Intraperitoneal pharmacokinetics of systemic oxaliplatin, 5-fluorouracil and bevacizumab in patients with colorectal peritoneal metastases.

BACKGROUND: Peritoneal metastases (PM) commonly occur in colorectal cancer patients. Systemic chemotherapy yields poor outcomes for these patients. It is hypothesised that traditional systemic chemotherapy is not very effective for this patient population. This study investigates to what extent systemic anti-cancer therapy crosses the peritoneal barrier. METHODS: In a Phase I study, eighteen patients received systemic oxaliplatin, 5-FU, and bevacizumab. Plasma and peritoneal fluid samples were collected to measure drug concentrations. A non-compartmental analysis determined the Area Under the Curve (AUC) for oxaliplatin and 5-FU in both matrices. Intraperitoneal (IP) and intravenous (IV) exposure ratios were calculated, along with the bevacizumab concentration IP/IV ratio. The relationship between tumour load and IP/IV ratios and the correlation between the IP/IV ratios of different treatments were assessed statistically. RESULTS: A total of 438 5-FU samples and 578 oxaliplatin samples were analysed in plasma and peritoneal fluid. Bevacizumab was quantified with 17 measurements in plasma and 15 measurements IP. Median IP/IV ratios were 0.143, 0.352 and 0.085 for 5-FU, oxaliplatin and bevacizumab, respectively. Oxaliplatin exhibited a longer IP half-life than 5-FU. A correlation was found between oxaliplatin and bevacizumab IP/IV ratios (R=0.69, p=0.01). No statistical correlations were found between the other investigated drugs. CONCLUSIONS: Our findings indicate that only a small percentage of systemically administered anti-cancer treatment reaches the IP cavity, questioning their efficacy against PM. This strengthens the hypothesis for repeated intraperitoneal chemotherapy to reach adequate anti-cancer drug levels.

Clinical Utility of Circulating Tumor DNA in Patients With Advanced KRASG12C-Mutated NSCLC Treated With Sotorasib.

INTRODUCTION: For patients with KRASG12C-mutated NSCLC who are treated with sotorasib, there is a lack of biomarkers to guide treatment decisions. We therefore investigated the clinical utility of pretreatment and on-treatment circulating tumor DNA (ctDNA) and treatment-emergent alterations on disease progression. METHODS: Patients with KRASG12C-mutated NSCLC treated with sotorasib were prospectively enrolled in our biomarker study (NCT05221372). Plasma samples were collected before sotorasib treatment, at first-response evaluation and at disease progression. The TruSight Oncology 500 panel was used for ctDNA and variant allele frequency analysis. Tumor response and progression-free survival were assessed per Response Evaluation Criteria in Solid Tumors version 1.1. RESULTS: Pretreatment KRASG12C ctDNA was detected in 50 of 66 patients (76%). Patients with detectable KRASG12C had inferior progression-free survival (hazard ratio [HR] 2.13 [95% confidence interval [CI]: 1.06-4.30], p = 0.031) and overall survival (HR 2.61 [95% CI: 1.16-5.91], p = 0.017). At first-response evaluation (n = 40), 29 patients (73%) had a molecular response. Molecular nonresponders had inferior overall survival (HR 3.58 [95% CI: 1.65-7.74], p = 0.00059). The disease control rate was significantly higher in those with a molecular response (97% versus 64%, p = 0.015). KRAS amplifications were identified as recurrent treatment-emergent alterations. CONCLUSIONS: Our data suggest detectable pretreatment KRASG12C ctDNA as a marker for poor prognosis and on-treatment ctDNA clearance as a marker for treatment response. We identified KRAS amplifications as a potential recurring resistance mechanism to sotorasib. Identifying patients with superior prognosis could aid in optimizing time of treatment initiation, and identifying patients at risk of early progression could allow for earlier treatment decisions.

Darolutamide does not interfere with OATP-mediated uptake of docetaxel.

