CytoSite Bio Announces Agreement with Lantheus for Granzyme B Targeted PET Imaging Radiotracer for Immunotherapy Assessment

A global collaboration agreement has been signed for the development and commercialization of a Granzyme B-targeted Positron Emission Tomography (PET) imaging radiotracer.

This radiotracer has the potential to support the monitoring of patient immune response and supports the accelerated development for CytoSite.

CytoSite will lead initial clinical development with Lantheus having an exclusive option to acquire worldwide development and commercialization rights to the radiotracer.

BOSTON, March 26, 2025 /PRNewswire/ — CytoSite Bio (CytoSite) announced today that they have signed a collaboration agreement for the clinical development and potential commercialization of CytoSite’s investigational Phase 1 ready granzyme B-targeted Positron Emission Tomography (PET) imaging tracer with Lantheus Holdings, Inc. This agreement provides Lantheus with an exclusive option to license worldwide rights to CytoSite’s novel imaging technology.

The two companies will collaborate on clinical development, with Lantheus having the option to acquire exclusive worldwide rights for further development and commercialization of the product. Under the terms of the agreement, CytoSite is eligible to receive payments for development, regulatory and commercial milestones, plus royalties on future product sales.

Granzyme B is an enzyme released upon activation of immune cells to destroy harmful cells, including cancer. Early studies of the investigational imaging tracer have shown potential to evaluate whether immunotherapies are working effectively to activate the immune system. This investigational PET imaging radiotracer could enable physicians to measure the early efficacy of such therapies within days of first dose and modify treatment accordingly rather than waiting for months to fully understand if the treatment is working. Additionally, pharmaceutical developers can use the investigational imaging tracer to gain an early read-out of efficacy for new therapies, enabling faster decision-making and more efficient allocation of resources.

“The clinical data we have generated to date validates our belief that use of PET imaging to detect active Granzyme B has the potential to transform outcomes in immuno-oncology, autoimmune-mediated and inflammatory diseases,” said Benjamin Larimer, PhD, Co-founder and CEO of CytoSite. “We are excited to be partnering with Lantheus to bring Granzyme B PET imaging to the forefront. This strategic collaboration creates a clear path to commercialization with an ideal partner in the radiopharmaceutical space while providing significant value potential for CytoSite as we advance this promising technology in parallel with our own radiotherapeutic program.”

“If approved, CytoSite’s proprietary Granzyme B biomarker could provide a valuable tool for oncologists, radiologists and medical professionals to enable improved outcomes for cancer patients and rapidly expand options for new immunotherapies,” said Umar Mahmood, MD, PhD, Co-founder of CytoSite, Chief of Nuclear Medicine and Molecular Imaging in the Department of Radiology at Massachusetts General Hospital (MGH) and Professor of Radiology at Harvard Medical School.

About CytoSite Bio

CytoSite Bio is developing novel radiopharmaceuticals that enable the quantification and modulation of immune activation to improve cancer immunotherapy. The lead product detects active Granzyme B, the primary protein responsible for the killing of tumor cells by the immune system. CytoSite’s products enable individually optimized treatments for patients, and more rapid evaluation of new drugs and drug combinations, using non-invasive, whole-body PET imaging combined with targeted radiotherapy.

For more information: www.cytositebio.com

Contacts:
Ben Larimer, PhD
CEO, CytoSite Bio
781-608-9916
blarimer@cytositebio.com

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SOURCE CytoSite Bio