Osmotic Blood-brain Barrier Disruption Research Articles

Osmotic blood-brain barrier disruption with mannitol followed by methotrexate, rituximab, and carboplatin in treating patients with newly diagnosed primary central nervous system lymphoma.

2077 Background: Osmotic blood-brain barrier disruption (BBBD) uses intra-arterial (IA) mannitol to open the neuro-vascular unit to enhance delivery of therapeutic agents to the brain. We report the results of a multi-institutional, single arm, phase 2 study evaluating the efficacy and safety of BBBD-enhanced chemotherapy in combination with immunotherapy in patients with newly diagnosed primary central nervous system lymphoma (PCNSL). PCNSL is a rare non-Hodgkin’s lymphoma that is limited to the brain, cerebrospinal fluid, spinal cord and/or the vitreoretinal compartment. Methods: Non-immunocompromised subjects with newly diagnosed PCNSL received rituximab IV over 5 hours on day 1. On days 2 and 3, under general anesthesia in the angiography suite, subjects received IA mannitol immediately followed by IA methotrexate over 10 minutes, and then IA carboplatin over 10 minutes. Subjects received sodium thiosulfate IV for hearing protection at 4 and 8 hours after each carboplatin dose. Treatment was repeated every month for up to 12 courses in the absence of disease progression or unacceptable toxicity. Per institutional recommendations, further accrual was terminated during the COVID-19 pandemic. Contrast MRI was used for response assessment based on IPCG criteria. Results: Twenty subjects (10 F, 10 M, Median KPS = 80; range 40-100) received a median of 8 cycles at 3 US institutions. Sixteen radiographic complete responses (80%) and 1 partial response were documented, 3 subjects were not evaluable (2 withdrew consent and 1 unrelated death). Median PFS was 55.2 months (95% CI :10.3 – not reached) and Median Overall survival was 82.8 months (95% CI :19.8-145.8). Fourteen patients (82% of evaluable patients) had grade 3 or 4 adverse events (AE). Grade 4 AEs (n = 14 in n = 7 patients) included neurologic toxicities (ischemia, cervical cord inflammation, neuropathy) and blood/bone marrow toxicities (lymphopenia, neutropenia, granulocytopenia). There were no treatment-related deaths. Conclusions: We demonstrate the feasibility of performing BBBD in a multi-institutional setting with excellent PFS and OS in patients without whole brain radiation or autologous transplant. Our CR rates, PFS and OS are comparable to other IV high-dose MTX regimens, with acceptable toxicity profile and no documented treatment-related deaths. Clinical trial information: NCT00293475 .

Transient Cortical Blindness Following Cerebral Angiography: A Case Report (P2-5.015)

<h3>Objective:</h3> We would like to report a case of Transient cortical blindness following cerebral angiography <h3>Background:</h3> Transient cortical blindness (TCB) is a rare complication following cerebral angiography. Its pathophysiology remains uncertain. We would like to report a case of TCB in a patient during follow up cerebral angiogram for post coil embolization of left internal carotid aneurysm. <h3>Design/Methods:</h3> 50-year-old woman with history of hypertension presents with bilateral vision loss during follow up cerebral angiography for ruptured left internal carotid artery aneurysm status post coiling. This was associated with headache, nausea, and emesis. No associated neurologic deficits. Review of symptoms was otherwise negative. CT Head and CTA showed no acute abnormalities. MRI done on admission showed no evidence of abnormalities. Ophthalmology saw the patient and exam was unrevealing. After 24 hours her vision gradually improved and was back to baseline after 48 hours with no intervention. <h3>Results:</h3> Transient Cortical Blindness is a rare but dramatic complication of cerebral angiogram. It is characterized by loss of perceived vision, normal fundi, normal papillary reflexes, and intact extraocular movements. Symptoms can occur at the start of the cerebral angiography procedure or until serval hours after. The recovery of normal vision may start within the first few hours, but may take as long as 5 days. Two hypothesis exist: could be due to a neurotoxic effect of contrast agent causing osmotic disruption of blood-brain barrier or could be the result of posterior reversible leukoencephalopathy syndrome leading to perivascular edema. There is no known treatment known to improve the condition. <h3>Conclusions:</h3> In summary, we reported a case of TCB following vertebral angiography, a rare but dramatic complication of cerebral angiography. Radiologists and clinicians should be aware of this complication. When it occurs, one should reassure the patient about the excellent prognosis of this condition. <b>Disclosure:</b> Dr. Gomez has nothing to disclose. Dr. Harris has nothing to disclose.

