Therapeutic Index Research Articles

Translational PK/PD framework for antibody-drug conjugates to inform drug discovery and development.

(171/200)ADCs represent a transformative class of medicine that combines the specificity of monoclonal antibodies with the potency of highly cytotoxic agents through linkers, aiming to enhance the therapeutic index of cytotoxic drugs. Given the complex molecular structures of ADCs, combining the molecular characteristics of small-molecule drugs and those of large-molecule biotherapeutics, there are several unique considerations when designing nonclinical-to-clinical PK/PD translation strategies.This complexity also demands a thorough understanding of the ADC's components-antibody, linker, and payload-to the overall toxicological, PK/PD, and efficacy profile. ADC development is a multidisciplinary endeavor requiring a strategic integration of nonclinical safety, pharmacology, and PK/PD modeling to translate from bench to bedside successfully.The ADC development underscores the necessity for a robust scientific foundation, leveraging advanced analytical and modeling tools to predict human responses and optimize therapeutic outcomes.This review aims to provide an ADC translational PK/PD framework by discussing unique aspects of ADC nonclinical to clinical PK translation, starting dose determination, and leveraging PK/PD modeling for human efficacious dose prediction and potential safety mitigation.

Population pharmacokinetics and pharmacodynamics of nasal glucagon in patients with type 1 or 2 diabetes.

The objective was to characterize the pharmacokinetics (PK) and pharmacodynamics (PD) of glucagon after injectable or nasal administration and confirm the appropriate therapeutic dose of nasal glucagon (NG) for adult patients. Six clinical studies with PK and five clinical studies with PD (glucose) data were included in the analysis. Doses ranging from 0.5 to 6 mg NG, and 0.5 to 1 mg injectable glucagon were studied. A total of 6284 glucagon and 7130 glucose concentrations from 265 individuals (patients and healthy participants) were available. Population PK/PD modeling was performed using NONMEM. Glucagon exposure and glucose response were simulated for patients administered various doses of NG to confirm the optimal dose. Glucagon PK was well-described with a single compartment disposition with first-order absorption and elimination processes. Bioavailability of NG relative to injectable glucagon was 16%. Exposure-response modeling revealed that lower baseline glucose was associated with higher maximum drug effect. The carry-over effect from prior insulin administration was incorporated into the model through a time-dependent increase in elimination rate of glucose. Simulations showed that more than 99% of hypoglycemic adult patients would experience treatment success, defined as an increase in blood glucose to ≥70 mg/dL or an increase of ≥20 mg/dL from nadir within 30 min after administration of NG 3 mg. The population PK/PD model adequately described the PK and PD profiles of glucagon after nasal administration. Modeling and simulations confirmed that NG 3 mg is the most appropriate dose for rescue treatment during hypoglycemia emergencies.

Exposure to Mycophenolic Acid and Its Clinical Response in an Indian Pediatric Population with Nephrotic Syndrome

Background: Children with nephrotic syndrome experience many side effects and frequent relapses when treated with steroids and other drugs. Mycophenolic acid (MPA) is one of the effective and least toxic drug for the treatment of nephrotic syndrome. This drug needs to be monitored for maximal efficacy and minimal toxicity. The therapeutic reference range for this drug is not established for the aforementioned patient population of Indian origin. Materials and Methods: In this observational study, children with nephrotic syndrome on mycophenolate mofetil were followed up for a minimum duration of three months. Following this, their clinical status (relapse/remission) was determined and the mycophenolate exposure was measured for over 12 hours. Results: A total of 34 participants were included, with 17 (50%) in relapse. Median MPA Area under the curve over 12 hours (AUC0–12h) (36.5 µg·h/ml) in the remission group differed significantly compared to that in the relapse group (17.2 µg·h/ml). Conclusion: Higher exposure to MPA AUC0–12h is associated with clinical remission of pediatric nephrotic syndrome.

Fake Xanax: Designer Emerging Benzodiazepine Epidemic Linked to Morbidity and Mortality a Narrative Review.

