Clinical Dose Range Research Articles

Translational modelling to predict human pharmacokinetics and pharmacodynamics of a Bruton's tyrosine kinase-targeted protein degrader BGB-16673.

Bifunctional small molecule degraders, which link the target protein with E3 ubiquitin ligase, could lead to the efficient degradation of the target protein. BGB-16673 is a Bruton's tyrosine kinase (BTK) degrader. A translational PK/PD modelling approach was used to predict the human BTK degradation of BGB-16673 from preclinical in vitro and in vivo data. A simplified mechanistic PK/PD model was used to establish the correlation between the in vitro and in vivo BTK degradation by BGB-16673 in a mouse model. Human and mouse species differences were compared using the parameters generated from in vitro human or mouse blood, and human or mouse serum spiked TMD-8 cells. Human PD was then predicted using the simplified mechanistic PK/PD model. BGB-16673 showed potent BTK degradation in mouse whole blood, human whole blood, and TMD-8 tumour cells in vitro. Furthermore, BGB-16673 showed BTK degradation in a murine TMD-8 xenograft model in vivo. The PK/PD model predicted human PD and the observed BTK degradation in clinical studies both showed robust BTK degradation in blood and tumour at clinical dose range. The presented simplified mechanistic model with reduced number of model parameters is practically easier to be applied to research projects compared with the full mechanistic model. It can be used as a tool to better understand the PK/PD behaviour for targeted protein degraders and increase the confidence when moving to the clinical stage.

Pharmacological Basis of Differences in Dose Response, Dose Equivalence, and Duration of Action of Inhaled Corticosteroids.

Asthma treatment guidelines classify inhaled corticosteroid (ICS) regimens as low, medium, or high dose. However, efficacy and safety are not independently assessed accordingly. Moreover, differences in ICS duration of action are not considered when a dose regimen is selected. We investigated the efficacy and safety implications of these limitations for available ICS molecules. Published pharmacodynamic and pharmacokinetic parameters were used, alongside physiological and pharmacological principles, to estimate the efficacy and safety of available ICS molecules. Extent and duration of glucocorticoid receptor (GR) occupancy in the lung (efficacy) and cortisol suppression (systemic exposure and safety) were estimated. Some ICS regimens (e.g., fluticasone furoate, fluticasone propionate, and ciclesonide) rank high for efficacy but low for systemic exposure, contrary to how ICS dose equivalence is currently viewed. Differences in dose-response relationships for efficacy and systemic exposure were unique for each ICS regimen and reflected in their therapeutic indices. Notably, even low doses of most ICSs can generate high GR occupancy (≥ 90%) across the entire dose interval at steady state, which may explain previously reported difficulties in obtaining dose responses within the clinical dose range and observations that most clinical benefit typically occurs at low doses. The estimated post dose duration of lung GR occupancy for ICS molecules was categorized as 4-6h (short), 14-16h (medium), 25-40h (long), or > 80h (ultra-long), suggesting potentially large differences in anti-inflammatory duration of action. In a real-world clinical setting where there may be poor adherence to prescribed therapy, our findings suggest a significant therapeutic advantage for longer-acting ICS molecules in patients with asthma.

Safety, tolerability, and pharmacokinetics of aildenafil citrate tablets, a novel oral PDE5 inhibitor, in healthy Chinese volunteers after multiple-dose administration.

Aildenafil citrate is a potent and selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase type 5, developed for the treatment of erectile dysfunction (ED). This study aimed to assess the pharmacokinetics, safety, and tolerability of aildenafil citrate tablets after multiple doses in healthy Chinese males. Twenty participants were divided into 2 groups, 10 participants each. Participants were administered multiple doses of aildenafil citrate tablets at 30and 60mg. The safety evaluation was based on clinical symptoms and adverse events. Concentrations of aildenafil and its key metabolites (M1, M5, and M12) in human serum were measured by liquid chromatography-tandem mass spectrometry. Pharmacokinetic analysis showed rapid absorption and elimination of aildenafil, with a median time to maximum serum concentration of 1hour and mean terminal half-lives of 2.75and 3.26hours in the respective dose groups. The mean maximum concentration was proportional to the aildenafil dose in the range of 30to 60mg, although the area under the curve was not proportional for serum concentration vs time 0 to the last measurable time point (24 hours). Multiple doses of aildenafil were well tolerated, with 60.0% of men experiencing treatment-emergent adverse events, notably myalgia and fatigue, particularly in the 60-mg group. Aildenafil citrate tablets demonstrated favorable tolerability with once-daily administration over the clinical dose range. The occurrence of myalgia and fatigue was more prevalent in the 60-mg group. From a pharmacokinetic perspective, optimal administration of aildenafil citrate tablets appears to be 1hour before sexual intercourse in men with ED. This study presents robust safety and pharmacokinetic data at expected therapeutic doses, unaffected by clinical factors. The efficacy of aildenafil citrate tablets warrants further validation in individuals with ED. Aildenafil citrate tablets exhibited good tolerability in healthy Chinese males following multiple doses at 30and 60mg. The 60-mg group showed an increased incidence of myalgia and fatigue, suggesting the need for heightened clinical vigilance. The mean maximum concentration, but not the area under the curve, displayed dose proportionality within the 30- to 60-mg dose range, and no significant drug accumulation was observed with repeated daily administration. CTR20192473 (http://www.chinadrugtrials.org.cn).