Determination of brain water content by dry/wet weight measurement for the detection of experimental brain edema.

Brain edema is a fatal pathological state in which brain volume increases as a result of abnormal accumulation of fluid within the brain parenchyma. A key attribute of experimentally induced brain edema - increased brain water content (BWC) - needs to be verified. Various methods are used for this purpose: specific gravimetric technique, electron microscopic examination, magnetic resonance imaging (MRI) and dry/wet weight measurement. In this study, the cohort of 40 rats was divided into one control group (CG) and four experimental groups with 8 rats in each group. The procedure for determining BWC using dry/wet weight measurement was initiated 24 h after the completion of edema induction by the water intoxication method (WI group); after the intraperitoneal administration of Methylprednisolone (MP) together with distilled water during edema induction (WI+MP group); 30 min after osmotic blood brain barrier disruption (BBBd group); after injection of MP via the internal carotid artery immediately after BBBd (BBBd + MP group). While induction of brain edema (WI, BBBd) resulted in significantly higher BWC, there was no increase in BWC in the MP groups (WI+MP, BBBd+MP), suggesting a neuroprotective effect of MP in the development of brain edema.

Safety of intra-arterial chemotherapy with or without osmotic blood-brain barrier disruption for the treatment of patients with brain tumors.

BackgroundIntra-arterial administration of chemotherapy with or without osmotic blood–brain barrier disruption enhances delivery of therapeutic agents to brain tumors. The aim of this study is to evaluate the safety of these procedures.MethodsRetrospectively collected data from a prospective database of consecutive patients with primary and metastatic brain tumors who received intra-arterial chemotherapy without osmotic blood–brain barrier disruption (IA) or intra-arterial chemotherapy with osmotic blood–brain barrier disruption (IA/OBBBD) at Oregon Health and Science University (OHSU) between December 1997 and November 2018 is reported. Chemotherapy-related complications are detailed per Common Terminology Criteria for Adverse Events (CTCAE) guidelines. Procedure-related complications are grouped as major and minor.Results4939 procedures (1102 IA; 3837 IA/OBBBD) were performed on 436 patients with various pathologies (primary central nervous system lymphoma [26.4%], glioblastoma [18.1%], and oligodendroglioma [14.7%]). Major procedure-related complications (IA: 12, 1%; IA/OBBBD: 27, 0.7%; P = .292) occurred in 39 procedures including 3 arterial dissections requiring intervention, 21 symptomatic strokes, 3 myocardial infarctions, 6 cervical cord injuries, and 6 deaths within 3 days. Minor procedure-related complications occurred in 330 procedures (IA: 41, 3.7%; IA/OBBBD: 289, 7.5%; P = .001). Chemotherapy-related complications with a CTCAE attribution and grade higher than 3 was seen in 359 (82.3%) patients.ConclusionsWe provide safety and tolerability data from the largest cohort of consecutive patients who received IA or IA/OBBBD. Our data demonstrate that IA or IA/OBBBD safely enhance drug delivery to brain tumors and brain around the tumor.

Effect of methylprednisolone on experimental brain edema in rats - own experience reviewed.

Brain edema - a frequently fatal pathological state in which brain volume increases resulting in intracranial pressure elevation - can result from almost any insult to the brain, including traumatic brain injury. For many years, the objective of experimental studies was to find a method to prevent the development of brain edema at the onset. From this perspective, the use of methylprednisolone (MP) appears promising. High molecular MP (MW>50 kDa) can be incorporated into the brain - in the conditions of the experimental model - either by osmotic blood-brain barrier disruption (BBBd) or during the induction of cellular edema by water intoxication (WI) - a condition that increases the BBB permeability. The time window for administration of the MP should be at the earliest stages of edema. The neuroprotective effect of MP on the permeability of cytoplasmatic membranes of neuronal populations was proved. MP was administrated in three alternative ways: intraperitoneally during the induction of cytotoxic edema or immediately after finishing cytotoxic edema induction in a dose of 100 mg/kg b.w.; into the internal carotid artery within 2 h after finishing cytotoxic edema induction in a dose of 50 mg/kg b.w.; into internal carotid artery 10 min after edema induction by BBBd in a dose of 50 mg/kg b.w.

