Population pharmacokinetics of regorafenib in solid tumours: Exposure in clinical practice considering enterohepatic circulation and food intake

Bioequivalence and Pharmacokinetic Evaluation of Regorafenib Tablets in Healthy Chinese Volunteers

This was a single-center, randomized, open-label, 2-formulation, and 2-cycle crossover trial conducted in 48 healthy Chinese volunteers, under fasting and fed conditions. The participants received oral doses of the test formulation (regorafenib) and reference formulation (40 mg) during each study period. Blood samples were collected before and up to 144 hours after the formulations were administered to determine changes in the pharmacokinetic parameters and adverse reactions, which were then used to evaluate bioequivalence and safety. The geometric mean ratios of maximum blood concentration, area under the plasma concentration-time curve from time 0 to the last quantifiable concentration, and area under the plasma concentration-time curve from time 0 to infinity for regorafenib were as follows: 94.7%, 91.4%, and 91.7%, respectively, under fasting conditions; and 94.6%, 97.7%, and 98.8%, respectively, under fed conditions. The 90% confidence intervals for the geometric mean ratios were within the 80%-125% equivalence interval for both the fasting and fed tests. Ingesting high-fat and high-calorie foods increases exposure to regorafenib, leading to slower rates of absorption. The safety profiles of the 2 preparations were similar.

Radioactive ADME Demonstrates ARV-110's High Druggability Despite Low Oral Bioavailability

Proteolysis-targeting chimeras (PROTACs) have emerged as potentially effective therapeutic medicines, but their high molecular weight and poor solubility directly impact their oral bioavailability. This work synthesized 14C-labeled bavdegalutamide (ARV-110) as a model compound of PROTACs to evaluate its ADME features. Compared with targeted antitumor drugs, the use of food increased oral bioavailability of ARV-110 in rats from 10.75% to 20.97%, which is still undesirable. However, the therapeutic effect of ARV-110 at a low dose was much better than that of enzalutamide, demonstrating the specific catalytic medicinal properties of PROTACs. Moreover, the specific distribution of ARV-110 in subcutaneous prostate tumors was determined by quantitative whole-body autoradiography (QWBA). Notably, the specificity and activity of PROTACs take precedence over their oral absorption, and high oral bioavailability is not necessary to produce excellent therapeutic effects. This work presents a roadmap for developing future PROTAC medications from a radioactive drug metabolism and pharmacokinetics (DMPK) perspective.

Association between albumin-bilirubin grade and plasma trough concentrations of regorafenib and its metabolites M-2 and M-5 at steady-state in Japanese patients

The aim of the present study was to determine whether the trough plasma concentrations (C0) of regorafenib and its metabolites, the N-oxide metabolite (M-2) and the desmethyl N-oxide metabolite (M-5), in 21 patients receiving regorafenib therapy were affected by albumin-bilirubin (ALBI) grade. Regorafenib was administered at dosages ranging from 40 to 160 mg once daily on a 3-week-on, 1-week-off cycle. C0 values of regorafenib and its major metabolites were measured by high-performance liquid chromatography on day 8 after treatment initiation. The C0 values of regorafenib and metabolites M-2 and M-5 were significantly lower in patients with ALBI grade 2 as compared with grade 1 (P = 0.023, 0.003 and 0.017, respectively). The total C0 of regorafenib and its metabolites was significantly higher in ALBI grade 1 patients relative to grade 2 (3.489 μg/mL vs. 1.48 μg/mL; P = 0.009). The median relative dose intensity (RDI) of patients categorized as ALBI grade 2 was significantly lower than that of grade 1 patients (21.9% vs. 62.9%; P = 0.006). In 15 colorectal cancer patients among the total 21 patients, patients with ALBI grade 2 (n = 9) had a significantly shorter median overall survival time than patients with grade 1 (n = 6; P = 0.013). Administering a low dose of regorafenib to patients with ALBI grade 2 reduces the RDI of regorafenib and lowers treatment efficacy, as an appropriate C0 of regorafenib is not maintained. Monitoring the C0 of regorafenib regularly is necessary to guide dose adjustment.

Regorafenib plus Vincristine and Irinotecan in Pediatric Patients with Recurrent/Refractory Solid Tumors: An Innovative Therapy for Children with Cancer Study

PURPOSE

This phase Ib study defined the safety, MTD, and recommended phase II dose (RP2D) of regorafenib combined with vincristine and irinotecan (VI). Secondary objectives were evaluation of antitumor activity and pharmacokinetics (PK) of regorafenib and irinotecan.

