Bidirectional TSH and IGF-1 receptor cross talk mediates stimulation of hyaluronan secretion by Graves' disease immunoglobins

Potential role of IGF-1R in the interaction between orbital fibroblasts and B lymphocytes: an implication for B lymphocyte depletion in the active inflammatory phase of thyroid-associated ophthalmopathy

BACKGROUND

Thyroid eye disease (TED) is an inflammatory process involving lymphocyte-mediated immune response and orbital tissue damage. The anti-insulin-like growth factor-1 receptor (IGF-1R) antibodies produced by B lymphocytes are involved in the activation of orbital fibroblasts and the inflammatory process of orbital tissue damage in TED. The purpose of this study was to explore the role of IGF-1R in the mechanistic connection between orbital fibroblasts and B lymphocytes in TED.

METHODS

Orbital fibroblasts sampled from orbital connective tissues and peripheral B lymphocytes isolated from peripheral blood, which were obtained from 15 patients with TED and 15 control patients, were co-cultured at a ratio of 1:20. The level of IGF-1R expression in orbital fibroblasts was evaluated by flow cytometry and confocal microscopy. Transient B lymphocyte depletion was induced with anti-CD20 monoclonal antibody rituximab, while the IGF-1R pathway was blocked by the IGF-1R binding protein. The expression levels of interleukin-6 (IL-6) and regulated upon activation, normal T cell expressed and secreted (RANTES) in the co-culture model were quantified via ELISA.

RESULTS

IGF-1R expression was significantly elevated in TED orbital fibroblasts compared to that of controls. A 24-h co-culture of orbital fibroblasts with peripheral B lymphocytes induced elevated expression levels of IL-6 and RANTES in each group (TED patients and controls), with the highest levels occurring in TED patients (T + T group). Rituximab and IGF-1R binding protein significantly inhibited increased levels of IL-6 and RANTES in the co-culture model of TED patients.

CONCLUSIONS

IGF-1R may mediate interaction between orbital fibroblasts and peripheral B lymphocytes; thus, blocking IGF-1R may reduce the local inflammatory response in TED. Rituximab-mediated B lymphocyte depletion played a role in inhibiting inflammatory responses in this in vitro co-culture model, providing a theoretical basis for the clinical application of anti-CD20 monoclonal antibodies in TED.

Teprotumumab in thyroid eye disease

Thyroid eye disease (TED) is an inflammatory condition involving the periocular and orbital soft tissues, affecting most commonly patients with hyperthyroid disorders. Traditional treatments used for the active phase of the disease range from conservative lubrication for mild symptoms to systemic immunomodulating drugs for moderate-to-severe symptoms. Teprotumumab (Tepezza) is a monoclonal antibody with an inhibitory effect on insulin-like growth factor 1 and is the first Food and Drug Administration (FDA) approved targeted medical therapy for reducing the inflammatory signs and symptoms associated with TED. Two large multicenter, randomized, double-masked, placebo-controlled trials have confirmed the efficacy and safety of teprotumumab in patients with active, moderate-to-severe TED. Recent reports and publications have also demonstrated the efficacy of teprotumumab in a wider range of patients. In this review, we summarize the clinical features and pathophysiology of TED, disease course, and traditional management methods. We further detail the development of teprotumumab, the founding studies that brought it to its FDA approval, adverse events profile, and ongoing as well as future investigations.

Potential involvement of the bone marrow in experimental Graves' disease and thyroid eye disease

Introduction

Graves' disease is an autoimmune disorder caused by auto-antibodies against the thyroid stimulating hormone receptor (TSHR). Overstimulation of the TSHR induces hyperthyroidism and thyroid eye disease (TED) as the most common extra thyroidal manifestation of Graves' disease. In TED, the TSHR cross talks with the insulin-like growth factor 1 receptor (IGF-1R) in orbital fibroblasts leading to inflammation, deposition of hyaluronan and adipogenesis. The bone marrow may play an important role in autoimmune diseases, but its role in Graves' disease and TED is unknown. Here, we investigated whether induction of experimental Graves' disease and accompanying TED involves bone marrow activation and whether interference with IGF-1R signaling prevents this activation.

Results

Immunization of mice with TSHR resulted in an increase the numbers of CD4-positive T-lymphocytes (p ≤0.0001), which was normalized by linsitinib (p = 0.0029), an increase of CD19-positive B-lymphocytes (p= 0.0018), which was unaffected by linsitinib and a decrease of GR1-positive cells (p= 0.0038), which was prevented by linsitinib (p= 0.0027). In addition, we observed an increase of Sca-1 positive hematopietic stem cells (p= 0.0007) and of stromal cell-derived factor 1 (SDF-1) (p ≤0.0001) after immunization with TSHR which was prevented by linsitinib (Sca-1: p= 0.0008, SDF-1: p ≤0.0001). TSHR-immunization also resulted in upregulation of CCL-5, IL-6 and osteopontin (all p ≤0.0001) and a concomitant decrease of the immune-inhibitory cytokines IL-10 (p= 0.0064) and PGE2 (p ≤0.0001) in the bone marrow (all p≤ 0.0001). Treatment with the IGF-1R antagonist linsitinib blocked these events (all p ≤0.0001). We further demonstrate a down-regulation of arginase-1 expression (p= 0.0005) in the bone marrow in TSHR immunized mice, with a concomitant increase of local arginine (p ≤0.0001). Linsitinib induces an upregulation of arginase-1 resulting in low arginase levels in the bone marrow. Reconstitution of arginine in bone marrow cells in vitro prevented immune-inhibition by linsitinib.

Conclusion

Collectively, these data indicate that the bone marrow is activated in experimental Graves' disease and TED, which is prevented by linsitinib. Linsitinib-mediated immune-inhibition is mediated, at least in part, by arginase-1 up-regulation, consumption of arginine and thereby immune inhibition.

The Role of Adipsin, Complement Factor D, in the Pathogenesis of Graves' Orbitopathy

Purpose

Graves' orbitopathy (GO) is an orbital manifestation of autoimmune Graves' disease, and orbital fibroblast is considered a target cell, producing pro-inflammatory cytokines and/or differentiating into adipocytes. Adipose tissue has been focused on as an endocrine and inflammatory organ secreting adipokines. We investigated the pathogenic role of a specific adipokine, adipsin, known as complement factor D in Graves' orbital fibroblasts.

Methods

The messenger RNA (mRNA) expression of multiple adipokines was investigated in adipose tissues harvested from GO and healthy subjects. Adipsin protein production was analyzed in primary cultured orbital fibroblasts under insulin growth factor (IGF)-1, CD40 ligand (CD40L) stimulation, and adipogenesis. The effect of blocking adipsin with small interfering RNA (siRNA) on pro-inflammatory cytokine production and adipogenesis was evaluated using quantitative real-time PCR, Western blot, and ELISA. Adipogenic differentiation was identified using Oil Red O staining.

Results

Adipsin gene expression was significantly elevated in GO tissue and increased after the stimulation of IGF-1 and CD40L, as well as adipocyte differentiation in GO cells. Silencing of adipsin suppressed IGF-1-induced IL-6, IL-8, COX2, ICAM-1, CCL2 gene expression, and IL-6 protein secretion. Adipsin suppression also attenuated adipocyte differentiation. Exogenous treatment of recombinant adipsin resulted in the activation of the Akt, ERK, p-38, and JNK signaling pathways.

Conclusions

Adipsin, secreted by orbital fibroblasts, may play a distinct role in the pathogenesis of GO. Inhibition of adipsin ameliorated the production of pro-inflammatory cytokines and adipogenesis in orbital fibroblasts. Our study provides an in vitro basis suggesting adipsin as a potential therapeutic target for GO treatment.

Linsitinib, an IGF-1R inhibitor, attenuates disease development and progression in a model of thyroid eye disease

Introduction

Graves' disease (GD) is an autoimmune disorder caused by autoantibodies against the thyroid stimulating hormone receptor (TSHR) leading to overstimulation of the thyroid gland. Thyroid eye disease (TED) is the most common extra thyroidal manifestation of GD. Therapeutic options to treat TED are very limited and novel treatments need to be developed. In the present study we investigated the effect of linsitinib, a dual small-molecule kinase inhibitor of the insulin-like growth factor 1 receptor (IGF-1R) and the Insulin receptor (IR) on the disease outcome of GD and TED.

Methods

Linsitinib was administered orally for four weeks with therapy initiating in either the early ("active") or the late ("chronic") phases of the disease. In the thyroid and the orbit, autoimmune hyperthyroidism and orbitopathy were analyzed serologically (total anti-TSHR binding antibodies, stimulating anti TSHR antibodies, total T4 levels), immunohistochemically (H&E-, CD3-, TNFa- and Sirius red staining) and with immunofluorescence (F4/80 staining). An MRI was performed to quantify in vivo tissue remodeling inside the orbit.

