A rapid and sensitive LC-MS/MS method for quantifying oxycodone, noroxycodone, oxymorphone and noroxymorphone in human plasma to support pharmacokinetic drug interaction studies of oxycodone

A sensitive and reliable LC-MS/MS method was developed and validated for the quantification of oxycodone and metabolites in human plasma. The method has a runtime of 6 min and a sensitivity of 0.1 μg/L for all analytes. Sample preparation consisted of protein precipitation. Separation was performed on a Kinetix biphenyl column (2.1 × 100 mm, 1.7 μm), using ammonium formate 5 mm in 0.1% aqueous formic acid and methanol LC-MS grade 100% in gradient elution at a flow rate of 0.4 ml/min. Detection was performed in multiple reaction monitoring mode using positive electrospray ionization. The method was linear over the calibration range of 0.1-25.0 μg/L for oxycodone, noroxycodone and noroxymorphone and 0.1-5.0 μg/L for oxymorphone. The method demonstrated good performance in terms of intra- and interday accuracy (86.5-110.3%) and precision (CV 1.7-9.3%). The criteria for the matrix effect were met (CV < 15%) except for noroxymorphone, for which an additional method was applied to compensate for the matrix effect. Whole blood samples were stable for 4 h at room temperature. Plasma samples were stable for 24 h at room temperature and 3 months at -20°C. Furthermore, the method was successfully applied in a pharmacokinetic drug interaction study of oxycodone and enzalutamide in patients with prostate cancer.

Enzalutamide Reduces Oxycodone Exposure in Men with Prostate Cancer

BACKGROUND AND OBJECTIVE

Up to 90% of patients with castration-resistant prostate cancer (CRPC) will develop symptomatic bone metastases requiring pain medication, with opioids being the mainstay of therapy in treating moderate and severe pain. Enzalutamide is an androgen receptor antagonist for the treatment of CRPC and a strong inducer of cytochrome P450 (CYP)3A4. Hereby, enzalutamide potentially reduces the exposure of oxycodone, an opioid metabolized by CYP3A4 and CYP2D6. Our objective was to evaluate the potential drug-drug interaction of enzalutamide and oxycodone.

METHODS

A prospective, nonrandomized, open-label, two-arm parallel study was performed. All patients received a single dose of 15 mg normal-release oxycodone. Patients in the enzalutamide arm (ENZ-arm) received enzalutamide 160 mg once daily. Plasma concentrations of oxycodone and its metabolites were quantified using a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) method.

RESULTS

Twenty-six patients (13 ENZ-arm; 13 control arm) were enrolled in the study. Enzalutamide decreased the mean AUC0-8 h and Cmax of oxycodone with, respectively, 44.7% (p < 0.001) and 35.5% (p = 0.004) compared with the control arm. The AUC0-8 h and Cmax of the active metabolite oxymorphone were 74.2% (p < 0.001) and 56.0% (p = 0.001) lower in the ENZ-arm compared with the control arm. In contrast, AUC0-8 h and Cmax of the inactive metabolites noroxycodone and noroxymorphone were significantly increased by enzalutamide.

CONCLUSION

Co-administration of enzalutamide significantly reduced exposure to oxycodone and its active metabolite oxymorphone in men with prostate cancer. This should be taken into account when prescribing enzalutamide combined with oxycodone.

Early on-treatment changes in circulating tumor DNA fraction and response to enzalutamide or abiraterone in metastatic castration-resistant prostate cancer

PURPOSE

Androgen receptor pathway inhibitors (ARPI) are standard of care for treatment-naive metastatic castration-resistant prostate cancer (mCRPC), but rapid resistance is common. Early identification of resistance will improve management strategies. We investigated whether changes in circulating tumor DNA (ctDNA) fraction during ARPI treatment are linked with mCRPC clinical outcomes.

EXPERIMENTAL DESIGN

Plasma cell-free DNA was collected from 81 patients with mCRPC at baseline and after 4-weeks of first-line ARPI treatment during two prospective multi-centre observational studies (NCT02426333;NCT02471469). CtDNA fraction was calculated from somatic mutations in targeted sequencing and genome copy number profiles. Samples were classified into detected vs. undetected ctDNA. Outcome measurements were progression-free survival (PFS) and overall survival (OS). Non-durable treatment response was defined as PFS ≤ 6 months.