Assessment of Dose Proportionality of Three Dose Strengths (6 mg, 12 mg and 24 mg) over the Clinical Dose Range (6–48 mg) of the Newly Developed Once-Daily Extended Release Tablet Formulation of Deutetrabenazine (P2-11.016)

<h3>Objective:</h3> To assess dose proportionality of three dose strengths (6mg, 12mg and 24mg), and across recommended clinical dose range (6mg – 48mg), for the once-daily (QD) extended-release tablet formulation of deutetrabenazine. <h3>Background:</h3> Deutetrabenazine (Austedo, Teva), a twice-daily (BID) formulation, is an approved treatment (daily doses 6–48mg) for tardive dyskinesia and chorea associated with Huntington disease. The new QD formulation has shown to deliver similar daily exposure to the BID formulation. <h3>Design/Methods:</h3> In a randomized phase 1 study (Study TV50717-PK-10175), healthy adult males and females (n=116) received single administrations of the QD formulation in a fed state (2×6mg, 1×12mg, 1×24mg, 2×24mg). Safety was assessed, and pharmacokinetic (PK) blood samples were collected pre-dose and up to 96 hours post-dose. Geometric mean ratios (GMRs) and 90% CIs were computed for PK parameters (maximum plasma concentration [C_max], area under the plasma concentration curve from time 0 to 36 hours [AUC_0–36h] and extrapolated to infinity [AUC_0-inf]) of deutetrabenazine, and active metabolites, deuterated α-HTBZ and β-HTBZ (individually and as a sum). A power model was fitted to describe the relationship between dose and PK parameters using a mixed model with sequence, period, and dose as fixed effects; and subject as random effect. To determine dose proportionality starting at 6mg, relative bioavailability was assessed between 2×6mg and 1×12mg. <h3>Results:</h3> GMRs and 90% CIs for C_max and AUCs fell within the bioequivalence limits of 80.00%–125.00%, demonstrating similarity between 2×6mg and 1×12mg tablets. Dose proportionality was demonstrated for all PK parameters and all analytes for QD formulation dose strengths 6mg, 12mg, and 24mg; and over the clinical dose range (6–48mg), as the 90% CIs for the slopes were contained within 0.839 to 1.161 and 0.839 to 1.107, respectively. <h3>Conclusions:</h3> The QD formulation of deutetrabenazine exhibits dose proportional pharmacokinetics for dose strengths (6mg, 12mg and 24mg), and across the full clinical dose range (6mg – 48mg). <b>Disclosure:</b> Dr. Sunzel has received personal compensation for serving as an employee of Teva Pharmaceuticals. Dr. Sunzel has stock in Teva Pharmaceuticals. An immediate family member of Dr. Sunzel has stock in Incyte. Dr. Ghibellini has received personal compensation for serving as an employee of Teva Pharmaceutical. Dr. Ghibellini has stock in Teva Pharmaceuticals. Ms. Iyengar has received personal compensation for serving as an employee of Teva. Ms. Iyengar has stock in Teva. Dr. Gutierrez has stock in Teva. Mrs. Ruffo has nothing to disclose. Dr. Gordon has received personal compensation for serving as an employee of Teva. Dr. Gordon has stock in Teva. Laura Rabinovich-Guilatt has received personal compensation for serving as an employee of Teva Pharmaceuticals. Laura Rabinovich-Guilatt has stock in Teva Pharmaceuticals.

1652. Sulbactam against Acinetobacter baumannii Pneumonia: Pharmacokinetic/Pharmacodynamic Appraisal of Current Dosing Recommendations

