Population Pharmacokinetic/Pharmacodynamic Analysis of the Glucokinase Activator PB201 in Healthy Volunteers and Patients with Type 2 Diabetes Mellitus: Facilitating the Clinical Development of PB201 in China

PB201 is an orally active, partial glucokinase activator targeting both pancreatic and hepatic glucokinase. As the second glucokinase activator studied beyond phase I, PB201 has demonstrated promising glycemic effects as well as favorable pharmacokinetic (PK) and safety profiles in patients with type 2 diabetes mellitus (T2DM). This study aims to develop a population PK/pharmacodynamic (PD) model for PB201 using the pooled data from nine phase I/II clinical trials conducted in non-Chinese healthy volunteers and a T2DM population and to predict the PK/PD profile of PB201 in a Chinese T2DM population. We developed the PK/PD model using the non-linear mixed-effects modeling approach. All runs were performed using the first-order conditional estimation method with interaction. The pharmacokinetics of PB201 were well fitted by a one-compartment model with saturable absorption and linear elimination. The PD effects of PB201 on reducing the fasting plasma glucose and glycosylated hemoglobin levels in the T2DM population were described by indirect response models as stimulating the elimination of fasting plasma glucose, where the production of glycosylated hemoglobin was assumed to be stimulated by fasting plasma glucose. Covariate analyses revealed enhanced absorption of PB201 by food and decreased systemic clearance with ketoconazole co-administration, while no significant covariate was identified for the pharmacodynamics. The population PK model established for non-Chinese populations was shown to be applicable to the Chinese T2DM population as verified by the PK data from the Chinese phase I study. The final population PK/PD model predicted persistent and dose-dependent reductions in fasting plasma glucose and glycosylated hemoglobin levels in the Chinese T2DM population receiving 50/50 mg, 100/50 mg, and 100/100 mg PB201 twice daily for 24 weeks independent of co-administration of metformin. Overall, the proposed population PK/PD model quantitatively characterized the PK/PD properties of PB201 and the impact of covariates on its target populations, which allows the leveraging of extensive data in non-Chinese populations with the limited data in the Chinese T2DM population to successfully supported the waiver of the clinical phase II trial and facilitate the optimal dose regimen design of a pivotal phase III study of PB201 in China.

Empirical scaling factor for predicting human pharmacokinetic profiles of disproportionate metabolites using the Css-MRTpo method and chimeric mice with humanised livers

Predicting plasma concentration-time profiles of disproportionate metabolites in humans is crucial for evaluating metabolites according to the Safety Testing guidelines. We evaluated Css-MRTpo, an empirical method, using chimeric mice with humanised livers capable of generating human-disproportionate metabolites. Azilsartan and AZ-M2 were administered to humanised chimeric mice, and pharmacokinetic parameters were obtained. Pharmacokinetic data for DS-1971a and DS-M1 in humanised chimeric mice were obtained from the literature. The human plasma concentration-time profiles of these compounds were simulated using the Css-MRTpo method. Azilsartan, DS-1971a, and PF-04937319 produced human disproportionate metabolites, AZ-M2, DS-M1, and PF-M1, respectively. The predicted human pharmacokinetic profiles of PF-04937319 and PF-M1 were obtained from a previous study, and their outcomes were re-evaluated. Our findings revealed that the plasma concentrations of the three metabolites were unexpectedly underpredicted, whereas the three unchanged drugs were reasonably predicted. Further, the introduction of the empirical scaling factor of 3, obtained from six model compounds, improved the predictability of metabolites, suggesting the potential usefulness of the Css-MRTpo method in combination with humanised chimeric mice for predicting the pharmacokinetic profiles of disproportionate metabolites at the early stage of new drug development.

Development of a PBPK model to quantitatively understand absorption and disposition mechanism and support future clinical trials for PB-201

