PRME

-- IND and CTA clearances in the United States and New Zealand establish a global Phase 1/2 program for PM577a in Wilson disease; study startup activities underway, with initial clinical data in 2027 -- -- Favorable arbitration resolution with Beam Therapeutics affirms Prime Medicine’s rights to PM647 in Alpha-1 Antitrypsin Deficiency; IND and/or CTA submission expected in 3Q 2026, with initial clinical data in 2027 -- -- FDA grants Regenerative Medicine Advanced Therapy designation to PM359; continued regulatory engagement with the FDA toward a BLA submission for PM359 in 1H 2027 -- -- Cash, cash equivalents, investments, and restricted cash of $108.8 million as of June 30, 2026, providing cash runway into 2027 -- CAMBRIDGE, Mass., Aug. 06, 2026 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the quarter ended June 30, 2026 and provided a business update. "We have continued to deliver on the focused strategy we laid out last year," said Allan Reine, M.D., Chief Executive Officer of Prime Medicine. "Wilson disease is now cleared to enter the clinic in two geographies. Our rights in Alpha-1 Antitrypsin Deficiency are secure, and the program is advancing toward regulatory submission. And in CGD, where Prime Editing has already shown it can correct disease in humans, we are working toward a BLA filing, and delivering this therapy to patients in need. The opportunity ahead of us is to demonstrate that same potential effect in vivo, in two of the largest genetic diseases targeting the liver." Dr. Reine continued, “We are now entering a transformative phase of growth and value creation potential that extends well beyond this year. We expect to initiate our global Phase 1/2 study of PM577a in the second half of 2026 and to submit an IND and/or CTA for PM647 in the third quarter, with initial clinical data from both programs anticipated in 2027. Alongside our progress toward a potential BLA for PM359, these milestones have the potential to significantly expand the clinical evidence supporting Prime Editing and advance our goal of bringing the first Prime Editing therapies to patients.” Prime Medicine’s Pipeline: Prime Medicine is advancing in vivo programs to cure two of the largest genetic diseases originating in the liver, Wilson disease (WD) and Alpha-1 Antitrypsin Deficiency (AATD). Following clearance of the Company’s Investigational New Drug (IND) application in the United States and Clinical Trial Application (CTA) in New Zealand, PM577a is progressing into a global Phase 1/2 program and study startup activities are underway. Additionally, Prime Medicine expects to submit an IND and/or CTA for PM647 in AATD in the third quarter of 2026. Initial clinical data from both programs are expected in 2027. Prime Medicine is also advancing an in vivo Cystic Fibrosis (CF) program with support from the Cystic Fibrosis Foundation and Prime Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. Additionally, following positive proof-of-concept data from the first two patients treated in its Phase 1/2 study of PM359 for the treatment of chronic granulomatous disease (CGD), and the recent grant of Regenerative Medicine Advanced Therapy (RMAT) designation, Prime Medicine continues to engage in regulatory dialogue with the U.S. Food and Drug Administration (FDA) toward a potential Biologics License Application (BLA) filing for PM359. Recent Corporate Updates: Wilson Disease (PM577a) In June 2026, the New Zealand Medicines and Medical Devices Safety Authority (Medsafe) cleared the Company’s CTA for PM577a, the first clinical authorization for an in vivo Prime Editing therapy from Prime Medicine. In July 2026, the FDA cleared the Company’s IND application for PM577a, opening participation to patients in the United States, where the ATP7B H1069Q variant that PM577a targets is the single most common cause of WD. Together, the two clearances establish a global Phase 1/2 program. The open-label, first-in-human study will evaluate the safety, tolerability, biological activity and efficacy of ascending doses of PM577a in adults and adolescents with WD, initially enrolling adults who are clinically stable on standard-of-care therapy. Prime Medicine has initiated study startup activities, with initial clinical data anticipated in 2027. Alpha-1 Antitrypsin Deficiency (PM647) In July 2026, Prime Medicine announced a positive, binding resolution of its previously disclosed arbitration with Beam Therapeutics, Inc. relating to the parties’ 2019 Collaboration and License Agreement. The Tribunal declared that PM647 is within Prime Medicine’s “Field” as defined by the agreement, that Prime Medicine did not breach the agreement, and that Prime Medicine owes no monetary damages. PM647 leverages Prime Medicine’s universal liver lipid nanoparticle (LNP) to correct the E342K (PiZ) mutation in the SERPINA1* gene, the most prevalent disease-causing mutation in AATD. In fully humanized mouse models, treatment with PM647 achieved high levels of editing efficiency and restored the corrected protein isoform (M-AAT) into the healthy human range at clinically relevant doses. PM647 is built on the same universal liver LNP delivery approach that underpins PM577a. Prime Medicine expects to draw on its experience with PM577a as it advances PM647 toward the clinic, and to benefit from the efficiencies and learnings enabled by its modular approach. Prime Medicine expects to submit an IND and/or CTA for PM647 in the third quarter of 2026, with initial clinical data expected in 2027. Chronic Granulomatous Disease (PM359) In June 2026, the FDA granted RMAT designation to PM359 based on Phase 1/2 clinical data, including data previously published in The New England Journal of Medicine. RMAT provides the benefits of intensive FDA guidance and expedited review, including discussions on surrogate or intermediate endpoints that may support accelerated approval and eligibility for rolling and priority review of a future BLA. PM359 has now received RMAT, Fast Track, Orphan Drug, and Rare Pediatric Disease designations from the FDA. Prime Medicine continues to engage with the FDA on the most efficient path to a BLA submission planned for the first half of 2027. Upcoming Milestones Continue study startup activities for the global Phase 1/2 clinical trial of PM577a in WD, initial clinical data in 2027. Submission of an IND and/or CTA for PM647 in AATD in the third quarter of 2026, initial clinical data in 2027. Continued regulatory engagement with the FDA toward a BLA submission for PM359 in the first half of 2027. Second Quarter 2026 Financial Results Research and Development (R&D) Expenses: R&D expenses were $33.4 million for the three months ended June 30, 2026, as compared to $41.4 million for the three months ended June 30, 2025. The decrease in R&D expenses was driven primarily by fewer R&D personnel-related costs resulting from the workforce reduction announced in May 2025, and facility cost savings realized from bringing the Company’s vivarium in-house. General and Administrative (G&A) Expenses: G&A expenses were $11.0 million for the three months ended June 30, 2026, as compared to $13.1 million for the three months ended June 30, 2025. The decrease in G&A expenses was primarily driven by a decrease in personnel costs resulting from one-time severance charges recorded in Q2 2025 and a decrease in stock compensation expense, and lower corporate legal fees. Net Loss: Net loss was $42.1 million for the three months ended June 30, 2026, as compared to $52.6 million for the three months ended June 30, 2025. Cash Position: As of June 30, 2026, cash, cash equivalents, investments, and restricted cash were $108.8 million, as compared to $191.4 million as of December 31, 2025. Financial Guidance Based on its current operating plans, Prime Medicine expects that its cash, cash equivalents and investments as of June 30, 2026 will be sufficient to fund its operating expenses and capital expenditure requirements into 2027. About Prime Medicine 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 our core areas of focus: liver, lung, and immunology and oncology. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, its X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2026 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 continued development and advancement of its WD, AATD and CF programs, including the anticipated timing of filing an IND and/or CTA application for PM647 in 3Q of 2026, the initiation of the global Phase 1/2 clinical trial of PM577a in the second half of 2026, and initial clinical data for PM647 and PM577a in 2027; the potential of Prime Editing to correct the causative mutations of, and to cure, diseases, including WD, AATD, CF and CGD; the ongoing regulatory engagement with the FDA based on the data from its Phase 1/2 trial of PM359 and the outcomes of such engagement, including the planned submission of a BLA filing in H1 2027; the potential benefits of RMAT designation for PM359, including discussions that may support expedited approval and eligibility for rolling and priority review of a future BLA; the effect of the resolution of the arbitration with Beam Therapeutics, Inc. on the Company’s rights to develop and commercialize PM647; the modularity of the Prime Editing platform and the benefits thereof; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory DearbornPrime [email protected] Hannah DeresiewiczPrecision [email protected]

