Targeting Viral RNA Using a Sequence Programmable Small Molecule-Oligonucleotide Conjugate

PROJECT 1: TARGETING VIRAL RNA USING A SEQUENCE PROGRAMMABLE SMALL MOLECULE- OLIGONUCLEOTIDE CONJUGATE SUMMARY We propose to merge small molecule and antisense oligonucleotide (ASO) approaches to specifically inhibit viral RNA translation without inhibiting the translation of endogenous cellular mRNAs. Rocaglate natural products, such as rocaglamide A (Roc), demonstrate a unique RNA-targeting mechanism by which small molecule binding to a bimolecular cavity between eIF4A helicase and polypurine RNA (stretches of A and G) generates a steric clamp on the 5’ untranslated regions (UTRs) of target mRNAs. Due to obstruction of the scanning ribosome, this rocaglamide-mediated clamp results in translational inhibition of polypurine tract-containing mRNAs, including that of SARS-CoV-2 and other positive-sense RNA viruses. While pre-clinical viral replication assays indicate that zotatifin, a clinical candidate based on rocaglamide, may demonstrate a promising therapeutic window as an anti-viral, it is anticipated that the simultaneous inhibition of multiple polypurine tract-containing mRNAs within the cell could result in dose-limiting toxicities. We position rocaglamide as a unique protein-RNA molecular glue that can be directed to specific viral target sequences through the appendage of an additional RNA-targeting chemical element. We have designed rocaglamide-ASO (RocASO) molecules which link rocaglamide to an ASO whose binding is dependent upon complementary base-pairing with target RNA sequences. A model that juxtaposes the two therapeutic modalities reveals a permissible disposition of the two binding elements approximately 20 ÃÂ... apart, which will be traversed by a variable chemical tether of sufficient length. RocASOs designed against the 5’ UTR of SARS-CoV-2 will be tested using biochemical ternary complex formation assays with eIF4A and viral RNA, as well as assayed using cellular reporters of SARS-CoV-2 5’ UTR translation and RNA stability. Finally, we will apply RocASOs in a SARS-CoV-2 replicon system to determine the relative tolerance of RocASOs to polypurine tract or ASO recognition sequence mutations. These experiments will also evaluate whether potentially emergent alterations to target sequences could be addressed by introducing concomitant modifications to RocASOs, assessing the platform as an adaptable RNA targeting modality for novel SARS-CoV-2 variants and other viral 5’ UTR sequences.