Comparison of CNS penetration, tissue distribution, and pharmacology of VP 16-213 by intracarotid and intravenous administration in dogs

Surgical Adjuncts for Glioblastoma

Although surgical resection of the solid tumor component of glioblastoma has been shown to provide a survival advantage, it will never be a curative procedure. Yet, systemically applied adjuvants (radiation therapy and chemotherapy) also are not curative and their options are limited by the inability of most agents to cross the blood-brain barrier. Direct delivery of adjuvant therapies during a surgical procedure potentially provides an approach to bypass the blood-brain barrier and effectively treat residual tumor cells. This article summarizes the approaches and therapeutics that have been evaluated to date, and challenges that remain to be overcome.

Blood-brain barrier, cytotoxic chemotherapies and glioblastoma

INTRODUCTION

Glioblastomas (GBM) are the most common and aggressive primary malignant brain tumors in adults. The blood brain barrier (BBB) is a major limitation reducing efficacy of anti-cancer drugs in the treatment of GBM patients. Areas covered: Virtually all GBM recur after the first-line treatment, at least partly, due to invasive tumor cells protected from chemotherapeutic agents by the intact BBB in the brain adjacent to tumor. The passage through the BBB, taken by antitumor drugs, is poorly and heterogeneously documented in the literature. In this review, we have focused our attention on: (i) the BBB, (ii) the passage of chemotherapeutic agents across the BBB and (iii) the strategies investigated to overcome this barrier. Expert commentary: A better preclinical knowledge of the crossing of the BBB by antitumor drugs will allow optimizing their clinical development, alone or combined with BBB bypassing strategies, towards an increased success rate of clinical trials.

Delivery of chemotherapeutics across the blood-brain barrier: challenges and advances

The blood-brain barrier (BBB) limits drug delivery to brain tumors. We utilize intraarterial infusion of hyperosmotic mannitol to reversibly open the BBB by shrinking endothelial cells and opening tight junctions between the cells. This approach transiently increases the delivery of chemotherapy, antibodies, and nanoparticles to brain. Our preclinical studies have optimized the BBB disruption (BBBD) technique and clinical studies have shown its safety and efficacy. The delivery of methotrexate-based chemotherapy in conjunction with BBBD provides excellent outcomes in primary central nervous system lymphoma (PCNSL) including stable or improved cognitive function in survivors a median of 12 years (range 2-26 years) after diagnosis. The addition of rituximab to chemotherapy with BBBD for PCNSL can be safely accomplished with excellent overall survival. Our translational studies of thiol agents to protect against platinum-induced toxicities led to the development of a two-compartment model in brain tumor patients. We showed that delayed high-dose sodium thiosulfate protects against carboplatin-induced hearing loss, providing the framework for large cooperative group trials of hearing chemoprotection. Neuroimaging studies have identified that ferumoxytol, an iron oxide nanoparticle blood pool agent, appears to be a superior contrast agent to accurately assess therapy-induced changes in brain tumor vasculature, in brain tumor response to therapy, and in differentiating central nervous system lesions with inflammatory components. This chapter reviews the breakthroughs, challenges, and future directions for BBBD.

Chemotherapy delivery issues in central nervous system malignancy: a reality check

PURPOSE

This review assesses the current state of knowledge regarding preclinical and clinical pharmacology for brain tumor chemotherapy and evaluates relevant brain tumor pharmacology studies before October 2006.

RESULTS

Chemotherapeutic regimens in brain tumor therapy have often emerged from empirical clinical studies with retrospective pharmacologic explanations, rather than prospective trials of rational chemotherapeutic approaches. Brain tumors are largely composed of CNS metastases of systemic cancers. Primary brain tumors, such as glioblastoma multiforme or primary CNS lymphomas, are less common. Few of these tumors have well-defined optimal treatment. Brain tumors are protected from systemic chemotherapy by the blood-brain barrier (BBB) and by intrinsic properties of the tumors. Pharmacologic studies of delivery of conventional chemotherapeutics and novel therapeutics showing actual tumor concentrations and biologic effect are lacking.

CONCLUSION

In this article, we review drug delivery across the BBB, as well as blood-tumor and -cerebrospinal fluid (CSF) barriers, and mechanisms to increase drug delivery to CNS and CSF tumors. Because of the difficulty in treating CNS tumors, innovative treatments and alternative delivery techniques involving brain/cord capillaries, choroid plexus, and CSF are needed.