Wall Street expects a year-over-year increase in earnings on higher revenues when Prime Medicine, Inc. (PRME) reports results for the quarter ended June 2026. While this widely-known consensus outlook is important in gauging the company's earnings picture, a powerful factor that could impact its near-term stock price is how the actual results compare to these estimates. The earnings report might help the stock move higher if these key numbers are better than expectations. On the other hand, if they miss, the stock may move lower. While the sustainability of the immediate price change and future earnings expectations will mostly depend on management's discussion of business conditions on the earnings call, it's worth handicapping the probability of a positive EPS surprise. This company is expected to post quarterly loss of $0.24 per share in its upcoming report, which represents a year-over-year change of +41.5%. Revenues are expected to be $4.4 million, up 292.9% from the year-ago quarter. The consensus EPS estimate for the quarter has remained unchanged over the last 30 days. This is essentially a reflection of how the covering analysts have collectively reassessed their initial estimates over this period. Investors should keep in mind that an aggregate change may not always reflect the direction of estimate revisions by each of the covering analysts. Price, Consensus and EPS Surprise Estimate revisions ahead of a company's earnings release offer clues to the business conditions for the period whose results are coming out. Our proprietary surprise prediction model -- the Zacks Earnings ESP (Expected Surprise Prediction) -- has this insight at its core. The Zacks Earnings ESP compares the Most Accurate Estimate to the Zacks Consensus Estimate for the quarter; the Most Accurate Estimate is a more recent version of the Zacks Consensus EPS estimate. The idea here is that analysts revising their estimates right before an earnings release have the latest information, which could potentially be more accurate than what they and others contributing to the consensus had predicted earlier. Thus, a positive or negative Earnings ESP reading theoretically indicates the likely deviation of the actual earnings from the consensus estimate. However, the model's predictive power is significant for positive ESP readings only. A positive Earnings ESP is a strong predictor of an earnings beat, particularly when combined with a Zacks Rank #1 (Strong Buy), 2 (Buy) or 3 (Hold). Our research shows that stocks with this combination produce a positive surprise nearly 70% of the time, and a solid Zacks Rank actually increases the predictive power of Earnings ESP. Please note that a negative Earnings ESP reading is not indicative of an earnings miss. Our research shows that it is difficult to predict an earnings beat with any degree of confidence for stocks with negative Earnings ESP readings and/or Zacks Rank of 4 (Sell) or 5 (Strong Sell). For Prime Medicine, Inc., the Most Accurate Estimate is lower than the Zacks Consensus Estimate, suggesting that analysts have recently become bearish on the company's earnings prospects. This has resulted in an Earnings ESP of -15.86%. On the other hand, the stock currently carries a Zacks Rank of #2. So, this combination makes it difficult to conclusively predict that Prime Medicine, Inc. will beat the consensus EPS estimate. While calculating estimates for a company's future earnings, analysts often consider to what extent it has been able to match past consensus estimates. So, it's worth taking a look at the surprise history for gauging its influence on the upcoming number. For the last reported quarter, it was expected that Prime Medicine, Inc. would post a loss of$0.24 per share when it actually produced a loss of -$0.28, delivering a surprise of -16.67%. Over the last four quarters, the company has beaten consensus EPS estimates just once. An earnings beat or miss may not be the sole basis for a stock moving higher or lower. Many stocks end up losing ground despite an earnings beat due to other factors that disappoint investors. Similarly, unforeseen catalysts help a number of stocks gain despite an earnings miss. That said, betting on stocks that are expected to beat earnings expectations does increase the odds of success. This is why it's worth checking a company's Earnings ESP and Zacks Rank ahead of its quarterly release. Make sure to utilize our Earnings ESP Filter to uncover the best stocks to buy or sell before they've reported. Prime Medicine, Inc. doesn't appear a compelling earnings-beat candidate. However, investors should pay attention to other factors too for betting on this stock or staying away from it ahead of its earnings release. Gossamer Bio (GOSS), another stock in the Zacks Medical - Biomedical and Genetics industry, is expected to report loss per share of $0.1 for the quarter ended June 2026. This estimate points to a year-over-year change of +41.2%. Revenues for the quarter are expected to be $3.4 million, down 70.4% from the year-ago quarter. The consensus EPS estimate for Gossamer Bio has remained unchanged over the last 30 days. However, a lower Most Accurate Estimate has resulted in an Earnings ESP of -40.00%. This Earnings ESP, combined with its Zacks Rank #3 (Hold), makes it difficult to conclusively predict that Gossamer Bio will beat the consensus EPS estimate. Over the last four quarters, the company surpassed EPS estimates just once. Stay on top of upcoming earnings announcements with the Zacks Earnings Calendar. Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Prime Medicine, Inc. (PRME) : Free Stock Analysis Report Gossamer Bio, Inc. (GOSS) : Free Stock Analysis Report This article originally published on Zacks Investment Research (zacks.com). Zacks Investment Research

CAMBRIDGE, Mass., May 07, 2026 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the quarter ended March 31, 2026 and provided a business update. “Prime Medicine continues to execute with clear momentum and a focused strategy designed to deliver on the transformative potential of Prime Editing,” said Allan Reine, M.D., Chief Executive Officer of Prime Medicine. “We remain on track to file regulatory applications for PM577 in Wilson Disease in the first half of this year, and for PM647 in AATD mid-year, bringing two of our most advanced programs to the brink of clinical entry, with initial data from both expected in 2027. In parallel, we continue to progress toward a potential BLA filing for PM359, which, if successful, would bring a one-time, potentially curative therapy to people living with CGD, who today face a lifetime of debilitating infections and limited treatment options. With a strengthened leadership team and a continued commitment to disciplined capital allocation, we believe Prime Medicine is well positioned to execute across our pipeline and unlock the broad promise of Prime Editing for patients.” Prime Medicine’s Pipeline: Prime Medicine is currently advancing in vivo programs to cure two of the largest genetic liver diseases, Wilson Disease (WD) and Alpha-1 Antitrypsin Deficiency (AATD). Prime Medicine expects to file an Investigational New Drug application (IND) and/or Clinical Trial Application (CTA) for PM577 in WD in the first half of 2026 and for PM647 in AATD in mid-2026; initial clinical data from both programs are expected in 2027. Prime Medicine is also advancing an in vivo Cystic Fibrosis (CF) program with support from the Cystic Fibrosis Foundation, and efforts to develop Prime Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. Additionally, following positive proof-of-concept data from the first two patients treated in its Phase 1/2 study of PM359 for the treatment of Chronic Granulomatous Disease (CGD), Prime Medicine continues to engage in regulatory dialogue with the U.S. Food and Drug Administration (FDA) toward a potential Biologics License Application (BLA) filing for PM359. Recent Corporate Updates: In April 2026, Prime Medicine announced the appointment of Svetlana Makhni as Chief Financial Officer (CFO). Ms. Makhni brings over 20 years of experience across biotechnology and healthcare CFO and investment banking roles, and will oversee Prime Medicine’s financial operations and strategy, including investor relations, and financial planning and analysis. Upcoming Presentation: Today, Prime Medicine announced that it will present new preclinical data for its Wilson Disease program at the American Society of Gene & Cell Therapy (ASGCT) 2026 Annual Meeting (May 11-15 in Boston, MA). Details of the oral presentation are as follows: Session: Translational Gene Therapy and Editing in Storage Disorders Presentation ID: 78 Presentation Title: Prime Editing Enables Precise and Efficient Correction of ATP7B Mutations and Restoration of Copper Homeostasis in Wilson Disease Models Presentation Date and Time: May 12th, 2026 at 11:30AM EST First Quarter 2026 Financial Results Research and Development (R&D) Expenses: R&D expenses were $34.1 million for the three months ended March 31, 2026, as compared to $40.6 million for the three months ended March 31, 2025. The decrease in R&D expenses was driven primarily by Prime Medicine’s strategic focus on advancing its in vivo liver franchise, deprioritization of its CGD program, and a reduction in R&D personnel resulting from the workforce reduction. This decrease was partially offset by an increase in clinical expense as Prime Medicine advances its WD and AATD programs. General and Administrative (G&A) Expenses: G&A expenses were $17.4 million for the three months ended March 31, 2026, as compared to $13.3 million for the three months ended March 31, 2025. The increase in G&A expenses was primarily driven by arbitration-related legal expenses, offset by a decrease in personnel costs resulting from the workforce reduction announced in May 2025. Net Loss: Net loss was $49.1 million for the three months ended March 31, 2026, as compared to $51.9 million for the three months ended March 31, 2025. Cash Position: As of March 31, 2026, cash, cash equivalents, investments, and restricted cash were $149.2 million, as compared to $191.4 million as of December 31, 2025. Financial Guidance Based on its current operating plans, Prime Medicine expects that its cash, cash equivalents and investments as of March 31, 2026 will be sufficient to fund its operating expenses and capital expenditure requirements into 2027. About Prime Medicine 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 our core areas of focus: liver, lung, and immunology and oncology. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, its X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2026 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 significance of data from its Phase 1/2 trial of PM359; the ongoing regulatory interactions with the FDA based on the data from its Phase 1/2 trial of PM359 and the outcomes of any such interactions, including its plan to submit a BLA for PM359 following final alignment with the FDA; the continued development and advancement of its WD, AATD and CF programs, including the anticipated timing of filing an IND and/or CTA application for its WD program in the first half of 2026 and for its AATD program in mid-2026, and initial clinical data for both programs in 2027; the potential of PM359 to address the unmet medical need for patients with CGD; the potential of Prime Editing to correct the causative mutations of, and to cure, diseases, including WD, AATD, CF and CGD; the partnership with Bristol Myers Squibb and the Cystic Fibrosis Foundation and the intended and potential benefits thereof; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; the modularity of the Prime Editing platform and the benefits thereof; the potential impacts of Ms. Makhni’s appointment as CFO of the Company; the potential of Prime Editing to unlock opportunities across thousands of potential indications; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory Dearborn Prime Medicine 857-209-0696 [email protected] Hannah Deresiewicz Precision AQ 212-362-1200 [email protected]

Harmony Biosciences Holdings, Inc. (HRMY) came out with quarterly earnings of $0.55 per share, missing the Zacks Consensus Estimate of $0.76 per share. This compares to earnings of $0.78 per share a year ago. These figures are adjusted for non-recurring items. This quarterly report represents an earnings surprise of -27.94%. A quarter ago, it was expected that this company would post earnings of $0.84 per share when it actually produced earnings of $0.38, delivering a surprise of -54.76%. Over the last four quarters, the company has not been able to surpass consensus EPS estimates. Harmony Biosciences, which belongs to the Zacks Medical - Biomedical and Genetics industry, posted revenues of $215.39 million for the quarter ended March 2026, missing the Zacks Consensus Estimate by 3.18%. This compares to year-ago revenues of $184.73 million. The company has topped consensus revenue estimates two times over the last four quarters. The sustainability of the stock's immediate price movement based on the recently-released numbers and future earnings expectations will mostly depend on management's commentary on the earnings call. Harmony Biosciences shares have lost about 12.4% since the beginning of the year versus the S&P 500's gain of 7.6%. While Harmony Biosciences has underperformed the market so far this year, the question that comes to investors' minds is: what's next for the stock? There are no easy answers to this key question, but one reliable measure that can help investors address this is the company's earnings outlook. Not only does this include current consensus earnings expectations for the coming quarter(s), but also how these expectations have changed lately. Empirical research shows a strong correlation between near-term stock movements and trends in earnings estimate revisions. Investors can track such revisions by themselves or rely on a tried-and-tested rating tool like the Zacks Rank, which has an impressive track record of harnessing the power of earnings estimate revisions. Ahead of this earnings release, the estimate revisions trend for Harmony Biosciences was mixed. While the magnitude and direction of estimate revisions could change following the company's just-released earnings report, the current status translates into a Zacks Rank #3 (Hold) for the stock. So, the shares are expected to perform in line with the market in the near future. You can see the complete list of today's Zacks #1 Rank (Strong Buy) stocks here. It will be interesting to see how estimates for the coming quarters and the current fiscal year change in the days ahead. The current consensus EPS estimate is $0.93 on $249.23 million in revenues for the coming quarter and $3.34 on $1.03 billion in revenues for the current fiscal year. Investors should be mindful of the fact that the outlook for the industry can have a material impact on the performance of the stock as well. In terms of the Zacks Industry Rank, Medical - Biomedical and Genetics is currently in the bottom 40% of the 250 plus Zacks industries. Our research shows that the top 50% of the Zacks-ranked industries outperform the bottom 50% by a factor of more than 2 to 1. Prime Medicine, Inc. (PRME), another stock in the same industry, has yet to report results for the quarter ended March 2026. This company is expected to post quarterly loss of $0.24 per share in its upcoming report, which represents a year-over-year change of +40%. The consensus EPS estimate for the quarter has been revised 0.6% higher over the last 30 days to the current level. Prime Medicine, Inc.'s revenues are expected to be $1.56 million, up 7.6% from the year-ago quarter. Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Harmony Biosciences Holdings, Inc. (HRMY) : Free Stock Analysis Report Prime Medicine, Inc. (PRME) : Free Stock Analysis Report This article originally published on Zacks Investment Research (zacks.com). Zacks Investment Research

RenovoRx, Inc. (RNXT) is expected to deliver flat earnings compared to the year-ago quarter on higher revenues when it reports results for the quarter ended March 2026. This widely-known consensus outlook gives a good sense of the company's earnings picture, but how the actual results compare to these estimates is a powerful factor that could impact its near-term stock price. The earnings report, which is expected to be released on May 14, might help the stock move higher if these key numbers are better than expectations. On the other hand, if they miss, the stock may move lower. While the sustainability of the immediate price change and future earnings expectations will mostly depend on management's discussion of business conditions on the earnings call, it's worth handicapping the probability of a positive EPS surprise. This company is expected to post quarterly loss of $0.08 per share in its upcoming report, which represents no change from the year-ago quarter. Revenues are expected to be $0.5 million, up 150% from the year-ago quarter. The consensus EPS estimate for the quarter has been revised 6.67% lower over the last 30 days to the current level. This is essentially a reflection of how the covering analysts have collectively reassessed their initial estimates over this period. Investors should keep in mind that the direction of estimate revisions by each of the covering analysts may not always get reflected in the aggregate change. Price, Consensus and EPS Surprise Estimate revisions ahead of a company's earnings release offer clues to the business conditions for the period whose results are coming out. Our proprietary surprise prediction model -- the Zacks Earnings ESP (Expected Surprise Prediction) -- has this insight at its core. The Zacks Earnings ESP compares the Most Accurate Estimate to the Zacks Consensus Estimate for the quarter; the Most Accurate Estimate is a more recent version of the Zacks Consensus EPS estimate. The idea here is that analysts revising their estimates right before an earnings release have the latest information, which could potentially be more accurate than what they and others contributing to the consensus had predicted earlier. Thus, a positive or negative Earnings ESP reading theoretically indicates the likely deviation of the actual earnings from the consensus estimate. However, the model's predictive power is significant for positive ESP readings only. A positive Earnings ESP is a strong predictor of an earnings beat, particularly when combined with a Zacks Rank #1 (Strong Buy), 2 (Buy) or 3 (Hold). Our research