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The extrapolation of drug exposure between species remains a challenging step in drug development, contributing to the low success rate of drug approval. As a consequence, extrapolation of toxicology from animal models to humans to evaluate safe, first-in-human (FIH) doses requires high safety margins. We hypothesized that a human-CYP3A4-expressing transgenic (Cyp3aXAV) mouse is a more predictive model for human drug exposure of CYP3A4-metabolized small-molecule drugs. Population pharmacokinetic models based on wild-type (WT) and Cyp3aXAV mouse pharmacokinetic data of oral lorlatinib, brigatinib, ribociclib and fisogatinib were allometrically scaled and compared to human exposure. Extrapolation of the Cyp3aXAV mouse model closely predicted the observed human exposure for lorlatinib and brigatinib with a 1.1-fold and 1.0-fold difference, respectively, compared to a 2.1-fold and 1.9-fold deviation for WT-based extrapolations of lorlatinib and brigatinib, respectively. For ribociclib, the extrapolated WT mouse model gave better predictions with a 1.0-fold deviation compared to a 0.3-fold deviation for the extrapolated Cyp3aXAV mouse model. Due to the lack of a human population pharmacokinetic model for fisogatinib, only median maximum concentration ratios were calculated, resulting in ratios of 1.0 and 0.6 for WT and Cyp3aXAV mice extrapolations, respectively. The more accurate predictions of human exposure in preclinical research based on the Cyp3aXAV mouse model can ultimately result in FIH doses associated with improved safety and efficacy and in higher success rates in drug development.

Amphotericin B is an antifungal and antiparasitic drug used in first-line treatment of the parasitic neglected tropical disease leishmaniasis. Liposomal amphotericin B is currently studied for the treatment of cutaneous and post-kala-azar dermal leishmaniasis, where the dermis of the skin is infected with Leishmania parasites. For the optimization of known treatment regimens, accurate target-site concentrations of the drug are required. To date, no assay was available to assess human skin concentrations of amphotericin B. We here present a bioanalytical assay for the quantification of amphotericin B in 4-mm human skin biopsies. Human skin biopsies were homogenized by overnight digestion using collagenase A and were processed afterwards by simple protein precipitation using methanol. Separation and detection were achieved using a Gemini C18 column with slightly acidic chromatographic conditions and a quadrupole - linear ion trap mass spectrometer, respectively. The method was validated in digestion solution over a range of 10-2,000 ng/mL using natamycin as internal standard, with a correlation coefficient (r2) of at least 0.9974. The assay performance, accuracy and precision, were acceptable over the validated range, using international (EMA and FDA) acceptance criteria. In the skin tissue extracts, amphotericin B ion enhancement was observed, however, the internal standard (IS) corrected for this effect hence calibration standards in digestion solvent could be used as a surrogate matrix for the quantification in skin tissue. Sample preparation recoveries were low (around 27%) because of degradation of amphotericin B during digestion and sample preparation processes, albeit highly reproducible, without compromising the accuracy and precision of the method. Using this assay, amphotericin B could be detected and quantified in skin biopsies originating from treated Indian post-kala-azar dermal leishmaniasis patients.

Bioanalytical assay development and validation procedures were performed to quantify antiprotozoal drug paromomycin in human skin tissue by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. Paromomycin, an aminoglycoside drug, is administered intra-muscularly and used in the treatment of multiple clinical presentations of the neglected tropical disease leishmaniasis. It is currently studied in the treatment of post-kala-azar dermal leishmaniasis, a disease where the Leishmania parasites divide and reside in the skin. We present a target-site bioanalytical method to accurately quantify paromomycin in human skin tissue, with the clinical purpose of quantifying paromomycin in skin biopsies from post-kala-azar dermal leishmaniasis patients originating from Sudan. Enzymatic digestion using collagenase A incubated at 37 °C overnight was employed as homogenization method to produce skin tissue homogenates. Further sample preparation was performed by protein precipitation using trichloroacetic acid and a dilution step. Final extracts were injected onto a C18 analytical column and isocratic heptafluorobutyric acid ion-pair separation and elution were employed. The chromatography system was coupled to a triple quadrupole mass spectrometer for detection. The method was validated in digestion solution over a linear range from 5 to 1000 ng/mL (r2 ≥ 0.9967) with the assay performance of accuracy and precision within acceptable criteria values as stated by the EMA guidelines. Furthermore, matrix effects were observed in human skin tissue and were corrected by the multiple deuterated paromomycin internal standard. No substantial IS-normalized matrix effect was detected along with relatively high sample preparation recovery. Consequently, digestion solution matrix serving as the preparation of calibration standards can be used as surrogate matrix for human skin tissue, which is convenient given the limited availability of control matrix. Finally, paro

