Pharmacologic activity and pharmacokinetics of metabolites of regorafenib in preclinical models

A Phase II Study of Regorafenib With a Lower Starting Dose in Patients With Metastatic Colorectal Cancer: Exposure-Toxicity Analysis of Unbound Regorafenib and Its Active Metabolites (RESET Trial)

BACKGROUND

Regorafenib demonstrated survival benefits as salvage therapy for patients with metastatic colorectal cancer. However, severe toxicities frequently occurred early in the treatment with the standard dose (160 mg/day), resulting in a dose reduction or interruption. To improve the tolerability and maintain sufficient efficacy, we conducted a phase II study of regorafenib with a lower starting dose (120 mg/day).

PATIENTS AND METHODS

Regorafenib was initiated at 120 mg/day, and the dosage was increased to 160 mg/day on day 15 of the first cycle for patients who had met the dose escalation criteria. The primary endpoint was the disease control rate (DCR). The pharmacokinetics of the total and unbound regorafenib and its active metabolites (M2, M5) were assessed.

RESULTS

A total of 70 patients were enrolled from September 2016 to December 2017. Only 6 patients achieved dose escalation to 160 mg on day 15 as planned. For the 68 evaluable patients, the DCR was 32.4% (95% confidence interval, 21.5%-44.8%), which was less than the threshold (30%) of our statistical hypothesis. The serum concentrations of total regorafenib for patients whose dose was escalated to 160 mg/day were significantly lower than those of the patients whose dose was not escalated (median, 3978 vs. 7244 nM; P = .027). The serum unbound concentrations of the sum of regorafenib and the active metabolites correlated significantly with the maximum grade of regorafenib-related symptomatic adverse events in the first cycle (11,138 vs. 19,096 pM; P = .035).

CONCLUSION

Regorafenib with a low starting dose of 120 mg/day did not achieve the expected DCR. A relationship of unbound exposure with toxicity was found.

The effect of gastrectomy on regorafenib exposure and progression-free survival in patients with advanced gastrointestinal stromal tumours

Aims

We investigated whether major gastrectomy influences the plasma exposure of regorafenib and treatment outcome.

Methods

Efficacy and pharmacokinetic data from 133 gastrointestinal stromal tumour patients included in a phase III trial were analysed. Patients were subdivided into 2 groups according to the extent of the gastrectomy (no/nonsignificant gastrectomy and major gastrectomy). Progression‐free survival (PFS) on regorafenib was measured and regorafenib and its pharmacological active metabolites plasma exposure were measured.

Results

A total of 133 patient were included, of whom 27 underwent major gastrectomy. In patients with no/nonsignificant gastrectomy the median PFS was 145 (interquartile range 43–281) days. The PFS in patients with a major gastrectomy was 172 (interquartile range 57–280) days. Regorafenib pharmacokinetic samples were collected in 80 patients of which 19 patients with a major gastrectomy and 61 patients with no/nonsignificant gastric surgery. The average ± standard deviation total concentration of regorafenib including the metabolites M‐2 and M‐5 was 6.9 ± 1.53 μmol/L and 6.7 ± 1.56 μmol/L in patient with major gastrectomy and no/nonsignificant gastrectomy respectively.

Conclusion

Our study shows that major gastrectomy did not influence plasma exposure of regorafenib and metabolites. In addition, no difference in PFS between the subgroups was seen.

Interaction Between Sex and Organic Anion-Transporting Polypeptide 1b2 on the Pharmacokinetics of Regorafenib and Its Metabolites Regorafenib-N-Oxide and Regorafenib-Glucuronide in Mice

Regorafenib, a multikinase inhibitor used in the treatment of various solid tumors, undergoes extensive uridine 5′‐diphosphate glucuronosyltransferase (Ugt)1a9‐mediated glucuronidation to form regorafenib‐N‐β‐glucuronide (M7; RG), but the contribution of hepatic uptake transporters, such as organic anion‐transporting polypeptide (Oatp)1b2, to the pharmacokinetics of regorafenib remains poorly understood. Using NONMEM‐based, population‐based, parent‐metabolite modeling, we found that Oatp1b2 and sex strongly impact the systemic exposure to RG in mice receiving oral regorafenib. Metabolic studies revealed that the liver microsomal expression of cytochrome P450 (Cyp)3a11 is twofold lower in female mice, whereas Ugt1a9 levels and function are not sex dependent. This finding is consistent with the metabolism of regorafenib occurring via two competing pathways, and the lack of Oatp1b2 results in decreased clearance of RG. The described model provides mechanistic insights into the in vivo disposition of regorafenib.

