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.

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.

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.

Influence of green tea consumption on endoxifen steady-state concentration in breast cancer patients treated with tamoxifen.

BACKGROUND: Many cancer patients use additional herbs or supplements in combination with their anti-cancer therapy. Green tea-active ingredient epigallocatechin-3-gallate (EGCG)-is one of the most commonly used dietary supplements among breast cancer patients. EGCG may alter the metabolism of tamoxifen. Therefore, the aim of this study was to investigate the influence of green tea supplements on the pharmacokinetics of endoxifen; the most relevant active metabolite of tamoxifen. METHODS: In this single-center, randomized cross-over trial, effects of green tea capsules on endoxifen levels were evaluated. Patients treated with tamoxifen for at least 3 months were eligible for this study. After inclusion, patients were consecutively treated with tamoxifen monotherapy for 28 days and in combination with green tea supplements (1 g twice daily; containing 300 mg EGCG) for 14 days (or vice versa). Blood samples were collected on the last day of monotherapy or combination therapy. Area under the curve (AUC0-24h), maximum concentration (Cmax) and minimum concentration (Ctrough) were obtained from individual plasma concentration-time curves. RESULTS: No difference was found in geometric mean endoxifen AUC0-24h in the period with green tea versus tamoxifen monotherapy (- 0.4%; 95% CI - 8.6 to 8.5%; p = 0.92). Furthermore, no differences in Cmax (- 2.8%; - 10.6 to 5.6%; p = 0.47) nor Ctrough (1.2%; - 7.3 to 10.5%; p = 0.77) were found. Moreover, no severe toxicity was reported during the whole study period. CONCLUSIONS: This study demonstrated the absence of a pharmacokinetic interaction between green tea supplements and tamoxifen. Therefore, the use of green tea by patients with tamoxifen does not have to be discouraged.

Effects of prednisone on docetaxel pharmacokinetics in men with metastatic prostate cancer: A randomized drug-drug interaction study.

AIMS: Docetaxel has been approved for the treatment of metastatic prostate cancer in combination with prednisone. Since prednisone is known to induce the cytochrome P450 iso-enzyme CYP3A4, which is the main metabolizing enzyme of docetaxel in the liver, a potential drug-drug interaction may occur. In this prospective randomized pharmacokinetic cross-over study we investigated docetaxel exposure with concomitant prednisone, compared to docetaxel monotherapy in men with metastatic prostate cancer. METHODS: Patients scheduled to receive at least 6 cycles of docetaxel (75 mg/m2 ) and who gave written informed consent were randomized to receive either the 1st 3 cycles, or the last 3 consecutive cycles with prednisone (twice daily 5 mg). Pharmacokinetic blood sampling was performed during cycle 3 and cycle 6. Primary endpoint was difference in docetaxel exposure, calculated as area under the curve (AUC0-inf ) and analysed by means of a linear mixed model. Given the cross-over design the study was powered on 18 patients to answer the primary, pharmacokinetic, endpoint. RESULTS: Eighteen evaluable patients were included in the trial. Docetaxel concentration with concomitant prednisone (AUC0-inf 2784 ng*h/mL, 95% confidence interval 2436-3183 ng*h/mL) was similar to the concentration of docetaxel monotherapy (AUC0-inf 2647 ng*h/mL, 95% confidence interval 2377-2949 ng*h/mL). Exploratory analysis showed no toxicity differences between docetaxel monotherapy and docetaxel cycles with prednisone. CONCLUSION: No significant difference in docetaxel concentrations was observed. In addition, we found similar toxicity profiles in absence and presence of prednisone. Therefore, from a pharmacokinetic point of view, docetaxel may be administrated with or without prednisone.

Understanding taxanes in prostate cancer; importance of intratumoral drug accumulation.

