Phase I and Pharmacokinetic Study of XRP6258 (RPR 116258A), a Novel Taxane, Administered as a 1-Hour Infusion Every 3 Weeks in Patients with Advanced Solid Tumors

No significant impact of patient age and prior treatment profile with docetaxel on the efficacy of cabazitaxel in patient with castration-resistant prostate cancer

BACKGROUND

The correlation of the oncological outcomes of docetaxel and cabazitaxel in Japanese metastatic castration-resistant prostate cancer (mCRPC) patients has not been unclear.

MATERIALS AND METHODS

This study included a total of 47 consecutive Japanese mCRPC patients treated with cabazitaxel and assessed the prognostic significance of cabazitaxel, focusing on patient age and the correlation of efficacy between docetaxel and cabazitaxel.

RESULTS

Prostate-specific antigen (PSA) decline was observed in 27 patients (57.4%), including 19 (40.0%) achieving the response defined by PSA decline ≥ 30%. The median overall survival (OS) periods after the introduction of cabazitaxel was 16.1 months. Twenty (42.6%) were judged to have responded to cabazitaxel with a PSA decrease ≥ 30% from the baseline. A 30% PSA response to cabazitaxel was achieved in 4 (50.0%) patients with ≧ 75 years (n = 8) and 16 (41.0%) patients with less than 75 years (n = 39). There was no significant correlation between the PSA response and patients' age (p = 0.707). A 30% PSA response to cabazitaxel was achieved in 13 (46.4%) and 7 (36.8%) patients with and without that to docetaxel, respectively. A 30% PSA response to cabazitaxel was achieved in 5 (16.6%) and 7 (41.2%) patients who had treated with less than 10 cycles docetaxel or 10 ≦ cycles, respectively. Univariate and multivariate analyses revealed that there were no significant correlation of patient age (p = 0.537), the response to prior docetaxel therapy (p = 0.339) or cycles of docetaxel therapy (p = 0.379) with shorter OS.

CONCLUSION

These results indicate that the introduction of cabazitaxel for Japanese mCRPC patients could result in oncological outcomes without any association with patient's age and the profiles of previous docetaxel therapy.

Risk stratification of castration-resistant prostate cancer patients treated with cabazitaxel

Patient characteristics before administering the first cycle of cabazitaxel for metastatic castration-resistant prostate cancer (mCRPC) were collected to assess prognostic factors for overall survival (OS). Multivariate analysis revealed that prostate-specific antigen (PSA) ≥100 ng/ml prior to cabazitaxel treatment, visceral metastasis, and low absolute monocyte count were independent prognostic indicators for OS. The aim of the present study was to investigate prognostic biomarkers in patients treated with cabazitaxel among Japanese metastatic castration-resistant prostate cancer (mCRPC) patients. In this retrospective study, 45 patients with mCRPC treated with cabazitaxel were reviewed retrospectively. Clinicopathological factors and laboratory data before administering the first cycle of cabazitaxel were collected to assess the prognostic factors for overall survival (OS). Treatment was generally well tolerated, with a median of 5 cycles (range, 1-26). Median OS from the start of cabazitaxel treatment was 16.1 months (95% confidence interval 6.8-25.5). Univariate analysis revealed that poor performance status, visceral metastasis, hemoglobin <11 mg/dl, absolute monocyte count <400/µl, and prostate-specific antigen ≥100 ng/ml prior to cabazitaxel treatment (P=0.002) were significantly associated with shorter OS. Multivariate analysis revealed that PSA ≥100 ng/ml prior to cabazitaxel treatment, visceral metastasis, and absolute monocyte count <400/µl were independent prognostic indicators for OS. Based on the relative risk of death, patients with mCRPC before cabazitaxel therapy were divided into three risk groups: Low, intermediate, and high (P<0.001). In conclusion, the practical implications of our results may assist in tailoring the introduction of cabazitaxel.

Combination of cabazitaxel and plicamycin induces cell death in drug resistant B-cell acute lymphoblastic leukemia

Bone marrow microenvironment mediated downregulation of BCL6 is critical for maintaining cell quiescence and modulating therapeutic response in B-cell acute lymphoblastic leukemia (ALL). In the present study, we have performed a high throughput cell death assay using BCL6 knockdown REH ALL cell line to screen a library of FDA-approved oncology drugs. In the process, we have identified a microtubule inhibitor, cabazitaxel (CAB), and a RNA synthesis inhibitor, plicamycin (PLI) as potential anti-leukemic agents. CAB and PLI inhibited cell proliferation in not only the BCL6 knockdown REH cell line, but also six other ALL cell lines. Furthermore, combination of CAB and PLI had a synergistic effect in inhibiting proliferation in a cytarabine-resistant (REH/Ara-C) ALL cell line. Use of nanoparticles for delivery of CAB and PLI demonstrated that the combination was very effective when tested in a co-culture model that mimics the in vivo bone marrow microenvironment that typically supports ALL cell survival and migration into protective niches. Furthermore, exposure to PLI inhibited SOX2 transcription and exposure to CAB inhibited not only Mcl-1 expression but also chemotaxis in ALL cells. Taken together, our study demonstrates the utility of concomitantly targeting different critical regulatory pathways to induce cell death in drug resistant ALL cells.

Analysis of cabazitaxel-resistant mechanism in human castration-resistant prostate cancer

Cabazitaxel (CBZ) is approved for docetaxel‐resistant castration‐resistant prostate cancer (CRPC). However, efficacy of CBZ for CRPC is limited and there are no effective treatments for CBZ‐resistant CRPC. In order to investigate the CBZ‐resistant mechanism, the establishment of a CBZ‐resistant cell line is urgently needed. We established CBZ‐resistant CRPC cell lines DU145CR and PC3CR by incubating DU145 and PC3 cells with gradually increasing concentrations of CBZ for approximately 2 years. We analyzed the gene expression profiles and cell cycle changes using microarray and flow cytometry. Pathway analysis revealed DU145CR cells had enhanced gene clusters of cell division and mitotic nuclear division. Enhancement of ERK signaling was detected in DU145CR cells. DU145CR cells had resistance to G₂/M arrest induced by CBZ through ERK signaling activation. The MEK inhibitor PD184352 significantly inhibited cell proliferation of DU145CR. In contrast to DU145CR, PC3CR cells had enhancement of PI3K/AKT signaling. The PI3K/mTOR inhibitor NVP‐BEZ 235 had a significant antitumor effect in PC3CR cells. Cabazitaxel ‐resistant CRPC cells established in our laboratory had enhancement of cell cycle progression signals and resistance to G₂/M arrest induced by CBZ. Enhancement of ERK signaling or PI3K/AKT signaling were detected in the cell lines, so ERK or PI3K/AKT could be therapeutic targets for CBZ‐resistant CRPC.

Recent advances on the progressive mechanism and therapy in castration-resistant prostate cancer

Background

Although there have been great advances in mechanisms and therapeutic methods of prostate cancer, the mortality rate of prostate cancer remains high. The castration-resistant prostate cancer (CRPC), which develops from hormone-sensitive prostate cancer, foreshadows a more dismal outcome. Concomitant with the researches in the mechanism of CRPC and therapy for CRPC, more and more landmark progress has been made in recent years.

Methods

A number of clinical and experimental studies were reviewed to indicate the novel advancement in the progressive mechanism and therapy of CRPC.

