Plasma Protein Binding Research Articles

A Quantitative Structure-Activity Relationship for Human Plasma Protein Binding: Prediction, Validation and Applicability Domain.

The purpose of this study was to develop a robust and externally predictive in silico QSAR-neural network model for predicting plasma protein binding of drugs. This model aims to enhance drug discovery processes by reducing the need for chemical synthesis and extensive laboratory testing. A dataset of 277 drugs was used to develop the QSAR-neural network model. The model was constructed using a Filter method to select 55 molecular descriptors. The validation set's external accuracy was assessed through the predictive squared correlation coefficient Q2 and the root mean squared error (RMSE). The developed QSAR-neural network model demonstrated robustness and good applicability domain. The external accuracy of the validation set was high, with a predictive squared correlation coefficient Q2 of 0.966 and a root mean squared error (RMSE) of 0.063. Comparatively, this model outperformed previously published models in the literature. The study successfully developed an advanced QSAR-neural network model capable of predicting plasma protein binding in human plasma for a diverse set of 277 drugs. This model's accuracy and robustness make it a valuable tool in drug discovery, potentially reducing the need for resource-intensive chemical synthesis and laboratory testing.

LC-MS/MS method for the quantitation of a dual PI3K/BRD4 inhibitor SF2523 in mouse plasma: Application to plasma protein binding and metabolism studies.

A sensitive and selective liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantitation of dual PI3K/BRD4 inhibitor SF2523 in mouse plasma. The analysis was performed on a UPLC system connected to a Shimadzu 8060 mass spectrometer by electrospray ionization in positive multiple reaction monitoring mode. Chromatographic separation was carried out on an ACE Excel C18 column with a gradient elution containing 0.1% formic acid and methanol as the mobile phase. The linearity was conducted in the concentration range 0.1-500 ng/ml for SF2523 in 100 μl of plasma. The inter- and intra-batch precision (RSD) were both lower than 13.5%, with the accuracy (percentage bias) ranging from -10.03 to 11.56%. The validated method was successfully applied to plasma protein binding and in vitro metabolism studies. SF2523 was highly bound to mouse plasma proteins (>95% bound). Utilizing mouse S9 fractions, a total of seven phase I and II metabolites were identified with hydroxylation found to be the major metabolic pathway. Metabolite identification included analysis of retention behaviors, molecular weight changes and MS/MS fragment patterns of SF2523 and the metabolites. This newly developed and validated method allows the rapid and easy determination of the SF2523 concentration with high sensitivity in a low sample volume and can be applied to future pre-clinical studies.

Pharmacokinetics of N,N-dimethyltryptamine in Humans.

N,N-dimethyltryptamine (DMT) is a psychedelic compound under development for the treatment of major depressive disorder (MDD). This study evaluated the preclinical and clinical pharmacokinetics and metabolism of DMT in healthy subjects. The physiochemical properties of DMT were determined using a series of in vitro experiments and its metabolic profile was assessed using monoamine oxidase (MAO) and cytochrome P450 (CYP) inhibitors in hepatocyte and mitochondrial fractions. Clinical pharmacokinetics results are from the phase I component of a phase I/IIa randomised, double-blind, placebo-controlled, parallel-group, dose-escalation trial (NCT04673383). Healthy adults received single escalating doses of DMT fumarate (SPL026) via a two-phase intravenous (IV) infusion. Dosing regimens were calculated based on pharmacokinetic modelling and predictions with progression to each subsequent dose level contingent upon safety and tolerability. In vitro clearance of DMT was reduced through the inhibition of MAO-A, CYP2D6 and to a lesser extent CYP2C19. Determination of lipophilicity and plasma protein binding was low, indicating that a high proportion of DMT is available for distribution and metabolism, consistent with the very rapid clinical pharmacokinetics. Twenty-four healthy subjects received escalating doses of DMT administered as a 10-min infusion over the dose range of 9-21.5 mg (DMT freebase). DMT was rapidly cleared for all doses: mean elimination half-life was 9-12 min. All doses were safe and well tolerated and there was no relationship between peak DMT plasma concentrations and body mass index (BMI) or weight. This is the first study to determine, in detail, the full pharmacokinetics profile of DMT following a slow IV infusion in humans, confirming rapid attainment of peak plasma concentrations followed by rapid clearance. These findings provide evidence which supports the development of novel DMT infusion regimens for the treatment of MDD. Registered on ClinicalTrials.gov (NCT04673383).

