A phase II study of ixabepilone (BMS-247550) in metastatic renal-cell carcinoma

A Phase II Multi-Center Study of Bevacizumab in Combination with Ixabepilone in Subjects with Advanced Renal Cell Carcinoma

Lessons Learned.

Accrual to renal cell carcinoma trials remains a challenge despite the lack of prolonged response to the available treatments.

The observation of three responses among the 30 patients with median progression‐free survival and overall survival of 8.3 and 15 months, respectively, indicates the combination has some activity, but it is not sufficient for further development.

Background.

Treatment of metastatic renal cell carcinoma (mRCC) remains suboptimal. Preclinical data have previously shown that ixabepilone, a microtubule‐stabilizing agent approved for the treatment of breast cancer, is active in taxane‐sensitive and ‐resistant cells. In this single‐arm phase II trial, we investigated a combination of ixabepilone plus bevacizumab in patients with refractory mRCC.

Methods.

We enrolled 30 patients with histologically confirmed mRCC, clear cell subtype, who had not been previously treated with ixabepilone or bevacizumab but had received at least one prior U.S. Food and Drug Administration (FDA)‐approved treatment for renal cell carcinoma (RCC). The treatment regimen consisted of 6 mg/m² ixabepilone per day for 5 days and 15 mg/kg bevacizumab every 21 days. After 6 cycles, the treatment interval could be extended to every 28 days. The primary endpoint was the objective response rate according to the Response Evaluation Criteria in Solid Tumors (RECIST). Secondary endpoints were progression‐free survival (PFS), overall survival (OS), and the toxicity of the combination.

Results.

The median number of prior therapies was two (range per patient one to five). Patients received a median of 8 cycles of ixabepilone plus bevacizumab (range 2–54). The median follow‐up was 36.4 months (range 23.5–96.5). Nineteen patients (63.3%) had stable disease as a best response. Three patients (10%) had a partial response. The median PFS was 8.3 months (95% confidence interval [CI], 4.9–10.6) and the median OS was 15.0 months (95% CI, 11.3–28.8). The total number of cycle for safety evaluation was 289. Grade 3/4 adverse events (>5% incidence) included lymphopenia (16.7%), hypertension (6.7%), and leukopenia (6.7%).

Conclusion.

The combination of ixabepilone and bevacizumab was well tolerated, with modest activity in second ‐ or later‐line mRCC, but it is not recommended as a therapy without further clinical development. Alternative combinations with these agents could be explored in future studies.

Flow induces epithelial-mesenchymal transition, cellular heterogeneity and biomarker modulation in 3D ovarian cancer nodules

Seventy-five percent of patients with epithelial ovarian cancer present with advanced-stage disease that is extensively disseminated intraperitoneally and prognosticates the poorest outcomes. Primarily metastatic within the abdominal cavity, ovarian carcinomas initially spread to adjacent organs by direct extension and then disseminate via the transcoelomic route to distant sites. Natural fluidic streams of malignant ascites triggered by physiological factors, including gravity and negative subdiaphragmatic pressure, carry metastatic cells throughout the peritoneum. We investigated the role of fluidic forces as modulators of metastatic cancer biology in a customizable microfluidic platform using 3D ovarian cancer nodules. Changes in the morphological, genetic, and protein profiles of biomarkers associated with aggressive disease were evaluated in the 3D cultures grown under controlled and continuous laminar flow. A modulation of biomarker expression and tumor morphology consistent with increased epithelial-mesenchymal transition, a critical step in metastatic progression and an indicator of aggressive disease, is observed because of hydrodynamic forces. The increase in epithelial-mesenchymal transition is driven in part by a posttranslational up-regulation of epidermal growth factor receptor (EGFR) expression and activation, which is associated with the worst prognosis in ovarian cancer. A flow-induced, transcriptionally regulated decrease in E-cadherin protein expression and a simultaneous increase in vimentin is observed, indicating increased metastatic potential. These findings demonstrate that fluidic streams induce a motile and aggressive tumor phenotype. The microfluidic platform developed here potentially provides a flow-informed framework complementary to conventional mechanism-based therapeutic strategies, with broad applicability to other lethal malignancies.

