Prediction of human pharmacokinetics of panipenem-betamipron, a new carbapenem, from animal data

Examination of Urinary Excretion of Unchanged Drug in Humans and Preclinical Animal Models: Increasing the Predictability of Poor Metabolism in Humans

PURPOSE

A dataset of fraction excreted unchanged in the urine (fe) values was developed and used to evaluate the ability of preclinical animal species to predict high urinary excretion, and corresponding poor metabolism, in humans.

METHODS

A literature review of fe values in rats, dogs, and monkeys was conducted for all Biopharmaceutics Drug Disposition Classification System (BDDCS) Class 3 and 4 drugs (n=352) and a set of Class 1 and 2 drugs (n=80). The final dataset consisted of 202 total fe values for 135 unique drugs. Human and animal data were compared through correlations, two-fold analysis, and binary classifications of high (fe ≥30%) versus low (<30%) urinary excretion in humans. Receiver Operating Characteristic curves were plotted to optimize animal fe thresholds.

RESULTS

Significant correlations were found between fe values for each animal species and human fe (p<0.05). Sixty-five percent of all fe values were within two-fold of human fe with animals more likely to underpredict human urinary excretion as opposed to overpredict. Dogs were the most reliable predictors of human fe of the three animal species examined with 72% of fe values within two-fold of human fe and the greatest accuracy in predicting human fe ≥30%. ROC determined thresholds of ≥25% in rats, ≥19% in dogs, and ≥10% in monkeys had improved accuracies in predicting human fe of ≥30%.

CONCLUSIONS

Drugs with high urinary excretion in animals are likely to have high urinary excretion in humans. Animal models tend to underpredict the urinary excretion of unchanged drug in humans.

Evaluation of Prediction Accuracy for Volume of Distribution in Rat and Human Using In Vitro, In Vivo, PBPK and QSAR Methods

Volume of distribution at steady state (V_ss) is an important pharmacokinetic parameter of a drug candidate. In this study, V_ss prediction accuracy was evaluated by using: (1) seven methods for rat with 56 compounds, (2) four methods for human with 1276 compounds, and (3) four in vivo methods and three Kp (partition coefficient) scalar methods from scaling of three preclinical species with 125 compounds. The results showed that the global QSAR models outperformed the PBPK methods. Tissue fraction unbound (f_u,t) method with adipose and muscle also provided high V_ss prediction accuracy. Overall, the high performing methods for human V_ss prediction are the global QSAR models, Øie-Tozer and equivalency methods from scaling of preclinical species, as well as PBPK methods with Kp scalar from preclinical species. Certain input parameter ranges rendered PBPK models inaccurate due to mass balance issues. These were addressed using appropriate theoretical limit checks. Prediction accuracy of tissue Kp were also examined. The f_u,t method predicted Kp values more accurately than the PBPK methods for adipose, heart and muscle. All the methods overpredicted brain Kp and underpredicted liver Kp due to transporter effects. Successful V_ss prediction involves strategic integration of in silico, in vitro and in vivo approaches.

Prediction of Human Pharmacokinetics of Fomepizole from Preclinical Species Pharmacokinetics Based on Normalizing Time Course Profiles

Fomepizole is used as an antidote to treat methanol poisoning due to its selectivity towards alcohol dehydrogenase. In the present study, the goal is to develop a method to predict the fomepizole human plasma concentration versus time profile based on the preclinical pharmacokinetics using the assumption of superimposability on simulated time course profiles of animals and humans. Standard allometric equations with/without correction factors were also assimilated in the prediction. The volume of distribution at steady state (Vss) predicted by simple allometry (57.55 L) was very close to the reported value (42.17 L). However, clearance (CL) prediction by simple allometry was at least 3-fold higher to the reported value (33.86 mL/min); hence, multiple correction factors were used to predict the clearance. Both brain weight and maximum life span potential could predict the CL with 1.22- and 1.01-fold difference. Specifically, the predicted Vss and CL values via interspecies scaling were used in the prediction of series of human intravenous pharmacokinetic parameters, while the simulation of human oral profile was done by the use of absorption rate constant (Ka) from dog following the applicability of human bioavailability value scaled from dog data. In summary, the findings indicate that the utility of diverse allometry approaches to derive the human pharmacokinetics of fomepizole after intravenous/oral dosing.

