Ultrasound, the technology best known for letting you look at your unborn child, could help help deliver medicines to hard-to-reach places like brains, to treat diseases like Alzheimer’s and cancer. As the Wall Street Journal notes, “Sound waves combined with tiny bubbles in the bloodstream can push drugs into the brain and tough-to-reach tumors….A cutting-edge approach that combines ultrasound waves with tiny bubbles of inert gas injected into the bloodstream can get more chemotherapy to tumor cells and enable drugs to breach one of the most stubborn frontiers in the human body—the blood-brain barrier. It is also being explored as a new way to deliver gene therapy.”
As the Journal explains,
The effectiveness of drugs in treating diseases like cancer, Alzheimer’s and Parkinson’s is often limited by poor penetration into tissues….whether in the brain or in tumors in other parts of the body….
To get to the places they are needed, many drugs must move from the bloodstream into surrounding tissue. The medicines have to travel through the thin walls of the capillaries, the body’s smallest blood vessels, and reach the target cells. This is tougher in some parts of the body than others. Some tumors are surrounded by dense networks of connective tissue that are hard to penetrate. In the brain, the capillary-wall cells are so tightly packed that they form a barrier that the vast majority of drugs can’t get through.
The new approach relies on targeted ultrasound waves that cause vibrations in tiny bubbles that are injected into the bloodstream. The resulting force—which some compare to the way an opera singer’s voice can make a wine glass quiver and even shatter—disrupts the surrounding capillary walls and tissue, temporarily creating microscopic gaps that have been shown to ease the passage of drugs in early human studies…..
The procedure takes place during drug dosing or soon after. Typically, the microbubbles are injected intravenously while ultrasound, similar to the type used for fetal imaging, is applied at the target site for around five minutes. In one cancer trial, for instance, the microbubbles and ultrasound are administered around an hour after chemotherapy begins, so that the drug is at a high concentration in the blood at the time of the procedure.
While the microbubbles flow throughout the bloodstream, the disruption in tissue only occurs in the part of the body exposed to the ultrasound wave. The effect is temporary, lasting for as little as an hour, and the microbubbles remain in the blood for only around five minutes. The tiny size of the bubbles means they don’t pose a risk of causing dangerous blockages in blood vessels, researchers say.
There is some risk of damage to tissues, depending on how frequently the procedure is used. Further research is needed to assess how often the procedure can be applied. But
early human trials are producing encouraging results. In a small study of patients with glioblastoma—a type of brain cancer—researchers found that using the technology in treatment with carboplatin, a powerful chemotherapy, resulted in six times the amount of the drug in brain tissue that was exposed to the targeted ultrasound compared with unexposed brain tissue. In patients treated with paclitaxel, another cancer drug, levels were 3.7 times higher where the procedure was applied. Under normal circumstances, both drugs are seldom used to treat brain cancer because so little can get across the blood-brain barrier…..liver tumors in two patients in a Phase 1 clinical trial that were exposed to ultrasound plus microbubbles during chemotherapy shrank more than those without the ultrasound.