Miltefosine is the only oral drug approved for the treatment of various clinical presentations of the neglected parasitic disease leishmaniasis. In cutaneous leishmaniasis and post-kala-azar dermal leishmaniasis, Leishmania parasites reside and multiply in the dermis of the skin. As miltefosine is orally administered and this drug is currently studied for the treatment of these skin-related types of leishmaniasis, there is an urgent need for an accurate assay to determine actual miltefosine levels in human skin tissue to further optimize treatment regimens through target-site pharmacokinetic studies. We describe here the development and validation of a sensitive method to quantify miltefosine in 4-mm human skin biopsies utilizing high-performance liquid chromatography coupled to tandem mass spectrometry. After the skin tissues were homogenized overnight by enzymatic digestion using collagenase A, the skin homogenates were further processed by protein precipitation and phenyl-bonded solid phase extraction. Final extracts were injected onto a Gemini C18 column using alkaline eluent for separation and elution. Detection was performed by positive ion electrospray ionization followed by a quadrupole - linear ion trap mass spectrometer, using deuterated miltefosine as an internal standard. The method was validated over a linear calibration range of 4-1000 ng/mL (r2 ≥ 0.9996) using miltefosine spiked digestion solution for calibration and quality control samples. Validation parameters were all within internationally accepted criteria, including intra- and inter-assay accuracies and precisions within± 15% and ≤ 15% (within± 20% and ≤ 20% at the lower limit of quantitation). There was no significant matrix effect of the human skin tissue matrix and the recovery for miltefosine, and internal standard were comparable. Miltefosine in human skin tissue homogenates was stable during the homogenization incubation (37 °C,± 16 h) and after a minimum of 10 days of storage at - 20 °C

The effect of transporters and enzymes on drug pharmacokinetics is increasingly evaluated using genetically modified animals that have these proteins either knocked-out or their human orthologues transgenically expressed. Analysis of pharmacokinetic data obtained in such experiments is typically performed using non-compartmental analysis (NCA), which has limitations such as not being able to identify the PK parameter that is affected by the genetic modification of the enzymes or transporters and the requirement of intense and homogeneous sampling of all subjects. Here we used a compartmental population pharmacokinetic modeling approach using PK data from a series of genetically modified mouse experiments with lorlatinib to extend the results and conclusions from previously reported NCA analyses. A compartmental population pharmacokinetic model was built and physiologically plausible covariates were evaluated for the different mouse strains. With the model, similar effects of the strains on the area under the concentration-time curve (AUC) from 0 to 8 hours were found as for the NCA. Additionally, the differences in AUC between the strains were explained by specific effects on clearance and bioavailability for the strain with human expressing CYP3A4. Finally, effects of multidrug efflux transporters ATP-binding cassette (ABC) sub-family B member 1 (ABCB1) and G member 2 (ABCG2) on brain efflux were quantified. Use of compartmental population PK modeling yielded additional insight into the role of drug-metabolizing enzymes and drug transporters in mouse experiments compared to the NCA. Furthermore, these models allowed analysis of heterogeneous pooled datasets and the sparse organ concentration data in contrast to classical NCA analyses.

Miltefosine is an alkylphosphocholine agent with a broad spectrum of antiparasitic properties. For over two decades, miltefosine has remained the only oral drug licensed and used in the treatment of the neglected tropical disease, leishmaniasis. The last extensive review of the pharmacology of miltefosine was published in 2012. Additional data on the clinical pharmacokinetics (PK) and pharmacodynamics (PD) of miltefosine have become available in the last decade, and there are ongoing and future studies in this area. Miltefosine PK are characterized by slow absorption and elimination, resulting in accumulation of drug in plasma until the end of treatment. Several recent studies established exposure-response relationships for various regimens of miltefosine in the treatment of visceral and cutaneous leishmaniasis, leading to the identification of PK parameters predictive of clinical relapse and outcome. This review provides an update on the most recent developments in the area of clinical pharmacology of miltefosine, including a discussion of the current dosing regimens.