Abstract Background Sulbactam (SUL), available in the USA as ampicillin-sulbactam, is a first line treatment for Acinetobacter baumannii infections. SUL is bactericidal against A. baumannii through affinity to penicillin-binding proteins with no synergy upon ampicillin addition. Despite its wide use, SUL dosing has not been standardized for management of A. baumannii infections. Herein, we examined SUL pharmacokinetic/pharmacodynamic (PK/PD) targets against A. baumannii in a neutropenic murine pneumonia model followed by estimation of the probability of target attainment (PTA) across a range of clinical SUL doses. Methods Eight clinical A. baumannii isolates (SUL MICs 1–16 mg/L) were tested. Mice were inoculated intranasally with 107 colony forming units (CFU)/mL bacterial suspensions. Two hours post inoculation, escalating SUL doses (1–200 mg/kg) were administered q8h for 24 h as ampicillin-sulbactam, while control mice received saline. Efficacy was measured as the change in log10 CFU/ lungs at 24 h compared with 0 h controls. PK and ex vivo protein binding of SUL were assessed in infected mice to determine the free systemic exposures of the regimens utilized. The percentages of dosing interval in which the free plasma concentration exceeded the SUL MIC (%fT &amp;gt; MIC) required to achieve 1- and 2-log kill against each isolate were estimated using Hill-equation. Monte Carlo simulations were performed to determine PTA for these endpoints with various clinically-utilized SUL dosing regimens. Mean and standard deviation values for SUL PK parameters were derived from patients with nosocomial pneumonia due to A. baumannii. Results Median (Interquartile range, IQR) %fT &amp;gt; MIC needed for 1-log and 2-log kill at 24 h were 27.36 (19.94 – 35.11) and 48.36 (38.18 – 58.01), respectively. The corresponding PTA following the maximum FDA-approved SUL dose for pneumonia (1g q6h, 0.5 h infusion) and three off-label doses are reported in the table. Conclusion Currently approved dose of SUL for pneumonia (1g q6h, 0.5 h infusion) provides effective exposure against A. baumannii at the current FDA/CLSI susceptibility breakpoint (SUL MIC ≤ 4 mg/L). Higher and/or more frequent SUL dosing provides additional coverage with 3 g q8h extended infusion further enhancing the PK/PD exposure against isolates with SUL MICs up to 16 mg/L. Disclosures Yasmeen Abouelhassan, PhD, Pfizer: spouse salary Joseph L. Kuti, PharmD, Abbvie: Honoraria|bioMeriuex: Advisor/Consultant|bioMeriuex: Grant/Research Support|Contrafect: Grant/Research Support|Entasis: Grant/Research Support|Merck and Co: Grant/Research Support|Roche Diagnostics: Grant/Research Support|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Shionogi: Honoraria|Summit: Grant/Research Support David P. Nicolau, PharmD, Shionogi: Grant/Research Support Kamilia Abdelraouf, PhD, Evopoint Biosciences Co., Ltd: Grant/Research Support|Venatorx Pharmaceuticals, Inc.: Grant/Research Support.

Comparative pharmacokinetics and urinary excretion of arsenic and mercury after oral administration of realgar, cinnabar and AnGongNiuHuang Pill to rats

Realgar- and cinnabar-containing AnGongNiuHuang Pill (AGNHP) is widely used for treating encephalopathy syndrome. However, it raises great safety concerns due to the adverse effects reported by arsenic or mercury poisoning. Although AGNHP has been generally recognized, little is known about the metabolism of arsenic and mercury and their resulting potential health risk in vivo. Thus, comparative pharmacokinetics and urinary excretion of arsenic and mercury were conducted in rats after oral administration of realgar, cinnabar and AGNHP, respectively. The contents of arsenic and mercury in rat blood and urine were determined by hydride-generation atomic fluorescence spectrometry (HG-AFS) after wet digestion. AGNHP significantly reduced the absorption of arsenic in blood and promoted urinary arsenic excretion. Whereas, it increased the blood mercury absorption and reduced urinary mercury excretion. No significant toxicity was observed in the clinical dose range of AGNHP. However, excessive exposure to arsenic and mercury may still pose risks especially by long-term or excessive medication. The results are helpful for the rational clinical applications of realgar- and cinnabar-containing TCMs.

Abstract 3382: Detection of cancer in dogs using a novel genetic-based synthetic biomarker platform

Abstract Early detection of cancer is an important driver of increased survival, quality of life and reduced healthcare costs. Although liquid biopsy provides a new option for early cancer detection, the limitations of detecting a few molecules of blood-based biomarkers naturally shed by the cancer remain. Earli is developing a highly sensitive, orthogonal approach that uses a genetic construct that usurps dysregulated pathways and actively forces cancer cells to drive the expression of a detectable ‘synthetic’ biomarker. We previously used murine xenograft models to validate the tumor detection properties of EARLI-001, a circular DNA containing a human derived cancer-activated promoter to drive the transient expression of secreted embryonic alkaline phosphatase (SEAP), a protein normally expressed only during fetal development. Biodistribution following intravenous (IV) administration of EARLI-001 shows a broad tissue tropism, enabling the potential to monitor multiple tissues for malignant cells. A single dose of EARLI-001 administered in a pulmonary metastatic cancer mouse model resulted in a 95-fold increase in serum SEAP compared to healthy controls. Recognizing the inherent limitations of murine models, we evaluated EARLI-001 in canines diagnosed with cancer. Dog cancers share many features with human malignancies including spontaneous tumor formation, heterogeneity, growth kinetics, histology, and comparable dysregulated genetic pathways. Furthermore, the use of dogs allows the study of EARLI-001 in an immune competent setting and with substantially increased size (up to 65 kg) comparable to scaling into human subjects. EARLI-001 was first tested for safety and biodistribution in 54 purpose-bred beagles in MTD and GLP toxicology studies which reveal that it is safe and well tolerated across a broad range of clinical doses. Biodistribution analysis in 12 tissues showed nanoplasmid levels peaking in the first days post dose and rapidly decreased to background levels by 60 days. These non-tumor bearing dogs showed no serum SEAP signal at all doses. Following IACUC approval and informed owner consent, EARLI-001 was administered to companion dogs in a standard 3 x 3 dose escalation study, with an expanded mid-range cohort. These companion dogs harbored a wide variety of spontaneous tumors in different tissues of origin. In tumor bearing dogs, EARLI-001 elicited a clear and discernable cancer-activated SEAP signal in 1 of 3 dogs dosed at 0.01 mg/kg, 3 of 6 dosed at 0.03 mg/kg, 2 of 2 at 0.07 mg/kg and 8 of 8 dogs dosed at 0.1 mg/kg. Furthermore, the MTD was not reached, and no significant dose-limiting toxicity was observed in these older, disease-burdened animals. These results show the utility of the platform to interrogate tumor biology and detect the presence of malignancies in relevant in vivo models and provided the critical safety and efficacy data towards a first-in-human clinical study in lung cancer initiated in 2021. Citation Format: Regina Nieu, Emily Phenix, Jennifer Hauss, Hadley Hanson, Nga Ho, Alex Harwig, Shireen Rudina, Badri Ananthanarayanan, Hong Chang, Bijee George, Maggie C. Louie, Julie Bulman-Fleming, Michael Kent, David Suhy. Detection of cancer in dogs using a novel genetic-based synthetic biomarker platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3382.

