Thyroid Toxicity Following Immune Checkpoint Inhibitor Treatment in Advanced Cancer

Factors associated with immune-related thyroid dysfunction induced by PD-1/PD-L1 inhibitors in cancer patients: an observational study

This study aimed to identify the potential factors associated with immune thyroid dysfunction caused by programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibitors in cancer patients. We conducted a retrospective study of thyroid immune-related adverse events (irAEs) in cancer patients treated with PD-1/PD-L1 inhibitors at Tianjin First Central Hospital from January 2020 to March 2023. Thyroid irAEs were characterized as hypothyroidism, hyperthyroidism and thyrotoxicosis followed by hypothyroidism. A total of 175 patients were screened in the study, of whom 48 patients (27%) developed thyroid irAEs (including 24 hypothyroidism, 11 hyperthyroidism and 13 thyrotoxicosis followed by hypothyroidism) following PD-1/PD-L1 inhibitors treatment. Multivariate logistic regression analysis showed that combination therapy with PD-1/PD-L1 inhibitors and tyrosine kinase inhibitors (lenvatinib/regorafenib) and high baseline anti-TPO level were associated with the development of thyroid irAEs caused by PD-1/PD-L1 inhibitors. The nomogram models showed good discriminant ability and could bring net benefits for more patients according to the decision curve analysis. However, the model needs to be further validated in other large cohorts.

Immune-Related Adverse Events Induced by Immune Checkpoint Inhibitors and CAR-T Cell Therapy: A Comprehensive Imaging-Based Review

Immunotherapy has revolutionized oncology care, improving patient outcomes in several cancers. However, these therapies are also associated with typical immune-related adverse events due to the enhanced inflammatory and immune response. These toxicities can arise at any time during treatment but are more frequent within the first few months. Any organ and tissue can be affected, ranging from mild to life-threatening. While some manifestations are common and more often mild, such as dermatitis and colitis, others are rarer and more severe, such as myocarditis. Management depends on the severity, with treatment being held for >grade 2 toxicities. Steroids are used in more severe cases, and immunosuppressive treatment may be considered for non-responsive toxicities, along with specific organ support. A multidisciplinary approach is mandatory for prompt identification and management. The diagnosis is primarily of exclusion. It often relies on imaging features, and, when possible, cytologic and/or pathological analyses are performed for confirmation. In case of clinical suspicion, imaging is required to assess the presence, extent, and features of abnormalities and to evoke and rule out differential diagnoses. This imaging-based review illustrates the diverse system-specific toxicities associated with immune checkpoint inhibitors and chimeric antigen receptor T-cells with a multidisciplinary perspective. Clinical characteristics, imaging features, cytological and histological patterns, as well as the management approach, are presented with insights into radiological tips to distinguish these toxicities from the most important differential diagnoses and mimickers-including tumor progression, pseudoprogression, inflammation, and infection-to guide imaging and clinical specialists in the pathway of diagnosing immune-related adverse events.

For the Long Haul: Management of Long-Term Survivors after Melanoma Systemic Therapy

PURPOSE OF REVIEW

This review summarizes the latest advancements in survivorship care for patients with advanced melanoma who received systemic therapy and emphasizes the areas where more research is needed.

RECENT FINDINGS

Over the last decade there have been remarkable advances in the treatment of advanced and metastatic melanoma. Due to these novel treatments, including several immune checkpoint inhibitors and tyrosine kinase inhibitors, there are and will continue to be increasing numbers of long-term melanoma survivors who have been treated with systemic therapy. These patients will navigate new challenges are they are essentially among the first long term survivors after these novel therapies. Survivorship care focuses on improving the health-related quality of life of patients including the physical, emotional, social and functional effects of cancer that begin at diagnosis and continue through the end of life. Survivorship also includes screening for cancer recurrence and second cancers. As the number of melanoma survivors who received systemic therapy continues to grow, the survivorship care plan will become increasingly important for optimal care of patients even after their cancer treatments. Understanding the many domains of survivorship care for this group of patients is imperative for their care now and to identify unmet needs for future research.

Thyroid disorders induced by immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) are a revolutionary class of drugs that powerfully contribute to cancer therapy by harnessing the immune system to fight malignancies. However, their successful use as anti-cancer drugs is accompanied by a wide spectrum of immune-related adverse effects (irAEs), including endocrinopathies. Among them, thyroid dysfunction stands out as one of the most common endocrinopathies induced by ICI therapy and surfaces as a prominent concern. Destructive thyroiditis is the pathophysiological basis shared by the most common patterns of thyrotoxicosis followed by hypothyroidism and isolated hypothyroidism. Diagnostic approach is guided by clinical manifestation, laboratory evaluation and imaging modalities. Treatment approaches range from the substitution of levothyroxine to the utilization of beta blockers, depending on the extent of thyroid dysfunction's severity. While the medical community is dealing with the evolution and complexities of immunotherapy, recognizing and effectively managing ICI-induced thyroid dysfunction emerged as crucial for enhancing patient safety and achieving improved outcomes. The aim of this review is to navigate the significance of ICI-induced thyroid dysfunction unraveling the various patterns, underlying mechanisms, diagnostic approaches, and treatment strategies. It, also, highlights the impact of various factors such as cancer subtype, ICI dosage, age, and genetic susceptibility on the risk of experiencing dysfunction.

Clinical use of thyroglobulin: not only thyroid cancer

Thyroglobulin (TG) is a dimeric glycoprotein produced exclusively by mature thyroid tissue and stored within the follicular lumen. It is essential for the organification of iodine and the production of thyroid hormones. The concentration of TG in the bloodstream varies between individuals and depends on factors such as thyroid mass, stimulation of the gland by thyrotropin or autoantibodies, and tissue destruction. TG is essential to monitor patients with differentiated thyroid cancer; however, its use is not limited only to this clinical entity. Measurement of circulating TG can provide better insight into numerous clinical scenarios, such as destructive thyroiditis, presence of ectopic thyroid tissue, thyroid trauma, factitious thyrotoxicosis, or iodine nutrition. Lately, TG has found its new clinical use in immune checkpoint-related thyroid dysfunction. TG measurement should be performed carefully in patients with antithyroglobulin antibodies due to possible laboratory interferences. In this review, we offer a summary of current knowledge about the clinical use of TG and the implications it brings to daily practice.

Clinical biomarkers for thyroid immune-related adverse events in patients with stage III and IV gastrointestinal tumors

Background

Thyroid immune-related adverse events (irAEs) associated with immune checkpoint inhibitor (ICI) treatment appear to correlate with a better prognosis. We aimed to investigate clinical biomarkers associated with thyroid irAEs.