Pharmacokinetics of β-Lactam Antibiotics: Clues from the Past To Help Discover Long-Acting Oral Drugs in the Future

β-Lactams represent perhaps the most important class of antibiotics yet discovered. However, despite many years of active research, none of the currently approved drugs in this class combine oral activity with long duration of action. Recent developments suggest that new β-lactam antibiotics with such a profile would have utility in the treatment of tuberculosis. Consequently, the historical β-lactam pharmacokinetic data have been compiled and analyzed to identify possible directions and drug discovery strategies aimed toward new β-lactam antibiotics with this profile.

Interspecies scaling and prediction of human clearance: comparison of small- and macro-molecule drugs

Human clearance prediction for small- and macro-molecule drugs was evaluated and compared using various scaling methods and statistical analysis. Human clearance is generally well predicted using single or multiple species simple allometry for macro- and small-molecule drugs excreted renally. The prediction error is higher for hepatically eliminated small-molecules using single or multiple species simple allometry scaling, and it appears that the prediction error is mainly associated with drugs with low hepatic extraction ratio (Eh). The error in human clearance prediction for hepatically eliminated small-molecules was reduced using scaling methods with a correction of maximum life span (MLP) or brain weight (BRW). Human clearance of both small- and macro-molecule drugs is well predicted using the monkey liver blood flow method. Predictions using liver blood flow from other species did not work as well, especially for the small-molecule drugs.

Application of fixed exponent 0.75 to the prediction of human drug clearance: an inaccurate and misleading concept

Considering the controversy surrounding the exponent of 0.75 for the prediction of human drug clearance and lack of any systematic evaluation of the aforementioned proposal, the objective of this study was to determine whether the exponent 0.75 is indeed the most suitable exponent for the prediction of human drug clearance as compared to allometric scaling using the rule of exponents (ROE). Three methods were used to predict human drug clearance. Besides evaluating the exponent of 0.75, an arbitrarily selected exponent of 0.65 was also tested. ROE was also used to predict human drug clearance, and predicted values by all three methods were compared with observed human drug clearance. The results indicate that the exponent 0.75 is not the best approach for the prediction of human drug clearance. Both exponents 0.75 and 0.65 predicted human drug clearance with uncertainty, although on average the prediction of human drug clearance by 0.65 was better than the exponent 0.75. ROE provided far more accurate prediction of human drug clearance than either of the exponents. Although exponent 0.75 occasionally provided a good prediction of human drug clearance for a given drug for a given species, overall, the method is highly erratic and unreliable.

Preparation of aromatic β-Selenolactams and their bioactivities as agricultural chemicals

The purpose of this study was to investigate the possibility of aromatic beta-selenolactams being used in agricultural chemicals. A series of beta-selenolactams with aromatic substituents at the 1-, 2- and 3-positions were synthesized and their bioactivities were evaluated. Acarianicidal and insecticidal activity against common destructive insects, antibacterial activity against seven common plant pathogens, and plant growth activity of typical food crops were investigated. We found that introduction of 4-chloro and 4-methyl groups on 2- or 3-phenyl groups of the beta-selenolactam ring brought about acarianicidal activity against adults and eggs of Plutella xylostella. However, except for moderate to weak effect on fatality of Culex pipiens molestus Forskal, insecticidal activity against two other kinds of insects, antibacterial activity against plant pathogens, and activity on plant growth regulation were not detected among the beta-selenolactam derivatives.

Population Pharmacokinetic Analysis of Panipenem/Betamipron in Patients with Various Degrees of Renal Function

BACKGROUND

Although plasma concentrations of panipenem were elevated and the risk of adverse events would increase in patients with renal impairment, a precise dosage regimen for patients with renal impairment has not been established.

METHODS

Population pharmacokinetic analyses were performed with plasma concentrations from 26 healthy volunteers and 41 patients. Optimal dosage regimens for patients with renal impairment were determined based on the bacteriostatic index of C(20%T)>(MIC), the concentration corresponding to the time above MIC of 20% of the dosing interval.