D3S-001, a highly potent, selective, and differentiated covalent inhibitor of KRAS G12C: Human dose prediction and first‐in‐human (FIH) trial design.

e15087 Background: Effective inhibition of G12C mutated KRAS is believed to be critical for anti-tumor efficacy in KRAS-driven cancers. D3S-001 is a potent and highly differentiated KRAS G12C inhibitor, which demonstrates rapid and near complete target inhibition and strong anti-tumor activity in preclinical cell line and animal models [Preclinical characterization of D3S-001, a highly potent, selective, and differentiated covalent inhibitor of KRAS G12C, ASCO 2022 Abstract #378099]. The current study utilizes pharmacokinetic (PK) modeling to predict the extent of KRAS G12C target inhibition at the proposed clinical dose range. Methods: Allometric scaling and non-linear fixed effect modeling were used to predict human PK profiles from DMPK data in animals. Human in vivo target inhibition was calculated based on human PK predictions, free drug fraction and results from in vitro target engagement assay. A First-in-Human (FIH) study was designed to investigate D3S-001 monotherapy in subjects with advanced solid tumors having a KRAS G12C mutation. Six dose escalation cohorts will be investigated, starting from 50mg QD. Results: Based on a GLP toxicology study in dogs, the highest non-severely toxic dose (HNSTD) was determined to be 20 mg/kg/day. Per ICH S9, a 20 mg/kg/day dose in dog supports a FIH starting dose of 110 mg. To ensure an additional safety margin, a lower starting dose of 50 mg was proposed. At 50 mg QD, the predicted human exposure (Cmax 60 nM, Caverage 49 nM, Ctrough 31 nM) is expected to achieve ̃70% target inhibition at 2 hours after dosing. In NCI-H358 mouse xenograft model, this exposure is associated with 94% tumor growth inhibition (TGI). Safety margins based on Cmax and AUC comparing to dog HNSTD are 17-fold and 9-fold, respectively. At 100 mg QD, the predicted human exposure (Cmax 120 nM, Caverage 98 nM, Ctrough 63 nM) is expected to achieve ̃95% target inhibition. This exposure is associated with tumor regression of 72% in the NCI-H358 mouse xenograft model. At dose levels higher than 100 mg QD, predicted human exposures are expected to consistently achieve &gt;95% target inhibition starting 1 hour after dosing. These exposures are associated with deeper levels of tumor regression of 97%. Moreover, even at 400 mg QD, predicted human plasma concentrations are still below dog plasma concentration of 443 nM, Caverage at HNSTD. Conclusions: D3S-001 is predicted to achieve rapid and consistently efficacious KRAS G12C target inhibition in humans at proposed clinical dose range. This high degree of KRAS G12C inhibition over the dosing interval may translate into greater clinical benefit to patients with KRAS G12C mutations comparing with other clinical-stage KRAS G12C inhibitors. Clinical data from the FIH study will be evaluated and compared to preclinical predictions.

Abstract LB127: Prospective preclinical modeling to estimate clinical pharmacokinetics and doses of BDTX-189, an inhibitor of allosteric ErbB mutations in advanced solid malignancies

