A phase two trial in Austria has revealed some astonishing results in the treatment of brain cancer, with a new drug shrinking metastases “significantly” in nearly three out of every four cases.
“I am very excited about the results,” oncology professor Matthias Preusser told IFLScience. “They can be directly used in patient care around the world and also open up new avenues of research in the brain tumor field.”
Preusser is a co-author of a new paper, published in Nature Medicine only this week, describing the trial’s success. The study followed 15 patients – 14 women and one man – who were being treated for HER2-positive breast cancer which had metastasized to the brain.
The key to the trial was the drug trastuzumab deruxtecan, a relatively new medication that’s been available for less than a year in many parts of the world. It “works like a Trojan horse,” Preusser told IFLScience: it’s what’s known as an antibody-drug conjugate (ADC) – a type of targeted medication comprising a monoclonal antibody and a cancer-killing agent which are chemically linked to each other.
“The antibody binds the drug to cancer cells, which then swallow the ADC,” Preusser explained. “In the tumor cell, the chemotherapy is released and kills the cancer.”
Trastuzumab deruxtecan has previously been shown to treat HER2-positive breast cancer pretty effectively, but the new trial wanted to see if it could provide the same benefits for cancer in the brain.
Until now, oncologists mostly assumed that drugs like trastuzumab deruxtecan wouldn’t be that helpful for treating cancers in the brain, because it has a relatively large molecular size. Thanks to the blood-brain barrier – a semi-permeable membrane found where the blood meets the cerebral tissue – only molecules smaller than 600 Da, or around 0.000000000000000000001 grams (so pretty small) can reach the brain.
With a molecular weight of about 158,000 Da, trastuzumab deruxtecan is well over this limit. So why did the researchers even try? Well, it turns out that metastases can actually disrupt the blood-brain barrier, allowing molecules far bigger than normal through to the brain tissue – and that, the team believe, is partly why the trial had such promising results.
“We found that the brain metastases shrank significantly in 11 of 15 patients, thus yielding a response rate in the brain of 73.3 percent,” Preusser reported. “In two patients the metastases were not detectable on MR images of the brain anymore.”
That’s very good news. “We showed in our study that this drug is also able to work against breast cancer that has spread to the brain,” Preusser told IFLScience, “and is thus able to help patients with very advanced and severe disease.”
Having now shown, albeit in a very small trial, that ADCs are a potential treatment for brain cancer – potentially even more effective in the long-term than current standard drug therapies – the team hope to see new treatments and trials being rolled out for brain and central nervous system cancers.
“I anticipate that more studies will focus now on ADC treatment of various kinds of brain tumors, both brain metastases from other cancers in the body such as lung cancer, and also from primary brain tumors such as glioblastoma,” Preusser told IFLScience.
“I hope that we will see improved treatment possibilities for cancers of the brain using ADCs.”