ACVR2A x TGF-β

Elritercept continued to demonstrate a durable transfusion independence in lower-risk myelodysplastic syndromes, including in patients with high transfusion burden Durable clinical responses were associated with improvements in patient-reported measures of fatigue Data from ongoing Phase 2 clinical trial in myelofibrosis continue to demonstrate that elritercept can not only ameliorate ineffective hematopoiesis and address cytopenias, but also provide broader clinical benefit, as supported by observed reductions in spleen volume and improved total symptom scores Keros will host a corporate update call and webcast today, June 17, 2024, at 8:00 a.m. ET LEXINGTON, Mass., June 17, 2024 (GLOBE NEWSWIRE) -- Keros Therapeutics, Inc. (“Keros” or the “Company”) (Nasdaq: KROS), a clinical-stage biopharmaceutical company focused on developing and commercializing novel therapeutics to treat a wide range of patients with disorders that are linked to dysfunctional signaling of the transforming growth factor-beta (“TGF-ß”) family of proteins, today announced that it presented additional data from its two ongoing Phase 2 clinical trials of elritercept (KER-050), one in patients with very low-, low-, or intermediate-risk myelodysplastic syndromes (“MDS”) and one in patients with myelofibrosis (“MF”), at the 29th Annual Hybrid Congress of the European Hematology Association (“EHA”), held in person in Madrid, Spain and virtually from June 13 through 16, 2024. In addition, Keros presented preclinical data showing that, in an animal model of MF, a research form of elritercept promoted erythropoiesis, mitigated anemia associated with MF, improved anemia associated with ruxolitinib therapy and improved muscle mass and function. “The data we presented at EHA continues to show an encouraging broad pro elritercept and supports its potential to treat not just the disease-associated cytopenias, but also impact the pathogenesis of MDS and MF,” said Jasbir S. Seehra, Ph.D., President and Chief Executive Officer. “We are excited by the results we presented, including the durability of transfusion independence observed with elritercept, and are excited to progress towards initiating a registrational Phase 3 clinical trial in MDS following positive feedback from the U.S. Food and Drug Administration.” Select Clinical Presentations Durable Clinical Benefit with Elritercept (KER-050) Treatment: Findings From an Ongoing Phase 2 Trial in Participants with Lower-Risk MDS This ongoing, open-label, two-part, Phase 2 clinical trial is evaluating elritercept in patients with very low-, low-, or intermediate-risk MDS. As of April 3, 2024 (the “data cut-off date”), 87 patients had received at least one dose of elritercept at the recommended Part 2 dose (“RP2D”) (collectively, the “safety population”). Of these patients in the safety population, 81 had completed at least 24 weeks of treatment or discontinued as of the data cut-off date (collectively, the modified intent-to-treat 24-week population, or the “mITT24 patients”). Data for hematological response and markers of hematopoiesis were presented from exploratory analyses of these mITT24 patients. All data presented from this trial is as of the data cut-off date. Of the 87 patients in the safety population, 57.5% (n=50) were high transfusion burden (“HTB”) while 25.3% (n=22) were low transfusion burden and 17.2% (n=15) were non-transfused (“NT”). Elritercept was observed to be generally well-tolerated in the safety population. There were three cases of fatal treatment-emergent adverse events (“TEAEs”) in the trial that were all deemed unrelated to treatment. The most commonly reported TEAEs (in ≥15% of patients) were diarrhea, fatigue, dyspnea, dizziness, COVID-19, nausea and anemia. No patients had progressed to acute myeloid leukemia. 55.6% (n=45/81) of the mITT24 patients achieved an overall erythroid response over the first 24 weeks of treatment, which is defined as meeting either modified International Working Group 2006 Hematological improvement-erythroid (“HI-E”) or transfusion independence (“TI”) for at least eight weeks in transfusion-dependent patients who required ≥ 2 red blood cell (“RBC”) units transfused at baseline. Additional data from the mITT24 patients include: 41.3% (n=26/63) of the TI-evaluable patients achieved TI for at least eight weeks over the first 24 weeks of treatment. 