Methods

We retrospectively analyzed data from 129 patients receiving programmed cell death protein 1 (PD-1) inhibitors for stage III and IV gastrointestinal tumors. Patients were divided into two groups: "thyroid irAEs" group and "no thyroid irAEs" group. We compared continuous variables using Mann-Whitney U and Kruskal-Wallis tests and categorical variables using Pearson's chi-square test. Survival curves were generated using the Kaplan-Meier method, and associations between clinical features and thyroid irAEs were assessed using univariate and multivariate logistic regression models. Associations for thyroid irAEs and outcomes [progression-free survival (PFS), overall survival (OS)] of the patients were performed with a Cox proportional hazard model.

Results

A total of 129 patients, including 66 gastric cancer, 30 esophageal squamous cell carcinoma, and 33 hepatocellular carcinoma (HCC), were involved in this analysis with 47 cases of thyroid irAEs occurrence. The Cox proportional hazard model analysis confirmed the extended PFS [hazard rate (HR) = 0.447, 95% confidence interval (CI): 0.215 to 0.931, p = 0.031] and OS (HR = 0.424, 95% CI: 0.201 to 0.893, p = 0.024) for thyroid irAEs group when compared with those of the no thyroid irAEs group. Association between thyroid irAEs and clinical characteristics at baseline was analyzed subsequently by univariate analysis. Higher body mass index (p = 0.005), increased eosinophil count (p = 0.014), increased lactate dehydrogenase (p = 0.008), higher baseline thyroid stimulating hormone (TSH) (p = 0.001), HCC (p = 0.001) and increased adenosine deaminase (ADA) (p = 0.001) were linked with thyroid irAEs occurrence. The multivariable logistic regression model indicated that ADA [odds rate (OR) = 4.756, 95% CI: 1.147 to 19.729, p = 0.032] was independently associated with thyroid irAEs occurrence.

Conclusions

Increased baseline level of ADA was associated with thyroid irAEs occurrence in patients with advanced gastrointestinal tumors who received ICI treatment. In the case of abnormal ADA, attention should be paid to the risk of thyroid irAEs.

Frequency and characteristics of immune-related thyroid adverse events in patients with resected stage III/IV melanoma treated with adjuvant PD-1 inhibitors: a national cohort study

PURPOSE

Immune-related thyroid adverse events (irTAEs) occur frequently following immune checkpoint inhibitor (ICI) therapy. The purpose of this study is to provide knowledge about the incidence, clinical timeline characteristics, associated factors of irTAEs, and potential impact on treatment efficacy in patients with melanoma receiving adjuvant ICI therapy.

METHODS

A national multicenter retrospective cohort study of patients with resected stage III/IV melanoma treated with adjuvant PD-1 inhibitors between November 2018 and December 2020. Data were extracted from the Danish Metastatic Melanoma Database. The irTAEs were defined as two consecutive abnormal TSH values and subdivided into transient or persistent.

RESULTS

Of 454 patients, 99 developed an irTAE (21.8%), of these were 46 transient (46.5%) and 53 persistent (53.5%). Median time to transient and persistent irTAE was 55 and 44 days, respectively (p = 0.57). A hyperthyroid phase followed by hypothyroidism was seen in 73.6% of persistent irTAEs, whereas 87% of transient irTAEs developed an isolated hypo- or hyperthyroid phase. Multiple variable analysis demonstrated an association between irTAE and female sex (HR 2.45; 95% CI 1.63-3.70; p < 0.001), but no association with recurrence-free survival (HR 0.86; 95% CI 0.50-1.48; p = 0.587) or overall survival (HR 1.05; 95% CI 0.52-2.12, p = 0.891).

CONCLUSIONS

IrTAE is a common side effect to PD-1 inhibitors primarily occurring within the first 3 months, with a high risk of persistency. Female sex is a strong predictive factor. IrTAE was not associated with improved clinical outcome.

Hyperthyroidism

Thyrotoxicosis causes a variety of symptoms and adverse health outcomes. Hyperthyroidism refers to increased thyroid hormone synthesis and secretion, most commonly from Graves' disease or toxic nodular goitre, whereas thyroiditis (typically autoimmune, viral, or drug induced) causes thyrotoxicosis without hyperthyroidism. The diagnosis is based on suppressed serum concentrations of thyroid-stimulating hormone (TSH), accompanied by free thyroxine and total or free tri-iodothyronine concentrations, which are raised (overt hyperthyroidism) or within range (subclinical hyperthyroidism). The underlying cause is determined by clinical assessment, detection of TSH-receptor antibodies and, if necessary, radionuclide thyroid scintigraphy. Treatment options for hyperthyroidism include antithyroid drugs, radioactive iodine, and thyroidectomy, whereas thyroiditis is managed symptomatically or with glucocorticoid therapy. In Graves' disease, first-line treatment is a 12-18-month course of antithyroid drugs, whereas for goitre, radioactive iodine or surgery are preferred for toxic nodules or goitres. Evidence also supports long-term treatment with antithyroid drugs as an option for patients with Graves' disease and toxic nodular goitre.

Achilles' Heel of currently approved immune checkpoint inhibitors: immune related adverse events

Immunotherapy has revolutionized the cancer treatment landscape by opening up novel avenues for intervention. As the use of immune checkpoint inhibitors (ICIs) has exponentially increased, so have immune-related adverse events (irAEs). The mechanism of irAEs may involve the direct damage caused by monoclonal antibodies and a sequence of immune responses triggered by T cell activation. Common side effects include dermatologic toxicity, endocrine toxicity, gastrointestinal toxicity, and hepatic toxicity. While relatively rare, neurotoxicity, cardiotoxicity, and pulmonary toxicity can be fatal. These toxicities pose a clinical dilemma regarding treatment discontinuation since they can result in severe complications and necessitate frequent hospitalization. Vigilant monitoring of irAEs is vital in clinical practice, and the principal therapeutic strategy entails the administration of oral or intravenous glucocorticoids (GSCs). It may be necessary to temporarily or permanently discontinue the use of ICIs in severe cases. Given that irAEs can impact multiple organs and require diverse treatment approaches, the involvement of a multidisciplinary team of experts is imperative. This review aims to comprehensively examine the pathogenesis, clinical manifestations, incidence, and treatment options for various irAEs.

