The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our condensed consolidated financial statements and related notes appearing elsewhere in this Quarterly Report on Form 10-Q, or this Quarterly Report, and our audited consolidated financial statements and related notes for the year ended December 31, 2025, included in our Annual Report on Form 10-K filed with the Securities and Exchange Commission, or SEC, on March 2, 2026. Some of the information contained in this discussion and analysis or set forth elsewhere in this Quarterly Report, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in the “Risk Factors” section of this Quarterly Report, our actual results could differ materially from the results described in, or implied by, the forward-looking statements contained in the following discussion and analysis. Overview We are a clinical-stage company focused on delivering functional improvement for people living with genetically driven neuromuscular diseases. Our proprietary FORCE platform is designed to leverage the transferrin receptor 1, or TfR1, to deliver targeted therapeutics to muscle tissue and the central nervous system, or CNS. The FORCE platform utilizes an antigen-binding fragment antibody, or Fab, targeting TfR1 linked to a payload that we rationally design to target the genetic basis of the disease we are seeking to treat. With our FORCE platform, we have the flexibility to deploy different classes of payloads (such as oligonucleotides and enzymes) with specific mechanisms of action that modify target functions. We currently leverage this modularity to focus on neuromuscular diseases with high unmet need, with etiologic targets and with clear translational potential from preclinical disease models to well-defined clinical development and regulatory pathways. Using our FORCE platform, we are assembling a broad portfolio of product candidates, including product candidates being developed for Duchenne muscular dystrophy, or DMD, myotonic dystrophy type 1, or DM1, facioscapulohumeral dystrophy, or FSHD, and Pompe disease. In addition, we plan to expand our portfolio through development efforts focused on diseases involving the CNS, rare skeletal muscle diseases, and cardiac and metabolic muscle diseases, including some with larger patient populations. We have identified product candidates for each of our DMD, DM1, FSHD and Pompe programs that are in varying stages of preclinical and clinical development. DMD We are developing zeleciment rostudirsen, or z-rostudirsen (also known as DYNE-251), for the treatment of DMD amenable to exon 51 skipping. Z-rostudirsen is designed to enable the production of near full-length dystrophin in muscle and the CNS to provide functional improvement. Z-rostudirsen has received Breakthrough Therapy, Fast Track and Rare Pediatric Disease designations from the U.S. Food and Drug Administration, or FDA, as well as Orphan Drug designation 18 from the FDA, the European Medicines Agency and the Japanese Ministry of Health, Labour and Welfare for the treatment of individuals with DMD, amenable to exon 51 skipping. Additionally, we are advancing four development candidates (DYNE-253, DYNE-245, DYNE-244 and DYNE-255) for the treatment of DMD amenable to skipping of exons 53, 45, 44, 55, respectively, into IND-enabling studies. Z-rostudirsen is being evaluated in the long-term extension portion of the DELIVER trial, a global Phase 1/2 clinical trial designed to be registrational, and the FORZETTO trial, a global Phase 3 clinical trial designed to be confirmatory. We have aligned with the FDA on the FORZETTO trial design and protocol. The registrational expansion cohort of the global Phase 1/2 DELIVER clinical trial of z-rostudirsen met its primary endpoint. Data from the DELIVER trial served as the basis for a biologics license application, or BLA, for potential U.S. Accelerated Approval. In May 2026, we initiated our Phase 3 FORZETTO clinical trial, a global, randomized, placebo-controlled, double-blind, confirmatory Phase 3 trial designed to assess the efficacy, safety, and tolerability of z-rostudirsen administered intravenously to ambulatory male participants with DMD amenable to exon 51 skipping. The trial will enroll approximately 90 participants 4 to 18 years of age who will be randomized 1:1 to receive 20 mg/kg of z-rostudirsen or placebo every four weeks (Q4W). The primary endpoint is the change from baseline in rise from floor (RFF) velocity at Week 73. Secondary endpoints include changes from baseline in stride velocity 95th centile (SV95C), North Star Ambulatory Assessment (NSAA) total score, 10-meter walk/run (10MWR) velocity, four-stair climb (4SC) velocity and forced vital capacity percent predicted (FVC%p), as well as additional functional and patient-reported outcome measures. Following the 72-week double-blind placebo-controlled treatment period, participants will be eligible to enroll in a 96-week open-label long-term extension. We have aligned with the FDA on the FORZETTO Phase 3 trial design and protocol. FORZETTO is intended to serve as a confirmatory trial to support the potential conversion of Accelerated Approval to traditional approval in the United States and to support ex-U.S. marketing applications. In July 2026, we announced that the FDA accepted for review our BLA for z-rostudirsen for the treatment of individuals with DMD amenable to exon 51 skipping. The FDA has granted the BLA priority review and assigned a Prescription Drug User Fee Act, or PDUFA, target action date of January 21, 2027. We continue to expect a potential U.S. launch of z-rostudirsen in the first quarter of 2027, assuming FDA approval is received on the anticipated timeline. We continue to pursue approval pathways outside of the United States for z-rostudirsen. DM1 We are developing zeleciment basivarsen, or z-basivarsen (also known as DYNE-101), for the treatment of DM1. Z-basivarsen is designed to deliver functional improvement in individuals living with DM1 by reducing toxic nuclear DMPK RNA to release splicing proteins and allow normal mRNA processing. Z-basivarsen has been granted Breakthrough Therapy, Orphan Drug and Fast Track designations by the FDA and Orphan Drug designation by the European Medicines Agency and the Japanese Ministry of Health, Labour and Welfare for the treatment of DM1. Z-basivarsen is being evaluated in the ACHIEVE trial, a global Phase 1/2 clinical trial designed to be registrational, and the HARMONIA trial, a global Phase 3 clinical