BACKGROUND: Most patients with cancer treated with everolimus experience stomatitis, which seriously affects the quality of life. The salivary concentrations of everolimus may predict the incidence and severity of stomatitis. The authors aimed to examine whether it was feasible to quantify the everolimus concentration in saliva and subsequently use it to predict stomatitis. METHODS: Saliva and whole blood samples were taken from patients with cancer, who were treated with everolimus in the dosage of either 10 mg once a day or 5 mg twice a day. Everolimus concentrations in saliva samples were measured by liquid chromatography-tandem mass spectrometry. A published population pharmacokinetic model was extended with the everolimus concentration in saliva to assess any association between everolimus in the blood and saliva. Subsequently, the association between the occurrence of stomatitis and the everolimus concentration in saliva was studied. RESULTS: Eleven patients were included in this study; saliva samples were available from 10 patients, including 3 patients with low-grade stomatitis. Everolimus concentrations were more than 100-fold lower in saliva than in whole blood (accumulation ratio 0.00801 and relative standard error 32.5%). Interindividual variability (67.7%) and residual unexplained variability (84.0%) were high. The salivary concentration of everolimus tended to be higher in patients with stomatitis, 1 hour postdose ( P = 0.14). CONCLUSIONS: Quantification of the everolimus concentration in saliva was feasible and revealed a nonsignificant correlation between everolimus concentration in the saliva and the occurrence of stomatitis. If future research proves this relationship to be significant, the everolimus concentration in the saliva may be used as an early predictor of stomatitis without invasive sampling. Thereby, in patients with high salivary everolimus concentrations, precautions can be taken to decrease the incidence and severity of stomatitis.

Correlations between increasing concentrations of circulating tumor DNA (ctDNA) in plasma and disease progression have been shown. A nonlinear mixed effects model to describe the dynamics of epidermal growth factor receptor (EGFR) ctDNA data from patients with non-small cell lung cancer (NSCLC) combined with a parametric survival model were developed to evaluate the ability of these modeling techniques to describe ctDNA data. Repeated ctDNA measurements on L858R, exon19del, and T790M mutants were available from 54 patients with EGFR mutated NSCLC treated with erlotinib or gefitinib. Different dynamic models were tested to describe the longitudinal ctDNA concentrations of the driver and resistance mutations. Subsequently, a parametric time-to-event model for progression-free survival (PFS) was developed. Predicted L858R, exon19del, and T790M concentrations were used to evaluate their value as predictor for disease progression. The ctDNA dynamics were best described by a model consisting of a zero-order increase and first-order elimination (19.7/day, 95% confidence interval [CI] 14.9-23.6/day) of ctDNA concentrations. In addition, time-dependent development of resistance (5.0 × 10-4 , 95% CI 2.0 × 10-4 -7.0 × 10-4 /day) was included in the final model. Relative change in L858R and exon19del concentrations from baseline was identified as most significant predictor of disease progression (p = 0.001). The dynamic model for L858R, exon19del, and T790M concentrations in ctDNA and time-to-event model adequately described the observed concentrations and PFS data in our clinical cohort. In addition, it was shown that nonlinear mixed effects modeling is a valuable method for the analysis of longitudinal and heterogeneous biomarker datasets obtained from clinical practice.

BACKGROUND: This study aimed to determine whether paromomycin plus miltefosine (PM/MF) is noninferior to sodium stibogluconate plus paromomycin (SSG/PM) for treatment of primary visceral leishmaniasis in eastern Africa. METHODS: An open-label, phase 3, randomized, controlled trial was conducted in adult and pediatric patients at 7 sites in eastern Africa. Patients were randomly assigned to either 20 mg/kg paromomycin plus allometric dose of miltefosine (14 days), or 20 mg/kg sodium stibogluconate plus 15 mg/kg paromomycin (17 days). The primary endpoint was definitive cure after 6 months. RESULTS: Of 439 randomized patients, 424 completed the trial. Definitive cure at 6 months was 91.2% (155 of 170) and 91.8% (156 of 170) in the PM/MF and SSG/PM arms in primary efficacy modified intention-to-treat analysis (difference, 0.6%; 97.5% confidence interval [CI], -6.2 to 7.4), narrowly missing the noninferiority margin of 7%. In the per-protocol analysis, efficacy was 92% (149 of 162) and 91.7% (155 of 169) in the PM/MF and SSG/PM arms (difference, -0.3%; 97.5% CI, -7.0 to 6.5), demonstrating noninferiority. Treatments were well tolerated. Four of 18 serious adverse events were study drug-related, and 1 death was SSG-related. Allometric dosing ensured similar MF exposure in children (<12 years) and adults. CONCLUSIONS: PM/MF and SSG/PM efficacies were similar, and adverse drug reactions were as expected given the drugs safety profiles. With 1 less injection each day, reduced treatment duration, and no risk of SSG-associated life-threatening cardiotoxicity, PM/MF is a more patient-friendly alternative for children and adults with primary visceral leishmaniasis in eastern Africa. Clinical Trials Registration. NCT03129646.