Abstract Allosteric oncogenic mutations occur outside the canonical ATP-binding site of EGFR and HER2, for which there are no approved single agent therapies that target this family. BDTX-189 is a potent, selective, irreversible inhibitor of the family of nearly 50 allosteric EGFR and HER2 mutant variants. The goal of this translational analysis was to predict the clinical pharmacokinetic (PK) profile of BDTX-189 utilizing in vitro data on the absorption, distribution and metabolism of BDTX-189 as well as in vivo PK data in preclinical species. The prospective PK modeling was conducted prior to initiation of a Phase 1/2 study, to provide predictions of clinical exposures and active dose range. A challenge in the design of irreversible inhibitors with optimal PK properties is the lack of reliable methods to predict their disposition and elimination in human. The PK of covalent drugs is often driven by extrahepatic elimination pathways, and therefore conventional approaches to predict human clearance using human hepatocytes or allometric scaling can lead to poor predictive accuracy. We employed a novel physiologically-based PK (PBPK) modeling strategy that accounted for compound-specific determinants of BDTX-189 metabolism and disposition. PK studies following intravenous (IV) and oral (PO) administration were conducted in preclinical species as well as in vitro studies to understand the ADME properties of BDTX-189. These preclinical data formed the basis of a PBPK modeling approach to predict the likely PK profile of BDTX-189 in human. The mechanistic assumptions used in the final models were able to recapitulate the observed animal PK after both IV and PO administration and thus predictions utilizing similar assumptions for human were considered plausible. Taken together with BDTX-189 exposure-response data in mouse models of anti-tumor efficacy, this enabled the prediction of potentially active dose levels in patients. Preclinical PBPK modeling indicated that BDTX-189 would be readily orally absorbed with a short elimination half-life (approximately 2 hours) while maintaining suppression of ErbB pathway biomarkers over the dosing interval, consistent with the irreversible mechanism of action and the desired ‘hit-and-run' PK/pharmacodynamic (PD) profile. Active dose levels in human were projected to be in the 400 - 800 mg QD range, based on the exposure - tumor growth inhibition relationship in multiple mouse PDX models harboring ErbB allosteric mutations. This study demonstrates that a PBPK modeling approach and an understanding of the determinants of clearance can provide an effective framework for preclinical-to-clinical translation. BDTX-189 is currently under clinical evaluation in the ongoing MasterKey-01 trial (NCT04209465), and clinical PK will be reported in due course. Citation Format: Giorgio Ottaviani, Matthew O'Connor, Alexander Flohr, Darlene Romashko, Alexander Mayweg, Elizabeth Buck, Nigel Waters. Prospective preclinical modeling to estimate clinical pharmacokinetics and doses of BDTX-189, an inhibitor of allosteric ErbB mutations in advanced solid malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB127.

An ultrasensitive LC-MS/MS method and application to clinical dose-range finding for glycopyrrolate via an e-Nebulizer.

Aim: Glycopyrrolate (GLY) has been widely used to treat chronic obstructivepulmonary disease (COPD). Recent technical advancement significantly improves the drug delivery efficiency. In a clinical dose-range determination study via electronic nebulizer, the starting dose was as low as 3-μg, thus, a bioanalytical method capable of measuring down to sub-pg/ml or fg/ml level was required to characterize pharmacokinetics of GLY. Methods: A straightforward solid-phase extraction coupled with reversed-phase LC-MS/MS method was successfully developed to quantify plasma GLY concentrations of 0.500-250 pg/mL. MS/MS detection was at ESI+by monitoring m/z 318.3→116.1 for GLY and 321.3→119.1 for the internal standard GLY-d3. Results and Conclusion: The method was validated with adequate selectivity, intra- and inter-assay precision and accuracy, dilution linearity, and sufficient stability for measuring GLY in human plasma. This method has been used for sample analysis of a clinical dose-range finding study (3-50 µg twice daily doses via an electronic nebulizer). The assay exhibited good precision, accuracy, and robustness. Pharmacokinetic analysis showed good dose proportionalityover the studied dose range, where Cmax was found to be Y = 1.354*X + 1.968 (r2 = 0.9984), and AUC0-12 h was Y = 4.661*X + 23.32 (r2 = 0.9976). The study clearly demonstrated the importance of an ultrasensitive (500 fg/ml LLOQ) method.

EXPOSURE DOSE INDEX BASED ON NOISE FACTOR ANALYSIS IN DIGITAL MAMMOGRAPHY: VERIFICATION USING DIRECT-TYPE FLAT-PANEL DETECTOR SYSTEM.

In this study, the development of a reasonable index of optimized exposure dose is attempted. Using a direct-type flat-panel system, noise factors contained in the image are analyzed based on the relative standard deviation method, and it is verified that the proposed index conforms with the appropriate standards regarding minimum exposure dose. The findings indicate that Poisson noise is dominant in the general clinical dose range; this noise fraction formed 90% of the total noise in the system considered in this study. Considering the results of previous surveys, it is estimated that the point at which the content rate of the Poisson noise starts to decrease can be considered as the lower limit, below which the dose cannot be reduced further without compromising on image quality. As the 'index' obtained by this method can be easily measured, it is useful as a quantitative indicator for dose determination and optimization.

The In Vitro Efficacy of Doxycycline over Vancomycin and Penicillin in the Elimination of Cutibacterium Acnes Biofilm.

