PLX9486 shows anti-tumor efficacy in patient-derived, tyrosine kinase inhibitor-resistant KIT-mutant xenograft models of gastrointestinal stromal tumors.

The purpose of the present study was to investigate the in vitro and in vivo activity of PLX9486, a tyrosine kinase inhibitor (TKI) targeting both primary KIT exon 9 and 11 and secondary exon 17 and 18 mutations in gastrointestinal stromal tumors (GISTs). Imatinib, a potent inhibitor of mutated KIT, has revolutionized the clinical management of advanced, metastatic GIST. However, secondary resistance develops mainly through acquired mutations in KIT exons 13/14 or exons 17/18. Second-line sunitinib potently inhibits KIT exon 13/14 mutants but is ineffective against exon 17 mutations. In our study, PLX9486 demonstrated in vitro nanomolar potency in inhibiting the growth and KIT phosphorylation of engineered BaF3 cells transformed with KIT exon 17 mutations (p.D816V) and with the double KIT exon 11/17 mutations (p.V560G/D816V). The in vivo efficacy of PLX9486 was evaluated using two imatinib-resistant GIST patient-derived xenograft (PDX) models. In UZLX-GIST9 (KIT: p.P577del;W557LfsX5;D820G), PLX9486 100 mg/kg/day resulted in significant inhibition of proliferation. Pharmacodynamic analysis showed a pronounced reduction in mitogen-activated protein kinase (MAPK) activation and other downstream effects of the KIT signaling pathway but no significant effect on KIT Y703 and Y719 phosphorylation. Similarly, in MRL-GIST1 (KIT: p.W557_K558del;Y823D) PLX9486 treatment led to significant tumor regression and strong inhibition of MAPK activation. Interestingly, the inhibitory effect on MAPK activation was evident even after a single dose of PLX9486. In conclusion, PLX9486 showed anti-tumor efficacy in patient-derived imatinib-resistant GIST xenograft models, mainly through inhibition of KIT signaling. These preclinical efficacy data encourage further testing of PLX9486 in the clinical setting.

Sarcomatoid dedifferentiation in metastatic clear cell renal cell carcinoma and outcome on treatment with anti-vascular endothelial growth factor receptor tyrosine kinase inhibitors: a retrospective analysis.

INTRODUCTION: This study aimed to assess the efficacy of anti-vascular endothelial growth factor receptor tyrosine kinase inhibitors (anti-VEGFR-TKIs) in patients with metastatic clear cell renal cell carcinoma (m-ccRCC) with sarcomatoid dedifferentiation. PATIENTS AND METHODS: The files of all patients with m-ccRCC consecutively treated with first-line anti-VEGFR-TKIs at the authors' institution were retrospectively reviewed. Pathology slides from nephrectomy and metastasectomy were assessed for the presence and extent of sarcomatoid dedifferentiation. RESULTS: A total of 124 patients were included; nephrectomy and metastasectomy specimens were available in 117 and 35 patients, respectively. Thirty percent of the primary nephrectomy specimens had sarcomatoid features, and the median involvement of the sarcomatoid component was 21% (range, 1%-95%). Patients with an important sarcomatoid component, defined as ≥ 25% involvement of the tumor, had a very poor outcome: progression-free survival (PFS) and overall survival (OS) were 3 and 6 months, respectively, and no partial responses (PR) were observed. Patients without sarcomatoid dedifferentiation or with sarcomatoid involvement < 25% had a PFS of 12 months (P < .0001; hazard ratio [HR], 51; 95% CI, 12.58-207.3), an OS of 22 months (P < .0001, HR, 10.72; 95% CI, 3.56-32.25), and a PR rate of 50% (P = .0015). Patients with a sarcomatoid component ≥ 25% in the metastasectomy also had a poorer PFS and OS on anti-VEGFR-TKIs compared with patients with < 25% of sarcomatoid features at these sites. CONCLUSION: Patients with m-ccRCC whose tumors contain a component of sarcomatoid dedifferentiation of ≥ 25% of the total tumor volume have a very poor outcome when treated with anti-VEGFR-TKIs. Analysis of the extent of sarcomatoid features in resected metastases can provide additional prognostic information.

Patterns of care, prognosis, and survival in patients with metastatic gastrointestinal stromal tumors (GIST) refractory to first-line imatinib and second-line sunitinib.