16 of those 26 patients (61.5%) achieved TI for at least 24 weeks over the first 48 weeks of treatment. Of the patients with HTB, 34.8% (n=16/46) achieved TI for at least eight weeks during the first 24 weeks of treatment. Eight of those 16 patients (50.0%) achieved TI for at least 24 weeks over the first 48 weeks of treatment. Of the TI-evaluable patients with baseline erythropoietin level less than 500 U/L, 50.0% (n=25/50) achieved TI for at least eight weeks over the first 24 weeks of treatment. Of the TI-evaluable patients with baseline erythropoietin level less than 500 U/L and HTB, 42.9% (n=15/35) achieved TI for at least eight weeks over the first 24 weeks of treatment. The median duration of transfusion independence was not met as of the data-cutoff date. 61.5% (n=16/26) of patients with a TI response had ongoing TI as of the data-cutoff. Of the patients that achieved TI, 42.3% (n=11/26) had responses of greater than one year, with all ongoing as of the data cut-off date. The FACIT-Fatigue scale, a measure of self-reported fatigue and its impact upon daily activities and function, was utilized to assess health-related quality of life in 62 of the mITT24 patients who were TI-evaluable and with baseline FACIT-Fatigue assessment. A difference of three in the FACIT-Fatigue scale is considered a minimally clinically important difference. In this group, patients who achieved TI had durable and clinically meaningful improvements in self-reported fatigue. Patients achieving TI of 24 weeks or longer had a mean change from baseline of 6.6 (n=12) versus patients who did not achieve TI of at least 24 weeks, who reported a mean change from baseline of -2.7 (n=25), for a mean difference of 9.4. The majority of patients enrolled in this ongoing trial had HTB and/or multi-lineage dysplasia, indicating a difficult-to-treat trial population. Durable TI responses continue to be observed in a broad range of patients with lower-risk MDS, including in those with HTB, which support the potential for elritercept to ameliorate ineffective hematopoiesis across multiple lineages in patients with MDS. Patients who achieved TI showed clinically meaningful improvements in FACIT-Fatigue scores, indicating that elritercept may improve quality of life in patients with lower-risk MDS. Elritercept (KER-050) Demonstrated Potential to Treat Myelofibrosis and Mitigate Ruxolitinib-Associated Cytopenias in the Phase 2 RESTORE Trial This ongoing, open-label, two-part Phase 2 clinical trial is evaluating elritercept administered with or without ruxolitinib in patients with MF who have anemia and were either currently on, failed, or ineligible for ruxolitinib at baseline. Safety data are presented for all patients that received at least one dose of elritercept (n=54) as of the data cut-off date. Evaluations of markers of hematopoiesis and anemia over 12 weeks, along with measurements of spleen volume and symptom scores (by the MF-symptom assessment form-Total Symptom Score, or “MF-SAF-TSS”) over 24 weeks, were presented for dose levels 1 through 4 in Part 1 and the RP2D, ranging from 0.75 mg/kg to 5.0 mg/kg (collectively, the “efficacy evaluable patients”). Enrollment of Part 1 of the trial, the dose escalation portion, is complete. Part 2, the dose expansion portion, is open and enrolling with a RP2D of 3.75 mg/kg with the option to up-titrate to 5.0 mg/kg. All data presented from this trial is as of the data cut-off date. Elritercept was generally well-tolerated by the safety population. There were four cases of fatal TEAEs in the trial that were each deemed unrelated to treatment. The most commonly reported TEAEs (in ≥15% of patients) were thrombocytopenia and diarrhea. The majority of treatment-related TEAEs were mild to moderate, with three patients experiencing Grade 3 or higher treatment-related TEAEs. Additional data from the efficacy evaluable patients include: Increases in hemoglobin were observed in the majority of evaluable non-transfusion dependent patients in both arms over a 12-week period within the first 24 weeks, suggesting that elritercept has the potential to address anemia due to MF and ruxolitinib-associated anemia. 60.6% (n=20/33) of patients that received at least three RBC units per 12 weeks at baseline in both arms and all dose levels tested showed reductions in transfusion burden over 12 weeks within the first 24 weeks. 