Abstract PO4-18-11: Phase 1 study of the tissue factor-targeting antibody-drug conjugate XB002 in patients with advanced solid tumors (JEWEL-101): Design of the triple-negative and hormone receptor-positive breast cancer expansion cohorts
Authors: Ulahannan Susanna , Johnson Melissa , Weiss Mia , Vandross Andrae , Vidal-Cardenas Sofia , Syed Mustafa , Tolcher Anthony 
Published: May 2024

Background: Tissue factor (TF) is a transmembrane protein that functions as a factor VIIa receptor, initiating the extrinsic coagulation cascade. TF is aberrantly expressed in multiple solid tumors, including breast cancer (BC), and its expression is associated with disease progression and poor prognosis (van den Berg et al. Blood 2012). Microtubule-targeting agents are a cornerstone of treatment for metastatic BC. XB002 is a novel antibody-drug conjugate (ADC) composed of a high-affinity TF-directed human monoclonal antibody conjugated to the zovodotin linker-payload. Zovodotin consists of an auristatin-based payload and a protease-cleavable linker and is designed to lower off-target deconjugation and improve tolerability compared with other microtubule inhibitor linker-payloads. In preclinical studies, XB002 did not interfere with coagulation and demonstrated antitumor activity with an encouraging safety profile. XB002 is being evaluated in JEWEL-101, an ongoing trial in patients (pts) with advanced solid tumors, including BC. Preliminary results from the dose-escalation stage of JEWEL-101 showed XB002 was well tolerated at multiple dose levels with no bleeding events or treatment-related peripheral neuropathy (PN) and low-grade ocular toxicity (Ulahannan et al. ENA 2022). Presented here is the study design of the tumor-specific expansion stage, including triple-negative BC (TNBC) and hormone receptor-positive BC (HR+ BC) cohorts.

Trial design and statistical methods: JEWEL-101 (NCT04925284) is a multicenter, open-label, phase 1 trial evaluating the safety, tolerability, pharmacokinetics (PK), and antitumor activity of XB002 in advanced solid tumors. Single-agent XB002 at the recommended dose will be assessed in the BC expansion cohorts utilizing Simon’s Two-Stage design.

Eligibility criteria: The trial will enroll adult pts with TNBC (ER-/PR-/HER-2-negative or low) and HR+ BC (ER+ and/or PR+ and HER-2-negative or low) into 2 separate cohorts. HER-2 negativity is defined as either HER-2 negative or low by local ISH or IHC assessment. For both cohorts, pts must have received 1–3 lines of prior systemic anticancer therapies for locally advanced or metastatic disease. Pts in the HR+ BC cohort must have received prior endocrine therapy and CDK4/6 inhibitor. All pts must have cytologically or histologically and radiologically confirmed BC that is inoperable, locally advanced, metastatic, or recurrent. Documented radiographic progression during or following their last systemic anticancer therapy is required. All pts must also have measurable disease per RECIST 1.1 by investigator assessment, archival (&lt; 2 years) or fresh tumor tissue, ECOG PS 0 or 1, and adequate organ and marrow function. Pts with grade 1 PN are allowed. Concomitant anticoagulation therapy while receiving XB002 is permitted if clinically indicated. Key exclusions are prior use of TF-targeting or auristatin derivate-based ADC; uncontrolled, significant intercurrent or recent illness, including acute or chronic significant ocular disorders; major surgery within 4 weeks; and corrected QT interval calculated by the Fridericia formula &gt;480 ms per ECG.

Specific aims: The primary objective of the expansion stage is to evaluate the preliminary efficacy of XB002 by estimating the objective response rate per RECIST 1.1 as assessed by the investigator. Secondary objectives include safety and tolerability, PK, immunogenicity, progression-free survival, duration of response, and overall survival.

Accrual: Up to 28 pts will be enrolled into each BC cohort. Enrollment is planned across sites in the US, Europe, and Asia-Pacific.

Contact information: Exelixis Clinical Trials, druginfo@exelixis.com, 1-888-393-5494

Citation Format: Susanna Ulahannan, Melissa Johnson, Mia Weiss, Andrae Vandross, Sofia Vidal-Cardenas, Mustafa Syed, Anthony Tolcher. Phase 1 study of the tissue factor-targeting antibody-drug conjugate XB002 in patients with advanced solid tumors (JEWEL-101): Design of the triple-negative and hormone receptor-positive breast cancer expansion cohorts [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-18-11.