Results

The androgen receptor (AR) is still a vital driver in the progression of CRPC, while other multiple mechanisms also contribute to this progression, such as tumor immunity, cancer stem cells, epithelial–mesenchymal transition and DNA repair disorder. In terms of the therapeutic methods of CRPC, chemotherapy with drugs, such as docetaxel, has been the first-line therapy for CRPC for many years. Besides, newer agents, which target some of the above mechanisms, show additional overall survival benefits for CRPC patients. These therapies include drugs targeting the androgen axis pathway (androgen synthesis, androgen receptor splice variants, coactivators of AR and so on), PI3K-AKT pathway, WNT pathway, DNA repair, rearrangement of ETS gene, novel chemotherapy and immunotherapy, bone metastasis therapy and so on. Understanding these novel findings on the mechanisms of CRPC and the latest potential CRPC therapies will direct us for further exploration of CRPC.

Conclusion

Through comprehensive consideration, the predominant mechanism of CRPC might be the AR signal axis concomitant with tumor microenvironment, stress, immunity, tumor microenvironment and so on. For CRPC therapy, targeting the AR axis pathway and chemotherapy are the first-line treatments at present. However, with the advancements in CRPC therapy made by the researchers, other novel potential methods will occupy more and more important position in the treatment of CRPC, especially the therapies targeting the tumor microenviroment, tumor immunity and DNA repair and so on.

Role of chemotherapy in prostate cancer

Chemotherapy in prostate cancer (PCa) has undergone dramatic landscape changes. While earlier studies utilized varying chemotherapy regimens which were found to be largely palliative in nature and hardly resulted in durable or meaningful responses, docetaxel resulted in the first chemotherapy agent that showed improvement in overall survival in metastatic castration-resistant prostate cancer (mCRPC). However, combination chemotherapy or any agents added to docetaxel have failed to yield incremental benefits. The improvement in overall survival as well as secondary endpoints of prostate-specific antigen (PSA) and time to recurrence when using docetaxel in the metastatic hormone-sensitive state has changed the standard of care for treatment of newly diagnosed de novo metastatic PCa. There are also promising results in locally advanced PCa and high-risk PCa in both the neoadjuvant and adjuvant settings. This review summarizes the historical as well as the more contemporary use of chemotherapeutic agents in PCa in varying states and phases of disease.

Prognostic significance of grade 3/4 neutropenia in Japanese prostate cancer patients treated with cabazitaxel

The present study aimed to evaluate the efficacy of cabazitaxel in Japanese patients affected by metastatic castration-resistant prostate cancer (mCRPC) previously treated with a docetaxel-containing regimen. In this retrospective study, 41 patients with mCRPC treated with cabazitaxel at Keio University Hospital were retrospectively reviewed. Cabazitaxel at a dose of 20-25 mg/m² was administered every 3 or 4 weeks. Clinicopathological factors and laboratory data were collected to assess the prognostic factors for overall survival (OS) and progression-free survival (PFS). An upfront dose-reduction was required in 52.5% of patients due to their reduced general condition or advanced age. Prophylactic G-CSF was prescribed to all the patients. Grade ≥3 neutropenia and febrile neutropenia occurred in 21 patients (53.6%) and 3 patients (6.8%), respectively. Treatment was generally well tolerated, with a median of 5 cycles (range 1-17). Median PFS and OS from the start of cabazitaxel treatment were 4.4 and 15.0 months (95% CI 8.9-21.2), respectively. Waterfall plot analysis revealed that a prostate-specific antigen (PSA) decline >50% was noticed in n = 11 patients receiving cabazitaxel (26.8%). Univariate analysis revealed that poor performance status, PSA ≥100 ng/mL prior to cabazitaxel treatment, visceral metastasis, absence of grade 3/4 neutropenia during cabazitaxel therapy and neutrophil-lymphocyte ratio were significantly associated with shorter overall survival. Multivariate analysis revealed that poor performance status, visceral metastasis, and the absence of grade 3/4 neutropenia during cabazitaxel therapy were the independent prognostic indicators for OS. The practical implication of our results might be to tailor cabazitaxel dosing on the basis of its hematological effects.

Prognostic and predictive clinical factors in patients with metastatic castration-resistant prostate cancer treated with cabazitaxel

INTRODUCTION

Cabazitaxel is one of several treatment options available for patients with metastatic castration-resistant prostate cancer who have progressed on docetaxel. Little is known about clinical factors that influence prognosis or treatment response for patients receiving cabazitaxel. Identifying prognostic and predictive factors could contribute to the optimal selection of patients for treatment after docetaxel.

METHODS

A retrospective review of patients enrolled on the cabazitaxel Canadian Early Access Program (C-EAP) was performed. Clinical factors were analyzed by univariable and multivariable Cox proportional hazards and logistic regression analysis to identify independent predictors of prognosis and response.

RESULTS

Forty-five patients from five centres in Canada were included in this study. On multivariable analysis, lower hemoglobin was associated with shorter survival. No other factors were independently associated with survival, prostate-specific antigen (PSA) response, or primary PSA progression.

CONCLUSIONS

Clinical factors predicting survival or treatment response were not identified for men with castration-resistant prostate cancer receiving cabazitaxel. Larger studies may be necessary to identify clinical factors and biomarkers that identify whether patients should or should not receive cabazitaxel.

A Series of Enthalpically Optimized Docetaxel Analogues Exhibiting Enhanced Antitumor Activity and Water Solubility

A dual-purpose strategy aimed at enhancing the binding affinity for microtubules and improving the water solubility of docetaxel led to the design and synthesis of a series of C-2- and C-3'-modified analogues. Both aims were realized when the C-3' phenyl group present in docetaxel was replaced with a propargyl alcohol. The resulting compound, 3f, was able to overcome drug resistance in cultured P-gp-overexpressing tumor cells and showed greater activity than docetaxel against drug-resistant A2780/AD ovarian cancer xenografts in mice. In addition, the considerably lower hydrophobicity of 3f relative to both docetaxel and paclitaxel led to better aqueous solubility. A molecular model of tubulin-bound 3f revealed novel hydrogen-bonding interactions between the propargyl alcohol and the polar environment provided by the side chains of Ser236, Glu27, and Arg320.

Establishment and characterization of two cabazitaxel-resistant prostate cancer cell lines

Once castration-resistant prostate cancer (CRPC) become resistant for cabazitaxel treatment, the patients are obliged to best supportive care. Therefore, the elucidation of the mechanism of the cabazitaxel-resistance and the conquest are important themes to improve the prognosis of the patients. Then we tried to establish cabazitaxel-resistant CRPC cell lines and characterized them. We established two cabazitaxel-resistant cell lines, PC-3-TxR/CxR and DU145-TxR/CxR from PC-3-TxR and DU145-TxR cell lines previously we established. PC-3-TxR/CxR and DU145-TxR/CxR cells became resistant for cabazitaxel by 11.8-fold and 4.4-fold, respectively. The TxR/CxR cells showed cabazitaxel-resistant using SCID mice in vivo. Although expression of multi-drug resistance gene 1 (MDR1) was up-regulated in DU145-TxR compared with DU145 cells, it was not up-regulated in DU145-TxR/CxR cells any more. In contrast, expression of MDR1 gene was up-regulated in PC-3-TxR compared with PC-3 cells and it was further up-regulated in PC-3-TxR/CxR compared with PC-3-TxR cells. Comparison of cDNA microarray between PC-3-TxR and PC-3-TxR/CxR cells or between DU145-TxR and DU145-TxR/CxR cells revealed that many genes were up-regulated or down-regulated. Finally, knockdown of MDR1 recovered the sensitivity to cabazitaxel not only in PC-3-TxR/CxR cells but also DU145-TxR/CxR cells. Together, regulation of MDR1 gene is important for conquest of the cabazitaxel-resistance.

