Building a Better Radiotracer
Waiting twenty years for your discovery to gain FDA approval and become available to physicians might test some researchers’ resolve. But radiopharmaceutical chemist Mark Goodman, PhD, kept his eye on the prize: a new and improved imaging agent to detect and view cancers.
When Goodman first came to Emory in 1993, it was his responsibility to support the Emory PET Center—providing imaging tools for researchers, mentoring and training fellows, and establishing his own research program. He welcomed the chance to continue investigating a synthetic amino acid labeled with radioactive carbon-11 that had been successfully used to image brain cancer.
The problem was that carbon-11 has a short half-life—about 20 minutes which realistically only allows for one patient study per batch production. “It was a lot of production effort for one patient,” says Goodman, professor of radiology and imaging sciences and Endowed Chair in Imaging Science at Emory School of Medicine and Winship Cancer Institute. “I wanted to expand on this, to see if I could develop an analog with a half-life greater than 60 minutes that would allow for many patient studies per batch production.”
Goodman and colleague Tim Shoup, PhD, now at Massachusetts General Hospital, designed just such a molecule, FACBC and studied it in cancer cells and in rodents with grade 4 brain tumor models. FACBC seemed to have the same properties as its carbon-11 labeled predecessor did in humans, as well as a longer half-life from radioactive fluorine-18, which is amenable to multidose batch production. From there, Goodman and Emory neurosurgeon Jeff Olson, MD, translated the technology to humans, and found it to be superior in glioma and metastatic brain tumor subjects to the standard imaging agent at that time.
“With this data in hand, we approached Emory’s Office of Technology Transfer about our discovery,” says Goodman, program director for Emory’s Center of Systems Imaging and director of the Radiopharmaceutical Discovery lab.
The technology was patented by Emory and was licensed to Nihon Mediphysics, which supported his research for several years. GE Healthcare licensed the technology from Nihon in 2008. “Initially they were very enthusiastic, and were looking at it for all kinds of cancers,” he says. GE Healthcare contracted with several sites in the US—Ann Arbor, Salt Lake City, New York—setting up collaborations for parallel clinical trials. But the company was also pursuing an Alzheimer’s imaging agent. “They went full-bore on the Alzheimer’s agent to beat a smaller company to market, and our compound languished,” says Goodman.
Goodman and David Schuster, MD, associate professor of radiology and imaging sciences at Emory, discovered that the radiotracer was especially good for looking at prostate cancer, because of its “low native urinary excretion," says Schuster. It proved superior to the conventional PET imaging agent—radioactive glucose—which is readily taken up by cancer cells but also appears in the urine, making detection more difficult since the prostate bed is close to the bladder.
While this was happening, a few GE employees went out on their own, starting Blue Earth Diagnostics in 2014 “solely to bring our imaging agent to market,” says Goodman. “They did it in two years, just under the wire of the patent’s expiration.” FACBC, under the brand name Axumin™, gained FDA approval on May 27, 2016. Axumin™ also received an FDA “orphan drug” designation for the diagnosis of glioma in 2015.
“I was very happy for Dr. Goodman after learning that Fluciclovine had received regulatory approval. Having worked on this project for many years and seeing it finally cross the finish line was quite rewarding for me personally,” say Cale Lennon, director of licensing from the Emory Office of Technology Transfer.”
Research on the radiotracer continues: Goodman, Olson and Schuster continue to investigate its use in detecting glioma, Schuster and Ashesh Jani, MD, professor of radiation oncology, are investigating its use in recurrent prostate cancer to guide decisions about radiation treatment; Baowei Fei, PhD, EngD, of the Coulter Department of Biomedical Engineering at Georgia Tech and Emory, is researching how to combine FACBC/Axumin™ with ultrasound to guide prostate biopsy; and Emory urologist Martin Sanda, MD, and colleagues are investigating its use to assess cancer severity in high-risk prostate cancer.
“You can do good science, but when it comes to commercialization, you have to rely on a partner you have faith in,” says Goodman. “It looks like this imaging agent will be out there for patient use now. That feels great, it really does.”
Later support for clinical research on FACBC/fluciclovine came from the National Cancer Institute, the Georgia Research Alliance and the Georgia Cancer Coalition.
Press Release: FDA approves Emory-developed prostate cancer imaging probe