Phase I clinical, pharmacokinetic, and pharmacodynamic study of KOS-862 (Epothilone D) in patients with advanced solid tumors and lymphoma

PURPOSE

To determine the maximum tolerated dose and safety of the epothilone, KOS-862, in patients with advanced solid tumors or lymphoma.

PATIENTS AND METHODS

Patients were treated weekly for 3 out of 4 weeks (Schedule A) or 2 out of 3 weeks (Schedule B) with KOS-862 (16-120 mg/m(2)). Pharmacokinetic (PK) sampling was performed during cycles 1 and 2; pharmacodynamic (PD) assessment for microtubule bundle formation (MTBF) was performed after the 1st dose, only at or above 100 mg/m(2).

RESULTS

Thirty-two patients were enrolled, and twenty-nine completed ≥1 cycle of therapy. Dose limiting toxicity [DLT] was observed at 120 mg/m(2). PK data were linear from 16 to 100 mg/m(2), with proportional increases in mean C(max) and AUC(tot) as a function of dose. Full PK analysis (mean ± SD) at 100 mg/m(2) revealed the following: half-life (t (½)) = 9.1 ± 2.2 h; volume of distribution (V(z)) = 119 ± 41 L/m(2); clearance (CL) = 9.3 ± 3.2 L/h/m(2). MTBF (n = 9) was seen in 40% of PBMCs within 1 h and in 15% of PBMC at 24-hours post infusion at 100 mg/m(2). Tumor shrinkage (n = 2, lymphoma), stable disease >3 months (n = 5, renal, prostate, oropharynx, cholangiocarcinoma, and Hodgkin lymphoma), and tumor marker reductions (n = 1, colorectal cancer/CEA) were observed.

CONCLUSION

KOS-862 was well tolerated with manageable toxicity, favorable PK profile, and the suggestion of clinical activity. The maximum tolerated dose was determined to be 100 mg/m(2) weekly 3-on/1-off. MTBF can be demonstrated in PBMCs of patients exposed to KOS-862.

Novel therapies for metastatic renal cell carcinoma: efforts to expand beyond the VEGF/mTOR signaling paradigm

With six agents approved for metastatic renal cell carcinoma (mRCC) within the past 5 years, there has undoubtedly been progress in treating this disease. However, the goal of cure remains elusive, and the agents nearest approval (i.e., axitinib and tivozanib) abide by the same paradigm as existing drugs (i.e., inhibition of VEGF or mTOR signaling). The current review will focus on investigational agents that diverge from this paradigm. Specifically, novel immunotherapeutic strategies will be discussed, including vaccine therapy, cytotoxic T-lymphocyte antigen 4 (CTLA4) blockade, and programmed death-1 (PD-1) inhibition, as well as novel approaches to angiogenesis inhibition, such as abrogation of Ang/Tie-2 signaling. Pharmacologic strategies to block other potentially relevant signaling pathways, such as fibroblast growth factor receptor or MET inhibition, are also in various stages of development. Although VEGF and mTOR inhibition have dramatically improved outcomes for patients with mRCCs, a surge above the current plateau with these agents will likely require exploring new avenues.

A phase II clinical trial of ixabepilone (Ixempra; BMS-247550; NSC 710428), an epothilone B analog, in patients with metastatic renal cell carcinoma

PURPOSE

Ixabepilone (Ixempra; BMS-247550) is an epothilone B analog and nontaxane microtubule-stabilizing compound with clinical activity in a range of solid tumors. This phase II study was conducted to assess the efficacy and safety of ixabepilone in patients with metastatic renal cell carcinoma.

EXPERIMENTAL DESIGN

Patients with metastatic renal cell carcinoma who had measurable disease and had not received previous cytotoxic or targeted therapy were treated with 6 mg/m(2) ixabepilone i.v. daily for 5 days every 3 weeks. Levels of Glu-terminated and acetylated tubulin, markers of microtubule stabilization, were assessed by Western blot. VHL gene mutation status was determined by sequencing.

