We’re Shaping the Future of Immunotherapy by Unlocking the Power of Granzyme B Abstract Orange Cubes to Tackle Cancer & Autoimmune Diseases.[I]Illustrative concept; not actual patient data unless explicitly stated.

Scientists Ben Larimer, PhD, Eric Wehrenberg-Klee, MD, and Umar Mahmood, PhD, pioneers in functional immunotherapy using Granzyme B-guided PET imaging, founded CytoSite Bio. Their groundbreaking work laid the foundation for our mission: to develop a unique class of radiopharmaceuticals that harnesses the power of granzyme B to transform medicine. Our platform provides a real-time window into the body’s immune activity,[II]Describes intended use and investigational objectives; clinical utility and outcomes remain under evaluation and are not guaranteed. offering a dual-pronged approach to radiodiagnostics and radiotherapeutics.

 

We have developed a first-in-class[III]“First-in-class” is based on CytoSite’s internal assessment of publicly available information as of the publish date; not independently verified. radiodiagnostic agent that provides an early and accurate assessment[II]Describes intended use and investigational objectives; clinical utility and outcomes remain under evaluation and are not guaranteed. of immunotherapy response in both cancer and autoimmune diseases. By mapping out immune activity, our solution can help accelerate clinical timelines by enabling swift go/no-go decisions[IV]Potential process benefits are investigational and depend on study design, regulatory guidance, and sponsor practices; not guaranteed. for new drug candidates and guiding patient care.

Our pipeline also includes a novel, investigational[V]Investigational; not approved for commercial use. The safety and efficacy of this product have not been established. radiotherapeutic. This innovative therapy uses intelligent targeting to hone in on the same granzyme B pathway, reinvigorating the immune system to kill cancer cells while sparing healthy tissue.[VI]Mechanistic description based on investigational design and preclinical/early data; benefit-risk has not been established in humans. Early preclinical data demonstrate our therapeutic agent can achieve a complete response,[VII]Preclinical model results; not necessarily predictive of human outcomes. offering a potent, next-generation treatment option.

 

This powerful combination of diagnostic insight and targeted therapy aims to usher in a new era of precision medicine[II]Describes intended use and investigational objectives; clinical utility and outcomes remain under evaluation and are not guaranteed. for a wide range of diseases.

Why CytoSite Bio

01

World-Renowned Leaders in Immunotherapy

Co-founders Benjamin Larimer, PhD, Eric Wehrenberg-Klee, MD, and Umar Mahmood, MD, PhD, three of the top global researchers in granzyme B, built CytoSite Bio. They developed the foundational technology for our platform and continue to provide unparalleled scientific and clinical leadership, ensuring our solutions are grounded in cutting-edge research. Their combined vision delivers a unique and powerful solution for the future of immunotherapy.

Benjamin Larimer, PhD

Benjamin Larimer, PhD

Co-founder and CEO
Umar Mahmood, MD, PhD

Umar Mahmood, MD, PhD

Co-founder
02

Trusted by Industry Giants

The potential of our granzyme B platform has earned the confidence of industry-leading companies, a powerful testament to the strength of our science. We have partnered with Lantheus, a global leader in precision diagnostics and radiopharmaceuticals, through a licensing agreement for our radiodiagnostic agent. This collaboration validates the clinical value of our technology.[VIII]Collaboration scope is governed by definitive agreements; collaboration does not guarantee regulatory approval, commercialization, or clinical success. Furthermore, our pipeline is advancing with the support of major global pharmaceutical companies and strategic partnerships that underscore the potential of our next-generation approach to precision immunotherapy.

Lantheus
Lilly
03

First-in-Class Granzyme B Targeting Platform

Our platform is the first of its kind[III]“First-in-class” is based on CytoSite’s internal assessment of publicly available information as of the publish date; not independently verified. to harness the power of granzyme B, a functional biomarker that directly signals immune-mediated cancer cell death. While other approaches look at static markers or general metabolic activity, our technology provides a real-time, actionable roadmap[II]Describes intended use and investigational objectives; clinical utility and outcomes remain under evaluation and are not guaranteed. of where the body is actively fighting a disease. By leveraging this single biological signal for both our diagnostic and therapeutic programs, we are pioneering a unique, integrated approach. Our imaging agent provides a clear picture of immune activity, while our therapeutic agent utilizes the same granzyme B pathway for precision-guided targeting and tumor destruction.[VI]Mechanistic description based on investigational design and preclinical/early data; benefit-risk has not been established in humans. This seamless connection is what makes our platform truly first-in-class.[III]“First-in-class” is based on CytoSite’s internal assessment of publicly available information as of the publish date; not independently verified.