trial designed to be confirmatory. We have aligned with the FDA on the HARMONIA trial design and protocol. In March 2026, we initiated our Phase 3 HARMONIA clinical trial, a global, randomized, placebo controlled, double-blind, confirmatory Phase 3 trial designed to assess the multi-system efficacy, safety, and tolerability of z-basivarsen administered intravenously to individuals with DM1. We began dosing patients in July 2026. The trial will enroll approximately 150 participants age 16 and older who will be randomized 1:1 to receive 6.8 mg/kg of z-basivarsen or placebo every eight weeks (Q8W). The primary endpoint is the change from baseline in the five times sit to stand (5xSTS) test at week 49. Secondary endpoints include video hand opening time, quantitative muscle testing, the 10-Meter Walk/Run test, the Myotonic Dystrophy Health Index, and additional patient- and clinician-reported outcomes. The trial also includes a broad set of exploratory endpoints designed to assess multiple domains of DM1 CNS impact. Following the 48-week double-blind placebo-controlled treatment period, patients will be eligible to enroll in a 24-week long-term extension. In June 2026, we completed enrollment of 71 participants in the registrational expansion cohort, or REC, of the ACHIEVE trial. We plan to announce data from the REC in the first quarter of 2027 to support a potential BLA submission to the FDA for U.S. Accelerated Approval in the third quarter of 2027. We anticipate a potential U.S. launch of z-basivarsen in the first half of 2028, assuming we receive favorable data from the REC, priority review is granted, and FDA approval is received on the anticipated timeline. We continue to pursue approval pathways outside of the United States for z-basivarsen. 19 FSHD We are developing DYNE-302 for the treatment of FSHD. DYNE-302 is designed to deliver functional improvement in individuals living with FSHD by reducing aberrant DUX4 expression. We are progressing DYNE-302 toward clinical development. In June 2024 and June 2025, we announced preclinical data for DYNE-302, our product candidate for FSHD, that demonstrated robust and durable DUX4 suppression and functional benefit in a mouse model. We generated these data using an innovative hTfR1/iFLExD mouse model we developed that expresses TfR1 and enables tunable DUX4 induction in skeletal muscle. In hTfR1/iFLExD mice, a single intravenous dose of DYNE-302 resulted in dose-dependent and robust reduction of the DUX4 transcriptome that lasted up to three months, with benefit on muscle structure. DYNE-302 also demonstrated prevention and reversal of muscle weakness. In July 2026, we announced that we received clearance from the FDA for our investigational new drug, or IND, application to initiate a Phase 1 clinical trial for DYNE-302 in FSHD. DYNE-302 leverages the same FORCE platform as our first two clinical programs, z-rostudirsen in DMD amenable to exon 51 skipping and z-basivarsen in DM1. We plan to evaluate DYNE-302 in a Phase 1 randomized, placebo-controlled, double-blind, multiple ascending dose clinical trial in ambulatory adult individuals with FSHD with a primary endpoint of safety and tolerability. The trial will also assess pharmacokinetics and pharmacodynamics, including change from baseline in muscle DUX4 transcriptome and plasma KHDC1L levels. In the first cohort, nine participants will receive three intravenous doses administered every four weeks (Q4W), randomized 2:1 to DYNE-302 1.5 mg/kg (approximate siRNA dose) or placebo. Following the completion of this cohort, we intend to evaluate higher dosing and less frequent administration. Participants who complete the placebo-controlled period may enter an open-label long-term extension and receive DYNE-302 for up to an additional 96 weeks. We intend to pursue a traditional approval pathway in the U.S. for DYNE-302. Pompe We are developing DYNE-401 for the treatment of Pompe disease. DYNE-401 is designed to deliver an enzyme replacement therapy to address the deficiency of the lysosomal enzyme, GAA, that causes Pompe disease. We engineered DYNE-401 by leveraging the FORCE platform to deliver GAA. We evaluated GAA delivery with our FORCE platform in vivo using hTfR1/6Neo mice, that were developed by crossing the well-established 6Neo mouse model of Pompe with mice expressing human transferrin receptor 1. Using this approach, intravenous administration cleared glycogen in muscle and the CNS and normalized lysosomal size in hTfR1/6Neo mice. This approach reduced serum neurofilament light chain, a biomarker of axonal injury, providing evidence of benefit in the CNS and displayed superior dose potency compared to GAA alone. Additional data with this approach supported the potential for monthly dosing, which is less frequent than approved enzyme replacement therapies for Pompe. Pipeline expansion We continue to explore additional applications for our proprietary FORCE platform, along with further iterations. To that end, we have identified two compounds, which we refer to as Conjugate 1 and Conjugate 2, utilizing a Fab conjugated to microtubule associated protein tau, or MAPT, siRNA designed to downregulate expression of all MAPT isoforms. Conjugate 1 utilizes our FORCE platform with the same Fab as our other programs. Conjugate 2 utilizes a modified form of the FORCE TfR1-binding Fab that has been further optimized for enhanced central nervous system delivery and potential use in neurological indications. In preclinical studies, both conjugates achieved robust MAPT RNA knockdown (approximately 75% for Conjugate 2) in both mice and nonhuman primates, with widespread and consistent delivery across brain regions, including the deep brain. Subcutaneous administration in mice achieved an equivalent reduction in MAPT RNA as compared to intravenous administration in mice. While maintaining our core focus on advancing our clinical programs in DMD and DM1, as well as our preclinical pipeline in neuromuscular diseases, we are currently evaluating next steps for the preclinical development of these conjugates. Recent Events In July 2026, we completed an underwritten public offering, pursuant to which we issued and sold 21,045,000 shares of our common stock, which included 2,745,000 shares issued upon the exercise in full by the underwriters of their option to purchase additional shares of common stock in the offering, which we refer to as the July 2026 offering. We estimate that 20 the net proceeds from the offering