RESULTS

CtDNA was detected in 48/81 (59%) baseline and 29/81 (36%) 4-week samples. CtDNA fraction for samples with detected ctDNA was lower at 4-weeks vs. baseline (median 5.0% vs. 14.5%, P=0.017). PFS and OS was shortest for patients with persistent ctDNA at 4 weeks (univariate hazard ratio 4.79 (95%CI, 2.62-8.77) and 5.49 (95%CI, 2.76-10.91), respectively), independent of clinical prognostic factors. For patients exhibiting change from detected to undetected ctDNA by 4-weeks, there was no significant PFS difference versus patients with baseline undetected ctDNA. CtDNA change had a positive predictive value of 88% and negative predictive value of 92% for identifying non-durable responses.

CONCLUSIONS

Early changes in ctDNA% are strongly linked to duration of first-line ARPI treatment benefit and survival in mCRPC and may inform early therapy switches or treatment intensification.

RNA Biomarkers as a Response Measure for Survival in Patients with Metastatic Castration-Resistant Prostate Cancer

Treatment evaluation in metastatic castration-resistant prostate cancer is challenging. There is an urgent need for biomarkers to discriminate short-term survivors from long-term survivors, shortly after treatment initiation. Thereto, the added value of early RNA biomarkers on predicting progression-free survival (PFS) and overall survival (OS) were explored. The RNA biomarkers: KLK3 mRNA, miR-375, miR-3687, and NAALADL2-AS2 were measured in 93 patients with mCRPC, before and 1 month after start of first-line abiraterone acetate or enzalutamide treatment, in two prospective clinical trials. The added value of the biomarkers to standard clinical parameters in predicting PFS and OS was tested by Harell's C-index. To test whether the biomarkers were independent markers of PFS and OS, multivariate Cox regression was used. The best prediction model for PFS and OS was formed by adding miR-375 and KLK3 (at baseline and 1 month) to standard clinical parameters. Baseline miR-375 and detectable KLK3 after 1 month of therapy were independently related to shorter PFS, which was not observed for OS. In conclusion, the addition of KLK3 and miR-375 (at baseline and 1 month) to standard clinical parameters resulted in the best prediction model for survival assessment.

The effect of chemotherapy on the exposure-response relation of abiraterone in metastatic castration-resistant prostate cancer

Aims

To assess whether the exposure–response relation for abiraterone is different in pre‐chemotherapy patients compared to post‐chemotherapy patients with metastatic castration‐resistant prostate cancer (mCRPC).

Methods

Data were collected from three clinical studies in mCRPC patients treated with abiraterone acetate. Cox regression analysis was used to determine the relation between abiraterone exposure and survival (progression‐free survival [PFS] and overall survival [OS]). An interaction term was used to test whether chemotherapy pretreatment was an effect modifier. To investigate the effect of the previously defined exposure threshold of 8.4 ng/mL on survival, Kaplan–Meier analysis was used.

Results

In total, 98 mCRPC patients were included, of which 78 were pre‐chemotherapy and 20 were post‐chemotherapy patients. Chemotherapy pretreatment in mCRPC setting appears to be an effect modifier. In pre‐chemotherapy patients, no significant association between abiraterone exposure and survival was observed (HR 0.68 [95% CI 0.42–1.10], P = .12 and HR 0.85 [95% CI 0.46–1.60], P = .61, PFS and OS, respectively) and no longer survival was seen for patients with an abiraterone exposure above the predefined threshold. In contrast, a significant association was seen in post‐chemotherapy patients (HR 0.30 [95% CI 0.12–0.74], P = .01 and HR 0.38 [95% CI 0.18–0.82] P = .01, PFS and OS, respectively), with an increased survival when exposed above this threshold.

Conclusion

Chemotherapy pretreatment in mCRPC setting modifies the abiraterone exposure–response relation. No relation between abiraterone exposure and survival was seen for pre‐chemotherapy patients. Therefore, potentially lower doses can be used in this setting to prevent overtreatment and reduce financial toxicity.