PB-201 is the second glucokinase activator in the world to enter the phase III clinical trials for the treatment of type 2 diabetes mellitus (T2DM). Combined with the efficacy advantages and the friendly absorption, distribution, metabolism, and excretion characteristics, the indication population of PB-201 will be broad. Because the liver is the primary organ for PB-201 elimination, and the elderly account for 20% of patients with T2DM, it is essential to estimate PB-201 exposure in specific populations to understand the pharmacokinetic characteristics and avoid hypoglycemia. Despite the limited contribution of CYP3A4 to PB-201 metabolism in vivo, the dual effects of nonspecific inhibitors/inducers on PB-201 (substrate for CYP3A4 and CYP2C9 isoenzymes) exposure under fasted and fed states also need to be evaluated to understand potential risks of combination therapy. To grasp the unknown information, the physiologically-based pharmacokinetic (PBPK) model was first developed and the influence of internal and external factors on PB-201 exposure was evaluated. Results are shown that the predictive performance of the mechanistic PBPK model meets the predefined criteria, and can accurately capture the absorption and disposition characteristics. Impaired liver function and age-induced changes in physiological factors may significantly increase the exposure under fasted state by 36%-158% and 48%-82%, respectively. The nonspecific inhibitor (fluconazole) and inducer (rifampicin) may separately increase/decrease PB-201 systemic exposure by 44% and 58% under fasted state, and by 78% and 47% under fed state. Therefore, the influence of internal and external factors on PB-201 exposure deserves attention, and the precision dose can be informed in future clinical studies based on the predicted results.

Biotransformation Novel Advances - 2021 year in review

Biotransformation field is constantly evolving with new molecular structures and discoveries of metabolic pathways that impact efficacy and safety. Recent review by Kramlinger et al (2022) nicely captures the future (and the past) of highly impactful science of biotransformation (see the first article). Based on the selected articles, this review was categorized into three sections: (1) new modalities biotransformation, (2) drug discovery biotransformation, and (3) drug development biotransformation (Table 1).

Dorzagliatin add-on therapy to metformin in patients with type 2 diabetes: a randomized, double-blind, placebo-controlled phase 3 trial

Metformin, the first-line therapy for type 2 diabetes (T2D), decreases hepatic glucose production and reduces fasting plasma glucose levels. Dorzagliatin, a dual-acting orally bioavailable glucokinase activator targeting both the pancreas and liver glucokinase, decreases postprandial glucose in patients with T2D. In this randomized, double-blind, placebo-controlled phase 3 trial, the efficacy and safety of dorzagliatin as an add-on therapy to metformin were assessed in patients with T2D who had inadequate glycemic control using metformin alone. Eligible patients with T2D (n = 767) were randomly assigned to receive dorzagliatin or placebo (1:1 ratio) as an add-on to metformin (1,500 mg per day) for 24 weeks of double-blind treatment, followed by 28 weeks of open-label treatment with dorzagliatin for all patients. The primary efficacy endpoint was the change in glycated hemoglobin (HbA1c) levels from baseline to week 24, and safety was assessed throughout the trial. At week 24, the least-squares mean change from baseline in HbA1c (95% confidence interval (CI)) was -1.02% (-1.11, -0.93) in the dorzagliatin group and -0.36% (-0.45, -0.26) in the placebo group (estimated treatment difference, -0.66%; 95% CI: -0.79, -0.53; P < 0.0001). The incidence of adverse events was similar between groups. There were no severe hypoglycemia events or drug-related serious adverse events in the dorzagliatin and metformin combined therapy group. In patients with T2D who experienced inadequate glycemic control with metformin alone, dorzagliatin resulted in effective glycemic control with good tolerability and safety profile ( NCT03141073 ).

CYP2C8-Mediated Formation of a Human Disproportionate Metabolite of the Selective NaV1.7 Inhibitor DS-1971a, a Mixed Cytochrome P450 and Aldehyde Oxidase Substrate

Predicting human disproportionate metabolites is difficult, especially when drugs undergo species-specific metabolism mediated by cytochrome P450s (P450s) and/or non-P450 enzymes. This study assessed human metabolites of DS-1971a, a potent Na_v1.7-selective blocker, by performing human mass balance studies and characterizing DS-1971a metabolites, in accordance with the Metabolites in Safety Testing (MIST) guidance. In addition, we investigated the mechanism by which the major human disproportionate metabolite (M1) was formed. After oral administration of radiolabeled DS-1971a, the major metabolites in human plasma were P450-mediated monoxidized metabolites M1 and M2 with area under the curve ratios of 27% and 10% of total drug-related exposure, respectively; the minor metabolites were dioxidized metabolites produced by aldehyde oxidase and P450s. By comparing exposure levels of M1 and M2 between humans and safety assessment animals, M1 but not M2 was found to be a human disproportionate metabolite, requiring further characterization under the MIST guidance. Incubation studies with human liver microsomes indicated that CYP2C8 was responsible for the formation of M1. Docking simulation indicated that, in the formation of M1 and M2, there would be hydrogen bonding and/or electrostatic interactions between the pyrimidine and sulfonamide moieties of DS-1971a and amino acid residues Ser100, Ile102, Ile106, Thr107, and Asn217 in CYP2C8, and that the cyclohexane ring of DS-1971a would be located near the heme iron of CYP2C8. These results clearly indicate that M1 is the predominant metabolite in humans and a human disproportionate metabolite due to species-specific differences in metabolism. Significance Statement This report is the first to show a human disproportionate metabolite generated by CYP2C8-mediated primary metabolism. We clearly demonstrate that DS-1971a, a mixed aldehyde oxidase and cytochrome P450 substrate, was predominantly metabolized by CYP2C8 to form M1, a human disproportionate metabolite. Species differences in the formation of M1 highlight the regio- and stereoselective metabolism by CYP2C8, and the proposed interaction between DS-1971a and CYP2C8 provides new knowledge of CYP2C8-mediated metabolism of cyclohexane-containing substrates.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of the glucokinase activator PB-201 and its effects on the glucose excursion profile in drug-naïve Chinese patients with type 2 diabetes: a randomised controlled, crossover, single-centre phase 1 trial

