A Study of the Pharmacokinetics, Biodistribution and Dosimetry of Granzyme-B Targeted [Cu-64]-Labeled PET Radiotracers in Adult Healthy Volunteers

NCT07774650 | Recruiting Early Phase 1 FDA Drug

• 1 other identifier: RTX-4000-101
• Study Type: interventional
• Target: 12
• Locations: 1 country
• Sites: 1

Brief Summary

This is an exploratory clinical study of copper-64 \[Cu-64\]-labeled granzyme B (GzmB)-targeted compounds for PET/CT imaging. The goal is to determine how GzmB-Targeted \[Cu-64\]-labeled compounds are distributed in the body by assessing PET/CT images and blood samples, and to assess the safety profile after a single intravenous dose. Up to 6 healthy volunteers (3 female, 3 male) will receive one injection of a GzmB-targeted \[Cu-64\]-labeled compound, then undergo multiple whole-body PET/CT scans, blood and urine tests over about 24 hours, and a follow-up phone call around Day 7. Up to 2 GzmB-Targeted \[Cu-64\]-labeled compounds may be assessed (i.e. maximum of 12 healthy volunteers in total in the study). Researchers will look at the blood activity of GzmB-Targeted \[Cu-64\]-labeled compound and the organ distribution and movement of the product in the body. They will also evaluate any changes in physical examination assessments, vital signs, ECG, and clinical laboratory measurements from pre-administration to post-administration.

Conditions

Healthy Volunteer

Outcome Measures

Primary Outcomes (8)

• Determine the maximum concentration (Cmax) of radiation (Pharmacokinetics) in the blood after a single dose of the GzmB-Targeted [Cu-64]-labeled compound

  Blood samples will be collected Pre-dose, immediately post-dose, 45 minutes, 1 \& 4 hours, \& 24 hours post dose. Radiation (PK) to be measured by gamma counter (KBq/mL).

  24 hour period post injection.

• Determine the time to maximum concentration (Tmax) in the blood after a single dose of the GzmB-Targeted [Cu-64]-labeled compound

  Blood samples will be collected Pre-dose, immediately post-dose, 45 minutes, 1 \& 4 hours, \& 24 hours post dose. Time to maximum concentration to be measured in hours (h).

  24 hour period post injection

• Determine the area under the curve (AUC) in blood after a single injection of the GzmB-Targeted [Cu-64]-labeled compound

  Blood samples will be collected Pre-dose, immediately post-dose, 45 minutes, 1 \& 4 hours, \& 24 hours post dose. AUC to be calculated by kilobecquerel x hours/milliliter (KBq x h/mL)

  24 hour period post injection.

• Determine the elimination half-life in the blood post a single injection of the GzmB-Targeted [Cu-64]-labeled compound

  Blood samples will be collected Pre-dose, immediately post-dose, 45 minutes, 1 \& 4 hours, \& 24 hours post dose. Elimination to be measured by time to half of the product being excreted from the blood (as measured by gamma counter) in hours (h)

  24 hour period post injection

• Determine the clearance in the blood after single injection of the GzmB-Targeted [Cu-64]-labeled compound

  Blood samples will be collected Pre-dose, immediately post-dose, 45 minutes, 1 \& 4 hours, \& 24 hours post dose. Clearance to be measured by milliliter/minute.

  24 hour period post injection

• Determine the volume of distribution in the blood after a single injection of the GzmB-Targeted [Cu-64]-labeled compound

  Blood samples will be collected Pre-dose, immediately post-dose, 45 minutes, 1 \& 4 hours, \& 24 hours post dose. Volume to be measured by Liter

  24 hour period post injection

• Evaluate the organ distribution of radioactivity for a single dose of GzmB-targeted [Cu64]-labeled compound

  Measuring the uptake in organs from a PET/CT. Imaging timepoints will be collected at 20 minutes post dose, 1 \& 4 hours and 24 hours post dose

  24 hour period post injection

• Evaluate the safety profile for a single dose of the GzmB-Targeted [Cu-64]-labeled compound in adult healthy volunteers

  Determine the incidence, and severity of Treatment Emergent Adverse Events (TEAEs including SAEs).