Concentration-QT modelling in early clinical oncology settings: Simulation evaluation of performance

AIMS

Concentration-QT modelling (C-QTc) of first-in-human data has been rapidly adopted as the primary evaluation of QTc interval prolongation risk. Here, we evaluate the performance of C-QTc in early oncology settings (i.e., patients, no placebo or supratherapeutic dose, 3 + 3 designs).

METHODS

C-QTc performance was evaluated across three oncology scenarios using a simulation-estimation approach: (scen1) typical dose-escalation testing six dose levels (n = 21); (scen2) small dose-escalation testing two dose levels (n = 9); (scen3) expansion cohorts at one dose level (n = 6-140). True ΔΔQTc effects ranged from 3 ms ("no effect") to 20 ms ("large effect"). Performance was assessed based on the upper limit of the ΔQTc two-sided 90% CI against a threshold of 10 or 20 ms.

RESULTS

The performance against the 10 ms threshold was limited based on C-QTc data from typical dose escalation (scen1) and acceptable performance was observed only for relatively large expansions (n ≥ 45; scen3). Performance against the 20 ms threshold was acceptable based on C-QTc data from a typical dose escalation (scen1) or dose expansion cohort n > 10 (scen3). In general, pooling C-QTc data from dose escalation and expansion cohorts substantially improved the performance and reduced the ΔQTc 90% CI width.

CONCLUSION

C-QTc performance appeared limited using a 10 ms threshold, but acceptable against a 20 ms threshold. Selection of threshold may be informed by the benefit-risk balance in a specific disease area. Acceptable precision (i.e., confidence intervals) of the estimated ΔQTc, regardless of its magnitude, can be facilitated by pooling data from dose escalation and expansion cohorts.

Liquid biopsy reveals KLK3 mRNA as a prognostic marker for progression free survival in patients with metastatic castration-resistant prostate cancer undergoing first-line abiraterone acetate and prednisone treatment

Circulating RNAs extracted from liquid biopsies represent a promising source of cancer‐ and therapy‐related biomarkers. We screened whole blood from patients with metastatic castration‐resistant prostate cancer (mCRPC) following their first‐line treatment with abiraterone acetate and prednisone (AA‐P) to identify circulating RNAs that may correlate with progression‐free survival (PFS). In a prospective multicenter observational study, 53 patients with mCRPC were included after they started first‐line AA‐P treatment. Blood was drawn at baseline, 1, 3, and 6 months after treatment initiation. The levels of predefined circulating RNAs earlier identified as being upregulated in patients with mCRPC (e.g., microRNAs, long noncoding RNAs, and mRNAs), were analyzed. Uni‐ and multivariable Cox regression and Kaplan–Meier analyses were used to analyze the prognostic value of the various circulating RNAs for PFS along treatment. Detectable levels of kallikrein‐related peptidase 3 (KLK3) mRNA at baseline were demonstrated to be an independent prognostic marker for PFS (201 vs 501 days, P = 0.00054). Three months after AA‐P treatment initiation, KLK3 could not be detected in the blood of responding patients, but was still detectable in 56% of the patients with early progression. Our study confirmed that KLK3 mRNA detection in whole blood is an independent prognostic marker in mCRPC patients receiving AA‐P treatment. Furthermore, the levels of circulating KLK3 mRNA in patients receiving AA‐P treatment might reflect treatment response or early signs of progression.

Prognostic Value of Novel Liquid Biomarkers in Patients with Metastatic Castration-Resistant Prostate Cancer Treated with Enzalutamide: A Prospective Observational Study

BACKGROUND

Several treatment options were recently added for metastatic castration-resistant prostate cancer (mCRPC). However, response to therapy is variable, and biomarkers that can guide treatment selection and response evaluation are lacking. Circulating RNAs are a promising source of biomarkers. We explored messenger RNAs (mRNAs), microRNAs (miRNAs), and long noncoding RNAs (lncRNAs) as potential biomarkers in liquid biopsies of patients with mCRPC treated with enzalutamide.