RESULTS

The clearance of panipenem and betamipron was correlated with creatinine clearance and the volume of the distribution of panipenem was correlated with body weight. C(20%T)>(MIC) for a standard dosage regimen of panipenem was 4.3 microg/ml, and the optimal dosage regimen for the patients was established based on this value.

CONCLUSION

The dosage regimen of panipenem for patients with renal impairment should be reduced when creatinine clearance is lower than 60 ml/min.

Quantitative Evaluation of Effect of Renal Failure on the Pharmacokinetics of Panipenem in Rats

The pharmacokinetics of panipenem in experimental renal failure animal models was investigated in order to identify the appropriate covariates affecting the pharmacokinetic behavior. Panipenem and betamipron were administered intravenously to rats with a variety of renal failures, such as nephritis induced by glycerol, gentamicin, uranium and antiserum against glomerular basement membrane as well as 5/6 subtotal nephrectomy. Panipenem in plasma and urine was determined and pharmacokinetic analysis was performed using a one-compartment open model. The elimination half-life prolonged and total body clearance, renal clearance (CL(R)) and renal excretion ratio were decreased according to the renal function, i.e. control>glycerol>anti-GBM=gentamicin>nephrectomy=uranium in order. However, distribution volume was consistent in all models. CL(R) showed strong positive correlation with the glomerular filtration rate in spite of a weak correlation with the reciprocal of blood urea nitrogen. However, no obvious correlation was observed with secretory clearance of N-1-methylnicotinamide. This preliminary information based on animal model might be useful for designing pharmacokinetic studies in special population at early stage of new drug development.

Interspecies pharmacokinetic scaling of DA-8159, a new erectogenic, in mice, rats, rabbits and dogs, and prediction of human pharmacokinetics

Time-averaged total body clearance (Cl) and apparent volume of distribution at steady state (V(SS)) of DA-8159 after intravenous administration to mice (30 mg/kg), rats (30 mg/kg), rabbits (30 mg/kg) and dogs (3 mg/kg) were analysed as a function of species body weight (W) using the allometric equation for interspecies scaling, and were used to predict those in humans. Significant linear relationships were obtained between log Cl (l/h) and log W (kg) (r = 0.992; p = 0.0079) and log V(SS) (l) and log W (kg) (r = 0.999; p < 0.0001). The corresponding allometric equations were Cl = 4.36 W(0.492) and V(SS) = 6.41 W(0.911). These allometric equations were extrapolated to predict the Cl and V(SS) for DA-8159 in humans based on the 70 kg body weights. In addition, concentrations in the plasma-time profile predicted using the four animal data fitted to a complex Dedrick plot of animal data. Our results indicated that the DA-8159 data obtained from four laboratory animals could be utilized to generate preliminary estimates of the pharmacokinetic parameters in humans. These parameters can serve as guidelines for better planning of clinical studies.

Interspecies pharmacokinetic scaling of oltipraz in mice, rats, rabbits and dogs, and prediction of human pharmacokinetics

Dose-independent pharmacokinetics of oltipraz after intravenous and/or oral administration at various doses to mice, rats, rabbits and dogs were evaluated. After both intravenous and/or oral administration of oltipraz to mice (5, 10 and 20 mg/kg for intravenous and 15, 30 and 50 mg/kg for oral administration), rats (5, 10 and 20 mg/kg for intravenous and 25, 50 and 100 mg/kg for oral administration), rabbits (5, 10 and 30 mg/kg for intravenous administration) and dogs (5 and 10 mg/kg for intravenous and 50 and 100 mg/kg for oral administration), the total area under the plasma concentration-time curve from time zero to time infinity (AUC) values of oltipraz were dose-proportional in all animals studied. Animal scale-up of some pharmacokinetics parameters of oltipraz was also performed based on the parameters after intravenous administration at a dose of 10 mg/kg to mice, rats, rabbits and dogs. Linear relationships were obtained between log time-averaged total body clearance (Cl) x maximum life-span potential (MLP) (1 year/h) and log species body weight (W) (kg) (r=0.999; p=0.0015), log Cl (l/h) and log W (kg) (r=0.979; p=0.0209), and log apparent volume of distribution at steady state (V(ss)) (l) and log W (kg) (r=0.999; p=0.0009). The corresponding allometric equations were ClxMLP=49.8 W(0.861), Cl=5.20 W(0.523) and V(ss)=4.46 W(0.764). Interspecies scale-up of plasma concentration-time data for the four species using pharmacokinetic time of dienetichron resulted in similar profiles. In addition, concentrations of oltipraz in a plasma concentration-time profile for humans predicted using the four animal data fitted to the dienetichron time transformation of animal data.