BACKGROUND: Resistance to docetaxel is common in metastatic castration-resistant prostate cancer (mCRPC) and may be caused by sub-therapeutic intratumoral drug concentrations. Cabazitaxel demonstrated survival benefit in docetaxel-pretreated and docetaxel-refractory patients. In this study, we investigated whether the superior antitumor activity of cabazitaxel in mCRPC is explained by higher intratumoral cabazitaxel levels. Since recent studies suggest a reduced efficacy of docetaxel following treatment with novel androgen receptor (AR)-targeted agents, we also investigated taxane efficacy in an enzalutamide-resistant tumor model. METHODS: Intratumoral concentrations of docetaxel and cabazitaxel were correlated with antitumor activity in docetaxel-naïve, docetaxel-resistant, and enzalutamide-resistant patient-derived xenografts (PDXs) of prostate cancer. RESULTS: Intratumoral drug levels were negatively related to intrinsic and acquired resistance to docetaxel. Also, the observed stronger antitumor activity of cabazitaxel was associated with increased cumulative exposure and higher intratumoral of cabazitaxel concentrations in all PDXs. CONCLUSIONS: The superior antitumor activity of cabazitaxel in docetaxel- and enzalutamide-resistant tumors can be partly attributed to higher intratumoral drug concentrations. Especially for patients who are intrinsically resistant to docetaxel resulting from suboptimal intratumoral docetaxel concentrations, cabazitaxel may be the preferred chemotherapeutic agent. Prostate 76:927-936, 2016. © 2016 Wiley Periodicals, Inc.

Treatment with subcutaneous and transdermal fentanyl: results from a population pharmacokinetic study in cancer patients.

PURPOSE: Transdermal fentanyl is effective for the treatment of moderate to severe cancer-related pain but is unsuitable for fast titration. In this setting, continuous subcutaneous fentanyl may be used. As data on the pharmacokinetics of continuous subcutaneous fentanyl are lacking, we studied the pharmacokinetics of subcutaneous and transdermal fentanyl. Furthermore, we evaluated rotations from the subcutaneous to the transdermal route. METHODS: Fifty-two patients treated with subcutaneous and/or transdermal fentanyl for moderate to severe cancer-related pain participated. A population pharmacokinetic model was developed and evaluated using non-linear mixed-effects modelling. For rotations from subcutaneous to transdermal fentanyl, a 1:1 dose conversion ratio was used while the subcutaneous infusion was continued for 12 h (with a 50 % tapering after 6 h). A 6-h scheme with 50 % tapering after 3 h was simulated using the final model. RESULTS: A one-compartment model with first-order elimination and separate first-order absorption processes for each route adequately described the data. The estimated apparent clearance of fentanyl was 49.6 L/h; the absorption rate constant for subcutaneous and transdermal fentanyl was 0.0358 and 0.0135 h(-1), respectively. Moderate to large inter-individual and inter-occasion variability was found. Around rotation from subcutaneous to transdermal fentanyl, measured and simulated plasma fentanyl concentrations rose and increasing side effects were observed. CONCLUSIONS: We describe the pharmacokinetics of subcutaneous and transdermal fentanyl in one patient cohort and report several findings that are relevant for clinical practice. Further research is warranted to study the optimal scheme for rotations from the subcutaneous to the transdermal route.

Lysosomal Sequestration Determines Intracellular Imatinib Levels.