RESULTS

Eighty-seven patients received a total of 590 cycles, with a median of 5 cycles (range, 1-29). The overall response rate was 13% (Response Evaluation Criteria in Solid Tumor). One patient had a complete response, 10 patients had partial responses, and 59 patients had stable disease. The median duration of response was 5.5 months. The median overall survival of renal cell carcinoma Motzer grade 0 and 1 patients with clear cell histology was 19.25 months. Treatment-related adverse events were primarily alopecia, gastrointestinal toxicity, neuropathy, and fatigue. Biopsies were done at baseline and after five doses of ixabepilone. Microtubule target engagement was achieved in 84.6% to 92.3% of patients evaluated. No correlation was identified between the target engagement, VHL gene mutation status, and clinical response.

CONCLUSION

Ixabepilone can cause tumor regression in some patients with metastatic renal cell carcinoma and could be considered in combination regimens with other therapies.

A phase II trial of the epothilone B analog ixabepilone (BMS-247550) in patients with metastatic melanoma

Background

Ixabepilone (BMS-247550), an epothilone B analog, is a microtubule stabilizing agent which has shown activity in several different tumor types and preclinical models in melanoma. In an open label, one-arm, multi-center phase II trial the efficacy and toxicity of this epothilone was investigated in two different cohorts: chemotherapy-naïve (previously untreated) and previously treated patients with metastatic melanoma.

Methodology/Principal Findings

Eligible patients had histologically-confirmed stage IV melanoma, with an ECOG performance status of 0 to 2. Ixabepilone was administered at a dose of 20 mg/m² on days 1, 8, and 15 during each 28-day cycle. The primary endpoint was response rate (RR); secondary endpoints were time to progression (TTP) and toxicity. Twenty-four patients were enrolled and 23 were evaluable for response. Initial serum lactate dehydrogenase (LDH) levels were elevated in 6/11 (55%) of the previously treated and in 5/13 (38%) of the previously untreated patients. No complete or partial responses were seen in either cohort. One patient in the previously treated group developed neutropenia and fatal septic shock. Seventeen patients (8 in the previously untreated group and 9 in the previously treated group) progressed after 2 cycles, whereas six patients (3 in each group) had stable disease after 2–6 cycles. Median TTP was 1.74 months in the previously untreated group (95% CI = 1.51 months, upper limit not estimated) and 1.54 months in the previously treated group (95% CI = 1.15 months, 2.72 months). Grade 3 and/or 4 toxicities occurred in 5/11 (45%) of previously untreated and in 5/13 (38%) of previously treated patients and included neutropenia, peripheral neuropathy, fatigue, diarrhea, and dyspnea.

Conclusions/Significance

Ixabepilone has no meaningful activity in either chemotherapy-naïve (previously untreated) or previously treated patients with metastatic melanoma. Further investigation with ixabepilone as single agent in the treatment of melanoma is not warranted.

Trial registration

Clinical Trials.gov NCT00036764

The epothilones: how pharmacology relates to clinical utility

OBJECTIVE

To review the pharmacologic properties of a novel class of chemotherapeutic agents, the epothilones, and to summarize findings from recent clinical trials investigating the various epothilones in cancer therapy.

DATA SOURCES

Literature searches were conducted using MEDLINE, PubMed, and the abstract search engines for the American Society of Clinical Oncology and American Association for Cancer Research annual meetings (all searches through November 2008). Primary search terms included epothilone, BMS-247550, ixabepilone, EPO906, patupilone, sagopilone, and ZK-EPO.

STUDY SELECTION AND DATA EXTRACTION

Publications were given priority for inclusion if they discussed structural or pharmacologic properties of the epothilones as a class or if they included preclinical or clinical data for epothilones currently in clinical development.