Little is known about infant's safety of chemotherapy during breastfeeding where evidence is limited to a few case reports. This lack of knowledge has led to a general tendency to advise against breastfeeding during cytotoxic therapy despite the overwhelming benefits that breastfeeding offers to both the mothers and their children. In this case series, the presence of five chemotherapies in breast milk was determined. The aim was to obtain insight into the presence of these drugs in breast milk to inform and help clinicians in making informed decisions for women who want to breastfeed. Three patients collected 24-hour samples of breast milk every day for 1, 2, or 3 weeks after chemotherapy, 210 in total. After determination of drug concentrations, the infant daily dose, relative daily infant dose (RID%) and cumulative RID were calculated. Cumulative RIDs in patients varied from 10% to values lower than 1%. Rich data allowed us to design a table which gives predictions on the amount of days that breast milk has to be discarded to reach cumulative RIDs below 5, 1, and 0.1% for each compound. For cyclophosphamide, paclitaxel, and carboplatin, cumulative RIDs below 1 or 0.1% are reached if breast milk is discarded for 1-3 days after administration. This might suggest that breastfeeding in between cycles is an option. However, other pharmacological parameters should also be taken into consideration. For doxorubicin, also the levels of the active metabolite doxorubicinol need quantification. Similarly, breastfeeding during treatment with cisplatin might give substantial exposure and we advise caution.

BACKGROUND: Physiologically based pharmacokinetic (PBPK) models combine drug-specific information with prior knowledge on the physiology and biology at the organism level. Whole-body PBPK models contain an explicit representation of the organs and tissue and are a tool to predict pharmacokinetic behavior of drugs. The aim of this study was to develop a PBPK model to describe organ distribution of 68Ga-DOTATATE in a population of patients without detectable neuroendocrine tumors (NETs). METHODS: Clinical 68Ga-DOTATATE PET/CT data from 41 patients without any detectable somatostatin receptor (SSTR) overexpressing tumors were included. Scans were performed at 45 min (range 30-60 min) after intravenous bolus injection of 68Ga-DOTATATE. Organ (spleen, liver, thyroid) and blood activity levels were derived from PET scans, and corresponding DOTATATE concentrations were calculated. A whole-body PBPK model was developed, including an internalization reaction, receptor recycling, enzymatic reaction for intracellular degradation and renal clearance. SSTR2 expression was added for several organs. Input parameters were fixed or estimated using a built-in Monte Carlo algorithm for parameter identification. RESULTS: 68Ga-DOTATATE was administered with a median peptide amount of 12.3 µg (range 8.05-16.9 µg) labeled with 92.7 MBq (range 43.4-129.9 MBq). SSTR2 amounts for spleen, liver and thyroid were estimated at 4.40, 7.80 and 0.0108 nmol, respectively. Variability in observed organ concentrations was best described by variability in SSTR2 expression and differences in administered peptide amounts. CONCLUSIONS: To conclude, biodistribution of 68Ga-DOTATATE was described with a whole-body PBPK model, where tissue distribution was mainly determined by variability in SSTR2 organ expression and differences in administered peptide amounts.

