CAR-T cells Targeting Thyroid-stimulating Hormone Receptor (TSHR) Demonstrate Safety and Potent Preclinical Activity Against Differentiated Thyroid Cancer

Abstract Background: Differentiated thyroid cancer (DTC) is usually very treatable and is often cured with surgery and, if indicated, follow with radioactive iodine (RAI) and long-term thyroid-stimulating hormone (TSH) suppression with levothyroxine. Unfortunately, locoregional relapse and distant metastases occur in up to 20% at ten years; those relapsed or distant metastatic thyroid cancer is relatively uncommon compare to other cancers, cytotoxic chemotherapies provided low response rates, and two-thirds of cases became RAI refractory (RAI-R). New therapy options for local-regional relapsed or distant metastases thyroid cancer are desperately needed. Chimeric antigen receptor T cells(CAR-T)have been demonstrated remarkable efficacy in hematological cancers but have not yet translated in treating solid tumors. The significant hurdles limiting CAR-T therapy were due to a paucity of differentially expressed cell surface molecules on solid tumors that can be safely targeted. Here, we present thyroid-stimulating hormone receptor (TSHR) as a putative target for CAR-T therapy of DTC. Methods: We undertook a large-scale screen on thyroid cancer tissues and multiple internal organs through bioinformatical analysis and immunohistochemistry to date TSHR expression. Using three previously described mAb, we generate three third-generation CAR-Ts. We tested anti-TSHR CAR-T in vitro activity by T-cell function assay and killing assay. Then we tested pre-clinical therapeutical efficacy in a xenograft mouse model of DTC and analyzed mice's physical conditions and histological abnormalities to evaluate anti-TSHR CAR-T's safety. Results: TSHR is highly and homogeneously expressed on 90.8%(138/152) of papillary thyroid cancer, 89.2% (33/37) of follicular thyroid cancer, 78.2% (18/23) of the cervical lymph node metastases, and 86.7% of locally recurrent or metastasis lesions with RAI-R disease. We develop three novel anti-TSHR CAR-T from mAb M22, K1-18, and K1-70; all three CAR-Ts mediate significant anti-tumor activity in vitro. Among these, we demonstrate that K1-70 CAR-T can have therapeutical efficacy in vivo, and no apparent toxicity has been observed. Conclusion: TSHR is a latent target antigen of CAR-T therapy for DTC. Anti-TSHR CAR-T has strong therapeutical efficacy in vivo while without prominent adverse events. Anti-TSHR CAR-T could represent an exciting therapeutic option for patients with specific local-regional relapsed or distant metastases thyroid cancer and should be tested in carefully designed clinical trials.