Assessment of Pulmonary Fibroblast Activity Using [68Ga]FAPI-46 PET/CT in Patients with Post-Acute Sequelae of COVID-19

The primary objective of this study is to assess whether **pulmonary fibroblast activity**, as measured by [68Ga]FAPI-PET/CT, is elevated in patients experiencing current long COVID dyspnea and fatigue compared to those with resolved symptoms. This evaluation is clinically relevant as it may provide insights into the persistence of symptoms in post-acute sequelae of COVID-19, potentially guiding personalized diagnostic and therapeutic strategies.

Secondary objectives include:

• Comparing whole body FAP uptake in patients with persistent versus resolved long COVID complaints.
• Evaluating FAP uptake in relation to clinical endpoints such as lung function, the 6-minute walking test (6-MWT), and self-reported daily impairments assessed through various questionnaires.
• Exploring serum biomarkers, including soluble FAP and cytokines/growth factors, and cellular phenotypes of inflammation and remodeling in relation to FAP uptake.

The clinical trial focuses on individuals experiencing **post-acute sequelae of COVID-19**, specifically targeting those with persistent dyspnea and fatigue. The study population includes adult participants over the age of 20, encompassing both male and female subjects. The trial does not involve a vulnerable population. Participants were selected based on self-reported complaints of dyspnea or fatigue persisting for more than three months following a confirmed SARS-CoV-2 infection. The trial includes two groups: one with a Fatigue Severity Scale score of 4 or higher at the time of the [68Ga]FAPI-PET/CT, and another with a score below 4 after previously recording a score of 4 or higher. Additionally, if necessary, 'healthy' controls without self-reported complaints or past SARS-CoV-2 infection may be included from the Lifelines or PARASOL cohort. The sponsor has not provided information regarding the total number of participants. Lifestyle factors such as diet and physical activity are not specified in the available data.

The clinical trial is designed to evaluate pulmonary **fibroblast** activity in patients experiencing post-acute sequelae of COVID-19, specifically focusing on those with long COVID symptoms such as dyspnea and fatigue. This study employs a **randomized**, double-blind, controlled trial design to ensure the reliability and validity of the results. The trial is expected to commence recruitment in January 2025 and conclude by January 2026, with the total duration of participant involvement being approximately one year.

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as age (over 20 years) and self-reported symptoms persisting for more than three months post-SARS-CoV-2 infection. The primary endpoint is the target-to-background ratio of the lung (TBRLung) differences per group, while secondary endpoints include various measures of [68Ga]FAPI uptake and its correlation with health metrics and biological markers.

Following the screening, participants will attend follow-up visits where [68Ga]FAPI-PET/CT scans will be conducted to assess fibroblast activity. These visits will also involve the collection of data on lung function, fatigue severity, and other health metrics. The end-of-study visit will mark the completion of the trial for each participant, where final assessments and data collection will occur.

Participants are expected to remain in the study for its entire duration unless specific conditions necessitate early termination. Such conditions include the development of adverse reactions to the investigational product, non-compliance with study procedures, or withdrawal of consent. The investigational product, [68Ga]FAPI-46, is administered via intravenous injection, with a maximum daily dose of 220 MBq/ml. The trial is not classified as a low-intervention study and is categorized as a phase-IV trial, focusing on the post-acute sequelae of COVID-19.

The clinical trial involves the administration of the experimental medication **[68Ga]FAPI-46**, which is a **solution for injection**. The active substance in this formulation is chemically synthesized and is identified as (S)-2,2',2''-(10-(2-(4-(3-((4-(2-(2-cyano-4,4-difluoropyrrolidin-1-yl)-2-oxoethylcarbamoyl)-quinolin-6-yl)(methyl)amino)-propyl)piperazin-1-yl)-2-oxoethyl)-68Ga-[1,4,7,10]-tetraazacyclododecane-1,4,7-triyl)triacetate. The medication is administered via **intravenous administration**. The maximum daily dose and total dose are both set at 220 MBq/ml, with the treatment period limited to a single day. The formulation is not intended for pediatric use and is not classified as an orphan drug.

In this study, no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are utilized. The focus is solely on the administration of the experimental drug **[68Ga]FAPI-46**. Participant compliance with the dosing schedule is monitored to ensure adherence to the protocol. The trial aims to evaluate the pulmonary fibroblast activity in patients with long COVID symptoms, using **[68Ga]FAPI-PET/CT** imaging as a diagnostic tool.

Efficacy in this clinical trial will be assessed by evaluating the pulmonary fibroblast activity using **[68Ga]FAPI-PET/CT** imaging. The primary endpoint for efficacy is the Target to Background Ratio of the Lung (TBRLung) differences per group. Secondary endpoints include the Standardized Uptake Value (SUVmean and SUVmax) of both paravertebral muscles, and the **[68Ga]FAPI** uptake (SUVmean) in relation to various parameters. These parameters include the percentage of ground glass opacities (GGO) on high-resolution CT, outcomes from multiple questionnaires, patient health metrics such as lung function and the 6-Minute Walk Test (6-MWT), and biological markers including circulating extracellular matrix fragments, circulating soluble FAP, inflammatory blood markers, and systemic and upper respiratory tract cellular phenotypes.

The trial aims to determine if pulmonary fibroblast activity is higher in patients with current long COVID dyspnea and fatigue compared to those with resolved complaints. The efficacy assessments will be conducted at specific timepoints, with the Fatigue Severity Scale being used to categorize patients into groups based on their fatigue levels at the time of **[68Ga]FAPI-PET/CT** imaging. The trial is designed to provide insights into the personalized diagnosis of post-acute sequelae of COVID-19 by correlating imaging findings with clinical and biological data.