Tyrosine Kinase Research Articles

7959 Combination Therapy Of Multi-Targeted Tyrosine Kinase Inhibitors And Immune Checkpoint Inhibitors In Advanced Adrenocortical Carcinoma

Abstract Disclosure: F. Yaylaci Mert: None. V. Balderrama Brondani: None. L.P. Marcal: None. M. Campbell: None. C. Jimenez: None. J. Varghese: None. A. Shah: None. M.A. Habra: None. Background: Adrenocortical carcinoma (ACC) is a rare cancer with limited response to systemic chemotherapies. Monotherapy with multi-targeted tyrosine kinase inhibitors (TKIs) or immune checkpoint inhibitors (ICIs) in ACC patients has limited efficacy. Combining TKIs with ICIs increased response rates in other malignancies but the efficacy of this approach in ACC is still unknown. This retrospective study aims to evaluate the efficacy and safety of the combined use of TKIs and ICIs in patients with advanced ACC. Methods: A single-center, retrospective cohort study in patients with advanced ACC treated with the combination of TKIs and ICIs. Response rates, progression-free survival (PFS), overall survival (OS) calculated from the time of combination, disease control rate (DCR), and safety profile were the main study objectives. Results: Seventeen patients were treated with combination therapy of TKI (lenvatinib or cabozantinib) and ICI (pembrolizumab) between January 2017 and December 2023. Eleven patients were women, the median age was 43.4 years (range 21.9-66.6), and 8 (47.1%) patients presented cortisol-producing tumors. All patients had prior systemic therapy, median of 3 (range 1-9) lines of therapy. The median duration of TKI+ICI therapy was 7.1 months (range 0.7-69.7). The treatment was discontinued in one patient due to a grade 3 adverse event (gastrointestinal fistula) after 1.6 months of treatment. Best overall responses were as follows: partial response 2 (13%), stable disease 8 (53%), and progressive disease 5 (34%). DCR was 58.8%. Median PFS was 7.1 months (range 0.7-66.4). One death occurred during the study due to disease progression. The median OS was 21.3 months (range 3.3-70.3). At the time of this report, 7 patients (41%) were still alive. Conclusion: The combined use of TKIs and ICIs in heavily treated ACC patients is associated with occasional durable responses and has a predictable and manageable side effect profile. This combination is worthy of a prospective clinical trial to validate the findings and establish new lines of therapy for this rare disease. Presentation: 6/2/2024

7581 Periodic Administration of Quercetin and Dasatinib Alleviates Skeletal Fragility in the INS2AKITA Mouse Model of Type 1 Diabetes

Abstract Disclosure: R. Dresner-Pollak: Consulting Fee; Self; Opko Biologics LTD.. Speaker; Self; Medison Pharma. N. Lishinsky: None. I. Gurt: None. J. Stokar: None. V. Temkin: None. P. Shivam: None. G. Zatarah: None. J. Milgram: None. R. Shahar: None. Skeletal fragility is a recognized complication of type 1 diabetes (T1D). The risk of hip and non-vertebral fractures is significantly higher in people living with T1D compared to age- and sex-matched non-diabetic controls and those living with type 2 diabetes (T2D). Hip fracture risk is up to six-fold higher in T1D patients; hip fractures occur 10-15 years earlier and the outcome is poorer compared to non-diabetics. Alterations in bone quality are considered major contributors to T1D-related skeletal fragility. As people with T1D live longer, there is a growing need to discover new therapeutics to reduce fracture risk. TID is associated with accelerated biological aging. Cellular senescence is a fundamental mechanism of aging. Senescent cells stop dividing, are resistant to apoptosis and acquire a distinct phenotype that includes secretome changes termed “senescence-associated secretory phenotype” (SASP). Clearing senescent cells with senolytics is recognized as a promising therapeutic approach for multiple conditions in mice and humans We explored the ability of senolytics dasatinib (D), a tyrosine kinase inhibitor, and quercetin (Q), a flavanol, present in fruit and vegetables, drug combination, to alleviate femur fragility in mice with T1D. Ins2Akita mice show a sexual dimorphic effect of the mutant Ins2 allele causing severe hyperglycemia in males. We treated Ins2Akita male and female mice and C57BL/6 wild type (WT) male mice with D + Q administered once monthly for four months beginning at age 3 months. 3-month-old Ins2Akita male mice had higher blood levels of the SASPs components HMGB1, PAI-1, MMP12, and increased gene expression of p53 and senescence effectors p16, p15 and SASPs Il1b, Mmp3, Mmp9, Mmp13, Serpineb2 at the femur diaphysis and in bone marrow mesenchymal stem cells, respectively compared to age-matched WT male mice. In vitro, exposure to glucose levels equivalent to those observed in blood in Ins2Akita male mice induced cellular senescence in IDG-SW3 osteocyte-like cells including a 4-5-fold increase in gene expression of p16INK4a, p21Cip[1], p53, double percentage of SA-β-gal+ cells and P21 protein level. Ingenuity pathway analysis of differentially expressed proteins revealed enrichment for the senescence pathway (Z=1.213; P=1.11E-05). D+Q administration did not affect bone microarchitecture at the spine (L2), distal femur metaphysis and diaphysis assessed by µCT. D+Q administration significantly increased femur resistance to fracture assessed by the 3-point-bending test by increasing whole femur work-to-fracture, the ultimate parameter of bone resistance to failure, and post-yield displacement, an index of matrix composition, organization, and bone quality in Ins2Akita males. No effect was observed in Ins2Akita females or WT male mice, indicating that the intervention is specific for T1D. Senolyitcs D+Q show promise in improving bone health in T1D. Presentation: 6/1/2024