Management of Primary Central Nervous System Lymphoma Using Intra-Arterial Chemotherapy With Osmotic Blood-Brain Barrier Disruption: Retrospective Analysis of the Sherbrooke Cohort

BackgroundPrimary central nervous system lymphomas (PCNSL) are rare and aggressive CNS tumors. Current management involves high-dose methotrexate (HD-MTX) typically administered intravenously (IV), despite the existence of the blood-brain barrier (BBB), which significantly decreases its bioavailability. Cerebral intra-arterial chemotherapy (CIAC) coupled with osmotic BBB disruption (OBBBD) can theoretically circumvent this issue.MethodsWe performed a retrospective analysis of patients with newly diagnosed PCNSL treated with HD-MTX-based CIAC+OBBBD at our center between November 1999 and May 2018. OBBBD was achieved using a 25% mannitol intra-arterial infusion. Patients were followed clinically and radiologically every month until death or remission. Demographics, clinical and outcome data were collected from the medical record. All imaging studies were reviewed for evidence of complication and outcome assessment. Kaplan-Meier analyses were used to compute remission, progression-free survival (PFS) as well as overall survival times. Subgroup analyses were performed using the log rank test.ResultsForty-four patients were included in the cohort. Median follow-up was 38 months. Complete response was achieved in 34 patients (79%) at a median of 7.3 months. Actuarial median survival and PFS were 45 months and 24 months, respectively. Age, ECOG and lesion location did not impact outcome. Complications included thrombocytopenia (39%), neutropenia (20%), anemia (5%), seizures (11%), stroke (2%), and others (20%).ConclusionCIAC using HD-MTX-based protocols with OBBBD is a safe and well-tolerated procedure for the management of PCNSL. Our data suggests better PFS and survival outcomes compared to IV protocols with less hematologic toxicity and good tolerability, especially in the elderly.

SURG-42. SAFETY OF INTRA-ARTERIAL CHEMOTHERAPY WITH OR WITHOUT OSMOTIC BLOOD BRAIN BARRIER DISRUPTION IN TREATMENT OF BRAIN TUMORS

Abstract BACKGROUND Intra-arterial route of drug delivery (IA) without or with osmotic blood brain barrier disruption (IA/BBBD) is one of the available techniques to overcome the blood-brain barrier and enhance drug delivery to brain tumors. We present a large single institution safety data of IA or IA/BBBD. METHODS This is a retrospective review of the electronic records, imaging and complications in patients who underwent IA or IA/BBBD in OHSU between December, 1997 and November, 2018. Procedural complications were documented prospectively and reviewed in the electronic medical records. Toxicities, attributed to chemotherapy, were reported when grade is either II or higher by Common Terminology Criteria for Adverse Events (CTCAE). RESULTS Complications related to chemotherapy and procedure were reported separately. Total of 4940 procedures (1102 IAC and 3838 oBBBD) were performed on 436 patients (190 female and 246 male). Pathologies were primary central nervous system lymphoma (PCNSL) (n=115, 26%), secondary central nervous system involvement (SCNSL) (n=37, 8%), glioblastoma (n=79, 18%), astrocytoma (grade II/III) (n=34, 7%), oligodendroglioma (n=64, 14%), pilocytic astrocytoma (n=10, 2%), metastatic (n=38, 8%), embryologic (n=37, 8%), others (n=22, 5%). Procedural complications: groin related (n=16, 0.32%), transient neurological decline (n=57, 1.15%), subintimal arterial injury (n=13, 0.26%), asymptomatic imaging changes (T2 or DWI) (n=60, 1.21%), symptomatic stroke (n=21, 0.43%), myocardial infarction (n=3, 0.37%), cervical cord injury (n=6, 0.12%), death within 3 days (n=6, 0.12%). Minor complications are 2.86%, major complications are 1.12%. Eighty-four percent (n=369) of the patients experienced grade 2 or higher toxicities attributed to chemotherapy. CONCLUSION We present the largest safety data set to date from a single institution experience using IA and IA/BBBD for brain tumors. Our results suggest that IA and IA/BBBD is safe and can be performed multiple times in the same patients with acceptable procedure related complications. Efficacy of this approach is being evaluated in prospective clinical trials.

