Screening of DNA-Encoded Small Molecule Libraries inside a Living Cell

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• DNA-encoded small molecule libraries (DELs) are powerful tools for identifying novel therapeutic protein modulators.
• In vivo screening of DELs has been limited by challenges in delivering libraries across cell membranes.

Purpose of the Study:

• To report the first successful screening of a multimillion-member DEL inside a living cell.
• To establish a novel method for in vivo DEL screening using Xenopus laevis oocytes.

Main Methods:

• Utilized large Xenopus laevis oocytes (1 μL) for direct DEL injection, overcoming cell membrane delivery issues.
• Expressed target proteins fused to a prey protein within oocytes for specific DNA labeling and discrimination.
• Screened a 194-million-member DEL against p38α, ACSS2, and DOCK5 protein targets.

Main Results:

• Successfully performed in vivo DEL screening in living cells.
• Identified multiple chemical clusters for all three tested targets (p38α, ACSS2, DOCK5).
• Achieved validated hits with single-digit nanomolar potencies for the p38α target.

Conclusions:

• Demonstrated a powerful new approach for DEL screening in a physiological context.
• Eliminated the need for highly purified target proteins, simplifying the screening process.
• Poised to expand the range of DEL-amenable targets and reduce drug candidate attrition rates.