Results

Linsitinib prevented autoimmune hyperthyroidism in the early state of the disease, by reducing morphological changes indicative for hyperthyroidism and blocking T-cell infiltration, visualized by CD3 staining. In the late state of the disease linsitinib had its main effect in the orbit. Linsitinib reduced immune infiltration of T-cells (CD3 staining) and macrophages (F4/80 and TNFa staining) in the orbita in experimental GD suggesting an additional, direct effect of linsitinib on the autoimmune response. In addition, treatment with linsitinib normalized the amount of brown adipose tissue in both the early and late group. An in vivo MRI of the late group was performed and revealed a marked decrease of inflammation, visualized by ¹⁹F MR imaging, significant reduction of existing muscle edema and formation of brown adipose tissue.

Conclusion

Here, we demonstrate that linsitinib effectively prevents development and progression of thyroid eye disease in an experimental murine model for Graves' disease. Linsitinib improved the total disease outcome, indicating the clinical significance of the findings and providing a path to therapeutic intervention of Graves' Disease. Our data support the use of linsitinib as a novel treatment for thyroid eye disease.

Efficacy and Safety of 6-Weekly versus 12-Weekly Intravenous Methylprednisolone in Moderate-to-Severe Active Thyroid-Associated Ophthalmopathy

PURPOSE

To compare the efficacy and safety of 6-weekly and 12-weekly intravenous methylprednisolone (IVMP) regimens in moderate-to-severe, active thyroid-associated orbitopathy (TAO) patients.

BASIC PROCEDURES

Retrospective comparative study of patients who received IVMP between January 2011 and July 2021 at the Thyroid Eye Clinic, the Chinese University of Hong Kong. Outcome measures included the 7-item clinical activity score (CAS), exophthalmos, extraocular muscle motility (EOMy), marginal reflex distance (MRD), best corrected visual acuity (BCVA), intraocular pressure (IOP), the requirement of additional treatment, and complications.

MAIN FINDINGS

A total of 65 (63% (41/65) females) moderate-to-severe, active TAO patients aged 50 ± 13 (25-74) years received 6-weekly (n = 22) or 12-weekly (n = 43) IVMP. Sex, age, smoking status, and Graves' disease status were comparable in the two groups (all p > 0.05). CAS at week 6 (p = 0.0279), 12 (p = 0.00228), and 52 (p = 0.0228) were lower at each time for the 12-weekly group. Exophthalmos improved more at week 6 (p = 0.0453) and 12 (p = 0.0347) in the 12-weekly group. The improvement of diplopia, MRD1, MRD2, and EOMy were comparable between the two groups. More patients in the 6-weekly group (p = 0.00169) required additional treatments including IVMP+/-ORT. Patients in the 6-weekly group who did not require additional treatment had a lower presenting CAS (p = 0.0193) than those who required additional treatment. The total numbers of adverse events were comparable between the two groups.

Influence of biological sex, age and smoking on Graves’ orbitopathy – a ten-year tertiary referral center analysis

Purpose

Severity of Graves’ orbitopathy (GO) shows wide individual differences. For optimal treatment, it is important to be able to predict the natural course of the disease as accurate as possible to counteract with anti-inflammatory and surgical treatment. Therefore, we aimed to further elucidate the impact of sex, age and smoking on GO.

Methods

We collected the clinical and demographic data of all patients of our tertiary referral center from January 2008 till December 2018 and analyzed it with descriptive statistics. Only patients with a complete data set were included in the further analysis. Odds ratio’s for moderate-to-severe and sight-threatening GO in relation to age, sex and smoking were calculated by means of multivariate logistic regression models.

Results

We evaluated the data of 4260 patient with GO and complete data sets. Most of these were women (83%). There were no significant differences between male and female patients regarding smoking habits and thyroid treatment. Men were significantly older at initial manifestation of TED (51.8 vs. 49.9y, p<0.01) and showed significant more often severe stages (61% vs. 53%, p<0.0001). Therefore, they needed significantly more intense treatment with steroids, irradiation, orbital decompression and muscle surgery. In multivariate logistic regression analyses age (OR 0.97, 95% CI:0.97-0.98, p<0.0001), male sex (OR 1.64, 95% CI:1.38-1.9, p<0.0001), smoking (OR 1.19, 95% CI:1.04-1.36, p=0.01), Grave’s disease (OR 1.55, 95% CI:1.26-1.90, p<0.0001) and history of radioiodine treatment (RAI) (OR 2.44, 95% CI:2.10-2.86, p<0.0001) showed an significant association with severe stages of GO.

Discussion

Our retrospective analysis showed once more that women are more often afflicted by GO. In contrast, men seem to be more severely afflicted and in need of anti-inflammatory and surgical treatments. This might be due to a different approach to the health system and resilience to GO specific symptoms, as well as previously described worse thyroid control. Estrogen mediated effects might also play a role as in other autoimmune diseases and should be subject of further trials. Besides the biological sex, smoking could again be confirmed as serious risk factor for severe GO. Of note, RAI was associated with more severe stages of GO, which should be subject to further investigation.

Change in lacrimal gland volume and aqueous tear production following treatment with teprotumumab

BACKGROUND

Dry eye syndrome occurs in up to 85% of patients with thyroid eye disease (TED). Lacrimal gland enlargement correlates with subjective tearing and a reduction in quality of life in patients with TED.

METHODS

In this prospective longitudinal study, patients presenting for the treatment of TED were considered for eligible. Primary outcomes included a change in the volume of the lacrimal gland and the production of tears following treatment with teprotumumab. The volume of lacrimal glands and proptosis was calculated using 3D volumetric analysis. Tear production was measured by Schirmer's test and associated symptoms were assessed using the VLSQ-8. The orbit with the most proptosis was designated the study orbit and the contralateral orbit was designated the fellow orbit.

RESULTS

Twenty patients were included. Mean (SD) age was 61 (18) and mean duration of TED prior to therapy was 48 months (47). Lacrimal gland volume in the study orbit decreased from 768 mm³ (288) to 486 mm³ (173) (p < 0.01) following therapy. For the fellow orbit, volume reduced from 637 mm³ (261) to 379 mm³ (147) (p < 0.01). Schirmer's test reading (STR) in the study orbit increased from 14.5 mm (8.2) to 23 mm (10) (p < 0.01) (59%) following treatment. In the fellow orbit, STR increased from 12.7 mm (7) to 21 mm (9) post therapy (69%) (p < 0.01). There was a significant improvement on all parts of the VLSQ-8.

CONCLUSION

Teprotumumab significantly reduces TED related expansion of the lacrimal gland, increases tear production, and improves dry eye symptoms.

Sphingolipids in thyroid eye disease

Graves' disease (GD) is caused by an autoimmune formation of autoantibodies and autoreactive T-cells against the thyroid stimulating hormone receptor (TSHR). The autoimmune reaction does not only lead to overstimulation of the thyroid gland, but very often also to an immune reaction against antigens within the orbital tissue leading to thyroid eye disease, which is characterized by activation of orbital fibroblasts, orbital generation of adipocytes and myofibroblasts and increased hyaluronan production in the orbit. Thyroid eye disease is the most common extra-thyroidal manifestation of the autoimmune Graves' disease. Several studies indicate an important role of sphingolipids, in particular the acid sphingomyelinase/ceramide system and sphingosine 1-phosphate in thyroid eye disease. Here, we discuss how the biophysical properties of sphingolipids contribute to cell signaling, in particular in the context of thyroid eye disease. We further review the role of the acid sphingomyelinase/ceramide system in autoimmune diseases and its function in T lymphocytes to provide some novel hypotheses for the pathogenesis of thyroid eye disease and potentially allowing the development of novel treatments.

Management of Thyroid Eye Disease: A Consensus Statement by the American Thyroid Association and the European Thyroid Association

Thyroid eye disease (TED) remains challenging for clinicians to evaluate and manage. Novel therapies have recently emerged, and their specific roles are still being determined. Most patients with TED develop eye manifestations while being treated for hyperthyroidism and under the care of endocrinologists. Endocrinologists, therefore, have a key role in diagnosis, initial management, and selection of patients who require referral to specialist care. Given that the need for guidance to endocrinologists charged with meeting the needs of patients with TED transcends national borders, and to maximize an international exchange of knowledge and practices, the American Thyroid Association and European Thyroid Association joined forces to produce this consensus statement.