Cutibacterium acnes (formerly Propionibacterium acnes) is a significant pathogen in periprosthetic joint infections (PJIs) in total shoulder arthroplasty. Poor outcomes seen in PJIs are due to the established C. acnes bacterial biofilms. The prolonged nature of C. acnes infections makes them difficult to treat with antibiotics. The goal of this study was to determine the relative efficacy of vancomycin compared with penicillin and doxycycline against planktonic and mature biofilms. Clinical isolates from PJI patients as well as a laboratory strain of C. acnes were tested. Planktonic minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were obtained using modified clinical laboratory standard index assays. Biofilm MICs and MBCs were also obtained. The MIC was determined for both using the PrestoBlue viability stain. The MBC was determined using differential reinforced clostridial medium agar plates for colony-forming unit analysis. Using the PrestoBlue viability reagent, the planktonic MIC values for vancomycin were significantly higher than doxycycline. Across 10 strains of C. acnes, all three antibiotics had decreased efficacy when comparing planktonic and biofilm cultures. Although effective antibiotic doses ranged from 1 to 1,000 μg/mL, only doxycycline achieved inhibitory and bactericidal concentrations in all tested strains. Penicillin failed to achieve the minimum biofilm inhibitory concentration (MBIC) in 60% of tested strains, whereas vancomycin failed in 80% of tested strains. Penicillin, doxycycline, and vancomycin have similar abilities in inhibiting C. acnes growth planktonically. The MBIC for doxycycline was within the clinical dosing range, suggesting C. acnes biofilm offers minimal tolerance to these antibiotics. The MBIC for penicillin was within clinical dosing ranges in only 60% of trials, suggesting the relative tolerance of C. acnes to penicillin. The minimum biofilm bactericidal concentration (MBBC) of doxycycline showed efficacy in 90% of trials, whereas penicillin and vancomycin achieved MBBC in 15% of samples.

Abstract 2273: Selection of first-in-human clinical dose range for the tumor-targeted 4-1BB agonist MP0310 (AMG 506) using a pharmacokinetic/pharmacodynamics modeling approach

Abstract Following the clinical success of checkpoint inhibitors, cancer immunotherapy is rapidly expanding into combination treatments to enhance response rates and duration. Engagement of co-stimulatory molecules from the tumor necrosis factor receptor (TNFR) superfamily, including 4-1BB, may be a promising approach to enhance the benefits of cancer immunotherapy. Agonistic antibodies against the costimulatory receptor 4-1BB (CD137) have been shown to effectively enhance the anti-tumor activity of checkpoint inhibitors and other agents in preclinical animal models. However, the clinical development of 4-1BB agonistic antibodies has met with limited success thus far. Anti-4-1BB monoclonal antibodies have either been reported to cause significant dose-limiting hepatotoxicity or demonstrated limited efficacy as single agent therapeutics. We generated a DARPin® therapeutic candidate, MP0310 (AMG 506), which comprises domains binding to 4-1BB and fibroblast activation protein (FAP). MP0310 triggers 4-1BB activation only if bound and clustered via FAP which is abundantly expressed by cancer associated fibroblasts present in many solid tumors. In vitro functional assays indicate that MP0310 is a potent T cell co-stimulator in the presence of FAP-expressing cells. In vivo activity of tumor-targeted 4-1BB agonism was assessed in the HT-29 colon carcinoma xenograft model in PBMC humanized mice in combination with a T cell engager. Consistent with tumor targeting, MP0310 enhanced intra-tumoral CD8 T cell expansion while showing only limited systemic activity. We used a translational pharmacokinetic-pharmacodynamic (PK-PD) modeling approach to integrate in vitro and in vivo data to support the estimation of a minimal anticipated biological effect level (MABEL) and the relevant dose range for first in human (FIH) studies. In addition to a PK model describing the MP0310 concentrations over time in mouse and monkey, direct and indirect response models were used to describe receptor occupancy (RO), intra-tumoral CD8 T cell infiltration and peripheral CD8 count kinetics. Predictions from the combined PK and PD models using average intra-tumoral and peripheral drug concentrations (Cav) provide a MABEL dose with minimal expected systemic PD effects at 20% RO as well as the anticipated therapeutic dose range in humans. In conclusion, our PK/PD-modeling approach provides support for the selection of a safe starting dose for MP0310 (AMG506) in patients. It provides a rationale for selecting the maximum tested dose, and may help reduce the number of cancer patients receiving sub-therapeutic doses. MP0310 (AMG 506) is currently being evaluated in a Ph1 clinical study. Citation Format: Alexander Link, Laurent Juglair, Heïdi Poulet, Guy Lemaillet, Christian Reichen, Patricia Schildknecht, Ivana Tosevski, Joanna Robinson, Niina Veitonmäki, Jörg Herbst, Keith Dawson, Christof Zitt, Camila de Almeida, Rik de Greef, Victor Levitsky, Michael T. Stumpp, Hong Ji, Elmar Vom Baur. Selection of first-in-human clinical dose range for the tumor-targeted 4-1BB agonist MP0310 (AMG 506) using a pharmacokinetic/pharmacodynamics modeling approach [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2273.

