after starting roxadustat. Pituitary stimulation test revealed selective suppression of TSH secretion. Recovery of TSH and FT4 levels after stopping roxadustat suggested the suppression of TSH was reversible.

Conclusions

Physicians should pay special attention to thyroid hormone abnormalities in treatment with roxadustat.

Roxadustat and thyroid-stimulating hormone suppression

Hypoxia-inducible factor prolyl-hydroxylase inhibitors belong to a new class of orally administered drugs for treating anemia in patients with chronic kidney disease (CKD). The prevalence of hypothyroidism is disproportionately high in patients with CKD on hemodialysis. We report a rapid suppression of thyroid-stimulating hormone (TSH) and decrease in free triiodothyronine (T3) and free tetraiodothyronine levels after switching from darbepoetin alfa to roxadustat in a hemodialysis patient with hypothyroidism on levothyroxine therapy. This was reversed after stopping roxadustat. Roxadustat has structural similarity with T3 and is a selective activating ligand for thyroid hormone receptor-β possibly suppressing TSH release.

Structural Insights into the Specificity of Ligand Binding and Coactivator Assembly by Estrogen-Related Receptor β

Estrogen-related receptor β (ERRβ) is a nuclear receptor critical for many biological processes. Despite the biological and pharmaceutical importance of ERRβ, deciphering the structure of ERRβ has been hampered by the difficulties in obtaining a pure and stable protein for structural studies. In fact, the ERRβ ligand-binding domain remains the last unsolved ERR structure and also one of only a few unknown nuclear receptor structures. Here, we report the identification of a critical single-residue mutation resulted in robust solubility and stability of an active ERRβ ligand-binding domain, thereby providing a protein tool enabling the first probe into the biochemical and structural studies of this important receptor. The crystal structure reveals key structural features that have enabled the integration of the molecular determinants of signals transduced across the ligand binding and coregulator recruitment by all three ERR subtypes, which also provides a framework for the rational design of selective and potent ligands for the treatment of various ERR-mediated diseases.