PATIENTS AND METHODS

Patients aged 6 months to <18 years with relapsed/refractory solid malignancies [≥50% with rhabdomyosarcoma (RMS)] received regorafenib (starting dose 72 mg/m2/day) concomitantly or sequentially with vincristine 1.5 mg/m2 on days 1 and 8, and irinotecan 50 mg/m2 on days 1-5 (21-day cycle). Adverse events (AE) and tumor response were assessed. PK (regorafenib and irinotecan) were evaluated using a population PK model.

RESULTS

We enrolled 21 patients [median age, 10 years; 12, RMS; 5, Ewing sarcoma (EWS)]. The MTD/RP2D of regorafenib in the sequential schedule was 82 mg/m2. The concomitant dosing schedule was discontinued because of dose-limiting toxicities in 2 of 2 patients treated. Most common grade 3/4 (>30% of patients) AEs were neutropenia, anemia, thrombocytopenia, and leukopenia. The overall response rate was 48% and disease control rate [complete response (CR)/partial response/stable disease/non-CR/non-progressive disease] was 86%. Median progression-free survival was 7.0 months [95% confidence interval (CI), 2.9-14.8] and median overall survival was 8.7 months (95% CI, 5.5-16.3). When combined with VI, regorafenib PK was similar to single-agent PK in children and adults (treated with regorafenib 160 mg/day).

CONCLUSIONS

Regorafenib can be combined sequentially with standard dose VI in pediatric patients with relapsed/refractory solid tumors with appropriate dose modifications. Clinical activity was observed in patients with RMS and EWS (ClinicalTrials.gov NCT02085148).

Effects of regorafenib on the mononuclear/phagocyte system and how these contribute to the inhibition of colorectal tumors in mice

BACKGROUND

Regorafenib was previously shown to reduce tumor-associated macrophages and potently inhibit colony-stimulating factor 1 receptor (CSF1R), also known as CD115, in biochemical assays. The CSF1R signaling pathway is essential in the biology of the mononuclear/phagocyte system, which can promote the development of cancer.

METHODS

A deeper investigation of regorafenib's effects on CSF1R signaling was performed using preclinical in vitro and in vivo studies with syngeneic CT26 and MC38 mouse models of colorectal cancer. Peripheral blood and tumor tissue were analyzed mechanistically by flow cytometry using antibodies against CD115/CSF1R and F4/80 and by ELISA for chemokine (C-C motif) ligand 2 (CCL2) levels. These read-outs were correlated with drug levels for the detection of pharmacokinetic/pharmacodynamic relationships.

RESULTS

Potent inhibition of CSF1R by regorafenib and its metabolites M-2, M-4, and M-5 was confirmed in vitro in RAW264.7 macrophages. The dose-dependent growth inhibition of subcutaneous CT26 tumors by regorafenib was associated with a significant reduction in both the number of CD115^hi monocytes in peripheral blood and the number of selective subpopulations of intratumoral F4/80^hi tumor-associated macrophages. CCL2 levels were not affected by regorafenib in blood but increased in tumor tissue, which may contribute to drug resistance and prevent complete tumor remission. An inverse relationship between regorafenib concentration and the number of CD115^hi monocytes and CCL2 levels was observed in peripheral blood, supporting the mechanistic involvement of regorafenib.

CONCLUSIONS

These findings may be clinically useful in optimizing drug dosing using blood-based pharmacodynamic markers and in identifying resistance mechanisms and ways to overcome them by appropriate drug combinations.

Population pharmacokinetic analyses of regorafenib and capecitabine in patients with locally advanced rectal cancer (SAKK 41/16 RECAP)

AIM

Locally advanced rectal cancer (LARC) is an area of unmet medical need with one third of patients dying from their disease. With response to neoadjuvant chemo-radiotherapy being a major prognostic factor, trial SAKK 41/16 assessed potential benefits of adding regorafenib to capecitabine-amplified neoadjuvant radiotherapy in LARC patients.

METHODS

Patients received regorafenib at three dose levels (40/80/120 mg once daily) combined with capecitabine 825 mg/m² bidaily and local radiotherapy. We developed population pharmacokinetic models from plasma concentrations of capecitabine and its metabolites 5'-deoxy-5-fluorocytidine and 5'-deoxy-5-fluorouridine as well as regorafenib and its metabolites M-2 and M-5 as implemented into SAKK 41/16 to assess potential drug-drug interactions (DDI). After establishing parent-metabolite base models, drug exposure parameters were tested as covariates within the respective models to investigate for potential DDI. Simulation analyses were conducted to quantify their impact.