Ceftobiprole medocaril for the treatment of pneumonia

ABSTRACT Introduction Ceftobiprole, a fifth-generation cephalosporin, exhibits a broad-spectrum activity against common pathogens causing pneumonia, including multidrug-resistant organisms (MDROs), such as penicillin-resistant S. pneumoniae (PRSP) and methicillin-resistant Staphylococcus aureus (MRSA) and non-extended-spectrum β -lactamase (non-ESBL) producing Enterobacterales strains. Therefore, ceftobiprole should be considered as a potential alternative for the empirical treatment of pneumonia in patients with high risk for MDROs. Area covered In this review, we discussed the role of ceftobiprole in the treatment of patients with pneumonia. Expert opinion Ceftobiprole has several advantages in the treatment of pneumonia. First, ceftobiprole exerts its bactericidal activity by inhibiting transpeptidases, especially showing strong affinities to penicillin-binding protein (PBP) 2a, PBP2× and PBP3. Second, its plasma protein binding is minimal, allowing it to penetrate lung tissue and achieve high concentrations in epithelial lung fluid. Third, ceftobiprole exhibits potent in vitro activity against a wide range of susceptible pathogens, including S. aureus, S. pneumoniae, Viridans streptococci, H. influenzae, M. catarrhalis, Enterobacterales, and particularly, MRSA and P. aeruginosa. Finally, several randomized controlled trials have demonstrated the clinical efficacy and safety of ceftobiprole in the treatment of pediatric and adult patients with community-acquired pneumonia and hospital-acquired pneumonia (excluding ventilator-associated pneumonia).

Plasma protein binding and tissue retention kinetics influence the rate and extent of nicotine delivery to the brain

Nicotine from inhaled combustible cigarette smoke is delivered rapidly to the brain, and sufficient unbound nicotine concentrations exert pharmacological effects. In addition to nicotine, combustible cigarette smoke also contains a significant number of toxicants that trigger perturbations, leading to an altered steady state due to differential expression of proteins. In this study, a physiologically based pharmacokinetic (PBPK) model for inhaled nicotine was used to simulate the influence of lysosomal change-driven tissue retention and plasma protein binding levels on nicotine pharmacokinetics (PK). A 3 × increase in tissue lysosomal volumes lowered the nicotine brain maximum concentration (Cmax) by 20.8%. Similarly, a 50% increase in plasma protein binding also lowered the unbound plasma arterial nicotine Cmax by 39.4%. Such fundamental changes in nicotine disposition due to physiological changes in combustible cigarette smokers will lead to altered nicotine consumption and exposure-responses of other weakly basic drugs. Literature reports indicate that nicotine consumed from non-combustible products do not alter drug exposures, indicating fewer or less severe toxicant-driven perturbations with the use of these products. Although several other parameters influence nicotine PK, this PBPK modeling study shows that increased tissue retention and plasma protein binding reduce nicotine delivery to the brain and could lead to differential consumption of combustible cigarettes. These differences in physiological states among combustible cigarette smokers need to be evaluated and should be considered during therapeutic interventions.

Abstract LB242: Characterizing the fate<tissue distribution and excretion route> of cancer vaccine lipoplex-RNA following intravenous injection of 14C-DOTMA-lipoplex-mRNA in mice

Abstract Messenger RNA (mRNA) has emerged as a new class of therapeutic agent delivered by a carrier lipoplex (LPX) to elicit an immune-response for treating various diseases, including cancers. However, the PK and tissue distribution of the components is not well characterized given its therapeutic novelty and structural complexity. As such, this study aimed to characterize the distribution and metabolic fate of LPX-mRNA using a radiolabeled DOTMA, a component of the LPX-mRNA therapeutic, to aid the development of this anti-cancer agent. To track the fate of LPX-mRNA, DOTMA was first radiolabeled with [14C] through chemical synthesis (14C-DOTMA, and then mixed with DOPE and mRNA at a specific ratio to form 14C-DOTMA-LPX-mRNA (14C-LPX-mRNA)). The plasma protein binding and blood cell partitioning for both 14C-LPX-mRNA and 14C-DOTMA alone were assessed in vitro. Moreover, the in vivo biodistribution and elimination of both 14C-molecules were characterized following a single intravenous (IV) injection in mice up to 12 weeks.The in-vitro assays showed the 14C-DOTMA and the 14C-LPX-mRNA were highly associated with plasma proteins and blood cell as the complexes were spun down at a much higher level as compared to in PBS solution (~5% and ~60% plasma proteins bound and ~60% and ~80% blood cell partitioned in 14C-DOTMA and the 14C-LPX-mRNA, respectively). Following in-vivo dosing in mice, plasma radioactivity of both test molecules showed a biphasic elimination profile with a rapid phase of decrease during the first 3 days followed by a prolonged exposure phase. The radioactivity in the whole blood and plasma displayed similar profiles but had minimal partitioning to blood cells, differing from the in-vitro data. We hypothesized that, both drug substances began to associate with plasma proteins/blood cells, then quickly distributed to the tissues and eliminated from the systemic circulation. Among all tissues analyzed, the liver and spleen showed the highest radioactivity levels where the 14C-LPX-mRNA peaked within the day while 14C-DOTMA peaked at 3-weeks-after-dose, followed by a long persistency. Lower levels of distribution and persistence of radioactivity were also observed in other tissues. The route of elimination is mainly through the biliary-fecal route with minimal contribution from the renal route for 14C-LPX-mRNA. 14C-LPX-mRNA achieved mass balance at 8-weeks after dose where ~70% was eliminated through feces, 3% through urine and ~20% remaining in tissues. 14C-DOTMA animals have an under-recovery of about 40-50% in radioactivity due to animals’ low intake of food and water which caused a severe reduction in animals’ weight. In summary, this study fully characterized the fate of the 14C-DOTMA and the 14C-LPX-mRNA in vitro and in vivo in mice. Our data demonstrated that the LPX-mRNA (by tracking DOTMA) mainly distributed to the spleen and liver with a long persistency, consistent with previous study showing the spleen as the major tissue for mRNA distribution. However, the LPX’s elimination profile (duration/persistency) is likely very different from that of mRNA. The ongoing work is to track the fate of mRNA component in LPX-mRNA, which could provide more insight on the correlation of DOTMA and mRNA, and help the development of this novel therapeutic modality. Citation Format: Victor Yip, Gillie Roth, Elizabeth Torres, Sara Wichner, Craig Blanchette, Amrita Kamath, Ben-Quan Shen. Characterizing the fate<tissue distribution and excretion route> of cancer vaccine lipoplex-RNA following intravenous injection of 14C-DOTMA-lipoplex-mRNA in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB242.