7862 The Paradoxical Role Of ERFFI1 In Breast Cancer Progression Is Supported By Its Dynamic Protein Interactome

Abstract Disclosure: A. Ocampo: None. P.D. Bagamasbad: None. In breast cancer (BCa), glucocorticoid (GC) therapy is used in anti-emetic and palliative care. However, the effects of GC therapy in BCa are conflicting as it is beneficial for hormone-responsive luminal subtypes while it promotes tumor progression in more aggressive triple-negative BCa (TNBCs). A factor implicated in this paradoxical shift is the feedback inhibitor of epidermal growth factor receptor (EGFR) signaling, ERBB receptor feedback inhibitor 1 (ERRFI1). In BCa cell lines, ERRFI1 expression is directly regulated by GC receptor (GR). More interestingly, ERRFI1 was found to restrict the GC-enhanced proliferation in normal breast epithelia but enhances the GC-mediated pro-tumorigenic effects in highly aggressive TNBC. To identify the mechanism behind the shift in ERFFI1 function through BCa progression, ERRFI1 protein interactions in the luminal, HER2, and TNBC subtypes were analyzed by identifying differentially expressed proteins from each subtype using available proteome and interactome datasets from Integrated Interactions Database and followed by network and clustering analyses through STRING. The ERRFI1 interactome varied across the subtypes, and gene ontology analysis of the protein networks revealed progressive tumorigenic effects from the least aggressive luminal subtype to the most aggressive TNBC. The luminal BCa-ERRFI1 interactome showed metastatic potential that is countered by negative regulation of receptor tyrosine kinase (RTK) signaling. The HER2-ERRFI1 interactome highlighted the amplification of RTK signaling and its possible modulation through SRC while the TNBC-ERRFI1 interactome presents pro-oncogenic proteins implicated in drug resistance, angiogenesis, and EMT. Interestingly, the interactome also revealed a link between EGFR signaling and GR signaling possibly through ERRFI1, EGFR, and SFN. To determine the function of ERFFI1 in EGFR signaling in BCa, we generated stable ERRFI1 knockdown in different breast epithelial cell models through lentiviral transduction. Cells were then treated with EGF followed by gene expression analysis of known EGF-upregulated genes such as MYC, GSK3B, MCL1, and MMP9. We found that ERRFI1 knockdown enhanced the EGF-dependent induction of MYC and MMP9 in normal MCF10A cells and this effect was not observed in the TNBC MDA-MB-468 line, suggesting the loss of ERRFI1-mediated inhibition of EGFR signaling with BCa tumorigenic potential. Taken together, our findings suggest that the progressive loss of anti-tumorigenic function of ERRFI1 may be explained by its changing interactome in BCa molecular subtypes. Presentation: 6/3/2024

7410 Bevacizumab Induced Hypothyroidism

Abstract Disclosure: A.L. McKenna: None. S. Thota-Kammili: None. K. Grennan: None. S. Rao: None. It is known that thyroid dysfunction is an adverse effect of tyrosine kinase inhibitors (TKIs) via inhibition of the vascular endothelial growth factor receptor (VEGFR). The VEGF signaling pathway is important in regulating angiogenesis in tumors and normal tissue. As a highly vascularized gland, it is expected the thyroid may be compromised because of VEGFR inhibitors. Proposed mechanisms of thyroid dysfunction include capillary regression and constriction leading to reduced vascular perfusion to the gland. Bevacizumab is a monoclonal antibody that targets VEGF and inhibits activation of VEGFR, reducing angiogenesis; interestingly, this is not commonly reported in the literature. Here we present a case where bevacizumab altered thyroid function in a patient with pre-existing primary hypothyroidism. A 60-year-old woman presented with worsening hypothyroidism. She reported a history of nonautoimmune primary hypothyroidism diagnosed in her early 20s; she still had an intact thyroid with no history of head/neck radiation. In the months leading to the presentation, she had been receiving maintenance chemotherapy with 5 fluorouracil and bevacizumab every 2 weeks for metastatic duodenal carcinoma. Prior to starting chemotherapy, she had been on a steady dose of 112 mcg of levothyroxine (LT4) daily. After 6 months on chemotherapy, she reported symptoms of fatigue and hair loss. Workup revealed an elevated TSH of 41 mIU/L (reference 0.3-4.2 mIU/L). She denied any significant changes in weight or malabsorption issues. Aside from the chemotherapy, no other new medications were introduced. Her LT4 dose was increased to 137 mcg daily, and 3 months later, there was improvement in TSH to 6.5 mIU/L as well as her symptoms. At this point, bevacizumab was briefly on hold for 2 months due to an upcoming procedure, hence there was no change to LT4 to avoid over correction. Her TSH normalized and was trending lower while bevacizumab was on hold. Once bevacizumab resumed, LT4 was preemptively increased to 150 mcg daily. Four months after resuming bevacizumab, her TSH remains within the normal reference range on 150 mcg LT4. It is hypothesized that this VEGF blocker led to worsening of her underlying hypothyroidism.Given the shared down regulation in the VEGF signaling pathway, it would be expected that TKIs and monoclonal antibodies against VEGF would share similar adverse reactions to the thyroid. However, to our knowledge, there have been limited reports of bevacizumab induced thyroid dysfunction in the literature. Explanations to this may include the more targeted VEGF inhibition with bevacizumab versus the inhibition of multiple kinase receptors from the TKIs. Further research into this will be needed. This case demonstrates that bevacizumab can impact thyroid function and thyroid labs may need to be monitored at the onset and during VEGF inhibitor therapies. Presentation: 6/3/2024