were approximately $405.0 million, after deducting underwriting discounts and commissions and offering expenses payable by us. Corporate information We were incorporated and commenced operations in 2017. Since our incorporation, we have devoted substantially all of our financial resources and efforts to organizing and staffing our company, business planning, raising capital, conducting research and development activities and filing and prosecuting patent applications. We do not have any products for sale and have not generated any revenue from product sales or otherwise. To date, we have principally raised capital through sales of equity securities and our borrowing under our Loan and Security Agreement, or the Loan Agreement, with Hercules Capital, Inc., or Hercules. Since our inception, we have incurred significant operating losses. Our ability to generate any product revenue or product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more product candidates. For the six months ended June 30, 2026 and 2025, we reported net losses of $299.4 million and $226.2 million, respectively. As of June 30, 2026, we had an accumulated deficit of $1.7 billion. We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We expect that our expenses and capital expenditure requirements will increase substantially in connection with our ongoing activities, particularly if and as we: •advance our product candidates for DMD, DM1, FSHD and Pompe and conduct research programs in additional indications; •expand the capabilities of our proprietary FORCE platform; •seek marketing approvals for any product candidates that successfully complete clinical trials; •obtain, expand, maintain, defend and enforce our intellectual property portfolio; •hire additional clinical, regulatory, scientific, medical affairs and commercial operations personnel; •establish manufacturing sources for any product candidate we may develop, including the Fab, linkers and therapeutic payload that will comprise the product candidate, and secure supply chain capacity to provide sufficient quantities for preclinical and clinical development and commercial supply; •establish a sales, marketing and distribution infrastructure to commercialize any products for which we may obtain marketing approval; and •add operational, legal, compliance, financial and management information systems and personnel to support our research, product development and future commercialization efforts, as well as to support our operations as a public company. We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for any product candidates we may develop. If we obtain regulatory approval for or otherwise commercialize any product candidates we may develop, we expect to incur significant expenses related to developing our commercialization capabilities to support product sales, marketing and distribution. Further, we expect to continue to incur additional costs associated with operating as a public company. As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements, and terms loans under our Loan Agreement with Hercules. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements or arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more product candidates we may develop. Because of the numerous risks and uncertainties associated with product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to raise capital, 21 maintain our research and development efforts, expand our business or continue our operations at planned levels, and as a result we may be forced to substantially reduce or terminate our operations. We believe that our cash, cash equivalents and marketable securities as of June 30, 2026, as well as the approximately $405.0 in net proceeds from the July 2026 offering, will enable us to fund our operating expenses, debt service obligations and capital expenditure requirements into the second quarter of 2028. We have based our estimate as to how long we expect we will be able to fund our operations, debt service obligations and capital expenditure requirements on assumptions that may prove to be wrong. We could use our available capital resources sooner than we currently expect, in which case we would be required to obtain additional financing, which may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. See “—Liquidity and capital resources” below. These estimates do not give effect to any additional funding tranches we may obtain access to under our Loan Agreement with Hercules, subject to the achievement of specified clinical, regulatory and commercial milestones, and do not give effect to any revenue we may generate on commercial sales of any products for which we obtain regulatory approval. Impact of tariffs The U.S. administration has announced or imposed multiple series of tariffs on U.S. trading partners. In response, several countries have threatened or imposed retaliatory measures, and multiple states have challenged these tariffs in court. While we have not experienced, and do not currently expect to experience, significant direct impact from these tariffs or retaliatory measures, the uncertainty surrounding the future of U.S. trade policy may negatively impact our supply chain operations and the costs of materials and production processes. Supply chain disruptions may impact the development, testing and clinical trials of our product candidates, and regulatory approval or commercial launch of any resulting product may be delayed or not obtained, which could significantly harm our business. The full extent of the future impact of these and other threatened measures remains uncertain. We continue to monitor these tariffs, retaliatory measures, and related litigation, and their possible effects on our business. See Part II, Item 1A. “Risk Factors—Risks related to regulatory approval and other regulatory and legal compliance matters” in this Quarterly Report for additional risks associated with current U.S. trade policy. Components of our results of operations Revenue We have not generated any revenue since our inception and do not expect to generate any revenue from the sale of products at least until 2027, if at all. If our development efforts are successful and we commercialize products, or if we enter into collaboration or license agreements with third parties, we may generate revenue in the future from product sales, as well as upfront, milestone and royalty payments from such collaboration or license agreements, or a combination thereof. Research