Management of thyroid eye disease: a Consensus Statement by the American Thyroid Association and the European Thyroid Association

Thyroid eye disease (TED) remains challenging for clinicians to evaluate and manage. Novel therapies have recently emerged, and their specific roles are still being determined. Most patients with TED develop eye manifestations while being treated for hyperthyroidism and under the care of endocrinologists. Endocrinologists, therefore, have a key role in diagnosis, initial management, and selection of patients who require referral to specialist care. Given that the need for guidance to endocrinologists charged with meeting the needs of patients with TED transcends national borders, and to maximize an international exchange of knowledge and practices, the American Thyroid Association and European Thyroid Association joined forces to produce this Consensus Statement.

Teprotumumab Divergently Alters Fibrocyte Gene Expression: Implications for Thyroid-associated Ophthalmopathy

CONTEXT

Teprotumumab, an IGF-I receptor (IGF-IR) inhibitor, is effective in thyroid-associated ophthalmopathy (TAO). The drug can modulate induction by TSH of IL-6 and IL-8 in CD34+ fibrocytes and their putative derivatives, CD34+ orbital fibroblasts (CD34+ OF). Fibrocytes express multiple thyroid autoantigens and cytokines implicated in TAO, which are downregulated by Slit2. Inflammation and disordered hyaluronan (HA) accumulation occur in TAO. Whether teprotumumab alters these processes directly in fibrocytes/CD34+ OF remains uncertain.

OBJECTIVE

Determine teprotumumab effects on expression/synthesis of several TAO-relevant molecules in fibrocytes and GD-OF.

DESIGN/SETTING/PARTICIPANTS

Patients with TAO and healthy donors were recruited from an academic endocrine and oculoplastic practice.

MAIN OUTCOME MEASURES

Real-time PCR, specific immunoassays.

RESULTS

Teprotumumab attenuates basal and TSH-inducible autoimmune regulator protein, thyroglobulin, sodium iodide symporter, thyroperoxidase, IL-10, and B-cell activating factor levels in fibrocytes. It downregulates IL-23p19 expression/induction while enhancing IL-12p35, intracellular and secreted IL-1 receptor antagonists, and Slit2. These effects are mirrored by linsitinib. HA production is marginally enhanced by teprotumumab, the consequence of enhanced HAS2 expression.

CONCLUSION

Teprotumumab affects specific gene expression in fibrocytes and GD-OF in a target-specific, nonmonolithic manner, whereas IGF-IR control of these cells appears complex. The current results suggest that the drug may act on cytokine expression and HA production systemically and locally, within the TAO orbit. These findings extend our insights into the mechanisms through which IGF-IR inhibition might elicit clinical responses in TAO, including a potential role of Slit2 in attenuating inflammation and tissue remodeling.

Mechanisms in Graves Eye Disease: Apoptosis as the End Point of Insulin-Like Growth Factor 1 Receptor Inhibition

Background: Graves' eye disease, also called Graves' orbitopathy (GO), is a potentially debilitating autoimmune disease associated with retro-orbital inflammation and tissue expansion, involving both fibroblasts and adipocytes, resulting in periorbital edema, worsening proptosis, and muscle dysfunction with diplopia and may ultimately threaten sight. Accumulating evidence has indicated that autoantibodies to the thyrotropin receptor (TSHR), which induce the hyperthyroidism of Graves' disease, also help mediate the pathogenesis of the eye disease in susceptible individuals through TSHR expression on retro-orbital cells. Since it has long been known that the effects of insulin-like growth factor 1 (IGF-1) and thyrotropin are additive, recent clinical trials with a human monoclonal IGF-1 receptor blocking antibody (teprotumumab; IGF-1R-B-monoclonal antibody [mAb]) have demonstrated its ability to induce significant reductions in proptosis, diplopia, and clinical activity scores in patients with GO. However, the molecular mechanisms by which such an antibody achieves this result is unclear. Methods: We have used Li-Cor In-Cell Western, Western blot, and immunohistochemistry to define levels of different proteins in mouse and human fibroblast cells. Proteomic array was also used to define pathway signaling molecules. Using CCK-8 and BrdU cell proliferation ELISA, we have analyzed proliferative response of these cells to different antibodies. Results: We now show that a stimulating TSHR antibody was able to induce phosphorylation of the IGF-1R and initiate both TSHR and IGF-1R signaling in mouse and human fibroblasts. IGF-1R-B-mAb (1H7) inhibited all major IGF-1R signaling cascades and also reduced TSHR signaling. This resulted in the antibody-induced suppression of autophagy as shown by inhibition of multiple autophagy-related proteins (Beclin1, LC3a, LC3b, p62, and ULK1) and the induction of cell death by apoptosis as evidenced by activation of cleaved caspase 3, FADD, and caspase 8. Furthermore, this IGF-1R-blocking mAb suppressed serum-induced perkin and pink mitophagic proteins. Conclusions: Our observations clearly indicated that stimulating TSHR antibodies were able to enhance IGF-1R activity and contribute to retro-orbital cellular proliferation and inflammation. In contrast, an IGF-1R-B-mAb was capable of suppressing IGF-1R signaling leading to retro-orbital fibroblast/adipocyte death through the cell-extrinsic pathway of apoptosis. This is likely the major mechanism involved in proptosis reduction in patients with Graves' eye disease treated by IGF-1R inhibition.

Inhibition of TSH/IGF-1 Receptor Crosstalk by Teprotumumab as a Treatment Modality of Thyroid Eye Disease

CONTEXT

We previously presented evidence that TSH receptor (TSHR)-stimulating autoantibodies (TSAbs) bind to and activate TSHRs but do not bind to IGF1 receptors (IGF1Rs). Nevertheless, we showed that IGF1Rs were involved in thyroid eye disease (TED) pathogenesis because TSAbs activated crosstalk between TSHR and IGF1R. Teprotumumab, originally generated to inhibit IGF1 binding to IGF1R, was recently approved for the treatment of TED (Tepezza).

OBJECTIVE

To investigate the role of TSHR/IGF1R crosstalk in teprotumumab treatment of TED.

DESIGN

We used orbital fibroblasts from patients with TED (TEDOFs) and measured stimulated hyaluronan (HA) secretion as a measure of orbital fibroblast activation by TED immunoglobulins (TED-Igs) and monoclonal TSAb M22. We previously showed that M22, which does not bind to IGF1R, stimulated HA in a biphasic dose-response with the higher potency phase dependent on TSHR/IGF1R crosstalk and the lower potency phase independent of IGF1R. Stimulation by TED-Igs and M22 was measured in the absence or presence of teprotumumab biosimilar (Tepro) or K1-70, an antibody that inhibits TSHR.

RESULTS

We show: (1) Tepro dose-dependently inhibits stimulation by TED-Igs; (2) Tepro does not bind to TSHRs; (3) Tepro inhibits IGF1R-dependent M22-induced HA production, which is mediated by TSHR/IGF1R crosstalk, but not IGF1R-independent M22 stimulation; and (4) β-arrestin 1 knockdown, which blocks TSHR/IGF1R crosstalk and prevents Tepro inhibition of HA production by M22 and by a pool of TED-Igs.

CONCLUSION

We conclude that Tepro inhibits HA production by TEDOFs by inhibiting TSHR/IGF1R crosstalk and suggest that inhibition of TSHR/IGF1R crosstalk is the mechanism of its action in treating TED.

Thyroid dermopathy responds to teprotumumab therapy

Summary

Thyroid dermopathy is an uncommon manifestation of thyroid disease that impairs the quality of life in certain cases. Currently, the available treatments offer limited results and a chance of recurrence. Teprotumumab, a novel medication that results in the regression of thyroid ophthalmopathy, may have similar effects on dermopathy. We describe four patients treated with teprotumumab for their thyroid ophthalmopathy who concomitantly had dermatopathy upon initiation of their infusions. Patients improved after two to three infusions and three out of the four patients have not suffered a recurrence.Teprotumumab is a monoclonal antibody (MAB) that attenuates an inflammatory response, resulting in decreased edema and tissue expansion. Given the similarities of their pathophysiology, we believe that the resolution of thyroid dermatopathy and regression of thyroid eye disease occurs via the same mechanism. We encourage further investigation utilizing teprotumumab for patients whose dermopathy is associated with impaired quality of life.

Learning points

Thyroid dermopathy (TD), an uncommon manifestation of thyroid disease, may occasionally impair function and quality of life. There are only a few treatments for TD, with limited results and high rates of recurrence. Teprotumumab is a Food and Drug Administration-approved medication used for thyroid eye disease (TED). Our patients treated with teprotumumab for TED showed improvement of TD, which demonstrates its potential use for this condition.