METHODS

Forty patients were included in this prospective multicenter observational study. Whole blood was drawn at baseline and 1, 3, and 6 months after start of therapy. Four mRNAs, 6 miRNAs, and 5 lncRNAs were analyzed by quantitative PCR. RNA levels in 30 healthy individuals were used as controls. RNA expression data were analyzed by Kaplan-Meier and Cox regression analyses, and the primary end point was progression-free survival. Clinical factors were included in the multivariable Cox regression analysis.

RESULTS

Levels of 2 miRNAs, miR-375 and miR-3687, and 1 lncRNA, N-acetylated alpha-linked acidic dipeptidase like 2 antisense RNA 2 (NAALADL2-AS2), were more than 2-fold higher in patients with mCRPC compared with healthy volunteers. Patients with higher levels of miR-375 or miR-3687 showed a shorter time to progression. Patients with higher levels of NAALADL2-AS2 showed a longer time to progression. In the multivariable Cox regression analysis, higher miR-375, miR-3687 and serum prostate-specific antigen concentrations were shown to be independent predictors for shorter time to progression.

CONCLUSIONS

We identified miR-3687 as a novel prognostic marker for response in patients with CRPC treated with enzalutamide, and we confirmed the prognostic value of miR-375.

Abstract 1413: Exploring the prognostic value of microRNAs and drug exposure in patients with metastatic castration resistant prostate cancer treated with abiraterone: a prospective observational study

Background Abiraterone acetate is registered for treatment of metastatic prostate cancer, including those with castration-resistant disease (mCRPC). Although it improves overall survival and progression free survival (PFS), treatment response differs between patients. Biomarkers to predict treatment response are lacking. Liquid biopsies containing microRNAs (miRNAs) are a promising source of prognostic biomarkers in mCRPC patients. Furthermore, the exposure to abiraterone in plasma is highly variable and subtherapeutic exposure might contribute to the variability in response to therapy. We explored the prognostic value of microRNAs and drug exposure in mCRPC patients treated with abiraterone.

Methods In a prospective multi-center observational study, 53 patients with mCRPC were included who started pre-chemotherapy abiraterone treatment. Blood was drawn at baseline, 1, 3 and 6 months after start of treatment. The following predefined miRNAs were selected; miR-21, miR-141, miR-200a, miR-200c, miR-375, miR-3687 and abiraterone concentrations were measured. MiRNA-levels in 30 healthy individuals served as controls. Relative miRNA-levels were calculated by the ΔΔCt method. If the geometric mean of a miRNA was more than 2-fold higher in patients versus healthy controls, they were included for survival analysis. Ctrough levels after 1, 3 and 6 months of therapy were measured. The average Ctrough level per patient was used for further analysis. The prognostic value of miRNAs and drug exposure for PFS (radiographic, biochemical or clinical progression) was analyzed with Kaplan-Meier (KM) analysis and tested with a log-rank test. Cut-off values for miRNAs in KM analysis were calculated using maximally selected rank statistics and for the relation with abiraterone Ctrough the earlier defined threshold of 8.4ng/ml was used.

Results Of the miRNAs analyzed, miR-375 was more than 2-fold higher in mCRPC patients versus healthy controls. Patients with more than 2.16 fold higher miR-375 compared to healthy controls showed a trend towards shorter PFS, median 352 vs. 456 days (p=0.076). No PFS benefit was shown for patients with a mean abiraterone Ctrough concentration ≥8.4ng/ml compared to patients below this threshold, median 411 vs. 409 days (p=0.81).

Conclusion High levels of miR-375 might be a prognostic biomarker for PFS in patients with mCRPC treated with abiraterone. The prognostic value of this miRNA should be further explored in a larger cohort of patients. Additionally, the functionality of miR-375 should be further elucidated. The beneficial effect of higher abiraterone exposure levels could not be confirmed in this study for this patient population.