60% (n=12/20) of the patients who showed reductions in transfusion burdens had a reduction of 50% or greater in the number of transfusions. Of the patients receiving 3.0 mg/kg of elritercept or higher in combination with ruxolitinib, 72.7% (n=8/11) had reduction of 50% or greater and 45.5% (n=5/11) of patients achieved TI. At Week 24, some reduction in spleen volume was observed in 52.9% (n=9/17) of patients with baseline spleen size ≥ 450 cm3 and a Week 24 spleen assessment, including three patients who had reductions of 35% or greater. Reductions in spleen volume in the combination arm generally occurred without an increase in ruxolitinib dose. At Week 24, some reduction in disease symptoms was observed in a majority of patients with at least two symptoms with an average score ≥ 3 or an average total score of ≥ 10 on the MF-SAF-TSS questionnaire at baseline and a week 24 MF-SAF-TSS assessment. Three patients had reductions of at least 50%, including two in the monotherapy arm and one in the combination arm. The data support the potential of elritercept to ameliorate ineffective hematopoiesis and address cytopenias due to MF and associated with ruxolitinib, and provide broader clinical benefit in patients, as supported by the observed reduction in spleen volume and improvement in total symptom scores. Conference Call and Webcast Information Keros will host a corporate update conference call and webcast today, June 17, 2024, at 8:00 a.m. Eastern time, to discuss the additional data from its two ongoing Phase 2 clinical trials of elritercept, one in patients with MDS and one in patients with MF, as well as additional updates to the Company's pipeline. The conference call will be webcast live at: . The live teleconference may be accessed by dialing (877) 407-0309 (domestic) or (201) 389-0853 (international). An archived version of the call will be available in the Investors section of the Keros website at for 90 days following the conclusion of the call. About the Ongoing Phase 2 Clinical Trial of Elritercept in Patients with MDS (NCT04419649) Keros is conducting an open label, two-part, multiple ascending dose Phase 2 clinical trial to evaluate elritercept in patients with very low-, low-, or intermediate-risk MDS who either have or have not previously received treatment with an erythroid stimulating agent. The primary objective of this trial is to assess the safety and tolerability of elritercept in patients with MDS that are RS positive or non-RS. The primary objective of Part 2 of this trial is confirmation of the safety and tolerability of the RP2D (3.75 mg/kg and 5.0 mg/kg). The secondary objectives of this trial are to evaluate the pharmacokinetics, pharmacodynamics and efficacy of elritercept. About the Ongoing Phase 2 Clinical Trial of Elritercept in Patients with MF-Associated Cytopenias (RESTORE trial; NCT05037760) Keros is conducting an open label, two-part, multiple ascending dose Phase 2 clinical trial to evaluate elritercept as a monotherapy and in combination with ruxolitinib in patients with MF-associated cytopenias. The primary objective of this trial is to assess the safety and tolerability of elritercept in patients with MF-associated cytopenias. The primary objective of Part 2 of this trial is confirmation of the safety and tolerability of the RP2D (3.75 mg/kg and 5.0 mg/kg). The secondary objectives of this trial are to evaluate the pharmacokinetics, pharmacodynamics and efficacy of elritercept administered with or without ruxolitinib. About Elritercept Keros’ lead product candidate, elritercept, is an engineered ligand trap comprised of a modified ligand-binding domain of the TGF-ß receptor known as activin receptor type IIA that is fused to the portion of the human antibody known as the Fc domain. Elritercept is being developed for the treatment of low blood cell counts, or cytopenias, including anemia and thrombocytopenia, in patients with MDS and in patients with MF. About Keros Therapeutics, Inc. Keros is a clinical-stage biopharmaceutical company focused on developing and commercializing novel therapeutics to treat a wide range of patients with disorders that are linked to dysfunctional signaling of the TGF-ß family of proteins. We are a leader in understanding the role of the TGF-ß family of proteins, which are master regulators of the growth, repair and maintenance of a number of tissues, including blood, bone, skeletal muscle, adipose and heart tissue. By leveraging this understanding, we have discovered and are developing protein therapeutics that have the potential to provide meaningful and potentially disease-modifying benefit to patients. Keros’ lead product candidate, elritercept, is being developed for the treatment of low blood cell counts, or cytopenias, including