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

Abstract

IntroductionGraves’ 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.MethodsLinsitinib 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.ResultsLinsitinib 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.ConclusionHere, 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.

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

“…Thus, we obtained bone marrow samples from each 10 BALB/c mice that were (i) immunized with the A-subunit of the TSHR and not further treated, (ii) immunized and treated with linsitinib or that were (iii) control-immunized with non-immunogenic ß-Gal and not further treated. Development of TED and changes in the orbit in these mice has been previously reported ( 18 ). These studies demonstrated that 90% of the mice that were immunized with TSHR developed TED.…”

“…Mice were immunized as described below at an age of 6 weeks. We employed three groups of mice ( 18 ), i.e. healthy control mice immunized with non-immunogenic ß-Gal (n=10), TSHR immunized mice (n=10) and TSHR immunized mice that were treated with linsitinib (n=10).…”

“…Linsitinib reduced the incidence of TED and only 10% of the mice that were immunized + treated with linsitinib developed TED. Specifically from our 28 mice used in this study, we had 8 ß-Gal mice (all healthy, none of them developed TED), 10 TSHR immunized mice not treated with linsitinib (9/10 mice developed TED) and 10 TSHR immunized mice treated with linsitinib (1/10 mice developed TED) ( 18 ). We followed the mice for 12 weeks.…”

“…We have recently demonstrated that linsitinib, also known as OSI-906, a selective small-molecule dual inhibitor of the insulin like growth factor 1 receptor (IGF-1R) and insulin receptor (IR) ( 17 ), has a marked beneficial effect on the outcome of experimental TED ( 18 ). Linsitinib blocked the development and progression of the local pathologies of GD and TED in an early and late phase of the autoimmune disorder in target tissues and also downregulated the inflammation in the orbital tissue, indicating the clinical significance of our findings.…”

Transcriptomic Profiling of Thyroid Eye Disease Orbital Fat Demonstrates Differences in Adipogenicity and IGF-1R Pathway

“…This pattern prompted us to investigate the effects of manipulating the IGF-1 pathway on adipogenesis in orbital fibroblasts. We utilized linsitinib, a small molecule IGF-1R antagonist, which diminishes immune infiltration and fibrosis in the orbit in TED animal models (41). Currently, linsitinib is undergoing Phase 2 clinical trials as a potential oral therapy for TED.…”