P14.84 Intraarterial chemotherapy and osmotic blood-brain barrier modification in the treatment of primary CNS lymphoma

Abstract BACKGROUND Primary central nervous system lymphomas (PCNSL) are considered a rare and aggressive form of central nervous system (CNS) tumors. High-dose methotrexate has become the backbone of PCNSL treatment, and is recommended by the EANO guidelines. In most recent protocols, investigators tend to postpone or even avoid the use of radiotherapy; indeed, its use has become controversial with findings of associated severe neuro-toxicity, especially in elderly patients. To maximize delivery across the BBB, we use cerebral intra-arterial chemotherapy (CIAC) coupled with osmotic blood-brain barrier disruption (OBBBD). We hereby report our single-center experience over 18 years with the CIAC + BBBD technique using 2 different HD-MTX protocols. MATERIAL AND METHODS This phase II study was conducted at the Centre hospitalier Universitaire de Sherbrooke (CHUS) from November 1999 to May 2018. The protocol was approved by the institutional review board, and informed consent was obtained in accordance to institutional regulation in every patient After enrollment and initial evaluation, patients were treated every four weeks (1 cycle) for 12 cycles, unless progression. After general anesthesia, a transfemoral approach was used to catheterize either the right or left internal carotid artery or the dominant vertebral artery, depending on tumor(s) location. OBBBD was performed by infusing 20% mannitol in the selected vascular distribution for 30 seconds at a rate that fills the vascular distribution so as to maximize the contact of the mannitol with the endothelial cells.Two different chemotherapy regimens were sequentially used in this study. High-dose MTX (5 g IV) was the cornerstone of both regimens: the first regimen (1999 to 2007) also included etoposide phosphate IV (400 mg/m²) and cyclophosphamide IV (660 mg/m²), whereas the 2nd regimen (1998 to 2018) also included carboplatin IA (400 mg/m²). RESULTS The present analysis therefore concerns a cohort of 44 naive patients recruited over 18 years in a single center. Median follow-up was 38 months. Overall, a CR was induced in 34 patients (79%). Themedian time to CR was 7.3 months (IQR: 7.8). Of these 34 patients, 11 (25.6%) are still alive, and 9 of these are disease-free after treatment discontinuation. The actuarial median survival (MS) was 46.5 months (95% CI: 30.9–62.2) for the cohort. Survival was 88%, 64%, 54%, 39% and 18% at 1, 2, 3,5 and 10 years (Figure 1 and Table 2).The progression-free survival was 43.4 months (95% CI: 17.9–68.9). Five occurrences of vascular complications related to the treatment were observed (11.6%). Conclusion: CIAC HD-MTX-based protocols with OBBBD is a safe and well-tolerated procedure for the management of primary CNS lymphoma. Our single center data suggests better PFS and survival outcomes compared to IV protocols with less hematologic toxicity and good tolerability, especially in the elderly.

THER-04. THE USE OF AN ADENOSINE A2 AGONIST TO IMPROVE THE PREVENTION AND TREATMENT OF BRAIN METASTASES

As systemic therapies for cancer become increasingly effective, there is generally a rise in the incidence of brain metastases as a site of first recurrence. This occurs because most antineoplastic agents do not reach the brain in therapeutic concentrations. Many approaches have been studied to improve drug distribution to the central nervous system (CNS) such as intra-arterial administration, osmotic blood-brain barrier (BBB) disruption, focused ultrasound, convection-enhanced delivery, development of CNS penetrant pro-drugs, and the use of vasoactive peptides to transiently disrupt the BBB. However, none of these has improved the prevention or treatment of CNS metastases. Regadenoson is an adenosine A2 agonist that is FDA approved for use in cardiac stress tests. In animals, it has been shown to transiently increase BBB permeability allowing high molecular weight dextran and chemotherapy to enter brain in higher concentrations. A clinical study designed to determine if regadenoson will perform similarly in humans has been CTEP approved and will soon be accruing patients through the Adult Brain Tumor Consortium. If the results are encouraging, future studies will focus on administering regadenoson concurrently with systemically administered chemotherapy in an effort to reduce the incidence of CNS metastases and to improve CNS drug delivery in patients with known brain metastases. This presentation will focus on the available pre-clinical and clinical data supporting this approach and the potential advantages and risks associated with transient BBB disruption in this setting.

