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- Data from longer-term follow-up of patients in clinical trials further demonstrate durability of the transformative benefits of CASGEVY® - - Multiple reimbursement agreements secured, expanding access to CASGEVY to more patients around the world - LONDON - June 12, 2025 - Vertex Pharmaceuticals (Nasdaq: VRTX) today announced positive longer-term data for CASGEVY® (exagamglogene autotemcel) from global clinical trials in people with severe sickle cell disease (SCD) or transfusion-dependent beta thalassemia (TDT). The results, presented at the European Hematology Association (EHA) Congress, continue to demonstrate the transformative, durable clinical benefits of CASGEVY. The longest follow up in SCD patients now extends more than 5.5 years and in TDT patients more than 6 years, with a mean of 39.4 months and 43.5 months, respectively. CASGEVY is the first and only approved CRISPR/Cas9 gene-edited therapy. “These longer-term data further confirm that CASGEVY can provide significant and durable clinical benefits to eligible people living with sickle cell disease or transfusion-dependent beta thalassemia,” said Franco Locatelli, M.D., Ph.D., Professor of Pediatrics at the Catholic University of the Sacred Heart of Rome, Director of the Department of Pediatric Hematology and Oncology at Bambino Gesù Children’s Hospital, Chair of Vertex’s TDT Program Steering Committee, and Presenting Author of the CASGEVY TDT clinical data at EHA. “Given the urgent and unmet need for new transformative treatments for these diseases, I am delighted by the strong progress that has been made to bring CASGEVY to eligible patients in the real world.” New longer-term follow-up data presented from the CASGEVY trials In SCD, 43/45 (95.6%) evaluable patients (those with at least 16 months of follow-up) were free from vaso-occlusive crises (VOCs) for at least 12 consecutive months (VF12) in CLIMB-121 and CLIMB-131 combined (95% CI: 84.9%, 99.5%). The mean duration of VOC-free was 35.0 months (range 14.4 to 66.2 months). All evaluable patients (45/45 [100%]) achieved freedom from in-patient hospitalization for severe VOCs for at least 12 consecutive months (HF12) in CLIMB-121 and CLIMB-131 combined (95% CI: 92.1%, 100%), with a mean hospitalization-free of 36.1 months (range 14.5 to 66.2 months). In TDT, 54/55 (98.2%) evaluable patients (those with at least 16 months of follow-up) achieved transfusion-independence for at least 12 consecutive months with a weighted average hemoglobin (Hb) of at least 9 g/dL (TI12) in CLIMB-111 and CLIMB-131 combined (95% CI: 90.3%, 100%). The mean duration of transfusion independence was 40.5 months (range 13.6 to 70.8 months). The one evaluable patient who did not achieve TI12 has been transfusion free for 14.8 months. Iron removal therapy has been stopped for more than 6 months in 39/56 (69.6%) treated patients following infusion with CASGEVY, with sustained improvement in ferritin and liver iron content, suggesting that CASGEVY has the potential to correct ineffective erythropoiesis. Patients continue to demonstrate stable levels of fetal hemoglobin (HbF) and allelic editing. The safety profile of CASGEVY continues to be generally consistent with myeloablative conditioning with busulfan and autologous hematopoietic stem cell transplant. All evaluable patients (45/45 [100%]) achieved freedom from in-patient hospitalization for severe VOCs for at least 12 consecutive months (HF12) in CLIMB-121 and CLIMB-131 combined (95% CI: 92.1%, 100%), with a mean hospitalization-free of 36.1 months (range 14.5 to 66.2 months). The one evaluable patient who did not achieve TI12 has been transfusion free for 14.8 months. Iron removal therapy has been stopped for more than 6 months in 39/56 (69.6%) treated patients following infusion with CASGEVY, with sustained improvement in ferritin and liver iron content, suggesting that CASGEVY has the potential to correct ineffective erythropoiesis. Progress in bringing CASGEVY to patients Through reimbursement agreements, Vertex has secured access for eligible SCD or TDT patients in multiple countries including Austria, Bahrain, England, the Kingdom of Saudi Arabia, Northern Ireland, Scotland, the United Arab Emirates, the United States and Wales. Vertex is continuing to work with government and reimbursement authorities globally to secure sustainable access for additional eligible patients. About Sickle Cell Disease (SCD) SCD is a debilitating, progressive, life-shortening genetic disease. SCD patients report health-related quality of life scores well below the general population and significant health care resource utilization. SCD affects the red blood cells, which are