Replacement Dose for Overt Hypothyroidism Induced by Programmed Cell Death Protein 1 Antibodies May Be Higher than Recommended

BACKGROUND

The present recommendations, consensus, or guidelines for the replacement dosage for hypothyroidism induced by programmed cell death protein 1 (PD-1) therapy are not uniform, and there are very few special clinical trials that have examined the replacement dosage for it.

OBJECTIVES

This article illustrates the clinical characteristics of hypothyroidism induced by PD-1 antibodies (Abs) and reports the recommended replacement dosage for hypothyroidism.

METHODS

Eighteen patients with overt primary hypothyroidism induced by PD-1 Abs (group 1) were selected from 655 patients with different tumor types. Retrospective analysis was performed on patients in group 1 and 18 patients with natural courses of overt primary hypothyroidism who were age- and sex-matched with the patients in group 1 (group 2). The replacement dosages required for the patients in the two groups were compared.

RESULTS

Thyroid dysfunction occurred in group 1 after approximately 3.0 ± 1.4 cycles of PD-1 therapy (1-6 stages), with a median time of 61.5 days. The median time of onset of hypothyroidism among all patients was 87.5 days (30-240 days). Most of the patients with hypothyroidism were asymptomatic, and the onset of hypothyroidism was independent of age, sex, TPOAb, TgAb and TSH in group 1 (P>0.05). The average replacement dosage for patients in group 1 was 1.8 ± 0.6 μg/kg/d (0.6-3.2 μg/kg/d). Multiple linear regression analysis showed that sex, age, TPOAb, TgAb and TSH were not correlated with drug dosage.

CONCLUSION

It seemed that the average maintenance dosage of levothyroxine might need to be 1.8 μg/kg/day for patients with overt hypothyroidism induced by PD-1 Abs.

Safety and efficacy of immune checkpoint inhibitor cancer therapy in patients with preexisting type 1 diabetes mellitus

Introduction

Immune checkpoint inhibitors (ICI) produce dramatic tumor shrinkage and durable responses in many advanced malignancies, but their use is limited by the development of immune-related adverse events (IRAEs) that occur in up to 60% of patients and often affect endocrine organs. Concern for more severe IRAEs in patients with preexisting autoimmune diseases, including type 1 diabetes mellitus (T1DM), has led to the exclusion of such individuals from clinical trials of ICI therapy. As a result, little is known about the safety and efficacy of ICI in this population. Here, we report safety and treatments outcomes in ICI-treated patients with preexisting T1DM.

Methods

This retrospective case-controlled study evaluated adult patients with T1DM who received ICI therapy for solid malignancies from 2015 to 2021 at four academic medical centers. Patients with prior ICI therapy, bone marrow transplantation, or pregnancy were excluded. We collected data on demographics, cancer diagnosis and treatment, IRAE incidence and severity, and diabetes management. Controls were matched 2:1 by age, sex, cancer diagnosis, and ICI therapy class.

Results

Of 12,142 cancer patients treated with ICI therapy, we identified 11 with a preexisting confirmed diagnosis of T1DM prior to starting ICI therapy. Mean age was 50.6 years, 63.6% were women, and most received anti-PD1/PDL1 monotherapy (10/11) compared with combination therapy (1/11). Grade 3/4 IRAEs were seen in 3/11 subjects with preexisting T1DM and were hepatitis, myositis, and myasthenia gravis. All three cases had interruption of ICI therapy and administration of adjunct therapies, including steroids, IVIG, or mycophenolate mofetil with resolution of the IRAE. The odds of all-grade IRAEs and of severe IRAEs were comparable between cases and controls matched for age, sex, cancer type, and ICI therapy [OR 0.83 (95% CI 0.2-3.56), p = 0.81, and OR 1.69 (0.31-9.36), p = 0.55, respectively]. Overall survival was not different between patients with T1DM and controls (p = 0.54). No patients had hospitalizations for diabetes-related complications during therapy.

Discussion

These data suggest that ICI monotherapy can successfully be used in patients with preexisting T1DM, with IRAE rates comparable with individuals without preexisting T1DM. Larger, prospective studies of these potentially life-saving ICI therapies that include patients with preexisting autoimmunity are warranted.

Clinical Characters and Influence Factors of Immune Checkpoint Inhibitor-related Thyroid Dysfunction

CONTEXT

Explore the clinical characteristics and influencing factors of immune thyroid dysfunction (ITD) caused by immune checkpoint inhibitors (ICIs) in the treatment of malignant tumors.

METHODS

This was a retrospective study of cancer patients treated with ICIs between January 2019 and December 2021 at the Second Affiliated Hospital of Nanchang University. According to the occurrence of thyroid dysfunction, patients were divided into an ITD group and non-ITD group. We describe the clinical characteristics, autoantibody levels, and their impact on prognosis of patients with ICI-related ITD.

RESULT

A total of 560 cases meeting the criteria were included, with a median follow-up time of 11.0 months. The incidence of ITD was 50.7%. Baseline TSH levels (OR, 1.935/mcIU/L; 95% CI, 1.613-2.321; P < .001) and combination targeted therapy (OR, 2.101; 95% CI, 1.433-3.079; P < .001) were most strongly associated with the occurrence of ITD. The median time to ITD in patients receiving medication with ICIs was 73 (34.5-149) days. Of the 87 patients initially diagnosed with hyperthyroid ITD, 46 (52.9%) progressed to hypothyroidism over the course of the disease. Baseline anti-thyroglobulin antibody abnormalities were strongly associated with the occurrence of ITD (OR, 67.393; 95% CI, 5.637-805.656; P = .001). Overall survival was significantly lower in patients who did not develop ITD than in those who did (hazard ratio, 0.523; 95% CI, 0.599-0.97; P < .001).

CONCLUSION

The incidence of ICI-related ITD is high, and the course of the disease is rapidly changing, and thyroid function in patients treated with immunotherapy should be monitored to detect ITD and permit early intervention.

Risk of Thyroid Dysfunction in PD-1 Blockade Is Stratified by the Pattern of TgAb and TPOAb Positivity at Baseline

CONTEXT

Positive antithyroglobulin (TgAb) and/or antithyroid peroxidase antibodies (TPOAb) at baseline indicate a high risk of thyroid immune-related adverse events (irAEs) induced by antiprogrammed cell death-1 antibodies (anti-PD-1-Ab). However, whether the positivity patterns of both antibodies are associated with the risk of thyroid irAEs is unknown.

OBJECTIVE

The aim of the present study was to clarify the association of the pattern of TgAb and TPOAb positivity at baseline with the risk of thyroid irAEs induced by anti-PD-1-Ab.

