Current strategies for targeted delivery of bio-active drug molecules in the treatment of brain tumor

Brain tumor is one of the most challenging diseases to treat. The major obstacle in the specific drug delivery to brain is blood-brain barrier (BBB). Mostly available anti-cancer drugs are large hydrophobic molecules which have limited permeability via BBB. Therefore, it is clear that the protective barriers confining the passage of the foreign particles into the brain are the main impediment for the brain drug delivery. Hence, the major challenge in drug development and delivery for the neurological diseases is to design non-invasive nanocarrier systems that can assist controlled and targeted drug delivery to the specific regions of the brain. In this review article, our major focus to treat brain tumor by study numerous strategies includes intracerebral implants, BBB disruption, intraventricular infusion, convection-enhanced delivery, intra-arterial drug delivery, intrathecal drug delivery, injection, catheters, pumps, microdialysis, RNA interference, antisense therapy, gene therapy, monoclonal/cationic antibodies conjugate, endogenous transporters, lipophilic analogues, prodrugs, efflux transporters, direct conjugation of antitumor drugs, direct targeting of liposomes, nanoparticles, solid-lipid nanoparticles, polymeric micelles, dendrimers and albumin-based drug carriers.

Drug delivery to brain tumors

A prerequisite for the efficacy of any cancer drug is that it reaches the tumor in therapeutic concentrations. This is difficult to accomplish in most systemic solid tumors because of factors such as variable hypoxia, intratumoral pressure gradients, and abnormal vasculature within the tumors. In brain cancer, the situation is complicated by the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier, which serve as physical and physiologic obstacles for delivery of drugs to the central nervous system. Many approaches to overcome, circumvent, disrupt, or manipulate the BBB to enhance delivery of drugs to brain tumors have been devised and are in active investigation. These approaches include high-dose intravenous chemotherapy, intra-arterial drug delivery, local drug delivery via implanted polymers or catheters, BBB disruption, and biochemical modulation of drugs.

Strategies to advance translational research into brain barriers

There is a paucity of therapies for most neurological disorders--from rare lysosomal storage diseases to major public health concerns such as stroke and Alzheimer's disease. Advances in the targeting of drugs to the CNS are essential for the future success of neurotherapeutics; however, the delivery of many potentially therapeutic and diagnostic compounds to specific areas of the brain is restricted by the blood-brain barrier, the blood-CSF barrier, or other specialised CNS barriers. These brain barriers are now recognised as a major obstacle to the treatment of most brain disorders. The challenge to deliver therapies to the CNS is formidable, and the solution will require concerted international efforts among academia, government, and industry. At a recent meeting of expert panels, essential and high-priority recommendations to propel brain barrier research forward in six topical areas were developed and these recommendations are presented here.

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.

Treatment of CNS dissemination in systemic lymphoma

The frequency of central nervous system (CNS) dissemination in non-Hodgkin's lymphoma (NHL) varies and is dependent on NHL histology. More than 50% of patients with CNS involvement have advanced and progressive systemic disease. While CNS involvement at initial diagnosis may be treated curatively, treatment of CNS involvement in systemic relapsing or refractory lymphoma is challenging and most often palliative. Due to a paucity of randomized trials, treatment of lymphomatous metastases is not standardized. Nonetheless, treatment of LM entails administration of both CNS-directed and systemic chemotherapy that often includes high-dose chemotherapy regimens with stem cell support.