Metabolic profiling of the anti-tumor drug regorafenib in mice

Regorafenib is a novel tyrosine kinase inhibitor, which has been approved by the United States Food and Drug Administration for the treatment of various tumors. The purpose of the present study was to describe the metabolic map of regorafenib, and investigate its effect on liver function. Mass spectrometry-based metabolomics approach integrated with multiple mass defect filter was used to determine the metabolites of regorafenib in vitro incubation mixtures (human liver microsomes and mouse liver microsomes), serum, urine and feces samples from mice treated with 80 mg/kg regorafenib. Eleven metabolites including four novel metabolites were identified in the present investigation. As halogen substituted drug, reductive defluorination and oxidative dechlorination metabolites of regorafenib were firstly report in present study. By screening using recombinant cytochrome P450 s (CYPs), CYP3A4 was found to be the principal isoforms involved in regorafenib metabolism. The predication with a molecular docking model confirmed that regorafenib had potential to interact with the active sites of CYP3A4, CYP3A5 and CYP2D6. Serum chemistry analysis revealed no evidence of hepatic damage from regorafenib exposure. This study provided a global view of regorafenib metabolism and its potential side-effects.

Regorafenib in the treatment of metastatic colorectal cancer

Regorafenib is an orally available multikinase inhibitor, currently approved in metastatic chemorefractory colorectal cancer patients. The results of two large randomized Phase III trials are available, providing significant results in overall and progression-free survival in this situation. Its use requires a special attention regarding patient selection, dosing schedule and management of adverse events. Identifying patients who will tolerate and have benefit from regorafenib is a challenge for clinicians. Therapeutic monitoring (especially cfDNA), predictive biomarkers and specific perfusion-based imaging techniques will may be result in optimizing regorafenib treatment.

Evolution of regorafenib from bench to bedside in colorectal cancer: Is it an attractive option or merely a "me too" drug?

Colorectal cancer (CRC) is a major public health problem in the United States with an estimated 50,260 deaths in 2017. Over the past two decades, several agents have been approved by the US Food and Drug Administration (FDA) for the treatment of patients with metastatic CRC (mCRC). Regorafenib (BAY 73-4506) is a small-molecule multikinase inhibitor that was approved for the treatment of mCRC in 2012. This agent is a novel oral diphenylurea-based multikinase inhibitor that is active against several angiogenic receptor tyrosine kinases (RTKs; VEGFR-1, VEGFR-2, VEGFR-3, TIE-2), oncogenic RTKs (c-KIT, RET), stromal RTKs (PDGFR-B, FGFR-1), and intracellular signaling kinases (c-RAF/RAF-1, BRAF, BRAF^V600E). Preclinical studies have documented its broad-spectrum activity against different solid tumor types including CRC. Phase I studies showed that it had an acceptable safety profile in advanced refractory mCRC. A subsequent Phase III trial (CORRECT) demonstrated significant clinical efficacy of regorafenib in patients with refractory or advanced mCRC, which eventually led to its FDA approval for the treatment of mCRC in September 2012. However, the drug was associated with significant toxicity in clinical practice when administered at the approved doses, which necessitated a thorough reassessment of its dosing schedule and toxicity profile. This review summarizes the development of regorafenib from the initial preclinical studies to the Phase III trials and critically examines the current clinical space occupied by regorafenib in the treatment of mCRC, at 5 years after its initial FDA approval.