TSH stimulation of human thyroglobulin and thyroid peroxidase gene transcription is partially dependent on internalization

The TSH receptor (TSHR) is the major regulator of thyroid hormone biosynthesis in human thyrocytes by regulating the transcription of a number of genes including thyroglobulin (TG) and thyroperoxidase (TPO). Until recently, it was thought that TSHR initiated signal transduction pathways only at the cell-surface and that internalization was primarily involved in TSHR desensitization and downregulation. Studies primarily in mouse cells showed that TSHR internalization regulates gene transcription at an intracellular site also. However, this has not been shown for genes involved in thyroid hormone biosynthesis in human thyrocytes. We used human thyrocytes in primary culture. In these cells, the dose-response to TSH for gene expression is biphasic with low doses upregulating gene expression and higher doses decreasing gene expression. We used two approaches to inhibit internalization. In the first, we used inhibitors of dynamins, dynasore and dyngo-4a. Pretreatment with dynasore or dyngo-4a markedly inhibited TSH upregulation of TG and TPO mRNAs, as well as TG secretion. In the second, we used knockdown of dynamin 2, which is the most abundant dynamin in human thyrocytes. We showed that dynamin 2 knockdown inhibited TSHR internalization and decreased the TSH-stimulated levels of TG and TPO mRNAs and proteins. Lastly, we showed that the level of the activatory transcription factor phosphorylated cAMP response element binding protein (pCREB) in the cell nuclei was reduced by 68% when internalization was inhibited. We conclude that upregulation of genes involved in thyroid hormone synthesis in human thyrocytes is, in part, dependent on internalization leading to nuclear localization of an activated transcription factor(s).

Proximity ligation assay to study TSH receptor homodimerization and crosstalk with IGF-1 receptors in human thyroid cells

Proximity ligation assay (PLA) is a methodology that permits detection of protein-protein closeness, that is, proteins that are within 40 nanometers of each other, in cells or tissues at endogenous protein levels or after exogenous overexpression. It detects the protein(s) with high sensitivity and specificity because it employs a DNA hybridization step followed by DNA amplification. PLA has been used successfully with many types of proteins. In this methods paper, we will describe the workings of PLA and provide examples of its use to study TSH/IGF-1 receptor crosstalk in Graves' orbital fibroblasts (GOFs) and TSH receptor homodimerization in primary cultures of human thyrocytes.

Effect of teprotumumab on intraocular pressure in thyroid-associated ophthalmopathy

PURPOSE:

MATERIALS AND METHODS:

RESULTS:

CONCLUSION:

Therapeutic Potential of Targeting Periostin in the Treatment of Graves' Orbitopathy

Periostin is a matricellular protein that is ubiquitously expressed in normal human tissues and is involved in pathologic mechanism of chronic inflammatory and fibrotic disease. In this study we investigate periostin in the pathogenesis of Graves' orbitopathy (GO) using human orbital adipose tissue obtained from surgery and primary cultured orbital fibroblasts in vitro. POSTN (gene encoding periostin) expression in Graves' orbital tissues and healthy control tissues was studied, and the role of periostin in GO pathologic mechanism was examined through small-interfering RNA (siRNA)-mediated silencing. POSTN gene expression was significantly higher in Graves' orbital tissues than healthy control tissues in real-time PCR results, and immunohistochemical staining revealed higher expression of periostin in Graves' orbital tissues than normal tissues. Silencing periostin using siRNA transfection significantly attenuated TGF-β-induced profibrotic protein production and phosphorylated p38 and SMAD protein production. Knockdown of periostin inhibited interleukin-1 β -induced proinflammatory cytokines production as well as phosphorylation of NF-κB and Ak signaling protein. Adipocyte differentiation was also suppressed in periostin-targeting siRNA transfected GO cells. We hypothesize that periostin contributes to the pathogenic process of inflammation, fibrosis and adipogenesis of GO. Our study provides in vitro evidence that periostin may be a novel potential therapeutic target for the treatment of GO.

Graves' Autoantibodies Exhibit Different Stimulating Activities in Cultures of Thyrocytes and Orbital Fibroblasts Not Reflected by Clinical Assays

Background: The pathogenesis of Graves' hyperthyroidism (GH) and associated Graves' orbitopathy (GO) appears to involve stimulatory autoantibodies (thyrotropin receptor [TSHR]-stimulating antibodies [TSAbs]) that bind to and activate TSHRs on thyrocytes and orbital fibroblasts. In general, measurement of circulating TSHR antibodies by clinical assays correlates with the status of GH and GO. However, most clinical measurements of TSHR antibodies use competitive binding assays that do not distinguish between TSAbs and antibodies that bind to but do not activate TSHRs. Moreover, clinical assays for TSAbs measure stimulation of only one signaling pathway, the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway, in engineered cells that are not thyrocytes or orbital fibroblasts. We determined whether measuring TSAbs by a cAMP-PKA readout in engineered cells accurately reveals the efficacies of stimulation by these antibodies on thyrocytes and orbital fibroblasts. Methods: We measured TSAb stimulation of normal human thyrocytes and orbital fibroblasts from patients with GO in primary cultures in vitro. In thyrocytes, we measured secretion of thyroglobulin (TG) and in orbital fibroblasts secretion of hyaluronan (hyaluronic acid [HA]). We also measured stimulation of cAMP production in engineered TSHR-expressing cells in an assay similar to clinical assays. Furthermore, we determined whether there were differences in stimulation of thyrocytes and orbital fibroblasts by TSAbs from patients with GH alone versus from patients with GO understanding that patients with GO have accompanying GH. Results: We found a positive correlation between TSAb stimulation of cAMP production in engineered cells and TG secretion by thyrocytes as well as HA secretion by orbital fibroblasts. However, TSAbs from GH patients stimulated thyrocytes more effectively than TSAbs from GO patients, whereas TSAbs from GO patients were more effective in activating orbital fibroblasts than TSAbs from GH patients. Conclusions: Clinical assays of stimulation by TSAbs measuring activation of the cAMP-PKA pathway do correlate with stimulation of thyrocytes and orbital fibroblasts; however, they do not distinguish between TSAbs from GH and GO patients. In vitro, TSAbs exhibit selectivity in activating TSHRs since TSAbs from GO patients were more effective in stimulating orbital fibroblasts and TSAbs from GH patients were more effective in stimulating thyrocytes.

The Role of Mitochondria-Linked Fatty-Acid Uptake-Driven Adipogenesis in Graves Orbitopathy

CONTEXT

Depot-specific expansion of orbital adipose tissue (OAT) in Graves orbitopathy (GO; an autoimmune condition producing proptosis, visual impairment and reduced quality of life) is associated with fatty acid (FA)-uptake-driven adipogenesis in preadipocytes/fibroblasts (PFs).

OBJECTIVE

This work sought a role for mitochondria in OAT adipogenesis in GO.

METHODS

Confluent PFs from healthy OAT (OAT-H), OAT from GO (OAT-GO) and white adipose tissue in culture medium compared with culture medium containing a mixed hormonal cocktail as adipogenic medium (ADM), or culture-medium containing FA-supplementation, oleate:palmitate:linoleate (45:30:25%) with/without different concentration of mitochondrial biosubstrate adenosine 5'-diphosphate/guanosine 5'-diphosphate (ADP/GDP), AICAR (adenosine analogue), or inhibitor oligomycin-A for 17 days. Main outcome measures included oil-red-O staining and foci count of differentiated adipocytes for in vitro adipogenesis, flow cytometry, relative quantitative polymerase chain reaction, MTS-assay/106 cells, total cellular-ATP detection kit, and Seahorse-XFe96-Analyzer for mitochondria and oxidative-phosphorylation (OXPHOS)/glycolysis-ATP production analysis.

RESULTS

During early adipogenesis before adipocyte formation (days 0, 4, and7), we observed OAT-specific cellular ATP production via mitochondrial OXPHOS in PFs both from OAT-H and OAT-GO, and substantially disrupted OXPHOS-ATP/glycolysis-ATP production in PFs from OAT-GO, for example, a 40% reduction in OXPHOS-ATP and trend-increased glycolysis-ATP production on days 4 and 7 compared with day 0, which contrasted with the stable levels in OAT-H. FA supplementation in culture-medium triggered adipogenesis in PFs both from OAT-H and OAT-GO, which was substantially enhanced by 1-mM GDP reaching 7% to 18% of ADM adipogenesis. The FA-uptake-driven adipogenesis was diminished by oligomycin-A but unaffected by treatment with ADP or AICAR. Furthermore, we observed a significant positive correlation between FA-uptake-driven adipogenesis by GDP and the ratios of OXPHOS-ATP/glycolysis-ATP through adipogenesis of PFs from OAT-GO.

CONCLUSION

Our study confirmed that FA uptake can drive OAT adipogenesis and revealed a fundamental role for mitochondria-OXPHOS in GO development, which provides potential for therapeutic interventions.