BACKGROUND

PB-201, a partial, pancreas/liver-dual glucokinase activator, showed good tolerance and glycaemic effects in multinational studies. This study determined its optimal dose, safety, pharmacokinetics, and pharmacodynamics in Chinese patients with type 2 diabetes.

METHODS

In this double-blind, randomised, four-period, crossover, phase 1 trial in China, conducted at the Peking University Third Hospital, adult patients with drug-naive type 2 diabetes were randomised (1:1:1:1) to four sequence groups using a computer-generated randomisation table. In each period, they received oral placebo or PB-201 (50+50, 100+50, or 100+100 mg split doses) for 7 days. Investigators and patients were masked to treatment assignment. The primary endpoints were safety and pharmacokinetics. Continuous glucose monitoring was used to delineate the glucose excursion profile. Trial registration number: NCT03973515.

FINDINGS

Between August 27, 2019 and December 19, 2019, 16 patients were randomised. PB-201 showed a dose-proportional pharmacokinetic profile without apparent accumulation in the body and induced dose-dependent lowering of blood glucose. PB-201 at 50+50, 100+50, and 100+100 mg increased mean time in range (49·210% [standard deviation 27], 56·130% [25], and 63·330% [20] with three doses, respectively) versus placebo (49·380% [27]) and reduced estimated glycated haemoglobin from baseline (-0·5445% [1·654], -1·063% [1·236], and -1·888% [1·381] vs -0·581% [1·200]). Fifteen patients (93·8%) had treatment-emergent adverse events, which were mild. No patients had hypoglycaemia with venous/capillary glucose <3·9 mmol/L or nocturnal hypoglycaemia.

INTERPRETATION

PB-201 100 mg twice daily is identified as the optimal dose, which shows promising glucose-lowering effects and low risks of hypoglycaemia and other side effects. Further investigation of PB-201 100 mg twice daily in confirmatory trials is warranted.

FUNDING

PegBio.

Physiologically Based Pharmacokinetic Models Predicting Renal and Hepatic Concentrations of Industrial Chemicals after Virtual Oral Doses in Rats

Recently developed high-throughput in vitro assays in combination with computational models could provide alternatives to animal testing. The purpose of the present study was to model the plasma, hepatic, and renal pharmacokinetics of approximately 150 structurally varied types of drugs, food components, and industrial chemicals after virtual external oral dosing in rats and to determine the relationship between the simulated internal concentrations in tissue/plasma and their lowest-observed-effect levels. The model parameters were based on rat plasma data from the literature and empirically determined pharmacokinetics measured after oral administrations to rats carried out to evaluate hepatotoxic or nephrotic potentials. To ensure that the analyzed substances exhibited a broad diversity of chemical structures, their structure-based location in the chemical space underwent projection onto a two-dimensional plane, as reported previously, using generative topographic mapping. A high-throughput in silico one-compartment model and a physiologically based pharmacokinetic (PBPK) model consisting of chemical receptor (gut), metabolizing (liver), central (main), and excreting (kidney) compartments were developed in parallel. For 159 disparate chemicals, the maximum plasma concentrations and the areas under the concentration-time curves obtained by one-compartment models and modified simple PBPK models were closely correlated. However, there were differences between the PBPK modeled and empirically obtained hepatic/renal concentrations and plasma maximal concentrations/areas under the concentration-time curves of the 159 chemicals. For a few compounds, the lowest-observed-effect levels were available for hepatotoxicity and nephrotoxicity in the Hazard Evaluation Support System Integrated Platform in Japan. The areas under the renal or hepatic concentration-time curves estimated using PBPK modeling were inversely associated with these lowest-observed-effect levels. Using PBPK forward dosimetry could provide the plasma/tissue concentrations of drugs and chemicals after oral dosing, thereby facilitating estimates of nephrotoxic or hepatotoxic potential as a part of the risk assessment.

