H3B-8800, an orally available small-molecule splicing modulator, induces lethality in spliceosome-mutant cancers

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Recurrent mutations in RNA splicing factors (SF3B1, U2AF1, SRSF2) are found in various cancers.
• Cancer cells with these mutations exhibit a dependency on wild-type (WT) spliceosome function.
• Current therapeutic strategies to target the spliceosome are limited.

Purpose of the Study:

• To describe a novel orally available modulator of the SF3b complex, H3B-8800.
• To evaluate the efficacy of H3B-8800 in killing spliceosome-mutant cancer cells.
• To elucidate the mechanism of action of H3B-8800.

Main Methods:

• Drug screening and characterization of H3B-8800, an SF3b complex modulator.
• In vitro and in vivo studies using cancer cell lines and patient-derived xenografts.
• Analysis of drug resistance mechanisms and spliceosome activity.

Main Results:

• H3B-8800 potently and preferentially kills spliceosome-mutant epithelial and hematologic tumor cells.
• The drug directly interacts with the SF3b complex, confirmed by drug-resistant mutant studies.
• H3B-8800 induces retention of short, GC-rich introns, particularly those in genes encoding spliceosome components.

Conclusions:

• H3B-8800 demonstrates significant therapeutic potential for spliceosome-mutant cancers.
• Splicing modulation represents a promising strategy for treating cancers with specific splicing factor mutations.
• This study highlights a targeted approach to exploit spliceosome vulnerabilities in cancer therapy.