Andrea L. Harzstark

Metabolic imaging of patients with prostate cancer using hyperpolarized [1-¹³C]pyruvate.

Metabolic imaging with hyperpolarized pyruvate was used to safely and noninvasively visualize prostate tumors in patients. The Hyperpolarized Prostate Cancer cells have a different metabolism than healthy cells. Specifically, they consume more pyruvate—a key component in glycolysis—than their normal counterparts. Nelson and colleagues therefore used a hyperpolarized form of pyruvate ([1-13C]pyruvate) to sensitively image increased levels of its product, [1-13C]lactate, as well as the flux of pyruvate to lactate. The [1-13C]pyruvate agent was used here in a first-in-human study in men with prostate cancer. Patients received varying doses of [1-13C]pyruvate that were found to be safe. These patients were then rapidly imaged with hyperpolarized 13C magnetic resonance (MR), which was able to provide dynamic (time course) information as well as three-dimensional (3D) (spatial) data at a single time point. Tumors were detected in all patients with biopsy-proven cancer. And, importantly, with 13C MR imaging (MRI), Nelson et al. were able to see cancer in regions of the prostate that were previously considered to be tumor-free upon inspection with other conventional anatomic imaging methods. With the ability to safely image tumor location and also follow tumor metabolism over time, hyperpolarized 13C MRI may be useful both for initial diagnosis and for monitoring therapy. Although the patients in this study had early-stage disease, the authors believe that [1-13C]lactate/[1-13C]pyruvate flux will only increase with tumor grade, making this imaging technology amenable to more advanced and aggressive cancers. Future studies will focus on optimizing agent preparation and delivery to ensure that this imaging technology can benefit patients in all clinical settings. This first-in-man imaging study evaluated the safety and feasibility of hyperpolarized [1-13C]pyruvate as an agent for noninvasively characterizing alterations in tumor metabolism for patients with prostate cancer. Imaging living systems with hyperpolarized agents can result in more than 10,000-fold enhancement in signal relative to conventional magnetic resonance (MR) imaging. When combined with the rapid acquisition of in vivo 13C MR data, it is possible to evaluate the distribution of agents such as [1-13C]pyruvate and its metabolic products lactate, alanine, and bicarbonate in a matter of seconds. Preclinical studies in cancer models have detected elevated levels of hyperpolarized [1-13C]lactate in tumor, with the ratio of [1-13C]lactate/[1-13C]pyruvate being increased in high-grade tumors and decreased after successful treatment. Translation of this technology into humans was achieved by modifying the instrument that generates the hyperpolarized agent, constructing specialized radio frequency coils to detect 13C nuclei, and developing new pulse sequences to efficiently capture the signal. The study population comprised patients with biopsy-proven prostate cancer, with 31 subjects being injected with hyperpolarized [1-13C]pyruvate. The median time to deliver the agent was 66 s, and uptake was observed about 20 s after injection. No dose-limiting toxicities were observed, and the highest dose (0.43 ml/kg of 230 mM agent) gave the best signal-to-noise ratio for hyperpolarized [1-13C]pyruvate. The results were extremely promising in not only confirming the safety of the agent but also showing elevated [1-13C]lactate/[1-13C]pyruvate in regions of biopsy-proven cancer. These findings will be valuable for noninvasive cancer diagnosis and treatment monitoring in future clinical trials.

Cabozantinib in Patients With Advanced Prostate Cancer: Results of a Phase II Randomized Discontinuation Trial

PURPOSE Cabozantinib (XL184) is an orally bioavailable tyrosine kinase inhibitor with activity against MET and vascular endothelial growth factor receptor 2. We evaluated the activity of cabozantinib in patients with castration-resistant prostate cancer (CRPC) in a phase II randomized discontinuation trial with an expansion cohort. PATIENTS AND METHODS Patients received 100 mg of cabozantinib daily. Those with stable disease per RECIST at 12 weeks were randomly assigned to cabozantinib or placebo. Primary end points were objective response rate at 12 weeks and progression-free survival (PFS) after random assignment. RESULTS One hundred seventy-one men with CRPC were enrolled. Random assignment was halted early based on the observed activity of cabozantinib. Seventy-two percent of patients had regression in soft tissue lesions, whereas 68% of evaluable patients had improvement on bone scan, including complete resolution in 12%. The objective response rate at 12 weeks was 5%, with stable disease in 75% of patients. Thirty-one patients with stable disease at week 12 were randomly assigned. Median PFS was 23.9 weeks (95% CI, 10.7 to 62.4 weeks) with cabozantinib and 5.9 weeks (95% CI, 5.4 to 6.6 weeks) with placebo (hazard ratio, 0.12; P < .001). Serum total alkaline phosphatase and plasma cross-linked C-terminal telopeptide of type I collagen were reduced by ≥ 50% in 57% of evaluable patients. On retrospective review, bone pain improved in 67% of evaluable patients, with a decrease in narcotic use in 56%. The most common grade 3 adverse events were fatigue (16%), hypertension (12%), and hand-foot syndrome (8%). CONCLUSION Cabozantinib has clinical activity in men with CRPC, including reduction of soft tissue lesions, improvement in PFS, resolution of bone scans, and reductions in bone turnover markers, pain, and narcotic use.