and development expenses Research and development expenses consist primarily of costs incurred for our research activities and development of our product candidates. These expenses include: •development and operation of our proprietary FORCE platform; •employee-related expenses, including salaries, related benefits and stock-based compensation expense, for employees engaged in research and development functions; •expenses incurred in connection with our research programs and development of our product candidates, including those incurred under agreements with third parties, such as consultants and contract research organizations, or CROs, to conduct preclinical studies and clinical trials; •the cost of laboratory supplies and acquiring, developing and manufacturing materials for use in our research, preclinical studies and clinical trials, including those incurred under agreements with third parties, such as consultants and contract manufacturing organizations, or CMOs; •facilities, depreciation and other expenses, which include direct or allocated expenses for rent and maintenance of facilities and insurance; and •costs related to compliance with regulatory requirements. 22 We expense research and development costs as incurred. Advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed. Our direct external research and development expenses consist of costs that include fees, reimbursed materials and other costs paid to consultants, contractors, CMOs and CROs in connection with our development, manufacturing and clinical activities. We have not allocated our direct external research and development costs to specific programs or product candidates that are not in clinical development. Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials. Accordingly, we expect that our research and development expenses will increase substantially as we advance z-rostudirsen and z-basivarsen through clinical trials, in connection with our preclinical and clinical development activities of DYNE-302, our FSHD product candidate, and DYNE-401, our Pompe disease product candidate, and if, and as, we advance any other product candidates through preclinical studies and clinical trials. At this time, we cannot accurately estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any product candidates we may develop. In particular, manufacturing costs may vary significantly from quarter to quarter. For the full year 2026, we expect manufacturing costs to increase progressively each quarter as a result of long lead times to build supply and we project manufacturing costs for z-rostudirsen, z-basivarsen and other pipeline product candidates to represent 55-65% of total research and development expenses for the full year 2026. Further, we project clinical trial costs related to z-rostudirsen, z-basivarsen and other pipeline product candidates to represent 10-20% and of total research and development expenses for the full year 2026. The successful development of any product candidate is highly uncertain. This is due to the numerous risks and uncertainties associated with product development, including the following: •the timing and progress of preclinical and clinical development activities; •the number and scope of programs we decide to pursue and their regulatory paths to market; •the need to raise funding to complete preclinical and clinical development of any product candidates we may develop; •our ability to establish new licensing or collaboration arrangements and the progress of the development efforts of third parties with whom we may enter into such arrangements; •our ability to maintain our current research and development programs and to establish new programs; •the successful initiation, enrollment and completion of clinical trials with safety, tolerability and efficacy profiles that are satisfactory to the FDA or any comparable foreign regulatory authority; •the receipt and related terms of regulatory approvals from applicable regulatory authorities for any product candidates we may develop; •the availability of specialty raw materials for use in production of any product candidate we may develop; •establishing agreements with third-party manufacturers for supply of product candidate components for our clinical trials; •our ability to obtain and maintain patents, trade secret protection and regulatory exclusivity, both in the United States and internationally; •our ability to protect our other rights in our intellectual property portfolio; •commercializing product candidates, if and when approved, whether alone or in collaboration with others; and •obtaining and maintaining third-party insurance coverage and adequate reimbursement for any approved products. A change in the outcome of any of these variables with respect to the development of any product candidate we may develop could significantly change the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any product candidate we may develop. 23 General and administrative expenses General and administrative expenses consist primarily of employee-related expenses, including salaries, related benefits and stock-based compensation, for employees in executive, finance, corporate and business development, commercial and administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax and administrative consulting services; insurance costs; administrative travel expenses; commercial readiness activities; and facility-related expenses, which include allocated expenses for rent, depreciation and maintenance of facilities and other operating costs. We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our growth strategy. In addition, if we obtain regulatory approval for a product candidate and do not enter into a third-party commercialization collaboration, we expect to incur significant expenses related to building a sales and marketing team to support product sales, marketing and distribution activities. Interest income Interest income consists of interest earned on our cash, cash equivalents and marketable securities. Interest expense Interest expense consists of amortization of debt issuance costs and discount and interest expense under the Loan Agreement with Hercules. Other income (expense), net Other income (expense), net consists of realized gains and losses on sales of marketable securities and foreign currency gains and losses. Income taxes Since our inception, we have not recorded any U.S. federal or state income tax benefits for the net losses we have