shows that stocks with this combination produce a positive surprise nearly 70% of the time, and a solid Zacks Rank actually increases the predictive power of Earnings ESP. Please note that a negative Earnings ESP reading is not indicative of an earnings miss. Our research shows that it is difficult to predict an earnings beat with any degree of confidence for stocks with negative Earnings ESP readings and/or Zacks Rank of 4 (Sell) or 5 (Strong Sell). For RenovoRx, the Most Accurate Estimate is the same as the Zacks Consensus Estimate, suggesting that there are no recent analyst views which differ from what have been considered to derive the consensus estimate. This has resulted in an Earnings ESP of 0%. On the other hand, the stock currently carries a Zacks Rank of #3. So, this combination makes it difficult to conclusively predict that RenovoRx will beat the consensus EPS estimate. Analysts often consider to what extent a company has been able to match consensus estimates in the past while calculating their estimates for its future earnings. So, it's worth taking a look at the surprise history for gauging its influence on the upcoming number. For the last reported quarter, it was expected that RenovoRx would post a loss of$0.08 per share when it actually produced a loss of -$0.08, delivering no surprise. The company has not been able to beat consensus EPS estimates in any of the last four quarters. An earnings beat or miss may not be the sole basis for a stock moving higher or lower. Many stocks end up losing ground despite an earnings beat due to other factors that disappoint investors. Similarly, unforeseen catalysts help a number of stocks gain despite an earnings miss. That said, betting on stocks that are expected to beat earnings expectations does increase the odds of success. This is why it's worth checking a company's Earnings ESP and Zacks Rank ahead of its quarterly release. Make sure to utilize our Earnings ESP Filter to uncover the best stocks to buy or sell before they've reported. RenovoRx doesn't appear a compelling earnings-beat candidate. However, investors should pay attention to other factors too for betting on this stock or staying away from it ahead of its earnings release. Another stock from the Zacks Medical - Biomedical and Genetics industry, Prime Medicine, Inc. (PRME), is soon expected to post loss of $0.24 per share for the quarter ended March 2026. This estimate indicates a year-over-year change of +40%. Revenues for the quarter are expected to be $1.56 million, up 7.6% from the year-ago quarter. Over the last 30 days, the consensus EPS estimate for Prime Medicine, Inc. has been revised 0.6% up to the current level. Nevertheless, the company now has an Earnings ESP of +4.73%, reflecting a higher Most Accurate Estimate. When combined with a Zacks Rank of #2 (Buy), this Earnings ESP indicates that Prime Medicine, Inc. will most likely beat the consensus EPS estimate. Over the last four quarters, the company surpassed EPS estimates just once. Stay on top of upcoming earnings announcements with the Zacks Earnings Calendar. Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report RenovoRx, Inc. (RNXT) : Free Stock Analysis Report Prime Medicine, Inc. (PRME) : Free Stock Analysis Report This article originally published on Zacks Investment Research (zacks.com). Zacks Investment Research

-- On track to file IND and/or CTA for Wilson Disease and AATD programs in 1H 2026 and mid-2026, respectively; initial clinical data for both expected in 2027 -- -- Ongoing engagement with FDA for PM359 in CGD; plan to submit BLA following final alignment -- -- Prime Medicine reported cash, cash equivalents, investments, and restricted cash of $191M providing cash runway into 2027 -- CAMBRIDGE, Mass., March 03, 2026 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the full year ended December 31, 2025 and provided a business update. “We are shaping the future of genetic medicine by advancing a platform that is rapidly emerging as the predominant gene editing technology. With Prime Editing, we have the opportunity to permanently and safely correct disease-causing mutations across a broad range of indications, supported by our comprehensive IP estate,” said Allan Reine, M.D., Chief Executive Officer of Prime Medicine. “With this foundation, our vision is bold and unwavering: to strategically deliver on the promise of Prime Editing and ensure patients have access to transformative therapies capable of delivering durable, and potentially lasting cures. This begins with PM359, our ex vivo Prime Edited autologous HSC product for CGD, for which we announced breakthrough data in 2025, which we believe supports an accelerated approval in the United States.” Dr. Reine continued, “We are also intensely focused on R&D execution. We are progressing toward key regulatory milestones for our two liver‑focused programs – in Wilson Disease and Alpha-1 Antitrypsin Deficiency – including planned IND and CTA submissions and the initiation of Phase 1/2 clinical trials. In parallel, we continue to generate compelling preclinical data across our portfolio, including for our program for Cystic Fibrosis; to further optimize our modular delivery and manufacturing approaches; and to explore additional collaborations that could expand the reach of our platform. These near‑ and mid‑term milestones position us to deliver important additional clinical validation of Prime Editing, as we accelerate our path toward bringing meaningful, life‑changing therapies to patients.” Prime Medicine’s Pipeline: Prime Medicine is advancing in vivo gene editing programs aimed at treating two of the most significant genetic liver disorders: Wilson Disease (WD) and Alpha‑1 Antitrypsin Deficiency (AATD). Prime Medicine anticipates submitting an investigational new drug (IND) and/or clinical trial application (CTA) for its anchor WD program (targeting the H1069Q mutation) in the first half of 2026, and plans to leverage the modularity of the Prime Editing platform to subsequently advance follow-on programs targeting other mutations, which collectively address a majority of WD patients. Prime Medicine expects to file an IND and/or CTA for its AATD program in mid-2026, and to report initial clinical data from both WD and AATD programs in 2027. Following positive proof-of-concept data from the first two patients treated in its Phase 1/2 study of PM359 for the treatment of Chronic Granulomatous Disease (CGD), Prime Medicine is actively working to ensure this transformative therapy is available for patients in need. Prime Medicine is also progressing an in vivo Cystic Fibrosis (CF) program with support from the Cystic Fibrosis Foundation, and anticipates generating preclinical proof of concept data in 2026. Additionally, its efforts to develop Prime Edited CAR-T products for hematology, immunology and oncology continue in partnership with Bristol Myers Squibb. Recent Business Updates: Prime Medicine continues to engage with the U.S. Food and Drug Administration (FDA) to explore ways to make PM359 available to patients with CGD. Based on recent interactions, Prime Medicine believes clinical data generated to-date may be sufficient to support an accelerated approval of PM359. The Company is working towards final alignment with the FDA, and intends to submit a Biologics License Application (BLA). In December 2025, Prime Medicine announced the publication of Phase 1/2 clinical data with PM359 in the New England Journal of Medicine (NEJM). The data, which were also presented in a poster session at the 67th American Society of Hematology (ASH) Annual Meeting, showed rapid neutrophil and platelet engraftment, as well as durable restoration of NADPH oxidase activity and early clinical benefit, without any safety concerns. Full Year 2025 Financial Results Research and Development (R&D) Expenses: R&D expenses were $160.6 million for the year ended December 31, 2025, as compared to $155.3 million for the year ended December 31, 2024. The increase in R&D expenses is driven primarily by license and intellectual property costs and facility related expenses, offset by Prime Medicine’s strategic focus on advancing its in vivo liver franchise, deprioritization of its CGD program, and a reduction in R&D personnel resulting from the workforce reduction. General and Administrative (G&A) Expenses: G&A expenses were $52.3 million for the year ended December 31, 2025, as compared to $50.2 million for the year ended December 31, 2024. The increase in G&A expenses was driven by increases in professional and consultant fees. Net Loss: Net loss was $201.1 million for the year ended December 31, 2025, as compared to $195.9 million for the year ended December 31, 2024. Cash Position: As of December 31, 2025, cash, cash equivalents, investments, and restricted cash were $191.4 million, as compared to $204.5 million as of December 31, 2024. Financial Guidance Based on its current operating plans, Prime Medicine expects that its cash, cash equivalents and investments as of December 31, 2025 will be sufficient to fund its operating expenses and capital expenditure requirements into 2027. About Prime Medicine 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 its core areas of focus: hematology, immunology and oncology, liver and lung. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, our X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2026 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 continued development and advancement of PM359, including the significance of data from its Phase 1/2 trial of PM359; the planned regulatory interactions with the FDA based on the data from its Phase 1/2 trial of PM359 and the outcomes of any such interactions; the continued development and advancement of its CF, AATD and WD programs, including the anticipated timing of filing an IND and/or CTA application for its WD program in the first half of 2026 and for its AATD program in mid-2026, and initial clinical data for both programs in 2027; the potential of PM359 to address the unmet medical need for patients with CGD; the potential of Prime Editing to correct the causative mutations of, and to cure, diseases, including AATD, WD, CF and CGD; the potential for its modular universal LNP platform to precisely deliver Prime Editors and enable significant efficiencies in pre-clinical development, manufacturing and clinical development; the ability to demonstrate, and the timing of, preclinical proof-of-concept in vivo for multiple programs; the further advancement of Prime Editors to maximize their versatility, precision and efficiency; the collaboration with Bristol Myers Squibb and the Cystic Fibrosis Foundation and the intended and potential benefits thereof; the initiation, timing, progress, and results of its research and development programs, preclinical studies and future clinical trials, including the release of data related thereto; the modularity of the Prime Editing platform and the benefits thereof; the potential for Prime Editors to more precisely and effectively achieve genetic modification; the potential for Prime Editors to repair genetic mutations and offer curative genetic therapies for a wide spectrum of diseases; the expansion of Prime Editing’s therapeutic potential and the creation of value through strategic business development to extend the reach and impact of Prime Editing to areas beyond Prime Medicine’s current pipeline; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; the potential of Prime Editing to unlock opportunities across thousands of potential indications; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory Dearborn Prime Medicine 857-209-0696 [email protected] Hannah Deresiewicz Precision AQ 212-362-1200 [email protected]

-- New preclinical data for PM577 in Wilson’s Disease (WD) to be presented at AASLD; on-track to file IND and/or CTA in H1’26, with initial clinical data expected in 2027 -- -- Nominated PM647 as development candidate for Alpha-1 Antitrypsin Deficiency (AATD); on-track to file IND and/or CTA in mid-2026, with initial clinical data expected in 2027 -- -- Strengthened leadership team with the appointment of Matthew Hawryluk, Ph.D., M.B.A. as Chief Business Officer -- -- Company to host virtual KOL event at 8:00am ET on Wednesday, November 12, 2025 to showcase Wilson’s Disease Strategy -- CAMBRIDGE, Mass., Nov. 07, 2025 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the quarter ended September 30, 2025 and provided a business update. “We remain steadfast in executing our focused strategy, with efforts centered on advancing our liver-targeted programs in WD and AATD, our Cystic Fibrosis (CF) program as well as exploring additional collaborations – like our efforts with Bristol Myers Squibb – that can expand the reach and impact of our technology,” said Allan Reine, M.D., Chief Executive Officer of Prime Medicine. “In recent months, we’ve made meaningful progress across these priorities. In August, we nominated PM647 as our development candidate for AATD, marking a significant step toward delivering a best-in-class therapy capable of correcting the mutant AATD protein back to normal. And, earlier this week, we welcomed Matthew Hawryluk, Ph.D., M.B.A., as Chief Business Officer, adding a senior leader with deep experience in building companies through internal innovation and high-value strategic collaborations. Following our recent financing, we believe we are well positioned to continue executing across our pipeline and to leverage the versatility and broad reach of our platform to treat some of the most devastating genetic diseases.” Dr. Reine continued, “This progress continues as we enter the fourth quarter. This weekend, we’ll present new preclinical data with PM577 at AASLD, further reinforcing our belief that Prime Editing can precisely correct the disease-causing mutations in patients suffering from Wilson’s Disease.” Prime Medicine’s Pipeline: Prime Medicine is currently advancing in vivo programs to cure two of the largest genetic liver diseases, Wilson’s Disease (WD) and Alpha-1 Antitrypsin Deficiency (AATD). Prime Medicine expects to file an investigational new drug application (IND) and/or clinical trial application (CTA) for its WD program in the first half of 2027 and for its AATD program in mid-2026; initial clinical data from both studies are expected in 2027. Prime Medicine is also advancing an in vivo Cystic Fibrosis (CF) program with support from the Cystic Fibrosis Foundation, and efforts to develop Prime Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. Additionally, following positive proof-of-concept data from the first two patients treated in its Phase 1/2 study of PM359 for the treatment of Chronic Granulomatous Disease (CGD), Prime Medicine plans to continue to engage in regulatory interactions with the U.S. Food and Drug Administration (FDA) to explore efficient ways to make this medicine available to patients in need. Recent Business Updates Today, Prime Medicine announced that it will present new preclinical data for PM577 at the American Association for the Study of Liver Diseases (AASLD) Liver Meeting (November 7-11, 2025). Details of the late-breaking poster presentation are as follows: Title: Normalization of hepatic copper level detected by ⁶⁴Cu PET imaging in mice treated with Prime Editor that precisely corrected ATP7B p.H1069Q mutation causing Wilson disease Date: Sunday, November 9, 2025 Time: 8:00am – 5:00pm ET Presentation Number: 5032 Session: Sunday Late Breaking Posters In August 2025, Prime Medicine nominated PM647 as its development candidate for the treatment of AATD. In fully humanized mouse models, treatment with PM647 achieved high levels of editing efficiency and demonstrated restoration of the corrected isoform (M-AAT) into the healthy human range at clinically relevant doses. PM647 is delivered using Prime Medicine’s universal liver lipid nanoparticle (LNP), which the Company believes may enable significant efficiencies in pre-clinical development, manufacturing and clinical development. Recent Corporate Updates: In November 2025, Prime Medicine announced the appointment of Matthew Hawryluk, Ph.D., M.B.A. as Chief Business Officer. Dr. Hawryluk will lead Prime Medicine’s business development, corporate strategy and alliance management functions, advancing the company’s efforts to expand the reach of Prime Editing through partnerships and collaborations. Prime Medicine will host a virtual KOL event on Wednesday, November 12, 2025, from 8:00-9:00am ET. This event will provide insight into Prime Medicine’s Wilson’s Disease strategy, with a focus on PM577. In addition to company management, the event will feature Dr. Michael Schilsky, Professor of Medicine at Yale School of Medicine and Medical Director of the Adult Liver Transplant program at Yale New Haven Transplantation Center. The event will be webcast live and those who intend to join can pre-register for the webcast here. Third Quarter 2025 Financial Results Research and Development (R&D) Expenses: R&D expenses were $44.0 million for the three months ended September 30, 2025, as compared to $40.3 million for the three months ended September 30, 2024. The increase in R&D expenses is driven primarily by license and intellectual property costs and facility related expenses, offset by Prime Medicine’s strategic focus on advancing its in vivo liver franchise, deprioritization of its CGD program, and a reduction in R&D personnel resulting from the workforce reduction. General and Administrative (G&A) Expenses: G&A expenses were $11.2 million for the three months ended September 30, 2025, as compared to $14.1 million for the three months ended September 30, 2024. The decrease in G&A expenses is primarily driven by a decrease in personnel costs resulting from the workforce reduction. Net Loss: Net loss was $50.6 million for the three months ended September 30, 2025, as compared to $52.5 million for the three months ended September 30, 2024. Cash Position: As of September 30, 2025, cash, cash equivalents, investments, and restricted cash were $227.0 million, as compared to $204.5 million as of December 31, 2024. Financial Guidance Based on its current operating plans, Prime Medicine expects that its cash, cash equivalents and investments of $213.3 million as of September 30, 2025 will be sufficient to fund its operating expenses and capital expenditure requirements into 2027. About Prime Medicine 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 our core areas of focus: liver, lung, and immunology and oncology. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, its X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2025 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 significance of data from its Phase 1/2 trial of PM359; the planned regulatory interactions with the FDA based on the data from its Phase 1/2 trial of PM359 and the outcomes of any such interactions; the continued development and advancement of its CF, AATD and WD programs, including the anticipated timing of filing an IND and/or CTA application for its WD program in the first half of 2027 and for its AATD program in mid-2026, and initial clinical data for both programs in 2027; the potential of PM359 to address the unmet medical need for patients with CGD; the initiation, timing, progress, and results of its research and development programs, preclinical studies and future clinical trials, including the release of data related thereto; the potential of Prime Editing to correct the causative mutations of, and to cure, diseases, including AATD, WD, CF and CGD; the potential for its universal LNP platform to precisely deliver Prime Editors and enable significant efficiencies in pre-clinical development, manufacturing and clinical development; the partnership with Bristol Myers Squibb and the Cystic Fibrosis Foundation, the intended and potential benefits thereof, and its ability to enter into additional partnerships; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; the potential of Prime Editing to unlock opportunities across thousands of potential indications; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory Dearborn Prime Medicine 857-209-0696 [email protected] Hannah Deresiewicz Precision AQ 212-362-1200 [email protected]

-- New preclinical data for PM577 in Wilson’s Disease (WD) to be presented at AASLD; on-track to file IND and/or CTA in H1’26, with initial clinical data expected in 2027 -- -- Nominated PM647 as development candidate for Alpha-1 Antitrypsin Deficiency (AATD); on-track to file IND and/or CTA in mid-2026, with initial clinical data expected in 2027 -- -- Strengthened leadership team with the appointment of Matthew Hawryluk, Ph.D., M.B.A. as Chief Business Officer -- -- Company to host virtual KOL event at 8:00am ET on Wednesday, November 12, 2025 to showcase Wilson’s Disease Strategy -- CAMBRIDGE, Mass., Nov. 07, 2025 (GLOBE NEWSWIRE) -- In a release issued earlier today by Prime Medicine, Inc. (Nasdaq: PRME) under the same headline, please note the first paragraph under "Prime Medicine’s Pipeline" has been amended to include "Prime Medicine expects to file an investigational new drug application (IND) and/or clinical trial application (CTA) for its WD program in the first half of 2026" rather than the "first half of 2027" as originally issued. Corrected release follows. Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the quarter ended September 30, 2025 and provided a business update. “We remain steadfast in executing our focused strategy, with efforts centered on advancing our liver-targeted programs in WD and AATD, our Cystic Fibrosis (CF) program as well as exploring additional collaborations – like our efforts with Bristol Myers Squibb – that can expand the reach and impact of our technology,” said Allan Reine, M.D., Chief Executive Officer of Prime Medicine. “In recent months, we’ve made meaningful progress across these priorities. In August, we nominated PM647 as our development candidate for AATD, marking a significant step toward delivering a best-in-class therapy capable of correcting the mutant AATD protein back to normal. And, earlier this week, we welcomed Matthew Hawryluk, Ph.D., M.B.A., as Chief Business Officer, adding a senior leader with deep experience in building companies through internal innovation and high-value strategic collaborations. Following our recent financing, we believe we are well positioned to continue executing across our pipeline and to leverage the versatility and broad reach of our platform to treat some of the most devastating genetic diseases.” Dr. Reine continued, “This progress continues as we enter the fourth quarter. This weekend, we’ll present new preclinical data with PM577 at AASLD, further reinforcing our belief that Prime Editing can precisely correct the disease-causing mutations in patients suffering from Wilson’s Disease.” Prime Medicine’s Pipeline: Prime Medicine is currently advancing in vivo programs to cure two of the largest genetic liver diseases, Wilson’s Disease (WD) and Alpha-1 Antitrypsin Deficiency (AATD). Prime Medicine expects to file an investigational new drug application (IND) and/or clinical trial application (CTA) for its WD program in the first half of 2026 and for its AATD program in mid-2026; initial clinical data from both studies are expected in 2027. Prime Medicine is also advancing an in vivo Cystic Fibrosis (CF) program with support from the Cystic Fibrosis Foundation, and efforts to develop Prime Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. Additionally, following positive proof-of-concept data from the first two patients treated in its Phase 1/2 study of PM359 for the treatment of Chronic Granulomatous Disease (CGD), Prime Medicine plans to continue to engage in regulatory interactions with the U.S. Food and Drug Administration (FDA) to explore efficient ways to make this medicine available to patients in need. Recent Business Updates Today, Prime Medicine announced that it will present new preclinical data for PM577 at the American Association for the Study of Liver Diseases (AASLD) Liver Meeting (November 7-11, 2025). Details of the late-breaking poster presentation are as follows: Title: Normalization of hepatic copper level detected by ⁶⁴Cu PET imaging in mice treated with Prime Editor that precisely corrected ATP7B p.H1069Q mutation causing Wilson disease Date: Sunday, November 9, 2025 Time: 8:00am – 5:00pm ET Presentation Number: 5032 Session: Sunday Late Breaking Posters In August 2025, Prime Medicine nominated PM647 as its development candidate for the treatment of AATD. In fully humanized mouse models, treatment with PM647 achieved high levels of editing efficiency and demonstrated restoration of the corrected isoform (M-AAT) into the healthy human range at clinically relevant doses. PM647 is delivered using Prime Medicine’s universal liver lipid nanoparticle (LNP), which the Company believes may enable significant efficiencies in pre-clinical development, manufacturing and clinical development. Recent Corporate Updates: In November 2025, Prime Medicine announced the appointment of Matthew Hawryluk, Ph.D., M.B.A. as Chief Business Officer. Dr. Hawryluk will lead Prime Medicine’s business development, corporate strategy and alliance management functions, advancing the company’s efforts to expand the reach of Prime Editing through partnerships and collaborations. Prime Medicine will host a virtual KOL event on Wednesday, November 12, 2025, from 8:00-9:00am ET. This event will provide insight into Prime Medicine’s Wilson’s Disease strategy, with a focus on PM577. In addition to company management, the event will feature Dr. Michael Schilsky, Professor of Medicine at Yale School of Medicine and Medical Director of the Adult Liver Transplant program at Yale New Haven Transplantation Center. The event will be webcast live and those who intend to join can pre-register for the webcast here. Third Quarter 2025 Financial Results Research and Development (R&D) Expenses: R&D expenses were $44.0 million for the three months ended September 30, 2025, as compared to $40.3 million for the three months ended September 30, 2024. The increase in R&D expenses is driven primarily by license and intellectual property costs and facility related expenses, offset by Prime Medicine’s strategic focus on advancing its in vivo liver franchise, deprioritization of its CGD program, and a reduction in R&D personnel resulting from the workforce reduction. General and Administrative (G&A) Expenses: G&A expenses were $11.2 million for the three months ended September 30, 2025, as compared to $14.1 million for the three months ended September 30, 2024. The decrease in G&A expenses is primarily driven by a decrease in personnel costs resulting from the workforce reduction. Net Loss: Net loss was $50.6 million for the three months ended September 30, 2025, as compared to $52.5 million for the three months ended September 30, 2024. Cash Position: As of September 30, 2025, cash, cash equivalents, investments, and restricted cash were $227.0 million, as compared to $204.5 million as of December 31, 2024. Financial Guidance Based on its current operating plans, Prime Medicine expects that its cash, cash equivalents and investments of $213.3 million as of September 30, 2025 will be sufficient to fund its operating expenses and capital expenditure requirements into 2027. About Prime Medicine 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 our core areas of focus: liver, lung, and immunology and oncology. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, its X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2025 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 significance of data from its Phase 1/2 trial of PM359; the planned regulatory interactions with the FDA based on the data from its Phase 1/2 trial of PM359 and the outcomes of any such interactions; the continued development and advancement of its CF, AATD and WD programs, including the anticipated timing of filing an IND and/or CTA application for its WD program in the first half of 2027 and for its AATD program in mid-2026, and initial clinical data for both programs in 2027; the potential of PM359 to address the unmet medical need for patients with CGD; the initiation, timing, progress, and results of its research and development programs, preclinical studies and future clinical trials, including the release of data related thereto; the potential of Prime Editing to correct the causative mutations of, and to cure, diseases, including AATD, WD, CF and CGD; the potential for its universal LNP platform to precisely deliver Prime Editors and enable significant efficiencies in pre-clinical development, manufacturing and clinical development; the partnership with Bristol Myers Squibb and the Cystic Fibrosis Foundation, the intended and potential benefits thereof, and its ability to enter into additional partnerships; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; the potential of Prime Editing to unlock opportunities across thousands of potential indications; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory Dearborn Prime Medicine 857-209-0696 [email protected] Hannah Deresiewicz Precision AQ 212-362-1200 [email protected]