Ipilimumab alone or in combination with radiotherapy in metastatic castration-resistant prostate cancer: results from an open-label, multicenter phase I/II study

BACKGROUND This phase I/II study in patients with metastatic castration-resistant prostate cancer (mCRPC) explored ipilimumab as monotherapy and in combination with radiotherapy, based on the preclinical evidence of synergistic antitumor activity between anti-CTLA-4 antibody and radiotherapy. PATIENTS AND METHODS In dose escalation, 33 patients (≥6/cohort) received ipilimumab every 3 weeks × 4 doses at 3, 5, or 10 mg/kg or at 3 or 10 mg/kg + radiotherapy (8 Gy/lesion). The 10-mg/kg cohorts were expanded to 50 patients (ipilimumab monotherapy, 16; ipilimumab + radiotherapy, 34). Evaluations included adverse events (AEs), prostate-specific antigen (PSA) decline, and tumor response. RESULTS Common immune-related AEs (irAEs) among the 50 patients receiving 10 mg/kg ± radiotherapy were diarrhea (54%), colitis (22%), rash (32%), and pruritus (20%); grade 3/4 irAEs included colitis (16%) and hepatitis (10%). One treatment-related death (5 mg/kg group) occurred. Among patients receiving 10 mg/kg ± radiotherapy, eight had PSA declines of ≥50% (duration: 3-13+ months), one had complete response (duration: 11.3+ months), and six had stable disease (duration: 2.8-6.1 months). CONCLUSIONS In mCRPC patients, ipilimumab 10 mg/kg ± radiotherapy suggested clinical antitumor activity with disease control and manageable AEs. Two phase III trials in mCRPC patients evaluating ipilimumab 10 mg/kg ± radiotherapy are ongoing. ClinicalTrials.gov identifier: NCT00323882.BACKGROUND This phase I/II study in patients with metastatic castration-resistant prostate cancer (mCRPC) explored ipilimumab as monotherapy and in combination with radiotherapy, based on the preclinical evidence of synergistic antitumor activity between anti-CTLA-4 antibody and radiotherapy. PATIENTS AND METHODS In dose escalation, 33 patients (≥6/cohort) received ipilimumab every 3 weeks × 4 doses at 3, 5, or 10 mg/kg or at 3 or 10 mg/kg + radiotherapy (8 Gy/lesion). The 10-mg/kg cohorts were expanded to 50 patients (ipilimumab monotherapy, 16; ipilimumab + radiotherapy, 34). Evaluations included adverse events (AEs), prostate-specific antigen (PSA) decline, and tumor response. RESULTS Common immune-related AEs (irAEs) among the 50 patients receiving 10 mg/kg ± radiotherapy were diarrhea (54%), colitis (22%), rash (32%), and pruritus (20%); grade 3/4 irAEs included colitis (16%) and hepatitis (10%). One treatment-related death (5 mg/kg group) occurred. Among patients receiving 10 mg/kg ± radiotherapy, eight had PSA declines of ≥50% (duration: 3-13+ months), one had complete response (duration: 11.3+ months), and six had stable disease (duration: 2.8-6.1 months). CONCLUSIONS In mCRPC patients, ipilimumab 10 mg/kg ± radiotherapy suggested clinical antitumor activity with disease control and manageable AEs. Two phase III trials in mCRPC patients evaluating ipilimumab 10 mg/kg ± radiotherapy are ongoing. ClinicalTrials.gov identifier: NCT00323882.