Recent advances in microtubule-stabilizing agents

Highly dynamic mitotic spindle microtubules are superb therapeutic targets for a group of chemically diverse and clinically successful anticancer drugs. Microtubule-targeted drugs disrupt microtubule dynamics in distinct ways, and they are primarily classified into two groups: microtubule destabilizing agents (MDAs), such as vinblastine, colchicine, and combretastatin-A4, and microtubule stabilizing agents (MSAs), such as paclitaxel and epothilones. Systematic discovery and development of new MSAs have been aided by extensive research on paclitaxel, yielding a large number of promising anticancer compounds. This review focuses on the natural sources, structural features, mechanisms of action, structure-activity relationship (SAR) and chemical synthesis of MSAs. These MSAs mainly include paclitaxel, taccalonolides, epothilones, FR182877 (cyclostreptin), dictyostatin, discodermolide, eleutherobin and sarcodictyins, zampanolide, dactylolide, laulimalides, peloruside and ceratamines from natural sources, as well as small molecular microtubule stabilizers obtained via chemical synthesis. Then we discuss the application prospect and development of these anticancer compounds.

New Generation Nanomedicines Constructed from Self-Assembling Small-Molecule Prodrugs Alleviate Cancer Drug Toxicity

The therapeutic index for chemotherapeutic drugs is determined in part by systemic toxicity, so strategies for dose intensification to improve efficacy must also address tolerability. In addressing this issue, we have investigated a novel combinatorial strategy of reconstructing a drug molecule and using sequential drug-induced nanoassembly to fabricate supramolecular nanomedicines (SNM). Using cabazitaxel as a target agent, we established that individual synthetic prodrugs tethered with polyunsaturated fatty acids were capable of recapitulating self-assembly behavior independent of exogenous excipients. The resulting SNM could be further refined by PEGylation with amphiphilic copolymers suitable for preclinical studies. Among these cabazitaxel derivatives, docosahexaenoic acid-derived compound 1 retained high antiproliferative activity. SNM assembled with compound 1 displayed an unexpected enhancement of tolerability in animals along with effective therapeutic efficacy in a mouse xenograft model of human cancer, compared with free drug administered in its clinical formulation. Overall, our studies showed how attaching flexible lipid chains to a hydrophobic and highly toxic anticancer drug can convert it to a systemic self-deliverable nanotherapy, preserving its pharmacologic efficacy while improving its safety profile. Cancer Res; 77(24); 6963-74. ©2017 AACR.

Using Flash Nanoprecipitation To Produce Highly Potent and Stable Cellax Nanoparticles from Amphiphilic Polymers Derived from Carboxymethyl Cellulose, Polyethylene Glycol, and Cabazitaxel

We report the use of flash nanoprecipitation (FNP) as an efficient and scalable means of producing Cellax nanoparticles. Cellax polymeric conjugates consisting of carboxymethyl cellulose functionalized with PEG and hydrophobic anticancer drugs, such as cabazitaxel (coined Cellax-CBZ), have been shown to have high potency against several oncology targets, including prostate cancer. FNP, a robust method used to create nanoparticles through rapid mixing, has been used to encapsulate several hydrophobic drugs with block copolymer stabilizers, but has never been used to form nanoparticles from random copolymers, such as Cellax-CBZ. To assess the potential of using FNP to produce Cellax nanoparticles, parameters such as concentration, mixing rate, solvent ratios, and subsequent dilution were tested with a target nanoparticle size range of 60 nm. Under optimized solvent conditions, particles were formed that underwent a subsequent rearrangement to form nanoparticles of 60 nm diameter, independent of Cellax-CBZ polymer concentration. This intraparticle relaxation, without interparticle association, points to a delicate balance of hydrophobic/hydrophilic domains on the polymer backbone. These particles were stable over time, and the random amphiphilicity did not lead to interparticle attractions, which would compromise the stability and corresponding narrow size distribution required for parenteral injection. The amphiphilic nature of these conjugates allows them to be processed into nanoparticles for sustained drug release and improved tumor selectivity. Preferred candidates were evaluated for plasma stability and cytotoxicity against the PC3 prostate cancer cell line in vitro. These parameters are important when assessing nanoparticle safety and for estimating potential efficacy, respectively. The optimal formulations showed plasma stability profiles consistent with long circulating nanoparticles, and cytotoxicity comparable to that of free CBZ. This study demonstrates that FNP is a promising technology for development of Cellax nanoparticles.

Reactive oxygen species induction by cabazitaxel through inhibiting Sestrin-3 in castration resistant prostate cancer

Reactive oxygen species (ROS) production induced by taxanes in cancer cells may influence the taxane-induced cell death or the drug resistance. We investigated the correlation between the cytotoxic effect of taxanes and ROS production in human castration-resistant prostate cancer (CRPC) cell lines. Three human prostate cancer cell lines were treated with increasing concentrations of docetaxel or cabazitaxel in vitro. Cabazitaxel showed significantly higher cytotoxic efficacy than docetaxel in human CRPC cells, accompanied by elevated ROS production detected by FACS analysis. To investigate whether cabazitaxel-mediated cell death was caused by the ROS generation induced by cabazitaxel, we treated CRPC cells in the presence of antioxidant NAC. NAC reduced the cytotoxic effect induced by cabazitaxel. We found that ROS elimination by Sestrin-3 (SESN3) was significantly inhibited by cabazitaxel, but not by docetaxel. These results indicate higher sensitivity of human CRPC to cabazitaxel compared to docetaxel involves ROS production through inhibiting the expression of antioxidant enzyme SESN3.

Cabazitaxel in the treatment of metastatic castration-resistant prostate cancer: patient selection and special considerations

Cabazitaxel is an effective chemotherapeutic agent used in the treatment of metastatic castration-resistant prostate cancer (mCRPC) refractory to docetaxel. With the advent of new antiandrogen therapies, immune-based treatments, and radioactive-targeted therapy, there are now multiple effective and approved agents for this disease state. The optimal sequencing of these agents is unclear as there are no large-scale head-to-head comparisons. Clinicians must familiarize themselves with the most recent studies as well as drug toxicities to determine the best treatment option for their patients. In this review, we focus on the development of cabazitaxel for mCRPC, evaluate its efficacy, and highlight key strategies for toxicity management. Additionally, we summarize the studies that address cabazitaxel treatment sequencing and optimal dosing schedule.

Phase III Study Comparing a Reduced Dose of Cabazitaxel (20 mg/m2) and the Currently Approved Dose (25 mg/m2) in Postdocetaxel Patients With Metastatic Castration-Resistant Prostate Cancer-PROSELICA

Purpose Cabazitaxel 25 mg/m² (C25) significantly improved overall survival (OS) versus mitoxantrone ( P < .001) in postdocetaxel patients with metastatic castration-resistant prostate cancer (mCRPC) in the phase III TROPIC study. The phase III PROSELICA study ( ClinicalTrials.gov identifier: NCT01308580) assessed the noninferiority of cabazitaxel 20 mg/m² (C20) versus C25 in postdocetaxel patients with mCRPC. Methods Patients were stratified by Eastern Cooperative Oncology Group performance status, measurability of disease per Response Evaluation Criteria in Solid Tumors (RECIST), and region, and randomly assigned to receive C20 or C25. To claim noninferiority of C20 (maintenance of ≥ 50% of the OS benefit of C25 v mitoxantrone in TROPIC) with 95% confidence level, the upper boundary of the CI of the hazard ratio (HR) for C20 versus C25 could not exceed 1.214 under a one-sided 98.89% CI after interim analyses. Secondary end points included progression-free survival, prostate-specific antigen (PSA), tumor and pain responses and progression, health-related quality of life, and safety. Results Overall, 1,200 patients were randomly assigned (C20, n = 598; C25, n = 602). Baseline characteristics were similar in both arms. Median OS was 13.4 months for C20 and 14.5 months for C25 (HR, 1.024). The upper boundary of the HR CI was 1.184 (less than the 1.214 noninferiority margin). Significant differences were observed in favor of C25 for PSA response (C20, 29.5%; C25, 42.9%; nominal P < .001) and time to PSA progression (median: C20, 5.7 months; C25, 6.8 months; HR for C20 v C25, 1.195; 95% CI, 1.025 to 1.393). Health-related quality of life did not differ between cohorts. Rates of grade 3 or 4 treatment-emergent adverse events were 39.7% for C20 and 54.5% for C25. Conclusion The efficacy of cabazitaxel in postdocetaxel patients with mCRPC was confirmed. The noninferiority end point was met; C20 maintained ≥ 50% of the OS benefit of C25 versus mitoxantrone in TROPIC. Secondary efficacy end points favored C25. Fewer adverse events were observed with C20.