-- Announced positive data from two patients in Phase 1/2 clinical trial in Chronic Granulomatous Disease (CGD), providing clinical proof-of-concept for Prime Editing; plan to have regulatory interactions based on current dataset -- -- Completed follow-on offering, raising $144.2 million in gross proceeds and extending cash runway into 2027 -- -- Secured up to $24 million in additional funding from the Cystic Fibrosis Foundation to advance Prime Editors for Cystic Fibrosis -- -- Announced leadership transition and strategic restructuring: Allan Reine, M.D., named Chief Executive Officer; focusing efforts on advancing liver franchise and programs funded through external partnerships -- CAMBRIDGE, Mass., Aug. 07, 2025 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the quarter ended June 30, 2025 and provided a business update. “Recent months have been transformative for Prime Medicine. We announced initial data from our CGD program, providing the first clinical evidence that Prime Editing may cure genetic diseases in humans, and outlined a strategic restructuring, reinforcing our commitment to operating with efficiency and financial discipline as we deliver the tremendous power of our technology,” said Allan Reine, M.D., Chief Executive Officer of Prime Medicine. “We enter the second half of 2025 in a position of strength, laser-focused on advancing our internally-funded programs to treat Wilson’s Disease and Alpha-1 Antitrypsin Deficiency, two of the largest genetic diseases treated by targeting the liver – as well as on programs to treat Cystic Fibrosis and with our partner BMS Prime Edited CAR-T products for hematology, immunology and oncology. Importantly, we are highly encouraged by the clinical data from the first two subjects from our CGD program and we intend to engage the FDA based on our current dataset to explore efficient ways to make this medicine available to patients in need.” Dr. Reine continued, “In recent weeks, we announced the successful closing of a $144.2 million financing and the receipt of additional funding from the Cystic Fibrosis Foundation. Together, these reflect a widespread belief in the transformative power of Prime Editing, as well as conviction in our focused strategy from a range of industry stakeholders. We are grateful to our new and existing shareholders for their continued support of our efforts to deliver the tremendous promise of Prime Editing to change patients’ lives.” Prime Medicine’s Pipeline: Prime Medicine is currently advancing in vivo programs to cure two of the largest genetic liver diseases, Wilson’s Disease and Alpha-1 Antitrypsin Deficiency (AATD), with initial clinical data from both programs expected in 2027. Prime Medicine is also advancing an in vivo Cystic Fibrosis (CF) program with support from the Cystic Fibrosis Foundation, and efforts to develop Prime Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. Recent Business Updates Prime Medicine announced additional clinical data from its Phase 1/2 study of PM359 for the treatment of Chronic Granulomatous Disease (CGD). Consistent with data previously reported in May 2025, preliminary results from a second patient showed rapid engraftment and restored NADPH oxidase activity to well above the threshold for clinical benefit, as measured by the dihydrorhodamine (DHR) assay, with an encouraging safety profile. In addition, data in the second patient demonstrated an improvement in inflammatory markers of CGD, with fecal calprotectin – a measure of intestinal inflammation – returning to normal levels at Day 45 from 15 times the upper limit of normal at baseline. While Prime Medicine does not intend to independently advance clinical development of PM359, the Company plans to have regulatory interactions with the U.S. Food and Drug Administration (FDA). In July 2025, Prime Medicine announced that the Cystic Fibrosis Foundation agreed to provide the Company with up to $24 million in additional funding to accelerate the development of Prime Editors designed to cure CF. With this capital from the Cystic Fibrosis Foundation, Prime Medicine will initially focus its efforts on the G542X mutation, one of the most prevalent nonsense mutations associated with CF and one for which currently available therapies are ineffective, while continuing to advance its PASSIGE-based approach. Recent Corporate Updates: In August 2025, Prime Medicine closed an underwritten public offering of common stock. Gross proceeds to Prime Medicine from the offering, before deducting underwriting discounts and commissions and offering expenses, were $144.2 million. In May 2025, Prime Medicine announced the appointment of Allan Reine, M.D., as Chief Executive Officer and member of the Board of Directors, and Jeff Marrazzo, member of the Company’s Board of Directors, as Executive Chair. Also in May 2025, Prime Medicine announced a strategic restructuring, as well as a cost and workforce reduction. These initiatives were designed to significantly decrease Prime Medicine’s operating expenses and cash burn, reducing anticipated cash needs by almost half through 2027. Second Quarter 2025 Financial Results Research and Development (R&D) Expenses: R&D expenses were $41.4 million for the three months ended June 30, 2025, as compared to $43.1 million for the three months ended June 30, 2024. The decrease in R&D expenses is driven primarily by Prime Medicine’s strategic focus on advancing its in vivo liver franchise, deprioritization of its CGD program, and a reduction in R&D personnel resulting from the workforce reduction. General and Administrative (G&A) Expenses: G&A expenses were $13.1 million for the three months ended June 30, 2025, as compared to $12.6 million for the three months ended June 30, 2024. The increase in G&A expenses primarily consists of one-time severance payments and other employee termination-related expenses and an increase in Prime Medicine’s corporate legal expenses. Net Loss: Net loss was $52.6 million for the three months ended June 30, 2025, as compared to $55.3 million for the three months ended June 30, 2024. Cash Position: As of June 30, 2025, cash, cash equivalents, investments, and restricted cash were $115.4 million, as compared to $204.5 million as of December 31, 2024. Cash as of June 30, 2025 does not include gross proceeds of $144.2 million from the company’s follow-on underwritten public offering of common stock, which closed in August 2025. Financial Guidance Based on its current operating plans, Prime Medicine expects that its pro-forma cash, cash equivalents and investments of $259.6 million as of June 30, 2025, which includes cash, cash equivalents, investments and restricted cash of $115.4 million as of June 30, 2025, and $138.2 million in net proceeds from its follow-on public offering and $6.0 million received from the Cystic Fibrosis Foundation in the third quarter, will be sufficient to fund its operating expenses and capital expenditure requirements into 2027. About Prime Medicine 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 our core areas of focus: liver, lung, and immunology and oncology. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, its X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2025 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 significance of data from its Phase 1/2 trial of PM359 on other pipeline programs and Prime Editing; the planned regulatory interactions with the FDA based on the data from its Phase 1/2 trial of PM359 and the outcomes of any such interactions; its evaluation of strategic alternatives and potential partnership opportunities for PM359, including its ability to execute and realize the anticipated benefits of any strategic alternatives it may pursue; the agreement with the CF Foundation, its expanded funding pursuant thereto, and the intended and potential benefits thereof, including the receipt of payments based on scientific milestones; the continued advancement of PASSIGE-based approaches for correcting CF mutations other than G542X; the continued development and advancement of its AATD and Wilson’s Disease programs, including the timing of initial clinical data for both programs in 2027; the initiation, timing, progress, and results of its research and development programs, preclinical studies and future clinical trials, including the release of data related thereto; the potential of Prime Editing to correct the causative mutations of, and to cure, diseases, including AATD, Wilson’s Disease, CF and CGD; its expectations regarding the anticipated benefits of its May 2025 strategic restructuring and reduction in force and its ability to implement and achieve the expected cost savings in connection therewith; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; the potential of Prime Editing to unlock opportunities across thousands of potential indications; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory Dearborn Prime Medicine 857-209-0696 [email protected] Hannah Deresiewicz Precision AQ 212-362-1200 [email protected]