Phase II and Biomarker Study of the Dual MET/VEGFR2 Inhibitor Foretinib in Patients With Papillary Renal Cell Carcinoma

PURPOSE Foretinib is an oral multikinase inhibitor targeting MET, VEGF, RON, AXL, and TIE-2 receptors. Activating mutations or amplifications in MET have been described in patients with papillary renal cell carcinoma (PRCC). We aimed to evaluate the efficacy and safety of foretinib in patients with PRCC. PATIENTS AND METHODS Patients were enrolled onto the study in two cohorts with different dosing schedules of foretinib: cohort A, 240 mg once per day on days 1 through 5 every 14 days (intermittent arm); cohort B, 80 mg daily (daily dosing arm). Patients were stratified on the basis of MET pathway activation (germline or somatic MET mutation, MET [7q31] amplification, or gain of chromosome 7). The primary end point was overall response rate (ORR). RESULTS Overall, 74 patients were enrolled, with 37 in each dosing cohort. ORR by Response Evaluation Criteria in Solid Tumors (RECIST) 1.0 was 13.5%, median progression-free survival was 9.3 months, and median overall survival was not reached. The presence of a germline MET mutation was highly predictive of a response (five of 10 v five of 57 patients with and without germline MET mutations, respectively). The most frequent adverse events of any grade associated with foretinib were fatigue, hypertension, gastrointestinal toxicities, and nonfatal pulmonary emboli. CONCLUSION Foretinib demonstrated activity in patients with advanced PRCC with a manageable toxicity profile and a high response rate in patients with germline MET mutations.

Platinum-Based Chemotherapy for Variant Castrate-Resistant Prostate Cancer

Purpose: Clinical features characteristic of small-cell prostate carcinoma (SCPC), “anaplastic,” often emerge during the progression of prostate cancer. We sought to determine the efficacy of platinum-based chemotherapy in patients meeting at least one of seven prospectively defined “anaplastic” clinical criteria, including exclusive visceral or predominantly lytic bone metastases, bulky tumor masses, low prostate-specific antigen levels relative to tumor burden, or short response to androgen deprivation therapy. Experimental Design: A 120-patient phase II trial of first-line carboplatin and docetaxel (CD) and second-line etoposide and cisplatin (EP) was designed to provide reliable clinical response estimates under a Bayesian probability model with early stopping rules in place for futility and toxicity. Results: Seventy-four of 113 (65.4%) and 24 of 71 (33.8%) were progression free after four cycles of CD and EP, respectively. Median overall survival (OS) was 16 months [95% confidence interval (CI), 13.6–19.0 months]. Of the seven “anaplastic” criteria, bulky tumor mass was significantly associated with poor outcome. Lactic acid dehydrogenase strongly predicted for OS and rapid progression. Serum carcinoembryonic antigen (CEA) concentration strongly predicted OS but not rapid progression. Neuroendocrine markers did not predict outcome or response to therapy. Conclusion: Our findings support the hypothesis that patients with “anaplastic” prostate cancer are a recognizable subset characterized by a high response rate of short duration to platinum-containing chemotherapies, similar to SCPC. Our results suggest that CEA is useful for selecting therapy in men with castration-resistant prostate cancer and consolidative therapies to bulky high-grade tumor masses should be considered in this patient population. Clin Cancer Res; 19(13); 3621–30. ©2013 AACR.

Phase I Study of Dovitinib (TKI258), an Oral FGFR, VEGFR, and PDGFR Inhibitor, in Advanced or Metastatic Renal Cell Carcinoma

Purpose: Signaling through the fibroblast growth factor (FGF) pathway may account for tumor resistance to antiangiogenic therapies targeting the VEGF pathway. Here, dovitinib (TKI258), a potent oral inhibitor of FGF receptor, VEGF receptor (VEGFR), and platelet-derived growth factor receptor tyrosine kinases, is studied in a dose escalation trial. Experimental Design: Patients with advanced or metastatic renal cell carcinoma (RCC) with predominant clear cell histology were treated with oral dovitinib 500 or 600 mg/day (5-days-on/2-days-off schedule). Results: Twenty heavily pretreated patients (median 3 prior regimens) were enrolled, with 16, 11, and 12 patients having previously received at least 1: VEGFR inhibitor, mTOR inhibitor, and immunotherapy, respectively. Fifteen and 5 patients were treated in 500- and 600-mg cohorts, respectively. Three patients experienced dose-limiting toxicities: grade 2 bradycardia (500 mg), grade 4 hypertensive crisis (600 mg), and grade 3 asthenia with grade 2 nausea and vomiting (600 mg). The most common adverse events related to dovitinib were nausea (75%), diarrhea (70%), vomiting (70%), and asthenia (50%), the majority of which were mild (grade 1 or 2), with grade 3 events 5% or less (except asthenia, 15%) and only one grade 4 event (hypertensive crisis). Two patients achieved a partial response (500 mg), and 12 patients had stable disease, including 2 patients with long lasting disease stabilizations (>1 year) in the 500-mg cohort. Conclusions: Dovitinib was tolerable and showed antitumor activity at a maximum tolerated dose of 500 mg on a 5-days-on/2-days-off schedule in heavily pretreated RCC patients. Clin Cancer Res; 19(5); 1257–68. ©2012 AACR.

