Researchers Move Small Molecule Drugs Through Blood Brain Barrier

Researchers at Mayo Clinic have demonstrated in a mouse model that their recently developed synthetic peptide carrier is a potential delivery vehicle for brain cancer chemotherapy drugs and other neurological medications. The findings appear in PLOS ONE.

“Not only have we shown that we can transport eight different molecules, we think this method will be less disruptive or invasive because it mimics a normal physiological process,” says Mayo Clinic neuroscientist Gobinda Sarkar, Ph.D., the corresponding author of the study. The researchers are able to transport the drugs without modifying any of the molecules involved. They say this development will aid in evaluation of potential new drugs for brain cancer.

The blood-brain barrier is meant to protect the brain from numerous undesirable chemicals circulating in the body, but it also obstructs access for treatment of brain tumors and other conditions. Too often the only recourse is invasive, which often limits a drug’s effectiveness or causes irreversible damage to an already damaged brain. Nearly all of the drugs that could potentially help are too large to normally pass through the barrier. Additionally, other methods may damage the vascular system.

This image shows three different examples of the brains used in the experiment. The caption best describes the image.

K16ApoE-mediated brain delivery of blue (EB), red (Crocein Scarlet) and green (Light Green SF) dyes to the brain. Three different approaches were assessed for dye delivery: 1. K16ApoE was injected first then a given dye was injected 10 min after (second columns of brain specimens); 2. K16ApoE was mixed with 300 ug of cetuximab and injected followed by injection of a given dye 10 min after 3rd column of brain specimens), and 3. K16ApoE and the dyes were mixed and injected (fourth column of brain specimens). The first column of brain specimens represents animals receiving injection of a given dye alone. Mice were perfused with saline 2 h after injection and then brains were collected for visualization. 67.5 picomole of K16ApoE was used in each experiment. 40 ul of a 2% solution of each of the dyes were used for injection into a 20 g mouse (amount of dye injected varied accordingly with weight of mice). Credit Jenkins et al./PLOS ONE.

In this case, the synthetic peptide K16ApoE, once injected into a vein, binds to proteins in the blood to create entities that can pass for near-normal ligands to some receptors present on the blood-brain barrier. The ‘pseudo-ligand’ receptor interaction creates what the researchers believe to be transient pores through which various molecules can be transported to the brain. The molecules they’ve transported in this manner include cisplatin, methotrexate, cetuximab, three different dyes, and synthetic peptides Y8 and I-125. The researchers believe this is the least complicated, least expensive and most versatile method for delivering therapeutics to the brain. Previously, the researchers delivered antibodies targeted against amyloid plaques into the brains of mouse models of Alzheimer’s disease using this same method.

“We know that some chemotherapeutic agents can kill brain tumor cells when they are outside the brain (as in a laboratory test). But because the agents cannot cross the blood-brain barrier, they are not able to kill brain tumor cells inside the brain. With the peptide carrier, these agents can now get into the brain and potentially kill the tumor cells,” says Mayo neurology researcher Robert Jenkins, M.D., Ph.D., senior author of the study.

The researchers say their method, which has been successfully demonstrated in mice, meets three of five requirements for a usable therapy: It’s feasible as a repeated procedure; it should be relatively easy to introduce into medical practice; and it would work for any size or location of brain tumor. More research will need to be done to prove effectiveness and determine any adverse effects.

Notes about this neuroscience research

The research was supported by Mayo Clinic, Bernie and Edith Waterman, and the Ting Tsung and Wei Fong Chao Family Foundation. Co-authors include Geoffry Curran, Jann Sarkaria, M.D., and Val Lowe, M.D., all of Mayo Clinic.

Contact: Bob Nellis – Mayo Clinic
Source: Mayo Clinic press release
Image Source: The image is credited to Jenkins et al./PLOS ONE and is adapted from the open access research paper
Original Research: Full open access research for “Peptide Carrier-Mediated Non-Covalent Delivery of Unmodified Cisplatin, Methotrexate and Other Agents via Intravenous Route to the Brain” by Gobinda Sarkar, Geoffry L. Curran, Jann N. Sarkaria, Val J. Lowe, and Robert B. Jenkins in PLOS ONE. Published online May 21 2014 doi:10.1371/journal.pone.0097655

Open Access Neuroscience Abstract

Peptide Carrier-Mediated Non-Covalent Delivery of Unmodified Cisplatin, Methotrexate and Other Agents via Intravenous Route to the Brain

Rapid pre-clinical evaluation of chemotherapeutic agents against brain cancers and other neurological disorders remains largely unattained due to the presence of the blood-brain barrier (BBB), which limits transport of most therapeutic compounds to the brain. A synthetic peptide carrier, K16ApoE, was previously developed that enabled transport of target proteins to the brain by mimicking a ligand-receptor system. The peptide carrier was found to generate transient BBB permeability, which was utilized for non-covalent delivery of cisplatin, methotrexate and other compounds to the brain.

“Peptide Carrier-Mediated Non-Covalent Delivery of Unmodified Cisplatin, Methotrexate and Other Agents via Intravenous Route to the Brain” by Gobinda Sarkar, Geoffry L. Curran, Jann N. Sarkaria, Val J. Lowe, and Robert B. Jenkins in PLOS ONE, May 21 2014 doi:10.1371/journal.pone.0097655

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