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

• 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™”). Sorrento is also developing potential antiviral therapies and vaccines against coronaviruses, including Abivertinib, COVI-AMG™, COVISHIELD™, COVI-MSC™ and COVIDROPS™; and diagnostic test solutions, including COVITRACK™ and COVISTIX™.

Sorrento's commitment to life-enhancing therapies for patients is also demonstrated by our effort to advance a first-in-class (TRPV1 agonist) non-opioid pain management small molecule, resiniferatoxin (“RTX”), and SP-102 (10 mg, dexamethasone sodium phosphate viscous gel) (SEMDEXA™), a novel, viscous gel formulation of a widely used corticosteroid for epidural injections to treat lumbosacral radicular pain, or sciatica, and to commercialize ZTlido® (lidocaine topical system) 1.8% for the treatment of post-herpetic neuralgia (PHN). RTX has cleared for Phase II trial for intractable pain associated with cancer and a Phase II trial in osteoarthritis patients. SEMDEXA announced highly statistically significant positive top-line results from its Phase III Pivotal Trial C.L.E.A.R Program for its novel, non-opioid product for the treatment of lumbosacral radicular pain (sciatica). ZTlido® was approved by the FDA on February 28, 2018.

For more information visit www.sorrentotherapeutics.com

Forward-Looking Statements

This press release and any statements made for and during any presentation or meeting contain forward-looking statements related to Sorrento Therapeutics, Inc., under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995 and subject to risks and uncertainties that could cause actual results to differ materially from those projected. Forward-looking statements include statements regarding STI-1558, including the potential antiviral profile of STI-1558 with respect to SARS-CoV-2 and its variants of concern (VOCs); the preclinical testing of STI-1558; the potential safety and efficacy of STI-1558; the potential for STI-1558 to effectively inhibit Omicron virus entry and replication; the expected impact STI-1558 will have against current and future VOCs of SARS-CoV-2, including Omicron; the potential for STI-1558 to exhibit broad-spectrum anti-SARS-CoV-2 activity; the expected formulation, dosing and/or route of administration for STI-1558; and Sorrento’s position in the antiviral industry. Risks and uncertainties that could cause our actual results to differ materially and adversely from those expressed in our forward-looking statements, include, but are not limited to: risks related to Sorrento's technologies and prospects, including, but not limited to risks related to seeking regulatory approval for STI-1558; clinical development risks, including risks in the progress, timing, cost, and results of clinical trials and product development programs; risk of difficulties or delays in obtaining regulatory approvals; risks that clinical study results may not meet any or all endpoints of a clinical study and that any data generated from such studies may not support a regulatory submission or approval; risks that prior test, study and trial results may not be replicated in future studies and trials; risks of manufacturing and supplying drug product; risks related to leveraging the expertise of its employees, subsidiaries, affiliates and partners to assist Sorrento in the execution of its product candidates’ strategies; risks related to the global impact of COVID-19; and other risks that are described in Sorrento's most recent periodic reports filed with the Securities and Exchange Commission, including Sorrento's Annual Report on Form 10-K for the year ended December 31, 2020, and subsequent Quarterly Reports on Form 10-Q filed with the Securities and Exchange Commission, including the risk factors set forth in those filings. Investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release and we undertake no obligation to update any forward-looking statement in this press release except as required by law.

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Contact: Dorman Followwill
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