Results of Phase I of CTT1057 Human Clinical Trial for Prostate Cancer Now Published

Scientists at UC San Francisco have just conducted the first-in-human Phase I study of CTT1057 in patients with localized and metastatic prostate cancer. CTT1057 is a lead diagnostic product from Cancer Targeted Technology (CTT), sponsor of this clinical trial, a collaboration between the Department of Radiology and Biomedical Imaging, Hematology/Oncology, Pathology and Urology. This important work was recently published online in The Journal of Nuclear Medicine.

In nuclear medicine, radiopharmaceuticals are used for diagnostic and therapeutic purposes. They are administered to patients and monitored using imaging. In prostate cancer diagnostic imaging, radiopharmaceuticals targeting prostate-specific membrane antigen (PSMA) are an emerging class of effective tools. CTT1057 is a 18F-labeled PSMA-targeting PET agent for detecting prostate cancer. According to researchers, CTT1057 is different from most other PSMA targeting agents with a urea-backbone because it is based on a phosphoramidate scaffold that irreversibly binds to PSMA. CTT1057 can be used to image both the localized and extent of the disease. Such a feature could allow for better, more effective diagnosis and monitoring, leading to more informed personalized treatment choices alongside regimens to prevent and/or reduce the pace of disease progression.

To perform the clinical trial, scientists recruited two patient cohorts. Cohort A were patients with localized prostate cancer pre-prostatectomy. Cohort B were patients with evidence of metastatic castration-resistant prostate cancer. Both were injected with CTT1057 intravenously. Combined PET/MR imaging was used following the injection. Cohort A patients were imaged on multiple time points to evaluate the kinetics of CTT1057 and estimate radiation dose profiles. Cohort B patients were imaged 60 to 120 minutes after injection of CTT1057. In both cohorts, PET images were assessed for overall image quality and contrasted with conventional imaging. (Read about the methodology in greater detail.)

Researchers concluded that CTT1057 is a promising PSMA-targeting, 18F-labeled PET radiopharmaceutical. It shows similar biodistribution to urea-based PSMA-targeted agents, but with lower exposure to both the kidneys and salivary glands, organs at risk from radiation exposure. In addition, it detects metastatic lesions with higher sensitivity than conventional imaging.

Spencer Behr, MD, associate professor of Clinical Radiology and Rahul Aggarwal, MD, assistant professor of Hematology/Oncology ran the clinical trial and are co-first authors. Henry Vanbrocklin, PhD, professor in residence and director of the Radiopharmaceutical Research and Youngho Seo, PhD, professor in residence and director of Nuclear Imaging Physics in the Center for Molecular and Functional Imaging (CMFI) at UCSF are senior investigators developing this radiopharmaceutical and analyzing the Phase I imaging data in collaboration with the team at Cancer Targeted Technology.

Authors from the UCSF Department of Radiology and Biomedical Imaging include Robert Flavell, MD, PhD, Kenneth Gao, Joseph Blecha, MS, Salma Jivan, Thomas Hope, MD, John Kurhanewicz, PhD, Susan Noworolski, PhD, Natalie Korn, and Romelyn De Los Santos. Other co-authors of this paper from UCSF include Eric Small, MD (Medicine/Division of Hematology/Oncology); Jeff Simko, MD, PhD (Pathology); Matthew Cooperberg, MD, MPH, Peter Carroll, MD, Hao Nguyen, MD, PhD and Kirsten Greene, MD, MS (Urology).

Next up are further prospective studies with CTT1057 to expound its role in cancer imaging, particularly in conjunction with its sister therapeutic radiopharmaceutical, 177Lu-labeled CTT1403 which is being planned for its Phase I study in the near future. Patients can find out more about this clinical trial at ClinicalTrials.gov.

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