9182 Metastatic Extra-Gastrointestinal Stromal Tumor Presenting As Hypoglycemia

Abstract Disclosure: O. faour: None. D. John: None. S.K. Suryanarayanan: None. A.A. Rizvi: None. Introduction: Non islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome seen in association with solid abdominal tumors of mesenchymal and epithelial origin. We report a case of metastatic extra-gastrointestinal stromal tumor (E-GIST) presenting with severe hypoglycemia as its initial manifestation. CASE DESCRIPTION: A 46-year-old patient was found to have a blood glucose of <45 mg/dl during a routine clinic visit with her primary care physician. Although she was asymptomatic, she was sent to the emergency room (ER) for further evaluation. She had a history of prediabetes managed by lifestyle modification. She has been experiencing multiple episodes of hypoglycemia previously which fulfilled the Whipple’s triad in the preceding months. These hypoglycemic episodes included loss of unconsciousness, falls in the shower with head injury, and several hospital visits. Serum glucose in the ER was 14 mg/dl and hypoglycemia persisted despite continuous dextrose solution. Physical examination was notable for a distended, non-tender abdomen and cervical lymphadenopathy. CT scan showed a 15 cm mass in the liver, multiple large masses in the mesentery, and a 11 cm lesion in the left pelvis. There were enlarged lymph nodes in the abdomen, chest, and neck. Serum chemistries drawn when the patient was hypoglycemic revealed potassium level of 2.7 mg/dl (3.5-5.5) an insulin level of <1.0 mIU/L (5-25), C-peptide <0.1 ng/mL (0.5-2), cortisol 13.8 mcg/dL (5-25), and insulin-like growth factor-2 (IGF-2) was 270 ng/mL (38-267). The IGF-2/IGF-1 molar ratio was 3.4 (normal <3:1). The sulfonylurea drug screen came back negative. Upper and lower endoscopies were unrevealing. Biopsy of the liver lesion showed cytology and immunohistochemical findings consistent with a epithelioid metastatic extra-gastrointestinal stromal tumor. A provisional diagnosis of NICTH was made. The patient responded well to intravenous glucose, oral carbohydrate intake and high-dose corticosteroids. She was subsequently started on therapy with the tyrosine kinase inhibitor (TKI) imatinib. Discussion: Paraneoplastic hypoglycemia is often seen in association with metastatic epithelial and mesenchymal tumors. IGF-2 and incompletely processed pro-IGF-2 activates autocrine, paracrine, and endocrine pathways that lead to tumor growth, fasting hypoglycemia, rarely of acromegalic features. Treatment with octreotide, diazoxide, and glucagon is generally ineffective, while glucocorticoid use and surgical intervention are helpful in ameliorating the hypoglycemia. Tumor-directed therapy with TKIs, primarily imatinib, appears promising in achieving remission. Our case is a clinical reminder that hypoglycemia secondary to NICTH can be the predominant presenting feature in patients with underlying E-GIST. Presentation: 6/3/2024

Population Pharmacokinetic Analysis of Tucatinib in Healthy Participants and Patients with Breast Cancer or Colorectal Cancer.

Tucatinib is a highly selective, oral, reversible, human epidermal growth factor receptor 2 (HER2)-specific tyrosine kinase inhibitor. Tucatinib is approved at a 300-mg twice-daily dose in adults in combination with trastuzumab and capecitabine for advanced HER2-postitive (HER2+) unresectable or metastatic breast cancer and in combination with trastuzumab for RAS wild-type HER2+ unresectable or metastatic colorectal cancer. This study sought to characterize the pharmacokinetics (PK) and assess sources of PK variability of tucatinib in healthy volunteers and in patients with HER2+ metastatic breast or colorectal cancers. A population pharmacokinetic model was developed based on data from four healthy participant studies and three studies in patients with either HER2+ metastatic breast cancer or metastatic colorectal cancer using a nonlinear mixed-effects modeling approach. Clinically relevant covariates were evaluated to assess their impact on exposure, and overall model performance was evaluated by prediction-corrected visual predictive checks. A two-compartment pharmacokinetic model with linear elimination and first-order absorption preceded by a lag time adequately described tucatinib pharmacokinetic profiles in 151 healthy participants and 132 patients. Tumor type was identified as a significant covariate affecting tucatinib bioavailability and clearance, resulting in a 1.2-fold and 2.1-fold increase in tucatinib steady-state exposure (area under the concentration-time curve) in HER2+ metastatic colorectal cancer and HER2+ metastatic breast cancer, respectively, compared with healthy participants. No other covariates, including mild renal or hepatic impairment, had an impact on tucatinib pharmacokinetics. The impact of statistically significant covariates identified was not considered clinically meaningful. No tucatinib dose adjustments are required based on the covariates tested in the final population pharmacokinetic model. NCT03723395, NCT03914755, NCT03826602, NCT03043313, NCT01983501, NCT02025192.