Novel 1,4 benzothiazine 3-one derivatives as anticonvulsant agents: Design, synthesis, biological evaluation and computational studies

In this study, two series of novel 1,4-benzothiazine-3-one derivatives with alkyl substitution (series 1: 4a-4f) and aryl substitution (series 2: 4g-4l) were designed and synthesized based on the chemical scaffolds of perampanel, hydantoins, progabide and etifoxine as anti-convulsant agents. The chemical structures of the synthesized compounds were confirmed by FT-IR, 1H NMR and 13C NMR spectroscopy. Anti-convulsant effect of the compounds was examined through intraperitoneal pentylenetetrazol (i.p. PTZ) induced epilepsy mouse models. Compound 4h (4-(4-bromo-benzyl)− 4 H-benzo[b] [1,4] thiazin-3(4 H)-one) demonstrated a promising activity toward chemically-induced seizure experiment. Molecular dynamics simulation on GABA-Aergic receptors as a plausible mechanism were also done to achieve the binding and orientation of compounds in the active site of the target to evaluate the results of docking and experimental studies. The computational results were confirmed the biological activity. DFT study of 4c and 4h was performed on B3LYP/6–311 G** level of theory. Reactivity descriptors such as HOMO, LUMO, electron affinity, ionization potential, chemical potential, hardness and softness were studied in detail and show that 4h has higher activity than 4c. Also, the frequency calculations were performed on the same level of theory and the results are in line with experimental data. Moreover, in silico ADMET properties were done to establish a relationship between the physiochemical data of the designed compounds and their in-vivo activity. Appropriate plasma protein binding and high blood-brain barrier penetration are the main features of desired in-vivo performance.

Abstract LB320: Discovery and characterization of QTX3034, a potent, selective, and orally bioavailable allosteric KRAS inhibitor

