BACKGROUND:Antibody-drug conjugates (ADCs) combine a tumor antigen-specific monoclonal antibody with a cytotoxic payload via a linker, enabling selective delivery of cytotoxic agents to cancer cells while minimizing damage to healthy tissues. This approach has revolutionized cancer treatment; however, despite these advantages, resistance to ADCs has emerged as a significant barrier to long-term efficacy. METHODS:In this review, we summarize and analyze molecular pathways implicated in ADC resistance across multiple cancer types, including triple-negative breast cancer, non-small cell lung cancer, pancreatic cancer, and relapsed/refractory acute myeloid leukemia. We further examine emerging strategies to overcome resistance, with particular emphasis on combination therapies and the development of next-generation ADCs. RESULTS:Accumulating evidence indicates that identifying and targeting key resistance-associated pathways can expand the population of patients who benefit from ADC therapy and extend the therapeutic lifespan of these agents. We highlight representative preclinical studies that have elucidated resistance mechanisms and demonstrate potential approaches to restore or enhance ADC efficacy. CONCLUSION:Understanding and overcoming ADC resistance is essential as these agents continue to expand into new therapeutic settings. By bridging basic mechanistic insights with translational and preclinical evidence, this review provides a comprehensive framework for addressing ADC resistance and informs future strategies for optimizing cancer treatment.

Background:Obesity's impact on cancer treatment outcomes is poorly understood, especially in the context of immuno-oncology. This study explores how obesity and medical comorbidities are associated with overall survival in cancer patients receiving immune checkpoint inhibitors (ICIs). Additionally, considering the influence of sex on body composition in obesity, this study examines the relationship between sex, obesity, medical comorbidities, and survival. Methods:This cohort study involved 688 patients with metastatic cancer received ICIs as first- or second-line therapy. Obesity was assessed using body mass index (BMI). Cox proportional hazard models and Kaplan-Meier survival analysis were used to examine associations between predictors and overall survival. Results:Patients with higher BMI had longer overall survival, and hazard ratio (HR) for death was 0.83 (95% CI 0.73-0.95) for every 10 units increased in BMI. Additionally, patients belonged to the highest BMI group (≥ 40) had the lowest risk of death when comparing to patients with BMI 18.5 to < 30 with HR 0.58 (95% CI 0.37-0.90). In subgroup analysis, a significant association between high BMI and decreased HR for death was predominantly observed in the male cohort. In multivariate analysis, the prognostic value of BMI remained significant after adjusting for performance status, line of therapy, age-adjusted medical comorbidities, and cancer type. Conclusions:Obesity was associated with decreased mortality risk for cancer patients who had received ICIs. There could be a sex-dependent association between survival benefit and obesity.

BackgroundPatients with cancer-cachexia display a general resistance to Immune Checkpoint Inhibitor (ICI) therapy, as well as an elevated baseline catabolic clearance (CL) of ICIs, which serves as a prognostic indicator of overall survival independent of dose and drug exposure. Increased rate of ICI CL is present in the Lewis Lung Carcinoma (LLC) murine model of cachexia, but absent in the non-cachectic MC38 model. Fc-Gamma Receptors (FcγRs) bind the Fc portion of antibodies and can impact ICI anti-tumor efficacy.MethodsA pharmacokinetic study of human IgG1 (hIgG1) and hIgG1 with D265A (D265A) mutation, to abrogate all FcγR binding, was performed in mice that were either LLC tumor bearing (TB) or tumor free (TF). Immunofluorescence studies using fluorescence conjugated anti-human IgG were conducted to detect and localize infused hIgG1 in the mouse liver. To further investigate, FcγRIIb knockout mice were utilized in pharmacokinetic studies with hIgG.ResultsCL of both IgG1 and D265A significantly increased in LLC TB mice compared to TF controls, however the CL of D265A was significantly lower compared to hIgG1 in LLC TB mice. Immunofluorescence image of mouse livers portrays colocalization of the administered hIgG1 and FcγRIIb in liver sinusoidal endothelial cells (LSEC), as well as upregulated hepatic expression of FcγRIIb in LLC TB. However, hIgG1 CL was unaffected by whole body knockout of FcγRIIb.ConclusionReduced CL of D265A versus IgG1 in LLC TB mice, but not TF mice, suggests FcγRs are involved in catabolic CL of IgG antibodies in the presence of LLC tumors and cancer cachexia. This suggest that in the presence of LLC tumors, changes in FcγR expression and/or function lead to significantly altered antibody CL mediated by FcγR. This apparent role of FcγRs in antibody catabolism cannot be solely explained by FcγRIIb, but instead suggests the significance of other FcγRs in cachexia-associated increases in antibody CL.