Etizolam is a thienodiazepine derivative which produces an anxiolytic effect similar to benzodiazepines such as alprazolam (Xanax). Like classic benzodiazepines, etizolam has a high affinity towards the GABAA receptor, and allosterically potentiates the effects of GABA resulting in neuronal hyperpolarization related to chloride influx. When taken in therapeutic doses, etizolam produces a similar effect to Xanax. Counterfeit Xanax tablets contain variable amounts of etizolam. Tablets with high amounts of etizolam can cause toxicity if ingested, especially when combined with other substances. When toxic symptoms occur in patients, they may include severe sedation, unconsciousness, and depression of the medullary respiratory center. In this regard, there is the potential for death. Additionally, the rise in fake Xanax tablets containing etizolam and other counterfeit medications has been exacerbated by the difference in regulations regarding these substances in different countries as well as the illegal drug trade. Healthcare providers may also play a role through the over- or underprescribing of certain medications. Thus, in order to combat the rise in counterfeit medications such as fake Xanax, international cooperation, regulation, and enforcement of laws pertaining to the manufacture, prescription, and distribution of these substances are needed.

A Tissue Distribution Study of Propafenone in an Intentional Fatal Poisoning Case

Propafenone (PPF) belongs to the class 1C antiarrhythmics and can cause electrocardiogram-associated adverse/toxic effects. Cases of PPF intoxication are rarely investigated. We developed a novel and selective GC-MS/MS method for the determination of PPF and its tissue distribution in an intentional fatal poisoning case, which is applicable to PPF quantification in the range of therapeutic to lethal concentrations in complex post-mortem samples. A simple and effective sample pretreatment was applied to all analyzed samples. PPF was determined without the need for dilution, even in highly complex samples containing a wide range of analyte concentrations. Quantification was performed using the standard addition method, developed and validated according to the ICH M10 guidelines. The obtained results indicated that the PPF concentration in the serum from blood taken while alive, before therapy, was the highest ever reported in the literature. Despite the intensive therapy after the patients’ admission, the PPF concentrations in the lungs, spleen, femoral blood and cardiac blood were fatal or abnormally high. On the other hand, the concentrations in the liver and skeletal muscle were lower or approximately the same as observed in cases with therapeutic doses. To the best of our knowledge, the distribution of PPF has not been investigated in fatal intoxication cases and can be helpful in clinical or forensic toxicology.

Pharmacodynamic monitoring by residual gene expression of the nuclear factor of activated T cell-regulated genes in lung transplant recipients and its correlation with tacrolimus blood levels

IntroductionTrough blood levels (C0) of tacrolimus are used to adjust drug dosage, but they do not consistently correlate with clinical outcomes. Measurement of residual gene expression of nuclear factor of activated T cell (NFAT)-regulated genes (NFAT-RGE) has been proposed as a pharmacodynamic biomarker to assess the degree of immunosuppression in certain solid organ transplantations, but little is known regarding lung transplant recipients (LTR). Our primary objective is to correlate tacrolimus blood levels with NFAT-RGE.MethodsNFAT-RGE and tacrolimus C0 and peak (C1.5) levels were determined in 42 patients at three, six and 12 months post-transplantation.ResultsTacrolimus C0 did not exhibit a correlation with NFAT-RGE, whereas C1.5 did. Besides, over 20% of measurements indicated high levels of immunosuppression based on the below 30% NFAT-RGE threshold observed in many studies. Among those measurements within the therapeutic range, 19% had an NFAT-RGE<30%.ConclusionConsequently, a subset of patients within the tacrolimus therapeutic range may be more susceptible to infection or cancer, potentially benefiting from NFAT-RGE and tacrolimus peak level monitoring to tailor their dosage. Further quantitative risk assessment studies are needed to elucidate the relationship between NFAT-RGE and the risk of infection, cancer, or rejection.

The reverse transcriptase inhibitor 3TC modulates hippocampal transcriptome signatures of inflammation in tauopathy model mice

Reducing neuroinflammation, a key contributor to brain aging and neurodegenerative diseases, is a promising strategy for improving cognitive function in these settings. The FDA-approved nucleoside reverse transcriptase inhibitor 3TC (Lamivudine) has been reported to improve cognitive function in old wild-type mice and multiple mouse models of neurodegenerative disease, but its effects on the brain have not been comprehensively investigated. In the current study, we used transcriptomics to broadly characterize the effects of long-term supplementation with a human-equivalent therapeutic dose of 3TC on the hippocampal transcriptome in male and female rTg4510 mice (a commonly studied model of tauopathy-associated neurodegeneration). We found that tauopathy increased hippocampal transcriptomic signatures of neuroinflammation/immune activation, but 3TC treatment reversed some of these effects. We also found that 3TC mitigated tauopathy-associated activation of key transcription factors that contribute to neuroinflammation and immune activation, and these changes were related to improved recognition memory performance. Collectively, our findings suggest that 3TC exerts protective effects against tauopathy in the hippocampus by modulating inflammation and immune activation, and they may provide helpful insight for ongoing clinical efforts to determine if 3TC and/or related therapeutics hold promise for treating neurodegeneration.