Cabozantinib in Chemotherapy-Pretreated Metastatic Castration-Resistant Prostate Cancer: Results of a Phase II Nonrandomized Expansion Study

PURPOSE Cabozantinib (XL184), an oral inhibitor of multiple receptor tyrosine kinases such as MET and VEGFR2, was evaluated in a phase II nonrandomized expansion study in castration-resistant prostate cancer (CRPC). PATIENTS AND METHODS Patients received open-label cabozantinib at daily starting doses of 100 mg or 40 mg until disease progression or unacceptable toxicity. The primary end point was bone scan response, defined as ≥ 30% reduction in bone scan lesion area. Other efficacy end points included overall survival, pain, analgesic use, and biomarkers. RESULTS One hundred forty-four patients sequentially enrolled in either a 100-mg (n = 93) or 40-mg (n = 51) study cohort. Ninety-one patients (63%) had a bone scan response, often by week 6. Treatment resulted in clinically meaningful pain relief (57% of patients) and reduction or discontinuation of narcotic analgesics (55% of patients), as well as improvements in measurable soft tissue disease, circulating tumor cells, and bone biomarkers. Improvements in each of these outcomes were observed in both cohorts: bone scan response in 73% and 45%, respectively; reductions in measurable soft tissue disease in 80% and 79%, respectively. Median overall survival was 10.8 months for the entire population. Most common grade 3 or 4 adverse events were fatigue (22%) and hypertension (14%). Fewer dose reductions because of toxicity were required in the 40-mg group. CONCLUSION The evidence suggests that cabozantinib has clinically meaningful activity in CRPC. Cabozantinib resulted in improvements in bone scans, pain, analgesic use, measurable soft tissue disease, circulating tumor cells, and bone biomarkers. Taken together, these phase II observations warrant further development of cabozantinib in prostate cancer.

A phase 1 study of everolimus and sorafenib for metastatic clear cell renal cell carcinoma

The current study was conducted to assess the maximum tolerated dose (MTD), safety, pharmacokinetics, and preliminary antitumor effect of everolimus, a mammalian target of rapamycin inhibitor, in combination with sorafenib, a tyrosine kinase inhibitor, in patients with metastatic clear cell renal cell carcinoma.

Immunotherapy for prostate cancer using antigen-loaded antigen-presenting cells: APC8015 (Provenge).

Dendritic cells are deficient both in number and function in patients with cancer. Loaded dendritic cell therapies aim to overcome this deficiency by delivering antigens to antigen-presenting cells under ex vivo conditions, improving dendritic cell function. APC8015 (Provenge®; Dendreon Corp., Seattle, WA) is a novel immunotherapeutic, which consists of autologous dendritic cells pulsed ex vivo with PA2024, a recombinant fusion protein consisting of granulocyte macrophage colony-stimulating factor and prostatic acid phosphatase, as an immunogenic agent. A Phase III randomized clinical trial has demonstrated a survival benefit in patients with metastatic hormone-refractory prostate cancer. This review summarizes the clinical trials using APC8015 in prostate cancer and discusses its future role in the treatment of prostate cancer.

Five-year survival in patients with cytokine-refractory metastatic renal cell carcinoma treated with axitinib.

BACKGROUND In a phase II study of axitinib for cytokine-refractory metastatic renal cell carcinoma, median overall survival (OS) was 29.9 months (95% CI, 20.3 to not estimable months). PATIENTS AND METHODS Long-term survival data were collected retrospectively from 52 patients with cytokine-refractory metastatic renal cell carcinoma who received axitinib in a completed phase II study (protocol 1), 11 of whom enrolled in a continuing access protocol (protocol 2), for the current observational study (protocol 3). In a post hoc analysis, the patients were grouped into quartiles based on cycle 1 day 1, 1- to 2-hour post-dose axitinib plasma levels to explore the impact of drug exposure on efficacy. RESULTS The 5-year survival rate was 20.6% (95% CI, 10.9%-32.4%), with a median follow-up of 5.9 years. Frequent all-grade adverse events were fatigue (n = 38; 73.1%), diarrhea (n = 34; 65.4%), hypertension (n = 33; 63.5%), and nausea (n = 33; 63.5%). Quartile 3 patients (axitinib level, 45.2-56.4 ng/mL; n = 12) had the best clinical outcome: objective response rate 82%, median progression-free survival (PFS) 28.3 months, and median OS that was not reached after 5 years. CONCLUSIONS Axitinib was well tolerated and provided an estimated 5-year survival rate of 20.6% for cytokine-refractory metastatic renal cell carcinoma. Exploratory analyses showed numerically higher objective response rate and longer OS and PFS in patients who achieved post-first-dose axitinib plasma concentrations within a specific range.