Assessment of toxicokinetics and toxicodynamics following intravenous administration of etoposide phosphate in beagle dogs

The toxicokinetics and toxicodynamics of etoposide phosphate (BMY-40481), a water soluble phosphate ester derivative of etoposide, were investigated in beagle dogs (N = 4) following 5 min i.v. infusion doses equivalent to 57, 114 and 461 mg/m2 of etoposide. The doses were administered in sequence starting with the low dose. There was a 28 day wash-out period between the doses. Serial blood samples were collected over 32 hr and the levels of intact BMY-40481 and etoposide in plasma were measured using validated HPLC assays. Hematology profiles were obtained at pre-dose, and twice a week post-dose for 28 days to correlate systemic exposure to etoposide and hematologic toxicity. Following i.v. administration, plasma concentrations of BMY-40481 declined rapidly. For the 3 doses, mean t 1/2 of BMY-40481 ranged from 0.11-0.17 hr (6.6-11 min). The mean Cmax and AUC values of BMY-40481 ranged from 1.72-40.5 micrograms/ml and 0.16-4.14 hr.micrograms/ml, respectively. Both systemic clearance and steady state volume of distribution of BMY-40481 decreased significantly at the high dose. In contrast, the mean Cmax and AUC values of etoposide ranged from 5.46-39.4 micrograms/ml and 2.28-22.6 hr.micrograms/ml, respectively. Cmax occurred at the end of infusion (5 min) at all dose levels, indicating that etoposide was rapidly formed from BMY-40481. The apparent systemic clearance (range: 342-435 ml/min/m2) and apparent steady state volume of distribution (range: 21.5-26.6 l/m2) of etoposide were dose-independent. The AUC of etoposide was significantly correlated with hematologic toxicity, i.e., percent decreases in white blood count (WBC), absolute neutrophil count (ANC) and platelets.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacology of intrathecal VP-16-213 in dogs

VP-16-213 is an anticancer drug that is active against a number of malignancies including small cell lung cancer, lymphoma, and leukemia which are often complicated by the development of leptomeningeal carcinomatosis. To investigate the potential usefulness of VP-16-213 for intrathecal administration, the pharmacology and toxicity of intrathecal VP-16-213 was determined. VP-16-213 at varying doses (0.01-1.0 mg.kg) was instilled intrathecally in dogs. Plasma, CSF, spinal cord, and brain tissue drug concentrations were determined by radiochemical and high performance liquid chromatography technique. Drug concentrations were strikingly higher in spinal cord tissue near the injection site compared to more distal cord sites. CSF concentration of VP-16-213 is 3-4 logs higher compared to concurrent plasma levels. Severe neurotoxicity occurred at the higher doses used. Due to limited diffusion and extremely low doses which could be used without life-threatening neurotoxicity, VP-16-213 does not appear to be a useful agent for intrathecal administration.

Effect of intracarotid infusion of etoposide with angiotensin II-induced hypertension on the blood-brain barrier and the brain tissue

This study investigated the effects of the intracarotid infusion of etoposide in combination with angiotensin II (AT II)-induced hypertension on the blood-brain barrier (BBB) and brain tissue in rats. Eighty rats were divided into five groups: Group 1, intravenous infusion of AT II to increase arterial blood pressure; Group 2, intracarotid infusion of etoposide at 22.5 mg/m2 for 10 minutes; Group 3, intracarotid infusion of etoposide at 75.0 mg/m2 for 10 minutes; Group 4, intracarotid infusion of etoposide at 75.0 mg/m2 for 20 minutes; Group 5, intracarotid infusion of etoposide at 75.0 mg/m2 for 10 minutes with AT II-induced hypertension. Evans blue staining of the brain was used as a monitor of BBB disruption. Mean arterial blood pressure over the experimental period in Group 1 increased from 86.3 +/- 1.3 mmHg (mean +/- SEM) to 139.0 +/- 2.4 mmHg, and Group 5 from 85.9 +/- 1.8 mmHg to 137.3 +/- 2.4 mmHg. None of the animals in Group 1 and 2 showed any obvious neurological change, while all the animals in Group 3, 4 and 5 exhibited diminished activity as their sole neurological change throughout the course of the experiment. Slight evidence of BBB disruption was seen in only 25% of the animals in Group 1. Significant BBB disruption was found in the animals in Group 2, 3, 4 and 5. No histological change was observed in any animal in Group 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentrations of VP16 and VM26 in human brain tumors

VP16 and VM26 were determined by high pressure liquid chromatography in intracerebral tumors, adjacent normal brain tissue, plasma and CSF samples from 24 patients given the two drugs before surgical resection of the tumor. The drugs were administered at doses of 100-150 mg/m2 as a 1-hour i.v. infusion, between 1.5 and 12 hours before surgery. Concentrations of VP16 ranged between 1.05 and 3.28 micrograms/g in tumors in the series of patients who received the drug 1.5-3 hours before surgery and between less than 0.05 and 1.12 micrograms/g in four patients who received the drug 9-13 hours before surgery. Tumor concentrations of VM26 also varied, ranging from less than 0.05 to 1.68 micrograms/g between 1.5 and 12 hours before surgery. VP16 and VM26 in the apparently normal brain tissue surrounding the tumor were low or undetectable except in one patient who had received radiotherapy, in whom we found 3.1 micrograms/g.