BACKGROUND: Based on reassuring short-term foetal and maternal safety data, there is an increasing trend to administer chemotherapy during the second and third trimesters of pregnancy. The pharmacokinetics (PK) of drugs might change as a result of several physiological changes that occur during pregnancy, potentially affecting the efficacy and safety of chemotherapy. OBJECTIVE: With this analysis, we aimed to quantitatively describe the changes in the PK of docetaxel, paclitaxel, doxorubicin and epirubicin in pregnant women compared with non-pregnant women. METHODS: PK data from 9, 20, 22 and 16 pregnant cancer patients from the International Network of Cancer, Infertility and Pregnancy (INCIP) were available for docetaxel, paclitaxel, doxorubicin and epirubicin, respectively. These samples were combined with available PK data from non-pregnant patients. Empirical non-linear mixed-effects models were developed, evaluating fixed pregnancy effects and gestational age as covariates. RESULTS: Overall, 82, 189, 271, and 227 plasma samples were collected from pregnant patients treated with docetaxel, paclitaxel, doxorubicin and epirubicin, respectively. The plasma PK data were adequately described by the respective models for all cytotoxic drugs. Typical increases in central and peripheral volumes of distribution of pregnant women were identified for docetaxel, paclitaxel, doxorubicin and epirubicin. Additionally, docetaxel, doxorubicin and paclitaxel clearance were increased in pregnant patients, resulting in lower exposure in pregnant women compared with non-pregnant patients. CONCLUSION: Given the interpatient variability, the identified pregnancy-induced changes in PK do not directly warrant dose adjustments for the studied drugs. Nevertheless, these results underscore the need to investigate the efficacy of chemotherapy, when administered during pregnancy.

Capecitabine is an oral pro-drug of 5-fluorouracil. Patients with solid tumours who are treated with capecitabine may develop hand-and-foot syndrome (HFS) as side effect. This might be a result of accumulation of intracellular metabolites. We characterised the pharmacokinetics (PK) of 5-fluorouridine 5'-triphosphate (FUTP) in peripheral blood mononuclear cells (PBMCs) and assessed the relationship between exposure to capecitabine or its metabolites and the development of HFS. Plasma and intracellular capecitabine PK data and ordered categorical HFS data was available. A previously developed model describing the PK of capecitabine and metabolites was extended to describe the intracellular FUTP concentrations. Subsequently, a continuous-time Markov model was developed to describe the development of HFS during treatment with capecitabine. The influences of capecitabine and metabolite concentrations on the development of HFS were evaluated. The PK of intracellular FUTP was described by an one-compartment model with first-order elimination (ke,FUTP was 0.028 h-1 (95% confidence interval 0.022-0.039)) where the FUTP influx rate was proportional to the 5-FU plasma concentrations. The predicted individual intracellular FUTP concentration was identified as a significant predictor for the development and severity of HFS. Simulations demonstrated a clear exposure-response relationship. The intracellular FUTP concentrations were successfully described and a significant relationship between these intracellular concentrations and the development and severity of HFS was identified. This model can be used to simulate future dosing regimens and thereby optimise treatment with capecitabine.

Pemetrexed is an important component of first line treatment in patients with non-squamous non-small cell lung cancer. However, a limitation is the contraindication in patients with renal impairment due to hematological toxicity. Currently, it is unknown how to safely dose pemetrexed in these patients. The aim of our study was to elucidate the relationship between pemetrexed exposure and toxicity to support the development of a safe dosing regimen in patients with renal impairment. A population pharmacokinetic/pharmacodynamic analysis was performed based on phase II study results in three patients with renal dysfunction, supplemented with data from 106 patients in early clinical studies. Findings were externally validated with data of different pemetrexed dosing regimens. Alternative dosing regimens were evaluated using the developed model. We found that pemetrexed toxicity was driven by the time above a toxicity threshold concentration. The threshold for vitamin-supplemented patients was 0.110 mg/mL (95% CI: 0.092-0.146 mg/mL). It was observed that in patients with renal impairment (estimated glomerular filtration rate [eGFR]: <45 mL/min) the approved dose of 500 mg/m2 would yield a high probability of severe neutropenia in the range of 51.0% to 92.6%. A pemetrexed dose of 20 mg for patients (eGFR: 20 mL/min) is shown to be neutropenic-equivalent to the approved dose in patients with adequate renal function (eGFR: 90 mL/min), but would result in an approximately 13-fold lower area under the concentration-time curve. The pemetrexed exposure-toxicity relationship is explained by a toxicity threshold and substantially different from previously thought. Without prophylaxis for toxicity, it is unlikely that a therapeutic dose can be safely administered to patients with renal impairment.