Randomised, open-label, phase II study comparing the efficacy and the safety of cabazitaxel versus weekly paclitaxel given as neoadjuvant treatment in patients with operable triple-negative or luminal B/HER2-negative breast cancer (GENEVIEVE)

BACKGROUND

The GENEVIEVE study compared the pathological complete response (pCR) rate (ypT0/is ypN0/+) in patients with operable human epidermal growth factor receptor 2 (HER2)-negative breast cancer (BC) treated with either cabazitaxel or paclitaxel.

METHODS

GENEVIEVE was a prospective, multicentre, randomised, open-label, phase II study comparing the efficacy and the safety of four 3-weekly cycles cabazitaxel versus 12 weeks of paclitaxel given as neoadjuvant treatment. Primary end-point was the pCR rate defined as the complete absence of invasive carcinoma on histological examination of the breast irrespective of lymph node involvement (ypT0/is, ypN0/+) after the taxane treatment. Patients could receive an anthracycline-based therapy thereafter.

RESULTS

Overall, 333 patients were randomised and started treatment with 74.7% and 83.2% of patients completing treatment in the cabazitaxel and paclitaxel arms, respectively. Patients in cabazitaxel arm had a significantly lower pCR rate compared to the paclitaxel arm (1.2% versus 10.8%; p = 0.001). A total of 42 (25.3%) patients in the cabazitaxel arm and 17 (10.2%) in the paclitaxel arm had at least one serious adverse event (p < 0.001). Dose reductions were observed in 9.6% patients in the cabazitaxel arm compared to 11.4% in the paclitaxel arm (p = 0.721). Main reason for dose reductions was non-haematological toxicities in 3.0% versus 7.8% (p = 0.087), respectively.

CONCLUSIONS

The GENEVIEVE study showed no short-term effect of cabazitaxel in triple-negative or luminal B/HER2-negative primary BC, while there seemed to be no differences in drug exposure and patient compliance between the two arms.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov NCT01779479.

No significant impact of prior treatment profile with docetaxel on the efficacy of cabazitaxel in Japanese patients with metastatic castration-resistant prostate cancer

The objective of this study was to retrospectively analyze the oncological outcomes of Japanese patients with metastatic castration-resistant prostate cancer (mCRPC) who received cabazitaxel. This study included a total of 63 consecutive Japanese mCRPC patients treated with cabazitaxel following the failure of docetaxel, and assessed the prognostic significance of cabazitaxel therapy in these patients focusing on the association of efficacies between two taxane agents. After treatment with cabazitaxel (median 5 cycles), prostate-specific antigen (PSA) decline was observed in 39 patients (61.9%), including 13 (27.0%) achieving the response defined by PSA decline ≥50%. The median progression-free survival (PFS) and overall survival (OS) periods after the introduction of cabazitaxel were 4.1 and 14.8 months, respectively. The response rate to cabazitaxel was not significantly different between responders and non-responders to prior docetaxel, and there was no significant correlation between the PFSs with docetaxel and cabazitaxel. Furthermore, univariate analyses of several parameters identified the performance status (PS) and clinical symptoms, but not the cycles of docetaxel therapy, total amount of administered docetaxel or objective response to docetaxel therapy, as significant predictors of OS on cabazitaxel therapy, of which only PS was independently associated with OS on multivariate analysis. These findings suggest that oncological outcomes in Japanese mCRPC patients receiving cabazitaxel are generally satisfactory, irrespective of the profiles related to prior treatment with docetaxel, and that it might be preferable to introduce cabazitaxel to mCRPC patients with a good PS to maximize the prognostic benefit of this agent.

Strategies to avoid treatment-induced lineage crisis in advanced prostate cancer

The increasing potency of therapies that target the androgen receptor (AR) signalling axis has correlated with a rise in the proportion of patients with prostate cancer harbouring an adaptive phenotype, termed treatment-induced lineage crisis. This phenotype is characterized by features that include soft-tissue metastasis and/or resistance to standard anticancer therapies. Potent anticancer treatments might force cancer cells to evolve and develop alternative cell lineages that are resistant to primary therapies, a mechanism similar to the generation of multidrug- resistant microorganisms after continued antibiotic use. Herein, we assess the hypothesis that treatment-adapted phenotypes harbour reduced AR expression and/or activity, and acquire compensatory strategies for cell survival. We highlight the striking similarities between castration-resistant prostate cancer and triple-negative breast cancer, another poorly differentiated endocrine malignancy. Alternative treatment paradigms are needed to avoid therapy-induced resistance. Herein, we present a new clinical trial strategy designed to evaluate the potential of rapid drug cycling as an approach to delay the onset of resistance and treatment-induced lineage crisis in patients with metastatic castration-resistant prostate cancer.

Phase I/II trial of cabazitaxel plus abiraterone in patients with metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel and abiraterone

Background

Abiraterone and cabazitaxel improve survival in patients with metastatic castration-resistant prostate cancer (mCRPC). We conducted an open-label phase I/II trial of cabazitaxel plus abiraterone to assess the antitumor activity and tolerability in patients with progressive mCRPC after docetaxel (phase I), and after docetaxel and abiraterone (phase II) (NCT01511536).

Patients and methods

The primary objectives were to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of cabazitaxel plus abiraterone (phase I), and the prostate-specific antigen (PSA) response defined as a ≥ 50% decrease confirmed ≥3 weeks later with this combination (phase II).

Results

Ten patients were enrolled in the phase I component; nine were evaluable. No DLTs were identified. The MTD was established as the approved doses for both drugs (cabazitaxel 25 mg/m2 every 3 weeks and abiraterone 1000 mg once daily). Daily abiraterone treatment did not impact on cabazitaxel clearance. Twenty-seven patients received cabazitaxel plus abiraterone plus prednisone (5 mg twice daily) in phase II. The median number of cycles administered (cabazitaxel) was seven (range: 1-28). Grade 3-4 treatment-emergent adverse events included asthenia (in 5 patients; 14%), neutropenia (in 5 patients; 14%) and diarrhea (in 3 patients; 8%). Nine patients (24%) required dose reductions of cabazitaxel. Of 26 evaluable patients, 12 achieved a PSA response [46%; 95% confidence interval (CI): 26.6-66.6%]. Median PSA-progression-free survival was 6.9 months (95% CI: 4.1-10.3 months). Of 14 patients with measurable disease at baseline, 3 (21%) achieved a partial response per response evaluation criteria in solid tumors.

Conclusions

The combination of cabazitaxel and abiraterone has a manageable safety profile and shows antitumor activity in patients previously treated with docetaxel and abiraterone.

Aged patients with metastatic castration resistant prostate cancer: Should we treat with chemotherapy?