A novel Css-MRTpo approach to simulate oral plasma concentration-time profiles of the partial glucokinase activator PF-04937319 and its disproportionate N-demethylated metabolite in humans using chimeric mice with humanized livers

A Css-MRTpo superposition method was devised to predict (retrospectively) oral plasma concentration-time profiles of PF-04937319 and its MIST-related metabolite, M1, in humans using chimeric mice with humanized liver.Original PK data were taken from a published report in which PF-04937319 and M1 were given to chimeric mice orally and/or intravenously. Human CL and Vss were predicted by single-species allometry and MRTiv,pred were calculated as Vss,pred/CL,pred. MRTpo,human were assumed to be MRTiv,pred plus MAT or mean metabolite formation time (MFT). Human Css was calculated by dividing the corrected oral dose by Vss,pred.Chronological sampling time and measured plasma concentrations were corrected by MRTpo,human and Css,human, respectively, and transformed to the corresponding values in humans.The obtained concentration-time profile of PF-04937319 was superimposed well with the observed data after single and repeated oral administration to humans. The transformed plasma concentration of M1 was somewhat lower than the observed value, but a slow increase of the simulated metabolite reflected gradual increase of observed M1 on Day 1. Transformed M1 gave an almost-flat concentration-time profile on Day 14, which was consistent with the curve observed in humans. Application of this novel method to other MIST-related compounds is discussed.

Metabolism and excretion of (S)-6-(3-cyclopentyl-2-(4-trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic acid (PF-04991532), a hepatoselective glucokinase activator, in humans: confirmation of the MIST potential noted in first-in-Human metabolite scouting studies

1. The absorption, metabolism, and excretion of a single oral 450-mg dose of [¹⁴C]-(S)-6-(3-cyclopentyl-2-(4-trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic acid (PF-04991532), a hepatoselective glucokinase activator, was investigated in humans. Mass balance was achieved with ∼94.6% of the administered dose recovered in urine and feces. The total administered radioactivity excreted in feces and urine was 70.6% and 24.1%, respectively. Unchanged PF-04991532 collectively accounted for ∼47.2% of the dose excreted in feces and urine, suggestive of moderate metabolic elimination in humans. 2. The biotransformation pathways involved acyl glucuronidation (M1), amide bond hydrolysis (M3), and CYP3A4-mediated oxidative metabolism on the cyclopentyl ring in PF-04991532 yielding monohydroxylated isomers (M2a-d). Unchanged PF-04991532 was the major circulating component (64.4% of total radioactivity) whereas M2a-d collectively represented 28.9% of the total plasma radioactivity. 3. Metabolites M2a-d were not detected systemically in rats and dogs, the preclinical species for the toxicological evaluation of PF-04991532. In contrast, cynomologus monkeys dosed orally with unlabeled PF-04991532 revealed M2a-d in circulation, whose UV abundance was comparable to the profile in humans. This observation suggested that monkeys could potentially serve as a non-rodent alternative for studying the toxicity of PF-04991532 and its metabolites M2a-d. 4. The present results are in excellent agreement with our previously generated metabolite scouting data, which provided preliminary evidence for the disproportionate metabolism of PF-04991532 in humans.

Plasma and Hepatic Concentrations of Chemicals after Virtual Oral Administrations Extrapolated Using Rat Plasma Data and Simple Physiologically Based Pharmacokinetic Models