Current Molecular Targeted Therapies for Bone and Soft Tissue Sarcomas

Systemic treatment options for bone and soft tissue sarcomas remained unchanged until the 2000s. These cancers presented challenges in new drug development partly because of their rarity and heterogeneity. Many new molecular targeting drugs have been tried in the 2010s, and some were approved for bone and soft tissue sarcoma. As one of the first molecular targeted drugs approved for solid malignant tumors, imatinib's approval as a treatment for gastrointestinal stromal tumors (GISTs) has been a great achievement. Following imatinib, other tyrosine kinase inhibitors (TKIs) have been approved for GISTs such as sunitinib and regorafenib, and pazopanib was approved for non-GIST soft tissue sarcomas. Olaratumab, the monoclonal antibody that targets platelet-derived growth factor receptor (PDGFR)-α, was shown to extend the overall survival of soft tissue sarcoma patients and was approved in 2016 in the U.S. as a breakthrough therapy. For bone tumors, new drugs are limited to denosumab, a receptor activator of nuclear factor κB ligand (RANKL) inhibitor, for treating giant cell tumors of bone. In this review, we explain and summarize the current molecular targeting therapies approved and in development for bone and soft tissue sarcomas.

Mass balance, metabolic disposition, and pharmacokinetics of a single oral dose of regorafenib in healthy human subjects

Purpose

To evaluate the mass balance, metabolic disposition, and pharmacokinetics of a single dose of regorafenib in healthy volunteers. In addition, in vitro metabolism of regorafenib in human hepatocytes was investigated.

Methods

Four healthy male subjects received one 120 mg oral dose of regorafenib containing approximately 100 µCi (3.7 MBq) [¹⁴C]regorafenib. Plasma concentrations of parent drug were derived from HPLC–MS/MS analysis and total radioactivity from liquid scintillation counting (LSC). Radiocarbon analyses used HPLC with fraction collection followed by LSC for all urine samples, plasma, and fecal homogenate extracts. For the in vitro study, [¹⁴C]regorafenib was incubated with human hepatocytes and analyzed using HPLC–LSC and HPLC–HRMS/MS.

Results

Regorafenib was the major component in plasma, while metabolite M-2 (pyridine N-oxide) was the most prominent metabolite. Metabolites M-5 (demethylated pyridine N-oxide) and M-7 (N-glucuronide) were identified as minor plasma components. The mean concentration of total radioactivity in plasma/whole blood appeared to plateau at 1–4 h and again at 6–24 h post-dose. In total, 90.5% of administered radioactivity was recovered in the excreta within a collection interval of 12 days, most of which (71.2%) was eliminated in feces, while excretion via urine accounted for 19.3%. Regorafenib (47.2%) was the most prominent component in feces and was not excreted into urine. Excreted metabolites resulted from oxidative metabolism and glucuronidation.

Conclusions

Regorafenib was eliminated predominantly in feces as well as by hepatic biotransformation. The multiple biotransformation pathways of regorafenib decrease the risk of pharmacokinetic drug–drug interactions.

Electronic supplementary material

The online version of this article (10.1007/s00280-017-3480-9) contains supplementary material, which is available to authorized users.

Antitumor effects of regorafenib and sorafenib in preclinical models of hepatocellular carcinoma

The purpose of this study was to investigate the antitumor activity of regorafenib and sorafenib in preclinical models of HCC and to assess their mechanism of action by associated changes in protein expression in a HCC-PDX mouse model. Both drugs were administered orally once daily at 10 mg/kg (regorafenib) or 30 mg/kg (sorafenib), which recapitulate the human exposure at the maximally tolerated dose in mice.

In a H129 hepatoma model, survival times differed significantly between regorafenib versus vehicle (p=0.0269; median survival times 36 vs 27 days), but not between sorafenib versus vehicle (p=0.1961; 33 vs 28 days). Effects on tumor growth were assessed in 10 patient-derived HCC xenograft (HCC-PDX) models. Significant tumor growth inhibition was observed in 8/10 models with regorafenib and 7/10 with sorafenib; in four models, superior response was observed with regorafenib versus sorafenib which was deemed not to be due to lower sorafenib exposure. Bead-based multiplex western blot analysis was performed with total protein lysates from drug- and vehicle-treated HCC-PDX xenografts. Protein expression was substantially different in regorafenib- and sorafenib-treated samples compared with vehicle. The pattern of upregulated proteins was similar with both drugs and indicates an activated RAF/MEK/ERK pathway, but more proteins were downregulated with sorafenib versus regorafenib. Overall, both regorafenib and sorafenib were effective in mouse models of HCC, although several cases showed better regorafenib activity which may explain the observed efficacy of regorafenib in sorafenib-refractory patients.