anemia and thrombocytopenia, in patients with MDS and in patients with MF. Keros’ second product candidate, cibotercept (KER-012), is being developed for the treatment of pulmonary arterial hypertension and for the treatment of cardiovascular disorders. Keros’ third product candidate, KER-065, is being developed for the treatment of obesity and for the treatment of neuromuscular diseases. Cautionary Note Regarding Forward-Looking Statements Statements contained in this press release regarding matters that are not historical facts are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Words such as “potential,” “progress” and “will” or similar expressions are intended to identify forward-looking statements. Examples of these forward-looking statements include statements concerning: Keros’ expectations regarding its growth, strategy, progress and the design, objectives, endpoints and timing of its clinical trials for elritercept, including its regulatory plans; the potential of elritercept to treat beyond MF- and MDS-associated cytopenias to have a direct effect on the pathogenesis of MF and MDS, respectively; the potential of KER-050 to ameliorate ineffective hematopoiesis across multiple lineages in patients with MDS and to improve quality of life in patients with lower-risk MDS; and the potential of KER-050 to address anemia due to MF and ruxolitinib-associated anemia. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. These risks and uncertainties include, among others: Keros’ limited operating history and historical losses; Keros’ ability to raise additional funding to complete the development and any commercialization of its product candidates; Keros’ dependence on the success of its product candidates, elritercept, cibotercept and KER-065; that Keros may be delayed in initiating, enrolling or completing any clinical trials; competition from third parties that are developing products for similar uses; Keros’ ability to obtain, maintain and protect its intellectual property; and Keros’ dependence on third parties in connection with manufacturing, clinical trials and preclinical studies. These and other risks are described more fully in Keros’ filings with the Securities and Exchange Commission (“SEC”), including the “Risk Factors” section of the Company’s Quarterly Report on Form 10-Q, filed with the SEC on May 8, 2024, and its other documents subsequently filed with or furnished to the SEC. All forward-looking statements contained in this press release speak only as of the date on which they were made. Except to the extent required by law, Keros undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made. Investor Contact: Justin Frantz jfrantz@kerostx.com 617-221-6042

Phase 2 EMBRAZE proof-of-concept trial designed to assess apitegromab's ability to safely preserve lean muscle mass in individuals on GLP-1 receptor agonist therapy for obesity New preclinical head-to-head comparison shows that SRK-439 is more potent than an anti-ActRII antibody in maintaining lean mass in diet-induced obesity (DIO) mice; lean mass loss with SRK-439, 1mg/kg dose was equivalent to anti-ActRII antibody, 20mg/kg dose Company hosting Investor Event today in New York City focusing on its selective latent myostatin inhibition programs in Spinal Muscular Atrophy and obesity with presentations from executive leadership and key experts CAMBRIDGE, Mass.--(BUSINESS WIRE)-- Scholar Rock (NASDAQ: SRRK), a late-stage biopharmaceutical company focused on advancing innovative treatments for spinal muscular atrophy (SMA), cardiometabolic disorders, and other serious diseases where protein growth factors play a fundamental role, today announced the initiation of the Phase 2 EMBRAZE proof-of-concept trial, designed to assess the safety and efficacy of apitegromab, a highly selective myostatin inhibitor, to preserve lean muscle mass in individuals living with obesity and on background therapy of a GLP-1 receptor agonist (GLP-1 RA). The results from this trial will inform the development of SRK-439, a novel investigational selective myostatin inhibitor optimized for the treatment of cardiometabolic disorders, including obesity. The Company also announced new preclinical data from a head-to-head comparison of SRK-439 and an anti-activin receptor II (anti-ActRII) antibody, which demonstrate SRK-439’s potential as best in class in preserving lean mass in patients on GLP-1 RAs. This data will be presented by Mo Qatanani, Ph.D., Chief Scientific Officer, at Scholar Rock’s Investor