Vascular delivery of intraperitoneal Evans blue dye into the blood-brain barrier-intact and disrupted rat brains.

Blood-brain barrier (BBB) integrity can be determined by tracer infusion into the circulation followed by measurements of its penetration into the brain parenchyma. Tracer injection through the intraperitoneal (i.p.) route (rather than intravascular injection) avoids confounding effects of animal anesthesia or immobilization/surgical stress. Evans blue dye (EBD) can be administered by i.p. injection, and once in circulation, it binds to plasma albumin to become an endogenous protein tracer. Here, we investigated whether a similar level of EBD is extravasated into the brain following i.p. versus intravenous (i.v.) injection in rats. In comparison with i.v. EBD injection, i.p. EBD injection resulted in much of the tracer residing in the peritoneal cavity. Accordingly, comparatively less EBD was found in the blood, liver, or brain of BBB-intact rat. In addition, following unilateral osmotic BBB disruption, i.v. but not i.p. EBD stained the ipsilateral hemisphere blue. Nevertheless, following either route of tracer administration in these rats, spectrophotometric quantification detected more EBD in the ipsilateral (BBB-disrupted) than in the contralateral hemisphere. Taken together, in contrast to a recent report, we found that i.p. EBD resulted in less tracer in circulation and in peripheral/central organs than EBD delivered i.v. We nevertheless conclude that i.p. EBD delivered sufficient tracer for the detection of regional BBB disruption.

Safety of intra-arterial chemotherapy with osmotic opening of the blood brain barrier.

e14056Background: Osmotic blood brain barrier disruption (BBBD) can increase drug delivery up to 100 fold in brain tumors when compared to IV delivery. The aim of this study was to evaluate the saf...

Intra-arterial Temozolomide, Osmotic Blood-brain Barrier Disruption and Radiotherapy in a Rat F98-Glioma Model

Background: The blood-brain barrier (BBB) is a major obstacle in the treatment of brain tumors. Intra-arterial (IA) administration with osmotic BBB disruption (BBBD) allows greater drug delivery to the central nervous system (CNS). Its use with temozolomide (TMZ), the first-line agent in the treatment of glioblastoma, has never been reported in an animal glioma model. Objective: This study was designed to investigate whether increased TMZ delivery would improve survival in the Fischer-F98 glioma model. Methods: Alternative methods of administration for TMZ (200 mg/m2) were tested, comparing intravenous infusions (IV, n=13) to IA (n=13) or BBBD with IA (n=13). IA normal saline (NS) was used as a control group (n=13). Five rats per group also underwent radiotherapy. Survival and adverse effects were measured. TMZ was quantified in plasma, CSF and brain at three time-points post-TMZ infusion (IV, IA or IA+BBBD) by LC-MS\MS. Results: Compared to IV, higher peak TMZ concentrations were observed in brain tumor (BT) tissues with IA and IA+BBBD infusions (4-fold and 5-fold, respectively). No difference in survival was observed between the IA with/without BBBD vs. IV/control groups. Radiotherapy increased survival independently of the method of TMZ delivery. Conclusion: We show that the enhanced delivery of TMZ by IA infusion (with/without BBBD) does not improve survival in this resistant model. However, the method of TMZ administration has a significant impact on CNS delivery. Bypassing the BBB with judicious use of local delivery approaches and appropriate therapeutic agents has potential for the treatment of glioblastomas. Keywords: Blood-brain barrier, Blood-brain barrier disruption, Drug delivery, F98 cells, Glioblastoma multiforme, Temozolomide.

