We all have a blood-brain barrier. It’s like a saran wrap around the small blood vessels in our brains. It protects the brain from infections, toxins and other threats, and it maintains homeostasis.
“But sometimes it does too good of a job,” said Dr. Ryan Alkins, neurosurgeon.
The blood-brain barrier (BBB) slows, and often prevents, the intake of life-saving drugs as well.
Alkins graduated from Sardis Secondary in 1999, then continued on to obtain his medical education at UBC.
By July of 2015, he had completed his neurosurgery residency and PhD in Medical Biophysics at the University of Toronto.
Alkins has been studying the BBB extensively for years, but his team’s recent discovery is now garnering national attention.
“Only a select type of drugs can cross the brain blood barrier,” Alkins said. Thus, treatment options are drastically limited for patients with brain tumours or neurodegenerative disorders.
However, Alkins and his colleagues at Sunnybrook Hospital are testing out a new method of drug delivery to the brain, one that “disrupts” the BBB.
This non-invasive method administers the treatment – chemotherapy, for instance – to the patient through an IV. The patient then lays down in an MRI unit, where doctors inject microscopic gas bubbles into the bloodstream through the IV. At the same time, doctors focus a high-intensity ultrasound on targeted areas of the brain.
“It’s like focusing light with a magnifying glass,” Alkins said.
The ultrasound causes the gas bubbles to rapidly expand and contract, and that oscillation creates tiny, temporary openings in the BBB, allowing the chemotherapy to leak through to the tumour or other destination.
The method was first found successful with animals, and they now are conducting their initial clinical trials on humans.
“We use an MRI dye contrast,” Alkins said. “So as [the treatment] leaks through the openings, we can see it on the MRI immediately afterwards.”
That’s precisely how they knew that their method was successful with their first patient, Bonny Hall.
This game-changing method of delivery means that doctors are able test out a range of chemotherapeutic drugs on the brain, rather than only the ones that could permeate the BBB on their own.
Furthermore, localization in the brain allows patients to take in lower dosages of the drug, which means they experience less of the side-effects.
Being non-invasive, this method also grants reduced risks to the patient. Prior attempts to bypass the BBB include drug-releasing wafers implanted onto the surface of the brain, or inserting a catheter in the groin to pump the drug, both of which require surgery.
When done correctly, Alkins said this new method causes no damage to the blood vessels. The gas bubbles dissolve in the bloodstream after about five minutes, and openings in the BBB close up within about six to twelve hours.
The clinical trial will include up to 10 patients, and will serve as a gateway to further studies.
Once they determine that this method is an effective way to increase drug concentrations beyond the BBB, and that it is safe and well-tolerated in humans, they will move on more long-term studies to determine if it can improve survival.
If proven effective, the implications of this method of delivering therapies to the brain go beyond cancer treatment. It could potentially be used to to provide recovery from a stroke, and in the treatment of neurodegenerative disorders like Alzheimer’s and Parkinson’s.
Alkins designed the trial with his PhD supervisor Dr. Kullervo Hynynen, and spearheaded its Health Canada approval process. He’s part of the team of five, with primary investigator Dr. Todd Mainprize, who are administering the initial trials.
Results of the trials are expected in about a year. Learn more at sunnybrook.ca.