METHODS

Patients (n = 516) were evaluated for TgAb and TPOAb at baseline and prospectively for thyroid function every 6 weeks for 24 weeks after initiating anti-PD-1-Ab.

RESULTS

Fifty-one (9.9%) patients developed thyroid irAEs (thyrotoxicosis in 34, hypothyroidism without prior thyrotoxicosis in 17). Twenty-five patients subsequently developed hypothyroidism following thyrotoxicosis. The cumulative incidence of thyroid irAEs differed among 4 groups classified by the presence of TgAb/TPOAb at baseline (group 1: TgAb-(-)/TPOAb-(-), 4.6% [19/415]; group 2: TgAb-(-)/TPOAb-(+), 15.8% [9/57]; group 3: TgAb-(+)/TPOAb-(-), 42.1% [8/19]; group 4: TgAb-(+)/TPOAb-(+), 60.0% [15/25]) as follows: groups 1 vs 2-4 (P ≤ .001) and groups 2 vs 3 (P = .008) and 4 (P < .001). There were different incidences of thyrotoxicosis (groups 1-4, 3.1%, 5.3%, 31.6%, 48.0%, respectively; P < .001) in groups 1 vs 3 and 4, and groups 2 vs 3 and 4, and of hypothyroidism (groups 1-4: 2.9%, 15.8%, 31.6%, 60.0%, respectively; P < .001) in groups 1 vs 2 to 4, and groups 2 vs 4.

CONCLUSION

The risk of thyroid irAEs was affected by the pattern of TgAb and TPOAb positivity at baseline; there were high risks of thyrotoxicosis in patients with TgAb-(+) and of hypothyroidism in patients with TgAb-(+) and those with TPOAb-(+).

Endocrine Side Effects in Patients Treated with Immune Checkpoint Inhibitors: A Narrative Review

Checkpoint inhibitors are monoclonal antibodies that elicit an anti-tumor response by stimulating immune system. Their use has improved the treatment of different types of cancer such as melanoma, breast carcinoma, lung, stomach, colon, liver, renal cell carcinoma, and Hodgkin's lymphoma, but several adverse events have been reported. Although the etiology of these effects is not completely understood, an uncontrolled activation of the immune system has been postulated. Indeed, some studies showed a cross reactivity of T cells, which acted against tumor antigens as well as antigens in the tissues of patients who developed immune-related adverse events. Despite the known possibility of developing immune-related adverse events, early diagnosis, monitoring during therapy, and treatment are fundamental for the best supportive care and administration of immune checkpoint inhibitors. The aim of this review is to guide the clinician in early diagnosis, management, and treatment of the endocrinological adverse effects in the major endocrine glands (thyroid, pituitary, adrenal, endocrine pancreas, and parathyroid).

Levothyroxine Dosing in Older Adults: Recommendations Derived From The Baltimore Longitudinal Study of Aging

OBJECTIVE

As thyroid hormone metabolism slows with advancing age, treatment dosing requirements change. Guidelines recommend titration from a low starting dose for older adults with hypothyroidism while providing weight-based estimates for younger populations. However, rapid replacement may be appropriate with acute onset of overt hypothyroidism. Therefore, a weight-based recommendation specific to older adults is needed.

METHODS

We determined mean levothyroxine dose using actual and ideal body weight (IBW) ratios for the outcome of euthyroid on therapy relative to assay-specific and proposed age-specific ranges for independently living participants aged ≥65 years in the Baltimore Longitudinal Study of Aging. We examined risk factors to identify those at highest risk of overtreatment using regression analyses adjusted for potential covariables and clustering to account for multiple visits per individual.

RESULTS

One hundred eighty-five participants aged ≥65 years were on levothyroxine at 645 eligible visits. At euthyroid visits, participants were on an average dose of 1.09 μg/kg (1.35 μg/kg IBW), with 84% of euthyroid individuals on a dose of <1.6 μg/kg. Average euthyroid dose did not differ by sex using either actual body weight (ABW) or IBW. For obese individuals, mean euthyroid dose was lower if calculated using ABW (0.9 μg/kg vs 1.14 μg/kg; P < .01) but similar if calculated using IBW (1.42 vs 1.32 μg/kg IBW; P = .41) compared with those with a body mass index of <30.

CONCLUSION

Thyroid hormone dose per body weight estimates for replacement in older adults (1.09 μg/kg ABW or 1.35 μg/kg IBW) are one-third lower than current weight-based dose recommendations for younger populations.

Immune checkpoint inhibitor-induced hypothyroidism predicts treatment response in Japanese subjects

Background

Immune checkpoint inhibitors (ICIs) cause a variety of immune-related adverse events (irAEs). Among them, thyroid dysfunction is most frequently observed. Patients with irAEs have higher survival rates than those without irAEs, but there is no certainty as to whether the degree of thyroid dysfunction is associated with treatment response or survival with ICIs.

Method

This is a single-center, retrospective, observational study. The study included 466 patients who received ICI at Kawasaki Medical School Hospital from September 1, 2014, to May 31, 2022 and evaluated the degree of abnormal thyroid function and survival and remission rates after treatment with ICIs. Primary hypothyroidism of less than 10 μIU/mL TSH was classified as grade 1, and primary hypothyroidism requiring more than 10 μIU/mL TSH or levothyroxine as grade 2-4.

Result

The mean age of the study participants was 68.2 ± 10.3 years, and the percentage of male participants was 72.6%. The frequency of ICI-induced thyroid dysfunction in the study participants was 28.2%. TSH levels were significantly higher in Grade 1 and Grades 2-4 when treated with ICI compared to NTF (p<0.0001). The survival rate at 1 year after ICI administration was significantly higher with 64.9% for grade 1 and 88.9% for grades 2-4 compared to 52.1% for NTF (p<0.0001). Cancer stage at the time of ICI administration did not differ among the groups (p=0.68). Nevertheless, the remission rate assessed by RECIST criteria was significantly higher in grades 2-4 compared to NTF (p<0.0001).

Conclusion

ICI-induced thyroid dysfunction was significantly correlated with survival, mean observation time, and treatment remission rate. It is important to monitor thyroid hormone levels regularly in patients receiving ICIs.

Thyroid dysfunction after immune checkpoint inhibitor treatment in a single-center Chinese cohort: a retrospective study

BACKGROUND

Thyroid dysfunction is a common adverse event after immune checkpoint inhibitor (ICI) therapy. The clinical manifestations of thyroid immune-related adverse events (irAEs) are variable and the underlying mechanisms remain unclear.