Reactivities of a Prostanoid EP2 Agonist, Omidenepag, Are Useful for Distinguishing between 3D Spheroids of Human Orbital Fibroblasts without or with Graves' Orbitopathy

Background. To obtain new insights into the activation of the thyroid-stimulating hormone (TSH) and insulin-like growth factor 1 (IGF-1) receptors in human orbital fibroblasts (n-HOFs), the effects of the prostanoid EP2 agonist, omidenepag (OMD), and a rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor, ripasudil (Rip) were evaluated using three-dimension (3D) n-HOFs spheroids in the absence and presence of the recombinant human TSH receptor antibodies, M22 and IGF-1. Methods. The effects of 100 nM OMD or 10 μM Rip on the physical properties, size, stiffness, and mRNA expression of several extracellular matrix (ECM) molecules, their regulator, inflammatory cytokines, and endoplasmic reticulum (ER) stress-related factors were examined and compared among 3D spheroids of n-HOFs, M22-/IGF-1-activated n-HOFs and GO-related human orbital fibroblasts (GHOFs). Results. The physical properties and mRNA expressions of several genes of the 3D n-HOFs spheroids were significantly and diversely modulated by the presence of OMD or Rip. The OMD-induced effects on M22-/IGF-1-activated n-HOFs were similar to the effects caused by GHOHs, but quite different from those of n-HOFs. Conclusions. The findings presented herein indicate that the changes induced by OMD may be useful in distinguishing between n-HOFs and GHOFs.

Orbital Signaling in Graves' Orbitopathy

Graves' orbitopathy (GO) is a complex and poorly understood disease in which extensive remodeling of orbital tissue is dominated by adipogenesis and hyaluronan production. The resulting proptosis is disfiguring and underpins the majority of GO signs and symptoms. While there is strong evidence for the thyrotropin receptor (TSHR) being a thyroid/orbit shared autoantigen, the insulin-like growth factor 1 receptor (IGF1R) is also likely to play a key role in the disease. The pathogenesis of GO has been investigated extensively in the last decade with further understanding of some aspects of the disease. This is mainly derived by using in vitro and ex vivo analysis of the orbital tissues. Here, we have summarized the features of GO pathogenesis involving target autoantigens and their signaling pathways.

Facial and Eyelid Changes in Thyroid Eye Disease Are Reversed by Teprotumumab

Thyroid eye disease (TED) causes orbital soft-tissue expansion. Recent studies have suggested that brow and temple changes may also occur. Teprotumumab, a monoclonal antibody to the insulin-like growth factor 1 receptor reduces soft-tissue swelling in TED. In this study, we quantified the changes to pan facial soft-tissue volumes and eyelid position, following treatment with teprotumumab.

IL-38 Exerts Anti-Inflammatory and Antifibrotic Effects in Thyroid-Associated Ophthalmopathy

CONTEXT

Thyroid-associated ophthalmopathy (TAO) is an organ-specific autoimmune disease closely associated with Graves' disease. IL-38, a novel cytokine in the IL-1 superfamily, has been reported to be involved in the pathogenesis of various autoimmune diseases.

OBJECTIVE

We aimed to evaluate the relationship between IL-38 and TAO disease activity and its role in inflammation and fibrosis in TAO.

METHODS

Blood samples and orbital connective tissues were collected from TAO patients and controls. Orbital fibroblasts were isolated from patients with TAO. Enzyme-linked immunosorbent assay, immunohistochemistry, flow cytometry, immunofluorescence, quantitative real-time PCR and Western blot analysis were performed.

RESULTS

Here, we demonstrated that IL-38 levels decreased in the circulation and orbital connective tissues of patients with TAO compared with the controls, and levels were negatively correlated with the clinical activity score. In vitro, potent anti-inflammatory and antifibrotic effects of IL-38 were observed. Furthermore, we revealed that IL-38 can counteract the phosphorylation of star molecules in multiple classical pathways.

CONCLUSION

IL-38 plays a protective role in TAO and is associated with its pathogenesis. Our data suggest that IL-38 may be a promising marker of TAO disease activity and a potential target for TAO therapy.

Teprotumumab for the treatment of chronic thyroid eye disease

Background

Teprotumumab, a novel IGF-1R antibody was recently shown to significantly reduce the signs of active Thyroid eye disease (TED). The current study reviews its efficacy in chronic TED.

Methods

In this retrospective review, consecutive patients with chronic stable TED (>2 years), who had received ≥3 infusions of teprotumumab were included. All patients had measurements of proptosis, and calculation of the CAS and diplopia scores before and after therapy. Five-point strabismus scores were also calculated. Patients who had imaging within 4 months prior to therapy and 6 weeks post therapy underwent orbital 3D volumetric analysis.

Results

Thirty-one patients met the inclusion criteria. The mean (SD) duration of TED was 81 months (56) and the mean (SD) number of infusions received by each patient was 7 (2). Mean (SD) reduction in proptosis for each study orbit was 3.5 mm (0.4) and 3 mm (0.3) for the fellow orbit. The CAS response was 90% for the study orbit and 87% for the fellow orbit. Of the 15 patients who had diplopia at baseline, 67% had a clinically significant response, while 47% had complete resolution following treatment. Following teprotumumab, mean (SD) reduction of muscle tissue was 2011 mm³ (1847) in the study orbit and 1620 mm³ (1759) in the fellow orbit. The mean (SD) reduction of fat volume was 2101 mm³ (1681) in the study orbit and 1370 mm³ (1181) in the fellow orbit.

Conclusion

Teprotumumab significantly reduces proptosis, inflammation, diplopia, strabismus and orbital soft tissue volume in patients with chronic TED.

Teprotumumab for thyroid eye disease: early response is not required for benefit

Purpose

In recent trials, 50% of patients treated with teprotumumab for thyroid eye disease had significant improvements in proptosis at 6 weeks. However, a small subgroup of patients did not have a significant response by week 12. We examine the outcomes at week 24 in patients from both trials who had little or no proptosis response at week 12.

Design

In this post hoc analysis, data from teprotumumab-treated patients in the placebo-controlled randomized phases 2 and 3 trials were reviewed.

Methods

Patients treated with teprotumumab or placebo with a ≤2 mm reduction from baseline in proptosis at week 12 and completed assessments at both the weeks 12 and 24 visits were included. The main outcome measures were a change in proptosis, clinical activity score (CAS) and diplopia in response to teprotumumab therapy at baseline and weeks 6, 12, 18, and 24.

Results

From the phases 2 and 3 studies, 24 patients from the treated and placebo groups were included for analysis (48 total). In the teprotumumab group, of the 24 who had no improvement in proptosis (≥2 mm from baseline) at 12 weeks, 15 (63%) demonstrated a clinically significant improvement at week 24. No patients from the 24 placebo patients had a clinically significant improvement in proptosis at 12 weeks, and 24 weeks. At week 12, 22 patients (92%) in the teprotumumab group had a significant reduction in the CAS (≥2 points) and at 24 weeks all patients achieved this reduction. At week 12, 11 (46%) patients from the placebo group had a significant improvement, while 10 (42%) had a significant improvement at 24 weeks. 22 of the 24 patients (92%) in the teprotumumab group had a diplopia grade > 0 at baseline. At week 12, 12 of the 22 (55%) had improvement in diplopia ≥ 1 grade. By week 24, 16 patients (73%) had an improvement in diplopia ≥ 1 grade. In the placebo group, 15 (63%) had significant diplopia. At week 12, 3 (20%) from this group had improvement in diplopia ≥ 1 grade, while at 24 weeks this number rose to 4 (27%).

Conclusions

There is variability in the time taken to manifest a clinically significant response to teprotumumab, some patients my need a longer time to respond.

Teprotumumab: Interpreting the Clinical Trials in the Context of Thyroid Eye Disease Pathogenesis and Current Therapies

Teprotumumab, a monoclonal antibody targeted against the insulin-like growth factor 1 (IGF-1) receptor, was recently approved by the United States Food and Drug Administration for the treatment of thyroid eye disease (TED). Phase 1 studies of teprotumumab for the treatment of malignancies demonstrated an acceptable safety profile but limited effectiveness. Basic research implicating the IGF-1 receptor on the CD-34+ orbital fibrocyte in the pathogenesis of TED renewed interest in the drug. Two multicenter, randomized, double-masked, clinical trials (phase 2 and 3) evaluated the efficacy of 8 infusions of teprotumumab every 3 weeks versus placebo in 170 patients with recent-onset active TED, as defined by a clinical activity score (CAS) of at least 4. Teprotumumab was superior to placebo for the primary efficacy end points in both studies: overall responder rate as defined by a reduction of 2 or more CAS points and a reduction of 2 mm or more in proptosis (69% vs. 20%; P < 0.001; phase 2 study) and proptosis responder rate as defined by a reduction of 2 mm or more in proptosis (83% vs. 10%; P < 0.001; phase 3 study). In both studies, treatment with teprotumumab compared with placebo achieved a significant mean reduction of proptosis (-3.0 mm vs. -0.3 mm, phase 2 study; -3.32 mm vs. -0.53 mm, phase 3 study) and CAS (-4.0 vs. -2.5, phase 2 study; -3.7 vs. -2.0, phase 3 study). Teprotumumab also resulted in a greater proportion of patients with a final CAS of 0 or 1, higher diplopia responder rate, and a larger improvement in the Graves' Ophthalmopathy Quality of Life overall score. More than half of patients (62%, phase 2 trial; 56%, phase 3 trial) who were primary end point responders maintained this response at 51 weeks after the last dose of therapy. The most common adverse events reported with teprotumumab included muscle spasms (25%), nausea (17%), alopecia (13%), diarrhea (13%), fatigue (10%), hearing impairment (10%), and hyperglycemia (8%). Teprotumumab is contraindicated for those with inflammatory bowel disease and who are pregnant. Although the current dosing regimen has proven effective for TED, dose-ranging studies including variable concentrations, infusion frequencies, and durations of teprotumumab therapy in the setting of TED have not been performed.