The prediction of methylmercury elimination half-life in humans using animal data: a neural network/rough sets analysis

Artificial neural networks and Rough Sets methodology have been utilized to predict human pharmacokinetic elimination half-life data based on animal data training sets. Methylmercury (Hg) pharmacokinetic data was obtained from 37 literature references, which provided data on species, gender, age, weight, route of administration, dose, dose frequency, and elimination half-life based on either whole-body Hg analysis or blood Hg analysis. Data were categorized into various formats for analysis comparisons. Rough Sets methodology was utilized to identify and remove redundant independent variables. Artificial neural networks were used to produce models based on the animal data, which were in turn used to predict and compare to the human elimination half-life values. These neural network predictions were compared to allometric graphical plots of the same data. The best artificial neural network prediction was based on a "thermometer" categorical representation of the data.

Allometric scaling of xenobiotic clearance: uncertainty versus universality

Statistical analysis and Monte Carlo simulation were used to characterize uncertainty in the allometric exponent (b) of xenobiotic clearance (CL). CL values for 115 xenobiotics were from published studies in which at least 3 species were used for the purpose of interspecies comparison of pharmacokinetics. The b value for each xenobiotic was calculated along with its confidence interval (CI). For 24 xenobiotics (21%), there was no correlation between log CL and log body weight. For the other 91 cases, the mean +/- standard deviation of the b values was 0.74 +/- 0.16; range: 0.29 to 1.2. Most (81%) of these individual b values did not differ from either 0.67 or 0.75 at P = 0.05. When CL values for the subset of 91 substances were normalized to a common body weight coefficient (a), the b value for the 460 adjusted CL values was 0.74; the 99% CI was 0.71 to 0.76, which excluded 0.67. Monte Carlo simulation indicated that the wide range of observed b values could have resulted from random variability in CL values determined in a limited number of species, even though the underlying b value was 0.75. From the normalized CL values, four xenobiotic subgroups were examined: those that were (i) protein, and those that were (ii) eliminated mainly by renal excretion, (iii) by metabolism, or (iv) by renal excretion and metabolism combined. All subgroups except (ii) showed a b value not different from 0.75. The b value for the renal excretion subgroup (21 xenobiotics, 105 CL values) was 0.65, which differed from 0.75 but not from 0.67.

Prediction of drug clearance in humans from laboratory animals based on body surface area

The object of the study was to develop a new allometric equation for clearance from laboratory animals to humans based on body surface area (BSA allometric method). Human clearances for 30 drugs were predicted from animal data obtained from the literature. The results predicted with the method were compared with those observed. The results were also compared with values predicted with clearance versus body weight (BW simple allometric method), the product of brain weight and clearance versus body weight (Cl x BRW method) and the product of maximum life span potential and clearance versus body weight (Cl x MLP method), respectively. Good predictions were found in 21 out of 30 with the BAS allometric method. Both BSA allometric method and BW simple allometric method can give good predictions of clearance in humans for many drugs. Similarly to BW simple allometric method, Cl x BRW method and Cl x MLP method, BSA allometric method may be used to accurately predict human clearance from laboratory animal data.