PURPOSE

To identify the clinical and biochemical characteristics of Chinese patients with ICI-related thyroid dysfunction.

METHODS

We retrospectively reviewed patients with carcinoma who received ICI therapy and underwent evaluation of thyroid function during hospitalization at Peking Union Medical College Hospital between January 1, 2017 and December 31, 2020. Clinical and biochemical features were analyzed in patients who developed ICI-related thyroid dysfunction. Survival analyses were performed to determine the effect of thyroid autoantibodies on thyroid abnormalities and the impact of thyroid irAEs on clinical outcomes.

RESULTS

The cohort included 270 patients with a median follow-up of 17.7 months; 120 (44%) of these patients developed thyroid dysfunction on immunotherapy. The most common thyroid irAE was overt hypothyroidism (with/without transient thyrotoxicosis), which occurred in 38% of patients (n = 45), followed by subclinical thyrotoxicosis (n = 42), subclinical hypothyroidism (n = 27), and isolated overt thyrotoxicosis (n = 6). The median time to first clinical presentation was 49 days (interquartile range 23, 93) for thyrotoxicosis and 98 days (interquartile range 51, 172) for hypothyroidism. In patients treated with PD-1 inhibitors, hypothyroidism was strongly associated with younger age (odds ratio [OR] 0.44, 95% confidence interval [CI] 0.29-0.67; P < 0.001), previous thyroid disease (OR 4.30, 95% CI 1.54-11.99; P = 0.005), and a higher baseline thyroid-stimulating hormone level (OR 2.76, 95% CI 1.80-4.23; P < 0.001). Thyrotoxicosis was only associated with the baseline thyroid-stimulating hormone (TSH) level (OR 0.59, 95% CI 0.37-0.94; P = 0.025). Thyroid dysfunction after initiation of ICI therapy was associated with better progression-free survival (hazard ratio [HR] 0.61, 95% CI 0.44-0.86; P = 0.005) and overall survival (hazard ratio 0.67, 95% CI 0.45-0.99; P = 0.046). Anti-thyroglobulin antibody positivity increased the risk of thyroid irAEs.

CONCLUSIONS

The occurrence of thyroid irAEs with diverse phenotypes is common. Distinct clinical and biochemical characteristics suggest heterogeneity among different subgroups of thyroid dysfunction, which requires further research to explore the under mechanism.

Baseline risk factors associated with immune related adverse events and atezolizumab

Background

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer patients in the last decade, but immune-related adverse events (irAEs) pose significant clinical challenges. Despite advances in the management of these unique toxicities, there remains an unmet need to further characterize the patient-level drivers of irAEs in order to optimize the benefit/risk balance in patients receiving cancer immunotherapy.

Methods

An individual-patient data post-hoc meta-analysis was performed using data from 10,344 patients across 15 Roche sponsored clinical trials with atezolizumab in five different solid tumor types to assess the association between baseline risk factors and the time to onset of irAE. In this study, the overall analysis was conducted by treatment arm, indication, toxicity grade and irAE type, and the study design considered confounder adjustment to assess potential differences in risk factor profiles.

Results

This analysis demonstrates that the safety profile of atezolizumab is generally consistent across indications in the 15 studies evaluated. In addition, our findings corroborate with prior reviews which suggest that reported rates of irAEs with PD-(L)1 inhibitors are nominally lower than CTLA-4 inhibitors. In our analysis, there were no remarkable differences in the distribution of toxicity grades between indications, but some indication-specific differences regarding the type of irAE were seen across treatment arms, where pneumonitis mainly occurred in lung cancer, and hypothyroidism and rash had a higher prevalence in advanced renal cell carcinoma compared to all other indications. Results showed consistency of risk factors across indications and by toxicity grade. The strongest and most consistent risk factors were mostly organ-specific such as elevated liver enzymes for hepatitis and thyroid stimulating hormone (TSH) for thyroid toxicities. Another strong but non-organ-specific risk factor was ethnicity, which was associated with rash, hepatitis and pneumonitis. Further understanding the impact of ethnicity on ICI associated irAEs is considered as an area for future research.

Conclusions

Overall, this analysis demonstrated that atezolizumab safety profile is consistent across indications, is clinically distinguishable from comparator regimens without checkpoint inhibition, and in line with literature, seems to suggest a nominally lower reported rates of irAEs vs CTLA-4 inhibitors. This analysis demonstrates several risk factors for irAEs by indication, severity and location of irAE, and by patient ethnicity. Additionally, several potential irAE risk factors that have been published to date, such as demographic factors, liver enzymes, TSH and blood cell counts, are assessed in this large-scale meta-analysis, providing a more consistent picture of their relevance. However, given the small effects size, changes to clinical management of irAEs associated with the use of Anti-PDL1 therapy are not warranted.

Preconditioning of the immune system modulates the response of papillary thyroid cancer to immune checkpoint inhibitors

BACKGROUND

The response of solid tumors such as papillary thyroid cancer (PTC) to immune checkpoint inhibitors (ICIs) is highly variable. The biological basis of this variability remains unknown.

METHODS

To test the hypothesis that preconditioning of the immune system modulates the therapeutic effect of ICIs, we used a murine model where PTC and iodine exacerbated thyroiditis (IET) can be induced in a temporally predictable fashion. A total of 122 mice were divided into 3 experimental groups. In the first one, named concomitant IET and PTC (No.=40), IET, and PTC were induced at the same time; in the second one, named pre-existing IET (No.=44), IET was induced prior to the induction of PTC; in the third one, named no IET (No.=38), only PTC was induced. Following disease induction, mice of each group were treated with anti-PD-1 antibody, anti-lymphocyte activation gene 3 antibody (anti-Lag3), anti-T-cell immunoglobulin and mucin domain 3 antibody (anti-Tim3), or IgG control. Ten weeks after the initial ICI injection, mice were sacrificed to collect the thyroid gland for histological analysis, to quantify the incidence and burden of PTC, and to perform high-throughput single-cell RNA sequencing of infiltrating CD45⁺ cells.

RESULTS

In the concomitant IET and PTC group, ICI treatment reduced PTC incidence (p=0.002 comparing treatment with any ICI vs control), while it had no effect in the pre-existing IET and no IET groups. Single-cell sequencing of thyroidal CD45⁺ cells showed that the different ICIs tested had both specific and shared effects on all the components of the thyroidal immune cell infiltrate. The shared effect of the tested ICIs was dependent on the presence of pre-existing versus concomitant IET. In the context of concomitant IET, ICI treatment resulted in the modulation of a greater number of pathways related to both innate and adaptive immunity.