incurred in any year or for our earned research and development tax credits, due to our uncertainty of realizing a benefit from those items. Results of operations Comparison of the three months ended June 30, 2026 and 2025 The following table summarizes our results of operations for the three months ended June 30, 2026 and 2025: Three Months Ended June 30, (in thousands) 2026 2025 Change Operating expenses: Research and development $ 152,169 $ 99,236 $ 52,933 General and administrative 29,492 16,555 12,937 Total operating expenses 181,661 115,791 65,870 Loss from operations (181,661 ) (115,791 ) (65,870 ) Other income (expense): Interest income 7,788 6,625 1,163 Interest expense (4,595 ) (94 ) (4,501 ) Other expense, net (88 ) (1,597 ) 1,509 Total other income (expense), net 3,105 4,934 (1,829 ) Net loss $ (178,556 ) $ (110,857 ) $ (67,699 ) 24 Research and development expenses The following table summarizes our research and development expenses for the three months ended June 30, 2026 and 2025: Three Months Ended June 30, (in thousands) 2026 2025 Change Direct research and development expenses by product candidate: Z-rostudirsen (DMD) $ 52,321 $ 29,525 $ 22,796 Z-basivarsen (DM1) 48,979 34,677 14,302 Unallocated research and development expenses: Platform and external research and development 14,117 7,425 6,692 Personnel related (including stock-based compensation) 27,832 20,804 7,028 Facility-related and other 8,920 6,805 2,115 Total research and development expenses $ 152,169 $ 99,236 $ 52,933 Expenses related to z-rostudirsen increased in the three months ended June 30, 2026 compared to the three months ended June 30, 2025. This was attributable to increased manufacturing activity in the second quarter of 2026 of drug components primarily for clinical supply for the long-term extension of the DELIVER trial and the global confirmatory Phase 3 clinical trial of z-rostudirsen, FORZETTO, that commenced in the second quarter of 2026. Additionally, higher clinical costs were incurred in the second quarter of 2026 due to the commencement of the FORZETTO trial. Expenses related to z-basivarsen increased in the three months ended June 30, 2026 compared to the three months ended June 30, 2025. This was primarily attributable to increased manufacturing activity in the second quarter of 2026 of drug substance and components primarily for clinical supply for the registrational expansion cohort of the ACHIEVE trial and the global confirmatory Phase 3 clinical trial of z-basivarsen, HARMONIA, that commenced in the first quarter of 2026. Additionally, higher clinical costs were incurred in the second quarter of 2026 due to the completion of enrollment of the registrational expansion cohort of the ACHIEVE trial in the second quarter of 2026 and increased enrollment in the HARMONIA trial. The increase in platform and external research and development expenses in the three months ended June 30, 2026 compared to the three months ended June 30, 2025 was due to increased external research activity associated with our preclinical programs and product candidates. The increase in personnel-related expenses was primarily due to the increase of 39 employees in our research and development headcount and higher stock-based compensation expense for awards granted to new hires and existing employees. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of research and development personnel. General and administrative expenses The following table summarizes our general and administrative expenses for the three months ended June 30, 2026 and 2025: Three Months Ended June 30, (in thousands) 2026 2025 Change Personnel-related $ 8,747 $ 4,352 $ 4,395 Stock-based compensation expense 7,190 4,877 2,313 Professional and consulting fees 9,975 5,094 4,881 Facility-related and other 3,580 2,232 1,348 Total general and administrative expenses $ 29,492 $ 16,555 $ 12,937 The increase in personnel-related and stock-based compensation expenses in the three months ended June 30, 2026 compared to the three months ended June 30, 2025 was due to the increase of 44 employees in our general and administrative headcount. Professional and consulting fees increased due to higher consulting costs for the preparation activities for the potential launch of z-rostudirsen and the overall growth of the organization in the three months ended June 30, 2026. Facility-related and other expenses increased due to higher costs of supporting a larger number of general and administrative personnel in the three months ended June 30, 2026. 25 Interest income Interest income for the three months ended June 30, 2026 and 2025 was $7.8 million and $6.6 million, respectively, due to interest earned on invested cash balances. The increase in interest income was due to increased cash, cash equivalents and marketable securities balances in the three months ended June 30, 2026 compared to the three months ended June 30, 2025. Interest expense Interest expense for the three months ended June 30, 2026 was $4.6 million due to our Loan Agreement with Hercules and interest owed on our vendor financing arrangement. Interest expense for the three months ended June 30, 2025 was less than $0.1 million due to our Loan Agreement with Hercules. Other expense, net Other expense, net, for the three months ended June 30, 2026 and 2025 was $0.1 million and $1.6 million, respectively, in each quarter due to realized foreign currency losses. Comparison of the six months ended June 30, 2026 and 2025 The following table summarizes our results of operations for the six months ended June 30, 2026 and 2025: Six Months Ended June 30, (in thousands) 2026 2025 Change Operating expenses: Research and development $ 253,175 $ 205,683 $ 47,492 General and administrative 53,763 32,480 21,283 Total operating expenses 306,938 238,163 68,775 Loss from operations (306,938 ) (238,163 ) (68,775 ) Other income (expense): Interest income 16,544 13,725 2,819 Interest expense (8,797 ) (94 ) (8,703 ) Other expense, net (219 ) (1,687 ) 1,468 Total other income (expense), net 7,528 11,944 (4,416 ) Net loss $ (299,410 ) $ (226,219 ) $ (73,191 ) Research and development expenses The following table summarizes our research and development expenses for the six months ended June 30, 2026 and 2025: Six Months Ended June 30, (in thousands) 2026 2025 Change Direct research and development expenses by product candidate: Z-rostudirsen (DMD) $ 90,069 $ 51,238 $ 38,831 Z-basivarsen (DM1) 63,761 80,111 (16,350 ) Unallocated research