Background: High-dose melphalan 140-200 mg/m2 (HDM) with autologous stem cell transplant (ASCT) is standard first-line treatment in multiple myeloma (MM), yet standard BSA-based dosing results in wide variation in systemic exposure (AUC). We developed a pharmacokinetic (PK)-guided dosing strategy using a 100 mg/m2 first dose, enabling real-time PK assessment and individualized adjustment for the second dose. We report final results of Phase A of our multi-center Phase 1 trial (NCT04483206, MyMel) evaluating feasibility and accuracy of this personalized approach. Methods: Patients received melphalan 100 mg/m2 on Day -3, and seven PK samples were collected and shipped overnight for LC-MS/MS analysis. Real-time AUC estimation using noncompartmental analysis (NCA) guided Day -1 dosing to achieve pre-specified AUC targets (13.5 or 14.5 mg × h/L). For comparison, post hoc Bayesian estimation using a nonlinear mixed effects (NLME) model was performed. Sparse sampling designs were evaluated using NONMEM. Results: All 20 patients successfully received PK-guided dosing, with Day -1 doses determined within 48 h. PK-guided dosing reduced AUC variability (CV 4.20-5.62%), with 19 of 20 achieving AUCs within ±10% of the target, compared to what would have been achieved by BSA dosing (CV 9.74-15.34%). NLME improved accuracy, particularly in patients with missing samples, and maintained performance using only four PK time points. Conclusions: This study demonstrates that PK-guided dosing is accurate and feasible with HDM-ASCT. NLME enhances accuracy and enables simplified sampling. Phase B will identify maximum tolerated systemic exposure of seven additional AUC cohorts using the NLME model and a four-sample design.

e15041 Background: Decreased baseline and cycle 1 (C1) serum albumin (ALB) predicts shorter overall survival (OS) in pts with NSCLC treated with IgG based immune checkpoint inhibitors (ICIs) but not in pts on ICI + chemotherapy. Decreased ALB may serve as a marker of hyper catabolism associated with cancer cachexia and elevated clearance (CL) of IgG drugs. It is unknown if ALB associates with OS in pts treated with antibody drug conjugates (ADCs), which combine IgG and chemotherapy. In this single-center retrospective analysis, we aimed to assess ALB and OS association. Methods: 601 cancer pts who received ADC, with at least one pretreatment and one on-treatment (C1) ALB value were included. Normal ALB was ≥ 3.5 g/dL per institution cut-off. In a subset of pts with pretreatment ALB measured within 30 days prior to start of ADC (n = 503), ALB percent change was calculated relative to the C1 value. ALB change was categorized as Increase/No change/Decrease and ( > 0%, 0% to –5%, –5% to –10%, < –10%). OS was defined as time from first ADC dose to death/censoring at most recent contact. Cox proportional hazards regression assessed ALB percent change vs. OS, adjusted for ADC and cancer type. Effect modification by ADC and cancer was evaluated with interaction terms (e.g. ADC x ALB change). Kaplan-Meier plots were used to visualize differences in OS. Results: In the full dataset (n = 601), pretreatment and C1 ALB were strongly associated with OS. Pts with normal (n = 490) vs. low ( < 3.5 g/dL, n = 111) C1 ALB had median OS of 31 mo vs. 9.8 mo, respectively (p < 0.0001). Among pts with relevant pre-treatment ALB (n = 503), pts with ALB increase had median OS of 29.3 mo, while pts with 0 – 5%, 5-10% or ≥10% decrease had median OS of 23.4 mo, 17.7 mo, and 12.1 mo, respectively ( p < 0.001). In multivariable analysis, each 10% ALB increase associated with 22% reduction in hazard of death (HR = 0.78, 95% CI 0.67–0.92). Compared with pts experiencing ≥10% ALB decrease, those with smaller decrease or increase had significantly lower hazards (adjusted HRs 0.45–0.49, all p < 0.001); highlighting the strong association of large ALB drop on survival. Borderline and significant interactions were observed comparing ALB (% change) vs cancer type (p = 0.06) and ALB change (3 categories) vs ADC type (p = 0.046), respectively. Conclusions: Early ALB change was independently associated with OS in cancer pts receiving ADCs, suggesting it may serve as an early indicator of mechanisms underlying IgG-based therapy resistance. Given known link between ALB and CL of IgG-based drugs, further investigation into the CL patterns, toxicities and outcomes of pts treated with ADCs is warranted. Age; Male(n), Female (n) 58 (24–89); 91, 510 Breast cancer, n (%) 402 (67) Non-breast, n (%) 199 (33) Advanced stage (3 - 4), n (%) 231 (38) Stage ≤ 2, n (%) 284 (47) Stage unknown, n (%) 86 (14) Trastuzumab Emtansine, n (%) 210 (35) Trastuzumab Deruxtecan, n (%) 147 (25) Enfortumab Vedotin, n (%) 91 (15) Other ADC, n (%) 153 (26)