Octreotide inhibits secretion of IGF-1 from orbital fibroblasts in patients with thyroid-associated ophthalmopathy via inhibition of the NF-κB pathway

PURPOSE

We investigated the effect of octreotide, a long-acting somatostatin (SST) analogue, on IGF-1 secretion and its possible mechanism of action in orbital fibroblasts (OFs) from patients with thyroid-associated ophthalmopathy (TAO).

MATERIALS AND METHODS

OFs were isolated from the orbital fat of patients with TAO or healthy individuals. The expression level of insulin-like growth factor (IGF)-1, at the protein and mRNA level, was determined with ELISA and quantitative RT-PCR, respectively. The expression pattern of somatostatin receptor (SSTR) 2, which has the highest affinity for octreotide, was examined by flow cytometry. The activity of NF-κB pathway was determined by examining the levels of phosphorylation of IKKα/β and p65, and degradation of IκB via western blot analysis, and by measuring the activity of NF-kB-dependent luciferase via transfection with plasmids containing luciferase and NF-κB binding site.

RESULTS

OFs from patients with TAO showed significantly higher levels of IGF-1 secretion and NF-κB activity even in the absence of stimulation, compared to those from controls. Treatment with octreotide reduced the level of IGF-1 secretion in OFs from patients with TAO, but not in OFs from controls. OFs from patients with TAO expressed higher levels of SSTR2 on the cell surface, compared to controls. In addition, the expression of IGF-1 at the protein and mRNA level was dependent on the activity of NF-κB pathway in OFs from patients with TAO. Furthermore, treatment with octreotide reduced on the activity of NF-κB pathway in OFs from patients with TAO.

CONCLUSION

OFs from patients with TAO showed significantly higher levels of IGF-1 secretion via up-regulation of NF-κB activity. Treatment with octreotide inhibited the secretion of IGF-1 by reducing the NF-κB pathway in OFs, which expressed higher levels of SSRT2 on the cell surface, from patients with TAO.

Enrichment of IGF-1R and PPARγ signalling pathways in orbital inflammatory diseases: steps toward understanding pathogenesis

BACKGROUND

Orbital inflammatory disease (OID) encompasses a wide range of pathology including thyroid-associated orbitopathy (TAO), granulomatosis with polyangiitis (GPA), sarcoidosis and non-specific orbital inflammation (NSOI), accounting for up to 6% of orbital diseases. Understanding the underlying pathophysiology of OID can improve diagnosis and help target therapy.

AIMS

To test the hypothesis that shared signalling pathways are activated in different forms of OID.

METHODS

In this secondary analysis, pathway analysis was performed on the previously reported differentially expressed genes from orbital adipose tissue using patients with OID and healthy controls who were characterised by microarray. For the original publications, tissue specimens were collected from oculoplastic surgeons at 10 international centres representing four countries (USA, Canada, Australia and Saudi Arabia). Diagnoses were independently confirmed by two masked ocular pathologists (DJW, HEG). Gene expression profiling analysis was performed at the Oregon Health & Science University. Eighty-three participants were included: 25 with TAO, 6 with orbital GPA, 7 with orbital sarcoidosis, 25 with NSOI and 20 healthy controls.

RESULTS

Among the 83 subjects (mean (SD) age, 52.8 (18.3) years; 70% (n=58) female), those with OID demonstrated perturbation of the downstream gene expressions of the IGF-1R (MAPK/RAS/RAF/MEK/ERK and PI3K/Akt/mTOR pathways), peroxisome proliferator-activated receptor-γ (PPARγ), adipocytokine and AMPK signalling pathways compared with healthy controls. Specifically, GPA samples differed from controls in gene expression within the insulin-like growth factor-1 receptor (IGF-1R, PI3K-Akt (p=0.001), RAS (p=0.005)), PPARγ (p=0.002), adipocytokine (p=0.004) or AMPK (p=<0.001) pathways. TAO, sarcoidosis and NSOI samples were also found to have statistically significant differential gene expression in these pathways.

CONCLUSIONS

Although OID includes a heterogenous group of pathologies, TAO, GPA, sarcoidosis and NSOI share enrichment of common gene signalling pathways, namely IGF-1R, PPARγ, adipocytokine and AMPK. Pathway analyses of gene expression suggest that other forms of orbital inflammation in addition to TAO may benefit from blockade of IGF-1R signalling pathways.

Improvement of asymmetric thyroid eye disease with teprotumumab

Purpose

Teprotumumab, a specific blocking antibody to the insulin like growth factor 1 receptor, significantly reduced proptosis in patients with thyroid eye disease (TED) in recent clinical trials. Given its specificity, we expect it to demonstrate greater efficacy on the worse affected orbit, in patients with asymmetric TED. Herein, we investigate the differential impact of teprotumumab on the orbits of such patients.

Methods

In this pooled analysis of patients who were enrolled in the recent phase 2 (NCT01868997) and phase 3 (NCT03298867) trials, all patients with asymmetric TED (difference in exophthalmometry of ≥3 mm) were screened for eligibility. The primary outcomes of the trials, proptosis, diplopia and Clinical Activity Score (CAS) response, were evaluated in both orbits of patients who had received treatment or placebo, to examine the differential response from baseline to week 24.

Results

From a pooled group of 84 patients randomised to receive teprotumumab and 87 randomised to placebo, 10 (12%) and 12 (14%), respectively, met the inclusion criteria. The teprotumumab-treated patients demonstrated significant reductions in proptosis, CAS and diplopia in both orbits of each patient and this was not seen with placebo. The reduction in proptosis and CAS was significantly greater in the worse affected orbit, improving symmetry. In the placebo arm, while the mean CAS in the study eye reduced over time, proptosis and diplopia did not change in either orbit.

Conclusion

The findings in this study suggest the differential impact of teprotumumab on orbits that are clinically more affected by TED, suggesting that teprotumumab reduces asymmetry.

Modulating TSH Receptor Signaling for Therapeutic Benefit

Autoimmune thyroid-stimulating antibodies are activating the thyrotropin receptor (TSHR) in both the thyroid and the eye, but different molecular mechanisms are induced in both organs, leading to Graves' disease (GD) and Graves' orbitopathy (GO), respectively. Therapy with anti-thyroid drugs to reduce hyperthyroidism (GD) by suppressing the biosynthesis of thyroid hormones has only an indirect effect on GO, since it does not causally address pathogenic TSHR activation itself. GO is thus very difficult to treat. The activated TSHR but also the cross-interacting insulin-like growth factor 1 receptor (IGF-1R) contribute to this issue. The TSHR is a heptahelical G-protein-coupled receptor, whereas the IGF-1R is a receptor tyrosine kinase. Despite these fundamental structural differences, both receptors are phosphorylated by G-protein receptor kinases, which enables β-arrestin binding. Arrestins mediate receptor internalization and also activate the mitogen-activated protein kinase pathway. Moreover, emerging results suggest that arrestin plays a critical role in the cross-interaction of the TSHR and the IGF-1R either in their common signaling pathway and/or during an indirect or potential TSHR/IGF-1R interaction. In this review, novel pharmacological strategies with allosteric small-molecule modulators to treat GO and GD on the level of the TSHR and/or the TSHR/IGF-1R cross-interaction will be discussed. Moreover, monoclonal antibody approaches targeting the TSHR or the IGF-1R and thereby preventing activation of either receptor will be presented. Another chapter addresses the immunomodulation to treat GO using TSHR-derived peptides targeting the human leukocyte antigen DR isotope (HLA-DR), which is a feasible approach to tackle GO, since HLA-DR and TSHR are overexpressed in orbital tissues of GO patients.