RESULTS

Plasma concentrations of capecitabine, regorafenib and metabolites were characterized by one- and two compartment models and absorption was described by parallel first- and zero-order processes and transit compartments, respectively. Apparent capecitabine clearance was 286 L/h (relative standard error [RSE] 14.9%, interindividual variability [IIV] 40.1%) and was reduced by regorafenib cumulative area under the plasma-concentration curve (median reduction of 45.6%) as exponential covariate (estimate -4.10×10^-4 , RSE 17.8%). Apparent regorafenib clearance was 1.94 L/h (RSE 12.1%, IIV 38.1%). Simulation analyses revealed significantly negative associations between capecitabine clearance and regorafenib exposure.

CONCLUSIONS

This work informs the clinical development of regorafenib and capecitabine combination treatment and underlines the importance to study potential DDI with new anticancer drug combinations.

Impact of trough concentrations of regorafenib and its major metabolites M-2 and M-5 on overall survival of chemorefractory metastatic colorectal cancer patients: Results from a multicentre GERCOR TEXCAN phase II study

PURPOSE

This prospective pharmacokinetic (PK) ancillary study of the TEXCAN phase II GERCOR trial of patients with chemorefractory metastatic colorectal cancer and treated with regorafenib (REGO) investigated correlations between overall survival (OS) and concentrations (C) of REGO and its active metabolites, M-2 and M-5.

METHODS

55 patients received REGO 160 mg/day for 21 days of a 28-day cycle (NCT02699073). REGO, M-2, M-5 were measured by liquid chromatography-mass spectrometry assay on day 15 of cycle 1 (C1) and 2 (C2). We studied the association between OS and Cmin of REGO, M-2 and M-5 at C1 and their accumulations between C1 and C2.

RESULTS

Medians of C2/C1 M-2 and M-5 ratios were 0.82 (interquartile range 0.50-1.78) and 0.75 (interquartile range 0.41-1.93), respectively. Patients with C2/C1 M-2 ratio ≥ median had improved survival compared to those < median (12.6 versus 4.0 months, P = 0.023), corresponding to a 66% mortality risk reduction in multivariate analysis. The C2/C1 M-2 ratio correlated with C1 REGO+M-2+M-5 (Csum; P = 0.006). Restricted cubic spline analysis showed an increased OS benefit as the C2/C1 M-2 ratio raises and when C1 Csum ranged between 2.5 and 5.5 mg/L. Patients within the Csum range had a reduced incidence of serious adverse events and improved OS.

CONCLUSIONS

We identified PK parameters associated with a survival benefit in patients with metastatic colorectal cancer treated by REGO. OS and safety were favourable when C1 REGO+M-2+M-5 Csum ranged between 2.5 and 5.5 mg/L. These results pave the way for individual REGO dose modification strategies based on PK monitoring.

CLINICAL TRIAL REFERENCE

NCT02699073.

Bioequivalence and Pharmacokinetic Evaluation of Two Oral Formulations of Regorafenib: An Open-Label, Randomised, Single-Dose, Two-Period, Two-Way Crossover Clinical Trial in Healthy Chinese Volunteers Under Fasting and Fed Conditions

Background

Regorafenib is an oral multi-kinase inhibitor approved for the treatment of solid tumours, but the pharmacokinetic profile of regorafenib in the Chinese population is unclear.

Objective

The aim of this study was to examine the pharmacokinetics, bioequivalence, and safety of two formulations of regorafenib 40 mg in healthy Chinese volunteers under fed and fasting conditions.

Methods

A single-centre, randomised, open-label, two-period, two-way crossover phase 1 trial was conducted by randomising a single oral dose of test (T) or reference (R, Stivarga^®) regorafenib (40 mg) to healthy Chinese volunteers under both fasting and fed conditions (high-fat and high-calorie diet). Pharmacokinetic parameters were calculated using non-compartmental methods. Adverse events were recorded to assess drug safety.

Results

Sixty-six participants were enrolled for both fasting and fed treatments. The 90% CIs geometric least-square means of ratio_T/R for regorafenib were completely contained within the equivalence margin of 80–125% under both fasting and fed conditions. Both formulations displayed similar and generally good safety profiles.

Conclusion

Single oral dose of the T (40 mg) and R (40 mg) regorafenib was bioequivalent under fasting and fed conditions and had similar favourable safety profiles among healthy Chinese volunteers.

Phase 1 dose-escalation and pharmacokinetic study of regorafenib in paediatric patients with recurrent or refractory solid malignancies

BACKGROUND

This phase 1 study evaluated safety, pharmacokinetics (PK), maximum tolerated dose (MTD), and antitumour activity of regorafenib in paediatric patients with solid tumours.

