A Phase I PET Imaging Study of 64Cu-GRIP B, a Radiotracer Targeting Granzyme B, in Patients With Acute Myocarditis

Summary

The proposed patient study represents the first-ever acute myocarditis patient imaging study with 64Cu-GRIP B PET. The tracer is designed to detect extracellular granzyme B as it is secreted by activated cytotoxic T lymphocytes in the cardiomyocyte inflammatory microenvironment, highlighting areas of CD8 T cell activity leading to cardiomyocyte damage. Myocarditis is characterized pathologically by myocardial infiltration of T cells and macrophages with presence of cardiomyocyte death - the proposed tracer tests for both the accumulation of CD8 T cells and their cytotoxic activity, which will hopefully significantly improve diagnostic certainty. The study population is focused on patients with acute myocarditis to assess the specificity and sensitivity of 64Cu-GRIP B to detect myocarditis. In future studies, 64Cu-GRIP B PET may also serve as a biomarker to monitor early response to immunomodulatory therapies to treat acute myocarditis. Each year at UCSF, the investigators encounter about 20 patients with acute myocarditis. These patients often present with non-specific cardiac symptoms with some evidence of cardiac injury (abnormal electrocardiogram or elevation in cardiac biomarkers such as troponin). Rarely is the diagnosis clear and often numerous additional clinical studies are necessary to rule out other common causes of cardiac injury like myocardial infarction. Patients identified with acute myocarditis by the investigators will receive standard clinical testing as appropriate and will also be consented to participate in a PET study with 64Cu-GRIP B. Over the course of this proposal, the investigators expect to enroll 10 patients who are being evaluated for acute myocarditis determined by current standard of care diagnostic modalities. The investigators will perform this feasibility assessment in parallel to the usual clinical care.

Eligibility

Age range

18–85 years

Sex

All

Healthy volunteers

No

Interventions

• Drug
  64Cu-GRIP B is a radiolabeled peptide tracer, a copper-64 isotope bound to a peptide designed to target extracellular Granzyme B

  The proposed patient study represents the first-ever acute myocarditis patient imaging study with 64Cu-GRIP B PET. The tracer is designed to detect extracellular granzyme B as it is secreted by activated cytotoxic T lymphocytes in the cardiomyocyte inflammatory microenvironment, highlighting areas of CD8 T cell activity leading to cardiomyocyte damage. This study is the first to evaluate the efficacy of 64Cu-GRIP B PET in detecting acute myocarditis. Notably, 64Cu-GRIP is currently being investigated in the setting of cancer in NCT05888532 and has been well tolerated.

Location