Efficacy of human prothrombin complex concentrate in the treatment of warfarin overdose in patients receiving warfarin for mechanical heart valve replacement.

Warfarin, a widely utilized anticoagulant, is paramount for preventing thromboembolic events in patients with mechanical heart valve replacements. However, its narrow therapeutic index can lead to over-anticoagulation and overdose, resulting in serious health risks. This study examines the efficacy of human prothrombin complex concentrate (PCC) in managing warfarin overdose, in comparison with traditional treatments. A retrospective analysis was conducted on 162 adults who presented with warfarin overdose (INR > 5.0) at a tertiary care hospital between 2016 and 2020. Participants were divided into 2 groups-those treated with PCC (n = 57) and those treated with conventional methods (n = 105), including vitamin K and fresh frozen plasma. The primary outcome was the rate of reaching the target (International Normalized Ratio) INR within 24 hours. Secondary outcomes included transfusion requirements, thromboembolic events, adverse reactions, 30-day mortality, and length of hospital stay. PCC demonstrated significant efficacy, with 89.5% of patients achieving the target INR within 24 hours, compared to 64.8% in the control group (P < .05). The PCC group also had reduced transfusion requirements and a shorter average hospital stay. There was no significant difference in thromboembolic events or adverse reactions between the 2 groups, and the reduced 30-day mortality in the PCC group was not statistically significant. Human prothrombin complex concentrate is associated with rapid reaching the target INR, decreased transfusion needs, and shortened hospitalization, making it a promising option for warfarin overdose management. While the results are encouraging, larger, multicenter, randomized controlled trials are necessary to further validate these findings and optimize PCC administration protocols.

Cenobamate Plasma Levels in Patients with Epilepsy: Correlation with Efficacy and Tolerability?

Objective: Cenobamate is approved by the European Medicine Agency for the treatment of adult patients with epilepsy (PWEs) with ongoing focal-onset seizures despite appropriate treatment with at least two established antiseizure medications. Pivotal trials and post-marketing real-world observational studies suggest high efficacy with unusually high seizure-free rates. The authors sought to investigate the plasma levels of cenobamate under steady-state conditions in seizure-free versus non-responding PWEs, and in PWEs who experienced adverse events versus those who did not. Methods: Blood samples were collected from adult PWEs who were treated with adjunct cenobamate under steady-state conditions. Daily doses, concomitant medications, efficacy, and tolerability were assessed. The plasma cenobamate levels of seizure-free versus non-responding PWEs and between PWEs with and those without clinical adverse events were compared. Results: Samples from 101 PWEs were included. Thirty-six PWEs were seizure-free and 65 were non-responders. In 31 PWEs, adverse events were apparent, whereas in the remaining 70, no tolerability issues were reported. A linear correlation was found between the daily doses (range: 100 mg–400 mg) and the plasma levels (3.8 mg/L–54.6 mg/L). Neither the daily doses nor the plasma levels differed significantly between the investigated subgroups. The main reason for this result was that the individual therapeutic ranges varied widely: seizure freedom and adverse effects were observed alongside low doses and plasma levels in some PWEs. Conversely, there were examples of PWEs who did not respond or who reported no tolerability issues at high doses or plasma levels. Conclusions: To evaluate the individual therapeutic range and to better understand the influence of other drugs in cases where concomitant medications are used, the therapeutic drug monitoring of cenobamate may be useful. A general therapeutic range cannot be defined.

Antibody–drug conjugates in the treatment of lymphoid neoplasms

SummaryAntibody-drug conjugates (ADCs) are a new class of monoclonal antibodies with the characteritic to specifically target tumor cells and to deliver a cytotoxic drug directly to the target cell thereby minimising side effects and improving the therapeutic index. In recent years, many new ADCs have been approved and are established therapeutic tools in lymphoma treatment.