The addition of darolutamide, an androgen receptor signalling inhibitor, to therapy with docetaxel has recently been approved as a strategy to treat metastatic prostate cancer. OATP1B3 is an SLC transporter that is highly expressed in prostate cancer and is responsible for the accumulation of substrates, including docetaxel, into tumours. Given that darolutamide inhibits OATP1B3 in vitro, we sought to characterise the impact of darolutamide on docetaxel pharmacokinetics. We investigated the influence of darolutamide on OATP1B3 transport using in vitro and in vivo models. We assessed the impact of darolutamide on the tumour accumulation of docetaxel in a patient-derived xenograft (PDX) model and on an OATP1B biomarker in patients. Darolutamide inhibited OATP1B3 in vitro at concentrations higher than the reported Cmax. Consistent with these findings, in vivo studies revealed that darolutamide does not influence the pharmacokinetics of Oatp1b substrates, including docetaxel. Docetaxel accumulation in PDX tumours was not decreased in the presence of darolutamide. Metastatic prostate cancer patients had similar levels of OATP1B biomarkers, regardless of treatment with darolutamide. Consistent with a low potential to inhibit OATP1B3-mediated transport in vitro, darolutamide does not significantly impede the transport of Oatp1b substrates in vivo or in patients. Our findings support combined treatment with docetaxel and darolutamide, as no OATP1B3 transporter based drug-drug interaction was identified.

Hepatotoxicity in patients with non-small cell lung cancer treated with sotorasib after prior immunotherapy: a comprehensive clinical and pharmacokinetic analysis.

BACKGROUND: Sotorasib given after immunotherapy could put patients at increased risk of hepatotoxicity. Therefore, there is a need to gain insight into the potential correlation between anti-PD-(L)1 treatment, anti-PD-(L)1 concentrations, sotorasib concentrations, and the incidence of hepatotoxicity during sotorasib. METHODS: Patients with KRASG12C-mutated NSCLC treated with sotorasib were prospectively enrolled in our biomarker cohort study (NCT05221372). Plasma samples were collected prior and during sotorasib treatment for anti-PD-1 and sotorasib concentrations. ALT/AST/ALP/GGT increases were collected prospectively and graded according to CTCAEv5.0. Severe hepatotoxicity was defined as grade ≥3 ALT/AST/ALP/GGT increase. FINDINGS: Of the 91 included patients, 80 (88%) received prior anti-PD-(L)1. Prior anti-PD-(L)1 and prior immune-related hepatotoxicity were associated with a higher incidence of severe hepatotoxicity (35% versus 0%, p = 0.016 and 75% versus 31%, p = 0.019, respectively). Patients with an interval of ≤6 weeks between anti-PD-(L)1 and sotorasib (n = 18) had a significantly higher incidence of severe hepatotoxicity than those with a 6-12 week (n = 24) and ≥12 week (n = 38) interval (83% versus 33% versus 13%, respectively, p < 0.0001). Sotorasib trough concentrations did not differ significantly between those with or without severe hepatotoxicity (106 versus 126 ng/mL, p = 0.16). Pembrolizumab concentrations were higher in those with severe hepatotoxicity versus those without (25.6 versus 6.1 µg/mL, p < 0.0001). INTERPRETATION: In this preliminary prospective study, sotorasib after PD-(L)1 blockade was associated with severe hepatotoxicity, especially in patients with a short interval between treatments, prior immune-related hepatitis and higher anti-PD-1 plasma concentrations. Our results suggest a minimum interval of 6 weeks between anti-PD-(L)1 and sotorasib to minimize the risk of hepatotoxicity. FUNDING: None.

Quantification and clinical validation of the selective MET kinase inhibitor DO-2 and its metabolites DO-5 and M3 in human plasma.

DO-2 is a highly selective MNNG HOS transforming (MET) inhibitor. This deuterated drug is thought to diminish the formation of the Aldehyde Oxidase 1 inactive metabolite M3. For various reasons, quantification of DO-2 and its metabolites M3 and DO-5 is highly relevant. In this study, we present an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method to quantify DO-2, M3 and DO-5. Rolipram served as the internal standard. Aliquots of 25 µL were mixed with 100 µL internal standard consisting of 10 ng/mL rolipram in acetonitrile. Separation of the analytes was achieved on an Acquity UPLC ® HSS T3 column, utilizing gradient elution with water/formic acid and acetonitrile/formic acid at a flow-rate of 0.400 mL/min. Calibration curves were linear in the range of 1.00 - 1000 ng/mL for DO-2 and DO-5, and 2.00 - 2000 ng/mL for M3 in human plasma. The within-run and between-run precisions of DO-2, DO-5 and M3, also at the level of the LLQ, were within 12.1%, while the accuracy ranged from 89.5 to 108.7%. All values for accuracy, within-run and between-run precisions met the criteria set by the Food and Drug Administration. The method was effectively employed in the analysis of samples obtained from a clinical trial.