CONCLUSIONS

Response to ICIs depends on the status of the immune system of the treated individual. Modulation of the immune system should be explored as a tool to improve response to ICIs in patients with PTC or other forms of cancer.

A Successful Case of Hepatocellular Carcinoma Treated with Atezolizumab Plus Bevacizumab with Multisystem Immune-related Adverse Events

A 63-year-old man with hepatitis C was treated with atezolizumab plus bevacizumab for unresectable diffuse hepatocellular carcinoma (HCC). After four cycles of atezolizumab plus bevacizumab, the diffuse HCC markedly shrank; however, he complained of general fatigue, loss of appetite, and slight loss of muscle strength in the lower legs. He was diagnosed with isolated adrenocorticotropic hormone deficiency (IAD), hypothyroidism, and myopathy, suggesting multisystem immune-related adverse events (irAEs). After administration of hydrocortisone, the clinical symptoms rapidly disappeared. Patients with multisystem irAEs can have favorable outcomes; thus, to continue immune-checkpoint inhibitors therapy, a correct diagnosis and management of multisystem irAEs are important.

The continuum of care of anticancer treatment-induced hypothyroidism in patients with solid non thyroid tumors: time for an intimate collaboration between oncologists and endocrinologists

INTRODUCTION

Hypothyroidism is a common adverse event of various anticancer treatment modalities, constituting a notable paradigm of the integration of the endocrine perspective into precision oncology.

AREAS COVERED

The present narrative review provides a comprehensive and updated overview of anticancer treatment-induced hypothyroidism in patients with solid non-thyroid tumors. A study search was conducted on the following electronic databases: PubMed, Google Scholar, Scopus.com, ClinicalTrials.gov, and European Union Clinical Trials Register from 2011 until August 2021.

EXPERT OPINION

In patients with solid non-thyroid tumors, hypothyroidism is a common adverse event of radiotherapy, high dose interleukin 2 (HD IL-2), interferon alpha (IFN-α), bexarotene, immune checkpoint inhibitors (ICPi), and tyrosine kinase inhibitors (TKIs), while chemotherapy may induce hypothyroidism more often than initially considered. The path forward for the management of anticancer treatment-induced hypothyroidism in patients with solid non-thyroid tumors is an integrated approach grounded on 5 pillars: prevention, vigilance, diagnosis, treatment and monitoring. Current challenges concerning anticancer treatment-induced hypothyroidism await counteraction, namely awareness of the growing list of related anticancer treatments, identification of predictive factors, counteraction of diagnostic pitfalls, tuning of thyroid hormone replacement, and elucidation of its prognostic significance. Close collaboration of oncologists with endocrinologists will provide optimal patient care.

Thyroid Dysfunction from Treatments for Solid Organ Cancers

In recent years, cancer care has been transformed by immune-based and targeted treatments. Although these treatments are effective against various solid organ malignancies, multiple adverse effects can occur, including thyroid dysfunction. In this review, the authors consider treatments for solid organ cancers that affect the thyroid, focusing on immune checkpoint inhibitors, kinase inhibitors, and radioactive iodine-conjugated treatments (I-131-metaiodobenzylguanidine). They discuss the mechanisms causing thyroid dysfunction, provide a framework for their diagnosis and management, and explore the association of thyroid dysfunction from these agents with patient survival.

Association of Antithyroid Antibodies in Checkpoint Inhibitor-Associated Thyroid Immune-Related Adverse Events

CONTEXT

The significance of thyroid peroxidase (TPOAb) and thyroglobulin antibody (TgAb) in the pathogenesis of thyroid immune-related adverse events (irAEs) is unknown.

OBJECTIVE

To characterize the association of anti-thyroid antibodies with the development of thyroid immune related adverse events.

METHODS

A retrospective cohort study was conducted of patients with melanoma receiving immune checkpoint inhibitor (ICI) treatment. TPOAb, TgAb, and interleukin-6 (IL-6) were measured retrospectively using tumor-banked samples at baseline and at time of diagnosis of a thyroid irAE. In euthyroid patients (without thyroid irAEs) measures were repeated 30 to 60 days after ICI commencement, which was similar to the median time to onset of thyroid irAEs in other patients.

RESULTS

A total of 122 patients were included-31 remained euthyroid, 47 developed subclinical thyrotoxicosis, 37 developed overt thyrotoxicosis, and 7 developed overt hypothyroidism without preceding thyrotoxicosis. Baseline elevation of TPOAb or TgAb was present in 19 (16%) and 28 (23%) patients, respectively. Positive TPOAb or TgAb at baseline was 97% and 100% specific for eventual development of a thyroid irAE, respectively. During ICI treatment, overt thyrotoxicosis, but not other subtypes of thyroid irAE, was associated with statistically significant increases in the titer of TgAb and TPOAb. Baseline IL-6 levels were not associated with thyroid irAE onset but statistically significantly increased during treatment in patients who developed overt hypothyroidism.

CONCLUSIONS

TPOAb and TgAb positivity at baseline was more prevalent in patients who developed thyroid irAEs. Statistically significant increases or new antibody positivity was observed in association with overt thyrotoxicosis. TPOAb and TgAb positivity or increases during ICI treatment may be a useful biomarker to identify patients at increased risk of thyroid irAEs, particularly overt thyrotoxicosis.

Thyroid-related adverse events induced by immune checkpoint inhibitors

Immune checkpoint inhibitors, namely anti-CTLA-4, anti-PD-1 and anti-PD-L1 monoclonal antibodies, have emerged in the last decade as a novel form of cancer treatment, promoting increased survival in patients. As they tamper with the immune response in order to destroy malignant cells, a new type of adverse reactions has emerged, known as immune-related adverse events (irAEs), which frequently target the endocrine system, especially the thyroid and hypophysis. Thyroid irAEs include hyperthyroidism, thyrotoxicosis, hypothyroidism and a possibly life-threatening condition known as the "thyroid storm". Early prediction of occurrence and detection of the thyroid irAEs should be a priority for the clinician, in order to avoid critical situations. Moreover, they are recently considered both a prognostic marker and a means of overseeing treatment response, since they indicate an efficient activation of the immune system. Therefore, a multidisciplinary approach including both oncologists and endocrinologists is recommended when immune checkpoint inhibitors are used in the clinic.