Comparison of Noise Equivalent Count Rates (NECRs) for the PET Systems With Different Ring Diameter and Electronics

Because the sensitivity of positron emission tomography (PET) system increases in proportion to the inverse of the diameter of the detector ring, brain PET systems are being planned and developed. However, count losses due to the dead-time of the detector blocks increases as the ring diameter decreases. Since the count losses decrease the noise equivalent count rate (NECR) of the system, the NECR of brain PET system may be lower than that of a whole-body PET system in clinical dose range. In this paper, we compared the NECRs of brain PET systems with that of a whole-body PET system using a Monte Carlo simulation. We simulated the PET system for a 27-cm-diameter detector ring, a 54-cm-diameter detector ring, and an 89-cm-diameter detector ring and evaluated the NECRs. In the clinical dose range, the NECR of the small-diameter brain PET system was lower than those of the whole-body PET system unless the electronics was advanced. We conclude that the small-diameter brain PET system with conventional electronics has not so much advantage except for the lower cost and the higher spatial resolution. However, advanced electronics can reduce degradation of NECR, so the small-diameter brain PET system with advanced electronics will be useful for clinical studies.

Quantitative investigation of hepatobiliary transport of [11C]telmisartan in humans by PET imaging

The pharmacokinetics of telmisartan are nonlinear within the clinical dose range. To identify the underlying mechanism of this nonlinearity, we conducted a PET study in healthy subjects using [11C]telmisartan. Eight healthy male subjects were enrolled in a 2-way crossover study. PET imaging was performed after intravenous administration of [11C]telmisartan with or without a 1-h oral predose of two 40 mg Micardis® tablets. About 60% of the injected [11C]telmisartan accumulated in the liver within 10 min after injection. With predosing of 80 mg telmisartan, the systemic elimination of [11C]telmisartan was slightly delayed, but the liver exposure started to decrease earlier and biliary excretion was greatly enhanced. Hepatic uptake clearance of the radioactivity was not changed by telmisartan predosing, whereas the biliary clearance of radioactivity from the liver was significantly increased. Thus, the alteration in the pharmacokinetics of the radioactivity could not be explained simply by the saturation of hepatic uptake. Therefore, other mechanisms, such as the saturation of intracellular binding of telmisartan and/or its glucuronide, and the glucuronidation of telmisartan by uridine 5′-diphospho-glucuronosyltransferases, should be considered. This is the first reported human PET study using [11C]telmisartan, the results of which can assist understanding of the hepatobiliary transport of telmisartan in humans.

Assessment of Inhibitory Effects of Hypnotics on Acetylcholine-Induced Contractions in Isolated Rat Urinary Bladder Smooth Muscle

The present study aimed to investigate the potential inhibitory effects of 21 clinically available hypnotics on acetylcholine (ACh)-induced contractions in rat urinary bladder smooth muscle (UBSM) in order to predict whether these hypnotics could induce voiding impairment. ACh-induced contraction in rat UBSM was inhibited only by diphenhydramine (a histamine H1 receptor antagonist) at a concentration that was clinically relevant. ACh-induced contraction was also significantly inhibited by flurazepam (a benzodiazepine hypnotic) and suvorexant (an orexin receptor antagonist), albeit at concentrations that substantially exceeded clinically achievable blood levels. These three drugs (at 10-5 M) also inhibited high-KCl (80 mM) Locke-Ringer solution-induced contractions. In contrast to the effects of the abovementioned hypnotics, ACh-induced contractions were not significantly affected by triazolam, etizolam, brotizolam, lormetazepam, estazolam, flunitrazepam, nitrazepam (benzodiazepine hypnotics), thiopental, thiamylal, pentobarbital, amobarbital, secobarbital, phenobarbital (barbiturate hypnotics), zolpidem (an imidazopyridine hypnotic), zopiclone (a cyclopyrrolone hypnotic), ramelteon (a melatonin receptor agonist), bromovalerylurea, and chloral hydrate. These findings suggest that most clinically used hypnotics are not likely to result in anticholinergic-induced dysuria within their clinically achievable blood concentration ranges. Diphenhydramine may, however, induce voiding impairment, an action attributable to diminished UBSM contractility within its clinical dose range.

Balancing RAF, MEK, and EGFR inhibitor doses to achieve clinical responses and modulate toxicity in BRAF V600E colorectal cancer.

