Evaluation of 68Ga-FAPI-46 PET/CT for Predicting Histological Response to Neoadjuvant Chemo-Immunotherapy in Early-Stage High-Risk Triple-Negative Breast Cancer

The primary objective of this clinical trial is to evaluate whether the **Total FAP-expressing tumor burden (TFTB)**, a biomarker derived from initial **68Ga-FAPI-46 PET-CT** imaging, can accurately predict the histological response to treatment in patients with early-stage high-risk triple-negative breast cancer (TNBC) undergoing neoadjuvant chemotherapy combined with pembrolizumab. This is clinically relevant as it may enhance the ability to tailor treatment strategies based on individual tumor characteristics, potentially improving patient outcomes.

Secondary objectives include:

• Comparing **68Ga-FAPI-46 PET/CT** imaging with **18F-FDG PET/CT** imaging in detecting metastases and assessing total tumor burden.
• Evaluating the predictive value of biomarkers extracted from both imaging modalities and their combination.
• Developing a model from imaging data to predict histological response post-chemo-immunotherapy.
• Exploratory: Comparing functional imaging data of FAP+ CAFs with histological evaluations of CAF subpopulations, tumor-infiltrating lymphocytes (TILs), and tumor PD-L1 expression.
• Exploratory: Assessing the impact of circulating tumor DNA (ctDNA) as a real-time method to monitor tumor burden and heterogeneity before and after neoadjuvant treatment, and its correlation with initial PET/CT scans and clinical outcomes.

The clinical trial involves participants diagnosed with **breast cancer**, specifically focusing on early-stage high-risk triple-negative breast cancer (TNBC). The study population comprises females aged 18 years and older, with no male participants included. Participants are required to have previously untreated, non-metastatic TNBC, with measurable targets according to RECIST/PERCIST criteria and no distant metastasis as confirmed by staging 18F-FDG PET/CT. The trial does not include vulnerable populations. Participants must have tumor tissue available and be able to comply with protocol requirements. They are also required to be covered by a health insurance system. The sponsor has not provided information regarding the total number of participants. The selection criteria emphasize the need for participants to have a centrally confirmed diagnosis of TNBC and to be suitable candidates for neoadjuvant chemotherapy plus pembrolizumab as a standard care option. Participants must have signed a written informed consent to be included in the study.

The clinical trial is designed to evaluate the efficacy of **68Ga-FAPI-46** PET/CT imaging in predicting histological response to neoadjuvant chemo-immunotherapy in patients with triple-negative **breast cancer**. 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 on June 15, 2024, and conclude by June 15, 2029, with the primary objective of assessing the predictive performance of the imaging technique in terms of the area under the ROC curve (AUC).

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as age, cancer stage, and treatment history. Following the initial screening, participants will receive the investigational product, **68Ga-FAPI-46**, via intravenous infusion. Subsequent follow-up visits will be scheduled to monitor the participants' response to the treatment and to perform additional imaging assessments. The end-of-study visit will involve a comprehensive evaluation of the participants' histological response to the treatment regimen.

The expected duration of participant involvement in the trial is approximately five years, aligning with the overall trial duration. Participants may be subject to early termination from the study if they experience adverse reactions, fail to comply with protocol requirements, or withdraw consent. The trial aims to provide valuable insights into the potential of **68Ga-FAPI-46** PET/CT imaging as a predictive tool for treatment response in triple-negative breast cancer, thereby contributing to the optimization of therapeutic strategies for this patient population.

The clinical trial involves the administration of **68Ga-FAPI-46**, an experimental radiopharmaceutical agent. This compound is provided as an **intravenous infusion** and is identified by the sponsor product code **[68Ga]Ga-FAPI-46**. The active substance is a chemically synthesized compound, specifically (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 administration route is intravenous, and the frequency of administration is determined by the study protocol.

**Paclitaxel Kabi** is utilized as a comparator treatment in the study. It is a **solution for infusion** with a concentration of 6 mg/ml. The active substance, **paclitaxel**, is a chemically derived compound. The administration is performed via intravenous infusion, adhering to the standard dosing schedules as per clinical guidelines.

**Cyclophosphamid beta** is another comparator treatment, provided as a **solution for injection/infusion** with a concentration of 500 mg/ml. The active substance is **cyclophosphamide**, a chemical compound. This medication is administered through intravenous infusion, following established dosing protocols.

**Epirubicin Eugia** is included in the trial as a **solution for injection** with a concentration of 2 mg/ml. The active substance is **epirubicin hydrochloride**, a chemical agent. Administration is conducted via intravenous infusion, in accordance with standard clinical practices.

**DOXORUBICINE ARROW** is administered as a **solution for infusion** with a concentration of 2 mg/ml. The active substance is **doxorubicin hydrochloride**, a chemical compound. This treatment is delivered through intravenous infusion, following conventional dosing regimens.

**CARBOPLATINE MEDAC** is provided as a **solution for infusion** with a concentration of 10 mg/ml. The active substance is **carboplatin**, a chemical compound. Administration is performed via intravenous infusion, adhering to standard dosing schedules.

**KEYTRUDA** is included as a **concentrate for solution for infusion** with a concentration of 25 mg/ml. The active substance is **pembrolizumab**, a protein-based compound. This medication is administered through infusion, following the dosing guidelines specified in the study protocol.

Efficacy in this clinical trial will be assessed primarily through the use of **68Ga-FAPI-46 PET/CT** imaging to predict the histological response to neoadjuvant chemotherapy plus pembrolizumab in patients with early-stage high-risk triple-negative breast cancer (TNBC). The primary endpoint is the measurement of the performance of **68Ga-FAPI-46 PET/CT** imaging in predicting complete histological response, evaluated by the area under the ROC curve (AUC of the ROC curve). Secondary endpoints include the comparison of **68Ga-FAPI-46 PET/CT** and **18F-FDG PET/CT** performances for the detection of metastases and evaluation of tumor burden, as well as the predictive performance of these imaging modalities, both separately and combined. The trial will also explore the correlation of **68Ga-FAPI-46 PET/CT** imaging data with histological evaluation of cancer-associated fibroblast (CAF) subpopulations, immune microenvironment, and the sensitivity of imaging compared to histology. Additionally, quantitative analysis of circulating tumor DNA (ctDNA) before and after neoadjuvant treatment will be conducted, correlating these findings with biomarkers from initial PET/CT scans and histological response. The efficacy assessments will be conducted using sensitivity, specificity, positive and negative predictive values, and AUC of the ROC curve.