Mini-Beam Spatially Fractionated Radiation Therapy for Whole-Brain Re-Irradiation—A Pilot Toxicity Study in a Healthy Mouse Model

For patients with recurrent brain metastases, there is an urgent need for a more effective and less toxic treatment approach. Accumulating evidence has shown that spatially fractionated radiation therapy (SFRT) is able to provide a significantly higher therapeutic ratio with lower toxicity compared to conventional radiation using a uniform dose. The purpose of this study was to explore the potential low toxicity benefit of mini-beam radiotherapy (MBRT), a form of SFRT, for whole-brain re-irradiation in a healthy mouse model. Animals first received an initial 25 Gy of uniform whole-brain irradiation. Five weeks later, they were randomized into three groups to receive three different re-irradiation treatments as follows: (1) uniform irradiation at 25 Gy; (2) MBRT at a 25 Gy volume-averaged dose (106.1/8.8 Gy for peak/valley dose, 25 Gy-MBRT); and (3) MBRT at a 43 Gy volume-averaged dose (182.5/15.1 Gy for peak/valley dose, 43 Gy-MBRT). Animal survival and changes in body weight were monitored for signs of toxicity. Brains were harvested at 5 weeks after re-irradiation for histologic evaluation and immunostaining. The study showed that 25 Gy-MBRT resulted in significantly less body weight loss than 25 Gy uniform irradiation in whole-brain re-irradiation. Mice in the 25 Gy-MBRT group had a higher level of CD11b-stained microglia but also maintained more Ki67-stained proliferative progenitor cells in the brain compared to mice in the uniform irradiation group. However, the high-dose 43 Gy-MBRT group showed severe radiation toxicity compared to the low-dose 25 Gy-MBRT and uniform irradiation groups, indicating dose-dependent toxicity. Our study demonstrates that MBRT at an appropriate dose level has the potential to provide less toxic whole-brain re-irradiation. Future studies investigating the use of MBRT for brain metastases are warranted.

Bivalirudin Monitoring in Pediatric Ventricular Assist Device and Extracorporeal Membrane Oxygenation: Analysis of Single-Center Retrospective Cohort Data 2018-2022.

The activated partial thromboplastin time (aPTT) is the most frequently used monitoring assay for bivalirudin in children and young adults on mechanical circulatory support including ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO). However, intrinsic variability of the aPTT complicates management and risks bleeding or thrombotic complications. We evaluated the utility and reliability of a bivalirudin-calibrated dilute thrombin time (Bival dTT) assay for bivalirudin monitoring in this population. Retrospective analysis of clinical data (including aPTT, dilute thrombin time [dTT]) and results of residual plasma samples from VAD patients were assessed in two drug-calibrated experimental assays. One assay (Bival dTT) was validated for clinical use in VAD patients, and subsequently used by clinicians in ECMO patients. Pearson correlation and simple linear regression were used to determine R2 correlation coefficients between the different laboratory parameters using Statistical Package for Social Sciences (Armonk, NY). ICUs at Cincinnati Children's Hospital Medical Center. Children on VAD or ECMO support anticoagulated with bivalirudin. None. One hundred fifteen plasma samples from 11 VAD patients were analyzed. Both drug-calibrated experimental assays (anti-IIa and Bival dTT) showed excellent correlation with each other (R2 = 0.94) and with the dTT (R2 = 0.87), but poor correlation with aPTT (R2 = 0.1). Bival dTT was selected for validation in VAD patients. Subsequently, clinically ordered results (105) from 11 ECMO patients demonstrated excellent correlation between the Bival dTT and the standard dTT (R2 = 0.86) but very poor correlation with aPTT (R2 = 0.004). APTT is unreliable and correlates poorly with bivalirudin's anticoagulant effect in ECMO and VAD patients. A drug-calibrated Bival dTT offers superior reliability and opportunity to standardize results across institutions. Additional studies are needed to determine an appropriate therapeutic range and correlation with clinical outcomes.