Immune Related Adverse Events of the Thyroid - A Narrative Review

Immune checkpoints are small molecules present on the cell surface of T-lymphocytes. They maintain self-tolerance and regulate the amplitude and duration of T-cell responses. Antagonism of immune checkpoints with monoclonal antibodies (immune checkpoint inhibitors) is a rapidly evolving field of anti-cancer immunotherapy and has become standard of care in management of many cancer subtypes. Immune checkpoint inhibition is an effective cancer treatment but can precipitate immune related adverse events (irAEs). Thyroid dysfunction is the most common endocrine irAE and can occur in up to 40% of treated patients. Both thyrotoxicosis and hypothyroidism occur. The clinical presentation and demographic associations of thyrotoxicosis compared to hypothyroidism suggest unique entities with different etiologies. Thyroid irAEs, particularly overt thyrotoxicosis, are associated with increased immune toxicity in other organ systems, but also with longer progression-free and overall survival. Polygenic risk scores using susceptibility loci associated with autoimmune thyroiditis predict development of checkpoint inhibitor associated irAEs, suggesting potentially shared mechanisms underpinning their development. Our review will provide an up-to-date summary of knowledge in the field of thyroid irAEs. Major focus will be directed toward pathogenesis (including genetic factors shared with autoimmune thyroid disease), demographic associations, clinical presentation and course, treatment, and the relationship with cancer outcomes.

Does Clinical and Biochemical Thyroid Dysfunction Impact on Endometrial Cancer Survival Outcomes? A Prospective Database Study

Endometrial cancer is the commonest gynaecological malignancy in developed countries, and women presenting with high risk or advanced disease have poor outcomes. Thyroid hormones play a key role in cellular metabolism and can influence cancer growth and invasion. Our aim was to evaluate the association between clinical and biochemical thyroid dysfunction and endometrial cancer survival outcomes. This was a prospective cohort study of women treated for endometrial cancer at a specialist centre. Clinical diagnosis of hypothyroidism was based on clinical and biochemical assessment, verified by general practitioner (GP) records. Pre-treatment serum samples were tested for thyrotropin (TSH), thyroid hormones (free T4 and total T3), and thyroid peroxidase antibodies. Kaplan-Meier survival estimates and log-rank tests were used to compare survival between groups, while Cox regression was used for multivariable analysis, adjusting for known confounders and effect modifications. In total, 333 women with median age and body mass index (BMI) of 66 years (interquartile range (IQR) 56, 73) and 33 kg/m2 (IQR 27, 41) respectively were included. A total of 51 (15.3%) women had a diagnosis of hypothyroidism, 39 (11.9%) had biochemical evidence of overt or subclinical hypothyroidism. Median follow-up was 35 months (IQR 21, 45) with 38 (11.7%) relapses and 50 (15.0%) deaths. Women with a diagnosis of hypothyroidism had improved overall survival (adjusted HR = 0.22, 95%CI 0.06-0.74, p = 0.02), cancer-specific survival (adjusted HR = 0.21, 95%CI 0.05-0.98, p = 0.04) and fewer recurrences (adjusted HR = 0.17, 95%CI 0.04-0.77, p = 0.02) than those who did not. Confirmatory studies should explore underlying mechanisms and the potential for therapeutic exploitation.

The Continuum of Thyroid Disorders Related to Immune Checkpoint Inhibitors: Still Many Pending Queries

BACKGROUND

Until more data are available to shed light on the thyroid disorders related to immune checkpoint inhibitors (ICPi) implemented for the treatment of hematological malignancies, the decision-making is guided by pertinent data derived mostly from solid tumors.

METHODS

The present review provides a comprehensive and updated overview of the thyroid disorders related to ICPi, namely to inhibitors of cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death (PD) 1 (PD-1), and the ligand of the latter (PD-L1).

RESULTS

With the increasing recognition of ir thyroid disorders, many outstanding issues have emerged. Ir thyroid disorders are reminiscent of, but not identical to, thyroid autoimmunity. Interclass and intraclass ICPi differences regarding thyroid immunotoxicity await interpretation. The available data concerning the predictive value of thyroid autoantibodies for the development of ir thyroid disorders are inconclusive. Mounting data indicate an association of ir thyroid disorders with ICPi efficacy, but a causative link is still lacking. The path forward is a tailored approach, entailing: (i) the validation of tumor-specific, patient-specific, and ICPi-specific predictive factors; (ii) appropriate patient selection; (iii) the uncoupling of antitumor immunity from immunotoxicity; (iv) a multidisciplinary initiative; and (v) global registry strategies.

CONCLUSIONS

Untangling and harnessing the interrelationship of immuno-oncology with endocrinology underlying the ir thyroid disorders will yield the optimal patient care.

Survival benefit of endocrine dysfunction following immune checkpoint inhibitors for nonthyroidal cancers

PURPOSE OF REVIEW

Our goal is to review pertinent data evaluating the association between immune checkpoint inhibitor (ICI)-induced endocrine dysfunction and survival in cancer patients as well as to understand the potential molecular links between these.

RECENT FINDINGS

ICIs have revolutionized cancer therapy but have also led to multiple immune-related adverse events (irAEs). Studies have demonstrated a link between the development of irAEs and improved survival, suggesting that ICI-induced antitumor immunity and autoimmunity are coupled. Thyroid irAEs are most frequently and strongly associated with improved survival, particularly in the context of overt thyroid dysfunction. Other endocrine irAEs, such as hypophysitis and diabetes are quite rare wherein the treatment approach or the disease process itself may mitigate improvement in survival. Preclinical and translational data indicate a role for CD4+ T cells, regulatory T cells and/or cytokines mediating irAEs, including thyroiditis.

SUMMARY

The development of irAEs is associated with improved tumor responses and survival in cancer patients. Thyroid irAEs, alone or in combination with other irAEs, are most strongly associated with improved outcomes. Biomarkers of response to ICIs are lacking, despite well-characterized pathologic and genomic susceptibilities predicting ICI efficacy. Early detection of thyroid irAEs may identify patients most likely to have durable antitumor response to ICIs. Although irAEs and antitumor immunity appear 'coupled', translational studies indicate the potential for their 'uncoupling', which could enable antitumor efficacy with greater safety margins.

Thyroid Immune-related Adverse Events Following Immune Checkpoint Inhibitor Treatment

CONTEXT

Thyroid dysfunction occurs commonly following immune checkpoint inhibition. The etiology of thyroid immune-related adverse events (irAEs) remains unclear and clinical presentation can be variable.