Event, which begins today at 8:30 a.m. ET and is being held in New York City. “We are thrilled to have initiated the EMBRAZE clinical trial ahead of schedule and to share new data from our SRK-439 program, which we believe further support our hypothesis that selective latent myostatin inhibition has advantages over less selective approaches to safely and effectively maintain lean muscle mass,” said Jay Backstrom, M.D., MPH, President and Chief Executive Officer at Scholar Rock. “Selectivity is key in mitigating potential safety concerns for this patient population and we look forward to sharing additional preclinical data at the American Diabetes Association 84th Scientific Sessions in June to support the best-in-class potential of SRK-439.” New SRK-439 Data For the head-to-head preclinical research study, the Company generated and tested an anti-ActRII antibody (a murine equivalent of bimagrumab), along with a murine equivalent of SRK-439 in a weight-stable diet induced obesity (DIO) mouse model. Mice were given either semaglutide (0.04mg/kg, daily) with an IgG control antibody (weekly, 20mg/kg) or semaglutide (0.04mg/kg, daily) in combination with weekly injections of either SRK-439 (0.3-10mg/kg) or of the anti-ActRII antibody (0.3-20mg/kg). Quantitative nuclear magnetic resonance (qNMR) was used to analyze change in lean mass after four weeks of treatment. Lean mass differences were significant in all doses of SRK-439 tested, supporting the hypothesis that SRK-439 could be an important therapy to aid in lean mass preservation and is suitable for subcutaneous dosing in a population of adults with obesity. SRK-439 attenuated the GLP-1 RA-driven lean mass loss in combination with semaglutide at a dose as low as 0.3 mg/kg (8.3% lean mass loss from baseline). Maximal effects observed at all doses over 1 mg/kg (4.2% lean mass loss from baseline at 10mg/kg), as compared to an IgG control + semaglutide (14.1% lean mass loss from baseline). Superiority to anti-ActRII antibody was shown in all equivalent doses tested: 3 mg/kg: -4.7% SRK-439 vs. -12.0% for anti-ActRII 1 mg/kg: -5.0% SRK-439 vs. -12.6% for anti-ActRII 0.3 mg/kg: -8.3% SRK-439 vs. -15.4% for anti-ActRII Equivalent lean mass preservation was seen at the highest dose tested for both drugs; 10 mg/kg SRK-439 (-4.2%) and 20 mg/kg anti-ActRII (-4.3%). “The data from this head-to-head comparison show that selectively inhibiting myostatin alone is sufficient to preserve lean mass on a background of GLP-1 RA, in preclinical models. Combined with the positive data observed at low doses of SRK-439, we believe that our selective myostatin approach is the right potential solution to preserve lean muscle mass while avoiding the potential off-target effects observed in less selective programs for this indication. We view this as strong evidence that SRK-439 could have a more favorable benefit/risk profile,” said Mo Qatanani, Ph.D., Chief Scientific Officer at Scholar Rock. Phase 2 EMBRAZE Trial Design Scholar Rock announced in January that the U.S. Food and Drug Administration cleared the Company’s Investigational New Drug (IND) application for EMBRAZE, a randomized, double-blind, placebo-controlled, Phase 2 proof-of-concept trial evaluating the efficacy, safety and pharmacokinetics of apitegromab in adults with a body mass index (BMI) of >27 (overweight) or a BMI of >30 (obese) and taking a GLP-1 RA (tirzepatide or semaglutide). The target enrollment of EMBRAZE is 100 subjects aged 18-65 who are overweight or obese without diabetes. As part of the study design, the treatment period is 24 weeks, and all subjects will receive a GLP-1 RA. In addition, all subjects will be randomized 1:1 to receive either apitegromab or placebo by intravenous (IV) infusion every four weeks during the 24-week treatment period. The primary endpoint is change from baseline at Week 24 in lean mass assessed by dual-energy X-ray absorptiometry. Secondary endpoints include additional weight loss measures, safety and tolerability, and pharmacokinetic outcomes. Exploratory endpoints at Weeks 24 and 32 include cardiometabolic parameters (e.g. HbA1c), body composition, and physical function. Primary data from EMBRAZE are expected in mid-2025 and will inform Scholar Rock’s development of SRK-439 towards an anticipated IND filing in 2025. The presentation from Scholar Rock’s Investor Day will be available in the Investors and Media section of Scholar Rock’s website. Live webcast of the event may be accessed by visiting the Investors & Media