Targeting TSH and IGF-1 Receptors to Treat Thyroid Eye Disease

Graves' disease (GD) is an autoimmune disease caused in part by thyroid-stimulating antibodies (TSAbs) that activate the thyroid-stimulating hormone receptor (TSHR). In Graves' hyperthyroidism (GH), TSAbs cause persistent stimulation of thyroid cells leading to continuous thyroid hormone synthesis and secretion. Thyroid eye disease (TED), also called Graves' orbitopathy, is an orbital manifestation of GD. We review the important roles of the TSHR and the insulin-like growth factor 1 receptor (IGF-1R) in the pathogenesis of TED and discuss a model of TSHR/IGF-1R crosstalk that considers two pathways initiated by TSAb activation of TSHR in the eye, an IGF-1R-independent and an IGF-1R-dependent signaling pathway leading to hyaluronan (HA) secretion in orbital fibroblasts. We discuss current and future therapeutic approaches targeting the IGF-1R and TSHR. Teprotumumab, a human monoclonal anti-IGF-1R-blocking antibody, has been approved as an effective treatment in patients with TED. However, as the TSHR seems to be the primary target for TSAbs in patients with GD, future therapeutic interventions directly targeting the TSHR, e.g. blocking antibodies and small molecule antagonists, are being developed and have the advantage to inhibit the IGF-1R-independent as well as the IGF-1R-dependent component of TSAb-induced HA secretion. Antigen-specific immunotherapies using TSHR peptides to reduce serum TSHR antibodies are being developed also. These TSHR-targeted strategies also have the potential to treat both GH and TED with the same drug. We propose that combination therapy targeting TSHR and IGF-1R may be an effective and better tolerated treatment strategy for TED.

Distinctive Features of Orbital Adipose Tissue (OAT) in Graves' Orbitopathy

Depot specific expansion of orbital-adipose-tissue (OAT) in Graves' Orbitopathy (GO) is associated with lipid metabolism signaling defects. We hypothesize that the unique adipocyte biology of OAT facilitates its expansion in GO. A comprehensive comparison of OAT and white-adipose-tissue (WAT) was performed by light/electron-microscopy, lipidomic and transcriptional analysis using ex vivo WAT, healthy OAT (OAT-H) and OAT from GO (OAT-GO). OAT-H/OAT-GO have a single lipid-vacuole and low mitochondrial number. Lower lipolytic activity and smaller adipocytes of OAT-H/OAT-GO, accompanied by similar essential linoleic fatty acid (FA) and (low) FA synthesis to WAT, revealed a hyperplastic OAT expansion through external FA-uptake via abundant SLC27A6 (FA-transporter) expression. Mitochondrial dysfunction of OAT in GO was apparent, as evidenced by the increased mRNA expression of uncoupling protein 1 (UCP1) and mitofusin-2 (MFN2) in OAT-GO compared to OAT-H. Transcriptional profiles of OAT-H revealed high expression of Iroquois homeobox-family (IRX-3&5), and low expression in HOX-family/TBX5 (essential for WAT/BAT (brown-adipose-tissue)/BRITE (BRown-in-whITE) development). We demonstrated unique features of OAT not presented in either WAT or BAT/BRITE. This study reveals that the pathologically enhanced FA-uptake driven hyperplastic expansion of OAT in GO is associated with a depot specific mechanism (the SLC27A6 FA-transporter) and mitochondrial dysfunction. We uncovered that OAT functions as a distinctive fat depot, providing novel insights into adipocyte biology and the pathological development of OAT expansion in GO.

Teprotumumab reduces extraocular muscle and orbital fat volume in thyroid eye disease

Purpose

Thyroid eye disease (TED) is a progressive, debilitating and potentially vision-threatening autoimmune disease. Teprotumumab, a novel human monoclonal antibody, has been shown to reverse the clinical manifestations of TED. Patients receiving teprotumumab have been shown in two multicenter, randomized placebo-controlled trials to have decreased proptosis, diplopia and inflammation after 24 weeks of treatment. This study aims to analyse volumetric and inflammatory changes on orbital imaging prior to and after teprotumumab treatment from one of these trials.

Design

Retrospective review.

Subjects

Six patients enrolled in the phase III teprotumumab clinical trial (OPTIC, NCT03298867) with active TED who received 24 weeks of teprotumumab and had pre- and post-treatment orbital imaging (CT or MRI). Additionally, 12 non-TED patients (24 orbits) were analysed as a comparative control group.

Methods

3D volumetric calculations of the extraocular muscles (EOMs), orbital fat, and bony orbit were measured using previously validated image processing software. 3D volumetric results and changes in EOM inflammation were compared with clinical measurements of TED.

Results

Total EOM volume within each orbit was markedly reduced post-teprotumumab in all patients (n=six patients, 12/12 orbits, p<0.02). There was no statistical difference in post-treatment EOM volume when compared to non-TED controls. Total orbital fat volume was also reduced in 11 of 12 studied orbits (n=six patients, p=0.04). Overall EOM inflammation based on MRI signal intensity ratio was reduced in 8/8 orbits (n=four patients, p<0.01).

Conclusion

Orbital imaging demonstrated decreased EOM volumes and orbital fat tissue volumes after teprotumumab treatment.

The Effect of Immunosuppression on Selected Antioxidant Parameters in Patients with Graves' Disease with Active Thyroid-Associated Orbitopathy

BACKGROUND AND STUDY AIMS

Thyroid-associated orbitopathy, the most common extrathyroidal manifestation of Graves' disease, is an autoimmune inflammation of orbital soft tissue. We report the study assessing the effect of immunosuppressive treatment with methylprednisolone on selected antioxidant parameters in patients with Graves' disease with active thyroid-associated orbitopathy.

PATIENTS AND METHODS

Activity and serum levels of selected antioxidant parameters as well as lipid peroxidation products were determined in a group of 56 patients with active thyroid-associated orbitopathy at three time-points: at baseline, after the discontinuation of intravenous methylprednisolone treatment and at 3 months after the discontinuation of additional oral methylprednisolone treatment. A control group consisted of 20 healthy age- and sex-matched volunteers.

RESULTS

We found an increased activity of superoxide dismutase and glutathione peroxidase and increased serum levels of uric acid, malondialdehyde and conjugated dienes, as well as a reduced activity of paraoxonase-1 and reduced serum vitamin C level in the study group at baseline. Systemic intravenous and oral methylprednisolone therapy led to normalization of activity and concentration of the most studied parameters.

CONCLUSION

Results of our study confirmed that oxidative stress is one of the factors involved in the pathogenesis of thyroid-associated orbitopathy and the methyloprednisolone treatment is effective in reducing both clinical symptoms and oxidative stress in patients with this disease.

Is There Evidence for IGF1R-Stimulating Abs in Graves' Orbitopathy Pathogenesis?

In this review, we summarize the evidence against direct stimulation of insulin-like growth factor 1 receptors (IGF1Rs) by autoantibodies in Graves’ orbitopathy (GO) pathogenesis. We describe a model of thyroid-stimulating hormone (TSH) receptor (TSHR)/IGF1R crosstalk and present evidence that observations indicating IGF1R’s role in GO could be explained by this mechanism. We evaluate the evidence for and against IGF1R as a direct target of stimulating IGF1R antibodies (IGF1RAbs) and conclude that GO pathogenesis does not involve directly stimulating IGF1RAbs. We further conclude that the preponderance of evidence supports TSHR as the direct and only target of stimulating autoantibodies in GO and maintain that the TSHR should remain a major target for further development of a medical therapy for GO in concert with drugs that target TSHR/IGF1R crosstalk.

Teprotumumab for the treatment of thyroid eye disease

INTRODUCTION

Thyroid eye disease is a debilitating, disfiguring, and potentially blinding periocular condition. Teprotumumab is a human insulin-like growth factor-I receptor monoclonal inhibitor antibody which indicated for treating thyroid eye disease.

AREAS COVERED

The authors performed a systematic review of the literature using the PubMed database, and the following keywords were used: 'teprotumumab,' 'thyroid eye disease,' and 'insulin-like growth factor I receptor.' The chemical property, mechanism of action, pharmacokinetics, clinical efficacy, and safety of teprotumumab were introduced in this paper.

EXPERT OPINION

Teprotumumab is a human monoclonal antibody targeting insulin-like growth factor-I receptor. Clinical trials indicated that proptosis response of teprotumumab was 83%, and clinical activity score, diplopia, and quality of life were also better than placebo. Teprotumumab was well tolerated, common adverse reactions included muscle spasm, nausea, alopecia, diarrhea, fatigue, hyperglycemia, hearing impairment, dysgeusia, headache, and dry skin.