essential for carrying oxygen to all organs and tissues of the body. SCD causes severe pain, organ damage and shortened life span due to misshapen or “sickled” red blood cells. The clinical hallmark of SCD is vaso-occlusive crises (VOCs), which are caused by blockages of blood vessels by sickled red blood cells and result in severe and debilitating pain that can happen anywhere in the body at any time. SCD requires lifelong treatment and significant use of health care resources, and ultimately results in reduced life expectancy, decreased quality of life and reduced lifetime earnings and productivity. In Europe, the mean age of death for patients living with SCD is around 40 years. About Transfusion-Dependent Beta Thalassemia (TDT) TDT is a serious, life-threatening genetic disease. TDT patients report health-related quality of life scores below the general population and significant health care resource utilization. TDT requires frequent blood transfusions and iron chelation therapy throughout a person’s life. Due to anemia, patients living with TDT may experience fatigue and shortness of breath, and infants may develop failure to thrive, jaundice and feeding problems. Complications of TDT can also include an enlarged spleen, liver and/or heart, misshapen bones and delayed puberty. TDT requires lifelong treatment and significant use of health care resources, and ultimately results in reduced life expectancy, decreased quality of life and reduced lifetime earnings and productivity. In Europe, the mean age of death for patients living with TDT is 50-55 years. About CASGEVY® (exagamglogene autotemcel) CASGEVY® is a non-viral, ex vivo CRISPR/Cas9 gene-edited cell therapy for eligible patients with SCD or TDT, in which a patient’s own hematopoietic stem and progenitor cells are edited at the erythroid specific enhancer region of the BCL11A gene through a precise double-strand break. This edit results in the production of high levels of fetal hemoglobin (HbF; hemoglobin F) in red blood cells. HbF is the form of the oxygen-carrying hemoglobin that is naturally present during fetal development, which then switches to the adult form of hemoglobin after birth. CASGEVY has been shown to reduce or eliminate VOCs for patients with SCD and transfusion requirements for patients with TDT. CASGEVY is approved for eligible SCD and TDT patients 12 years and older by multiple regulatory bodies around the world. About the CLIMB Trials The ongoing Phase 1/2/3 open-label trials, CLIMB-111 and CLIMB-121, are designed to assess the safety and efficacy of a single dose of CASGEVY in patients ages 12 to 35 years with TDT or with SCD and recurrent VOCs. The trials are closed for enrollment. Patients will be followed for approximately two years after CASGEVY infusion in these trials. Each patient will be asked to participate in the ongoing long-term, open-label trial, CLIMB-131. CLIMB-131 is designed to evaluate the long-term safety and efficacy of CASGEVY in patients who received CASGEVY, including those in other CLIMB trials. The trial is designed to follow patients for up to 15 years after CASGEVY infusion. About Vertex Vertex is a global biotechnology company that invests in scientific innovation to create transformative medicines for people with serious diseases and conditions. The company has approved therapies for cystic fibrosis, sickle cell disease, transfusion-dependent beta thalassemia and acute pain, and it continues to advance clinical and research programs in these areas. Vertex also has a robust clinical pipeline of investigational therapies across a range of modalities in other serious diseases where it has deep insight into causal human biology, including neuropathic pain, APOL1-mediated kidney disease, IgA nephropathy, primary membranous nephropathy, autosomal dominant polycystic kidney disease, type 1 diabetes and myotonic dystrophy type 1. Vertex was founded in 1989 and has its global headquarters in Boston, with international headquarters in London. Additionally, the company has research and development sites and commercial offices in North America, Europe, Australia, Latin America and the Middle East. Vertex is consistently recognized as one of the industry's top places to work, including 15 consecutive years on Science magazine's Top Employers list and one of Fortune’s 100 Best Companies to Work For. For company updates and to learn more about Vertex’s history of innovation, visit www.vrtx.com/en-global. Vertex Special Note Regarding Forward-Looking Statements This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, the statements by Franco Locatelli, M.D., Ph.D., in this press release, and statements regarding expectations for the anticipated transformative, durable