BACKGROUND: Data regarding the management and outcome of patients with metastatic gastrointestinal stromal tumors (GIST) refractory to 1st-line imatinib and 2nd-line sunitinib are limited. METHODS: Medical records of 223 imatinib-resistant and sunitinib-resistant GIST who were treated in 11 major referral centers were reviewed. RESULTS: The three most frequent drugs used in the 3rd-line setting were: nilotinib n = 67 (29.5%), sorafenib n = 55 (24.5%), and imatinib n = 40 (17.5%). There were 18 patients (8%) who received best supportive care (BSC) only. The median progression-free survival (PFS) and overall survival (OS) on 3rd-line treatment were 3.6 months [95% confidence interval (95% CI), 3.1-4.1] and 9.2 months (95% CI, 7.5-10.9), respectively. Multivariate analysis showed that, in the 3rd-line setting, albumin level and KIT/PDGFRA mutational status were significantly associated with PFS, whereas performance status and albumin level were associated with OS. After adjustment for prognostic factors, nilotinib and sorafenib provided the best PFS and OS. Rechallenge with imatinib was also associated with improved OS in comparison with BSC. CONCLUSION: In the 3rd-line setting, rechallenge with imatinib provided limited clinical benefit but was superior to BSC. Sorafenib and nilotinib have significant clinical activity in imatinib-resistant and sunitinib-resistant GIST and may represent an alternative for rechallenge with imatinib.

The preclinical and clinical activity of aviscumine: a potential anticancer drug.

Extracts from the European mistletoe plant Viscumalbum have been studied for decades for their direct and indirect anticancer activity. Therefore, scientists were interested in identifying the active compound (mistletoe lectin) in these extracts and making it available as a highly purified molecule for drug development. Recombinant mistletoe lectin (INN: aviscumine) was produced in Escherichiacoli. It has been shown to have immunomodulatory and cytotoxic activity in invitro and in animal models and can target tumour cells. Clinical phase I studies also demonstrated immunomodulatory activity, which appears to have a positive effect on disease stabilisation. This review explores the current knowledge base for aviscumine's mechanism of action, efficacy and side-effects in both preclinical studies and clinical trials, and it considers aviscumine's potential as a cancer therapy.

Polo-like kinase (PLK) inhibitors in preclinical and early clinical development in oncology.

Polo-like kinases (PLKs) are a group of highly conserved serine/threonine protein kinases that play a key role in processes such as cell division and checkpoint regulation of mitosis. About 80% of human tumors, of various origins, express high levels of PLK transcripts. However, PLK mRNA is mostly absent in surrounding healthy tissues. Overexpression of PLK is associated with a poor prognosis in several tumor types and a lower overall survival rate. The overexpression of PLKs in human tumors, but not in healthy nondividing cells, makes them an attractive, selective target for cancer drug development. PLK inhibitors interfere with different stages of mitosis, such as centrosome maturation, spindle formation, chromosome separation, and cytokinesis. They induce mitotic chaos and severely perturb cell cycle progression, eventually leading to cancer cell death. Several PLK inhibitors are in development and are undergoing evaluations as potential cancer treatments. This review includes an overview of PLK inhibitors in early clinical development (i.e., BI 2536, BI 6727, GSK461364, ON 019190.Na, and HMN-214) and in advanced preclinical development (i.e., ZK-thiazolidinone, NMS-1, CYC-800, DAP-81, and LC-445). If proof of principle is confirmed in large studies, PLK inhibitors will offer a new targeted antitumor therapy for cancer patients.

Using the continual reassessment method: lessons learned from an EORTC phase I dose finding study.

Many clinicians often do not feel comfortable with the Continual Reassessment Method (CRM). This article reviews its implementation, showing the characteristics, advantages and limitations of this method in Phase I studies as an alternative to the classical 'Fibonacci' escalation schema. A two center, dose escalation phase I study of rViscumin was carried out. Thirty-seven patients were included at 14 different dose-levels (10 to 6400 ng/kg). The complete clinical results are presented elsewhere. A 2-step CRM design enables one to speed-up the study and most importantly to obtain an accurate estimate of the maximum tolerated dose (MTD). Different management issues related to a multicenter study are illustrated and we show how the method can go wrong when severe toxicity, or dose limiting toxicity (DLT), is not considered by the clinician as being sufficient to limit dose escalation (here a grade 3 asthenia related to the drug). This would have affected any dose finding methods. We believe that CRM is a good alternative to the standard method from both a statistical and a practical point of view but further methodological research is necessary to address the issues related to the composite nature of the endpoint.

Capecitabine/oxaliplatin, a safe and active first-line regimen for older patients with metastatic colorectal cancer: post hoc analysis of a large phase II study.