Battling Salmonella enteritidis infections: integrating proteomics and in vivo assessment of Galla Chinensis tannic acid

Salmonella infections pose a significant threat to animal and human health. Phytochemicals present a potential alternative treatment. Galla chinensis tannic acid (GCTA), a hydrolyzable polyphenolic compound, inhibits bacterial growth and demonstrates potential as an alternative or supplement to antibiotics to prevent Salmonella infections. However, little is known about the antimicrobial mechanism of GCTA against Salmonella. Here, we revealed 456 differentially expressed proteins upon GCTA treatment, impacting pathways related to DNA replication, repair, genomic stability, cell wall biogenesis, and lipid metabolism using TMT-labeled proteomic analysis. TEM analysis suggested altered bacterial morphology and structure post-treatment. A Salmonella-infected-mouse model indicated that GCTA administration improved inflammatory markers, alleviated intestinal histopathological alterations, and reduced Salmonella enterica serovar Enteritidis (S. Enteritidis) colonization in the liver and spleen of Salmonella-infected mice. The LD50 of GCTA was 4100 mg/kg with an oral single dose, vastly exceeding the therapeutic dose. Thus, GCTA exhibited antibacterial and anti-infective activity against S. Enteritidis. Our results provided insight into the molecular mechanisms of these antibacterial effects, and highlights the potential of GCTA as an alternative to antibiotics.

Enhancing the stability and therapeutic potential of the antimicrobial peptide Feleucin-K3 against Multidrug-Resistant a. Baumannii through rational utilization of a D-amino acid substitution strategy

Antimicrobial peptides (AMPs), which have a low probability of developing resistance, are considered the most promising antimicrobial agents for combating antibiotic resistance. Feleucin-K3 is an amphiphilic cationic AMP that exhibits broad-spectrum antimicrobial activity. In our previous research, the first phenylalanine residue was identified as the critical position affecting its biological activity. Here, a series of Feleucin-K3 analogs containing hydrophobic D-amino acids were developed, leveraging the low sensitivity of proteases to unnatural amino acids and the regulatory effect of hydrophobicity on antimicrobial activity. Among them, K-1dF, which replaced the phenylalanine of Feleucin-K3 with its enantiomer (D-phenylalanine), exhibited potent antimicrobial activity with a therapeutic index of 46.97 and MICs between 4 to 8 μg/ml against both sensitive and multidrug-resistant Acinetobacter baumannii. The introduction of D-phenylalanine increased the salt tolerance and serum stability of Feleucin-K3. Moreover, K-1dF displayed a rapid bactericidal effect, a low propensity to develop resistance, and a synergistic effect when combined with antibiotics. More importantly, it exhibited considerable or superior efficacy to imipenem against pneumonia and skin abscess infection. In brief, the K-1dF obtained by simple and effective modification strategy has emerged as a promising candidate antimicrobial agent for tackling multidrug-resistant Acinetobacter baumannii infections.

Design, synthesis, and evaluation of N1,N3-dialkyldioxonaphthoimidazoliums as antibacterial agents against methicillin-resistant Staphylococcus aureus

Increasing antibiotic resistance of bacterial pathogens poses a serious threat to human health worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is among the most deleterious bacterial pathogens owing to its multidrug resistance, necessitating the development of new antibacterial agents against it. We previously identified a novel dioxonaphthoimidazolium agent, c5, with moderate antibacterial activity against MRSA from an anticancer clinical candidate, YM155. In this study, we aimed to design and synthesize several novel cationic amphiphilic N1,N3-dialkyldioxonaphthoimidazolium bromides with enhanced lipophilicity of the two side chains in the imidazolium scaffold and improved antibacterial activities compared to those of c5 against gram-positive bacteria in vitro and in vivo. Our new antibacterial lead, N1,N3-n-octylbenzyldioxonaphthoimidazolium bromide (11), exhibited highly potent antibacterial activities against various gram-positive bacterial strains (MICs: 0.19–0.39 μg/mL), including MRSA, methicillin-sensitive S. aureus, and Bacillus subtilis. Moreover, antibacterial mechanism of 11 against MRSA based on the generation of reactive oxygen species (ROS) was evaluated. Although compound 11 exhibited cytotoxic effects in vitro and lacked a therapeutic index against the HEK293 and HDFa mammalian cell lines, it exhibited low toxicity in the Drosophila animal model. Remarkably, 11 exhibited better in vivo antibacterial efficacy than c5 and the clinically used antibiotic, vancomycin, in SA3-infected Drosophila model. Moreover, the development of bacterial resistance to 11 was not observed after 16 consecutive passages. Therefore, rational design of antibacterial cationic amphiphiles based on ROS-generating pharmacophores with optimized lipophilicity can facilitate the identification of potent antibacterial agents against drug-resistant infections.

Therapeutic doses of ketamine acutely attenuate the aversive effect of losses during decision-making.

