PET Imaging Biomarker Has Potential Application in Cancer Diagnosis and Treatment

A new positron emission tomography (PET) imaging agent was designed to capture and quantify the cellular expression of carbonic anhydrase IX (CA-IX), an enzyme whose expression has been linked to tumor growth and invasion, as well as hypoxia.

Siemens Healthcare (Erlangen, Germany) reported initial findings of a new imaging biomarker developed by its molecular imaging biomarker research facility in collaboration with Dr. Jian Q. (Michael) Yu and Fox Chase Cancer Center (Philadelphia, PA, USA). The results were presented September 23, 2009, at the World Molecular Imaging Conference in Montreal, Canada. "These are very exciting initial results,” said Jian Q. Yu, M.D., from the Fox Chase Cancer Center. "The potential ability to noninvasively determine the level of potency in malignant cancer cells might drastically change the treatment course in individual patients.”

CA-IX is an active enzyme, whose expression usually promotes tumor growth and invasion, and thus impairs prognosis. Noninvasive quantification of CA-IX expression may have the potential to characterize the biologic aggressiveness of malignant tumors in an individual, without the need for the invasive collection of tissue samples. The detection of CA-IX in patients may provide a novel approach to predict disease outcomes and efficacious responses to cancer therapy, and, ultimately, help physicians decide on the most effective treatment options for patients.

The results of the phase 0 (exploratory), or "first-in-human,” study indicated that the bio-distribution of the new agent was recorded at safe levels for clinical use in PET studies. The agent was also found to be stable for imaging at 133-minutes postinjection, which allows a sufficient window for acquiring the image, and that the agent safely clears the body through urinary elimination. The study included initial human data regarding biodistribution of the new agent, radiation dosimetry levels in normal volunteers, and optimal patient imaging parameters using PET. Further study with patients is currently in progress.

"Siemens is committed to investing in new scientific and technological methods to visualize disease so that, ultimately, patients can be diagnosed and treated earlier,” said Hartmuth Kolb, vice president, Siemens Biomarker Research, Molecular Imaging.

CA-IX is one subtype of transmembrane carbonic anhydrases, which catalyzes the reversible hydration of carbon dioxide into carbonic acid and is believed to be involved in pH regulation, which is linked to tissue invasion by tumors. The absence of CA-IX expression has been observed in many normal tissues. The abnormal expression of CA-IX has been detected in many carcinomas originating from CA-IX negative tissues including, the brain, kidney, lung, breast, and uterine cervical tissues.

Phase 0 trials are conducted in accordance with the U.S. Food and Drug Administration's (FDA) guidance on exploratory investigational new drug (IND) studies. These types of studies are intended to improve the development of promising drugs or imaging agents by determining at a very early stage if the drug or agent performs as expected, based on earlier results in preclinical trials.

Siemens Molecular Imaging Biomarker Research facility in Los Angeles (CA, USA) is focused on the discovery and development of new imaging biomarkers to spur the growth of in vivo molecular diagnostics. In addition to this study mentioned, Siemens also has four other agents in development, with the goal of bringing several new agents to the clinical market over the next five to 10 years. Research and development efforts conducted at the facility and with Siemens' research partners focus largely on oncology and neurology, and include such agents as those that visualize angiogenesis, cell proliferation, hypoxia, and amyloid plaque.

The Siemens Healthcare Sector is one of the world's largest suppliers to the healthcare industry and a trendsetter in medical imaging, laboratory diagnostics, medical information technology, and hearing aids.

Related Links:
Siemens Healthcare
Fox Chase Cancer Center