section of the Scholar Rock website at . An archived replay of the webcast will be available on the Company’s website for approximately 90 days following the presentations. About SRK-439 SRK-439 is a novel, preclinical, investigational myostatin inhibitor that has high in vitro affinity for pro- and latent myostatin and maintains myostatin specificity (i.e., no GDF11 or Activin-A binding), and is initially being developed for the treatment of cardiometabolic disorders, including obesity. Based on preclinical data, SRK-439 has the potential to support healthier weight management by preserving lean mass during weight loss. The efficacy and safety of SRK-439 have not been established and SRK-439 has not been approved for any use by the FDA or any other regulatory agency. About Apitegromab Apitegromab is an investigational fully human monoclonal antibody inhibiting myostatin activation by selectively binding the pro- and latent forms of myostatin in the skeletal muscle. It is the first muscle-targeted treatment candidate to demonstrate clinical proof-of-concept in spinal muscular atrophy (SMA). Myostatin, a member of the TGFβ superfamily of growth factors, is expressed primarily by skeletal muscle cells, and the absence of its gene is associated with an increase in muscle mass and strength in multiple animal species, including humans. Scholar Rock believes that its highly selective targeting of pro- and latent forms of myostatin with apitegromab may lead to a clinically meaningful improvement in motor function in patients with SMA. The U.S. Food and Drug Administration (FDA) has granted Fast Track, Orphan Drug and Rare Pediatric Disease designations, and the European Medicines Agency (EMA) has granted Priority Medicines (PRIME) and Orphan Medicinal Product designations, to apitegromab for the treatment of SMA. The efficacy and safety of apitegromab have not been established and apitegromab has not been approved for any use by the FDA or any other regulatory agency. About Scholar Rock Scholar Rock is a biopharmaceutical company that discovers, develops, and delivers life-changing therapies for people with serious diseases that have high unmet need. As a global leader in the biology of the transforming growth factor beta (TGFβ) superfamily of cell proteins and named for the visual resemblance of a scholar rock to protein structures, the clinical-stage company is focused on advancing innovative treatments where protein growth factors are fundamental. Over the past decade, Scholar Rock has created a pipeline with the potential to advance the standard of care for neuromuscular disease, cardiometabolic disorders, cancer, and other conditions where growth factor-targeted drugs can play a transformational role. Scholar Rock is the only company to show clinical proof-of-concept for a muscle-targeted treatment in spinal muscular atrophy (SMA). This commitment to unlocking fundamentally different therapeutic approaches is powered by broad application of a proprietary platform, which has developed novel monoclonal antibodies to modulate protein growth factors with extraordinary selectivity. By harnessing cutting-edge science in disease spaces that are historically under-addressed through traditional therapies, Scholar Rock works every day to create new possibilities for patients. Learn more about our approach at ScholarRock.com and follow @ScholarRock and on LinkedIn. Availability of Other Information About Scholar Rock Investors and others should note that we communicate with our investors and the public using our company website , including, but not limited to, company disclosures, investor presentations and FAQs, Securities and Exchange Commission filings, press releases, public conference call transcripts and webcast transcripts, as well as on Twitter and LinkedIn. The information that we post on our website or on Twitter or LinkedIn could be deemed to be material information. As a result, we encourage investors, the media and others interested to review the information that we post there on a regular basis. The contents of our website or social media shall not be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended. Scholar Rock® is a registered trademark of Scholar Rock, Inc. Forward-Looking Statements This press release contains "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding Scholar Rock’s future expectations, plans and prospects, including without limitation, Scholar Rock’s expectations regarding its growth, strategy, progress and