The discovery of rapid-acting antidepressant, ketamine has opened a pathway to a new generation of treatments for depression, and inspired neuroscientific investigation based on a new perspective that non-adaptive changes in the intrinsic excitatory and inhibitory circuitry might underlie the pathophysiology of depression. Nevertheless, it still remains largely unknown how the hypothesized molecular and synaptic levels of changes in the circuitry might mediate behavioral and neuropsychological changes underlying depression, and how ketamine might restore adaptive behavior. Here, we used computational models to analyze behavioral changes induced by therapeutic doses of ketamine, while rhesus macaques were iteratively making decisions based on gains and losses of tokens. When administered intramuscularly or intranasally, ketamine reduced the aversiveness of undesirable outcomes such as losses of tokens without significantly affecting the evaluation of gains, behavioral perseveration, motivation, and other cognitive aspects of learning such as temporal credit assignment and time scales of choice and outcome memory. Ketamine's potentially antidepressant effect was separable from other side effects such as fixation errors, which unlike outcome evaluation, was readily countered with strong motivation to avoid errors. We discuss how the acute effect of ketamine to reduce the initial impact of negative events could potentially mediate longer-term antidepressant effects through mitigating the cumulative effect of those events produced by slowly decaying memory, and how the disruption-resistant affective memory might pose challenges in treating depression. Our study also invites future investigations on ketamine's antidepressant action over diverse mood states and with affective events exerting their impacts at diverse time scales.

Therapeutic doses of ketamine acutely attenuate the aversive effect of losses during decision-making

The discovery of rapid-acting antidepressant, ketamine has opened a pathway to a new generation of treatments for depression, and inspired neuroscientific investigation based on a new perspective that non-adaptive changes in the intrinsic excitatory and inhibitory circuitry might underlie the pathophysiology of depression. Nevertheless, it still remains largely unknown how the hypothesized molecular and synaptic levels of changes in the circuitry might mediate behavioral and neuropsychological changes underlying depression, and how ketamine might restore adaptive behavior. Here, we used computational models to analyze behavioral changes induced by therapeutic doses of ketamine, while rhesus macaques were iteratively making decisions based on gains and losses of tokens. When administered intramuscularly or intranasally, ketamine reduced the aversiveness of undesirable outcomes such as losses of tokens without significantly affecting the evaluation of gains, behavioral perseveration, motivation, and other cognitive aspects of learning such as temporal credit assignment and time scales of choice and outcome memory. Ketamine’s potentially antidepressant effect was separable from other side effects such as fixation errors, which unlike outcome evaluation, was readily countered with strong motivation to avoid errors. We discuss how the acute effect of ketamine to reduce the initial impact of negative events could potentially mediate longer-term antidepressant effects through mitigating the cumulative effect of those events produced by slowly decaying memory, and how the disruption-resistant affective memory might pose challenges in treating depression. Our study also invites future investigations on ketamine’s antidepressant action over diverse mood states and with affective events exerting their impacts at diverse time scales.

Abstract PO2-19-08: INAVO121: Phase III study of inavolisib + fulvestrant vs alpelisib + fulvestrant in patients with hormone receptor-positive, HER2-negative, PIK3CA-mutated locally advanced or metastatic breast cancer