Abstract Background: Anaplastic thyroid carcinoma (ATC) is a rare and highly aggressive malignancy. ATC can occur de novo, but accumulating pathological and genomic evidence suggests that a subset may arise through progressive dedifferentiation of pre-existing differentiated thyroid carcinoma (DTC), most commonly papillary thyroid carcinoma (PTC). Supporting this concept, coexistent PTC has been reported in approximately 20-30% of ATC cases, and genomic studies indicate that additional somatic alterations—such as TERT promoter and TP53 mutations—may drive this transition. However, the molecular mechanisms underlying this dedifferentiation process remain poorly understood. To address this gap, we compared gene expression profiles between well-differentiated PTC regions and undifferentiated ATC regions within the same tumors. Methods: RNA was extracted from well-differentiated and undifferentiated regions of the same tumor specimens (FFPE) obtained from six ATC cases. After RNA extraction, RNA libraries were prepared and sequenced using the Illumina NovaSeq 6000 platform, and comparative gene expression analysis was performed. To evaluate the impact of FOXD1 (Forkhead Box D1) on chemosensitivity, siRNA-mediated knockdown was performed, and cell viability after doxorubicin or paclitaxel treatment was assessed using the CCK-8 assay in two ATC cell lines (OCUT-1C and OCUT-1F). To investigate the regulatory mechanism of FOXD1 expression, methylation analysis of the FOXD1 promoter region was performed by bisulfite sequencing in a PTC cell line (KTC-1), OCUT-1C, and OCUT-1F. Results: Gene expression and KEGG pathway analyses showed EMT activation in ATC. Among transcription factors upregulated in the undifferentiated regions, FOXD1 was consistently overexpressed and therefore selected for further investigation. TGF-β-induced EMT of KTC-1 cells increased the expression of FOXD1 and the EMT-related transcription factors SNAI1 and SNAI2. qRT-PCR analysis revealed that siRNA suppression of FOXD1 altered the expression of EMT-related genes (CDH1, CDH2, SNAI1, SNAI2), whereas knockdown of SNAI1/2 did not affect FOXD1 expression. In both OCUT-1C and OCUT-1F cell lines, FOXD1 suppression restored sensitivity to doxorubicin and paclitaxel. Bisulfite sequencing revealed that the FOXD1 promoter was demethylated in OCUT-1C and OCUT-1F compared to KTC-1. Conclusions: These findings suggest that FOXD1 contributes to the dedifferentiation process from PTC to ATC. Moreover, restoration of chemosensitivity upon FOXD1 knockdown indicates that FOXD1 could be a promising therapeutic target for ATC. Future studies will further validate FOXD1 expression in additional clinical samples and perform functional analyses using FOXD1-knockout cell lines. Citation Format: Aki Inase, Mitsuyoshi Hirokawa, Miyoko Higuchi, Naoyoshi Onoda, Takuya Higashiyama, Taiji Koyama, Shiro Kimbara, Masanori Teshima, Hironobu Minami, Ken-Ichi Nibu, Mitch A. Phelps, Naomi Kiyota. The role of FOXD1 in the anaplastic transformation of thyroid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2992.

Aspirin is one of the most commonly used medications in pregnancy, particularly for the prevention of hypertensive disorders. Despite aspirin's widespread use in pregnancy for preeclampsia prevention, its pharmacokinetics (PK) across all trimesters remain poorly characterized, complicating optimal dosing recommendations. To develop a pregnancy-specific physiologically based pharmacokinetic (PBPK) model for aspirin that could be individualized to patient-specific parameters, illustrating differences in aspirin PK across the different trimesters of pregnancy. A PBPK model was developed using GastroPlus (a mechanistically driven simulation software) for nonpregnant and pregnant people at each trimester of pregnancy. The nonpregnant PBPK model was first established and validated against existing data from healthy adult volunteers. Once validated, the model was adapted for pregnant people and verified using observed pharmacokinetic profiles. The simulated PK parameters of aspirin in pregnant and nonpregnant women closely matched the clinical observations reported in the literature, with fold errors ≤ 1.04 (less than 1.5 is considered an acceptable simulation model). The predicted systemic exposure (AUC0-24h) of salicylic acid (SA), the active metabolite of aspirin decreased throughout gestation, showing a reduction of approximately 20% at 10 weeks and 30% at 40 weeks. An increase in clearance was observed as gestation progressed. The model predicted a modest decrease of 10% in systemic exposure in pregnant women and a 20% increase in fetal exposure to SA as pregnancy progresses. A PBPK model using GastroPlus was developed to describe the PK and pharmacodynamics of aspirin in both pregnant and nonpregnant healthy adults.

Background: Pancreatic Ductal Adenocarcinoma (PDAC) has a dismal five-year survival rate of 13% and is closely associated with cachexia. Cancer cachexia is a multifactorial syndrome characterized by irreversible wasting of skeletal muscles, fat loss and systemic inflammation. While cachexia is known to confer resistance to immune checkpoint inhibition in several cancers, the bidirectional relationship between cachexia and the immune system in PDAC remains unclear, necessitating the development of novel preclinical models. Our laboratory has characterized a novel pancreatic cancer cachexia model in C57BL/6J mice by utilizing the pancreatic cancer cell line called KPCL-4 derived from KPC-LSIY mice (Kras(LSL-G12D/+)Tp53(LSL-R172H/+)Pdx1-Cre/R26(LSL-LSIY)). Methods: KPCL-4 cells were orthotopically injected into the pancreas of male and female C57BL/6J mice and hallmarks of cachexia were assessed at endpoint by measurement of tumor weight, terminal tumor-adjusted body weight, skeletal muscle, adipose tissue, liver and spleen masses, proteolytic markers and grip strength. Plasma cytokine and chemokine concentrations were quantified by Luminex assay and high-dimensional flow cytometry was used to investigate changes in tumor-infiltrating immune populations. Results: We observed a sex bias in cachexia presentation despite similar tumor weights in male and female mice, whereby males exhibited a >5% decrease in terminal tumor-adjusted body weight (p < 0.001), >50% fat loss (p < 0.001), upregulation of proteolytic markers in skeletal muscles (p < 0.01) and reduction in skeletal muscle mass (p < 0.05), function (p < 0.01) and cross-sectional area (p < 0.0001) whereas females demonstrated conserved skeletal muscle mass with 33% fat loss (p < 0.05), reduction in muscle cross-sectional area (p < 0.0001) and splenomegaly (p < 0.01). While intra-tumoral immune populations did not exhibit sex-specific differences, plasma cytokine concentrations were differentially upregulated in males and females, suggesting functional differences in immune cells as potent drivers of sex bias in KPCL-4-driven cachexia. Conclusions: The KPCL-4 orthotopic PDAC model exhibits prominent hallmarks of cachexia and serves as a novel platform for investigating the complex interplay between cancer cachexia and immunomodulation.