and development expenses: Platform and external research and development 25,582 15,040 10,542 Personnel related (including stock-based compensation) 55,765 45,892 9,873 Facility related and other 17,998 13,402 4,596 Total research and development expenses $ 253,175 $ 205,683 $ 47,492 Expenses related to z-rostudirsen increased in the six months ended June 30, 2026 compared to the six months ended June 30, 2025. This was attributable to increased manufacturing activity of drug substance and components in the six months ended June 30, 2026, primarily for clinical supply for the long-term extension of the DELIVER trial and the global confirmatory Phase 3 clinical trial of z-rostudirsen, FORZETTO, that commenced in the second quarter of 2026. Additionally, higher clinical costs were incurred in the six months ended June 30, 2026 due to the commencement of the FORZETTO trial. Expenses related to z-basivarsen decreased in the six months ended June 30, 2026 compared to the 26 six months ended June 30, 2025. This was primarily attributable to higher manufacturing activity for process performance qualification batches of oligonucleotide payload and the timing of drug substance conjugation activities in the six months ended June 30, 2025, which were partially offset by higher clinical costs in the six months ended June 30, 2026 due to the completion of enrollment of the registrational expansion cohort of the ACHIEVE trial in the second quarter of 2026 and increased enrollment in the HARMONIA trial. The increase in platform and external research and development expenses in the six months ended June 30, 2026 compared to the six months ended June 30, 2025 was primarily due to increased external research activity associated with our preclinical programs and product candidates. The increase in personnel-related expenses was primarily due to the increase of 39 employees in our research and development headcount and higher stock-based compensation expense for awards granted to new hires and existing employees. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of research and development personnel. General and administrative expenses The following table summarizes our general and administrative expenses for the six months ended June 30, 2026 and 2025: Six Months Ended June 30, (in thousands) 2026 2025 Change Personnel-related $ 16,268 $ 8,157 $ 8,111 Stock-based compensation expense 13,372 9,706 3,666 Professional and consulting fees 17,740 10,757 6,983 Facility-related and other 6,383 3,860 2,523 Total general and administrative expenses $ 53,763 $ 32,480 $ 21,283 The increase in personnel-related and stock-based compensation expenses in the six months ended June 30, 2026 compared to the six months ended June 30, 2025 was due to the increase of 44 employees in our general and administrative headcount. Professional and consulting fees increased due to higher consulting costs for the preparation activities for the potential launch of z-rostudirsen and the overall growth of the organization in the six months ended June 30, 2026. Facility-related and other expenses increased due to higher costs of supporting a larger number of general and administrative personnel in the six months ended June 30, 2026. Interest income Interest income for the six months ended June 30, 2026 and 2025 was $16.5 million and $13.7 million, respectively, due to interest earned on invested cash balances. The increase in interest income was due to an increased cash, cash equivalents and marketable securities balance throughout the six months ended June 30, 2026 compared to the six months ended June 30, 2025. Interest expense Interest expense for the six months ended June 30, 2026 was $8.8 million due to our Loan Agreement with Hercules and interest owed on our vendor financing arrangement. Interest expense for the six months ended June 30, 2025 was less than $0.1 million due to our Loan Agreement with Hercules. Other expense, net Other expense for the six months ended June 30, 2026 and 2025 was $0.2 million and $1.7 million, respectively, due to realized foreign currency losses. Liquidity and capital resources Sources of liquidity Since our inception, we have incurred significant operating losses. We expect to incur significant expenses and operating losses for the foreseeable future as we support our continued research activities and development of our product candidates and platform. We have not yet commercialized any product candidates, and we do not expect to generate revenue from sales of any product candidates at least until 2027, if at all. To date, we have funded our operations primarily with proceeds from sales of equity securities and our borrowing under the Loan Agreement with Hercules. As of June 30, 2026 we had cash, cash equivalents and marketable securities of $898.5 million. 27 In November 2021, we entered into an Open Market Sale AgreementSM, or the Sales Agreement, with Jefferies LLC, or Jefferies. On March 5, 2024, we filed a universal shelf registration statement on Form S-3, or the 2024 Shelf Registration Statement, and included a prospectus relating to the Sales Agreement. Under the 2024 Shelf Registration Statement, we may offer and sell debt securities, common stock, preferred stock, units and/or warrants from time to time at an indeterminate aggregate offering price in one or more offerings. In November 2024, we filed a prospectus supplement relating to the Sales Agreement, pursuant to which, in accordance with the Sales Agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $300.0 million, which we refer to as our at-the-market offering program. Sales of common stock under the Sales Agreement through Jefferies may be made by any method that is deemed an “at-the-market” offering as defined in Rule 415(a)(4) under the Securities Act. During the six months ended June 30, 2026, we did not issue or sell any shares of common stock pursuant to the Sales Agreement. In June 2025, we entered into the Loan Agreement with Hercules, in its capacity as administrative agent and collateral agent and as a lender, and certain other financial institutions that from time to time become parties to the Loan Agreement as lenders, which we refer to collectively as the Lenders. In December 2025, we entered into the First Amendment to the Loan Agreement with Hercules. In June 2026, we entered into the Second Amendment to the Loan Agreement with Hercules. The Loan Agreement, as amended by the First and the Second Amendment, provides for term