8576 Genomic and Transcriptomic Characterization of Pediatric Thyroid Cancers

Abstract Disclosure: J.C. Ricarte-Filho: None. E.R. Reichenberger: None. K. Hinkle: None. A.R. Isaza: None. A.J. Bauer: None. A.T. Franco: None. Background: Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer in both pediatric and adult populations. Recent genomic profiling of papillary thyroid cancers, including that of the Cancer Genome Atlas, has uncovered the genetic alterations and molecular mechanisms driving thyroid cancer. However, these studies were primarily focused on adult patients. Despite their favorable prognosis, pediatric PTCs have higher rates of metastasis and recurrence than adult PTCs, but the molecular characterization of these tumors have been comparatively lacking. Methods: Here we explore the genomic and transcriptomic landscape of pediatric PTCs from 126 patients, including 107 primary tumors and 19 lymph node metastases (non-paired) using whole-exome sequencing and RNA sequencing. Thirteen primary tumors also had a paired lymph node metastasis analyzed. Results: We found driver alterations in 113 of 126 (90%) of the PTCs investigated, including the identification of a novel receptor tyrosine kinase (RTK) fusion not previously reported in thyroid cancer. Genetic drivers were predominantly kinase fusions (48%), most commonly fusions of RET (22%), NTRK3 (10%), ALK (5%) and NTRK1 (5%). The most common point mutations were BRAF p.V600E (21%), NRAS p.Q61R/K (9%) and hotspot mutations in DICER1 (4%). We found genetic alterations in 12 of the 13 paired lymph node metastasis. In all 12 cases the metastatic tissue harbored the same alterations found in the primary tumor. Eight out of 12 cases had fusions (3 RET, 3 NTRK3 and 2 NTRK1), and the additional 4 cases had point mutations (3 BRAFV600E and 1 TSHRM543T). Fourteen patients (11%) had widely invasive disease with lateral lymph node and distant metastases (N1bM1). Most of these N1bM1 tumors (13/14; 93%) were driven by RTK fusions (5 NTRK3, 3 RET, 3 NTRK1 and 2 ALK). The one case lacking a kinase fusion had a CHEK2 mutation. Conclusion: Our genomic and transcriptomic analysis allowed the detection of driver alterations in ∼90% of the cases, reducing the so-called “dark matter” in our cohort. Our data support that kinase fusions are associated with metastatic disease in pediatric PTC. Patients with RET/NTRK/ALK fusions have worse outcomes than those with BRAF p.V600E mutation and RAS-like alterations (NRAS, DICER1, non-V600 BRAF, PTEN). By using the transcriptional profiling generated in this study, we are currently investigating the molecular mechanisms underlying the metastatic behavior of pediatric PTCs harboring oncogenic fusions, including changes in MAPK transcriptional output, differentiation score and recruitment of signaling pathways potentially associated with the metastatic behavior of these tumors. Presentation: 6/3/2024

7272 Antineoplastic Effect of Cabozantinib in Primary and Continuous Human Anaplastic Thyroid Cancer Cells

Abstract Disclosure: G. Elia: None. S. Ferrari: None. F. Ragusa: None. V. Mazzi: None. A. Patrizio: None. E. Balestri: None. C. Botrini: None. L. Rugani: None. E. Barozzi: None. C. La Motta: None. P. Fallahi: None. A. Antonelli: None. Anaplastic thyroid cancer (ATC) is a highly aggressive cancer with a low median survival of about 6-10 months. The standard treatment include surgery, external hyperfractionated radiation therapy, and chemotherapy. However, these therapies are not effective and new therapeutical approaches are needed. Tyrosine kinase inhibitors (TKI) are a class of drugs able to inhibit different pathways that results inappropriately activated in cancer cells.To date no studies evaluated the effect of cabozantinib in primary human ATC cells, and in ATC continuous cell line in vitro. We aimed to test the efficacy of cabozantinib a multiTKI acting against VEGFR 1,2, c-MET, and RET (recently approved for aggressive differentiated thyroid cancer) in primary human ATC cells, and in ATC continuous cell line (8305C, CAL-62) in vitro. Therefore, for primary ATC cells we collected surgical thyroidal tissues from five patients with ATC, from thyroid biopsy at the moment of first surgical operation, and we tested the effect of cabozantinib. Cabozantinib showed its efficacy in inhibiting cell proliferation, and also in increasing apoptosis (p < 0.05) both in primary and in continuous ATC cells. In conclusion, cabozantinib demonstrated a good antineoplastic activity in human ATC cells in vitro. These results open the way for a possible clinical use of cabozantinib in patients with ATC, and are important for a personalized therapeutic approach to be tailored to each patient avoiding the administration of ineffective drugs. Presentation: 6/1/2024

6847 Poorly Differentiated Thyroid Cancer: A Rare Entity

Abstract Disclosure: S. Fatima: None. S. Ward: None. A. Champion: None. Introduction: Poorly differentiated thyroid carcinoma (PDTC) is a rare thyroid carcinoma originating from follicular epithelial cells. Regarding the degree of differentiation, PDTC ranks between differentiated thyroid cancer and anaplastic thyroid cancer. We hereby present a rare case of PDTC. Case: 29-year-old female with a history of metastatic papillary thyroid cancer (PTC) presented to the emergency department with shortness of breath. She initially noticed a left thyroid mass in 2021. CT neck in 1/2022 showed a 7 cm left thyroid mass with substernal extension, small right thyroid mass with tracheal compression, left bulky cystic nodal masses extending anterior and posterior to carotid and internal jugular vein. PET scan in 3/2022 showed left 7.6 cm thyroid mass SUV 12.1 with tracheal compression, left level II-IV adenopathy with level IV nodal masses 5.1 cm SUV 4.5. Ultrasound-guided FNA in 4/2022 showed PTC in left 8.7cm thyroid nodule; right 2.8 cm nodule showed Atypia of Undetermined Significance; Left 5.5 cm neck level III lymph node (LN) showed PTC metastasis; right 5.1 cm neck level III LN showed PTC metastasis (+ thyroglobulin and TTF-1). CT chest in 11/2022 showed additional involvement of manubrium. Repeat core needle biopsy of left thyroid mass showed left invasive thyroid carcinoma. She was started on neoadjuvant Lenvatinib in 1/2023. Follow-up CT neck in 5/2023 showed a reduction in the size of the left thyroid mass to 5.5cm x 5.8cm x 6.5cm. At this time, she had symptoms of dysphagia, orthopnea, weight loss of about 60 lbs and neck pain. In 11/2023 at time of current presentation she underwent total thyroidectomy, bilateral modified radical neck dissection and manubriectomy. Surgical pathology showed PDTC in left thyroid mass, PTC in right thyroid mass with metastatic PDTC in left proximal sternocleidomastoid, manubrium and LN involvement in neck and mediastinum. OmniSeq Insight testing showed APC and BRCA1 gene mutations, negative BRAF V600E, RET fusion, RET mutation, NTRK1/2/3 fusion and PD L1 immunohistochemistry score is <1%. The patient is planned to receive [1]3[1]I ablation therapy. Conclusion: PDTC accounts for 3–5% of all thyroid carcinomas. The 5, 10-, and 15-year survival rates of patients are 50–85%, 34–50%, and 0%, respectively. RAS gene alterations are found in 25–35%, BRAF mutation in 15–27%, TERT promoter mutation in 40% and mutant TP53 in 16–28% of PDTCs. TERT promoter gene and TP53 mutation usually indicate an aggressive phenotype and a dismal prognosis. Surgery, [1]3[1]I therapy, and external beam radiotherapy constitute the mainstay of traditional treatment for patients with advanced disease; however, treatment is challenging. Tyrosine kinase inhibitors i.e, sorafenib and lenvatinib, have been used in cases of progressive, recurrent, or metastatic disease not responsive to [1]3[1]I therapy. Immunotherapy may be an option in PD-L1-positive tumors. Presentation: 6/1/2024

