Boundless Bio Presents Preclinical and Clinical Pharmacodynamic Data on its Lead Extrachromosomal DNA (ecDNA)-Directed Therapy, BBI-355, at the American Association for Cancer Research Annual Meeting 2024 - Seite 2

Title: Preclinical and clinical pharmacodynamic characterization of BBI-355, a novel, orally bioavailable, and selective CHK1 inhibitor being evaluated in the first-in-human Phase 1/2 POTENTIATE clinical trial of patients with cancer harboring oncogene amplifications
Number: 3631
Session Category: Clinical Research
Session Title: Biomarkers in Clinical Trials
Session Date and Time: Monday Apr 8, 2024, 1:30 PM - 5:00 PM PT
Location: Poster Section 40
Poster Board Number: 9

Historically, clinical CHK1 inhibitor programs have lacked effective clinical PD biomarker assays. The findings showed that phosphorylated-CHK1 Ser345 (pCHK1-S345) is a useful pharmacodynamic (PD) biomarker for confirming clinical on-target activity of BBI-355 and could potentially inform the pharmacologically active range of BBI-355 in clinical development. In addition to preclinical data, increased pCHK1-S345 expression by immunohistochemistry in skin biopsies from patients treated with BBI-355 in the ongoing POTENTIATE clinical study were also observed, marking the first, real-time analysis of PD activity from a CHK1 inhibitor in humans.

Title: Extrachromosomal DNA (ecDNA) amplification of multi-drug resistance genes results in acquired resistance to taxane-based chemotherapy
Abstract Number: 5870
Session Category: Experimental and Molecular Therapeutics
Session Title: Mechanisms of Drug Resistance 3
Session Date and Time: Tuesday Apr 9, 2024, 1:30 PM - 5:00 PM PT
Location: Poster Section 24
Poster Board Number: 14

Early insights into the role of ecDNA in driving resistance to paclitaxel, a taxane chemotherapy, are revealed and highlight the importance of ecDNA-directed therapies as a potential treatment option for many patients that have chemotherapy-resistant disease. Chemotherapy remains standard of care for many cancer patients, however, resistance to chemotherapy often develops and has been associated with the emergence of multi-drug resistance (MDR) gene amplification, such as ABCB1. These preclinical findings showed that ecDNA-enabled MDR gene amplification can cause short-and long-term resistance to paclitaxel, potentially driving resistance to chemotherapy in patients and underscoring the broad need for ecDTx for chemotherapy-resistant patient populations.