The blood-brain barrier blocks the entry of antibodies into the brain. This limits the potential use of antibody therapeutics to treat brain diseases, such as brain tumors.
In a new study published in the journal Frontiers in Cell and Developmental Biology, researchers at the University of Alabama at Birmingham report that the site-directed addition of an FDA-approved, biodegradable polymer at the hinge and near hinge regions of the therapeutic antibody trastuzumab effectively facilitated the brain delivery of this human monoclonal IgG1 antibody. Trastuzumab is used to treat breast cancer and several other cancers.
Preliminary work on this novel platform included in vitro and mouse-model experiments. Researchers say the delivery system still must be optimized and tested further, yet note their simple methodology converts antibody therapeutics to a brain-deliverable form that maintains the antibody’s medical functionality.
“The concerns of brain-entry haunt the development of brain-disease-targeting antibody therapeutics, impeding the medical translations of laboratory-generated antibodies to clinical practices,” said Masakazu Kamata, Ph.D., leader of the study and an associate professor in the UAB Department of Microbiology. “In this context, this simple methodology has great potential to serve as the platform to not only repurpose the current antibody therapeutics, but also encourage the design of novel antibodies, for the treatment of brain diseases.”
The biocompatible polymer used was poly 2-methacryloyloxyethyl phosphorylcholine, or PMPC, with chain lengths of 50, 100 or 200 monomers. The researchers had already discovered that this non-immunogenic polymer, which the FDA has approved as a coating material for transplantable devices, could bind to two receptors on brain microvascular endothelial cells composing the blood-brain barrier, and those cells could then move the polymer across the blood-brain barrier by transcytosis. Transcytosis is a specialized transport whereby extracellular cargo is brought inside the cell, shuttled across the cytoplasm to the other side of the cell, and then released.
The UAB researchers were able to cleave four interchain disulfide bonds in the trastuzumab IgG1 hinge and near hinge regions, creating thiol groups. Each thiol group was then conjugated to a chain of the PMPC to create trastuzumab molecules with one of the three chain lengths, which they denoted as Tmab-PMPC50, Tmab-PMPC100 and Tmab-PMPC200.
Each of these modified antibodies still maintained trastuzumab-specific binding to cells expressing the HER2 antigen, the target of trastuzumab. Both the Tmab-PMPC50 and the Tmab-PMPC100 were internalized into HER2-positive cells and promoted antibody-dependent cell death, which is the medical functionality by which trastuzumab kills HER2+ breast cancer cells.
The researchers then showed that PMPC conjugation of trastuzumab enhanced blood-brain barrier penetration through the epithelial cells on the blood-brain barrier via the transcytosis pathway. The translocatable Tmab-PMPC100 was the best at efficient blood-brain barrier penetration while retaining trastuzumab’s epitope recognition, the ability of the antibody to bind to its antigen target.
In a mouse model, both Tmab-PMPC100 and Tmab-PMPC200 were about fivefold better at brain penetration than native trastuzumab. In preliminary in vitro and mouse-model experiments, the polymer-modified trastuzumab did not induce neurotoxicity, did not show adverse effects in the liver, and did not disrupt the integrity of the blood-brain barrier.
“Those findings collectively indicate that PMPC conjugation achieves effective brain delivery of therapeutic antibodies, such as trastuzumab, without induction of adverse effects, at least in the liver, the blood-brain barrier or the brain,” Kamata said.
Others have also investigated ways to get cargo like antibodies across the blood-brain barrier, the researchers noted.
In work that led to the current study, the UAB researchers for the current study had shown they could wrap various macromolecular cargos within PMPC shells, and these nanocapsules demonstrated prolonged blood circulation, reduced immunogenicity and enhanced brain delivery in mice and non-human primates.
Yet this system had drawbacks. The nanocapsules required the addition of targeting ligands to bring them to their disease target and degradable crosslinkers that would allow release of the cargo at that site. Unfortunately, disease-associated microenvironments often lack conditions that can trigger degradation of the crosslinkers.
Other researchers seeking to breach the blood-brain barrier have investigated various ligands other than PMPC to boost transport, such as ligands derived from microbes and toxins, or endogenous proteins like lipoproteins. These generally have had undesirable surface properties—such as being highly immunogenic, highly hydrophobic or charged. PMPC does not exhibit those undesirable traits.
Co-authors with Kamata in the study, “Site-oriented conjugation of poly(2-methacryloyloxyethyl phosphorylcholine) for enhanced brain delivery of antibody,” are Jie Ren, Chloe E. Jepson, Charles J. Kuhlmann, Stella Uloma Azolibe and Madison T. Blucas, UAB Department of Microbiology; Sarah L. Nealy and Eugenia Kharlampieva, UAB Department of Chemistry; Satoru Osuka, UAB Department of Neurosurgery; and Yoshiko Nagaoka-Kamata, UAB Department of Pathology.