The intracellular uptake and retention (IUR) of imatinib is reported to be controlled by the influx transporter SLC22A1 (organic cation transporter 1). We recently hypothesized that alternative uptake and/or retention mechanisms exist that determine intracellular imatinib levels. Here, we systematically investigate the nature of these mechanisms. Imatinib uptake in cells was quantitatively determined by liquid chromatography-tandem mass spectrometry. Fluorescent microscopy was used to establish subcellular localization of imatinib. Immunoblotting, cell cycle analyses, and apoptosis assays were performed to evaluate functional consequences of imatinib sequestration. Uptake experiments revealed high intracellular imatinib concentrations in HEK293, the leukemic cell lines K562 and SD-1, and a gastrointestinal stromal tumor cell line GIST-T1. We demonstrated that imatinib IUR is time-, dose-, temperature-, and energy-dependent and provide evidence that SLC22A1 and other potential imatinib transporters do not substantially contribute to the IUR of imatinib. Prazosin, amantadine, NH4Cl, and the vacuolar ATPase inhibitor bafilomycin A1 significantly decreased the IUR of imatinib and likely interfere with lysosomal retention and accumulation of imatinib. Costaining experiments with LysoTracker Red confirmed lysosomal sequestration of imatinib. Inhibition of the lysosomal sequestration had no effect on the inhibition of c-Kit signaling and imatinib-mediated cell cycle arrest but significantly increased apoptosis in imatinib-sensitive GIST-T1 cells. We conclude that intracellular imatinib levels are primarily determined by lysosomal sequestration and do not depend on SLC22A1 expression.

Circadian variation in tamoxifen pharmacokinetics in mice and breast cancer patients.

The anti-estrogen tamoxifen is characterized by a large variability in response, partly due to pharmacokinetic differences. We examined circadian variation in tamoxifen pharmacokinetics in mice and breast cancer patients. Pharmacokinetic analysis was performed in mice, dosed at six different times (24-h period). Tissue samples were used for mRNA expression analysis of drug-metabolizing enzymes. In patients, a cross-over study was performed. During three 24-h periods, after tamoxifen dosing at 8 a.m., 1 p.m., and 8 p.m., for at least 4 weeks, blood samples were collected for pharmacokinetic measurements. Differences in tamoxifen pharmacokinetics between administration times were assessed. The mRNA expression of drug-metabolizing enzymes showed circadian variation in mouse tissues. Tamoxifen exposure seemed to be highest after administration at midnight. In humans, marginal differences were observed in pharmacokinetic parameters between morning and evening administration. Tamoxifen C(max )and area under the curve (AUC)0-8 h were 20 % higher (P < 0.001), and tamoxifen t(max) was shorter (2.1 vs. 8.1 h; P = 0.001), indicating variation in absorption. Systemic exposure (AUC0-24 h) to endoxifen was 15 % higher (P < 0.001) following morning administration. The results suggest that dosing time is of marginal influence on tamoxifen pharmacokinetics. Our study was not designed to detect potential changes in clinical outcome or toxicity, based on a difference in the time of administration. Circadian rhythm may be one of the many determinants of the interpatient and intrapatient pharmacokinetic variability of tamoxifen.

4ß-hydroxycholesterol as an endogenous CYP3A marker in cancer patients treated with taxanes.

AIM: Taxanes are anti-cancer agents used to treat several types of solid tumours. They are metabolized by cytochrome P450 (CYP) 3A, displaying a large pharmacokinetic (PK) variability. In this study, we evaluated the endogenous CYP3A4 marker 4ß-hydroxycholesterol (4ß-OHC) as a potential individual taxane PK predictor. METHODS: Serum 4ß-OHC and cholesterol concentrations were determined in 291 paclitaxel and 151 docetaxel-treated patients, and were subsequently correlated with taxane clearance. RESULTS: In the patients treated with paclitaxel, no clinically relevant correlations between the 4ß-OHC or 4ß-OHC : cholesterol ratio and paclitaxel clearance were found. In the patients treated with docetaxel, 4ß-OHC concentration was weakly correlated with docetaxel clearance in males (r = 0.35 P = 0.01, 95% CI 0.08, 0.58). Of the 10% patients with taxane outlier clearance values, 4ß-OHC did correlate with docetaxel clearance in males (r = 0.76, P = 0.03, 95% CI 0.12, 0.95). CONCLUSION: There was no clinical correlation between paclitaxel clearance and the CYP3A4 activity markers 4ß-OHC or the 4ß-OHC : cholesterol ratio. A weak correlation was observed between 4ß-OHC and docetaxel clearance, but only in males. This endogenous CYP3A4 marker has limited predictive value for taxane clearance in patients.