7626 Endocrine Adverse Reactions Of Tyrosine Kinase Inhibitors In Combination With Immune Checkpoint Inhibitors: A Retrospective Analysis Using The US FDA Adverse Event Reporting System

Abstract Disclosure: W. Shao: None. D. Lu: None. K. Yang: None. Y. Gao: None. J. Zhang: None. Y. Zhang: None. Background: Tyrosine kinase inhibitor (TKI) and immune checkpoint inhibitor (ICI) have been recognized to cause multiple endocrine adverse reactions (EARs). However, the combination therapy-associated EARs is still unclear. We aimed to evaluate the clinical characteristics and prognosis of EARs induced by TKI, ICI and TKI+ICI therapy. Methods: Using the US FDA Adverse Event Reporting System, 938464 cases of all adverse events, adult patients, related to the three types of treatments from January 2001 to September 2023 were identified. A total of 22275 cases were EARs and divided into TKI (n=9181), ICI (n=11363) and TKI+ICI group (n=1731). Results: The incidence of EARs was the highest in TKI+ICI group (9.1%), followed by ICI (7.7%), and TKI group (1.2%) (P < 0.05). Among patients with EARs, the proportions of female and Asian patients were significantly greater in TKI+ICI group than in the other groups (P<0.05 for all). TKI+ICI group had a larger proportion of elderly patients compared with TKI group. The most common type of EARs in TKI+ICI group was thyroid dysfunction (TD) (67.5%), followed by glucose metabolism disorder (GMD) (14.0%). Compared with TKI group, TKI+ICI group displayed a higher risk of TD (OR 3.247, 95% CI [2.849-3.701]), pituitary dysfunction (PD) (OR 6.199, 95% CI [4.534-8.474]), and primary adrenal insufficiency (PAI) (OR 4.178, 95% CI [3.470-5.031]), while the risk of GMD was lower (OR 0.136, 95% CI [0.115-0.161]). Compared with ICI group, an increasing trend of TD (OR 2.640, 95% CI [2.328-2.995]) was found in TKI+ICI group, while a lower risk of GMD (OR 0.388, 95% CI [0.328-0.459]) and PD (OR 0.312, 95% CI [0.255-0.383]) was observed in TKI+ICI group. Hypothyroidism and diabetes mellitus were the main types of TD and GMD in all three groups. Patients with polyendocrine glands involvement accounted for the largest proportion in ICI group (11.4%), followed by TKI +ICI (7.9%), and TKI group (2.3%) (P<0.05). In TKI+ICI group, elderly patients, Asians, melanoma patients were more likely to experience multi-glandular EARs. In terms of prognosis, TKI+ICI group presented a higher risk of hospitalization compared to TKI (OR 2.201, 95% CI [1.943-2.492]) and ICI group (OR 1.282, 95%CI [1.139-1.442]). However, the mortality risk of TKI+ICI group was significantly lower (OR 0.717, 95% CI [0.588-0.874]) than TKI group, and there was no significant difference compared to ICI group. Moreover, there was no difference in mortality between patients with polyendocrine and single endocrine gland involvement. Conclusions: EARs were more common in TKI+ICI therapy. The distribution of EARs in different glands varied among combination therapy and monotherapy. Combination therapy associated EARs did not increase the risk of mortality. Key words: Tyrosine kinase inhibitors, Immune checkpoint inhibitors, Combination therapy, Endocrine adverse reactions, Prognosis Presentation: 6/3/2024

