CD44 splice variants as novel antibody-targets for advanced breast cancer
openNCI - National Cancer Institute
Project Summary
Few therapeutic options exist for triple-negative and heavily treated, hormone receptor-positive metastatic breast
cancer (BC) patients. Antibody-drug conjugates (ADCs) improve overall survival for BC patients with low-HER2
expressing tumors by [Trastuzumab deruxtecan (T-DXd), Datopotamab deruxtecan (Dato-DXd), or Sacituzumab
govitecan (SG)], but these strategies fail when HER2 targeting is not possible. Moreover, most patients who
qualify and respond to T-DXd, Dato-DXd, or SG will relapse or progress, leaving even fewer therapeutic options
available. Novel treatments that improve outcomes for patients who relapse after the current standard of care
ADCs remain a critical clinical need.
We propose a novel ADC-based therapeutic platform for aggressive and resistant BC to address two issues that
continue to hamper the development and adoption of ADCs for clinical use: high treatment-associated toxicities
due to on-target, off-tumor effects and poor tumor penetration. We will overcome these challenges with two
specific technical advances: (1) development of conditionally-active antibodies with enhanced binding to
antigens in the tumor microenvironment to minimize impacts on healthy tissues, and (2) drug conjugation via
cyclic peptides, including an Arg-Gly-Asp tumor-penetrating peptide, and a neutrophil-elastase resistant linker
(EGCit) to enhance drug penetration into tumors. To evaluate our ADC, we will target CD44 variant 9 (CD44v9),
a marker associated with poor patient outcomes and overexpressed in the subgroup of BC patients who are
resistant or unresponsive to HER2-targeted therapy; notably >50% of all BC are Her2-low and CD44v9+. We
hypothesize that antibodies binding the novel CD44v9 target and engineered for optimized selectivity and
payload penetration will effectively home to and kill aggressive breast cancer. We will achieve this objective by
developing tumor-selective antibodies binding CD44v9 (Aim 1), creating anti-CD44v9 ADCs equipped with
tumor-penetrating peptides (Aim 2), and evaluating the efficacy of the ADCs and CD44v9 antibodies in orthotopic
and humanized mouse models of HER2-negative BC and BC that is resistance to FDA-approved ADCs (Aim 3).
This project is technically innovative for its development of conditionally-active antibodies, the use of tumor-
penetrating peptides, the introduction of a novel linker, the evaluation of CD44v9 as a novel target, and the
combination of these elements into a single ADC. The results will provide proof of concept for a novel ADC
platform for aggressive or drug-resistant BC and provide mechanistic insights into the biological role of CD44v9
in BC. When successful, the newly developed ADCs will offer a critical path forward for patients with aggressive
BC who have limited treatment options.
Up to $669K
health research