Abstract B38: Radiation enhances intracellular delivery of anti-MGMT oligomers to reduce protein expression in vitro and in a xenograft model

Abstract High levels of DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) in glioblastoma tumor are associated with temozolomide resistance and poor prognosis. MGMT provides a promising therapeutic target to overcome chemo-resistance and improve overall survival in cancer patients. In this study, we investigate the enhanced delivery of anti-MGMT morpholino oligonucleotide (AMON) using a sub-therapeutic dose of radiation to reduce MGMT expression of human cancer cells (T98G glioma and H460 and A549 non-small cell lung carcinoma) in vitro and in vivo. Compared to standard transfection techniques, sub-therapeutic dose of radiation enhanced intracellular AMON delivery and transiently reduced MGMT protein expression at 3 d in vitro. The optimal radiation dosage was cancer cell type dependent and ranged from 1-12 Gy. In addition, AMON delivered using sub-therapeutic dose of radiation increased cytotoxicity of T98G cells in response to temozolomide compared to radiation and temozolomide alone in vitro. In a H460 subcutaneous xenograft tumor model, intravenous AMON administration reduced MGMT protein level by 50% in irradiated tumors but not in contralateral non-irradiated lesions within the same animal. Tumor MGMT protein downregulation by AMON did not alter DNA promoter methylation status. Our results demonstrate for the first time the use of radiation to enhance the intracellular delivery of antisense oligonucleotides to modulate MGMT protein expression in vitro and in vivo. We have previously shown that antisense nucleotides can be delivered to the brain parenchyma using osmotic blood brain barrier disruption. Therefore, we believe that cancer patients with MGMT overexpression, unmethylated DNA promoter and/or resistance to DNA alkylating agents may benefit from this novel antisense therapeutic technology to improve overall survival. Citation Format: Jeffrey Wu, Prakash Ambady, DreeAnna Morris, Michael Pagel, Randy Woltjer, Joshua Walker, Leslie Muldoon, Edward Neuwelt. Radiation enhances intracellular delivery of anti-MGMT oligomers to reduce protein expression in vitro and in a xenograft model [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr B38.

Superselective intraarterial cerebral infusion of cetuximab after osmotic blood/brain barrier disruption for recurrent malignant glioma: phase I study

Objective To establish a maximum tolerated dose of superselective intraarterial cerebral infusion (SIACI) of Cetuximab after osmotic disruption of the blood-brain barrier (BBB) with mannitol, and examine safety of the procedure in patients with recurrent malignant glioma. MethodsA total of 15 patients with recurrent malignant glioma were included in the current study. The starting dose of Cetuximab was 100mg/m(2) and dose escalation was done to 250mg/m(2). All patients were observed for 28days post-infusion for any side effects. ResultsThere was no dose-limiting toxicity from a single dose of SIACI of Cetuximab up to 250mg/m(2) after osmotic BBB disruption with mannitol. A tolerable rash was seen in 2 patients, anaphylaxis in 1 patient, isolated seizure in 1 patient, and seizure and cerebral edema in 1 patient. DiscussionSIACI of mannitol followed by Cetuximab (up to 250mg/m(2)) for recurrent malignant glioma is safe and well tolerated. A Phase I/II trial is currently underway to determine the efficacy of SIACI of cetuximab in patients with high-grade glioma.

Chemotherapy Delivery Strategies to the Central Nervous System: neither Optional nor Superfluous.

Malignant brain tumors including primary brain tumors (e.g., glioblastoma multiforme) and metastases, are aggressive and lethal entities for the majority of affected patients. Current standard treatments involving combinations of surgery, radiotherapy and systemic chemotherapy offer only modest improvements in survival. Faced with dismal survival, great efforts are deployed to find interesting treatment alternatives. However, the blood-brain barrier (BBB) and the blood-tumor barrier (BTB) remain great obstacles to significant drug delivery to brain tumors. The need to optimize delivery strategies for better patient outcome in the treatment of malignant brain tumors is well acknowledged. Certain interesting strategies use surgical or physical techniques to enhance the distribution of therapeutic agents to the central nervous system. The following strategies will be discussed in this review: intra-arterial delivery, osmotic BBB disruption, intranasal delivery, convection-enhanced delivery and osmotic pumps, implanted polymers, magnetic microspheres and ultrasound BBB disruption. The purpose of this paper is to review the importance of the BBB and the BTB and to review the current status and future perspectives of these delivery procedures.