clinical benefits of CASGEVY, plans to continue working with government and reimbursement authorities globally to secure sustainable access for patients, and our plans for and design of the CLIMB studies. While we believe the forward-looking statements contained in this press release are accurate, these forward-looking statements represent the company's beliefs only as of the date of this press release and there are a number of risks and uncertainties that could cause actual events or results to differ materially from those expressed or implied by such forward-looking statements. Those risks and uncertainties include, among other things, that eligible patient access to CASGEVY may not be achieved on the anticipated timeline, or at all, that data from the company's development programs may not support registration or further development of its compounds due to safety, efficacy, and other reasons, and other risks listed under the heading “Risk Factors” in Vertex's most recent annual report and subsequent quarterly reports filed with the Securities and Exchange Commission at www.sec.gov and available through the company's website at www.vrtx.com. You should not place undue reliance on these statements, or the scientific data presented. Vertex disclaims any obligation to update the information contained in this press release as new information becomes available. Vertex Pharmaceuticals IncorporatedInvestors:InvestorInfo@vrtx.com Media:mediainfo@vrtx.comorInternational: +44 20 3204 5275orU.S.: 617-341-6992

-- First ever clinical data supporting safety and efficacy of Prime Editing in humans -- -- Initial data from first patient dosed in Phase 1/2 trial finds single dose of PM359 led to 58% DHR positivity by Day 15 and 66% by Day 30, well above levels believed to be potentially curative -- -- Rapid engraftment observed in both neutrophils and platelets -- -- Encouraging safety profile; no serious adverse events related to PM359 -- -- Initiating efforts to explore continued clinical development opportunities for PM359 external to Prime Medicine -- May 19, 2025 -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today announced positive initial data from the first patient dosed in its ongoing Phase 1/2 clinical study of PM359 in Chronic Granulomatous Disease (CGD). Preliminary results from the first patient demonstrated that PM359 was well-tolerated, showed rapid engraftment and restored NADPH oxidase activity to well above the threshold for clinical benefit, as measured by the dihydrorhodamine (DHR) assay. CGD is a rare inherited disease that leads to recurrent, debilitating and often life-threatening infections. It is caused by mutations in genes, including NCF1, that encode proteins that form the NADPH oxidase complex, an enzyme that kills bacteria and fungi to control infection. PM359, an ex vivo Prime Edited autologous hematopoietic stem cell (HSC) product for the treatment of p47phox CGD and the first Prime Editor generated therapy to be administered in humans, is designed to correct the delGT mutation in NCF1, the most prevalent disease-causing mutation in the p47phox variant of CGD, thereby addressing its underlying pathophysiology. Prime Medicine estimates that CGD causative mutations occur in between one in 100,000 and one in 200,000 births in the United States, with approximately 25 percent of patients presenting with the p47phox form of the disease. “We created prime editing five and a half years ago as a versatile, precise genome editing technology that in principle could correct almost all mutations known to cause genetic diseases,” said David Liu, Ph.D., Co-Founder of Prime Medicine and Richard Merkin Professor and Director of the Merkin Institute of Transformative Technologies in Healthcare at the Broad Institute of MIT and Harvard. “Today’s data represent a milestone in medicine, establishing that prime editing in a patient's cells can correct a pathogenic mutation and can change the course of a life-limiting disease. I am thrilled by the implication of these results for the CGD patient community, and more generally for people living with genetic diseases.” PM359 is being evaluated in a Phase 1/2, multinational, first-in-human trial designed to assess safety, biological activity and preliminary efficacy in adult and pediatric study participants. Initial safety and efficacy data reported today are from the first adult patient treated in the trial. This patient was treated with a single dose of PM359, administered by intravenous infusion. NADPH oxidase activity was measured by the dihydrorhodamine (DHR) assay at baseline, Day 15 and Day 30. Treatment with PM359 led to complete restoration of NADPH oxidase activity in 58% of neutrophils