Abstract BACKGROUND Standard-of-care (SoC) endocrine therapy (ET) for patients (pts) with hormone receptor-positive, HER2-negative, PIK3CA-mutated locally advanced or metastatic breast cancer (HR+, HER2–, PIK3CA-mut LA/mBC) was transformed by combinations with cyclin-dependent kinase 4/6 inhibitors (CDK4/6is); a CDK4/6i-based combination is approved in high-risk early BC. However, in most pts, mechanisms of resistance that emerge during or after treatment with a CDK4/6i and ET combination lead to relapse/disease progression. Dysregulating mutations in PIK3CA, occurring in ~40% of HR+, HER2– BCs, represent a common mechanism of resistance to CDK4/6is and ET combinations. Alpelisib (ALP; a selective PI3Kα inhibitor; PI3Kαi) + fulvestrant (FUL) is approved for pts with HR+, HER2–, PIK3CA-mut LA/mBC, but its widespread implementation in clinical practice has been challenging. As such, there is a significant need to develop PI3Kαis with a better therapeutic index. Inavolisib (INAVO) is a highly potent and selective PI3Kαi that also facilitates the degradation of mutated PI3Kα isoform. INAVO has demonstrated manageable safety/tolerability, alone and in combination with SoC treatments in HR+, HER2–, PIK3CA-mut LA/mBC. Moreover, an ongoing Phase I trial showed that INAVO + FUL elicited encouraging preliminary antitumor activity in heavily pretreated pts, including a CDK4/6i-based regimen. TRIAL DESIGN INAVO121 is a Phase III, randomized, open-label study. Pts are randomized 1:1 to receive INAVO (9 mg oral daily; PO QD) + FUL (500 mg intramuscularly on Days [D] 1 and 15 of Cycle 1, then D1 of subsequent cycles), or ALP (300 mg PO QD) + FUL. Randomization is stratified by visceral disease (yes vs no) and prior CDK4/6i therapy (adjuvant vs metastatic setting). Pts will receive treatment until disease progression or unacceptable toxicity. ELIGIBILITY CRITERIA Pts have HR+, HER2–, PIK3CA-mut LA/mBC (confirmed by circulating-tumor DNA or tumor tissue), adequate hematologic and organ function, and disease progression after or during treatment with a CDK4/6i-based regimen. Up to two prior lines of systemic therapy in LA/mBC, including one line of chemotherapy, are allowed. AIMS The primary endpoint is progression-free survival (PFS) by blinded independent central review (BICR). Secondary endpoints include overall survival, BICR-objective response rate, BICR-best overall response, BICR-duration of response, BICR-clinical benefit rate, safety, tolerability, pt-reported outcomes, and pharmacokinetics. STATISTICAL METHODS A stratified log-rank test at an overall 0.05 significance level (two-sided) will be used for the primary endpoint analysis. Median PFS will be estimated using Kaplan–Meier methodology. An independent data monitoring committee will be in place for safety and efficacy. ACCRUAL The study is open for enrollment and has randomized four pts; the study is targeting 400 pts at ~200 sites globally. CONTACT INFORMATION For more information or to refer a patient, email global.rochegenentechtrials@roche.com or call 1-888-662-6728 (USA only). Clinicaltrials.gov number NCT05646862. This abstract was originally presented at ASCO 2023 (TPS1123). Citation Format: Dejan Juric, Kevin Kalinsky, Seock-Ah Im, Eva Ciruelos, Giampaolo Bianchini, Carlos Barrios, William Jacot, Peter Schmid, Sherene Loi, Hope Rugo, Veronica Craine, Katherine Hutchinson, Aulde Flechais, Eirini Thanopoulou, Nadia Harbeck. INAVO121: Phase III study of inavolisib + fulvestrant vs alpelisib + fulvestrant in patients with hormone receptor-positive, HER2-negative, PIK3CA-mutated locally advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-19-08.

Abstract PO3-06-08: Epithelial to Mesenchymal Transition Confers Sensitivity to Cytotoxic Agent Ophiobolin A via Alterations in Mitochondrial Function and Metabolic Pathways

Abstract Epithelial to Mesenchymal Transition Confers Sensitivity to Cytotoxic Agent Ophiobolin A via Alterations in Mitochondrial Function and Metabolic Pathways Haleigh Parker1, Kayla Haberman1, Alexander Kornienko2, Antonio Evidente3, Daniel Romo4, Benny Abraham Kaipparettu5,6, Joseph Taube1,6 1 Department of Biology, Baylor University, Waco, TX, USA 2 Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, USA 3 Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte Sant’Angelo, Naples, Italy 4 Department of Chemistry and Biochemistry, Baylor University, Waco, TX, USA 5 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA 6 Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, TX, USA Background Metastatic progression in patients with triple negative breast cancer (TNBC) occurs in approximately half of all patients, reducing median overall survival. Metastasis may be facilitated through the epithelial to mesenchymal transition (EMT), which generates cancer cells with enhanced metastatic capacity and resistance to chemotherapeutics, features which are partially mediated by alterations in metabolic pathways and mitochondrial function. Here, we show a drug-like small molecule possesses EMT-specific cytotoxic activity via EMT-imparted variations in metabolic and mitochondrial functions. The fungus-derived sesterterpenoid, Ophiobolin A (OpA), possesses nanomolar cytotoxic activity and a high therapeutic index, though its target and mechanism of action remain unknown. Objectives The objectives of this study are to characterize alterations in metabolic pathways and mitochondrial function in the context of EMT, determine OpA induced alterations in specific metabolic pathways involved in metastasis and identify metabolic targets for the treatment of chemotherapeutic-resistant, metastatic triple negative breast cancer. Methods This study identifies distinct, novel metabolic alterations associated with EMT status and specific changes in mitochondrial and metabolic function associated with OpA treatment via analysis of intermediate metabolites, rates of oxidative phosphorylation and glycolysis, metabolic pathway capacity and dependency, protein expression, iron localization, reactive oxygen species accumulation and transmission electron microscopy. Results Our analysis indicates that OpA acts in a mitochondria-specific manner to cause a loss of membrane potential in EMT-positive, but not EMT-negative, cells with specific effects on complex III of the electron transport chain and oxidative phosphorylation as a whole. Furthermore, distinct shifts in glycolysis not only support previous data, but also provides insight as to mitochondrial functionality. Cells were also found to have distinct metabolic pathway capacities/dependencies and ROS and iron accumulation, depending on EMT status and OpA treatment. Finally, specific morphological alterations were uncovered via TEM image analysis. Therefore, we conclude that EMT imparts alterations in mitochondrial function and metabolic pathways, conferring sensitivity to the cytotoxic effects of OpA. Citation Format: Haleigh Parker, Kayla Haberman, Joseph Taube, Alexander Kornienko, Antonio Evidente, Daniel Romo, Benny Kaipparettu. Epithelial to Mesenchymal Transition Confers Sensitivity to Cytotoxic Agent Ophiobolin A via Alterations in Mitochondrial Function and Metabolic Pathways [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-06-08.