ATPS-57INTRA-ARTERIAL ADMINISTRATION IMPROVES TEMOZOLOMIDE DELIVERY AND EFFICACY IN A MODEL OF INTRACEREBRAL METASTASIS, BUT HAS UNEXPECTED BRAIN TOXICITY

We tested the hypothesis that intra-arterial (IA) infusion of temozolomide into the internal carotid artery would safely improve drug delivery to brain and enhance chemotherapy efficacy in a chemosensitive rat brain tumor model. Quantitative autoradiography after 25 µCi 14C-temozolomide was given by oral, intravenous, or IA route of administration, or IA with osmotic blood-brain barrier disruption (BBBD) (n = 5-7 per group) showed that both IA and IA/BBBD administration increased drug delivery in tumor by over 3-fold compared to normal brain (P < 0.02), and also significantly elevated delivery throughout the infused right hemisphere. Temozolomide (20 mg/kg; ∼150 mg/m2) increased median survival when given by oral (25.5 days), intravenous (25.5 days), or IA (33 days) route of administration, compared to 17.5 days in untreated controls (n = 8 per group; overall P < 0.0001). Survival time after IA temozolomide was significantly longer than all other groups (P < 0.01 for all comparisons). BBBD temozolomide was toxic in the efficacy study, but there was no evidence of symptomatic neurotoxicity in rats given IA temozolomide. After these promising animal results, a 49 year old male with glioblastoma multiforme who failed all standard therapy received temozolomide 100 mg/m2 IA. Upon initiation of the second course of IA infusion the patient had increased heart rate, blood pressure, and rash, and the procedure was terminated without sequelae. Follow up IA infusion of temozolomide diluent in normal rats showed damaged cerebrovasculature as determined by dye leakage. We conclude that under the current formulation temozolomide is not safe for IA infusion.

Overcoming the blood-brain tumor barrier for effective glioblastoma treatment.

Gliomas are the most common primary brain tumors. Particularly in adult patients, the vast majority of gliomas belongs to the heterogeneous group of diffuse gliomas, i.e. glial tumors characterized by diffuse infiltrative growth in the preexistent brain tissue. Unfortunately, glioblastoma, the most aggressive (WHO grade IV) diffuse glioma is also by far the most frequent one. After standard treatment, the 2-year overall survival of glioblastoma patients is approximately only 25%. Advanced knowledge in the molecular pathology underlying malignant transformation has offered new handles and better treatments for several cancer types. Unfortunately, glioblastoma multiforme (GBM) patients have not yet profited as although numerous experimental drugs have been tested in clinical trials, all failed miserably. This grim prognosis for GBM is at least partly due to the lack of successful drug delivery across the blood-brain tumor barrier (BBTB). The human brain comprises over 100 billion capillaries with a total length of 400 miles, a total surface area of 20 m(2) and a median inter-capillary distance of about 50 μm, making it the best perfused organ in the body. The BBTB encompasses existing and newly formed blood vessels that contribute to the delivery of nutrients and oxygen to the tumor and facilitate glioma cell migration to other parts of the brain. The high metabolic demands of high-grade glioma create hypoxic areas that trigger increased expression of VEGF and angiogenesis, leading to the formation of abnormal vessels and a dysfunctional BBTB. Even though the BBTB is considered 'leaky' in the core part of glioblastomas, in large parts of glioblastomas and, even more so, in lower grade diffuse gliomas the BBTB more closely resembles the intact blood-brain barrier (BBB) and prevents efficient passage of cancer therapeutics, including small molecules and antibodies. Thus, many drugs can still be blocked from reaching the many infiltrative glioblastoma cells that demonstrate 'within-organ-metastasis' away from the core part to brain areas displaying a more organized and less leaky BBTB. Hence, drug delivery in glioblastoma deserves explicit attention as otherwise new experimental therapies will continue to fail. In the current review we highlight different aspects of the BBTB in glioma patients and preclinical models and discuss the advantages and drawbacks of drug delivery approaches for the treatment of glioma patients. We provide an overview on methods to overcome the BBTB, including osmotic blood-brain barrier disruption (BBBD), bradykinin receptor-mediated BBTB opening, inhibition of multidrug efflux transporters, receptor-mediated transport systems and physiological circumvention of the BBTB. While our knowledge about the molecular biology of glioma cells is rapidly expanding and is, to some extent, already assisting us in the design of tumor-tailored therapeutics, we are still struggling to develop modalities to expose the entire tumor to such therapeutics at pharmacologically meaningful quantities. Therefore, we must expand our knowledge about the fundamentals of the BBTB as a step toward the design of practical and safe devices and approaches for enhanced drug delivery into the diseased brain area.