8648 Background: EGFR TKIs improve clinical outcomes for patients with EGFR-mutated NSCLC. However, they are not curative even when combined with chemotherapy or antibody-based therapies because of slow-cycling, drug-tolerant cells that persist due to transcriptional reprogramming. This inevitably leads to tumor resistance and disease progression. Our preclinical studies showed that EGFR-mutated NSCLC cells enter a persistent state in response to TKIs due to increased transcriptional activity of β-catenin. Treatment of mice bearing EGFR-mutated NSCLC xenografts with an EGFR TKI and a β-catenin inhibitor caused a greater depth and duration of response than treatment with an EGFR TKI alone, which improved overall survival (OS). We also observed that patients with EGFR-mutated NSCLC who had the greatest increase in serum levels of the secreted β-catenin transcriptional target PAI-1 following treatment with a TKI had significantly worse progression free survival (PFS). These data led us to conduct a single-arm phase Ib clinical trial (NCT04780568) that investigated osimertinib in combination with tegavivint, an inhibitor of β-catenin transcriptional activity. Methods: Patients with metastatic EGFR-mutated (exon 19 deletion or L858R) NSCLC who had not received prior treatment with an EGFR TKI were eligible. All participants received osimertinib 80mg daily and were enrolled to escalating dose levels of tegavivint, which was administered weekly IV for 16 weeks. The primary objectives were to assess the safety and tolerability of the combination and to determine the recommended phase 2 dose (RP2D) of tegavivint. Secondary objectives measured the objective response rate (ORR), median PFS, and OS. Results: Fifteen evaluable patients received treatment on the dose escalation portion of this study, including six patients at the highest dose level of tegavivint (8 mg/kg), which was determined to be the RP2D. No dose limiting toxicities nor drug-related serious adverse events occurred. The adverse events that were observed included hematologic, skin, and GI toxicities, consistent with the known osimertinib toxicity profile. Pharmacokinetic analysis showed a dose-dependent increase in the C max and AUC of tegavivint, and plasma levels of osimertinib were comparable to those seen historically when administered as a single agent. The ORR was 73% with 2 of 15 patients (13%) achieving a complete response. Median PFS was 20.6 months (95% CI: 7-32 months). OS data is still maturing. Conclusions: NCT04780568 showed that the combination of osimertinib and tegavivint was safe and tolerable as first-line therapy in patients with metastatic EGFR-mutated NSCLC. This novel combination has the potential to improve the depth and durability of response to EGFR TKIs, without significantly increasing toxicity, by targeting drug-tolerant persistence. Clinical trial information: NCT04780568 .

Purpose The neonatal Fc receptor (FcRn) protects IgG-based monoclonal antibodies (mAbs) from catabolism by direct binding within endosomes and facilitates their recycling to extracellular spaces. Elevated clearance of immune checkpoint inhibitors (ICIs) and other IgG-based mAbs is often observed in patients with cachexia phenotypes and is associated with worse outcomes. We sought to understand if FcRn's function is altered in cancer cachexia. Experimental design Clearance of IgGs with different FcRn-binding properties were evaluated in cachectic LLC tumor-bearing (TB) and non-cachectic tumor-free mice in both wild-type and FcRn knockout backgrounds. As macrophage depletion with liposomal clodronate affects IgG pharmacokinetics only in the absence of FcRn function, we compared IgG clearance in LLC-TB and TF mice with and without macrophage ablation to assess changes in FcRn's functional status in cachectic tumor-bearing mice. Results We noted that the induction of IgG clearance in the presence of a cachectic tumor was dampened by the lack of FcRn engagement in whole body FcRn knockout mice. As expected, clodronate administration did not significantly affect systemic clearance of FcRn-binding IgG, though it significantly reduced clearance of FcRn-null IgG. More importantly, these effects were consistent in both TF and TB cachectic contexts. Conclusions These results suggest that while FcRn accounts for a portion of the observed changes in IgG pharmacokinetics in cancer cachexia, the functional status of FcRn is not significantly different in healthy mice without tumors compared to those with LLC tumors and associated cachexia, which indicates the potential involvement of FcRn-independent mechanisms.

ABSTRACT Busulfan is commonly used in hematopoietic stem cell transplantation conditioning, with therapeutic drug monitoring (TDM) guiding dose adjustments to promote target exposure attainment. Published busulfan population pharmacokinetic (popPK) models vary in structure and covariates, and it is unclear how broadly applicable one popPK model is across different datasets and patient populations. A popPK model was developed from a retrospective busulfan PK dataset (N = 109 patients). Individual PK parameters were derived by maximum a posteriori (MAP) estimation in four additional datasets. Model-based and TDM-based dosing performance was assessed and compared with noncompartmental analysis and standard weight-based dosing across the five datasets. The model was subsequently used to evaluate minimal sampling schemes. A two-compartment popPK model with sex and body surface area as covariates reliably estimated PK parameters and AUCs across five datasets (N = 464), closely agreeing with NCA. In the original dataset, weight-based dosing would have achieved target AUC in 34% of patients, compared with 40% and 80% using model-based and TDM-based dosing, respectively. Across remaining datasets, model-based dosing performed comparably to weight-based dosing. Sampling could be reduced to four time points, and even a single late sample enabled accurate AUC estimation. The single busulfan popPK model demonstrated adequate generalizability and performed equally with weight-based dosing for achieving specified AUCs. The model could also be used for AUC determination using minimal sampling, though its performance declined in datasets where sampling and dosing schemes differed from the original dataset, highlighting limitations in applying one popPK model across diverse scenarios.