Prostate cancer largely affects aged men and as life expectancy continues to increase, it is likely to be a growing burden requiring an adequate management. Aging is a heterogeneous process, thus, to assess the individual state of health when making decisions is essential. Comprehensive geriatric assessment allows a detailed evaluation of the state of health of a specific subject and can modify the therapeutic decision. It is still not commonly used because it is time consuming. Chemotherapy should be administered equally in aged well-fit patients as in the general population as per the SIOG (International society of geriatric oncology) recommendations for geriatric evaluation and treatment in prostate cancer patients. Chemotherapy with docetaxel or cabazitaxel is expected to have an efficacy and toxicity similar to younger patients and they might be considered treatment options for these patients among others. In vulnerable or frail patients, weekly or biweekly docetaxel regimens are acceptable treatment options.

Phase Ib Trial of Cabazitaxel and Tasquinimod in Men With Heavily Pretreated Metastatic Castration Resistant Prostate Cancer (mCRPC): The CATCH Trial

BACKGROUND

Tasquinimod is an immunomodulating and anti-antiangiogenic oral agent with anti-prostate cancer activity in preclinical studies and in clinical trials of men with metastatic castration resistant prostate cancer (mCRPC), including single agent activity and in combination with taxanes. We sought to identify the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of tasquinimod in combination with cabazitaxel and prednisone in men with chemorefractory mCRPC.

METHODS

Men with mCRPC who had failed prior docetaxel chemotherapy received cabazitaxel 25 mg/m² every 3 weeks with oral tasquinimod at 1 of 3 escalating dose levels (0.25, 0.5, and 1.0 mg once daily) with prednisone and PEG-filgastrim support, using a 3 + 3 dose escalation design. Treatment continued until progressive disease or unacceptable toxicity.

RESULTS

We enrolled 25 men with chemorefractory mCRPC. The RP2D was 0.5 mg tasquinimod based on excess DLTs (two of three men) observed at dose level 3 (1.0 mg) including grade 3 sensory neuropathy and grade 3 atrial fibrillation. Dose level 2 was expanded to 14 men, where 3 DLTs were observed: grade 3 fatigue, grade 4 febrile neutropenia, and grade 3 liver function abnormalities. The proportion of men with a ≥30% PSA decline was 63% and the median composite progression-free survival (PFS) was 8.5 months (95% CI 4.2-16.4 months) based on 12 PFS events. The median number of cycles of cabazitaxel was 6 (range 1-13), with six men receiving >10 cycles. Best overall RECIST responses (CR + PR) were observed in three men (12%), with stable disease in 12 (48%). No pharmacokinetic interactions were observed.

CONCLUSIONS

We determined the RP2D of tasquinimod combined with cabazitaxel to be 0.5 mg daily following a 3 week lead-in of tasquinimod 0.25 mg with growth factor support. No unexpected toxicities occurred. Prostate 77: 385-395, 2017. © 2016 Wiley Periodicals, Inc.

Safety and pharmacokinetics of cabazitaxel in patients with hepatic impairment: a phase I dose-escalation study

Purpose

Cabazitaxel has not been studied in patients with hepatic impairment (HI). This phase I study assessed cabazitaxel safety and pharmacokinetics in patients with HI.

Methods

Patients with advanced, non-hematologic cancer, and normal hepatic function (Cohort 1: C-1), or mild (C-2), moderate (C-3), severe (C-4) HI received cabazitaxel starting doses of 25, 20, 10, and 10 mg/m², respectively. Doses were escalated in patients with HI based on Cycle 1 dose-limiting toxicities (DLTs). Adverse events and the cabazitaxel pharmacokinetic profile were assessed.

Results

In C-2, three patients receiving cabazitaxel 25 mg/m² experienced DLTs; maximum tolerated dose (MTD) was 20 mg/m². In C-3, two patients receiving 20 mg/m² experienced DLTs; MTD was 15 mg/m². C-4 was discontinued early due to DLTs. The most frequent cabazitaxel-related, grade 3–4 toxicity was neutropenia (42%). Cabazitaxel clearance normalized to body surface area (CL/BSA) was lower in C-1 (geometric mean [GM] 13.4 L/h/m²) than expected (26.4 L/h/m²), but similar in C-2 (23.5 L/h/m²) and C-3 (27.9 L/h/m²). CL/BSA in C-4 was 18.1 L/h/m². Compared with C-2, CL/BSA increased 19% in C-3 (GM ratio 1.19; 90% CI 0.74–1.91), but decreased 23% in C-4 (0.77; 0.39–1.53). Cabazitaxel free fraction was unaltered. No significant correlation was found between grade 3–4 toxicities and pharmacokinetic parameters.

Conclusions

Mild–moderate HI did not cause substantial decline in cabazitaxel clearance. Cabazitaxel dose reductions in patients with mild–moderate HI, and a contraindication in patients with severe HI, are justified based on safety data.

Randomized Phase II Study of Cabazitaxel Versus Methotrexate in Patients With Recurrent and/or Metastatic Squamous Cell Carcinoma of the Head and Neck Previously Treated With Platinum-Based Therapy

LESSONS LEARNED

Cabazitaxel has activity in squamous cell carcinoma of the head and neck (SCCHN) and taxane-resistant cell lines. For the first time, cabazitaxel was investigated in incurable patients with recurrent SCCHN. Patients were randomly assigned to cabazitaxel every 3 weeks or weekly methotrexate.This phase II study did not meet its primary endpoint.Cabazitaxel has low activity in SCCHN.The toxicity profile in this population also was not favorable owing to the high rate of febrile neutropenia observed (17%).

BACKGROUND

Cabazitaxel is a second-generation taxane that improves the survival of patients with metastatic castrate-resistant prostate cancer following docetaxel therapy. Cabazitaxel has activity in squamous cell carcinoma of the head and neck (SCCHN) and taxane-resistant cell lines. In this randomized phase II trial, we investigated cabazitaxel in patients with recurrent SCCHN.

METHODS

Patients with incurable SCCHN with progression after platinum-based therapy were randomly assigned to cabazitaxel every 3 weeks (cycle 1, 20 mg/m², increased to 25 mg/m² for subsequent cycles in the absence of nonhematological adverse events [AEs] greater than grade 2 and hematological AEs greater than grade 3) or methotrexate (40 mg/m²/week). The patients were stratified according to their performance status and previous platinum-based chemotherapy for palliation versus curative intent. The primary endpoint was the progression-free survival rate (PFSR) at 18 weeks.

RESULTS

Of the 101 patients, 53 and 48, with a median age of 58.0 years (range, 41-80), were randomly assigned to cabazitaxel or methotrexate, respectively. The PFSR at 18 weeks was 13.2% (95% confidence interval [CI], 5%-25%) for cabazitaxel and 8.3% (95% CI, 2%-20%) for methotrexate. The median progression-free survival was 1.9 months in both arms. The median overall survival was 5.0 and 3.6 months for cabazitaxel and methotrexate, respectively. More patients experienced serious adverse events with cabazitaxel than with methotrexate (54% vs. 36%). The most common drug-related grade 3-4 AE in the cabazitaxel arm was febrile neutropenia (17.3%).

CONCLUSION

This study did not meet its primary endpoint. Cabazitaxel has low activity in recurrent SCCHN.

A phase I pharmacokinetic and safety study of cabazitaxel in adult cancer patients with normal and impaired renal function

PURPOSE

Limited data are available on cabazitaxel pharmacokinetics in patients with renal impairment. This open-label, multicenter study assessed cabazitaxel in patients with advanced solid tumors and normal or impaired renal function.

METHODS

Cohorts A (normal renal function: creatinine clearance [CrCL] >80 mL/min/1.73 m²), B (moderate renal impairment: CrCL 30 to <50 mL/min/1.73 m²) and C (severe impairment: CrCL <30 mL/min/1.73 m²) received cabazitaxel 25 mg/m² (A, B) or 20 mg/m² (C, could be escalated to 25 mg/m²), once every 3 weeks. Pharmacokinetic parameters and cabazitaxel unbound fraction (F _U) were assessed using linear regression and mixed models. Geometric mean (GM) and GM ratios (GMRs) were determined using mean CrCL intervals (moderate and severe renal impairment: 40 and 15 mL/min/1.73 m²) versus a control (90 mL/min/1.73 m²).