Abstract The RAS family of proto-oncogenes are the most frequently mutated genes in cancer, in which mutations in KRAS account for approximately 25% of all human cancers. RAS oncogenes impair the ability of RAS to convert from its active GTP-bound form into its inactive GDP-bound state leading to the sustained activation of the MAPK signaling pathway and ultimately driving tumorigenesis. Until recently, KRAS was regarded as undruggable, but newly approved covalent inhibitors of KRASG12C have demonstrated clinical benefit in patients harboring this mutation. However, patients with KRASG12C mutation only represent approximately 10% of the KRAS-mutated or amplified cancer population, and multiple RAS-mediated resistance mechanisms have emerged with these covalent compounds. Here we show that QTX3034 is a potent, highly selective, and orally bioavailable mutant KRAS inhibitor. Using the most common KRAS mutant, KRASG12D, QTX3034 demonstrated picomolar binding affinity (0.6 nM) to the inactive form of KRASG12D and inhibited SOS1/2 mediated nucleotide exchange with picomolar potency (0.2 nM). In a NanoBiT cellular target engagement assay, QTX3034 treatment disrupted KRASG12D:RAF1 protein-protein interaction in a concentration-dependent manner with an EC50 of 17 nM in HEK293T cells. Western blot analyses and CTG proliferation assays illustrated that QTX3034 treatment inhibited downstream ERK phosphorylation and cell proliferation in KRASG12D -driven cancer cell lines. Similar inhibitory effects were observed across KRASG12D and KRASG12V mutant cancer cell lines, albeit less potent against the latter. Notably, QTX3034 produced no effect against NRAS or BRAF mutant cells. In vivo, QTX3034 achieved sustained systemic exposure levels required for efficacy following single oral administration in mice, indicating potential durable inhibition of KRAS signaling in vivo. In a KRASG12D -driven xenograft model, oral administration of QTX3034 twice daily (BID) demonstrated dose-dependent anti-tumor efficacy and achieved tumor regression in 100% of tumors. In a KRASG12V -driven xenograft model, oral administration of QTX3034 showed significant tumor growth inhibition, consistent with its activity against KRASG12V in vitro. QTX3034 was well-tolerated in rodent, repeat dose toxicology studies and exhibited significant exposure in the brain. QTX3034 has good solubility, permeability, and moderate protein binding in human plasma. The systemic clearance in rats and dogs was moderate to high, respectively, with good oral bioavailability. QTX3034 exhibited weak CYP inhibition (direct and time-dependent) with a favorable in vitro off-target selectivity/safety profile. Taken together, this preclinical characterization supports the advancement of QTX3034 into IND-enabling studies for KRAS mutant cancers. Citation Format: Yang W. Zhang, Dave Rominger, Elizabeth Donohue Vo, Jillian M. Silva, Yang J. Zhang, Greg Lee, John Micozzi, Ben Reid, Brooke McDonough, Audrey Hospital, Juan I. Luengo, Cameron Pitt, Hong Lin. Discovery and characterization of QTX3034, a potent, selective, and orally bioavailable allosteric KRAS inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB320.

Brigatinib pharmacokinetics in patients with chronic hepatic impairment

SummaryBrigatinib is an anaplastic lymphoma kinase (ALK) inhibitor approved for the treatment of ALK-positive non-small cell lung cancer. This open-label, parallel-group study investigated the effect of chronic hepatic impairment on the pharmacokinetics (PK) of brigatinib to inform dosing recommendations for these patients. Participants with hepatic impairment classified according to Child-Pugh categories of mild (A), moderate (B), or severe (C) and matched-healthy participants with normal hepatic function received a single oral dose of 90-mg brigatinib. Plasma samples were collected for the determination of brigatinib plasma protein binding and estimation of plasma PK parameters. Twenty-seven participants were enrolled (Child-Pugh A–C, n = 6 each; matched-healthy participants, n = 9). The mean fraction of free plasma brigatinib was comparable for the Child-Pugh A (11.1%), Child-Pugh B (10.8%), and healthy participant groups (8.5%); free brigatinib was higher in the Child-Pugh C group (23.1%). There were no clinically meaningful effects of mild or moderate hepatic impairment on unbound systemic exposures (area under the plasma concentration-time curve [AUC]) of brigatinib (geometric least-squares mean ratios [90% CI] of 89.32% [69.79%–114.31%] and 99.55% [77.78%–127.41%], respectively). In the severe hepatic impairment group, brigatinib unbound AUC was approximately 37% higher (geometric least-squares mean ratio [90% CI] of 137.41% [107.37%–175.86%]) compared with healthy participants with normal hepatic function. Brigatinib was well tolerated in healthy participants and in participants with hepatic impairment. No dose adjustment is required for patients with mild or moderate hepatic impairment. The brigatinib dose should be reduced by approximately 40% for patients with severe hepatic impairment.

ADME, Pharmacokinetic Scaling, Pharmacodynamic and Prediction of Human Dose and Regimen of Novel Antiviral Drugs.

The search for new drugs is an extremely time-consuming and expensive endeavour. Much of that time and money go into generating predictive human pharmacokinetic profiles from preclinical efficacy and safety animal data. These pharmacokinetic profiles are used to prioritize or minimize the attrition at later stages of the drug discovery process. In the area of antiviral drug research, these pharmacokinetic profiles are equally important for the optimization, estimation of half-life, determination of effective dose, and dosing regimen, in humans. In this article we have highlighted three important aspects of these profiles. First, the impact of plasma protein binding on two primary pharmacokinetic parameters-volume of distribution and clearance. Second, interdependence of primary parameters on unbound fraction of the drug. Third, the ability to extrapolate human pharmacokinetic parameters and concentration time profiles from animal profiles.

