PET-Based Imaging of Radiolabeled CIT-013 (Cityview)

PET-Based Imaging to Evaluate the Distribution of Radiolabeled CIT-013 in Patients With Inflammatory Mediated Immune Disease

Inflammatory mediated immune diseases (IMIDs), such as rheumatoid arthritis (RA) and hidradenitis suppurativa (HS), are characterized by chronic inflammation resulting from an aberrant immune response. Recent studies have identified neutrophil extracellular traps (NETs) as key contributors to the pathology of these diseases. CIT-013 is a novel humanized monoclonal antibody designed to inhibit NET release and enhance phagocytosis, offering a new potential therapeutic strategy for RA and HS. Previous clinical trials have demonstrated that CIT-013 is well tolerated in both healthy volunteers and patients with RA, with evidence of reduced NET formation and positive effects in active RA cases. Since NET-related inflammation primarily occurs in local tissues, understanding CIT-013's distribution beyond blood measurements is crucial for evaluating its therapeutic potential. This trial therefore uses radiolabeled CIT-013 and Positron Emission Tomography-Computed Tomography (PET-CT) imaging, along with lymph node biopsies, to evaluate the distribution of CIT-013 and target engagement in patients with IMIDs.

Study Overview

• Status: Recruiting
• Conditions: RA
• Intervention / Treatment: Drug: [89Zr]Zr-CIT

• Study Type: Interventional
• Enrollment (Estimated): 12
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Leonie Middelink; Phone Number: +31613328444; Email: lmiddelink@citryll.com

Study Locations

• Netherlands
  • Nijmegen, Netherlands
    • Recruiting
    • NL-01
    • Contact: PI NL-01

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Female (of non-childbearing potential) or male between 60-85 years of age (both inclusive).
• For male participants with female partners of child-bearing potential, an adequate form of contraception must be adhered to, and men must refrain from donating sperm, prior to entry into the trial and for a further 6 months after IP administration.
• Willing and able to provide written, informed consent.

Exclusion Criteria:

• Diagnosed with RA according to the 2010 classification criteria of the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR) ≥ 6 months prior to screening (diagnosis based on medical records).

Participants in Cohort A (active RA) must furthermore meet the following criteria:

- Disease Activity Score 28 (DAS28) C-Reactive Protein (CRP) (DAS28-CRP) ≥ 4.2 AND ≥ 1 Swollen Joint AND ≥ 1 Tender Joint prior to screening.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: [89Zr]Zr-CIT-013	Drug: [89Zr]Zr-CIT; radiolabelled CIT-013

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Distribution of radiolabeled CIT-013 in patients with IMIDs	Whole body PET-CT imaging 24 hours (D2) after IP administration. In addition to visual assessment, uptake of [89Zr]-DFO-CIT013 will be quantified per organ(-system). In vivo distribution profiles will be evaluated per cohort to determine ranges of uptake per organ(-system) and between cohorts to compare uptake in different IMIDs	24 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
safety and tolerability of CIT-013 in patients with IMIDs.	Frequency and severity of treatment-emergent adverse events (TEAE) throughout the trial period, including clinically relevant findings and ADAs.	Day 29

Collaborators and Investigators

• Sponsor: Citryll BV

Study record dates

Study Major Dates

• Study Start (Actual): January 15, 2026
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: August 22, 2025
• First Submitted That Met QC Criteria: August 22, 2025
• First Posted (Actual): August 29, 2025

Study Record Updates

• Last Update Posted (Actual): January 30, 2026
• Last Update Submitted That Met QC Criteria: January 28, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: CITRYLL004

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No