Population pharmacokinetic modelling to assess the impact of CYP2D6 and CYP3A metabolic phenotypes on the pharmacokinetics of tamoxifen and endoxifen.

AIMS: Tamoxifen is considered a pro-drug of its active metabolite endoxifen. The major metabolic enzymes involved in endoxifen formation are CYP2D6 and CYP3A. There is considerable evidence that variability in activity of these enzymes influences endoxifen exposure and thereby may influence the clinical outcome of tamoxifen treatment. We aimed to quantify the impact of metabolic phenotype on the pharmacokinetics of tamoxifen and endoxifen. METHODS: We assessed the CYP2D6 and CYP3A metabolic phenotypes in 40 breast cancer patients on tamoxifen treatment with a single dose of dextromethorphan as a dual phenotypic probe for CYP2D6 and CYP3A. The pharmacokinetics of dextromethorphan, tamoxifen and their relevant metabolites were analyzed using non-linear mixed effects modelling. RESULTS: Population pharmacokinetic models were developed for dextromethorphan, tamoxifen and their metabolites. In the final model for tamoxifen, the dextromethorphan derived metabolic phenotypes for CYP2D6 as well as CYP3A significantly (P < 0.0001) explained 54% of the observed variability in endoxifen formation (inter-individual variability reduced from 55% to 25%). CONCLUSIONS: We have shown that not only CYP2D6, but also CYP3A enzyme activity influences the tamoxifen to endoxifen conversion in breast cancer patients. Our developed model may be used to assess separately the impact of CYP2D6 and CYP3A mediated drug-drug interactions with tamoxifen without the necessity of administering this anti-oestrogenic drug and to support Bayesian guided therapeutic drug monitoring of tamoxifen in routine clinical practice.

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.

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.

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.

The OCT2/MATE1 Interaction Between Trifluridine, Metformin and Cimetidine: A Crossover Pharmacokinetic Study.

BACKGROUND AND OBJECTIVES: Trifluridine/tipiracil, registered for the treatment of patients with metastatic gastric and colorectal cancer, is a substrate and inhibitor for the organic cation transporter 2 (OCT2) and the multidrug and toxin extrusion protein 1 (MATE1), which raises the potential for drug-drug interactions with other OCT2/MATE1 modulators. Therefore, we prospectively examined the effect of an OCT2/MATE1 inhibitor (cimetidine) and substrate (metformin) on the pharmacokinetics of trifluridine. METHODS: In this three-phase crossover study, patients with metastatic colorectal or gastric cancer were sequentially treated with trifluridine/tipiracil alone (phase A), trifluridine/tipiracil concomitant with metformin (phase B) and trifluridine/tipiracil concomitant with cimetidine (phase C). The primary endpoint was the relative difference in exposure of trifluridine assessed by the area under the curve from timepoint zero to infinity. A > 30% change in exposure was considered clinically relevant. A p-value of < 0.025 was considered significant because of a Bonferroni correction. RESULTS: Eighteen patients were included in the analysis. Metformin did not significantly alter the exposure to trifluridine (- 12.6%; 97.5% confidence interval - 25.0, 1.8; p = 0.045). Cimetidine did alter the exposure to trifluridine significantly (+ 18.0%; 97.5% confidence interval 4.5, 33.3; p = 0.004), but this increase did not meet our threshold for clinical relevance. Metformin trough concentrations were not influenced by trifluridine/tipiracil. CONCLUSIONS: Our result suggests that the OCT2/MATE1 modulators cimetidine and metformin can be co-administered with trifluridine/tipiracil without clinically relevant effects on drug exposure. CLINICAL TRIAL REGISTRATION: NL8067 (registered 04-10-2019).

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.

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.

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.