6850 A Case of Anaplastic Thyroid Carcinoma With a Complete Metabolic Response to Pembrolizumab

Abstract Disclosure: E. Tirthani: None. J.T. Kung: None. Background: Anaplastic thyroid carcinoma (ATC) is an aggressive disease with limited therapeutic options and generally poor prognosis. Post-surgery, most patients are treated with a combination of chemotherapy, radiation, and tyrosine kinase inhibitors +/- immune checkpoint inhibitors. We describe a unique case of ATC with a complete metabolic response to pembrolizumab, a selective PD-1 inhibitor, as evidenced by imaging. Clinical Case: A 69-year-old female presented to the clinic for evaluation of a rapidly enlarging neck mass. The initial ultrasound showed a large mixed cystic-solid right thyroid nodule with irregular margins with micro- and macrocalcifications, which was biopsied. Cytology showed discohesive high-grade malignant tumor cells with enlarged nuclei, nuclear hyperchromasia in the background of necrosis, and dense neutrophilic infiltration concerning for ATC. A CT scan of the neck and chest showed a complex cystic thyroid mass with central necrosis and calcification with paratracheal, supraclavicular, and mediastinal lymphadenopathy. MRI of the brain was negative for metastatic disease. The patient underwent a total thyroidectomy with right and left level 6 and 7 neck dissection. Intra-operatively, gross extrathyroidal extension of the tumor was noted to the right carotid, larynx, right recurrent laryngeal nerve, and esophagus, with residual tumor left behind near the larynx. Pathology confirmed stage IVC ATC, positive for PIK3CA, NF1, p53 mutations, and BRAF negative. 90% of tumor cells showed PD-L1 expression on immunohistochemical staining. The post-surgical PET scan showed two discrete, well-defined foci of very intense FDG uptake, corresponding to the right lower cervical and para-esophageal lymph nodes with no evidence of distant metastasis. Systemic chemotherapy with carboplatin and paclitaxel (5 cycles) was initiated with concurrent intensity modulated radiation therapy (total 60 Gy/40 fractions to thyroid bed and bilateral neck). Repeat imaging showed minimal change in the size of the PET-positive lymph nodes. Immunotherapy was initiated and with just 2 cycles of 400 mg IV pembrolizumab, a repeat PET scan was obtained, which showed a complete metabolic response to therapy. Minimal residual FDG activity in the right supraclavicular region was thought to be secondary to posttreatment changes. The patient was able to resume her activities of daily living and had an improvement in appetite. The plan is to continue 400 mg IV pembrolizumab every 6 weeks while cautiously assessing for adverse effects from immunotherapy. Conclusion: It is rare to see a complete metabolic response to therapy with pembrolizumab without concurrent use of tyrosine kinase inhibitors in patients with ATC. A high tumoral PD-L1 expression may be the key to having this kind of dramatic response. Presentation: 6/3/2024

Midostaurin added to 10-day decitabine, for patients unfit for intensive chemotherapy with AML and higher risk MDS, irrespective of FLT3 mutational status, does not improve outcome.

The treatment of older patients with acute myeloid leukemia (AML) considered unfit for receiving intensive chemotherapy is challenging. Based on the hypothesis that addition of the broad tyrosine kinase inhibitor (TKI) midostaurin could improve the response to hypomethylating agents, irrespective of FLT3 gene mutational status, we conducted a randomized phase II multicenter study to assess the tolerability and efficacy of the addition of midostaurin to a 10-day schedule of decitabine in unfit (i.e. Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) ≥ 3) AML and higher risk myelodysplasia (MDS) patients (HOVON155 trial). In total, 140 eligible patients were randomly (1:1) assigned to treatment with 10-days of decitabine alone (N = 70) or combined with midostaurin (50mg bid;starting the day following the last dose of decitabine), (N = 70). Addition of midostaurin was well tolerated and the number of AEs was comparable for both treatment arms. Early death rates (< 30 days) were similar as well (10%). In the decitabine plus midostaurin arm 24% reached CR/CRi, the median OS was 4.8 months and 1-yrs OS was 31% which compared with 34% CR/CRi, median OS of 7.4 months and 1-yrs OS of 37% for the decitabine alone group (NS). Thus, while the addition of midostaurin appears safe, it does not enhance therapeutic efficacy of decitabine in unfit AML patients.

7434 Modulation of FGFR-FGF2-FGF23 Signaling Partially Rescues Osteoarthritis in Hyp Mice Homolog of Human X- Linked Hypophosphatemia

Abstract Disclosure: M.M. Hurley: None. L. Xiao: None. Human with X-linked hypophosphatemia (XLH) and its Hyp mice homolog develop several phenotypic abnormalities due to phosphate wasting mediated by abnormal Fibroblast Growth Factor Receptor-1 (FGFR1) and Fibroblast Growth Factor 23 (FGF23) signaling. XLH and Hyp mice also develop severe osteoarthropathy (OA) whose etiology is not fully defined. We previously reported that Fibroblast growth factor 2 (FGF2) regulates FGF23, specifically, mice overexpressing the high molecular weight FGF2 isoforms (HMWFGF2) in osteoprogenitors phenocopy Hyp mice including development of OA that worsens with age. Since we also reported that Hyp mice overexpress HMWFGF2 isoforms in osteoblasts and osteocytes, we examined whether the knee OA phenotype in Hyp mice was associated with aberrant FGFR1, FGF2, FGF23 signaling in knee joint articular cartilage and subchondral bone and whether in vivo FGFR tyrosine kinase inhibitor BGJ398 would modulate the OA phenotype in knee joints of Hyp mice. Ten weeks-old Control and Hyp mice were treated with Vehicle or BGJ398 for 12 weeks. Safranin-O staining of knee articular cartilage for proteoglycan revealed decreased staining in Hyp vehicle-treated mice that was partially restored to the cartilage thickness of Control mice in the Hyp-BGJ398-treated group. Significantly increased degradative enzyme matrix metalloproteinase-13 (MMP-13) in Hyp vehicle-treated knee articular cartilage was significantly reduced by BGJ398. Immunostaining revealed significantly increased phosphorylated FGFR1, FGF2 and FGF23 in both articular cartilage and subchondral bone. While BGJ398 significantly reduced immunostaining for phosphoFGFR1 and FGF2 in both articular cartilage and subchondral bone, it significantly reduced FGF23 in subchondral bone but not in articular cartilage. Significantly increased phospho-ERK1/2 labeling in Hyp-vehicle treated articular cartilage was partially rescued by BGJ398. This study demonstrates that increased FGFR1/FGF2 signaling contributes to OA in Hyp mice that can be partially rescued by FGF receptor inhibitor via reduction in MAPK signaling. Presentation: 6/1/2024

