Prime Medicine (PRME) 8-KPrime Medicine Reports Full Year 2023 Financial Results and Provides Business Updates

“In 2024, we anticipate undergoing a significant transformation, maturing into a clinical-stage company and bringing the first-ever Prime Editing-based therapeutic candidate to patients. We look forward to filing our first IND or CTA in the months ahead, and to commencing our Phase 1 clinical trial in CGD, a serious, life-threatening disease that we believe is uniquely suited for treatment with a Prime Editing-based approach,” said Keith Gottesdiener, M.D., President and Chief Executive Officer of Prime Medicine. “In parallel, we continue to progress our broader pipeline, where we are advancing programs across our core areas of focus: hematology and immunology, liver, lung, ocular and neuromuscular disease. This year, we expect to advance our first liver and ocular disease programs into IND-enabling studies, while continuing to explore business development opportunities that can accelerate our existing work, enable us to pursue additional programs, and provide access to innovation that can further advance Prime Editing. Over time, we believe the modularity of the Prime Editing platform will allow us to quickly build on our current efforts, unlocking opportunities across a wide range of genetic and common diseases, which collectively impact millions of people.”

Prime Medicine expects the following activities and next steps to drive Prime Medicine forward and support the company’s maturation into a clinical-stage company:

Prime Medicine is a leading biotechnology company dedicated to creating and delivering the next generation of gene editing therapies to patients. The Company is deploying its proprietary Prime Editing platform, a versatile, precise and efficient gene editing technology, to develop a new class of differentiated one-time curative genetic therapies. Designed to make only the right edit at the right position within a gene while minimizing unwanted DNA

modifications, Prime Editors have the potential to repair almost all types of genetic mutations and work in many different tissues, organs and cell types. Taken together, Prime Editing’s versatile gene editing capabilities could unlock opportunities across thousands of potential indications.

Prime Medicine is currently progressing a diversified portfolio of investigational therapeutic programs organized around core areas of focus: hematology and immunology, liver, lung, ocular and neuromuscular. Across each core area, Prime Medicine’s initial focus is on genetic diseases with a fast, direct path to treating patients, and those with high unmet need not currently addressable using other gene editing approaches. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential to expand beyond the genetic diseases in its initial pipeline, potentially including immunological diseases, cancers, infectious diseases, and targeting genetic risk factors in common diseases, which collectively impact millions of people. For more information, please visit www.primemedicine.com.

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, implied and express statements about Prime Medicine’s beliefs and expectations regarding: the initiation, timing, progress, and results of its research and development programs, preclinical studies and future clinical trials, and the release of data related thereto; the anticipated maturation into a clinical-stage company and bringing the first-ever Prime Editing-based therapeutic candidate to patients; progressing its broader pipeline across core areas of focus; exploring business development opportunities that could accelerate existing work and the benefits thereof; the modularity of the Prime Editing platform and the benefits thereof; certain activities and next steps to support the company’s maturation into a clinical-stage company, including opening IND and/or CTA applications, clinical data expectations, establishing proof of concept, advancing programs into lead optimization, advancing preclinical studies and initiating IND-enabling activities, nominating development candidates, and establishing delivery platform and rout of administration; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; and the potential of Prime Editing to unlock opportunities across thousands of potential indications. The words “may,” “might,” “will,” “could,” “would,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “expect,” “estimate,” “seek,” “predict,” “future,” “project,” “potential,” “continue,” “target” and similar words or expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

Any forward-looking statements in this press release are based on management’s current expectations and beliefs and are subject to a number of risks, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this press release, including, without limitation, risks associated with: uncertainties related to an IND or CTA filing and entering clinical trials; the authorization, initiation, and conduct of preclinical and IND-enabling studies and other development requirements for potential product candidates, including uncertainties related to opening INDs and obtaining regulatory approvals; risks related to the development and optimization of new technologies, the results of preclinical studies, or clinical studies not being predictive of future results in connection with future studies; the scope of protection Prime Medicine is able to establish and maintain for intellectual property rights covering its Prime Editing technology; Prime Medicine’s ability to identify and enter into future license agreements and collaborations; and general economic, industry and market conditions, including rising interest rates, inflation, and adverse developments affecting the financial services industry. These and other risks and uncertainties are described in greater detail in the section entitled “Risk Factors” in Prime Medicine’s most recent Annual Report on Form 10-K, as well as any subsequent filings with the Securities and Exchange Commission. In addition, any forward-looking statements represent Prime Medicine’s views only as of today and should not be relied upon as representing its views as of any subsequent date. Prime Medicine explicitly disclaims any obligation to update any forward-looking statements subject to any obligations under applicable law. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements.