Sorrento Announces Its Oral SARS-CoV-2 Main Protease (Mpro) Inhibitor, STI-1558, Strongly Neutralizes Omicron

Excerpt from the Press Release:

• STI-1558, a novel oral Mpro inhibitor, effectively inhibits Omicron virus entry and replication in cells.
• STI-1558 is orally bioavailable with improved human liver microsomal stability to avoid using Ritonavir as a pharmacokinetic enhancer in humans.

SAN DIEGO, Jan. 28, 2022 (GLOBE NEWSWIRE) — Sorrento Therapeutics, Inc. (Nasdaq: SRNE, “Sorrento”) today announced its late-stage preclinical M^pro inhibitor, STI-1558, effectively inhibits Omicron virus entry and replication in cell-based assays.

The world is experiencing a huge wave of infection with the Omicron variant of SARS-CoV-2, and current vaccines and EUA-approved antibodies offer diminished protection against Omicron transmission and infection. STI-1558 is an oral M^pro inhibitor which has demonstrated in preclinical studies broad-spectrum anti-SARS-CoV-2 activity when tested for activity against the original SARS-CoV-2 strain and all previous predominant variants of concern (VOCs).

STI-1558’s antiviral activity against Omicron has also been tested in a cell-based neutralization assay. In VeroE6 cells challenged with Omicron variant, STI-1558 alone (without efflux inhibitor) showed significant antiviral activity with an EC₅₀ value of 360 nM, equivalent activity to that seen against the Delta variant (EC₅₀ value, 370 nM). Notably, in an Omicron S protein-mediated pseudovirus entry assay, STI-1558 effectively inhibited pseudovirus entry into cells, whereas EUA-approved nirmatrelvir showed no inhibition. Particularly, STI-1558 showed improved human liver metabolic stability as compared to nirmatrelvir, and its oral bioavailability does not depend on the ritonavir co-administration. Without the need to co-administer Ritonavir, STI-1558 potentially avoids significant adverse drug-drug interactions.

“With Omicron becoming a globally dominant variant of SARS-CoV-2 in such a short period of time, we are focused on developing an effective therapeutic strategy for fighting the Omicron variant and future variants of concern, and most importantly, for preventing or overcoming drug-resistance. Sorrento continues its commitment to develop and deliver effective anti-COVID therapies to save patient lives and end the pandemic,” stated Dr. Henry Ji, Chairman and CEO of Sorrento.

About Sorrento Therapeutics, Inc. 

Sorrento is a clinical and commercial stage biopharmaceutical company developing new therapies to treat cancer, pain (non-opioid treatments), autoimmune disease and COVID-19. Sorrento’s multimodal, multipronged approach to fighting cancer is made possible by its extensive immuno-oncology platforms, including key assets such as fully human antibodies (“G-MAB™ library”), immuno-cellular therapies (“DAR-T™”), antibody-drug conjugates (“ADCs”), and oncolytic virus (“Seprehvec™”).

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