ABSTRACTBackgroundCancer cachexia is a debilitating syndrome characterized by irreversible losses in skeletal muscle mass, with or without losses in adipose tissue. Cancer cachexia is an underrecognized syndrome that impacts ~50% of all cancer patients and accounts for up to ~20% of all cancer deaths. Lung cancer remains one of the deadliest cancers in the United States with an estimated 137 000 deaths in the year 2021 alone. Lung cancer is highly comorbid with cancer cachexia. Pre‐clinical models are heavily relied upon to study both lung cancer and cancer cachexia; however, there is a need to develop novel models to study the relationship between the two diseases. We therefore characterized the cachexia phenotype in the CMT‐167 syngeneic lung cancer model.MethodsMale C57BL6/J mice, aged 8–10 weeks, were administered an intramuscular (IM) injection of either 0.5 × 106 CMT‐167 cells or vehicle. Clinically relevant features of cancer cachexia were assessed 23 days after CMT‐167 cell administration in tumour bearing mice by assessment of terminal skeletal muscle and adipose tissue mass, gastrocnemius myofiber cross sectional area (CSA), circulating biomarkers of cachexia, and skeletal muscle E3 ubiquitin ligase mRNA. A single intravenous dose pharmacokinetic study of pembrolizumab was completed to assess tumour status influence upon antibody pharmacokinetics.ResultsCompared to tumour free (TF) mice, we observed lower terminal tumour‐adjusted bodyweight, adipose tissue mass, gastrocnemius mass, quadriceps mass, and gastrocnemius myofiber CSA. CMT‐167 tumour bearing (TB) mice did not lose bodyweight relative to starting weight, but instead failed to gain as much weight as TF controls. CMT‐167 TB mice exhibited increased concentrations of circulating markers of cachexia and muscle wasting, such as IL‐6 and TNF‐α, although there was no difference in transcription of E3 ubiquitin ligases Trim63 (MuRF‐1) and Fbxo32 (atrogin‐1) in skeletal muscle compared to TF mice. CMT‐167 TB mice exhibited increased catabolic clearance (CL) of the human IgG4 anti‐PD‐1, pembrolizumab, agreeing with published literature showing increased CL of immune checkpoint inhibitors in cachectic populations. Comparing the IM CMT‐167 model to historical data with the well‐established IM Lewis Lung Carcinoma model, CMT‐167 TB mice displayed a less severe cachectic phenotype in terms of bodyweight and skeletal muscle effects.ConclusionsThe IM CMT‐167 model is a syngeneic lung cancer model of mild cachexia. CMT‐167 TB mouse is a novel model in which to study cancer cachexia induction, skeletal muscle atrophy and immune checkpoint inhibitor clearance mechanisms in the context of lung cancer.

Objectives: Abemaciclib, a selective inhibitor of cyclin-dependent kinase 4 and 6, and olaparib, a poly (ADP-ribose) polymerase (PARP) enzyme inhibitor, are used for cancer treatment. Early toxicity was observed in patients with recurrent platinum-resistant ovarian cancer in an ongoing trial evaluating combined abemaciclib and olaparib (NCT04633239). Since metabolism and transport pathways for abemaciclib and olaparib partially overlap, and since cycle 1 pharmacokinetic (PK) data suggested drug-drug interactions (DDI) in this patient population, we aimed to explore potential drug interaction mechanisms utilizing both population pharmacokinetic (PopPK) and physiologically-based PK (PBPK) modeling and simulation approaches.Methods: Olaparib 200 or 250 mg was administered alone BID for 7 days and then administered in combination with abemaciclib 50 mg BID starting day 8 with 28-day cycles. A nonlinear mixed-effects model was developed using NONMEM, and a PBPK model was developed using PK-sim®. Physicochemical and absorption, distribution, metabolism, and excretion data of both agents were obtained from literature, and additional model parameters were estimated using clinical data. For both modeling approaches, model evaluation was performed by comparing predicted plasma concentration-time profiles to the observed data. Results: Both the popPK and PBPK models properly captured the observed profiles of abemaciclib and olaparib through one cycle of treatment. Compared to historical data with abemaciclib alone, the population PK model indicated there was an approximately 70% increase in first-order absorption rate constant and approximately 20% decrease in both apparent volume of distribution and apparent clearance of abemaciclib when administered with olaparib. However, time-varying components had to be incorporated to improve fitting for Days 15 through 28 in both the PopPK and PBPK models. While time-varying clearance had previously been described for olaparib, inclusion of that alone did not account for observed changes in PK of both drugs. Furthermore, with the experimental data currently available, specific enzyme and transporter contributions to the observed DDI could not be assigned.Conclusions: The developed PK models adequately described the observed plasma concentrations of abemaciclib and olaparib when initially combined in recurrent platinum-resistant ovarian cancer population, and with inclusion of additional time-varying components, the models could adequately describe PK behavior throughout cycle 1. The present models demonstrate underlying mechanisms, beyond those previously described, are involved in time-varying PK and DDI with combined abemaciclib and olaparib, though additional experimental data will be required to confirm the specific contributions of CYP and/or transporter-mediated DDI.Citations: [1] Chigutsa E, Kambhampati SRP, Karen Sykes A, Posada MM, van der Walt JS, Turner PK. Development and Application of a Mechanistic Population Modeling Approach to Describe Abemaciclib Pharmacokinetics. CPT Pharmacometrics Syst Pharmacol. 2020;9(9):523-533. doi:10.1002/psp4.12544

Objectives: Higher catabolic clearance (CL) of immune checkpoint inhibitors (ICIs) is a biomarker for less favorable outcomes, independent of drug exposure, in patients with cancer, thus leading to confounded exposure-response relationships. Patients with rapid mAb CL present with cancer cachexia phenotypes[1,2], though underlying mechanisms linking high mAb CL, poor drug response, and cancer cachexia are poorly understood. Our previous research demonstrates elevated CL of ICIs in patients can be replicated in mouse models of cancer cachexia, and the increased CL is partially, but not wholly, attributed to neonatal Fc receptor (FcRn) and Fc gamma receptors (FcγRs)[3]. Endogenous IgG can bind to FcRn or FcγRs, and they are associated with mAb PK [4,5]. This study aimed to develop a mechanistic PBPK model of mAb PK to integrate FcRn, FcγRs, and endogenous IgG, predict their combined roles in IgG mAb PK in mice, and compare model-predictions to observations from patients with cancer. Methods: A PBPK model was developed by incorporating FcγR-mediated internalization of mAb and endogenous IgG from an initial model adapted from literature[6]. Physiological parameters were obtained from literature, and ratio of FcγR and FcRn expression between healthy and cachectic mice was derived from in vitro observations. Other parameters were identified based on the PK data of human IgG1 (hIgG1), without and with engineering to disrupt binding to FcγR and FcRn, and observed level of serum endogenous IgG and albumin. Model simulation was conducted to explore impact on hIgG1 CL from altered expression of FcRn, FcγR, and circulating endogenous IgG. Clinical samples were from patients with non-small cell lung cancer or renal cell cancer who received ICIs. Results: The model successfully captured the PK of hIgG1s in healthy mice and cachectic mice. Our measurements of FcRn expression suggest slight decrease in mRNA but slight increase in protein levels in splenocytes and liver sinusoidal endothelial cells. When FcRn expression was assumed to be unchanged or changed minimally in the cachectic mice, simultaneous increases in the production rate of endogenous IgG and FcγR expression, similar to observations, in the cachectic mice were required to describe the CL elevation of wild-type hIgG1 compared to healthy mice. This also explained the smaller extent of CL elevation in the antibodies having disrupted binding to FcγR or FcRn. The model captured the measured baseline level of endogenous IgG. In clinical samples, there was a positive association between baseline endogenous IgG and CL of nivolumab, and this was consistent with the model-prediction. Conclusions: The model was able to capture the changes in the CL of IgG antibodies in cancer cachexia. Further development incorporating changes in immune cell populations will be investigated. The developed model will greatly enhance our ability to explore the complex mechanisms linking ICI CL and outcomes from ICI therapy.Citations: [1] Guo, Y. et al. Clinical Cancer Research 30 (2024): 942-958. [2] Turner, David C., et al. Clinical Cancer Research 24.23 (2018): 5841-5849. [3] Vu, Trang T., et al. Pharmacological research 199 (2024): 107048. [4] Oldham, Robert J., et al. Journal for Immunotherapy of Cancer 8.1 (2020). [5] Abe, Kazuki, et al. European Journal of Clinical Pharmacology 78.1 (2022): 77-87. [6] Shah, Dhaval K., and Alison M. Betts. Journal of pharmacokinetics and pharmacodynamics 39 (2012): 67-86.

An isotope-dilution bioanalytical assay for abemaciclib and its metabolites in combination with olaparib was developed and validated in human plasma K2 EDTA. For the quantitative assay, human plasma samples (or human plasma QC samples) were spiked with internal standard solution before a simple protein precipitation with methanol. The extract was injected onto a liquid chromatography-tandem mass spectrometry (LC-MS/MS) instrument where it was chromatographically separated by a polar end-capped reversed phase column and guard using gradient elution with water and methanol both modified with 0.2 % formic acid (v/v) as the mobile phases. The analytes and internal standards were measured by heated electrospray ionization (HESI) in positive polarity using selected reaction monitoring (SRM) on a triple quadrupole mass spectrometer. The assay was validated for linear ranges as follows: 0.4 - 1000 nM abemaciclib, 0.35 - 1000 nM M2 and M18, 0.5 - 1000 nM M20, and 0.75 - 1000 nM olaparib. The inter-day or between day precision for the quality controls (n = 18) was < 13% and the accuracy was +/- 12 %, for all analytes, including the lower limit of quantification (LLOQ). The intra-day or within day precision for the quality controls (n = 6) was <= 11 % and the accuracy was +/- 12% for low, mid, and high and < 19% at LLOQ. The recovery in human plasma was determined to be between 92% and 102% for all analytes spanning the linear range. The validated, bioanalytical quantitative assay was designed to measure abemaciclib, its metabolites, and olaparib for pharmacokinetic evaluation of patients in clinical trials for breast, brain, and ovarian cancers.