RESULTS

Overall, 25 patients received cabazitaxel (median cycles: 3 [range 1-20]; Cohort A: 5 [2-13]; Cohort B: 3 [1-15]; and Cohort C: 5 [1-20]), of which 24 were eligible for pharmacokinetic analysis (eight in each cohort). For moderate and severe renal impairment versus normal renal function, GMR estimates were: clearance normalized to body surface area (CL/BSA) 0.95 (90% CI 0.80-1.13) and 0.89 (0.61-1.32); area under the curve normalized to dose (AUC/dose) 1.06 (0.88-1.27) and 1.14 (0.76-1.71); and F _U 0.99 (0.94-1.04) and 0.97 (0.87-1.09), respectively. Estimated slopes of linear regression of log parameters versus log CrCL (renal impairment) were: CL/BSA 0.06 (-0.15 to 0.28); AUC/dose -0.07 (-0.30 to 0.16); and F _U 0.02 (-0.05 to 0.08). Cabazitaxel safety profile was consistent with previous reports.

CONCLUSIONS

Renal impairment had no clinically meaningful effect on cabazitaxel pharmacokinetics.

Cabazitaxel and indocyanine green co-delivery tumor-targeting nanoparticle for improved antitumor efficacy and minimized drug toxicity

Cabazitaxel (CBX) is an effective antineoplastic agent for the treatment of many kinds of cancers. However, the poor water solubility remains a serious deterrent to the utilization of CBX as a commercial drug. In this study, we designed a strategy that integrated CBX into albumin nanoparticles (ANs) formed with human serum albumin (HSA) to improve the water solubility and targeting ability. Meanwhile, we utilized a photothermal agent-indocyanine green (ICG), which could cooperate with CBX to enhance the antitumor effect. The obtained ANs containing ICG and CBX (AN-ICG-CBX) exhibited good mono-dispersity. In vitro cytotoxicity study showed the effectiveness of CBX and ICG, respectively, whereas AN-ICG-CBX with irradiation exhibited the most efficient antiproliferative ability (83.7%). In vivo safety evaluation studies demonstrated the safety of AN-ICG-CBX. Furthermore, the in vivo antitumor study indicated that the AN-ICG-CBX with irradiation achieved higher tumor inhibition rate (91.3%) compared with CBX-encapsulated AN (AN-CBX) (83.3%) or ICG-encapsulated AN (AN-ICG) plus irradiation (60.1%) in 4T1 tumor-bearing mice. To sum up, a safety and effective formulation AN-ICG-CBX was developed in this study and successfully reduced the drug toxicity, improved the targeting efficiency and enhanced the therapeutic effects, becoming a promising candidate for clinical application.

A multicentre phase II trial of cabazitaxel in patients with advanced non-small-cell lung cancer progressing after docetaxel-based chemotherapy

Background:

Cabazitaxel, a semisynthetic microtubule inhibitor, has shown antitumour activity in models resistant to paclitaxel and docetaxel, and it has been approved for the treatment of docetaxel-resistant prostate cancer. We investigated its activity in patients with advanced non-small-cell lung cancer (NSCLC) progressing under or after docetaxel-based regimens.

Methods:

Patients with locally advanced unresectable or metastatic NSCLC, with an Eastern Cooperative Oncology Group performance status of 0–2, were enrolled; patients had to have received up to two prior chemotherapy regimens for the treatment of advanced disease, including one docetaxel-containing regimen. Treatment consisted of cabazitaxel (25 mg m⁻² intravenously, every 21 days) until disease progression. The primary end point was the overall response rate.

Results:

Among the 46 evaluable patients, 28.3% had squamous cell carcinoma and 54.3% had adenocarcinoma. Eight (17.4%) patients had received one and 38 (82.6%) two prior chemotherapy regimens. Treatment compliance was 95% 26 (16%) cycles were delayed because of toxicity, (n=13) and dose reduction was required in 6 (13%) patients because of haematologic toxicity. Six (13%) patients achieved a partial response and 17 (37.0%) stable disease. The median progression-free survival and overall survival were 2.1 (95% confidence interval (CI): 1.0–3.2) and 7.4 (95% CI: 5.2–9.6) months, respectively. Grade 4 adverse events included neutropenia (n=8; 17%), febrile neutropenia (n=6; 13%) and thrombocytopenia (n=3; 6.5%). There was one treatment-related death.

Conclusions:

Cabazitaxel exhibits activity in NSCLC patients pre-treated with docetaxel-based chemotherapy with a substantial but manageable toxicity profile. The drug merits further evaluation in this indication.

Early investigational tubulin inhibitors as novel cancer therapeutics

INTRODUCTION

Microtubules represent one of the most logical and strategic molecular targets amongst the current targets for chemotherapy, alongside DNA. In the past decade, tubulin inhibitors as cancer therapeutics have been an area of focus due to the improved understanding and biological relevance of microtubules in cellular functions. Fueled by the objective of developing novel chemotherapeutics and with the aim of establishing the benefits of tubulin inhibition, several clinical trials have been conducted with others ongoing.

AREA COVERED

At present, the antitubulin development pipeline contains an armful of agents under clinical investigation. This review focuses on novel tubulin inhibitors as cancer therapeutics. The article covers the agents which have completed the phase II studies along with the agents demonstrating promising results in phase I studies.

EXPERT OPINION

Countless clinical trials evaluating the efficacy, safety and pharmacokinetics of novel tubulin inhibitors highlights the scientific efforts being paid to establish their candidature as cancer therapeutics. Colchicine binding site inhibitors as vascular disrupting agents (VDAs) and new taxanes appear to be the most likely agents for future clinical interest. Numerous agents have demonstrated clinical benefits in terms of efficacy and survival in phase I and II studies. However conclusive benefits can only be ascertained on the basis of phase III studies.

Cabazitaxel Versus Topotecan in Patients with Small-Cell Lung Cancer with Progressive Disease During or After First-Line Platinum-Based Chemotherapy

INTRODUCTION

Patients with small-cell lung cancer (SCLC) typically respond well to initial chemotherapy. However, relapse invariably occurs, and topotecan, the only approved second-line treatment option, has limited efficacy. Taxanes have activity in SCLC, and cabazitaxel is a second-generation taxane with potential for enhanced activity in chemorefractory malignancies.

METHODS

Patients with SCLC who relapsed after initial platinum-based chemotherapy were randomly assigned to receive cabazitaxel 25 mg/m every 21 days or topotecan 1.5 mg/m on days 1-5 every 21 days. Two patient subgroups, defined by chemosensitive and chemo-resistant/refractory disease, were assessed in combination and separately.

RESULTS

The safety profile of cabazitaxel and topotecan was consistent with previous studies, and despite considerable toxicity in both arms, no new safety concerns were identified. Patients receiving cabazitaxel had inferior progression-free survival compared with topotecan (1.4 versus 3.0 months, respectively; two-sided p < 0.0001; hazard ratio = 2.17, 95% confidence interval = 1.563-3.010), and results were similar in both the chemosensitive and chemorefractory subgroups. No complete responses were observed in either arm, and no partial responses were observed in the cabazitaxel group. The partial response rate in the topotecan arm was 10%. Median overall survival was 5.2 months in the cabazitaxel arm and 6.8 months in the topotecan arm (two-sided p = 0.0125; hazard ratio = 1.57, 95% confidence interval = 1.10-2.25).