timing of its clinical trials for apitegromab and its preclinical programs, including SRK-439, and indication selection and development timing, including the therapeutic potential, clinical benefits and safety thereof, expectations regarding timing, success and data announcements of current ongoing preclinical and clinical trials, the ability of any product candidate to perform in humans in a manner consistent with earlier nonclinical, preclinical or clinical trial data, and the potential of its product candidates and proprietary platform. The use of words such as “may,” “might,” “could,” “will,” “should,” “expect,” “plan,” “anticipate,” “believe,” “estimate,” “project,” “intend,” “future,” “potential,” or “continue,” and other similar expressions are intended to identify such forward-looking statements. All such forward-looking statements are based on management's current expectations of future events and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in or implied by such forward-looking statements. These risks and uncertainties include, without limitation, that preclinical and clinical data, including the results from the Phase 2a clinical trial of apitegromab, or its preclinical data with respect to SRK-439, are not predictive of, may be inconsistent with, or more favorable than, data generated from future or ongoing clinical trials of the same product candidates, including, without limitation, the Phase 3 clinical trial of apitegromab in SMA or the Phase 2a EMBRAZE clinical trial; Scholar Rock’s ability to provide the financial support, resources and expertise necessary to identify and develop product candidates on the expected timeline; the data generated from Scholar Rock’s nonclinical and preclinical studies and clinical trials; information provided or decisions made by regulatory authorities; competition from third parties that are developing products for similar uses; Scholar Rock’s ability to obtain, maintain and protect its intellectual property; Scholar Rock’s dependence on third parties for development and manufacture of product candidates including, without limitation, to supply any clinical trials; and Scholar Rock’s ability to manage expenses and to obtain additional funding when needed to support its business activities and establish and maintain strategic business alliances and new business initiatives; as well as those risks more fully discussed in the section entitled "Risk Factors" in Scholar Rock’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2024, as well as discussions of potential risks, uncertainties, and other important factors in Scholar Rock’s subsequent filings with the Securities and Exchange Commission. Any forward-looking statements represent Scholar Rock’s views only as of today and should not be relied upon as representing its views as of any subsequent date. All information in this press release is as of the date of the release, and Scholar Rock undertakes no duty to update this information unless required by law. View source version on businesswire.com: Contacts Scholar Rock: Investors Rushmie Nofsinger Scholar Rock rnofsinger@scholarrock.com ir@scholarrock.com 857-259-5573 Media Molly MacLeod Scholar Rock mmacleod@scholarrock.com media@scholarrock.com 802-579-5995 Source: Scholar Rock View this news release online at:

LEXINGTON, Mass., May 14, 2024 (GLOBE NEWSWIRE) -- Keros Therapeutics, Inc. (“Keros”) (Nasdaq: KROS), a clinical-stage biopharmaceutical company focused on developing and commercializing novel therapeutics to treat a wide range of patients with disorders that are linked to dysfunctional signaling of the transforming growth factor-beta (“TGF-ß”) family of proteins, today announced that five abstracts will be presented from the KER-050 (elritercept) program at the 29th Annual Congress of the European Hematology Association (“EHA”), to be held both virtually and in person from June 13 through 16, 2024. The following abstracts were posted to the EHA website on May 14, 2024, 10:00 a.m. Eastern time. Clinical Presentation “Durable clinical treatment with elritercept (KER-050) treatment: Findings from an ongoing Phase 2 trial in participants with lower-risk MDS” Abstract Code: s183Session Title: s450 Immune and targeted therapies in MDSSession Date and Time: June 14, 2024; 8:45 a.m. - 10:00 a.m. Eastern time “Activin A Inhibition by elritercept (KER-050) is associated with evidence of cardiovascular benefit: Translation of preclinical observations to humans with MDS” Abstract Code: p760Session