by Day 15 and 66% of neutrophils by Day 30, significantly exceeding the anticipated minimum threshold for clinical benefit of 20%. Additionally, this patient experienced rapid engraftment of his autologous transplant following myeloablative conditioning. Engraftment was confirmed in neutrophils on Day 14 and in platelets on Day 19. Of note, this is nearly two-times faster than approved gene editing technologies, where median engraftment has been reported to occur on Days 27 and 35 across these same measures. Treatment with PM359 was generally well-tolerated, with an acceptable safety profile. Adverse events (AEs) were generally consistent with AEs otherwise observed during myeloablative conditioning with busulfan. No serious AEs related to PM359 were reported as of the data cutoff. “The data reported today are important for two reasons. First, for people living with CGD, these results suggest Prime Editing may offer a reprieve from their disease, restoring NADPH oxidase function and, therefore, reducing the risk of acquiring a deadly infection or suffering from inflammation of the lung, liver or bowel,” said Mohammed Asmal, M.D., Ph.D., Chief Medical Officer of Prime Medicine. “We are grateful to our first patient and to his family and caretakers for their trust and participation in our trial.” Dr. Asmal continued, “Second, these data answer key questions about Prime Editors, confirming their potential to be delivered safely and restore normal gene function. This reaffirms our conviction that Prime Editing will be the foundation of a new class of differentiated, one-time genetic therapies, and we look forward to advancing our broader pipeline of investigational programs, directed towards large genetic diseases that impact the liver and lung.” Prime Medicine does not plan to independently advance its efforts in CGD. Prime Medicine is exploring options for the continued clinical development of PM359 external to the company and ceasing further efforts in X-linked CGD. Prime Medicine believes PM359 has the potential to transform the care of p47phox CGD and is committed to working with urgency to identify an appropriate partner to help ensure this important therapy is delivered to patients. Going forward, Prime Medicine will focus its resources on advancing its in vivo liver franchise, where the Company is advancing programs to cure two of the largest genetic liver diseases, Wilson’s Disease and Alpha-1 Antitrypsin Deficiency (AATD). Prime Medicine will also continue its in vivo Cystic Fibrosis program with support from the Cystic Fibrosis Foundation, and its efforts to develop Prime Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. In addition, Prime Medicine will continue to pursue additional business development opportunities to accelerate innovation, ensure the broadest application of Prime Editing, and further bolster its financial resources. PM359, Prime Medicine’s first product candidate within its hematology and immunology area of focus, targets the p47phox variant of CGD, a serious, life-threatening disease that presents in childhood. PM359 comprises autologous hematopoietic stem cells (HSCs) modified ex vivo using Prime Editors that have been designed to correct a high percentage of cells containing the disease-causing mutation. PM359 has received rare pediatric drug designation and orphan drug designation from the U.S. Food and Drug Administration. Chronic granulomatous disease (CGD) is a rare inherited hematologic disorder characterized by susceptibility to severe, difficult-to-treat infections, and inflammatory/autoimmune complications. CGD is caused by mutations in any one of the subunits comprising the NADPH oxidase complex, which is required for phagocytic cells, in particular neutrophils, to destroy many invasive microorganisms. CGD causative mutations are estimated to occur between one in 100,000 and one in 200,000 births in the United States, and most children are diagnosed within the first three years of life. Beginning in childhood, patients with CGD develop infections from a range of both typical and unusual bacteria, fungi and mycobacteria. These infections may present in various organ systems, and protracted infections can lead to long-term organ damage and failure. In addition, patients have non-infectious inflammatory disease, most commonly presenting as inflammatory bowel disease, soft tissue granulomas, and strictures of the urinary or digestive tract. Undiagnosed or untreated, the infectious manifestations of CGD are rapidly fatal, with refractory or antimicrobial resistant infection the leading cause of mortality. 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. 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