CONCLUSION

Cabazitaxel, a next-generation taxane, had inferior efficacy when compared with standard-dose topotecan in the treatment of relapsed SCLC. Topotecan remains a suboptimal therapy, and continued efforts to develop improved second-line treatments are warranted.

SNPs associated with activity and toxicity of cabazitaxel in patients with advanced urothelial cell carcinoma

AIM

We aimed to identify SNPs associated with cabazitaxel toxicity and response within a Phase II clinical trial using this compound in advanced transitional cell carcinoma after progression to a platinum-based regimen.

PATIENTS & METHODS

Eleven SNPs in CYP3A4, CYP3A5, CYP2C8, ABCB1 and TUBB1 were genotyped in 45 patients.

RESULTS

CYP3A5 rs776746 A allele was associated with protection against gastrointestinal toxicity (odds ratio: 0.06, 95% CI: 0.007-0.63, p = 0.018) and with reduced progression-free survival (hazard ratio: 5.1, 95% CI: 1.7-15.1, p = 0.0038, multivariable analysis). ABCB1 SNPs were associated with total number of grade 3-4 toxicity events (p-values of 0.009, 0.041 and 0.043, respectively).

CONCLUSION

Polymorphisms in CYP3A5 and ABCB1 may define a subset of patients with different cabazitaxel toxicity and efficacy and therefore could be used as markers for treatment optimization.

Skeletal metastases and impact of anticancer and bone-targeted agents in patients with castration-resistant prostate cancer

Incidence of bone metastases is very high in advanced prostate cancer patients. Bone metastases likely have a significant impact on functional status and quality of life, not only related to pain, but also to the relevant risk of skeletal-related events. A better understanding of mechanisms associated with bone metastatic disease secondary to prostate cancer and more specifically to the cross-talk between tumor cells and bone microenvironment in metastatic progression represented the background for the development of new effective bone-targeted therapies. Furthermore, a better knowledge of biological mechanisms driving disease progression led to significant advances in the treatment of castration-resistant prostate cancer, with the development and approval of new effective drugs. Aim of this review is to outline the physiopathology of bone metastases in prostate cancer and summarize the main results of clinical trials conducted with different drugs to control morbidity induced by skeletal metastases and bone disease progression. For each agent, therapeutic effect on bone metastases has been measured in terms of pain control and/or incidence of skeletal-related events, usually defined as a composite endpoint, including the need for local treatment (radiation therapy or surgery), spinal cord compression, pathological bone fractures. In details, data obtained with chemotherapy (mitoxantrone, docetaxel, cabazitaxel), new generation hormonal agents (abiraterone, enzalutamide), radium-223, bone-targeted agents (zoledronic acid, denosumab) and with several experimental agents (cabozantinib, dasatinib, anti-endothelin and other agents) in patients with castration-resistant prostate cancer are reviewed.

Taxane anticancer agents: a patent perspective

INTRODUCTION

Paclitaxel and docetaxel were two epoch-making anticancer drugs and have been successfully used in chemotherapy for a variety of cancer types. In the year 2010, a new taxane, cabazitaxel, was approved by FDA for use in combination with prednisone for the treatment of metastatic hormone-refractory prostate cancer. Albumin-bound paclitaxel (nab™-paclitaxel; abraxane) nanodroplet formulation was another notable invention (FDA approval 2005 for refractory, metastatic, or relapsed breast cancer). Abraxane in combination with gemcitabine for the treatment of pancreatic cancer was approved by FDA in 2013. Accordingly, there have been a huge number of patent applications dealing with taxane anticancer agents in the last 5 years. Thus, it is a good time to review the progress in this area and find the next wave for new developments.

AREA COVERED

This review covers the patent literature from the year 2010 to early 2015 on various aspects of taxane-based chemotherapies and drug developments.

EXPERT OPINION

Three FDA-approved taxane anticancer drugs will continue to expand their therapeutic applications, especially through drug combinations and new formulations. Inspired by the success of abraxane, new nano-formulations are emerging. Highly potent new-generation taxanes will play a key role in the development of efficacious tumor-targeted drug delivery systems.

Treatment regimens of classical and newer taxanes

The classical taxanes (paclitaxel, docetaxel), the newer taxane cabazitaxel and the nanoparticle-bound nab-paclitaxel are among the most widely used anticancer drugs. The taxanes share the characteristics of extensive hepatic metabolism and biliary excretion, the need for dose adaptation in patients with liver dysfunction, and a substantial pharmacokinetic variability even after taking into account known covariates. Data from clinical studies suggest that optimal scheduling of the taxanes is dependent not only on the specific taxane compound, but also on the tumor type and line of treatment. Still, the optimal dosing regimen (weekly vs 3 weekly) and optimal dose of the taxanes are controversial, as is the value of pharmacological personalization of taxane dosing. In this article, an overview is given on the pharmacological properties of the taxanes, including metabolism, pharmacokinetics-pharmacodynamics and aspects in the clinical use of taxanes. The latter includes the ongoing debate on the most active and safe regimen, the recommended initial dose and the issue of therapeutic drug dosing.

Current and future targeted therapies for non-small-cell lung cancers with aberrant EGF receptors

Expression of the EGF receptors (EGFRs) is abnormally high in many types of cancer, including 25% of lung cancers. Successful treatments target mutations in the EGFR tyrosine kinase domain with EGFR tyrosine kinase inhibitors (TKIs). However, almost all patients develop resistance to this treatment, and acquired resistance to first-generation TKI has prompted the clinical development of a second generation of EGFR TKI. Because of the development of resistance to treatment of TKIs, there is a need to collect genomic information about EGFR levels in non-small-cell lung cancer patients. Herein, we focus on current molecular targets that have therapies available as well as other targets for which therapies will be available in the near future.

Phase I dose-escalation study of cabazitaxel administered in combination with gemcitabine in patients with metastatic or unresectable advanced solid malignancies

Supplemental Digital Content is available in the text.

Taxane–gemcitabine combinations have demonstrated antitumor activity. This phase I study (NCT01001221) aimed to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of cabazitaxel plus gemcitabine and to assess the preliminary efficacy of this combination. The patients included had metastatic or unresectable solid tumors and had exhausted standard treatment. Cohorts of three to six patients received cabazitaxel (15–20 mg/m²) before (part 1a) or after (part 1b) gemcitabine (700–1000 mg/m²) on Day 1 and gemcitabine alone on Day 8. Prophylactic growth factors were not allowed in cycle 1. In part 1a (n=12), five patients received 20 mg/m² cabazitaxel plus 1000 mg/m² gemcitabine (20/1000), five received 15/900, two received 15/700. In part 1b, all six patients received the lowest dose (700/15). At all doses, two or more patients experienced a DLT, regardless of administration sequence, including febrile neutropenia (n=4), grade 4 neutropenia (n=2), grade 4 thrombocytopenia (n=2), and grade 3 aspartate transaminase increase (n=1). The MTD was not established as all cohorts exceeded the MTD by definition. All patients experienced an adverse event; the most frequent all-grade nonhematologic events were fatigue (66.7%), decreased appetite (50.0%), and diarrhea (44.4%). The most frequent grade 3–4 hematologic abnormalities were neutropenia (83.3%), leukopenia (77.8%), and lymphopenia (72.2%). Toxicity was sequence-independent but appeared worse with gemcitabine followed by cabazitaxel. Durable partial responses were observed in three patients (prostate cancer, appendiceal cancer, and melanoma). The unacceptable DLTs with cabazitaxel plus gemcitabine, at doses reduced more than 25% from single-agent doses, preclude further investigation.