Recent years have seen dramatic clinical advances in targeting the ERK pathway with the FDA approval of several selective inhibitors of RAF and MEK1–5. Clinical trials of these agents indicate that near complete inhibition of pathway signaling is necessary to effectively inhibit tumor growth6. Targeted approaches have been most successful in BRAF V600E tumors because of the relatively wide therapeutic index of RAF inhibitors (vemurafenib and dabrafenib), which inhibit signaling in cells with BRAF V600 mutants but cause “paradoxical activation” of ERK signaling in normal cells that are wild-type for RAF kinases. In contrast, MEK inhibitors (trametinib and cobimetinib) suppress ERK signaling in all cells, and their clinical activity has been limited by a narrow therapeutic index. Combining these agents – with RAF and MEK inhibitors for BRAF V600E melanoma or lung cancer and with RAF, MEK, and EGFR inhibitors for BRAF V600E colorectal cancer – to profoundly inhibit ERK signaling has led to improved antitumor activity7. Combination therapy has also been shown to offset the toxicities caused by RAF inhibitors, such as the development of keratoacanthomas and squamous cell carcinoma, resulting from paradoxical ERK activation with these agents. The role of RAF inhibitors to offset MEK inhibitor toxicity and the need for dose intensity to modulate opposing toxicities is less clear. Recent observations in clinical trials have suggested that RAF inhibitors offset dermatologic toxicity from MEK or EGFR inhibitors. In the phase III trial of trametinib in melanoma, grade 3 or 4 acneiform dermatitis occurred in 8% of trametinib-treated patients, whereas in the phase III trial of the combination of dabrafenib and trametinib, no patient had grade 3 or 4 acneiform dermatitis8,9. Combinations of RAF and EGFR inhibitors have also had a lower incidence of acneiform rash than seen with EGFR inhibitors alone7,10,11. This is also likely due to the opposite effects of RAF and EGFR inhibitors on MEK activation in normal cells. However, the doses of RAF inhibitors needed for these clinically opposing effects and how these doses compare to clinically efficacious doses have not been studied. We now report the course of a patient with BRAF V600E CRC treated with dabrafenib, trametinib, and panitumumab in a phase II clinical trial, and within this patient characterize the effect on toxicities of different dose levels of these agents. Further, we find that, within the clinical dose range, there is a RAF inhibitor dose that is an inflection point for the toxicity and efficacy of this regimen.

Comparison of Dopamine D3 and D2 Receptor Occupancies by a Single Dose of Blonanserin in Healthy Subjects: A Positron Emission Tomography Study With [11C]-(+)-PHNO

BackgroundBlockade of D3 receptor, a member of the dopamine D2-like receptor family, has been suggested as a possible medication for schizophrenia. Blonanserin has high affinity in vitro for D3 as well as D2 receptors. We investigated whether a single dose of 12 mg blonanserin, which was within the daily clinical dose range (i.e., 8–24 mg) for the treatment of schizophrenia, occupies D3 as well as D2 receptors in healthy subjects.MethodsSix healthy males (mean 35.7±7.6 years) received 2 positron emission tomography scans, the first prior to taking blonanserin, and the second 2 hours after the administration of a single dose of 12 mg blonanserin. Dopamine receptor occupancies by blonanserin were evaluated by [11C]-(+)-PHNO.ResultsOccupancy of each region by 12 mg blonanserin was: caudate (range 64.3%–81.5%; mean±SD, 74.3±5.6%), putamen (range 60.4%–84.3%; mean±SD, 73.3%±8.2%), ventral striatum (range 40.1%–88.2%; mean±SD, 60.8%±17.1%), globus pallidus (range 65.8%–87.6%; mean±SD, 75.7%±8.6%), and substantia nigra (range 56.0%–88.7%; mean±SD, 72.4%±11.0%). Correlation analysis between plasma concentration of blonanserin and receptor occupancy in D2-rich (caudate and putamen) and D3-rich (globus pallidus and substantia nigra) regions showed that EC50 for D2-rich region was 0.39 ng/mL (r=0.43) and EC50 for D3-rich region was 0.40 ng/mL (r=0.79).ConclusionsA single dose of 12 mg blonanserin occupied D3 receptor to the same degree as D2 receptor in vivo. Our results were consistent with previous studies that reported that some of the pharmacological effect of blonanserin is mediated via D3 receptor antagonism.

Silver nitrate based gel dosimeter

A new radiochromic gel dosimeter based on silver nitrate and a normoxic gel dosimeter was investigated using UV-Visible spectrophotometry in the clinical dose range. Gamma radiation induced the synthesis of silver nanoparticles in the gel and is confirmed from the UV-Visible spectrum which shows an absorbance peak at around 450 nm. The dose response function of the dosimeter is found to be linear upto12Gy. In addition, the gel samples were found to be stable which were kept under refrigeration.

Cerium nanoparticle effect on sensitivity of Fricke gel dosimeter: Initial investigation

Fricke gel dosimeters (FXGs) have been the preferred dosimeters because of its ease in preparation and water and tissue equivalency. Visible changes happen three dimensionally in the dosimeter as the ferrous (Fe2+) ions change into ferric (Fe3+) ions upon irradiation and the measure of this change can be correlated to the dose absorbed. Nanoparticles are promising entities that can improve the sensitivity of the gel dosimeter. Cerium Oxide nanoparticle was investigated for possible enhancement of absorbed dose in the FXG. Various concentrations of the nanoparticle based gel dosimeters were prepared and irradiated for a clinical dose range of 0-3 Gy in a telegamma unit. The optimal concentration of 0.1 mM nanoparticle incorporated in the FXG enhances the radiation sensitivity of the unmodified FXG taken as reference without modifying the background absorbance prior to irradiation. The gel recipe consisted of 5% (wt) gelatin, 50 mM Sulphuric acid, 0.05 mM Xylenol Orange, 0.5 mM Ferrous Ammonium Sulphate and 0.1 mM Cerium (IV) Oxide nanoparticle (< 25 nm particle size) and triple distilled water. The FXGs with nanoparticle showed linear dose response in the dose range tested.