OBJECTIVE

This study sought to define thyroid irAEs following immune checkpoint inhibitor (ICI) treatment and describe their clinical and biochemical associations.

METHODS

We performed a retrospective cohort study of thyroid dysfunction in patients with melanoma undergoing cytotoxic T-lymphocyte antigen-4 (CTLA-4) and/or programmed cell death protein-1 (PD-1) based ICI treatment from November 1, 2009, to December 31, 2019. Thyroid function was measured at baseline and at regular intervals following the start of ICI treatment. Clinical and biochemical features were evaluated for associations with ICI-associated thyroid irAEs. The prevalence of thyroid autoantibodies and the effect of thyroid irAEs on survival were analyzed.

RESULTS

A total of 1246 patients were included with a median follow-up of 11.3 months. Five hundred and eighteen (42%) patients developed an ICI-associated thyroid irAE. Subclinical thyrotoxicosis (n = 234) was the most common thyroid irAE, followed by overt thyrotoxicosis (n = 154), subclinical hypothyroidism (n = 61), and overt hypothyroidism (n = 39). Onset of overt thyrotoxicosis occurred a median of 5 weeks (interquartile range [IQR] 2-8) after receipt of a first dose of ICI. Combination immunotherapy was strongly associated with development of overt thyrotoxicosis (odds ratio [OR] 10.8, 95% CI 4.51-25.6 vs CTLA-4 monotherapy; P < .001), as was female sex (OR 2.02, 95% CI 1.37-2.95; P < .001) and younger age (OR 0.83 per 10 years, 95% CI 0.72-0.95; P = .007). By comparison, median onset of overt hypothyroidism was 14 weeks (IQR 8-25). The frequency of overt hypothyroidism did not differ between different ICI types. The strongest associations for hypothyroidism were higher baseline thyroid-stimulating hormone (OR 2.33 per mIU/L, 95% CI 1.61-3.33; P < .001) and female sex (OR 3.31, 95% CI 1.67-6.56; P = .01). Overt thyrotoxicosis was associated with longer progression free survival (hazard ratio [HR] 0.68, 95% CI 0.49-0.94; P = .02) and overall survival (HR 0.57, 95% CI 0.39-0.84; P = .005). There was no association between hypothyroidism and cancer outcomes.

CONCLUSION

Thyroid irAEs are common and there are multiple distinct phenotypes. Different thyroid irAE subtypes have unique clinical and biochemical associations, suggesting potentially distinct etiologies for thyrotoxicosis and hypothyroidism arising in this context.

Immune-related toxicities of checkpoint inhibitors: mechanisms and mitigation strategies

The immune-related adverse events associated with treatment with immune checkpoint inhibitors result in significant morbidity for patients as well as considerable cost to the health-care system, and can limit the use of these beneficial drugs. Understanding the mechanisms of these side effects and how they can be separated from the antitumour effects of immune checkpoint inhibitors, as well as identifying biomarkers that predict the development of immune-related toxicities, will facilitate the conduct of trials to limit their onset and improve patient outcomes. In this Review, we discuss the different types of immune-related adverse events and how their treatment and identification of possible predictive biomarkers may shed light on their mechanisms, and describe possible strategies and targets for prophylactic and therapeutic intervention to mitigate them.

Thyroid Immune-Related Adverse Events in Patients with Cancer Treated with anti-PD1/anti-CTLA4 Immune Checkpoint Inhibitor Combination: Clinical Course and Outcomes

OBJECTIVE

Thyroid immune-related adverse events (irAEs) have been reported to have prognostic significance among patients with cancer treated with anti-programmed cell death-1 (PD1) and anti-programmed death-ligand 1 monotherapies. We evaluated the clinical course and predictors of thyroid irAEs in relation to outcomes of patients with advanced cancer treated with combination anti-PD1/anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA4).

METHODS

We conducted a regional study and identified patients with advanced cancer who received ≥1 cycle of combination anti-PD1/anti-CTLA4 between 2015 and 2019 in Hong Kong. Thyroid function tests (TFTs) were monitored every 3 weeks. Thyroid irAE was defined by ≥2 abnormal TFTs after initiation of combination anti-PD1/anti-CTLA4 in the absence of other causes.

RESULTS

One hundred and three patients were included (median age: 59 years; 71.8% men). About 45% had prior anti-PD1 exposure. Upon median follow-up of 6.8 months, 17 patients (16.5%) developed thyroid irAEs, where 6 initially presented with thyrotoxicosis (overt, n = 4; subclinical, n = 2) and 11 with hypothyroidism (overt, n = 2; subclinical, n = 9). Eventually, 10 patients (58.8%) required continuous thyroxine replacement. Systemic steroid was not required in all cases. Prior anti-PD1 exposure (odds ratio, 3.67; 95% CI, 1.19-11.4; P = .024) independently predicted thyroid irAEs. Multivariable Cox regression analysis revealed that occurrence of thyroid irAEs was independently associated with better overall survival (adjusted hazard ratio, 0.34; 95% CI, 0.17-0.71; P = .004).

CONCLUSION

Thyroid irAEs are common in routine clinical practice among patients with advanced cancer treated with anti-PD1/anti-CTLA4 combination and might have potential prognostic significance. Regular TFT monitoring is advised for timely treatment of thyroid irAEs to prevent potential morbidities.

Proteasomal and lysosomal degradation for specific and durable suppression of immunotherapeutic targets

Cancer immunotherapy harness the body’s immune system to eliminate cancer, by using a broad panel of soluble and membrane proteins as therapeutic targets. Immunosuppression signaling mediated by ligand-receptor interaction may be blocked by monoclonal antibodies, but because of repopulation of the membrane via intracellular organelles, targets must be eliminated in whole cells. Targeted protein degradation, as exemplified in proteolysis targeting chimera (PROTAC) studies, is a promising strategy for selective inhibition of target proteins. The recently reported use of lysosomal targeting molecules to eliminate immune checkpoint proteins has paved the way for targeted degradation of membrane proteins as crucial anti-cancer targets. Further studies on these molecules’ modes of action, target-binding “warheads”, lysosomal sorting signals, and linker design should facilitate their rational design. Modifications and derivatives may improve their cell-penetrating ability and the in vivo stability of these pro-drugs. These studies suggest the promise of alternative strategies for cancer immunotherapy, with the aim of achieving more potent and durable suppression of tumor growth. Here, the successes and limitations of antibody inhibitors in cancer immunotherapy, as well as research progress on PROTAC- and lysosomal-dependent degradation of target proteins, are reviewed.