DATA SYNTHESIS

The epothilones are a novel class of microtubule-stabilizing agents (MSAs). Epothilones are structurally and pharmacologically distinct from taxanes, but the exact ways in which the pharmacophores of the 2 classes differ has not been firmly established. A number of natural, semisynthetic, and fully synthetic epothilones are in various stages of clinical development. These agents differ from each other and from existing MSAs; these differences influence potency, stability, and solubility. Ixabepilone is currently approved to treat multidrug-resistant metastatic breast cancer and has demonstrated efficacy in earlier stages of breast cancer and in several other tumor types. Patupilone and sagopilone are currently under clinical investigation and have each shown promise in a number of treatment settings and tumor types. All 3 agents appear to be associated with manageable toxicities, but no class-wide toxicity profile exists for the epothilones and dose-limiting toxicities differ among the agents.

CONCLUSIONS

The epothilones have demonstrated significant potential for addressing the growing therapeutic challenge of taxane resistance, and the ever-increasing pool of information regarding structure-activity relationships of these MSAs will help to optimize microtubule-targeted chemotherapy.

Activity of ixabepilone in patients with metastatic breast cancer with primary resistance to taxanes

Primary drug resistance, defined as disease progression as best response to treatment, presents an important problem in everyday clinical practice. Primary taxane resistance, reported in up to 55% of patients with breast cancer, plays a critical role in minimizing the efficacy of taxane-based chemotherapy for metastatic breast cancer (MBC). The epothilones are a novel class of antineoplastic agents, developed to overcome tumor-resistance mechanisms. Ixabepilone, the first drug in this class, stabilizes microtubule polymerization, and induces cell-cycle arrest and apoptosis. Ixabepilone demonstrates low susceptibility to different and multiple mechanisms of drug resistance that play a crucial role in primary taxane resistance, such as tumor overexpression of neuronal-specific beta-tubulin isotype III and drug-efflux transporters. In phase II trials, ixabepilone demonstrated proven activity in patients with MBC whose tumors had primary or secondary resistance to taxanes and other agents. Ixabepilone also demonstrated activity in patients with tumor types such as renal-cell cancer and pancreatic cancer that are usually intrinsically insensitive to chemotherapy, including taxanes. To determine the activity of ixabepilone in patients with primary taxane resistance, a retrospective analysis of patient subsets from 2 clinical trials was conducted. Ixabepilone demonstrated clinical activity as monotherapy, and in combination with capecitabine, in patients with MBC who had disease progression as best response to previous taxane therapy. Response rates in patients with primary taxane resistance were comparable to responses observed in total patient populations. The clinical results support the hypothesis that ixabepilone can overcome or circumvent primary mechanisms of resistance to taxanes and other chemotherapeutic agents.

Novel microtubule-targeting agents - the epothilones

Epothilones are a new class of antimicrotubule agents currently in clinical trials. Their chemical structures are distinct from taxanes and are more amenable to synthetic modification. Six epothilones have been studied in preclinical and clinical trials: patupilone (epothilone B), ixabepilone (BMS247550), BMS 310705, sagopilone (ZK-EPO), KOS-862 (epothilone D), and KOS-1584. In vitro data have shown increased potency in taxane-sensitive and taxane-resistant cancer cell lines. This enhanced cytotoxic effect has been attributed to epothilone being a poor substrate for p-glycoprotein drug resistance protein and having high affinity to the various beta tubulin isoforms. Phase I clinical data have shown different dose-limiting toxicities for each of the epothilones. These effects are drug specific, dose specific, and schedule of administration specific. While diarrhea and myelosuppression are the dose-limiting toxicities for patupilone and BMS 310705, respectively, neurologic toxicity, as seen with taxanes, is the dose-limiting toxicity of ixabepilone, sagopilone, and KOS-862. In an effort to decrease neurologic toxicity, investigators have modified dosing schedules with limited success. Ixabepilone has the most mature clinical results with published phase II and III data, and regulatory approval for clinical use in the treatment of breast cancer. Ixabepilone has also been combined with other anticancer agents and has regulatory approval in combination with capecitabine for heavily treated breast cancer.