Influence of Food With Different Fat Concentrations on Alectinib Exposure: A Randomized Crossover Pharmacokinetic Trial.

BACKGROUND: Alectinib is the keystone treatment in advanced anaplastic lymphoma kinase-positive (ALK+) non-small cell lung cancer (NSCLC). An exposure-response threshold of 435 ng/mL has recently been established, albeit 37% of patients do not reach this threshold. Alectinib is orally administered, and absorption is largely influenced by food. Hence, further investigation into this relationship is needed to optimize its bioavailability. PATIENTS AND METHODS: In this randomized 3-period crossover clinical study in ALK+ NSCLC, alectinib exposure was compared among patients with different diets. Every 7 days, the first alectinib dose was taken with either a continental breakfast, 250-g of low-fat yogurt, or a self-chosen lunch, and the second dose was taken with a self-chosen dinner. Sampling for alectinib exposure (Ctrough) was performed at day 8, just prior to alectinib intake, and the relative difference in Ctrough was compared. RESULTS: In 20 evaluable patients, the mean Ctrough was 14% (95% CI, -23% to -5%; P=.009) and 20% (95% CI, -25% to -14%; P<.001) lower when taken with low-fat yogurt compared with a continental breakfast and a self-chosen lunch, respectively. Administration with a self-chosen lunch did not change exposure compared with a continental breakfast (+7%; 95% CI, -2% to +17%; P=.243). In the low-fat yogurt period, 35% of patients did not reach the threshold versus 5% with the other meals (P<.01). CONCLUSIONS: Patients and physicians should be warned for a detrimental food-drug interaction when alectinib is taken with low-fat yogurt, because it results in a clinically relevant lower alectinib exposure. Intake with a self-chosen lunch did not change drug exposure and could be a safe and patient-friendly alternative.

CYP3A4*22 Genotype-Guided Dosing of Kinase Inhibitors in Cancer Patients.

INTRODUCTION: A genetic variant explaining a part of the exposure of many kinase inhibitors (KIs) is the single nucleotide polymorphism (SNP) CYP3A4*22, resulting in less CYP3A4 enzyme activity. The primary aim of this study was to investigate if the systemic exposure is non-inferior after a dose reduction of KIs metabolized by CYP3A4 in CYP3A4*22 carriers compared to patients without this SNP (i.e., wildtype patients) receiving the standard dose. METHODS: In this multicenter, prospective, non-inferiority study, patients were screened for the presence of CYP3A4*22. Patients with the CYP3A4*22 SNP received a 20-33% dose reduction. At steady state, a pharmacokinetic (PK) analysis was performed and compared to the PK results from wildtype patients treated with the registered dose using a two-stage individual patient data meta-analysis approach. RESULTS: In total, 207 patients were included in the final analysis. The CYP3A4*22 SNP was found in 16% of the patients in the final analysis (n = 34). Most of the included patients received imatinib (37%) or pazopanib (22%) treatment. The overall geometric mean ratio (GMR) comparing the exposure of the CYP3A4*22 carriers to the exposure of the wildtype CYP3A4 patients was 0.89 (90% confidence interval: 0.77-1.03). CONCLUSION: Non-inferiority could not be proven for dose reduction of KIs metabolized by CYP3A4 in CYP3A4*22 carriers compared to the registered dose in wildtype patients. Therefore, an up-front dose reduction based upon the CYP3A4*22 SNP for all KIs does not seem an eligible new way of personalized therapy. TRIAL REGISTRATION: International Clinical Trials Registry Platform Search Portal; number NL7514; registered 11/02/2019.

Validation of an LC-MS/MS method for simultaneous quantification of abiraterone, enzalutamide and darolutamide in human plasma.

Currently, several oral androgen receptor signalling inhibitors are available for the treatment of advanced prostate cancer. Quantification of plasma concentrations of these drugs is highly relevant for various purposes, such as Therapeutic Drug Monitoring (TDM) in oncology. Here, we report a liquid chromatography/tandem mass spectrometric (LC-MS/MS) method for the simultaneous quantification of abiraterone, enzalutamide, and darolutamide. The validation was performed according to the requirements of the U.S. Food and Drug Administration and European Medicine Agency. We also demonstrate the clinical applicability of the quantification of enzalutamide and darolutamide in patients with metastatic castration-resistant prostate cancer.

