Ultrasound breaks through the barrier
Focused ultrasound helps drugs penetrate the brain
A method has been developed that could revolutionize the treatment of brain cancer and neurodegenerative diseases by temporarily allowing drugs and other substances to cross the blood—brain barrier - the structure that separates the blood vessels of the brain from the rest of its tissues. A trial involving four women whose breast cancer has metastasized to the brain has shown that focused ultrasound guided by magnetic resonance can safely deliver a therapeutic drug to brain tissue, causing a tumor to shrink.
The blood-brain barrier prevents dangerous substances from entering the brain from the bloodstream, such as toxins or microbes. Only water, certain gases such as oxygen and a small amount of other substances are able to penetrate inside. But the mechanism that protects brain tissue simultaneously becomes an obstacle to the use of drugs. Therefore, doctors cannot apply a large number of drugs for cancer or neurodegenerative diseases, such as Alzheimer's disease.
The new method uses focused ultrasound to open the blood-brain barrier in certain areas, causing fluctuations in microscopic bubbles of contrast agent injected into the patient. These fluctuations cause gaps to appear in the cell wall of blood vessels, allowing substances that are usually difficult to enter the brain to pass through the barrier.
Nir Lipsman from the Sunnybrook Center for Medical Sciences in Toronto and his colleagues say that their method opens the barrier for less than a day. In the current work, they used ultrasound to deliver the monoclonal antibody trastuzumab (herceptin) to the affected areas of the brain in four patients with metastatic breast cancer. Although the study was primarily intended to assess the safety of the method, it showed that the drug was absorbed by the tumors and that they then decreased. It is important to note that none of the patients had serious side effects, and further imaging showed that their blood-brain barrier closed again after 24 hours.
"Herceptin is a huge compound, so if we can inject it into the brain with focused ultrasound, we can safely assume that we can inject other molecules of the same size or smaller," says Nir Lipsman.
The study was published in the journal Science Translational Medicine (Meng et al., MR-guided focused ultrasound enhancements delivery of trastuzumab to Her2-positive brain metastases).
Portal "Eternal youth" http://vechnayamolodost.ru