Citation Format: Emmy Boerrigter, Guillemette E. Benoist, Inge M. van Oort, Gerald W. Verhaegh, Onno van Hooij, Levi Groen, Frank Smit, Irma M. Oving, Pieter de Mol, Tineke J. Smilde, Diederik M. Somford, Niven Mehra, Jack A. Schalken, Nielka P. van Erp. Exploring the prognostic value of microRNAs and drug exposure in patients with metastatic castration resistant prostate cancer treated with abiraterone: a prospective observational study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1413.

A prospective phase I multicentre randomized cross-over pharmacokinetic study to determine the effect of food on abiraterone pharmacokinetics

Purpose

Abiraterone acetate is used at a fixed oral dose of 1000 mg once daily (OD) taken fasted. By administering abiraterone acetate with food, a reduced dose can potentially be given while maintaining equivalent abiraterone exposure. Moreover, administering abiraterone acetate with a breakfast is considered more patient friendly. The aim of this study was to establish the bio-equivalent lower dose of abiraterone when taken with a continental breakfast (CB) compared to the standard intake of 1000 mg OD fasted.

Methods

In this phase I, randomized cross-over, multi-center study, abiraterone pharmacokinetics (PK) were evaluated in patients with metastatic castration-resistant prostate cancer who were treated for 14 days with 1000 mg abiraterone acetate taken fasted, followed by 14 days of treatment with 500 mg taken with a CB.

Results

14 patients were enrolled into the study, of whom 12 were eligible for PK analysis. The geometric mean ratio (GMR) (fed/fasted) was 0.88 (90% CI 0.73–1.07) for area-under-the-curve (AUC_0–24h), 1.03 (90% CI 0.79–1.34) for C_max and 0.81 (90% CI 0.60–1.10) for C_trough, respectively. High inter-patient variability (> 50%) was found for all PK parameters under both intake conditions. Patients seemed to be slightly more satisfied about the intake of 500 mg abiraterone acetate when taken with a CB compared to 1000 mg fasted.

Conclusion

In conclusion, a bioequivalent lower dose of abiraterone taken with food could not be established in our study. Although based on the absence of a exposure–toxicity relationship, the strict bioequivalence margins as defined by the FDA guidelines could be applied more flexible for abiraterone. Information on the effect of food on abiraterone pharmacokinetics as presented in our study can be used for patients with difficulties taken their medication fasted.

Electronic supplementary material

The online version of this article (10.1007/s00280-019-03952-w) contains supplementary material, which is available to authorized users.

Development and Validation of a Bioanalytical Method to Quantitate Enzalutamide and its Active Metabolite N-Desmethylenzalutamide in Human Plasma: Application to Clinical Management of Patients With Metastatic Castration-Resistant Prostate Cancer

BACKGROUND

Enzalutamide is a potent androgen-signaling receptor inhibitor and is licensed for the treatment of metastatic castration-resistant prostate cancer. N-desmethylenzalutamide is the active metabolite of enzalutamide. A method to quantitate enzalutamide and its active metabolite was developed and validated according to the European Medicine Agency guidelines.

METHODS

Enzalutamide and N-desmethylenzalutamide were extracted by protein precipitation, separated on a C18 column with gradient elution and analyzed with tandem quadrupole mass spectrometry in positive ion mode. A stable deuterated isotope (D6-enzalutamide) was used as an internal standard. The method was tested and stability was studied in real-life patients with metastatic castration-resistant prostate cancer patients treated with enzalutamide.

RESULTS

The calibration curve covered the range of 500-50,000 ng/mL. Within- and between-day precisions were <8% and accuracies were within 108% for both enzalutamide and N-desmethylenzalutamide. Precisions for lower limit of quantification level were <10% and accuracies within 116% for enzalutamide and N-desmethylenzalutamide. Enzalutamide and N-desmethylenzalutamide stability was proven for 24 hours for whole blood at ambient temperature and 23 days for plasma at both ambient temperature and 2-8°C. Long-term patient plasma stability was shown for 14 months at -40°C.

CONCLUSIONS

This bioanalytical method was successfully validated and applied to determine plasma concentrations of enzalutamide and N-desmethylenzalutamide in clinical studies and in routine patient care.