PurposePatients with cancer cachexia display a general resistance to immune checkpoint inhibitor (ICI) therapy, and baseline ICI catabolic clearance is a predictive indicator for overall survival, independent of dose and drug exposure. Fc-gamma (FcγRs) and neonatal Fc receptors (FcRn) play key roles in ICI clearance and efficacy, and we aimed to determine the impact of cachexia, independent of tumor, on immune cell populations and their Fc receptor (FcR) expression in patients and in murine models of cancer, cachexia, and cancer cachexia.Experimental designImmune cell populations and their FcR expression were measured in tumor-bearing and tumor-free mice, with/without cachexia, and from patients with non-small cell lung cancer (NSCLC) and renal cell carcinoma. These measures, upon splenocytes and peripheral blood mononuclear cells (PBMCs) in mice and humans respectively, were compared with baseline ICI drug clearance and cachexia phenotype.ResultsLeukocyte populations and FcγR in mouse splenocytes displayed distinct expressional patterns when comparing across tumor and cachexia status. Univariate analyses revealed several correlations between FcγR expression on patient PBMCs and both ICI clearance and cachexia phenotype. Notably, FcRn expression was unchanged or slightly elevated in tumor-bearing mice and did not correlate with ICI clearance in murine splenocytes or patient leukocytes. Furthermore, immune cell populations and FcR expression were different among tumor types but did not differ in splenocytes of tumor-free mice with Activin A/IL-6 induced cachexia when compared with vector controls.ConclusionsThese findings provide the first evidence that FcRs, critical for the efficacy and pharmacokinetics of many ICI and other IgG mAbs, are altered in a tumor-dependent manner. Furthermore, in the absence of a tumor, cachexia phenotype may not coincide with inflammation in the form of altered immune cell populations and elevated catabolic clearance of IgG mAbs, suggesting these features arise from properties intrinsic to the tumor.

BACKGROUND: Buprenorphine (BUP), a high-affinity partial mu-opioid receptor agonist, is the most prescribed medication for opioid use disorder in pregnancy in the US.1 Approximately half of neonates exposed to BUP in utero are diagnosed with neonatal opioid withdrawal syndrome (NOWS), but reliable tools to predict which neonates will develop NOWS are not currently available. Lacking accurate prediction tools, the American Academy of Pediatrics recommends prolonged inpatient observation of all neonates exposed to BUP in utero.2 Improved understanding of the biodistribution of buprenorphine and its metabolites may help develop prediction and diagnostic tools, thus enabling earlier discharge of neonates who are not at risk and interventions tailored to those at highest risk. OBJECTIVE: To determine the concentration of BUP and its metabolites in maternal and fetal samples and to investigate whether there is a relationship between BUP concentrations and NOWS. STUDY DESIGN: This is a retrospective cohort study utilizing samples from the Maternal-Fetal Medicine Preterm Birth Biomarker repository at The Ohio State University (IRB# 2013H0404). Matched maternal and fetal samples were collected from individuals taking BUP for treatment of opioid use disorder during pregnancy. All delivered at term (>= 37 weeks' gestation) via cesarean birth, participated in a multidisciplinary outpatient prenatal and addiction program, and were prescribed BUP 16 mg daily. We excluded individuals taking medications that have been associated with increased risk and severity of neonatal withdrawal, such as psychotropic medications. Samples were collected at the time of delivery and included maternal plasma, amniotic fluid, and umbilical cord blood. Concentrations of BUP, its biologically active metabolite norbuprenorphine (NBUP) and its metabolites glucuronide forms of buprenorphine (BUP-Gluc) and norbuprenorphine (NBUP-Gluc) were determined by liquid chromatography-mass spectrometry. The concentrations of BUP and its metabolites in maternal and fetal compartments were compared between neonates who developed NOWS, defined as withdrawal symptoms requiring pharmacotherapy, and those who did not. RESULTS: We identified 12 maternal-infant dyads meeting inclusion criteria. Five (42%) neonates born to mothers in the study developed NOWS. There were no significant differences in gestational age at delivery, frequency of small for gestational age, or other baseline characteristics between the 2 groups. There were no differences in maternal plasma concentrations of BUP or any of its metabolites between the 2 groups. BUP concentrations were higher in cord blood (mean (SD) 0.65 (0.19) vs 0.31 (0.13) ng/mL, P=.01) and amniotic fluid (0.64 (0.74) vs 0 ng/mL, P=.04) in neonates who developed NOWS, compared to those who did not (Table). NBUP was not detected in measurable quantities in the cord blood of any neonates. However, the concentrations of NBUP in amniotic fluid were higher in neonates who developed NOWS (2.01 (0.07) vs 0 ng/mL, P=.03, Figure). There were no differences in the concentrations of the metabolites BUP-Gluc and NBUP-Gluc in any of the compartments tested. CONCLUSIONS: Despite similar dosing and similar maternal plasma concentrations, NBUP concentrations in amniotic fluid and BUP concentrations in amniotic fluid and umbilical cord plasma were higher for infants who were later diagnosed with NOWS. These results suggest differential accumulation of the biologically active forms of the medication in the fetal compartment of those whose neonates ultimately developed NOWS. To our knowledge, this is the first study correlating the biodistribution of BUP and its metabolites in maternal-fetal compartments in humans with the development of NOWS. Based on previous retrospective studies, the risk and severity of NOWS do not correlate with maternal BUP dose, suggesting individual variation in pharmacokinetics plays a role.3-5 In our study, concentrations of BUP and NBUP were undetectable in the amniotic fluid of neonates who did not develop NOWS. Our novel findings suggest that testing amniotic fluid at delivery may allow triaging of which neonates are at risk of NOWS. Accurate risk stratification tools would enable earlier discharge of neonates who are not at risk of NOWS and targeted interventions for neonates at the highest risk.2 Further studies are needed to determine the underlying mechanisms of variation in biodistribution, and whether analysis of these specimens at delivery may help predict NOWS in buprenorphine-exposed neonates.