-- Initial data from Phase 1/2 trial of PM359 for p47phox CGD expected in 2025 -- -- IND and/or CTA for PM577 for Wilson’s Disease on-track for 1H 2026 -- -- Unveiled potentially best-in-class program for AATD; IND and/or CTA filing targeted for mid-2026 -- CAMBRIDGE, Mass., May 08, 2025 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today reported financial results for the quarter ended March 31, 2025 and provided a business update. “We recently unveiled our AATD program, further demonstrating our commitment to building a liver franchise of Prime Editors designed to cure major genetic diseases,” said Keith Gottesdiener, M.D., President and Chief Executive Officer of Prime Medicine. “Both our Wilson’s Disease and AATD programs are advancing through preclinical development, and we look forward to initiating clinical trials in both indications in 2026. In addition, we remain on track to report initial data from our Phase 1/2 trial of PM359 in CGD this year, and continue to progress our efforts in CF.” Dr. Gottesdiener continued, “While PM359 leverages a different delivery mechanism from our programs in liver and lung diseases, we believe our forthcoming CGD data could provide important readthrough across our pipeline. If positive, these data would demonstrate the potential of Prime Editing as a powerful and differentiated technology, potentially capable of offering curative benefit to patients following a single treatment. We remain committed to executing with focus and discipline as we approach these first in-human data, which we hope will mark a key inflection point on our path to sustained growth.” Prime Medicine’s Pipeline: Prime Medicine is advancing a set of high-value programs across its core areas of focus (hematology, immunology and oncology, liver, and lung). These include ex vivo hematopoietic stem cell (HSC) programs for the treatment of p47phox chronic granulomatous disease (CGD) and X-linked CGD; lipid nanoparticle (LNP) Prime Editors for the treatment of Wilson’s Disease and alpha-1 antitrypsin deficiency (AATD); LNP or adeno-associated virus (AAV) Prime Editors for the treatment of cystic fibrosis (CF); and ex vivo T-cell therapies, which are being developed in collaboration with Bristol Myers Squibb. Recent Business Updates In March 2025, Prime Medicine unveiled its preclinical program for the treatment of AATD. Prime Medicine’s program leverages the Company’s universal liver LNP to edit the E342K (Pi*Z) mutation in the SERPINA1 gene, the prevalent disease-causing mutation in AATD, with the potential to treat both lung- and liver-associated disease. In initial in vivo data, Prime Medicine observed high levels of editing at the target site, with full restoration of circulating wild-type AAT protein (M-AAT) to normal human range. Additionally, based on preclinical studies using unoptimized surrogate Prime Editors across Prime Medicine’s liver franchise, the Company believes Prime Editing has the ability to correct disease-causing mutations without introducing off-target or bystander edits. Anticipated Upcoming Milestones: Chronic Granulomatous Disease (CGD): Announce initial clinical data from Cohort 1 in the Phase 1/2 trial of PM359 for p47phox CGD in 2025. The initial readout will include safety and engraftment data, as well as key outcome measures, including the reconstitution of NADPH oxidase activity as measured by the DHR assay. Wilson’s Disease: Advance PM577 through investigational new drug (IND)-enabling studies for the treatment of Wilson’s Disease patients with the most prevalent Wilson’s Disease mutation in the United States. File investigational new drug (IND) and/or clinical trial application (CTA) for PM577 in the first half of 2026. AATD: Initiate IND-enabling studies for the treatment of AATD. File IND and/or CTA in mid-2026. First Quarter 2025 Financial Results Research and Development (R&D) Expenses: R&D expenses were $40.6 million for the three months ended March 31, 2025, as compared to $37.8 million for the three months ended March 31, 2024. The increase in R&D expenses primarily due to the expansion and build out of our laboratory space at 60 First Street and 500 Arsenal Street. General and Administrative (G&A) Expenses: G&A expenses were $13.3 million for the three months ended March 31, 2025, as compared to $11.2 million for the three months ended March 31, 2024. The increase in G&A expenses was driven by personnel expenses. Net Loss: Net loss was $51.9 million for the three months ended March 31, 2025, as compared to $45.8 million for the three months ended March 31, 2024. Cash Position: As of March 31, 2025, cash, cash equivalents, investments, and restricted cash were $158.3 million, as compared to $204.5 million as of December 31, 2024. Financial Guidance Based on its current operating plans, Prime Medicine expects that its cash, cash equivalents and investments as of March 31, 2025 will be sufficient to fund its operating expenses and capital expenditure requirements into the first half of 2026. About Prime Medicine 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 our core areas of focus: hematology, immunology and oncology, liver and lung. Across each core area, Prime Medicine is focused initially on a set of high value programs, each targeting a disease with well-understood biology and a clearly defined clinical development and regulatory path, and each expected to provide the foundation for expansion into additional opportunities. Over time, the Company intends to maximize Prime Editing’s broad and versatile therapeutic potential, as well as the modularity of the Prime Editing platform, to rapidly and efficiently expand beyond the diseases in its current pipeline, potentially including additional genetic diseases, 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. From time to time Prime Medicine may use its website, its X, formerly Twitter, account (@PrimeMedicine) or its LinkedIn profile at https://www.linkedin.com/company/prime-medicine to distribute material information. Its financial and other material information is routinely posted to and accessible on the Investors section of its website, available at www.primemedicine.com. Investors are encouraged to review the Investors section of its website because the Company may post material information on that site that is not otherwise disseminated by the Company. Information that is contained in and can be accessed through the Company’s website or its social media is not incorporated into, and does not form a part of, this press release. © 2025 Prime Medicine, Inc. All rights reserved. PRIME MEDICINE, the Prime Medicine logos, and PASSIGE are trademarks of Prime Medicine, Inc. All other trademarks referred to herein are the property of their respective owners. Forward Looking Statements 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 continued development and advancement of PM359, including the ongoing Phase 1/2 trial and the timing of the anticipated release of initial clinical data readout for p47phox CGD in 2025; the continued development and advancement of its AATD and Wilson’s Disease programs, including the timing of the filing of IND and/or CTA applications in mid-2026 and 1H 2026, respectively; the initiation, timing, progress, and results of its research and development programs, preclinical studies and future clinical trials, including the release of data related thereto; the significance of data from the Phase 1/2 trial of PM359 on other pipeline programs and Prime Editing; the potential of Prime Editing to correct the causative mutations of diseases, including of AATD, Wilson’s Disease, CF and p47phox CGD; its expectations regarding the breadth of Prime Editing technology and the implementation of its strategic plans for its business, programs, and technology; the potential of Prime Editing to unlock opportunities across thousands of potential indications; and its expected cash runway. 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 Prime Medicine’s product candidates 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; Prime Medicine’s expectations regarding the anticipated timeline of its cash runway and future financial performance; and general economic, industry and market conditions. 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. Investor and Media Contacts Gregory Dearborn Prime Medicine 857-209-0696 [email protected] Hannah Deresiewicz Precision AQ 212-362-1200 [email protected]