Mirati Therapeutics Presents Preclinical Data on Novel Approach to PRMT5 Inhibition that Selectively Targets the PRMT5/MTA Complex in MTAP-Deleted Cancer Models

SAN DIEGO, April 10, 2021 /PRNewswire/ -- Mirati Therapeutics, Inc. (NASDAQ: MRTX), a late-stage targeted oncology company, today announced initial preclinical results evaluating its investigational synthetic lethal PRMT5 inhibitor in methylthioadenosine phosphorylase (MTAP)-deleted cancer models. Mirati's internally discovered PRMT5 compound is the first to specifically target the PRMT5/methylthioadenosine (MTA) complex. This approach is designed to leverage elevated levels of MTA in cancers exhibiting an MTAP deletion and to selectively kill cancer cells harboring this genetic alteration. The results were presented today during a late-breaking minisymposium at the 2021 American Association for Cancer Research (AACR) Virtual Annual Meeting [Abstract # LB003].

Preclinical results showed that the Mirati PRMT5 compound bound selectively to the PRMT5/MTA complex and demonstrated a greater than 100-fold selectivity for MTAP-deleted cells compared with cells that do not exhibit this genetic defect in both proliferation and mechanistic assays. This selectivity for the PRMT5/MTA complex and MTAP-deleted cancer cells allows for the selective targeting of cancer cells while sparing healthy cells, which are also dependent on PRMT5 for cell growth and survival. In addition, treatment of MTAP-deleted tumor xenograft-bearing mice with the Mirati PRMT5 compound resulted in halted tumor growth and near complete reduction of symmetric dimethylarginine (SDMA), a biomarker of PRMT5 activity, at well-tolerated dose levels.  

"We are proud to have a potential first-in-class therapeutic agent to specifically target the PRMT5/MTA complex in MTAP-deleted cancer cells," said James Christensen, Ph.D., executive vice president and chief scientific officer, Mirati Therapeutics, Inc. "Based on discoveries made by Mirati scientists, we have designed a novel approach to specifically bind to and inhibit PRMT5 in complex with MTA. With this approach, we are able to target MTAP-deleted tumors, which should result in an improved therapeutic index relative to known PRMT5 and MAT2A inhibitors."

About PRMT5 Inhibition in MTAP-deleted Cancers

PRMT5 is an enzyme critical to the survival of both healthy and cancer cells and is partially inhibited by MTA, which accumulates in MTAP-deleted cancers. The MTAP deletion is present in approximately 10 percent of all cancers and is the most frequently observed gene deletion event (MTAP/CDKN2A) across several cancer types. Cancers with an MTAP deletion, such as pancreatic, lung, and bladder cancers, are associated with a poor prognosis, representing a significant unmet medical need.

Activated PRMT5 is crucial for the regulation of cellular processes essential for cell survival, including regulation of RNA splicing, gene expression and protein translation. In MTAP-deleted cancer cells, the inhibitory cofactor MTA accumulates and binds to PRMT5.  Mirati's PRMT5 compound selectively targets the PRMT5/MTA complex in MTAP-deleted cancer cells while sparing healthy cells. The Mirati PRMT5 compound is advancing toward an Investigational New Drug (IND) filing in the first half of 2022.

About Mirati Therapeutics

Mirati Therapeutics is a late-stage biotechnology company whose mission is to discover, design and deliver breakthrough therapies to transform the lives of patients with cancer and their loved ones. The company is relentlessly focused on bringing forward therapies that address areas of high unmet need, including lung cancer, and advancing a pipeline of novel therapeutics targeting the genetic and immunological drivers of cancer. Mirati is using its scientific expertise to develop novel solutions in two registration-enabling programs: adagrasib (MRTX849), an investigational small molecule, potent and selective KRAS G12C inhibitor, as monotherapy and in combination with other agents, and sitravatinib, an investigational spectrum-selective inhibitor of receptor tyrosine kinases in combination with checkpoint inhibitor therapies. Mirati is also advancing its differentiated preclinical portfolio, including MRTX1133, an investigational KRAS G12D inhibitor, and other oncology discovery programs. Unified for patients, Mirati's vision is to unlock the science behind the promise of a life beyond cancer.

For more information about Mirati Therapeutics, visit us at Mirati.com or follow us on Twitter and LinkedIn.  

Forward Looking Statements

This press release contains forward-looking statements regarding the business of Mirati Therapeutics, Inc. ("Mirati"). Any statement describing Mirati's goals, expectations, financial or other projections, intentions or beliefs, development plans and the commercial potential of Mirati's drug development pipeline, including without limitation adagrasib (MRTX849), sitravatinib and MRTX1133, is a forward-looking statement and should be considered an at-risk statement. Such statements are subject to risks and uncertainties, particularly those challenges inherent in the process of discovering, developing and commercialization of new drug products that are safe and effective for use as human therapeutics, and in the endeavor of building a business around such drugs.

Mirati's forward-looking statements also involve assumptions that, if they never materialize or prove correct, could cause its results to differ materially from those expressed or implied by such forward-looking statements. Although Mirati's forward-looking statements reflect the good faith judgment of its management, these statements are based only on facts and factors currently known by Mirati. As a result, you are cautioned not to rely on these forward-looking statements. These and other risks concerning Mirati's programs are described in additional detail in Mirati's quarterly reports on Form 10-Q and annual reports on Form 10-K, which are on file with the U.S. Securities and Exchange Commission (the "SEC") available at the SEC's Internet site (www.sec.gov).These forward-looking statements are made as of the date of this press release, and Mirati assumes no obligation to update the forward-looking statements, or to update the reasons why actual results could differ from those projected in the forward-looking statements, except as required by law. 

Mirati Contacts
Investor Relations
Temre Johnson
(858) 332-3562
ir@mirati.com

Media Relations
Priyanka Shah
(908) 447-6134
media@mirati.com

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SOURCE Mirati Therapeutics, Inc.