Abstract 503: ISM3412, a novel and selective MAT2A inhibitor for the treatment of cancer

Abstract The enzyme methionine adenosyltransferase 2α (MAT2A) has an important role in metabolism and epigenetics as the major producer of the universal methyl donor S-adenosyl methionine (SAM). Despite broad cellular functions, MAT2A was recently implicated as a synthetic lethal target in cancers that have a deletion of the methylthioadenosine phosphorylase (MTAP) gene, which is found in approximately 15% of all cancers. Here, we report ISM3412 is a novel potent MAT2A inhibitor with high selectivity. In enzymatic assays, ISM3412 demonstrated a strong inhibition of MAT2A with an IC50 of 19.4 nM. In both HCT116 MTAP-/- cells and HCT116 parental cells, the compound inhibited SAM production, with IC50 values of 5.97 nM and 3.66 nM, respectively. Additionally, it inhibited SDMA production in HCT116 MTAP-/- cells (IC50 of 6.37 nM), but not in HCT116 parental cells (IC50 > 2000 nM). Consistent with the large SDMA inhibitory potency difference between the HCT116 isogenic cell pair, ISM3412 also exhibited very good selectivity in cellular proliferation assays. While it inhibited cellular growth in HCT116 MTAP-/-cells with an IC50 of 199nM, its inhibitory potency on HCT116 parental cells was very weak (IC50 of >21117nM), revealing more than a 100-fold selectivity in inhibiting growth in this isogenic pair cell line. Furthermore, while ISM3412 strongly inhibited proliferation in multiple cancer cell lines with natural MTAP deficiency (including pancreatic cancer, bladder cancer, and NSCLC), the same was not observed in multiple MTAP-intact cell lines (IC50 > 30 uM). Consistent with the in vitro data, ISM3412 demonstrated robust mono-therapeutic efficacy in an MTAP-/- HCT116 CDX model with tumor growth inhibition of 66% at 3 mg/kg QD. Similarly, ISM3412 also demonstrated robust single-agent efficacy in CDX models of pancreatic cancer, bladder cancer and NSCLC, as well as in a PDX model of esophageal cancer. Notably, ISM3412 showed improved efficacy when combined with docetaxel, compared to the individual monotherapy. ISM3412, at 10 uM, showed no obvious agonistic or antagonistic effect on 44 selected targets in a mini safety panel, demonstrating its selectivity as a MAT2A inhibitor. In addition to its strong biological potency and selectivity, ISM3412 exhibited favorable drug-likeness properties, including low molecular weight, good solubility and permeability, and low plasma protein binding. In vivo PK data revealed low clearance and high oral-bioavailability. Further, it was well tolerated with no significant hepatobiliary toxicity. In conclusion, ISM3412 is a novel and highly selective MAT2A inhibitor for MTAP-deficient cancers, and merits clinical evaluation. Citation Format: Qingyuan Meng, Xiao Ding, Xiaosong Liu, Hailong Wang, Ling Wang, Junwen Qiao, Hua Cao, Yushu Yin, Congcong Zhu, Xing Liang, Xin Cai, Yuanyuan Xu, Chenxi Xu, Shan Chen, Sujata Rao, Feng Ren, Alex Zhavoronkov. ISM3412, a novel and selective MAT2A inhibitor for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 503.

Abstract 2790: Preclinical studies of ZG19018, a novel irreversible covalent inhibitor of KRAS G12C, for the treatment of advanced non-small cell lung cancer and other solid tumors

Abstract Growing evidences of covalent irreversible inhibitors in clinical treatments of solid tumors with KRAS G12C mutation have recently emerged after FDA-approved AMG510 (Sotorasib) for NSCLC chemotherapies. ZG19018 is an irreversible KRAS G12C inhibitor with novel structure that shows promising preclinical results for in vitro molecular and biological studies and in vivo G12C-mutated cancer models and safety studies in animals. For instance, ZG19018 rapidly and selectively forms covalent bonds with G12C-GDP, which accounts for lock-in KRAS protein as the inactive GDP-bound state but inhibits the activation of numerous downstream signaling pathways like RAF/MEK on ERK phosphorylation. ZG19018 showed highly inhibition of a 3D growth panel for human cancer cell lines harboring the KRAS G12C mutation, e.g. H358 (NSCLCs), MIA PaCa-2 (pancreatic) and SW837 (colorectal), etc. For pharmacodynamics, a battery of in vitro and in vivo ADME/DMPK studies indicated a high plasma protein binding (>99.6%) of ZG19018 with over 40% bioavailability in rat and dog via oral administration for the adequate drug levels in various tissues including lung, crossing BBB to reach brain, and accumulation in tumors. For in vivo anti-tumor efficacy, ZG19018 exhibited significant dose-dependent inhibition of tumor growth of G12C-driven subcutaneous models in nude mouse like H358 NSCLC cells but induced further tumor regression in pancreatic cancer MIA PaCa-2 xenograft. ZG19018 also showed an enhanced anti-tumor activities as combined with chemo-reagent Donafinib, a broad tyrosine kinase inhibitor blocking RAF/MEK/ERK signaling pathways of tumor cells, in the same H358 xenograft model. The general toxicology studies in rat under 28 days repeated oral administration (q.d.) showed NOAEL and STD10 values at 75 and 150 mg/kg/day, respectively. The safety pharmacological studies showed no notable effects of ZG19018 on the cardiovascular, respiratory and CNS systems. The genotoxic potential studies indicated ZG19018 without mutagenesis. Collectively, ZG19018 is now in phase I/II clinical trials for the treatments of solid tumors with KRAS G12C mutation in China. Citation Format: Bing Zhu, Dawei Cui, Ruifeng Liu, Weidong Feng, Zelin Sheng, Binhua Lv. Preclinical studies of ZG19018, a novel irreversible covalent inhibitor of KRAS G12C, for the treatment of advanced non-small cell lung cancer and other solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2790.

