LOS ANGELES (CNS) — UCLA scientists said they will soon begin clinical trials on a new PET scan tool that could be used to determine whether certain types of anti-cancer drugs will be effective on a particular patient, or create an adverse reaction instead, depending on the presence of an enzyme that has so far been difficult to detect in humans.

Certain drugs treating leukemia, and breast, ovarian, non-small cell lung and pancreatic cancers, are more effective for patients who have high levels of the deoxycytidine kinase, or dCK, enzyme in their tumor tissues, according to UCLA researcher Caius Radu. But the same drugs can also be ineffective or even toxic for patients who have low levels of the dCK enzyme, Radu said.

Doctors have been looking for a way to only administer such drugs to patients with high levels of the enzyme and to avoid giving them to those who could be harmed by them, but so far have been unable to monitor the presence of the enzyme in humans using the existing PET, or positron emission tomography, tools.

On Monday, March 28, Radu said UCLA researchers have developed a “promising” new PET probe — the radioactive substance used in the imaging device for detecting disease — that will give doctors the ability to see the dCK enzymes.

“The quality of the images is much better,” Radu said. “We are able to clearly see tissues, including tumor tissues, with high dCK activity that we haven’t seen before in humans using any of the other probes previously developed for this enzyme.”

The PET probe, dubbed [18F]CFA, should be able to detect dCK enzymes that prompt reactions in Clofarabine, Cytarabine and Fludarabine — drugs that treat certain forms of leukemia — and Gemcitabine, which is used for breast, ovarian, non-small cell lung and pancreatic cancers, the researcher said.

Radu said the dCK enzyme “is essential for the therapeutic activity of an entire class of anticancer drugs and even for some antiviral drugs.”

“It can take an inactive drug and activate it,” Radu said. “If you trick a cancer cell or virus to activate the drug, it would be toxic for the cancer cell or viral genome.”

The ability to make the dCK enzyme visible could also have other uses, such as in immunotherapy, which is a new area of oncology medicine in which doctors attempt to teach the immune system to fight cancer, Radu said.

For example, activated immune cells increase their expression of the dCK enzyme, which means the [18F]CFA could be used to monitor the effectiveness and progress of immunotherapy treatments, Radu said.

Radu said his team is hoping to begin clinical trials on the probe soon and, if successful, seek approval from the U.S. Food & Drug Administration.

The [18F]CFA is patented by the University of California and licensed to Sofie Biosciences, a company founded by Rafu and the other researchers.