PATIENTS AND METHODS

Patients (aged 6 months to <18 years) with recurrent/refractory solid tumours received oral regorafenib once daily for 3 weeks on/1 week off. The starting dose (60 mg/m²) was derived from an adult physiology-based PK model and scaled to children; dose escalation was followed by safety expansion of the MTD cohort. Treatment-emergent adverse events (TEAEs) were evaluated using National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. Regorafenib PK was evaluated using a population PK model.

RESULTS

Forty-one patients (median age 13 years) received regorafenib (four cohorts: 60-93 mg/m²). Five of 23 evaluable patients experienced dose-limiting toxicities (Grade 4 thrombocytopenia, Grade 3 maculopapular rash, pyrexia, hypertension, and exfoliative dermatitis [each n = 1]). The MTD was defined as 82 mg/m². The most common Grade ≥3 drug-related TEAE was thrombocytopenia (10%). The incidence and severity of hypertension, diarrhoea, fatigue, hypothyroidism, and hand-foot skin reaction were lower than reported in adults. Regorafenib exposure increased with dose, with substantial overlap because of moderate-to-high interpatient variability. One patient with rhabdomyosarcoma experienced an unconfirmed partial response; 15 patients had stable disease, five for >16 weeks.

CONCLUSIONS

The recommended phase 2 dose of single-agent regorafenib in paediatric patients with solid malignancies is 82 mg/m². Regorafenib demonstrated acceptable tolerability and preliminary antitumour activity, supporting further investigation in paediatric patients.

CLINICAL TRIAL NUMBER

NCT02085148.

Antineoplastic dosing in overweight and obese cancer patients: an Associazione Italiana Oncologia Medica (AIOM)/Associazione Medici Diabetologi (AMD)/Società Italiana Endocrinologia (SIE)/Società Italiana Farmacologia (SIF) multidisciplinary consensus position paper

Most anticancer molecules are administered in body-size-based dosing schedules, bringing up unsolved issues regarding pharmacokinetic data in heavy patients. The worldwide spread of obesity has not been matched by improved methods and strategies for tailored drug dosage in this population. The weight or body surface area (BSA)-based approaches may fail to fully reflect the complexity of the anthropometric features besides obesity in cancer patients suffering from sarcopenia. Likewise, there is a lack of pharmacokinetic data on obese patients for the majority of chemotherapeutic agents as well as for new target drugs and immunotherapy. Therefore, although the available findings point to the role of dose intensity in cancer treatment, and support full weight-based dosing, empirical dose capping often occurs in clinical practice in order to avoid toxicity. Thus a panel of experts of the Associazione Italiana Oncologia Medica (AIOM), Associazione Medici Diabetologi (AMD), Società Italiana Endocrinologia (SIE), and Società Italiana Farmacologia (SIF), provides here a consensus statement for appropriate cytotoxic chemotherapy and new biological cancer drug dosing in obese patients.

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The worldwide spread of obesity is an emerging challenge also in cancer patients

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Weight or BSA-based approaches do not adequately address the critical issue of optimal dosing for cancer drugs under obesity

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Empirical dose capping is often employed in clinical practice to avoid toxicities among overweight and obese patients

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There is a lack of clinical and pharmacokinetic studies in this population

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Clinical practice recommendations should guide suitable dosing of cytotoxic and biological cancer drugs in obese patients

Pharmacokinetics of the oral multikinase inhibitor regorafenib and its association with real-world treatment outcomes

Purpose Despite the established activity of regorafenib in metastatic colorectal cancer (CRC), gastrointestinal stromal tumor (GIST), and hepatocellular carcinoma (HCC), its toxicity profile has limited clinical use. We aimed to evaluate the pharmacokinetics of regorafenib and its active metabolites M-2/M-5, and to clarify the relationships between total drug-related exposure and clinical outcomes in real-world practice. Methods Blood samples at steady state were obtained during Cycle 1 from patients treated with regorafenib. Plasma concentrations of regorafenib and its metabolites were measured by liquid chromatography-tandem mass spectrometry. The efficacy and safety endpoints were progression-free survival (PFS) and dose-limiting toxicities (DLTs), respectively. The exposure-response relationships were assessed. Results Thirty-four Japanese patients with advanced cancers were enrolled (CRC, n = 26; GIST and HCC, each n = 4). Nine patients started regorafenib treatment at the recommended dose of 160 mg once daily (3 weeks on / 1 week off), while the other patients received a reduced starting dose to minimize toxicities. The median PFS was significantly longer in patients achieving total trough concentrations (C_trough) of regorafenib and M-2/M-5 ≥2.9 µg/mL than those who did not (112 vs. 57 days; p = 0.044). Furthermore, the cumulative incidence of DLTs during the first 2 cycles was significantly higher in patients with summed C_trough levels ≥4.3 µg/mL than in others (p = 0.0003). Conclusions Dose titration of regorafenib to achieve drug-related C_trough levels between 2.9 and 4.3 µg/mL in Cycle 1 may improve efficacy and safety, warranting further investigation in a larger patient population.Clinical trial registry: Not applicable.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