Physicochemical properties, drug likeness, ADMET, DFT studies, and in vitro antioxidant activity of oxindole derivatives

Poor pharmacokinetic and safety profiles create significant hurdles in the drug development process. This work focuses on a detailed understanding of drug discovery interplay among physicochemical, pharmacokinetic, toxicity endpoints, and antioxidant properties of oxindole derivatives. DFT compıutations were also performed at B3LYP/6-311G** level to evaluate the physicochemical properties, global reactivity features, and intramolecular interactions. The BOILED-Egg pharmacokinetic model envisaged gastrointestinal absorption, blood-brain barrier penetration, and no interaction with p-glycoprotein for compounds C1 and C2. The physicochemical evaluation revealed that C1 possesses superior drug-like properties fit for oral absorption. Both derivatives were predicted to have high plasma protein binding, efficient distribution, and inhibiting CYP 450 major isoforms but serve as substrates only for a few of them. Both molecules have mild to moderate clearance rates. Out of ten toxicity parameters, only hepatotoxicity was predicted. DFT results implied that the meta position of the -OH group made the possibility of charge transfer greater than -para positioned -OH, due to the ΔNmax (eV) values of molecules C1 and C2 being calculated at 2.596 and 2.477, respectively. Both C1 and C2 exhibited a concentration dependant DPPH and ABTS radical scavenging activity. The chemical structure-physicochemical-pharmacokinetic relationship identified the meta position as the favorite for the electron-withdrawing hydroxyl group. This provides useful insight to medicinal chemists to design 6-chlorooxindole derivatives with an acceptable drug-like and pharmacokinetic property.

Quantitative determination of lurbinectedin, its unbound fraction and its metabolites in human plasma utilizing ultra-performance LC-MS/MS.

Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) methods to quantify total lurbinectedin, its plasma protein binding to derive the unbound fraction and its main metabolites 1',3'-dihydroxy-lurbinectedin (M4) and N-desmethyl-lurbinectedin (M6) in human plasma, were developed and validated. For lurbinectedin, sample extraction was performed using supported liquid extraction. For metabolites, liquid-liquid extraction with stable isotope-labeled analogue internal standards was used. Plasma protein binding was evaluated using rapid equilibrium dialysis. In vitro investigations at different plasma protein concentrations were carried out to estimate dissociation rate constants to albumin and alpha-1-acid glycoprotein (AAG). Calibration curves displayed good linearity over 0.1 to 50 ng/mL for lurbinectedin and 0.5 to 20 ng/mL for the metabolites. Methods were validated in accordance with established guidance. The inter-day precision and accuracy ranged from 5.1% to 10.7%, and from -5% to 6% (lurbinectedin in plasma); from 3.1% to 6.6%, and from 4% to 6% (lurbinectedin in plasma:PBS); from 4.5% to 12.9%, and from 4% to 9% (M4); and from 7.5% to 10.5%, and from 6% to 12% (M6). All methods displayed good linearity (r2 >0.99). Recovery was evaluated for lurbinectedin in plasma:PBS (66.4% to 86.6%), M4 (7.82% to 13.4%) and M6 (22.2% to 34.3%). The method for lurbinectedin in plasma has been applied in most clinical studies, while the plasma:PBS and metabolites methods were used to evaluate the impact of special conditions on lurbinectedin PK. Lurbinectedin plasma protein binding was 99.6% and highly affected by AAG concentration. These UPLC-MS/MS methods enable the rapid and sensitive quantification of lurbinectedin and its main metabolites in clinical samples.