  From injection to 8 days post injection

Secondary Outcomes (5)

• Evaluate the radiation absorbed dose estimates for organs for a single dose of the GzmB-Targeted [Cu-64]-labeled compound

  24 hour period post injection

• Evaluate the whole body effective dose estimated for a single dose of the GzmB-Targeted [Cu-64]-labeled compound

  24 hour period post injection

• Examine whole-body excretion of a single dose of the GzmB-Targeted [Cu-64] labeled compound

  Samples will be taken continuously starting immediately post-dose through 24 hours post injection

• Determine the total cumulative excretion over time in the urine (mL/min) for the GzmB-Targeted [Cu-64]-labeled compound

  A 24 hour period post injection

• Determine the renal clearance for the GzmB-Targeted [Cu-64]-labeled compound

  24 hour period post injection

Study Arms (2)

[Cu-64]RTX-4001

EXPERIMENTAL

Arm Description: Single IV administration of \[Cu-64\]RTX-4001, a Granzyme-B-targeted PET radiotracer, in healthy adult volunteers.

Drug: Granzyme-B targeted [64Cu]-labeled PET radiotracer

[Cu-64]RTX-4002

EXPERIMENTAL

Arm Description: Single IV administration of \[Cu-64\]RTX-4002, a Granzyme-B-targeted PET radiotracer, in healthy adult volunteers.

Drug: Granzyme-B targeted [64Cu]-labeled PET radiotracer

Interventions

Granzyme-B targeted [64Cu]-labeled PET radiotracer DRUG

Single intravenous administration of a Granzyme-B targeted \[64Cu\]-labeled positron emission tomography (PET) radiotracer to assess pharmacokinetics, biodistribution, and radiation dosimetry in adult healthy volunteers.

[Cu-64]RTX-4001; [Cu-64]RTX-4002

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Adult male or female participants 18-60 years of age judged to be in good health by the Investigator
• No clinically significant laboratory abnormalities; all tests of liver and kidney function within normal limits
• Capable of giving signed informed consent, which includes compliance with requirements and restrictions listed in the ICF and this protocol
• Female participants of childbearing potential and male participants who are fertile and have female partners of childbearing potential must agree to use adequate birth control throughout the study to the conclusion of follow-up.

You may not qualify if:

• Pregnant or breast-feeding female participants (female participants of childbearing potential must have negative pregnancy tests at Screening and pre-dose Day 0)
• Inadequate venous access (at least two distinct access sites allowing for separate test agent administration and PK blood sampling are required)
• Inability or unwillingness to undergo serial PET/CT imaging
• Active infection or malignancy
• Known or suspected inflammatory, autoimmune or fibrotic disease
• Major surgery or other intensive medical treatment in the 3 months prior to planned study injection, as assessed by the investigator
• Received a radioisotope within 7 physical half-lives of that radioisotope prior to planned study injection
• Known allergy/hypersensitivity to PET/CT tracers or compounds similar to GzmB-Targeted Compounds
• Concurrent participation in a clinical trial of investigational product(s)
• Participation in other research protocols or clinical care where there was radiation exposure such that the exposure from the last year, in addition to the radiation exposure expected from participation in this clinical study, exceeds the effective dose of 50 mSv, which would be above the acceptable annual limit established by US federal guidelines
• Significant intercurrent illness or psychiatric illness/social situation that could place the participant at undue risk during study participation, significantly alter study outcomes, or affect participant compliance with study requirements for dosing and evaluation, as determined by the investigator

Sponsors & Collaborators

• Ratio Therapeutics, Inc.: lead

Study Sites (1)

Xing Imaging

New Haven, Connecticut, 06510, United States

RECRUITING

Central Study Contacts

Anna Carberry

CONTACT

203-444-6025; clinicrecruitment@indd.org

Study Design

• Study Type: interventional
• Phase: early phase 1
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: DIAGNOSTIC
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: March 19, 2026
• First Posted: August 19, 2026
• Study Start: July 8, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2026
• Last Updated: September 1, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)