Only a small fraction of chemicals possesses adequate in vivo toxicokinetic data for assessing potential hazards. The aim of the present study was to model the plasma and hepatic pharmacokinetics of more than 50 disparate types of chemicals and drugs after virtual oral administrations in rats. The models were based on reported pharmacokinetics determined after oral administration to rats. An inverse relationship was observed between no-observed-effect levels after oral administration and chemical absorbance rates evaluated for cell permeability ( r = -0.98, p < 0.001, n = 17). For a varied selection of more than 30 chemicals, the plasma concentration curves and the maximum concentrations obtained using a simple one-compartment model (recently recommended as a high-throughput toxicokinetic model) and a simple physiologically based pharmacokinetic (PBPK) model (consisting of chemical receptor, metabolizing, and central compartments) were highly consistent. The hepatic and plasma concentrations and the hepatic and plasma areas under the concentration-time curves of more than 50 chemicals were roughly correlated; however, differences were evident between the PBPK-modeled values in livers and empirically obtained values in plasma. Of the compounds selected for analysis, only seven had the lowest observed effect level (LOEL) values for hepatoxicity listed in the Hazard Evaluation Support System Integrated Platform in Japan. For these seven compounds, the LOEL values and the areas under the hepatic concentration-time curves estimated using PBPK modeling were inversely correlated ( r = -0.78, p < 0.05, n = 7). This study provides important information to help simulate the high hepatic levels of potent hepatotoxic compounds. Using suitable PBPK parameters, the present models could estimate the plasma/hepatic concentrations of chemicals and drugs after oral doses using both PBPK forward and reverse dosimetry, thereby indicating the potential value of this modeling approach in predicting hepatic toxicity as a part of risk assessments of chemicals absorbed in the human body.

Dorzagliatin (HMS5552), a novel dual-acting glucokinase activator, improves glycaemic control and pancreatic β-cell function in patients with type 2 diabetes: A 28-day treatment study using biomarker-guided patient selection

AIMS

To investigate the pharmacokinetics and pharmacodynamics of a dual-acting glucokinase activator, dorzagliatin, and its safety, tolerability and effect on pancreatic β-cell function in Chinese patients with type 2 diabetes (T2D).

MATERIALS AND METHODS

A total of 24 T2D patients were selected, utilizing a set of predefined clinical biomarkers, and were randomized to receive dorzagliatin 75 mg twice or once daily (BID, QD respectively) for 28 days. Changes in HbA1c and glycaemic parameters from baseline to Day 28 were assessed. In addition, changes in β-cell function from baseline to Day 32 were evaluated.

RESULTS

Significant reductions in HbA1c were observed in both regimens on Day 28 (-0.79%, 75 mg BID; -1.22%, 75 mg QD). Similar trends were found in the following parameters, including reductions from baseline in fasting plasma glucose by 1.20 mmol/L and 1.51 mmol/L, in 2-hour postprandial glucose by 2.48 mmol/L and 5.03 mmol/L, and in glucose AUC_0-24 by 18.59% and 20.98%, for the BID and QD groups, respectively. Both regimens resulted in improvement in β-cell function as measured by steady state HOMA 2 parameter, %B, which increased by 36.31% and 40.59%, and by dynamic state parameter, ΔC₃₀ /ΔG₃₀ , which increased by 24.66% and 167.67%, for the BID and QD groups, respectively. Dorzagliatin was well tolerated in both regimens, with good pharmacokinetic profiles.

CONCLUSIONS

Dorzagliatin treatment for 28 days in Chinese T2D patients, selected according to predefined biomarkers, resulted in significant improvement in β-cell function and glycaemic control. The safety and pharmacokinetic profile of dorzagliatin supports a subsequent Phase II trial design and continued clinical development.

Simulation of human plasma concentration-time profiles of the partial glucokinase activator PF-04937319 and its disproportionate N-demethylated metabolite using humanized chimeric mice and semi-physiological pharmacokinetic modeling

1. The partial glucokinase activator N,N-dimethyl-5-((2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl)benzofuran-4-yl)oxy)pyrimidine-2-carboxamide (PF-04937319) is biotransformed in humans to N-methyl-5-((2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl)benzofuran-4-yl)oxy)pyrimidine-2-carboxamide (M1), accounting for ∼65% of total exposure at steady state. 2. As the disproportionately abundant nature of M1 could not be reliably predicted from in vitro metabolism studies, we evaluated a chimeric mouse model with humanized liver on TK-NOG background for its ability to retrospectively predict human disposition of PF-04937319. Since livers of chimeric mice were enlarged by hyperplasia and contained remnant mouse hepatocytes, hepatic intrinsic clearances normalized for liver weight, metabolite formation and liver to plasma concentration ratios were plotted against the replacement index by human hepatocytes and extrapolated to those in the virtual chimeric mouse with 100% humanized liver. 3. Semi-physiological pharmacokinetic analyses using the above parameters revealed that simulated concentration curves of PF-04937319 and M1 were approximately superimposed with the observed clinical data in humans. 4. Finally, qualitative profiling of circulating metabolites in humanized chimeric mice dosed with PF-04937319 or M1 also revealed the presence of a carbinolamide metabolite, identified in the clinical study as a human-specific metabolite. The case study demonstrates that humanized chimeric mice may be potentially useful in preclinical discovery towards studying disproportionate or human-specific metabolism of drug candidates.