Importance of relative binding of bisphenol A and bisphenol S to plasma proteins for predicting their in vivo potencies

Many studies suggest that the potential impact of bisphenol S (BPS) as an endocrine disruptor is comparable to that of bisphenol A (BPA). However, in vitro-to-in vivo and from animal to human extrapolations require knowledge of the plasma free fraction of the active endocrine compounds. The present study aimed to characterise BPA and BPS binding to plasma proteins both in humans and different animal species. The plasma protein binding of BPA and BPS was assessed by equilibrium dialysis in plasma from adult female mice, rats, monkeys, early and late pregnant women as well as paired cord blood, early and late pregnant sheep and foetal sheep.The fraction of free BPA was independent of plasma concentrations and ranged between 4% and 7% in adults. This fraction was 2 to 3.5 times lower than that of BPS in all species except sheep, ranging from 3% to 20%. Plasma binding of BPA and BPS was not affected by the stage of pregnancy, BPA and BPS free fractions representing about 4% and 9% during early and late human pregnancy, respectively. These fractions were lower than the free fractions of BPA (7%) and BPS (12%) in cord blood.Our results suggest that similarly to BPA, BPS is extensively bound to proteins, mainly albumin. The higher fraction of free BPS compared to BPA may have implications for human exposure assessment since BPS free plasma concentrations are expected to be 2 to 3.5 times higher than that of BPA for similar plasma concentration.

Transcranial focused ultrasound-mediated unbinding of phenytoin from plasma proteins for suppression of chronic temporal lobe epilepsy in a rodent model

The efficacy of many anti-epileptic drugs, including phenytoin (PHT), is reduced by plasma protein binding (PPB) that sequesters therapeutically active drug molecules within the bloodstream. An increase in systemic dose elevates the risk of drug side effects, which demands an alternative technique to increase the unbound concentration of PHT in a region-specific manner. We present a low-intensity focused ultrasound (FUS) technique that locally enhances the efficacy of PHT by transiently disrupting its binding to albumin. We first identified the acoustic parameters that yielded the highest PHT unbinding from albumin among evaluated parameter sets using equilibrium dialysis. Then, rats with chronic mesial temporal lobe epilepsy (mTLE) received four sessions of PHT injection, each followed by 30 min of FUS delivered to the ictal region, across 2 weeks. Two additional groups of mTLE rats underwent the same procedure, but without receiving PHT or FUS. Assessment of electrographic seizure activities revealed that FUS accompanying administration of PHT effectively reduced the number and mean duration of ictal events compared to other conditions, without damaging brain tissue or the blood–brain barrier. Our results demonstrated that the FUS technique enhanced the anti-epileptic efficacy of PHT in a chronic mTLE rodent model by region-specific PPB disruption.

New Dual Inhibitors of Bacterial Topoisomerases with Broad-Spectrum Antibacterial Activity and In Vivo Efficacy against Vancomycin-Intermediate Staphylococcus aureus.

A new series of dual low nanomolar benzothiazole inhibitors of bacterial DNA gyrase and topoisomerase IV were developed. The resulting compounds show excellent broad-spectrum antibacterial activities against Gram-positive Enterococcus faecalis, Enterococcus faecium and multidrug resistant (MDR) Staphylococcus aureus strains [best compound minimal inhibitory concentrations (MICs): range, <0.03125-0.25 μg/mL] and against the Gram-negatives Acinetobacter baumannii and Klebsiella pneumoniae (best compound MICs: range, 1-4 μg/mL). Lead compound 7a was identified with favorable solubility and plasma protein binding, good metabolic stability, selectivity for bacterial topoisomerases, and no toxicity issues. The crystal structure of 7a in complex with Pseudomonas aeruginosa GyrB24 revealed its binding mode at the ATP-binding site. Expanded profiling of 7a and 7h showed potent antibacterial activity against over 100 MDR and non-MDR strains of A. baumannii and several other Gram-positive and Gram-negative strains. Ultimately, in vivo efficacy of 7a in a mouse model of vancomycin-intermediate S. aureus thigh infection was also demonstrated.

Target attainment and population pharmacokinetics of flucloxacillin in critically ill patients: a multicenter study

PurposeInsufficient antimicrobial exposure has been associated with worse clinical outcomes. Reportedly, flucloxacillin target attainment in critically ill patients was heterogeneous considering the study population selection and reported target attainment percentages. Therefore, we assessed flucloxacillin population pharmacokinetics (PK) and target attainment in critically ill patients.MethodsThis prospective, multicenter, observational study was conducted from May 2017 to October 2019 and included adult, critically ill patients administered flucloxacillin intravenously. Patients with renal replacement therapy or liver cirrhosis were excluded. We developed and qualified an integrated PK model for total and unbound serum flucloxacillin concentrations. Monte Carlo dosing simulations were performed to assess target attainment. The unbound target serum concentration was four times the minimum inhibitory concentration (MIC) for ≥ 50% of the dosing interval (ƒT>4xMIC ≥ 50%).ResultsWe analyzed 163 blood samples from 31 patients. A one-compartment model with linear plasma protein binding was selected as most appropriate. Dosing simulations revealed 26% ƒT>2 mg/L ≥ 50% following continuous infusion of 12 g flucloxacillin and 51% ƒT>2 mg/L ≥ 50% for 24 g.ConclusionBased on our dosing simulations, standard flucloxacillin daily doses of up to 12 g may substantially enhance the risk of underdosing in critically ill patients. Prospective validation of these model predictions is needed.