Comparative pharmacokinetics of the carbapenems: clinical implications

During the last few decades, several carbapenems have been developed. The major characteristic of the newer drugs, such as MK-826, is a prolonged half-life. Alternatively, some carbapenems have been developed that can be given orally, such as CS-834 and L-084. Although imipenem and panipenem have to be administered with a co-drug to prevent degradation by the enzyme dehydropeptidase-1 and reduce nephrotoxicity, the newer drugs such as meropenem, biapenem and lenapenem are relatively stable towards that enzyme. Structural modifications have, besides changes in pharmacology, also led to varying antimicrobial properties. For instance, meropenem is relatively more active against Gram-negative organisms than most other carbapenems, but is slightly less active against Gram-positive organisms. Except for half-life and bioavailability, the pharmacokinetic properties of the carbapenems are relatively similar. Distribution is mainly in extracellular body-water, as observed both from the volumes of distribution and from blister studies. Some carbapenems have a better penetration in cerebrospinal fluid than others. In patients with renal dysfunction, doses have to be adjusted, and special care must be taken with imipenem/cilastatin and panipenem/betamipron to prevent accumulation of the co-drugs, as the pharmacokinetic properties of the co-drugs differ from those of the drugs themselves. However, toxicity of the co-drugs has not been shown. The carbapenems differ in proconvulsive activity. Imipenem shows relatively the highest proconvulsive activity, especially at higher concentrations. Pharmacodynamic studies have shown that the major surrogate parameter for antimicrobial efficacy is the percentage of time of the dosage interval above the minimum inhibitory concentration (MIC). The minimum percentage percentage of time above the MIC (TaM) needed for optimal effect is known in animals (30 to 50%), but not in humans. It is probably less than 100%, but may be higher than 50%. Dosage regimens currently in use result in a TaM of about 50% at 4 mg/L, which is the current 'susceptible' breakpoint determined by the National Committee for Clinical Laboratory Standards (NCCLS) for most micro-organisms. Dosage regimens in patients with reduced renal clearance should be based on the TaM. The increased half-life of the newer carbapenems will probably lead to less frequent administration, although continuous infusion may still be the optimal mode of administration for these drugs. The availability of oral carbapenems will have a profound effect on the use of carbapenems in the community.

First time in human for GV196771: interspecies scaling applied on dose selection

The utility of interspecies scaling in early drug development has been extensively debated. The authors discuss the dose selection strategy for a first time into man (FTIM) study for GV196771, a new glycine antagonist, using techniques of interspecies scaling. The FTIM dose selection strategy was based on predicted plasma profiles of GV196771 in humans using allometric scaling and considerations of safety and pharmacological activity in animals. Allometric techniques were first retrospectively applied to data obtained in humans and animals for GV150526, a glycine antagonist with similar pharmacokinetic characteristics to GV196771. GV196771 and GV150526 are extensively protein bound; thus, protein binding differences among species were considered in the scaling. Using the scaled pharmacokinetic parameters, compartmental modeling was performed to prospectively simulate concentration profiles for the oral administration of GV196771. This article will discuss the outcome of the prospective dose selection strategy for GV196771 compared to the actual concentration profiles observed in the FTIM study.

Interspecies scaling of renally secreted drugs

The objective of this study is to predict pharmacokinetic parameters (clearance, volume of distribution at steady state, and elimination half-life) in humans from animal data for drugs which are renally secreted in humans. Pharmacokinetic parameters of ten drugs were scaled-up from animal data obtained from the literature. Using simple allometry (pharmacokinetic parameter of interest vs body weight), total, renal and nonrenal clearances, volume of distribution and half-life were predicted in humans. The predicted parameters were compared with the observed parameters. The results of the study indicated that it is likely that the predicted total and renal clearances from animal data will be underestimated in humans for renally secreted drugs. The prediction of renal clearance was improved by normalizing the renal clearance by a 'correction factor' for animals who exhibited renal secretion. The predicted volume and half-life were comparable with the observed values in man. Overall, the results of this study indicate that caution should be employed in interpreting the total and renal clearance of renally secreted drugs predicted by the allometric approach.