A Multikinase and DNA-PK Inhibitor Combination Immunomodulates Melanomas, Suppresses Tumor Progression, and Enhances Immunotherapies

Combination therapies have the potential to improve outcomes in melanoma patients but have not yet been clinically efficacious. Here, we used high-throughput flow cytometry-based screening to identify and characterize candidate therapies that might synergize with and augment T-cell immunotherapy efficacy. Two lead therapies, regorafenib (Reg) and NU7441, were selected based on their ability to alter a variety of immunomodulatory proteins, including CD55, CD73, CD155, programmed death-ligand 1 (PD-L1), nerve growth factor receptor (NGFR), and HLA class I in a heterogeneous panel of melanomas. The therapies also upregulated several melanoma antigens, inhibited proliferation, and perturbed activation of oncogenic signaling pathways in melanomas. T cells treated with the therapies proliferated normally and exhibited a favorably altered phenotype, including increased CD25, CD28, inducible T-cell costimulator (ICOS), and reduced expression of coinhibitory receptors. Cytokine production was also increased in treated T cells. When administered in mice, REg suppressed melanoma progression in a CD8⁺ T cell-dependent manner when used alone and with various immunotherapies. Additionally, Reg altered the number, phenotype, and function of various T-cell subsets in the tumor microenvironment. These studies reveal that Reg and NU7441 influence the immunobiology of both tumor cells and T cells and enhance the efficacy of various immunotherapies. Cancer Immunol Res; 5(9); 790-803. ©2017 AACR.

Regorafenib as treatment for patients with advanced hepatocellular cancer

Hepatocellular carcinoma is one of the fastest growing causes of cancer-related mortality worldwide. Sorafenib was the first and only drug to improve survival for patients with advanced disease, and has been the cornerstone of treatment for nearly a decade. Regorafenib is a multikinase inhibitor that has recently been shown to significantly improve survival in patients who have progressed on first-line sorafenib. In this review, we discuss the pharmacokinetic and pharmacodynamics properties of regorafenib and its efficacy and tolerability in patients with advanced hepatocellular carcinoma.

Pharmacologic activity and pharmacokinetics of metabolites of regorafenib in preclinical models

Regorafenib is an orally administered inhibitor of protein kinases involved in tumor angiogenesis, oncogenesis, and maintenance of the tumor microenvironment. Phase III studies showed that regorafenib has efficacy in patients with advanced gastrointestinal stromal tumors or treatment‐refractory metastatic colorectal cancer. In clinical studies, steady‐state exposure to the M‐2 and M‐5 metabolites of regorafenib was similar to that of the parent drug; however, the contribution of these metabolites to the overall observed clinical activity of regorafenib cannot be investigated in clinical trials. Therefore, we assessed the pharmacokinetics and pharmacodynamics of regorafenib, M‐2, and M‐5 in vitro and in murine xenograft models. M‐2 and M‐5 showed similar kinase inhibition profiles and comparable potency to regorafenib in a competitive binding assay. Inhibition of key target kinases by all three compounds was confirmed in cell‐based assays. In murine xenograft models, oral regorafenib, M‐2, and M‐5 significantly inhibited tumor growth versus controls. Total peak plasma drug concentrations and exposure to M‐2 and M‐5 in mice after repeated oral dosing with regorafenib 10 mg/kg/day were comparable to those in humans. In vitro studies showed high binding of regorafenib, M‐2, and M‐5 to plasma proteins, with unbound fractions of ~0.6%, ~0.9%, and ~0.4%, respectively, in murine plasma and ~0.5%, ~0.2%, and ~0.05%, respectively, in human plasma. Estimated free plasma concentrations of regorafenib and M‐2, but not M‐5, exceeded the IC₅₀ at human and murine VEGFR2, suggesting that regorafenib and M‐2 are the primary contributors to the pharmacologic activity of regorafenib in vivo.