In Vivo Efficacy Testing of Peptide Receptor Radionuclide Therapy Radiosensitization Using Olaparib.

Peptide receptor radionuclide therapy (PRRT), a form of internal targeted radiation treatment using [177Lu]Lu [DOTA0-Tyr3]octreotate, is used to treat patients with metastasized neuroendocrine tumors (NETs). Even though PRRT is now the second line of treatment for patients with metastasized NETs, the majority of patients will not be cured by the treatment. PRRT functions by inducing DNA damage upon radioactive decay and inhibition of DNA damage repair proteins could therefore be used as a strategy to potentiate PRRT. Previous work has shown promising results on the combination of PRRT with the PARP inhibitor olaparib in cell lines and mice and we have been taken the next step for further in vivo validation using two different xenografted mouse models. We observed that this combination therapy resulted in increased therapeutic efficacy only in one model and not the other. Overall, our findings indicate a tumor-type dependent anti-tumor response to the combination of PRRT and olaparib. These data emphasize the unmet need for the molecular stratification of tumors to predetermine the potential clinical value of combining PARP inhibition with PRRT.

Quantitation of osimertinib, alectinib and lorlatinib in human cerebrospinal fluid by UPLC-MS/MS.

Overall survival in metastatic lung cancer has been dramatically improved with the use of small molecule kinase inhibitors (SMKIs). Quantification of SMKI in cerebrospinal fluid (CSF) can be used to assess penetration of these drugs into the central nervous system. This paper describes an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for quantification of the SMKIs alectinib, lorlatinib and osimertinib in human CSF. Alectinib-d8 and dasatinib-d8 were used as internal standards. Aliquots with 25 µL CSF/30% albumin (9:1,v/v) were mixed with 100 µL internal standard solution consisting of 1 ng/mL dasatinib-d8 and alectinib-d8 in acetonitrile. The analytes were separated by an Acquity UPLC® HSS T3 column (2.1 ×150 mm, 1.8 µm), using gradient elution (ammonium formate pH 4.5, acetonitrile) with a flow rate of 0.400 mL/min. All calibration curves were linear for the concentration range from 2.50 to 250 ng/mL. Within-run and between-run precision varied from 0.72% to 11.7%, with accuracy ranging from 95.3% to 113.2%. For all compounds, a high degree of non-specific binding to the vacutainer was observed. This issue could be countered easily by a combination of pre-coating with BSA solution (30%) in phosphate buffer pH 4.2, and immediate sample mixture with BSA solution after collection. To test the clinical applicability, CSF was collected in seven unique patients using alectinib (n = 1), lorlatinib (n = 2), and osimertinib (n = 4). Measured CSF trough concentrations ranged between 3.37 and 116 ng/mL.

Quantitative and qualitative changes in platelet traits of sunitinib-treated patients with renal cell carcinoma in relation to circulating sunitinib levels: a proof-of-concept study.

BACKGROUND: Tyrosine kinase inhibitors (TKIs), such as sunitinib, are used for cancer treatment, but may also affect platelet count and function with possible hemostatic consequences. Here, we investigated whether patient treatment with the TKI sunitinib affected quantitative and qualitative platelet traits as a function of the sunitinib level and the occurrence of bleeding. METHODS: Blood was collected from 20 metastatic renal cell carcinoma (mRCC) patients before treatment, and at 2 weeks, 4 weeks and 3 months after sunitinib administration. We measured blood cell counts, platelet aggregation, and concentrations of sunitinib as well as its N-desethyl metabolite in plasma, serum and isolated platelets. Progression of disease (PD) and bleeding were monitored after 3 months. RESULTS: In sunitinib-treated mRCC patients, concentrations of (N-desethyl-)sunitinib in plasma and serum were highly correlated. In the patients' platelets the active metabolite levels were relatively increased as compared to sunitinib. On average, a sustained reduction in platelet count was observed on-treatment, which was significantly related to the inhibitor levels in plasma/serum. Principal component and correlational analysis showed that the (N-desethyl-)sunitinib levels in plasma/serum were linked to a reduction in both platelet count and collagen-induced platelet aggregation. The reduced aggregation associated in part with reported bleeding, but did not correlate to PD. CONCLUSION: The sunitinib-induced reduction in quantitative and qualitative platelet traits may reflect the effective sunitinib levels in the patient. These novel results may serve as a proof-of-principle for other TKI-related drugs, where both platelet count and functions are affected, which could be used for therapeutic drug monitoring.