7862 The Paradoxical Role of ERFFI1 in Breast Cancer Progression Is Supported by Its Dynamic Protein Interactome

Abstract Disclosure: A. Ocampo: None. P.D. Bagamasbad: None. In breast cancer (BCa), glucocorticoid (GC) therapy is used in anti-emetic and palliative care. However, the effects of GC therapy in BCa are conflicting as it is beneficial for hormone-responsive luminal subtypes while it promotes tumor progression in more aggressive triple-negative BCa (TNBCs). A factor implicated in this paradoxical shift is the feedback inhibitor of epidermal growth factor receptor (EGFR) signaling, ERBB receptor feedback inhibitor 1 (ERRFI1). In BCa cell lines, ERRFI1 expression is directly regulated by GC receptor (GR). More interestingly, ERRFI1 was found to restrict the GC-enhanced proliferation in normal breast epithelia but enhances the GC-mediated pro-tumorigenic effects in highly aggressive TNBC. To identify the mechanism behind the shift in ERFFI1 function through BCa progression, ERRFI1 protein interactions in the luminal, HER2, and TNBC subtypes were analyzed by identifying differentially expressed proteins from each subtype using available proteome and interactome datasets from Integrated Interactions Database and followed by network and clustering analyses through STRING. The ERRFI1 interactome varied across the subtypes, and gene ontology analysis of the protein networks revealed progressive tumorigenic effects from the least aggressive luminal subtype to the most aggressive TNBC. The luminal BCa-ERRFI1 interactome showed metastatic potential that is countered by negative regulation of receptor tyrosine kinase (RTK) signaling. The HER2-ERRFI1 interactome highlighted the amplification of RTK signaling and its possible modulation through SRC while the TNBC-ERRFI1 interactome presents pro-oncogenic proteins implicated in drug resistance, angiogenesis, and EMT. Interestingly, the interactome also revealed a link between EGFR signaling and GR signaling possibly through ERRFI1, EGFR, and SFN. To determine the function of ERFFI1 in EGFR signaling in BCa, we generated stable ERRFI1 knockdown in different breast epithelial cell models through lentiviral transduction. Cells were then treated with EGF followed by gene expression analysis of known EGF-upregulated genes such as MYC, GSK3B, MCL1, and MMP9. We found that ERRFI1 knockdown enhanced the EGF-dependent induction of MYC and MMP9 in normal MCF10A cells and this effect was not observed in the TNBC MDA-MB-468 line, suggesting the loss of ERRFI1-mediated inhibition of EGFR signaling with BCa tumorigenic potential. Taken together, our findings suggest that the progressive loss of anti-tumorigenic function of ERRFI1 may be explained by its changing interactome in BCa molecular subtypes. Presentation: 6/3/2024

7187 Non-islet Cell Tumor Hypoglycemia in a Patient With Metastatic Renal Cell Carcinoma

Abstract Disclosure: G.W. Bao: None. A.Y. Yin: None. We report a rare case of non-islet cell tumor hypoglycemia (NICTH) in a patient with metastatic renal cell carcinoma. NICTH is a paraneoplastic syndrome due to increased production of an incompletely processed form of insulin-like growth factor 2 (“big IGF-2”). It requires a high-level of suspicion for diagnosis and is challenging to manage. Our patient is a 69 year old gentleman with a history of deceased donor renal transplant in 1994 and 2008. He was diagnosed with renal cell carcinoma (RCC) metastatic to bone, lymph nodes, and lungs, which was initially treated with cabozantinib, later switched to lenvatinib and everolimus due to disease progression. On admission, he presented with anasarca and weakness. He had recurrent fasting hypoglycemia associated with confusion and lethargy. The lowest serum glucose was 28 mg/dL. He was also diagnosed with primary hypothyroidism (TSH 25.1 uIU/mL and free T4 0.31 ng/dL), suspected to be due to tyrosine kinase inhibitor therapy. Levothyroxine was initiated. Cosyntropin stimulation resulted in a post-stimulation cortisol of 7 ug/dL, although this was felt not to be reliably diagnostic of adrenal insufficiency in the setting of profound hypoalbuminemia. IGF-1 and IGF-2 were 16 ng/mL and 388 ng/mL, respectively; IGF-2: IGF-1 ratio was 24.3. He was treated with intravenous dextrose and prednisone 30mg daily with stabilization of glucoses for a few days. On hospital day 19, he acutely decompensated and passed away shortly after being transitioned to comfort-focused care. Non-diabetic hypoglycemia is relatively uncommon, and may be seen in patients with liver disease, sepsis, adrenal insufficiency, and malignancy. We report a case of NICTH in a patient with metastatic RCC, which is a particularly rare cause of hypoglycemia. NICTH is due to tumor production of “big IGF-2”, a precursor of IGF-2, which mimics the effects of insulin and causes fasting hypoglycemia. NICTH is more commonly associated with mesenchymal and epithelial tumors such as fibromas, fibrosarcomas, and hepatocellular carcinomas. NICTH due to RCC appears to be a much more rare entity, with as few as four cases reported in the literature. Laboratory findings of NICTH include low insulin, pro-insulin, C-peptide, and β-hydroxybutyrate during hypoglycemia. An IGF-2: IGF-1 ratio &amp;gt;10 is considered virtually diagnostic. Surgical excision is curative, although often delayed or not feasible, and patients frequently require intravenous dextrose. High-dose steroids (ie, prednisone 30-60mg daily) can be used, which promotes “big IGF-2” clearance. NICTH is likely under-recognized in patients with advanced malignancies. This diagnosis should be considered in those with refractory hypoglycemia, although management is challenging if tumor control cannot be achieved. Presentation: 6/1/2024

CD28 Costimulation Augments CAR Signaling in NK Cells via the LCK/CD3ζ/ZAP70 Signaling Axis.