Objectives: In rapidly proliferating cancer cells, the de novo pyrimidine synthesis pathway is highly activated and enhances the tumor’s supply of pyrimidine nucleotides. HOSU-53 is under development as an orally bioavailable, small-molecule inhibitor of dihydroorotate dehydrogenase (DHODH), a mitochondrial enzyme that catalyzes the rate-limiting step of de novo pyrimidine nucleotide biosynthesis, conversion of dihydroorotate (DHO) to orotate1. Biological testing verified the efficacy of HOSU-53 in acute myeloid leukemia, multiple myeloma, small-cell lung cancer, melanoma, and other cancer cell lines. Our goals were to develop PK/PD models to scale across species and utilize plasma DHO exposure as a biomarker for both efficacy and on-target toxicity to target a safe, yet potentially effective starting dose in a first-in-human (FIH) trial.Methods: Plasma HOSU-53 and DHO concentration vs. time data were available from Good Laboratory Practice (GLP) and non-GLP pharmacokinetics (PK), toxicity, and efficacy studies in mice, rats, and beagle dogs. One-, two-, and three-compartment models for HOSU-53 PK were investigated and then linked to various PD models for DHO accumulation via DHODH inhibition, and a comprehensive dataset combining pharmacokinetics/pharmacodynamics (PK/PD) data across the three species was used for fitting and estimation of random and fixed effects, including allometric scale factors. Simulations of various dose regimens in humans have been made based on the final PK/PD model selected.Results: A 2-compartment model with first-order absorption and linear elimination with allometric factors adequately characterized the observed HOSU-53 PK profiles across species. DHO response to HOSU-53 was best characterized using a turnover model to capture the delay between plasma drug concentration and biomarker response. Compared with a previously developed physiologically based PK (PBPK) model, the PK/PD model is in good agreement in predicting human PK profiles. However, the HOSU-53 exposure-DHO response relationships did not scale well across species, suggesting yet unidentified mechanistic components may be required within the model.Conclusions: A translational modeling and simulation approach was used to identify a target dose range for the FIH study of a novel DHODH inhibitor using data from preclinical studies. Human simulations suggest an oral FIH starting dose of 5 mg QD will be safe and near the low end of the predicted efficacy range based on preclinical DHO exposure data. The discrepancy in PD predictions between species indicates better understanding of the pharmacological mechanisms of HOSU-53, DHODH, de novo pyrimidine synthesis, and DHO pharmacodynamics across species is needed to aid the development of HOSU-53 in humans.Citations: [1] Elgamal, O. A.; Fobare, S.; Vibhute, S.; Mehmood, A.; Vroom, D. C.; Johnson, M. L.; Stearns, B.; Lerma, J. R.; Truxall, J.; Stahl, E.; Carmichael, B.; Orwick, S. J.; Mims, A. S.; Curran, E.; Santhanam, R.; Tridandapani, S.; Phelps, M. A.; Xie, Z.; Coss, C. C.; Baker, S. D.; Patrick, J.; Ezzell, J. K.; Rai, J.; Pan, J.; Rai, S. N.; Stillwell, C.; Wunderlich, M.; Abdulrahim, M.; Goodwin, T. E.; Hilinski, G.; Bennett, C. E.; Hertlein, E.; Byrd, J. C. Pyrimidine Depletion Enhances Targeted and Immune Therapy Combinations in Acute Myeloid Leukemia. JCI Insight 2024, 9 (8). https://doi.org/10.1172/jci.insight.173646.

ABSTRACT Introduction Immune checkpoint inhibitors (ICIs) have revolutionized metastatic NSCLC treatment. Acute kidney injury (AKI) is a common complication of ICI‐based therapies, alone or with chemotherapy. This study investigates the association between early AKI and 12‐month survival among patients with metastatic NSCLC receiving front‐line ICI‐based treatment. Methods This retrospective study included metastatic NSCLC patients who received ICI‐based therapy (2017–2022). Early AKI was defined as a creatinine increase ≥ 1.5 times baseline within 21 days of the fourth cycle or last cycle if fewer than four were given. Clinical characteristics were compared using t‐tests and chi‐squared tests. Survival differences were assessed by Kaplan–Meier and log‐rank tests, with Cox models evaluating the association between AKI and 12‐month survival. Results Of the 310 patients, AKI occurred in 38 patients (12.6%), with 8 patients (2.3%) missing follow‐up creatinine data. The hazard ratio (HR) for death within 12 months for patients who developed early AKI was 1.733 (95% CI 1.060–2.835, p = 0.026). The highest rate of early AKI was seen in patients receiving pemetrexed, pembrolizumab, and carboplatin (16.7%), compared to 11.1% for pembrolizumab monotherapy and 4.5% for pembrolizumab with paclitaxel and carboplatin. Although patients who recovered renal function were more likely to continue immunotherapy, 12‐month survival rates did not significantly differ (52.2% vs. 46.7%). Conclusions Early AKI during pembrolizumab‐based treatment in metastatic NSCLC patients was associated with reduced 12‐month survival. These findings highlight the need for close monitoring and preventive strategies to manage AKI in this population.