loans in an aggregate principal amount of up to $400.0 million under multiple tranches, available as follows: (i) an initial term loan tranche funded on the closing date of the Loan Agreement in aggregate principal amount of $100.0 million; (ii) subject to the achievement of specified clinical, regulatory and commercial milestones, and after the borrowing of the second term loan tranche of $50.0 million in December 2025 and third term loan tranche of $50.0 million in June 2026, three additional term loan tranches totaling up to $125.0 million; and (iii) subject to approval by the Lenders’ investment committee in their discretion, a final term loan tranche of up to $75.0 million. At June 30, 2026, the principal term loan balance was $200.0 million. Refer to Note 7, “Debt” in the accompanying notes to the condensed consolidated financial statements for a discussion of the Loan Agreement with Hercules. In July 2026, we completed the July 2026 offering, pursuant to which we issued and sold 21,045,000 shares of our common stock. We estimate that the net proceeds from the offering were approximately $405.0 million, after deducting underwriting discounts and commissions and offering expenses payable by us. Cash flows The following table summarizes our sources and uses of cash for each of the periods presented: Six Months Ended June 30, (in thousands) 2026 2025 Net cash used in operating activities $ (275,208 ) $ (200,596 ) Net cash (used in) provided by investing activities (7,187 ) 8,232 Net cash provided by financing activities 65,174 242,015 Net (decrease) increase in cash, cash equivalents and restricted cash $ (217,221 ) $ 49,651 Operating activities During the six months ended June 30, 2026, operating activities used $275.2 million of cash, due to our net loss of $299.4 million and net cash used by changes in our operating assets and liabilities of $4.8 million, partially offset by non-cash charges of $29.0 million. Net cash used in changes in our operating assets and liabilities primarily consisted of a $23.4 million increase in prepaid expenses and other current assets, partially offset by a $14.2 million increase in accounts payable and other liabilities and a $4.4 million decrease in other non-current assets. During the six months ended June 30, 2025, operating activities used $200.6 million of cash, due to our net loss of $226.2 million, partially offset by non-cash charges of $23.6 million and net cash provided by changes in our operating assets and liabilities of $2.0 million. Net cash provided by changes in our operating assets and liabilities primarily consisted of a $2.8 million decrease in prepaid expenses and other current assets, partially offset by a $0.8 million decrease in accounts payable and other liabilities. Changes in our operating assets and liabilities during these periods were generally due to the growth of our business, increased clinical trial activity, increased manufacturing activities, advancement of our product candidates and the timing of vendor invoices and payments. 28 Investing activities During the six months ended June 30, 2026, net cash used in investing activities was $7.2 million due to purchases of marketable securities of $107.1 million and purchases of property and equipment of $1.7 million, partially offset by maturities of marketable securities of $58.2 million and sales of marketable securities of $43.4 million. During the six months ended June 30, 2025, net cash provided by investing activities was $8.2 million due to maturities of marketable securities of $107.7 million and sales of marketable securities of $8.5 million, partially offset by purchases of marketable securities of $106.9 million and purchases of property and equipment of $1.0 million. Financing activities During the six months ended June 30, 2026, net cash provided by financing activities was $65.2 million, including $49.5 million in net proceeds from the third term loan tranche under our Loan Agreement with Hercules, $18.0 million in proceeds from our vendor financing arrangement and $2.0 million in proceeds received from stock option exercises. These cash inflows were partially offset by $3.9 million in repayments related to our vendor financing arrangement and the payment of $0.4 million of issuance costs from the follow-on public offering we completed in December 2025, pursuant to which we issued and sold 21,827,549 shares of our common stock and from which we received net proceeds of $377.7 million, after deducting underwriting discounts and commissions and offering expenses paid by us. During the six months ended June 30, 2025, net cash provided by financing activities was $242.0 million, consisting of $140.6 million in aggregate net proceeds from sales of our common stock under our at-the-market offering program, $98.8 million in net proceeds from the initial term loan tranche under the Loan Agreement with Hercules and $2.6 million in net proceeds received from stock option exercises. Funding requirements We expect our expenses to increase in connection with our ongoing activities, particularly as we advance the clinical development of z-rostudirsen and z-basivarsen, the development of our FSHD, Pompe and DMD franchise programs and additional research programs. The timing and amount of our operating expenditures will depend largely on: •the identification of additional product candidates; •the scope, progress, costs and results of preclinical and clinical development of any product candidates we may develop; •the costs, timing and outcome of regulatory review of any product candidates we may develop; •our decision to initiate a clinical trial, not to initiate a clinical trial or to terminate an existing clinical trial; •changes in laws or regulations applicable to any product candidates we may develop, including but not limited to clinical trial requirements for approvals; •the cost and timing of obtaining materials to produce adequate product supply for any preclinical or clinical development of any product candidate we may develop; •the costs and timing of future commercialization activities and related preparations, including product manufacturing, marketing, sales and distribution, for any product candidate we may develop for which we obtain marketing approval; •the legal costs involved in prosecuting patent applications and enforcing patent claims and other intellectual property claims; •additions or departures of key scientific or management personnel; •our ability to establish and maintain collaborations on favorable terms, if at all, as well as the costs and timing of any collaboration, license or other arrangement, including the terms and timing of any milestone payments thereunder; and •the costs of operating as a public company. We believe that our cash, cash equivalents and marketable securities as of June 30, 2026, as well as the approximately $405.0 in net proceeds from the July 2026 offering, will enable us to fund our operating expenses, debt service obligations, and capital expenditure requirements into the second quarter of 2028. We have based this estimate on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect. 29 Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances, and marketing, distribution or licensing arrangements with third parties. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders may be materially diluted, and the terms of such securities could include liquidation or other preferences that adversely affect the rights of holders of our common stock. Debt financing and preferred equity financing, if available, may involve agreements that include restrictive covenants that limit our ability to take specified actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements or arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more of our product candidates we may develop. See Part II, Item 1A. “Risk Factors” in this Quarterly Report for additional risks associated with our substantial capital requirements. Contractual and other obligations We enter into contracts in the normal course of business with CROs, CMOs and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. Except for the master manufacturing services agreements described below, these contracts typically do not contain significant minimum purchase commitments and are generally cancelable by us upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of our service providers, up to the date of cancellation and in the case of certain arrangements with CROs and CMOs may include non-cancelable fees. We have also entered into a license agreement with the University of Mons under which we are obligated to make specified milestone and royalty payments. The payment obligations under this agreement are contingent upon future events, such as our achievement of specified development, regulatory and commercial milestones, or generating product sales. We are unable to estimate the timing or likelihood of achieving these milestones or generating future product sales. For additional information about our license agreement with the University of Mons and amounts that could become payable in the future under that agreement, see Item 1. "Business—Intellectual Property—License Agreement with the University of Mons" in the Annual Report on Form 10-K filed with the SEC on March 2, 2026. On December 4, 2020, we entered into a lease agreement for office and laboratory space, which was amended in January 2021, March 2021 and June 2021. The lease has a term of 8.5 years that commenced when we gained access to the office and laboratory space in September 2021. Our obligation for the payment of the base rent began in April 2022 and is $0.4 million per month, increasing to $0.5 million per month during the term of the lease. We have two options to extend the term of the lease, each for a period of an additional five years. On January 15, 2025, we entered into a master manufacturing services agreement with a CMO which secures capacity at the CMO's manufacturing facilities for certain of our product candidates and components thereof. As of June 30, 2026, we have paid $26.9 million towards non-current assets under this agreement and pursuant to a mutually agreed rolling forecast we have committed to pay an additional $99.7 million in fees through June 2028. In specified termination circumstances, the agreement requires us to pay the CMO for services completed, the cost of the CMO's raw materials that cannot be repurposed and specified cancellation fees. This agreement formalizes and supersedes a letter agreement that we entered into with the CMO on July 18, 2024. On October 31, 2025, we entered into another master manufacturing services agreement with a CMO which also secures capacity at the CMO's manufacturing facilities for certain of our product candidate components. The agreement obligates us to compensate the CMO for producing certain of our product candidate components pursuant to a mutually agreed rolling forecast, pursuant to which, as of June 30, 2026, we have committed to pay an additional $59.8 million in fees through December 2027. In specified termination circumstances, the agreement requires us to pay the CMO for services completed, the cost of the CMO's raw materials that cannot be repurposed, capital equipment and certain manufacturing activities previously committed to. Critical accounting estimates Our condensed consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of our condensed consolidated financial statements and related 30 disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions. We define our critical accounting policies as those accounting principles generally accepted in the United States of America that require us to make subjective estimates and judgments about matters that are uncertain and are likely to have a material impact on our financial condition and results of operations as well as the specific manner in which we apply those principles. Management has determined that our most critical accounting policies are those relating to accrued research and development expenses and stock-based compensation. As we advance our product candidates into and through clinical development, we expect research and development expenses and, in particular, our accounting for accrued research and development expenses to be an increasingly important critical accounting policy. There have been no significant changes to our critical accounting policies or estimates from those described in our Annual Report on Form 10-K filed with the SEC on March 2, 2026. Recently Issued and Adopted Accounting Pronouncements Refer to Note 2, "Summary of Significant Accounting Policies" in the accompanying notes to the condensed consolidated financial statements for a discussion of significant accounting policies. There are no recently issued accounting pronouncements that have not yet been adopted that are expected to have a material impact on the Company’s financial statements as of June 30, 2026.