How to Treat Hepatocellular Carcinoma in Elderly Patients

Hepatocellular carcinoma (HCC) is the primary tumour of the liver with the greatest incidence, particularly in the elderly. Additionally, improvements in the treatments for chronic liver diseases have increased the number of elderly patients who might be affected by HCC. Little evidence exists regarding HCC in old patients, and the elderly are still underrepresented and undertreated in clinical trials. In fact, this population represents a complex subgroup of patients who are hard to manage, especially due to the presence of multiple comorbidities. Therefore, the choice of treatment is mainly decided by the physician in the clinical practice, who often tend not to treat elderly patients in order to avoid the possibility of adverse events, which may alter their unstable equilibrium. In this context, the clarification of the optimal treatment strategy for elderly patients affected by HCC has become an urgent necessity. The aim of this review is to provide an overview of the available data regarding the treatment of HCC in elderly patients, starting from the definition of "elderly" and the geriatric assessment and scales. We explain the possible treatment choices according to the Barcelona Clinic Liver Cancer (BCLC) scale and their feasibility in the elderly population.

Feasibility of Extrapolating Randomly Taken Plasma Samples to Trough Levels for Therapeutic Drug Monitoring Purposes of Small Molecule Kinase Inhibitors

Small molecule kinase inhibitors (SMKIs) are widely used in oncology. Therapeutic drug monitoring (TDM) for SMKIs could reduce underexposure or overexposure. However, logistical issues such as timing of blood withdrawals hamper its implementation into clinical practice. Extrapolating a random concentration to a trough concentration using the elimination half-life could be a simple and easy way to overcome this problem. In our study plasma concentrations observed during 24 h blood sampling were used for extrapolation to trough levels. The objective was to demonstrate that extrapolation of randomly taken blood samples will lead to equivalent estimated trough samples compared to measured C_min values. In total 2241 blood samples were analyzed. The estimated C_trough levels of afatinib and sunitinib fulfilled the equivalence criteria if the samples were drawn after T_max. The calculated C_trough levels of erlotinib, imatinib and sorafenib met the equivalence criteria if they were taken, respectively, 12 h, 3 h and 10 h after drug intake. For regorafenib extrapolation was not feasible. In conclusion, extrapolation of randomly taken drug concentrations to a trough concentration using the mean elimination half-life is feasible for multiple SMKIs. Therefore, this simple method could positively contribute to the implementation of TDM in oncology.

Population pharmacokinetics of regorafenib in solid tumours: Exposure in clinical practice considering enterohepatic circulation and food intake

Aim

Regorafenib is an oral multikinase inhibitor with clinical efficacy in a range of advanced solid tumours. A population pharmacokinetic (PK) model was developed to evaluate the variability of the PK of regorafenib and its pharmacologically active metabolites M‐2 and M‐5 in solid tumours.

Methods

The model was initially developed using densely sampled phase 1 data and information on food intake to incorporate enterohepatic circulation (EHC) that was identified to considerably contribute to the PK of regorafenib. This was then applied to sparsely sampled data from four phase 3 studies in patients with advanced solid tumours. The need for exact food intake data to estimate individual drug exposure was evaluated.

Results

By incorporating EHC, the model adequately described the PK profiles of regorafenib, M‐2 and M‐5 after single and multiple doses in patients from phase 1 studies. Individual exposure in phase 3 studies was adequately described based on assumptions on the time and frequency of food intake, although exact food intake data are recommended to improve the estimation. Covariate analysis identified sex and body mass index (BMI) as impacting exposure to regorafenib, and sex as strongly impacting exposure to M‐2 and M‐5 (also influenced by the BMI effect on parent regorafenib in the joint model developed); however, these factors accounted for a small portion of the overall variability in exposure.

Conclusions

The adequate description of regorafenib PK after multiple dosing requires the incorporation of EHC. Neither single nor combined covariates predicted exposures that would warrant a priori regorafenib dose adjustment.