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.

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.