Researchers from Johns Hopkins experimented with mice and reported the successful use of positron emission tomography for the calculation of real-time taken by an immunotherapy drug to reach a tumor.
The technique utilizes the PET imaging of a radiolabeled protein that is synthesized and locks on the tumor cells, allowing the researchers to visually follow the place where an inhibitor drug is binding to a tumor while dispersing. “This approach offers a vital step toward directly measuring how well immunotherapy drugs are able to engage a tumor in any given person,” said an associate teacher of radiology at John Hopkins University, Dr. Sridhar Nimmagadda.
The research team had to make in the lab, a special small radiolabeled protein or a peptide, that would bind to PD-L1, and facilitate in identifying a receptor with the radiotracer that is visible to PET imaging.
Firstly, observing the results of lab-grown cells, the researchers were able to confirm that the radiolabeled peptide will not be altering or interfering with the drugs of immunotherapy. They said that repeated tests had shown that the peptide was bound to PD-L1 with lesser vigor and that it was not able to push off the bounded drug. This ability allowed it to serve as a PD-L1 protein’s efficient marker that had to receive the treatment. The researchers then applied the same technique on animals. Mice with implanted lung tumors of humans were given a single dose of atezolizumab, i.e. a cancer-fighting drug.
When these mice were compared to the controls that had received merely a saline injection, it was found that there was a 77% reduction in the unoccupied PD-L1 levels of tumors, proving that the researcher’s treatment had reached most of the PD-L1 proteins
“The remaining areas indicate parts of the tumor that the immunotherapy didn’t reach,” added Nimmagadda. “In human patients, this could give us some insight about how to optimize further treatments by increasing the dose or substituting other drugs or therapies more quickly.”
“These results represent a necessary initial step toward finding safe, effective and personalized doses of immunotherapy,” Nimmagadda said.