More information: Jie Ren et al, Site-oriented conjugation of poly(2-methacryloyloxyethyl phosphorylcholine) for enhanced brain delivery of antibody, Frontiers in Cell and Developmental Biology (2023). DOI: 10.3389/fcell.2023.1214118
News
These two viruses may become the next public health threats, scientists say
Two emerging pathogens with animal origins—influenza D virus and canine coronavirus—have so far been quietly flying under the radar, but researchers warn conditions are ripe for the viruses to spread more widely among humans. [...]
COVID-19 viral fragments shown to target and kill specific immune cells
COVID-19 viral fragments shown to target and kill specific immune cells in UCLA-led study Clues about extreme cases and omicron’s effects come from a cross-disciplinary international research team New research shows that after the [...]
Smaller Than a Grain of Salt: Engineers Create the World’s Tiniest Wireless Brain Implant
A salt-grain-sized neural implant can record and transmit brain activity wirelessly for extended periods. Researchers at Cornell University, working with collaborators, have created an extremely small neural implant that can sit on a grain of [...]
Scientists Develop a New Way To See Inside the Human Body Using 3D Color Imaging
A newly developed imaging method blends ultrasound and photoacoustics to capture both tissue structure and blood-vessel function in 3D. By blending two powerful imaging methods, researchers from Caltech and USC have developed a new way to [...]
Brain waves could help paralyzed patients move again
People with spinal cord injuries often lose the ability to move their arms or legs. In many cases, the nerves in the limbs remain healthy, and the brain continues to function normally. The loss of [...]
Scientists Discover a New “Cleanup Hub” Inside the Human Brain
A newly identified lymphatic drainage pathway along the middle meningeal artery reveals how the human brain clears waste. How does the brain clear away waste? This task is handled by the brain’s lymphatic drainage [...]
New Drug Slashes Dangerous Blood Fats by Nearly 40% in First Human Trial
Scientists have found a way to fine-tune a central fat-control pathway in the liver, reducing harmful blood triglycerides while preserving beneficial cholesterol functions. When we eat, the body turns surplus calories into molecules called [...]
A Simple Brain Scan May Help Restore Movement After Paralysis
A brain cap and smart algorithms may one day help paralyzed patients turn thought into movement—no surgery required. People with spinal cord injuries often experience partial or complete loss of movement in their arms [...]
Plant Discovery Could Transform How Medicines Are Made
Scientists have uncovered an unexpected way plants make powerful chemicals, revealing hidden biological connections that could transform how medicines are discovered and produced. Plants produce protective chemicals called alkaloids as part of their natural [...]
Scientists Develop IV Therapy That Repairs the Brain After Stroke
New nanomaterial passes the blood-brain barrier to reduce damaging inflammation after the most common form of stroke. When someone experiences a stroke, doctors must quickly restore blood flow to the brain to prevent death. [...]
Analyzing Darwin’s specimens without opening 200-year-old jars
Scientists have successfully analyzed Charles Darwin's original specimens from his HMS Beagle voyage (1831 to 1836) to the Galapagos Islands. Remarkably, the specimens have been analyzed without opening their 200-year-old preservation jars. Examining 46 [...]
Scientists discover natural ‘brake’ that could stop harmful inflammation
Researchers at University College London (UCL) have uncovered a key mechanism that helps the body switch off inflammation—a breakthrough that could lead to new treatments for chronic diseases affecting millions worldwide. Inflammation is the [...]
A Forgotten Molecule Could Revive Failing Antifungal Drugs and Save Millions of Lives
Scientists have uncovered a way to make existing antifungal drugs work again against deadly, drug-resistant fungi. Fungal infections claim millions of lives worldwide each year, and current medical treatments are failing to keep pace. [...]
Scientists Trap Thyme’s Healing Power in Tiny Capsules
A new micro-encapsulation breakthrough could turn thyme’s powerful health benefits into safer, smarter nanodoses. Thyme extract is often praised for its wide range of health benefits, giving it a reputation as a natural medicinal [...]
Scientists Develop Spray-On Powder That Instantly Seals Life-Threatening Wounds
KAIST scientists have created a fast-acting, stable powder hemostat that stops bleeding in one second and could significantly improve survival in combat and emergency medicine. Severe blood loss remains the primary cause of death from [...]
Oceans Are Struggling To Absorb Carbon As Microplastics Flood Their Waters
New research points to an unexpected way plastic pollution may be influencing Earth’s climate system. A recent study suggests that microscopic plastic pollution is reducing the ocean’s capacity to take in carbon dioxide, a [...]