The influence of green tea extract on nintedanib's bioavailability in patients with pulmonary fibrosis.

Nintedanib is an oral small-molecule kinase inhibitor and first-line treatment for idiopathic pulmonary fibrosis. Nintedanib is a substrate of the drug efflux transporter ABCB1. Green tea flavonoids --especially epigallocatechin gallate (EGCG)-- are potent ABCB1 modulators. We investigated if concomitant administration of green tea extract (GTE) could result in a clinically relevant herb-drug interaction. Patients were randomized between A-B and B-A, with A being nintedanib alone and B nintedanib with GTE. Both periods lasted 7 days, in which nintedanib was administered twice daily directly after a meal. In period B, patients additionally received capsules with GTE (500 mg BID, >60% EGCG). Pharmacokinetic sampling for 12 h was performed at day 7 of each period. Primary endpoint was change in geometric mean for the area under the curve (AUC0-12 h). A linear mixed model was used to analyse AUCs and maximal concentration (Cmax). In 26 included patients, the nintedanib AUC0-12 h was 21% lower (95% CI -29% to -12%; P < 0.001) in period B (with GTE) compared to period A. Cmax did not differ significantly between periods; - 14% (95% CI -29% to +4%; P = 0.12). The detrimental effect was predominant in patients with the ABCB1 3435 C>T wild type variant. No differences in toxicities were observed. Exposure to nintedanib decreased with 21% when administered 60 min after GTC for only 7 days. This is a statistically significant interaction which could potentially impair treatment efficacy. Before patients and physicians should definitely be warned to avoid this combination, prospective clinical validation of an exposure-response relationship is necessary.

Influence of probenecid on endoxifen systemic exposure in breast cancer patients on adjuvant tamoxifen treatment.

Introduction: In breast cancer patients treated with the anti-estrogen tamoxifen, low concentrations of the active metabolite endoxifen are associated with more disease recurrence. We hypothesized that we could increase endoxifen concentrations by induction of its formation and inhibition of its metabolism by co-administration of probenecid. Methods: We conducted a crossover study and measured endoxifen concentrations in patients on steady-state tamoxifen monotherapy and after 14 days of combination treatment with probenecid. Eleven evaluable patients were included. Results: Treatment with tamoxifen and probenecid resulted in a 26% increase of endoxifen area under the plasma concentration-time curve from 0 to 24 h (AUC0-24h) compared to tamoxifen monotherapy (95% confidence interval [CI]: 8-46%; p < 0.01), while the maximum observed endoxifen concentration increased with 24% (95% CI: 7-44%; p < 0.01). The metabolic ratio of endoxifen to tamoxifen increased with 110% (95% CI: 82-143%; p < 0.001) after the addition of probenecid. Conclusion: Probenecid resulted in a clinically relevant increase of endoxifen concentrations in breast cancer patients treated with adjuvant tamoxifen. This combination therapy could provide a solution for patients with a CYP2D6-poor metabolizer phenotype or endoxifen concentrations below the threshold despite earlier tamoxifen dose.

Therapeutic Drug Monitoring of Endoxifen for Tamoxifen Precision Dosing: Feasible in Patients with Hormone-Sensitive Breast Cancer.