CT imaging and spontaneous behavior analysis after osmotic blood-brain barrier opening in Wistar rat.

In our previous experiments we demonstrated that osmotic opening of the blood brain barrier (BBB) in rats by administration of mannitol into the internal carotid artery leads to cerebral edema. The aim of this study was to confirm objectively the development of brain edema and determine whether it affects spontaneous locomotor activity in rats (SLA). Brain edema was verified by computer tomography (CT) examination of the brain and SLA was observed during open field test. Twenty four adult male rats were divided into four groups of six: (1) control animals (C), (2) controls with anesthesia (CA), (3) controls with sham surgery (CS), (4) experimental - osmotic opening of the BBB (MA). Osmotic BBB disruption manifested by reducing the density of brain tissue (hypodensity), suggesting a higher water content in the brain tissue. SLA was compared between C, CA, CS and MA groups and between MA and CA groups. Significant difference was found only between the control group and MA group. In the first 30 min of the examination, rats after the mannitol administration revealed a marked limitation of spontaneous locomotor activity. Experimental results demonstrated reduction of spontaneous locomotor activity in rats with induced brain edema.

ET-07 * DOES OSMOTIC BLOOD-BRAIN BARRIER DISRUPTION ALLOWS EFFLUX PUMP SUBSTRATES DELIVERY TO THE TUMOR AND CNS?

Despite decades of research, the median survival of glioblastoma (GBM) patients remains 14.6 months. The presence of the blood-brain barrier (BBB) limits CNS antineoplastic drugs delivery. Many BBB characteristics are involved in the drug delivery limitation, amongst them the efflux pumps. Different delivery strategies, such as the osmotic blood-brain barrier disruption (BBBD) have been developed and used with success in GBM patients. In order to enhance BBBD efficacy, more information is needed about its dynamic process. The aim of this study was to determine if the BBBD procedure can enable the delivery of efflux pump substrates to brain parenchyma and glioma cells. Thirty-two F98-Fischer rats were randomly assigned to 6 groups: 1: control; 2: tariquidar (P-glycoprotein (PGP) inhibitor); 3: BBBD in tumor ipsilateral hemisphere; 4: tariquidar vehicle (n = 3); 5: BBBD negative control (n = 3); and 6: BBBD + tariquidar. An MRI scan was performed to allow PET-MRI images coregistration. A 1-h dynamic PET acquisition was obtained and, with 11C-Carvedilol (a PGP substrate) administered iv during the first minute of the scan. Four volumes of interest (VOI) were studied: tumor volume, distal volume to the tumor in the ipsilateral parenchyma and equivalent control VOIs in the contralateral hemisphere. 11C-Carvedilol uptake ratios of corresponding ipsilateral and contralateral VOIs were computed for every animal. 11C-Carvedilol uptake in tumors was significantly higher on average in tariquidar and BBBD + tariquidar groups compared to the control groups. When comparing 11C-Carvedilol uptake in parenchyma, there was no significant difference between the groups at study. However, only two out of six animals in the BBBD + tariquidar group did show higher 11C-Carvedilol uptake, indicating that the BBBD must be excellent for effective substrate delivery to CNS. These results demonstrate that the BBBD procedure does not allow significant delivery of efflux pump substrates to the CNS, unless excellent BBBD procedure is achieved.

The effect of intra-arterial delivery of temozolomide with or without osmotic blood-brain barrier disruption and combined to radiotherapy

The effect of intra-arterial delivery of temozolomide with or without osmotic blood-brain barrier disruption and combined to radiotherapy