Species variation in pharmacokinetics and opsonization of palmitoyl rhizoxin (RS-1541) incorporated in lipid emulsions

Highly lipophilic antitumor agent, palmitoyl rhizoxin (RS-1541), was incorporated into stable lipid emulsions about 100-1000nm in mean diameter consisting of triglyceride ODO and surfactant HCO-60. The pharmacokinetics of RS-1541 were studied after i.v. injection in mice, rats, rabbits, and dogs. Dog showed characteristic pharmacokinetics of RS-1541, compared with other species. RS-1541 was much more rapidly eliminated from plasma with emulsion particles in dogs than in mice, rats, and rabbits. Most amounts of injected RS-1541 were recovered in the liver six hours after administration to dogs, while less than 20% recoveries were observed for mice and rats. To clarify this species variation, opsonization of emulsion particles were evaluated. When emulsions (about 200nm in size) were opsonized by dog plasma, and intravenously injected to rats, total clearance and liver uptake of RS-1541 were increased to 1.8 fold and 2.7 fold of control values, respectively. In contrasts, emulsions opsonized by mouse, rabbit and human plasma did not show such drastic changes in pharmacokinetics of RS-1541 in rats. Furthermore, total clearance of RS-1541 for emulsions opsonized by dog plasma was increased to 1.9 fold of controls after injection to rabbits. These results indicate that opsonizing activities of dog plasma for RS-1541 emulsions are high, compared with other species. This species variation in opsonizing process probably caused the species variation in the pharmacokinetics of RS-1541 incorporated in lipid emulsions.

Scaling basic toxicokinetic parameters from rat to man

Scaling of the quantified dispositional parameters of xenobiotics from animals to man is of interest from the standpoint of toxicology (e.g., poisoning and risk assessment). Scaling is also important from the standpoint of therapeutics because it represents a strategy for predicting first-use-in-human doses in clinical trials of investigational new drugs. Current strategies for scaling either doses of xenobiotics or the dispositional parameters of xenobiotics from animals to man rely on models that take account principally of species differences in weight or body surface area. Interspecies scaling of dispositional parameters such as clearance or volume of distribution commonly involves the comparison of estimates of these parameters for a given xenobiotic among numerous species on the basis of weight with the resultant mathematical relationship used to predict the values of those parameters for that xenobiotic in a species weighing, on average, about 70 kg (i.e., a man). Our approach has been to ascertain whether a useful mathematical model could be developed for predicting the dispositional parameters of a xenobiotic, its half-life and volume of distribution, in humans based exclusively on estimates of those parameters in rats. Based on a data set of about 100 different xenobiotics, we found that values for half-life and volume of distribution of a xenobiotic in humans can be predicted from the estimates of those parameters in rats.

Recent advances in the chemistry and biology of carbapenem antibiotics

The discovery of the olivanic acids and thienamycin aroused considerable interest amongst medicinal chemists and microbiologists around the world. The susceptibility of these agents to metabolic degradation has, however, been a major obstacle in their development. For many years the only notable success from such intensive research was the combination of imipenem with cilastatin, an inhibitor of the renal dipeptidase enzyme DHP-1. The enormous success of Primaxin for the treatment of a range of life-threatening bacterial infections provided the impetus for the discovery of totally synthetic, non-natural carbapenem derivatives that combine the broad spectrum of antimicrobial activity with stability to enzymatic degradation. This has indeed been realised in the development of meropenem; it possesses the broad spectrum of activity and resistance to beta-lactamases that are embodied in imipenem as well as displaying increased stability to human dehydropeptidases. Most recent research has focused upon the development of carbapenem antibiotics which combine broad spectrum antimicrobial activity and metabolic stability with oral absorption, for the treatment of community-acquired infections. Indeed, the pro-drug esters of the tricyclic carbapenems represent the first significant advance in this respect. However, the increased use of carbapenem antibiotics would undoubtedly accelerate the emergence of carbapenem-hydrolysing enzymes. The ultimate challenge could therefore be the design and synthesis of carbapenem derivatives that are resistant to these metallo-beta-lactamases. Due to the enormous problems encountered in the development of the carbapenem antibiotics, this area of research has, in the past, been described as a battlefield that did not bode well for the future [181]. Primaxin and meropenem proved however that these problems were not insurmountable, and are therefore a testimony to the persistence and dedication of those scientists in their war against bacterial infection.