A Study on Pharmacokinetic Functionalities and Safety Margins of an Optimized Simvastatin Nanoformulation.

A pharmaceutical formulation with favorable pharmacokinetic parameters is more likely to be efficacious and safe to overcome the failures of the drug resulting from lack of efficacy, poor bioavailability, and toxicity. In this view, we aimed to evaluate the pharmacokinetic functionalities and safety margin of an optimized CS-SS nanoformulation (F40) by in vitro/in vivo methods. The everted sac technique was used to evaluate the improved absorption of a simvastatin formulation. In vitro protein binding in bovine serum and mice plasma was performed. The formulation's liver and intestinal CYP3A4 activity and metabolic pathways were investigated by the qRT-PCR technique. The excretion of cholesterol and bile acids was measured to demonstrate the formulation's cholesterol depletion effect. Safety margins were determined by histopathology as well as fiber typing studies. In vitro protein binding results revealed the existence of a high percentage of free drugs (22.31 ± 3.1%, 18.20 ± 1.9%, and 16.9 ± 2.2%, respectively) compared to the standard formulation. The controlled metabolism in the liver was demonstrated from CYP3A4 activity. The formulation showed enhanced PK parameters in rabbits such as a lower Cmax, clearance, and a higher Tmax, AUC, Vd, and t1/2. qRT-PCR screening further proved the different metabolic pathways followed by simvastatin (SREBP-2) and chitosan (PPAR-γ pathway) in the formulation. The results from qRT-PCR and histopathology confirmed the toxicity level. Hence, this pharmacokinetic profile of the nanoformulation proved it has a unique synergistic hypolipidemic modality.

Amisulpride Augmentation in Schizophrenia Patients with Poor Response to Olanzapine: A 4-week, Randomized, Rater-Blind, Controlled, Pilot Study

IntroductionOlanzapine (OLA) is a common first-prescribed antipsychotic and has shown favorable efficacy in acutely exacerbated patients with schizophrenia. The mixed receptor activity of OLA and its greater affinity for serotonin 5-HT2A rather than dopamine D2 receptors are similar to those of clozapine. Pharmacokinetically, OLA is metabolized mainly by hepatic cytochrome enzyme P450 1A2 (CYP1A2). Because risks of antipsychotic polypharmacy include increased drug-drug interactions, pharmacokinetic considerations are important for selection of antipsychotics to be combined. Due to its pharmacological characteristics, amisulpride (AMI), another atypical antipsychotic with proven efficacy, is a promising adjuvant agent of special interest. AMI is unlikely to interact with other drugs due to the low plasma protein binding and metabolism and does not affect the activity of the CYP system. Furthermore, AMI is highly selective for dopamine D2/D3 receptors; has minimal or no affinity for D1, D4, or D5 receptors. Despite the potential benefits of the combination of OLA and AMI, only a few open-label studies have been conducted, and no randomized clinical trial has been performed to date to examine the efficacy and tolerability of the combination. Hence, the goals of this study were to test the hypothesis that AMI augmentation would improve psychotic symptoms and be well tolerated in schizophrenic patients who showed poor response to OLA monotherapy.ObjectivesThe purpose of this study was to compare the efficacy and tolerability of continued olanzapine (OLA) versus amisulpride (AMI) augmentation in schizophrenic patients with poor response to OLA monotherapy.MethodsThe present 4-week, randomized, rater-blinded study included 25 patients with schizophrenia who were partially or completely unresponsive to treatment with OLA monotherapy. Eligible subjects were randomly assigned at a 1:1 ratio to continuation of OLA monotherapy (OLA group) or OLA with AMI augmentation (AMI group). Efficacy was primarily evaluated using the Positive and Negative Syndrome Scale (PANSS) at baseline and at 1, 2, and 4 weeks.ResultsThe changes in PANSS total score and PANSS-positive subscale score were significantly different (p &lt; 0.05) between the OLA and AMI groups. The differences between the two groups in PANSS-negative subscale, PANSS-general subscale, Brief Psychiatric Rating Scale, and Clinical Global Impression-Severity (CGI-S) scale scores were not statistically significant.ConclusionsAMI augmentation could be an effective strategy for patients with schizophrenia who show inadequate early response to OLA monotherapy.Disclosure of InterestW.-M. Bahk Grant / Research support from: Handok Pharmaceuticals, Seoul, Korea, Y. S. Woo: None Declared, S.-Y. Park: None Declared, B.-H. Yoon: None Declared, S.-M. Wang: None Declared, M.-D. Kim: None Declared