TSH/IGF1 receptor crosstalk: Mechanism and clinical implications

Increasing evidence of interdependence between G protein-coupled receptors and receptor tyrosine kinase signaling pathways has prompted reevaluation of crosstalk between these receptors in disease and therapy. Investigations into thyroid-stimulating hormone (TSH) and insulin-like growth factor 1 (IGF1) receptor crosstalk, and its application to the clinic have in particular shown recent progress. In this review, we summarize current insights into the mechanism of TSH/IGF1 receptor crosstalk. We discuss evidence that crosstalk is one of the underlying causes of TSHR-based disease and the feasibility of using combinations of TSH receptor and IGF1 receptor antagonists to increase the therapeutic index for the treatment of Graves' hyperthyroidism and Graves' ophthalmopathy.

Fibrosis in dysthyroid eye disease

Dysthyroid eye disease is a rare condition, mainly found in people with Graves' hyperthyroidism. Autoimmune responses to thyroid/orbit shared antigens drive extensive tissue remodelling. This includes excess adipogenesis and over-production of extra-cellular matrix, which both tend to occur in the earlier 'active' inflammatory stages of disease. With time these give way to fibrosis, which has a profound impact on eye motility and may be life-long. Progress has been made in identifying the shared autoantigen(s) and the role of specific T cells and autoantibodies in remodelling, which have facilitated development of novel therapies. However relatively little is known of the autoimmune processes under-pinning fibrosis and currently there are no adequate medical treatments.

New insights into the pathogenesis and nonsurgical management of Graves orbitopathy

Graves orbitopathy, also known as thyroid eye disease or thyroid-associated orbitopathy, is visually disabling, cosmetically disfiguring and has a substantial negative impact on a patient's quality of life. There is increasing awareness of the need for early diagnosis and rapid specialist input from endocrinologists and ophthalmologists. Glucocorticoids are the mainstay of treatment; however, recurrence occurs frequently once these are withdrawn. Furthermore, in >60% of cases, normal orbital anatomy is not restored, and skilled rehabilitative surgery is required. Clinical trials have shown that considerable benefit can be derived from the addition of antiproliferative agents (such as mycophenolate or azathioprine) in preventing deterioration after steroid cessation. In addition, targeted biologic therapies have shown promise, including teprotumumab, which reduces proptosis, rituximab (anti-CD20), which reduces inflammation, and tocilizumab, which potentially benefits both of these parameters. Other strategies such as orbital radiotherapy have had their widespread role in combination therapy called into question. The pathophysiology of Graves orbitopathy has also been revised with identification of new potential therapeutic targets. In this Review we provide an up-to-date overview of the field, outline the optimal management of Graves orbitopathy and summarize the research developments in this area to highlight future research questions and direct future clinical trials.

4-Methylumbelliferone suppresses hyaluronan and adipogenesis in primary cultured orbital fibroblasts from Graves' orbitopathy

PURPOSE

In Graves' orbitopathy (GO), hyaluronan secreted by orbital fibroblasts contributes to orbital tissue expansion. The goal of this research was to evaluate the potential benefit of 4-methylumbelliferone (4-MU), a hyaluronan synthase (HAS) inhibitor, in primary cultured orbital fibroblasts from Graves' orbitopathy.

METHODS

We assessed the viability of orbital fibroblasts using a live/dead cell assay. Hyaluronan synthesis was evaluated by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time PCR (qPCR). Adipogenesis was assessed by Oil Red O staining and qPCR of adipogenic transcription factors.

RESULTS

In orbital fibroblasts treated with 4-MU (up to 1000 μM), cell viability was preserved by 90%. 4-MU significantly inhibited HAS gene expression and hyaluronan production (*P < 0.05). With respect to adipogenesis, 4-MU suppressed the accumulation of lipids and reduced the number of adipocytes, while decreasing expression of adipogenic transcription factors.

CONCLUSIONS

4-MU represents a promising new therapeutic agent for GO based on its ability to inhibit hyaluronan production and adipogenesis, without decreasing cell viability.

β-Arrestin 1 in Thyrotropin Receptor Signaling in Bone: Studies in Osteoblast-Like Cells

A direct action of thyrotropin (TSH, thyroid-stimulating hormone) on bone precursors in humans is controversial. Studies in rodent models have provided conflicting findings. We used cells derived from a moderately differentiated osteosarcoma stably overexpressing human TSH receptors (TSHRs) as a model of osteoblast precursors (U2OS-TSHR cells) to investigate TSHR-mediated effects in bone differentiation in human cells. We review our findings that (1) TSHR couples to several different G proteins to induce upregulation of genes associated with osteoblast activity-interleukin 11 (IL-11), osteopontin (OPN), and alkaline phosphatase (ALPL) and that the kinetics of the induction and the G protein-mediated signaling pathways involved were different for these genes; (2) TSH can stimulate β-arrestin-mediated signal transduction and that β-arrestin 1 in part mediates TSH-induced pre-osteoblast differentiation; and (3) TSHR/insulin-like growth factor 1 (IGF1) receptor (IGF1R) synergistically increased OPN secretion by TSH and IGF1 and that this crosstalk was mediated by physical association of these receptors in a signaling complex that uses β-arrestin 1 as a scaffold. These findings were complemented using a novel β-arrestin 1-biased agonist of TSHR. We conclude that TSHR can signal via several transduction pathways leading to differentiation of this model system of human pre-osteoblast cells and, therefore, that TSH can directly regulate these bone cells.

Current Understanding of the Progression and Management of Thyroid Associated Orbitopathy: A Systematic Review

Thyroid associated orbitopathy (TAO) is a common diagnosis encountered by ophthalmologists and oculoplastic surgeons. TAO has a varying clinical presentation that can include upper eyelid retraction, restrictive strabismus, proptosis, exposure keratopathy, and optic neuropathy. In this review, we discuss the most recent literature on and the current understanding of the pathophysiology of TAO. We also review available and potential future treatment options for the management of TAO.

A New Era in the Treatment of Thyroid Eye Disease

PURPOSE

Improved understanding of thyroid eye disease (TED) pathogenesis has facilitated identification of a targeted molecular approach for TED treatment offering the potential to halt or slow disease progression in a nonsurgical manner. Herein, we provide a summary of the current knowledge of TED management, followed by discussion of a novel insulin-like growth factor-1 receptor (IGF-1R) antagonist antibody and its potential to change the course of the disease.

DESIGN

Perspective.

METHODS

Review of the literature and authors' experience.

RESULTS

Many publications demonstrate IGF-1R overexpression in TED, and its activation as an autoantigen as a critical factor in TED pathogenesis. Several in vitro studies demonstrate that IGF-1R inhibition attenuates downstream molecular events including cytokine and hyaluronan production, and cellular differentiation. These observations led to the hypothesis that blocking IGF-1R may abrogate the clinical progression of TED. The recent completion of phase 2 and 3 randomized, placebo-controlled trials demonstrate the efficacy and safety of teprotumumab, a fully human monoclonal IGF-1R antagonist antibody, in patients with moderate-to-severe, active TED. Both the phase 2 and the recent phase 3 study results demonstrate that more patients with active TED receiving teprotumumab experienced a meaningful improvement in proptosis.

CONCLUSIONS

Current TED treatment strategies target inflammation and symptoms, but do not modify the disease course. Therefore, proptosis as well as strabismus and its resulting diplopia often remain, impacting patient well-being and quality of life over the long term. Targeted molecular therapy using teprotumumab demonstrates disease-modifying benefits with the potential to shift the paradigm for TED treatment.

Thyroid Eye Disease: How A Novel Therapy May Change The Treatment Paradigm

Thyroid eye disease (TED) is a complex, debilitating autoimmune disease that causes orbital inflammation and tissue remodeling, resulting in proptosis, diplopia, and in severe cases, loss of vision. TED can lead to facial disfigurement and severely impact patients’ quality of life. Although the course of TED was identified over 60 years ago, effective treatment options have proved to be challenging. Current treatments such as glucocorticoid therapy and orbital radiation focus on reducing orbital inflammation. However, these therapies fail to modify the disease outcomes, including proptosis and diplopia. Recent advances in the understanding of the molecular basis of TED have facilitated the development of targeted molecular therapies such as teprotumumab, an insulin-like growth factor-1 receptor inhibiting monoclonal antibody. In recent phase 2 and phase 3 randomized placebo-controlled trials, teprotumumab rapidly achieved improvement in clinical endpoints defining TED, including improved proptosis and diplopia. Dramatic improvement in clinical outcomes achieved after teprotumumab therapy during active TED are heretofore singular and comparable only to surgical therapies achieved during the inactive phase of TED. The advent of effective medical therapy can lead to a paradigm shift in the clinical management of TED. This review will provide an overview of TED, its epidemiology, insight into the molecular biology of the disease, clinical characteristics and diagnosis, and current and emerging treatment modalities.