PURPOSE: The tumor-activated fluoropyrimidine capecitabine achieves response rates superior to those of bolus 5-fluorouracil/leucovorin (5-FU/LV) as first-line treatment for metastatic colorectal cancer (CRC), with favorable safety and fewer hospitalizations. Capecitabine is also at least as effective as bolus 5-FU/LV in the adjuvant setting, again with a favorable safety profile. Improved outcomes with capecitabine versus bolus 5-FU/LV in the adjuvant setting have been shown in overall trial populations and in patients aged >or= 70 years. Capecitabine/oxaliplatin (XelOx) is a safe and active combination for the first-line treatment of metastatic CRC. PATIENTS AND METHODS: This post hoc analysis of a large phase II trial compared data from older and younger patients treated with first-line XelOx: oxaliplatin 130 mg/m(2) intravenously on day 1 followed by oral capecitabine 1,000 mg/m(2) twice daily for 14 days every 3 weeks. RESULTS: The median age of the overall population (N = 96) was 64 years (range, 34-79 years), including 52 younger patients (< 65 years of age) and 44 older patients (>or= 65 years of age). Both age groups received a median of 8 cycles (range, 1-26 cycles) of XelOx. The XelOx regimen had similar high activity in both groups, with response rates of 58% (95% CI, 43%-71%) and 52% (95% CI, 37%-68%) in younger and older patients, respectively. In addition, time to disease progression and overall survival were similar in both groups (P > 0.5 for both outcomes). The XelOx regimen also had a favorable safety profile, with no clinically relevant differences between older and younger patients. The overall incidence of adverse events (including grade 3/4), dose reductions, and withdrawals because of adverse events were similar in both groups. CONCLUSION: In the context of an aging population, XelOx provides a highly effective and tolerable first-line treatment for patients with metastatic CRC.

Adaptation and performance of an immuno-PCR assay for the quantification of Aviscumine in patient plasma samples.

An immuno-polymerase chain reaction (IPCR) assay is used to evaluate the kinetic behaviour of the novel anti-cancer drug Aviscumine in plasma samples taken from 41 patients during a 3-year clinical trial. The ultrasensitive IPCR assay employed the amplification of a detection-antibody linked marker-DNA and an internal competitor DNA for standardization, thus enabling the detection of the antigen in concentrations far below the detection limit of conventional enzyme-linked immuno-sorbent assay (ELISA). The quantification of Aviscumine was carried out using external calibration curves obtained from individual patient plasma samples, collected previous to the administration of Aviscumine, which were spiked with known amounts of the reference substance Aviscumine. Additional controls were measured containing standardized human serum spiked with Aviscumine to assure the continuous general reproducibility of the assay as well as to estimate differences between individual patients. Average recovery was found to be 95+/-19% and the average deviation in precision of the assay was determined to be 9+/-5%. Data for the quantification of Aviscumine were obtained from all patient samples investigated with the exception of a single patient. The collected data provided the basis for the valid routine quantification of patient samples for the calculation of the pharmacokinetic behaviour of Aviscumine in patient plasma.

The modulated oral fluoropyrimidine prodrug S-1, and its use in gastrointestinal cancer and other solid tumors.

The fluoropyrimidine anticancer agent 5-fluorouracil (5-FU) is active in a wide range of solid tumors, particularly gastric, colorectal, and head and neck cancers. Whilst infusional 5-FU is associated with higher response rates and a favorable safety profile as compared to the classical i.v. bolus administration, prolonged infusions can be inconvenient for the patients and catheter-related problems are common complications. An oral 5-FU formulation would allow for sustained 5-FU plasma concentrations, mimicking the pharmacokinetics (PK) of a continuous infusion with the addition of convenience of administration. The oral administration of 5-FU itself is not feasible due to the high activity of dihydropyrimidine dehydrogenase in the gut wall, which causes rapid metabolism of the drug, and results in decreased and erratic absorption of 5-FU and non-linear PK. To bypass this problem, oral fluoropyrimidine derivatives were developed either in the form of 5-FU prodrugs (i.e. tegafur, doxifluridine or capecitabine), or as enzyme inhibitors (i.e. eniluracil) administered with 5-FU, or as both prodrugs and enzyme inhibitors (i.e. S-1, UFT or BOF-A2). This review will focus on the oral fluoropyrimidine S-1, which consists of the 5-FU prodrug tegafur (ftorafur, FT) and two enzyme inhibitors, i.e. CDHP (5-chloro-2,4-dihydroxypyridine) and OXO (potassium oxonate), in a molar ratio of 1(FT):0.4 (CDHP):1(OXO). Phase II trials have demonstrated that S-1, as a single agent, is active for the treatment of gastric, colorectal, head and neck, breast, non-small cell lung, and pancreatic cancers. Phase III trials are currently underway in gastric cancer and these results are awaited to confirm the phase II findings. Furthermore, the combination of S-1 with cisplatin (CDDP), irinotecan or docetaxel for the treatment of gastric cancer and with CDDP for non-small cell and pancreatic cancer is feasible and active. The activity observed with S-1 in the phase II studies is at least equivalent, if not better, than continuous i.v. and bolus 5-FU and the other oral fluoropyrimidines. Thus, we may finally be seeing the realization of oral treatments for the management of various solid tumors and could be on the brink of a new approach to treatment strategies.