Canada’s particle physics laboratory TRIUMF is making a push to be a future world leader in the production of a special radioactive isotope nicknamed the “rarest drug on Earth,” which can deliver devastating amounts of energy to single cancer cells, without harming nearby tissue.
Most nuclear isotopes in medicine are used for diagnosis, by allowing scanning technology to see certain aspects of organs, bones, blood flow, and tumours. But Actinium-225 has shown promise in experimental uses on late stage cancer patients as an actual radioactive medicine that can kill cancer cells — and only cancer cells — by delivering an intense but hyper-local blast of energy.
The problem, as researchers at Vancouver-based TRIUMF put it, is that Actinium-225 is the “rarest drug on earth,” produced only as a by-product of nuclear weapons production, or in tiny amounts in TRIUMF’s own laboratory. Each year, the entire world only makes an amount equal to the weight of a few grains of sand.
To illustrate its promise, they point to the successful treatment of a German man in his 70s identified only as Peter, whose metastatic prostate cancer appears to have been sent into complete remission after being treated.
The idea is that a particle of Actinium-225 can be bound to a particle of a drug that selectively attaches only to cancer cells. When that happens, a sort of trigger prompts the Actinium-225 particle to decay in a cascade of “daughter” and “grand-daughter” isotopes. As it does, it releases a burst of energy that Paul Schaffer, TRIUMF’s associate lab director for life sciences, compared to firing a cannonball into a pool.
“Basically you’re taking a heavy particle from radioactive decay and shooting it into the cell,” he said.
That puts a lot of energy into a very small space. A particle passes through the cell, doing damage as it does so, but because its energy is expended so quickly, it only gets through one, two, maybe four cells before it dissipates. DNA and other critical parts of the cell are destroyed.
The strategy is unproven and largely untested, and it has only been used as a last-ditch effort in places such as Germany, where experimental treatments like this are allowed. But slowly, medicine is building up anecdotal evidence from Actinium’s use against leukemia and prostate cancer, with likely similar applications for pancreatic, colorectal and breast cancer.
“I can’t overstate how much I get excited when I talk about it. It sends a chill down my spine, to be honest with you,” said Schaffer.
The problem is the production process and its reliance on nuclear weapons waste. Schaffer’s project is to find another way to make it.
The solution has been to use the element thorium, make it into a disk, then put it at the end of a high energy particle beam, and then slam protons into it. That causes a cascading shower of smaller elements, one of which is Actinium-225.
Schaffer is a chemist, and therefore accustomed to taking stable compounds out of fridges and combining them in glassware. Now, in the nuclear world, by “moving beyond the bottles” to proton accelerators, he is “transmuting” one element into another by smashing particles together.
He calls this nuclear chemistry a kind of modern “alchemy,” and though he means it as a metaphor, he works with equipment that literally can turn lead into gold (though not in economically viable quantities).
For Actinium, the plan and hope is to partner with the reactor at Chalk River, Ont., with the goal of building a production line that could contribute perhaps a couple of kilograms of Actinium-225 per day, enough to make a serious play at the potential global market.
“We wouldn’t need a new accelerator. That’s the beautiful part of all this,” Schaffer said.