Abstract PO3-19-07: AC699-001, a first in human Phase 1 trial utilizing a novel estrogen receptor chimeric degrader in patients with advanced or metastatic breast cancer

Abstract Background Estrogen receptors (ER) are hormone-regulated transcription factors that play a critical role in breast cancer initiation and proliferation. Modulation of estrogen activity with therapeutics such as tamoxifen and aromatase inhibitors have been the mainstay therapeutic strategy for ER-positive breast cancer. Several ER-directed therapies have been developed to antagonize the oncogenic ER function, including Selective ER Degraders (SERDs) such as fulvestrant which is approved to treat patients with advanced or metastatic breast cancer. However, it requires intramuscular injection and has poor solubility, thereby limiting its administered dose and therefore its efficacy. In addition to SERDs, a newly emerging technology, E3 ligase-engaged chimeric degraders, has been used to induce potent and deeper ER degradation. Empowered by Accutar's proprietary Protein-Protein Interaction Targeting Chimeras (PPI-TAC) platform, AC699 was meticulously designed as a chimeric degrader to target and degrade the protein of interest, ERα. By effectively linking an ER ligand to an E3-ligase recruiting ligand, AC699 brings ERα in proximity to an E3 ligase, thereby inducing subsequent ubiquitination and degradation of ERα. Notably, chimeric ER degraders possess the unique advantage of degrading the ER protein without the inherent risk of activating an ER signal. Moreover, these molecules are not degraded alongside the target protein allowing for their efficient recycling within the cell. This direct mechanism enables chimeric ER degraders to achieve potent ER degradation with increased specificity, thereby potentially providing a higher therapeutic index compared to SERDs. This abstract describes a first-in-human Phase 1 trial of AC699, a novel ER degrader. Study Description The AC699-001 Phase 1 dose escalation study will enroll up to 60 patients with locally advanced or metastatic ER-positive, human epidermal growth factor receptor 2-negative, breast cancer. Patients must have progressed on standard treatment including at least two prior endocrine regimens or at least one prior line of therapy if combined with a CDK4/6 inhibitor. Prior chemotherapy is not required but must not exceed three prior cytotoxic regimens. Patients must have at least one measurable lesion or at least one predominantly lytic bone lesion. AC699 is given orally, once daily, with doses ranging from 100 mg to 600 mg in a standard 3+3 dose escalation design. The primary objective is to evaluate the safety and tolerability of AC699 using CTCAE 5.0. Secondary objectives include assessing preliminary anti-tumor activity according to RECIST 1.1 and characterizing the pharmacokinetic profile of single and multiple doses of AC699. Enrollment began in December 2022 with five sites in the United States planned. NCT05654532. Citation Format: Manish R Patel, Rachel Layman, Joy Nolte Fong, Hui Zhang, Su Kim, Erika Hamilton. AC699-001, a first in human Phase 1 trial utilizing a novel estrogen receptor chimeric degrader in patients with advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-19-07.