A clinically relevant decrease in abiraterone exposure associated with carbamazepine use in a patient with castration-resistant metastatic prostate cancer

ADVERSE EVENT

Decreased abiraterone exposure after introducing carbamazepine.

DRUGS IMPLICATED

Abiraterone acetate and carbamazepine.

THE PATIENT

A 65-year-old man with metastatic castration resistant prostate cancer, was treated with abiraterone acetate and prednisolone, and received concomitant carbamazepine for treatment of facial neuropathy.

EVIDENCE THAT LINKS THE DRUG TO THE EVENT

The interaction was confirmed by a decrease in abiraterone exposure >2-fold (area-under-the-curve and trough levels). After discontinuation of carbamazepine therapy, the abiraterone exposure normalized. No alternative causes were found that explain the decrease in abiraterone exposure.

MECHANISM

Induction of CYP3A and potentially phase I metabolism (SULT2A1) by carbamazepine.

IMPLICATIONS FOR THERAPY

Clinicians and pharmacists should be aware of this clinically relevant interaction. The national drug-drug interaction checker does not warn for this interaction, whereas both the Lexicomp® and Micromedex® advice to avoid if possible or to increase the abiraterone dose frequency to twice daily. Carbamazepine should not be combined with abiraterone to avoid underexposure and suboptimal therapy. Therapeutic drug monitoring of abiraterone is useful to guide therapy when drug-drug interactions cannot be avoided.

Analytical challenges in quantifying abiraterone with LC-MS/MS in human plasma

A method was developed and validated to quantify abiraterone in human plasma. During assay development, several analytical challenges were encountered: limited stability in patient samples, adsorption to glass, coelution with metabolites and carry-over issues. Limited stability (2 h) was found for abiraterone in fresh plasma as well as whole blood at ambient temperature. When kept at 2-8°C, abiraterone in plasma was stable for 24 h and in whole blood for 8 h. Adsorption of abiraterone to glass materials was addressed by using polypropylene throughout the method. Carry-over was reduced to acceptable limits by incorporating a third mobile phase into the gradient. The chromatographic separation of abiraterone with its multiple metabolites was addressed by using a longer analytical column and adjusting the gradient. Abiraterone was extracted by protein precipitation, separated on a C18 column with gradient elution and analyzed with tandem quadrupole mass spectrometry in positive ion mode. A stable deuterated isotope was used as the internal standard. The assay ranges from 1 to 500 ng/mL. Within- and-between-day precisions and accuracies were below 13.4% and within 95-102%. This bioanalytical method was successfully validated and applied to determine plasma concentrations of abiraterone in clinical studies and in regular patient care for patients with metastatic castration-resistant prostate cancer.

Pharmacokinetic Aspects of the Two Novel Oral Drugs Used for Metastatic Castration-Resistant Prostate Cancer: Abiraterone Acetate and Enzalutamide

Two novel oral drugs that target androgen signaling have recently become available for the treatment of metastatic castration-resistant prostate cancer (mCRPC). Abiraterone acetate inhibits the synthesis of the natural ligands of the androgen receptor, whereas enzalutamide directly inhibits the androgen receptor by several mechanisms. Abiraterone acetate and enzalutamide appear to be equally effective for patients with mCRPC pre- and postchemotherapy. Rational decision making for either one of these drugs is therefore potentially driven by individual patient characteristics. In this review, an overview of the pharmacokinetic characteristics is given for both drugs and potential and proven drug–drug interactions are presented. Additionally, the effect of patient-related factors on drug disposition are summarized and the limited data on the exposure–response relationships are described. The most important pharmacological feature of enzalutamide that needs to be recognized is its capacity to induce several key enzymes in drug metabolism. The potency to cause drug–drug interactions needs to be addressed in patients who are treated with multiple drugs simultaneously. Abiraterone has a much smaller drug–drug interaction potential; however, it is poorly absorbed, which is affected by food intake, and a large interpatient variability in drug exposure is observed. Dose reductions of abiraterone or, alternatively, the selection of enzalutamide, should be considered in patients with hepatic dysfunction. Understanding the pharmacological characteristics and challenges of both drugs could facilitate decision making for either one of the drugs.