Title: Poster sessionSession Date and Time: June 14, 2024; 12:00 p.m. - 1:00 p.m. Eastern time “Elritercept (KER-050) demonstrated potential to treat myelofibrosis and mitigate ruxolitinib-associated cytopenias in the Phase 2 RESTORE Trial” Abstract Code: s223Session Title: s423 Clinical advances in myelofibrosis and mastocytosisSession Date and Time: June 15, 2024; 5:30 a.m. – 6:45 a.m. Eastern time “Reduced ferritin and increased bone specific alkaline phosphatase in participants with lower-risk MDS treated with elritercept (KER-050) support potential to rebalance the osteohematopoietic niche” Abstract Code: s302Session Title: s438 Iron metabolism: From basics to the clinicSession Date and Time: June 15, 2024; 8:45 a.m. - 10:00 a.m. Eastern time Preclinical Presentation “RKER-050, a modified activin receptor type IIA ligand trap, rescued anemia and increased muscle mass and strength in a mouse model of myelofibrosis” Abstract Code: p1013Session Title: Poster sessionSession Date and Time: June 14, 2024; 12:00 p.m. - 1:00 p.m. Eastern time About KER-050 Keros’ lead product candidate, KER-050, is an engineered ligand trap comprised of a modified ligand-binding domain of the TGF-ß receptor known as activin receptor type IIA that is fused to the portion of the human antibody known as the Fc domain. KER-050 is being developed for the treatment of low blood cell counts, or cytopenias, including anemia and thrombocytopenia, in patients with myelodysplastic syndromes (“MDS”) and in patients with myelofibrosis. About Keros Therapeutics, Inc. Keros is a clinical-stage biopharmaceutical company focused on developing and commercializing novel therapeutics to treat a wide range of patients with disorders that are linked to dysfunctional signaling of the TGF-ß family of proteins. We are a leader in understanding the role of the TGF-ß family of proteins, which are master regulators of the growth, repair and maintenance of a number of tissues, including blood, bone, skeletal muscle, adipose and heart tissue. By leveraging this understanding, we have discovered and are developing protein therapeutics that have the potential to provide meaningful and potentially disease-modifying benefit to patients. Keros’ lead product candidate, KER-050 (elritercept), is being developed for the treatment of low blood cell counts, or cytopenias, including anemia and thrombocytopenia, in patients with MDS and in patients with myelofibrosis. Keros’ second product candidate, KER-012 (cibotercept), is being developed for the treatment of pulmonary arterial hypertension and for the treatment of cardiovascular disorders. Keros’ third product candidate, KER-065, is being developed for the treatment of obesity and for the treatment of neuromuscular diseases. Cautionary Note Regarding Forward-Looking Statements Statements contained in this press release regarding matters that are not historical facts are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Words such as “will” or similar expressions are intended to identify forward-looking statements. Examples of these forward-looking statements include statements concerning: Keros’ presentation plans for the upcoming EHA annual meeting. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. These risks and uncertainties include, among others: Keros’ limited operating history and historical losses; Keros’ ability to raise additional funding to complete the development and any commercialization of its product candidates; Keros’ dependence on the success of its product candidates, KER-050, KER-012 and KER-065; that Keros may be delayed in initiating, enrolling or completing any clinical trials; competition from third parties that are developing products for similar uses; Keros’ ability to obtain, maintain and protect its intellectual property; and Keros’ dependence on third parties in connection with manufacturing, clinical trials and preclinical studies. These and other risks are described more fully in Keros’ filings with the Securities and Exchange Commission (“SEC”), including the “Risk Factors” section of the Company’s Quarterly Report on Form 10-Q, filed with the SEC on May 8, 2024, and its other documents subsequently filed with or furnished to the SEC. All forward-looking statements contained in this press release speak only as of the date on which they were made. Except to the extent required by law, Keros undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made. Investor Contact: Justin Frantzjfrantz@kerostx.com 617-221-6042