A phase I open-label study investigating the disposition of [14C]-cabazitaxel in patients with advanced solid tumors

Cabazitaxel is a semisynthetic taxane approved for the treatment of patients with hormone-refractory metastatic prostate cancer (now known as metastatic castration-resistant prostate cancer) treated previously with a docetaxel-containing treatment regimen. The human plasma pharmacokinetics of cabazitaxel have been described previously, but detailed analyses of the metabolism and excretion pathways of cabazitaxel have not yet been published. Metabolite profiling, quantification, and identification as well as excretion analyses were carried out on samples from patients with advanced solid tumors who received an intravenous infusion of 25 mg/m [C]-cabazitaxel (50 μCi, 1.85 MBq) over 1 h. In plasma, cabazitaxel was the main circulating compound. Seven metabolites were detected, but with each accounting for 5% or less of the parent drug exposure, none were considered relevant metabolites. In excreta, 76.0% of the administered dose was recovered in feces within 2 weeks and 3.7% of the dose was excreted in urine within 1 week. Approximately 20 metabolites were detected in excreta; the main metabolites corresponded to combined mono-O-demethyl or di-O-demethyl derivatives on the taxane ring, with hydroxyl or cyclized derivatives on the lateral chain. Docetaxel (di-O-demethyl-cabazitaxel) was only detected at trace levels in excreta. These results suggest an extensive hepatic metabolism and biliary excretion of cabazitaxel in humans.

Initial testing (stage 1) of the anti-microtubule agents cabazitaxel and docetaxel, by the pediatric preclinical testing program

BACKGROUND

Although microtubule-destabilizing agents (principally vincristine) are in common use in pediatric oncology, the microtubule-stabilizing taxanes are uncommonly used to treat childhood cancers. Cabazitaxel has been reported to have activity superior to that of docetaxel in preclinical models of multidrug-resistant adult cancers, and it was active in patients who had progressed on or after docetaxel. The PPTP conducted a comparison of these two agents against the PPTP in vitro panel and against a limited panel of solid tumor xenografts.

PROCEDURES

Cabazitaxel and docetaxel were tested against the PPTP in vitro cell line panel at concentrations from 0.01 to 0.1 μM and in vivo against a subset of the PPTP solid tumor xenograft models at a dose of 10 or 7.5 mg/kg on an every 4 days × 3 I.V. schedule.

RESULTS

In vitro, both cabazitaxel and docetaxel had similar potency (median rIC50 0.47 nM and 0.88 nM, respectively) and a similar activity profile, with Ewing sarcoma cells being significantly more sensitive to both agents. In vitro sensitivity to docetaxel inversely correlated with mRNA expression for ABCB1, but the correlation with ABCB1 expression was weaker for cabazitaxel. In vivo cabazitaxel demonstrated significantly greater activity than docetaxel in five of 12 tumor models, inducing regressions in six models compared with three models for docetaxel.

CONCLUSIONS

Cabazitaxel demonstrated superior activity compared to docetaxel. The lower cabazitaxel systemic exposure tolerated in humans compared to mice needs to be considered when extrapolating these results to the clinical setting.

The Emerging Role of Extracellular Vesicle-Mediated Drug Resistance in Cancers: Implications in Advanced Prostate Cancer

Emerging evidence has shown that the extracellular vesicles (EVs) regulate various biological processes and can control cell proliferation and survival, as well as being involved in normal cell development and diseases such as cancers. In cancer treatment, development of acquired drug resistance phenotype is a serious issue. Recently it has been shown that the presence of multidrug resistance proteins such as Pgp-1 and enrichment of the lipid ceramide in EVs could have a role in mediating drug resistance. EVs could also mediate multidrug resistance through uptake of drugs in vesicles and thus limit the bioavailability of drugs to treat cancer cells. In this review, we discussed the emerging evidence of the role EVs play in mediating drug resistance in cancers and in particular the role of EVs mediating drug resistance in advanced prostate cancer. The role of EV-associated multidrug resistance proteins, miRNA, mRNA, and lipid as well as the potential interaction(s) among these factors was probed. Lastly, we provide an overview of the current available treatments for advanced prostate cancer, considering where EVs may mediate the development of resistance against these drugs.

Metastatic castration-resistant prostate cancer: time for innovation

Androgen deprivation is the mainstay of advanced prostate cancer treatment. Despite initial responses, almost all patients progress to castration-resistant prostate cancer (CRPC). The understanding of the biology of CRPC and the evidence that CRPC still remains driven by androgen receptor signaling led to the discovery of new therapeutic targets. In the last few years, large Phase III trials showed improvements in survival and outcomes and led to the approval of a CYP17 inhibitor (abiraterone), an androgen receptor antagonist (enzalutamide), the taxane cabazitaxel, an α-emitter (radium-223), the bone resorption-targeting drug denosumab and an immunotherapy (sipuleucel-T). This article describes the molecular mechanisms underlying castration resistance, discusses recent and ongoing trials and offers some insights into identifying the best sequence of new drugs.

P-glycoprotein, CYP3A, and Plasma Carboxylesterase Determine Brain Disposition and Oral Availability of the Novel Taxane Cabazitaxel (Jevtana) in Mice

We aimed to clarify the roles of the multidrug-detoxifying proteins ABCB1, ABCG2, ABCC2, and CYP3A in oral availability and brain accumulation of cabazitaxel, a taxane developed for improved therapy of docetaxel-resistant prostate cancer. Cabazitaxel pharmacokinetics were studied in Abcb1a/1b, Abcg2, Abcc2, Cyp3a, and combination knockout mice. We found that human ABCB1, but not ABCG2, transported cabazitaxel in vitro. Upon oral cabazitaxel administration, total plasma levels were greatly increased due to binding to plasma carboxylesterase Ces1c, which is highly upregulated in several knockout strains. Ces1c inhibition and in vivo hepatic Ces1c knockdown reversed these effects. Correcting for Ces1c effects, Abcb1a/1b, Abcg2, and Abcc2 did not restrict cabazitaxel oral availability, whereas Abcb1a/1b, but not Abcg2, dramatically reduced cabazitaxel brain accumulation (>10-fold). Coadministration of the ABCB1 inhibitor elacridar completely reversed this brain accumulation effect. After correction for Ces1c effects, Cyp3a knockout mice demonstrated a strong (six-fold) increase in cabazitaxel oral availability, which was completely reversed by transgenic human CYP3A4 in intestine and liver. Cabazitaxel markedly inhibited mouse Ces1c, but human CES1 and CES2 only weakly. Ces1c upregulation can thus complicate preclinical cabazitaxel studies. In summary, ABCB1 limits cabazitaxel brain accumulation and therefore potentially therapeutic efficacy against (micro)metastases or primary tumors positioned wholly or partly behind a functional blood-brain barrier. This can be reversed with elacridar coadministration, and similar effects may apply to ABCB1-expressing tumors. CYP3A4 profoundly reduces the oral availability of cabazitaxel. This may potentially be greatly improved by coadministering ritonavir or other CYP3A inhibitors, suggesting the option of patient-friendly oral cabazitaxel therapy.

Gene interference strategies as a new tool for the treatment of prostate cancer

Prostate cancer (PCa) is one of the most common cancer in men. It affects older men and the incidence increases with age; the median age at diagnosis is 67 years. The diagnosis of PCa is essentially based on three tools: digital rectal exam, serum concentration of prostate specific antigen, and transrectal ultrasound-guided biopsy. Currently, the therapeutic treatments of this cancer are different and range from the prostatectomy to hormonal therapy, to radiation therapy, to immunotherapy, and to chemotherapy. However, additional efforts are required in order to find new weapons for the treatment of metastatic setting of disease. The purpose of this review is to highlight new therapeutic strategies based on gene interference; in fact, numerous siRNA and miRNA in the therapeutic treatment of PCa are reported below.