Improved cellular pharmacokinetics and pharmacodynamics underlie the wide anticancer activity of sagopilone

Sagopilone (ZK-EPO) is the first fully synthetic epothilone undergoing clinical trials for the treatment of human tumors. Here, we investigate the cellular pathways by which sagopilone blocks tumor cell proliferation and compare the intracellular pharmacokinetics and the in vivo pharmacodynamics of sagopilone with other microtubule-stabilizing (or tubulin-polymerizing) agents. Cellular uptake and fractionation/localization studies revealed that sagopilone enters cells more efficiently, associates more tightly with the cytoskeleton, and polymerizes tubulin more potently than paclitaxel. Moreover, in contrast to paclitaxel and other epothilones [such as the natural product epothilone B (patupilone) or its partially synthetic analogue ixabepilone], sagopilone is not a substrate of the P-glycoprotein efflux pumps. Microtubule stabilization by sagopilone caused mitotic arrest, followed by transient multinucleation and activation of the mitochondrial apoptotic pathway. Profiling of the proapoptotic signal transduction pathway induced by sagopilone with a panel of small interfering RNAs revealed that sagopilone acts similarly to paclitaxel. In HCT 116 colon carcinoma cells, sagopilone-induced apoptosis was partly antagonized by the knockdown of proapoptotic members of the Bcl-2 family, including Bax, Bak, and Puma, whereas knockdown of Bcl-2, Bcl-X(L), or Chk1 sensitized cells to sagopilone-induced cell death. Related to its improved subcellular pharmacokinetics, however, sagopilone is more cytotoxic than other epothilones in a large panel of human cancer cell lines in vitro and in vivo. In particular, sagopilone is highly effective in reducing the growth of paclitaxel-resistant cancer cells. These results underline the processes behind the therapeutic efficacy of sagopilone, which is now evaluated in a broad phase II program.

Epothilones and new analogues of the microtubule modulators in taxane-resistant disease

BACKGROUND

Microtubule-stabilising agents typified by the epothilone class of drug have demonstrated promising activity in Phase II and III clinical trials.

OBJECTIVE

Data supporting the efficacy of these agents are reviewed and their potential use in taxane-refractory disease assessed.

METHODS

Preclinical evidence assessing the role of the spindle assembly checkpoint in determining the cellular response to microtubule stabilization are presented together with clinical data documenting the efficacy of non-taxane microtubule modulators.

RESULTS/CONCLUSIONS

Evidence suggests that microtubule-stabilising agents prolong activation of the spindle assembly checkpoint which may promote cancer cell death in mitosis or following mitotic exit. A weakened spindle assembly checkpoint is associated with altered sensitivity to agents targeting the microtubule and therefore pathways of drug resistance may be shared by these cytotoxic therapies. Preliminary clinical trial data do suggest modest activity of epothilones in truly taxane-resistant patient cohorts, indicating the potential niche for these agents in a molecularly undefined patient group, potentially implicating the role of P-glycoprotein in the acquisition of taxane-resistant disease. Trial data of these antimitotic agents will be presented together with their potential role in taxane-resistant disease and the implications for future clinical trial design.

Ixabepilone for the treatment of solid tumors: a review of clinical data

BACKGROUND

Microtubule stabilizing agents such as taxanes are an integral part of therapy for multiple solid tumors. However, due to limitations of these agents, newer more effective cytotoxic agents are necessary. Ixabepilone, an epothilone B analog, is a novel microtubule stabilizing agent.

OBJECTIVE

This review provides an updated summary of emerging clinical experience with Ixabepilone.

METHODS

Phase I, II and III clinical trials presented in abstract form or journal articles found within a PubMed search through November 2007 are described in this review.

RESULTS/CONCLUSION

Ixabepilone offers promising clinical activity in a variety of solid tumors. Ixabepilone is FDA-approved for the treatment of breast cancer refractory to anthracyclines and taxanes. The optimal dose and schedule are still being defined, and the predominant side effects are bone marrow suppression and neuropathy.