BACKGROUND: Endoxifen is the most important active metabolite of tamoxifen. Several retrospective studies have suggested a minimal or threshold endoxifen systemic concentration of 14-16 nM is required for a lower recurrence rate. The aim of this study was to investigate the feasibility of reaching a predefined endoxifen level of ≥ 16 nM (5.97 ng/mL) over time using therapeutic drug monitoring (TDM). METHODS: This prospective open-label intervention study enrolled patients who started treatment with a standard dose of tamoxifen 20 mg once daily for early breast cancer. An outpatient visit was combined with a TDM sample at 3, 4.5, and 6 months after initiation of the tamoxifen treatment. The tamoxifen dose was escalated to a maximum of 40 mg if patients had an endoxifen concentration < 16 nM. The primary endpoint of the study was the percentage of patients with an endoxifen level ≥ 16 nM at 6 months after the start of therapy compared with historical data, in other words, 80% of patients with endoxifen levels ≥ 16 nM with standard therapy. RESULTS: In total, 145 patients were included. After 6 months, 89% of the patients had endoxifen levels ≥ 16 nM, compared with a literature-based 80% of patients with endoxifen levels ≥ 16 nM at baseline (95% confidence interval 82-94; P = 0.007). In patients with an affected CYP2D6 allele, it was not always feasible to reach the predefined endoxifen level of ≥ 16 nM. No increase in tamoxifen-related adverse events was reported after dose escalation. CONCLUSION: This study demonstrated that it is feasible to increase the percentage of patients with endoxifen levels ≥ 16 nM using TDM. TDM is a safe strategy that offers the possibility of nearly halving the number of patients with endoxifen levels < 16 nM.

Effect of the Proton Pump Inhibitor Esomeprazole on the Systemic Exposure of Capecitabine: Results of A Randomized Crossover Trial.

Retrospective data suggest that gastric acid reduction by proton pump inhibitors (PPIs) impairs the dissolution and subsequent absorption of capecitabine, and thus potentially reduces the capecitabine exposure. Therefore, we examined prospectively the effect of esomeprazole on the pharmacokinetics of capecitabine. In this randomized crossover study, patients with cancer were assigned to 2 sequence groups, each consisting of 3 phases: capecitabine with esomeprazole administration 3 hours before (phase A), capecitabine alone (phase B), and capecitabine concomitant with cola and esomeprazole co-administration 3 hours before (phase C). The primary end point was the relative difference (RD) in exposure to capecitabine assessed by the area under the plasma concentration-time curve from zero to infinity (AUC0-inf ) and analyzed by a linear mixed effect model. Twenty-two evaluable patients were included in the analysis. After esomeprazole, there was a 18.9% increase in AUC0-inf of capecitabine (95% confidence interval (CI) -10.0% to 57.0%, P = 0.36). In addition, capecitabine half-life was significantly longer after esomeprazole (median 0.63 hours vs. 0.46 hours, P = 0.005). Concomitant cola did not completely reverse the effects observed after esomeprazole (RD 3.3% (95% CI -16.3 to 27.4%, P = 1.00). Capecitabine exposure is not negatively influenced by esomeprazole cotreatment. Therefore, altered capecitabine pharmacokinetics do not explain the assumed worse clinical outcome of PPI-cotreated patients with cancer.

Tissue Type Differences in ABCB1 Expression and Paclitaxel Tissue Pharmacokinetics in Patients With Esophageal Cancer.

Background: Data from previous work suggests that there is no correlation between systemic (plasma) paclitaxel exposure and efficacy in patients treated for esophageal cancer. In this trial, we investigated ATP-binding cassette efflux transporter expression and intratumoral pharmacokinetics of paclitaxel to identify changes which could be a first sign of chemoresistance. Methods: Patients with esophageal cancer treated with paclitaxel and carboplatin (± concomitant radiotherapy) were included. During the first and last cycle of weekly paclitaxel, blood samples and biopsies of esophageal mucosa and tumor tissue were taken. Changes in paclitaxel exposure and expression of ABCB1 (P-glycoprotein) over time were studied in both tumor tissue and normal appearing esophageal mucosa. Results: ABCB1 was significantly higher expressed in tumor tissue compared to esophageal tissue, during both the first and last cycle of paclitaxel (cycle 1: p < 0.01; cycle 5/6: p = 0.01). Interestingly, ABCB1 expression was significantly higher in adenocarcinoma than in squamous cell carcinoma (p < 0.01). During the first cycle, a trend towards a higher intratumoral paclitaxel concentration was observed compared to the esophageal mucosa concentration (RD:43%; 95%CI: -3% to 111% p = 0.07). Intratumoral and plasma paclitaxel concentrations were significantly correlated during the first cycle (AUC0-48 h: r = 0.72; p < 0.01). Conclusion: Higher ABCB1 expression in tumor tissue, and differences between histological tumor types might partly explain why tumors respond differently to systemic treatment. Resistance by altered intratumoral paclitaxel concentrations could not be demonstrated because the majority of the biopsies taken at the last cycle of paclitaxel did contain a low amount of tumor cells or no tumor.

