Mirati Announces IND Clearance By U.S. FDA Enabling Phase 1 Initiation For First-In-Class Oral KRASG12D Selective Inhibitor, MRTX1133

IND demonstrates Mirati's leadership in KRAS, representing the Company's third KRAS or KRAS-signaling program to enter clinical development

San Diego, CA /PRNewswire/ - Mirati Therapeutics, Inc. (NASDAQ: MRTX), announced today the U.S. Food and Drug Administration (FDA) has cleared the Investigational New Drug (IND) application of MRTX1133, a potential first-in-class oral KRASG12D selective inhibitor for clinical evaluation. KRASG12D mutations impact approximately 180,000 patients in the US and Europe, representing approximately a 2.5-fold increase in prevalence compared to KRASG12C mutations. No targeted oncology treatment options currently exist for these patients.

MRTX1133 is a highly potent investigational inhibitor of the KRASG12D driver mutation and demonstrated selective and reversible inhibition of KRASG12D in both its active and inactive states. In addition, MRTX1133 administration resulted in marked tumor response in preclinical KRASG12D mutated pancreatic cancer models as well as lung and colorectal cancer models. MRTX1133 has demonstrated favorable properties including a low risk for off-target activity and drug interactions and a predicted human half-life of greater than 50 hours.

"The clearance by the FDA to initiate clinical evaluation of MRTX1133, the third program in our KRAS franchise to enter clinical development, is illustrative of the innovative approach to drug discovery and demonstrates the best-in-class capabilities of the Mirati team. This particular mutation has been difficult to target, and we are confident in our novel oral formulation strategy, which we believe will enable near-complete target inhibition over the full dosing interval," said James Christensen, Ph.D. chief scientific officer, Mirati Therapeutics, Inc. "We are thrilled to advance MRTX1133 into clinical development and the potential to positively impact people living with KRASG12D-mutated cancers."

The Phase 1/2 clinical trial will launch in early 2023 with plans for multiple expansion cohorts in pancreatic, colorectal, lung and other KRASG12D tumor types.

About Mirati Therapeutics, Inc.
Mirati Therapeutics, Inc. is a 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. Unified for patients, Mirati's vision is to unlock the science behind the promise of a life beyond cancer.

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

About MRTX1133
MRTX1133 is an investigational, highly potent, selective and reversible small molecule inhibitor of KRASG12D that is optimized to sustain near complete target inhibition with the potential to be both a first and best-in-class treatment option. MRTX1133 is entering Phase 1 clinical evaluation in 2023 investigating the drug's impact on KRASG12D-driven cancers. For more information visit Mirati.com/science.

Forward Looking Statements
tential of KRAZATITM (adagrasib), sitravatinib (TAM receptor inhibitor), MRTX1719 (MTA-cooperative PRMT5 inhibitor), MRTX0902 (SOS1 inhibitor), and MRTX1133 (selective KRASG12D inhibitor), Mirati's technologies and Mirati' other products in development. Any statement describing Mirati' goals, expectations, intentions or beliefs, financial or other projections, is a forward-looking statement and should be considered an at-risk statement. Such statements are subject to certain risks and uncertainties, including those related to the impact COVID-19 could have on our business, and including those inherent in the process of discovering, developing and commercializing medicines that are safe and effective for use as human therapeutics, and in the endeavor of building a business around such medicines.

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' annual report on Form 10-K, and most recent Form 10-Q, which are on file with the Securities and Exchange Commission and 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.