Agnostic Therapy in Rare Solid Tumors

The ANTARES study is a phase II "basket" trial designed to evaluate the tissue-agnostic efficacy of the monoclonal anti-PD1 antibody, nivolumab, in patients with advanced or metastatic rare tumors. A "basket" trial is an innovative type of clinical trial where patients with different types of cancers, but sharing a common molecular feature (in this case, PD-L1 expression), are treated with the same therapy, regardless of the tumor's site of origin. This approach allows for the evaluation of treatments targeting specific molecular characteristics, independent of the primary cancer type. Rare tumors, as defined by the World Health Organization (WHO), have an incidence of fewer than six cases per 100,000 people per year. Although each rare cancer type is individually uncommon, collectively they account for 25-30% of all malignancies and are often underrepresented in clinical trials due to recruitment challenges and limited funding. As a result, patients with rare cancers generally have a poorer prognosis compared to those with more common tumors. In this study, patients with advanced or refractory rare malignancies expressing PD-L1, with a combined positive score (CPS) of ≥10, will be treated with nivolumab. Treatment will be administered until disease progression or for a maximum duration of 12 months, aiming to assess the efficacy and safety of this tissue-agnostic immunotherapy approach. Efficacy will be measured according to RECIST v1.1 criteria, with objective response as the primary endpoint. Additionally, the study will assess response biomarkers, including PD-L1, circulating tumor DNA (ctDNA), and microvesicles, to better understand the correlation between biomarker expression and clinical outcomes. This multicenter trial, with an estimated duration of four years, will be conducted at Institute of Cancer of the State of São Paulo (ICESP) and other partner institutions. The study aims to overcome existing barriers in rare cancer treatment by offering an innovative approach that explores the potential of personalized therapies based on molecular characteristics, rather than the tumor's primary site