Docetaxel Skin Exposure and Micronucleation Contributes to Skin Toxicity Caused by CPC634.

Docetaxel entrapped nanoparticle CPC634 is associated with dose-related skin toxicity that resembles conventional docetaxel (Cd)-related skin toxicity. This study compared the cutaneous pharmacokinetics and pharmacodynamics of docetaxel and CPC634. In this randomised cross-over study, patients with solid tumours received one cycle of CPC634 and Cd (both at 75 mg/m2). Skin biopsies were taken at baseline and at day 8 of both cycles. Released and total docetaxel (released docetaxel plus entrapped docetaxel) concentrations and histopathological changes in the skin biopsies were evaluated. Twenty patients underwent paired skin biopsies for pharmacokinetic analysis and 10 patients had biopsies available for histopathological assessment. The total skin docetaxel concentration was 369% (95%CI: 229% to 569%, p < 0.001) higher after CPC634 administration compared to Cd while the released docetaxel concentrations were not statistically different (95%CI: -9% to 63%, p = 0.169). The CPC634 released docetaxel concentration in the skin was positively correlated with plasma concentrations (Pearson's correlation 0.48, p = 0.03). Histopathological examination revealed increased apoptosis, mitotic cells with nuclear atypia, and micronucleation with an enhanced Ki-67 index for both compounds. In conclusion, both CPC634 and Cd treatment result in docetaxel exposure in the skin causing cutaneous anti-mitotic effects such as micronucleation, which could induce an inflammatory reaction leading to skin toxicity.

Effect of Scalp Cooling on the Pharmacokinetics of Paclitaxel.

Chemotherapy-induced alopecia (CIA), a side effect with high impact, can be prevented by cooling the scalp during the administration of some cytotoxic drugs. However, the effects of this prolonged scalp cooling on the pharmacokinetics of chemotherapy have never been investigated. In this study, we compared the pharmacokinetics of the widely used chemotherapeutic agent paclitaxel (weekly dose of 80-100 mg/m2) in female patients with solid tumors using concomitant scalp cooling (n = 14) or not (n = 24). Blood samples were collected in all patients for pharmacokinetic analyses up to 6 h after one course of paclitaxel administration. The primary endpoint was the clearance (L/h) of paclitaxel. Paclitaxel clearance-expressed as relative difference in geometric means-was 6.8% (90% CI: -16.7% to 4.4%) lower when paclitaxel was administered with concomitant scalp cooling versus paclitaxel infusions without scalp cooling. Within the subgroup of patients using scalp cooling, paclitaxel clearance was not statistically significantly different between patients with CIA (alopecia grade 1 or 2) and those without CIA. Hence, scalp cooling did not negatively influence the clearance of paclitaxel treatment.

Quantification of ribociclib in dried blood spots by LC-MS/MS: Method development and clinical validation.

A reliable, specific, selective and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of ribociclib in both dried blood spot (DBS) samples and potassium EDTA plasma. DBS samples were obtained simultaneously with a plasma sample in advanced breast cancer patients treated with ribociclib. A 6 mm disk from the central part of the dried blood spot sample was punched, followed by extraction of ribociclib using liquid-liquid extraction spiked with ribociclib-d6 as internal standard. Concentrations of ribociclib in DBS samples were correlated with corresponding plasma concentrations. From the blood sample also hematocrit was determined. The method was validated for selectivity, sensitivity, precision, lower limit of detection, linearity, stability and accuracy according to the food and drug administration (FDA) guideline. The within- and between-run precisions were ≤10.6 and ≤1.07 %, respectively; while the average accuracy ranged from 100 to 103 %. The influence of hematocrit on validation parameters was tested in the range of 0.20 - 0.40 L/L. No influence of hematocrit on validation parameters was observed. Regression analysis and a Bland-Altman plot indicated correlation between the results obtained from DBS and plasma samples. A strong correlation (R2 >0.97) between DBS samples and plasma concentration from 17 breast cancer patients was found. A number of 12 out of 17 processed DBS samples (71 %) fell inside the acceptable range of 20 % difference of simultaneously obtained plasma samples. The lower limit of quantification in DBS is 10.0 ng/mL and linearity was demonstrated up to 1000 ng/mL. In conclusion, the newly developed assay met the required standard for validation. The methods were used to study ribociclib disposition in patients with advanced breast cancer.