Multiple factors in the design of a chimeric antigen receptor (CAR) influence CAR T-cell activity, with costimulatory signals being a key component. Yet, the impact of costimulatory domains on the downstream signaling and subsequent functionality of CAR-engineered natural killer (NK) cells remains largely unexplored. Here, we evaluated the impact of various costimulatory domains on CAR-NK cell activity, using a CD70-targeting CAR. We found that CD28, a costimulatory molecule not inherently present in mature NK cells, significantly enhanced the antitumor efficacy and long-term cytotoxicity of CAR-NK cells both in vitro and in multiple xenograft models of hematologic and solid tumors. Mechanistically, we showed that CD28 linked to CD3ζ creates a platform that recruits critical kinases, such as lymphocyte-specific protein tyrosine kinase (LCK) and zeta-chain-associated protein kinase 70 (ZAP70), initiating a signaling cascade that enhances CAR-NK cell function. Our study provides insights into how CD28 costimulation enhances CAR-NK cell function and supports its incorporation in NK-based CARs for cancer immunotherapy. Significance: We demonstrated that incorporation of the T-cell-centric costimulatory molecule CD28, which is normally absent in mature natural killer (NK) cells, into the chimeric antigen receptor (CAR) construct recruits key kinases including lymphocyte-specific protein tyrosine kinase and zeta-chain-associated protein kinase 70 and results in enhanced CAR-NK cell persistence and sustained antitumor cytotoxicity.

Glofitamab in Relapsed/Refractory Mantle Cell Lymphoma: Results From a Phase I/II Study.

Patients with relapsed/refractory (R/R) mantle cell lymphoma (MCL) have a poor prognosis. The phase I/II NP30179 study (ClinicalTrials.gov identifier: NCT03075696) evaluated glofitamab monotherapy in patients with R/R B-cell lymphomas, with obinutuzumab pretreatment (Gpt) to mitigate the risk of cytokine release syndrome (CRS) with glofitamab. We present data for patients with R/R MCL. Eligible patients with R/R MCL (at least one previous therapy) received Gpt (1,000 or 2,000 mg) 7 days before the first glofitamab dose (single dose or split over 2 days if required). Glofitamab step-up dosing was administered once a day on days 8 (2.5 mg) and 15 (10 mg) of cycle 1, with a target dose of 16 or 30 mg once every 3 weeks from cycle 2 day 1 onward, for 12 cycles. Efficacy end points included investigator-assessed complete response (CR) rate, overall response rate (ORR), and duration of CR. Of 61 enrolled patients, 60 were evaluable for safety and efficacy. Patients had received a median of two previous therapies (range, 1-5). CR rate and ORR were 78.3% (95% CI, 65.8 to 87.9) and 85.0% (95% CI, 73.4 to 92.9), respectively. In patients who had received previous treatment with a Bruton tyrosine kinase inhibitor (n = 31), CR rate was 71.0% (95% CI, 52.0 to 85.8) and ORR was 74.2% (95% CI, 55.4 to 88.1). CRS after glofitamab administration occurred in 70.0% of patients, with a lower incidence in the 2,000 mg (63.6% [grade ≥2, 22.7%]) versus 1,000 mg (87.5%; grade ≥2, 62.5%) Gpt cohort. Four adverse events led to glofitamab withdrawal (all infections). Fixed-duration glofitamab induced high CR rates in heavily pretreated patients with R/R MCL; the safety profile was manageable with appropriate support.

Successful Treatment of Monoclonal Immunotactoid Glomerulopathy Associated with Chronic Lymphocytic Leukemia Using Ibrutinib.

A 71-year-old woman developed nephrotic syndrome during 10-year follow-up for chronic lymphocytic leukemia. A renal biopsy sample analysis revealed IgG1-lambda-positive monoclonal immunotactoid glomerulopathy (mITG). The patient was treated with ibrutinib, a Bruton tyrosine kinase inhibitor, and complete renal remission was achieved after 24 months. ITG is a rare disease that is characterized by glomerular deposition. In particular, mITG, which presents immune deposits that exhibit light-chain restriction, is often associated with hematologic disorders. Most patients with mITG receive immunosuppressive therapy and/or chemotherapy; however, to our knowledge, there have been no reports of treatment with ibrutinib.

Chronic Myeloid Leukemia in Resource Limited Settings: Treatment Free Remission and Tyrosine Kinase Resistance

Chronic Myeloid Leukemia in Resource Limited Settings: Treatment Free Remission and Tyrosine Kinase Resistance

MerTK+ macrophages promote melanoma progression and immunotherapy resistance through AhR-ALKAL1 activation.

Despite our increasing understanding of macrophage heterogeneity, drivers of macrophage phenotypic and functional polarization in the microenvironment are not fully elucidated. Here, our single-cell RNA sequencing data identify a subpopulation of macrophages expressing high levels of the phagocytic receptor MER proto-oncogene tyrosine kinase (MerTK+ macrophages), which is closely associated with melanoma progression and immunotherapy resistance. Adoptive transfer of the MerTK+ macrophages into recipient mice notably accelerated tumor growth regardless of macrophage depletion. Mechanistic studies further revealed that ALK And LTK Ligand 1 (ALKAL1), a target gene of aryl hydrocarbon receptor (AhR), facilitated MerTK phosphorylation, resulting in heightened phagocytic activity of MerTK+ macrophages and their subsequent polarization toward an immunosuppressive phenotype. Specifically targeted delivery of AhR antagonist to tumor-associated macrophages with mannosylated micelles could suppress MerTK expression and improved the therapeutic efficacy of anti-programmed cell death ligand 1 therapy. Our findings shed light on the regulatory mechanism of MerTK+ macrophages and provide strategies for improving the efficacy of melanoma immunotherapy.