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Updated: Sep 3, 2025
Biotinylated Cell-penetrating Peptides to Study Intracellular Protein-protein Interactions
Published on: December 20, 2017
A Broad-Based Characterization of a Cell-Penetrating, Single Domain Camelid Bi-Specific Antibody Monomer That Targets
Sunanda Singh1, Genoveva Murillo2, Justin Richner3
1Singh Biotechnology, 1547 Fox Grape Loop, Lutz, FL 33558, USA.
Abstract:
STAT3 and KRAS regulate cell proliferation, survival, apoptosis, cell migration, and angiogenesis. Aberrant expression of STAT3 and mutant active forms of KRAS have been well-established in the induction and maintenance of multiple cancers. STAT3 and KRAS mutant proteins have been considered anti-cancer targets; however, they are also considered to be clinically "undruggable" intracellular molecules, except for KRAS(G12C). Here we report a first-in-class molecule, a novel, single domain camelid VHH antibody (15 kDa), SBT-100, that binds to both STAT3 and KRAS and can penetrate the tumor cell membrane, and significantly inhibit cancer cell growth. Additionally, SBT-100 inhibits KRAS GTPase activity and downstream phosphorylation of ERK in vitro. In addition, SBT-100 inhibits the growth of multiple human cancers in vitro and in vivo. These results demonstrate the feasibility of targeting hard-to-reach aberrant intracellular transcription factors and signaling proteins simultaneously with one VHH to improve cancer therapies.
Insights
A novel antibody, SBT-100, effectively targets both STAT3 and KRAS proteins, inhibiting cancer cell growth. This breakthrough offers a new approach for treating cancers driven by these difficult-to-drug intracellular targets.
Area of Science:
- Oncology
- Molecular Biology
- Immunotherapy
Background:
- Signal transducer and activator of transcription 3 (STAT3) and Kirsten rat sarcoma virus (KRAS) are key regulators of cell functions implicated in cancer.
- Aberrant STAT3 and mutant KRAS are prevalent in numerous cancers, presenting significant therapeutic challenges due to their intracellular localization and
- undruggable
- nature, with exceptions like KRAS(G12C).
Purpose of the Study:
- To develop and evaluate a novel therapeutic agent capable of simultaneously targeting both STAT3 and mutant KRAS intracellularly.
- To assess the efficacy of this agent in inhibiting cancer cell proliferation and tumor growth.
Main Methods:
- Development of a single-domain camelid VHH antibody (SBT-100) designed to bind STAT3 and KRAS.
- In vitro assessment of SBT-100's ability to inhibit KRAS GTPase activity and downstream signaling (ERK phosphorylation).
- Evaluation of SBT-100's anti-cancer effects on multiple human cancer cell lines and in vivo tumor models.
Main Results:
- SBT-100, a novel VHH antibody, successfully binds to both STAT3 and KRAS, penetrating tumor cell membranes.
- SBT-100 demonstrated significant inhibition of cancer cell growth in vitro and in vivo.
- The antibody effectively inhibited KRAS GTPase activity and downstream ERK phosphorylation in vitro.
Conclusions:
- Simultaneous targeting of intracellular proteins STAT3 and KRAS with a single VHH antibody is feasible.
- SBT-100 represents a first-in-class therapeutic candidate with potential to overcome challenges in targeting
- undruggable
- cancer targets.
- This approach holds promise for improving the efficacy of cancer therapies by addressing multiple oncogenic drivers concurrently.