Granzyme
04

Impressive Early Clinical Results— >95% Sensitivity/Specificity Across Multiple Cancer Types

Our diagnostic platform’s capabilities are supported by robust clinical data, demonstrating high clinical value with a sensitivity and specificity of over 95% across multiple cancer types to date.[IX]Performance metrics reflect early, limited-size studies with protocol-specific endpoints; not validated for all populations, indications, or settings; results may vary. These metrics aren’t just numbers; they represent the accuracy that is our goal to empower confident decision-making. The high sensitivity of our test will enable us to reliably detect when a patient’s immune system is actively fighting cancer. Conversely, our high specificity will ensure we can correctly identify when a therapy is not working, preventing patients from enduring ineffective and costly treatments. This high degree of accuracy and reliability is a critical differentiator, and will provide clinicians and drug developers with the certainty they need to guide patient care and accelerate the development of new drugs.

Cancer Cell
05

Ready-to-Deploy Infrastructure – GMP Manufacturing Complete, Active INDs, Established Clinical Sites

We’ve built the operational and regulatory infrastructure needed to accelerate clinical partnerships. Our platform is ready for immediate deployment, featuring a completed GMP manufacturing process to ensure a reliable supply of our radiopharmaceuticals. We have active INDs with a flexible, modular design that streamlines regulatory submissions for collaborators. Furthermore, our established network of clinical sites is prepared to conduct trials. This complete, pre-established framework eliminates the typical barriers to entry, enabling our partners to quickly and efficiently advance their clinical programs without delay.[X]GMP refers to clinical-trial manufacturing readiness; INDs authorize specified studies and do not imply approval. Site readiness and timelines are subject to various factors, including regulatory, operational, and contractual considerations.

Massachusetts General Hospital

Our Leadership

World-class scientists and operators advancing Granzyme B immunotherapy.
Leadership Team
Board of Directors

Our Leadership

Leadership Team
Board of Directors

Benjamin Larimer, PhD

Co-founder and Chief Executive Officer

Umar Mahmood, MD, PhD

Co-founder

Eric P. Wehrenberg-Klee, MD

Co-founder

Colin Miller, PhD

Clinical Operations and Regulatory

Geoffrey Bilcer, PhD

Medicinal Chemistry
Ellen Cordo is CytoSite Bio's Chief Financial Officer (CFO).

Ellen Cordo, CPA

CFO
Kimmai Phan is a Project Manager at CytoSite Bio focusing on granzyme B led immunotherapy.

Kimmai Phan

Project Manager

From Diagnostics to Therapeutics

Building on 7 years of Granzyme B expertise
2018
Company Founded
2020
First Human Granzyme B PET Image
2022
CSB-321 PET Imaging Diagnostic Clinical Trials Initiated
2023
CSB-321 Diagnostic Human Dosimetry Completed
2024
Pioneered granzyme B radiotherapeutic for immunotherapy
2025
Lantheus Licensing Deal

Company Founded

Developed first-in-class Granzyme B PET imaging

Cytosite founded with a mission of improving immunotherapy through granzyme B targeting.

First Human Granzyme B PET Image

First to image granzyme B in humans via a PET scan.

First-in-class in-human granzyme B PET image to visualize active immune response.

CSB-321 PET Imaging Diagnostic Clinical Trials Initiated

Pioneered Granzyme B targeting for cancer imaging. Progressed granzyme B targeting and imaging in multiple cancers.

CSB-321 Diagnostic Human Dosimetry Completed

First-in-class granzyme B PET imaging clinical trial.

Pioneered granzyme B radiotherapeutic for immunotherapy.

First-in-class preclinical granzyme B radiotherapeutic for immunotherapy.

Expanded the granzyme B platform for both radiodiagnostic & radiotherapeutic.

Our Progress to Date

Radiodiagnostic Progress

Diagnostics progressed to Phase II Clinical Trials, and commercial viability was proven.

Radiotherapeutic Progress

Preclinical indications of granzyme B radiotherapeutic as a potential groundbreaking immunotherapy.
2018
Company Founded

Company Founded

Developed first-in-class Granzyme B PET imaging

Cytosite founded with a mission of improving immunotherapy through granzyme B targeting.
2020
First Human Granzyme B PET Image

First Human Granzyme B PET Image

First to image granzyme B in humans via a PET scan.

First-in-class in-human granzyme B PET image to visualize active immune response.
2022
CSB-321 PET Imaging Diagnostic Clinical Trials Initiated

CSB-321 PET Imaging Diagnostic Clinical Trials Initiated

Pioneered Granzyme B targeting for cancer imaging. Progressed granzyme B targeting and imaging in multiple cancers.
2023
CSB-321 Diagnostic Human Dosimetry Completed

CSB-321 Diagnostic Human Dosimetry Completed

First-in-class granzyme B PET imaging clinical trial.
2024
Pioneered granzyme B radiotherapeutic for immunotherapy

Pioneered granzyme B radiotherapeutic for immunotherapy.

First-in-class preclinical granzyme B radiotherapeutic for immunotherapy.

Expanded the granzyme B platform for both radiodiagnostic & radiotherapeutic.

Be a Part of Our Success

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