Keros Therapeutics Presents Clinical Trial and Preclinical Study Results from its KER-050 Program and Preclinical Data from its ALK2 Inhibitor Program at the 63rd American Society of Hematology Annual Meeting and Exposition

• Keros Therapeutics will be hosting a conference call and webcast today, December 13, 2021, at 4:01 p.m. ET.

LEXINGTON, Mass., Dec. 13, 2021 (GLOBE NEWSWIRE) -- Keros Therapeutics, Inc. (“Keros”) (Nasdaq: KROS), a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel treatments for patients suffering from hematological and musculoskeletal disorders with high unmet medical need, today announced that it presented additional data from its ongoing Phase 2 clinical trial of KER-050 in patients with very low-, low-, or intermediate-risk myelodysplastic syndromes (“MDS”), as well as preclinical data on the differentiated mechanism of action of KER-050 and its activity in cytopenia models, at the 63rd American Society of Hematology (“ASH”) Annual Meeting and Exposition, held in person and virtually December 11 through 14, 2021. In addition, Keros announced preclinical data evaluating ALK2 inhibition as a potential treatment option for anemia of inflammation.

“We were pleased to present additional data from our ongoing Phase 2 clinical trial of KER-050 in MDS patients at this year’s ASH annual meeting,” said Jasbir S. Seehra, Ph.D., President and Chief Executive Officer of Keros. “We believe these data support the potential of KER-050 as a treatment for multilineage cytopenias in MDS by potentially targeting multiple stages of hematopoiesis. We are also pleased to have recently initiated dosing for Cohort 5 of the trial at 5.0 mg/kg of KER-050, to be administered once every four weeks for 12 weeks, following the Safety Review Committee recommendation for this trial.”

Clinical Presentation

• A Phase 2, Open-Label, Ascending Dose Study of KER-050 for the Treatment of Anemia in Patients with Very Low, Low, or Intermediate Risk Myelodysplastic Syndromes

This ongoing, open-label, two-part, multiple ascending dose Phase 2 clinical trial is evaluating KER-050 in participants with very low-, low-, or intermediate-risk MDS who either have or have not previously received treatment with an erythroid stimulating agent (“ESA”). Enrollment was balanced approximately one-to-one between patients that did not have ring sideroblasts (“non-RS”) and patients that have ring sideroblasts (“RS positive”). Patients received KER-050 subcutaneously every 28 days for up to four cycles during Part 1 of the trial, at the following dose levels: Cohort 1, 0.75 mg/kg; Cohort 2, 1.5 mg/kg; Cohort 3, 2.5 mg/kg; and Cohort 4, 3.75 mg/kg.

As of October 25, 2021 (the “data cut-off date”), 24 patients in Cohorts 1, 2, 3 and 4 had received at least one dose of KER-050. KER-050 was observed to be generally well-tolerated as of the data cut-off date. No drug-related serious adverse events or dose-limiting toxicities were reported. The most commonly reported treatment-emergent adverse events were nausea, fatigue, diarrhea and dyspnea, none of which were deemed related to study drug. Treatment-related adverse events were reported in four patients, which were mild or moderate in severity, and did not lead to dose modification or treatment discontinuation. No patients developed high-risk MDS or acute myeloid leukemia. Two patients withdrew from the trial prior to completing eight weeks of treatment with KER-050, one due to death deemed unrelated to study drug and one due to withdrawn patient consent.

16 patients in Cohorts 1, 2 and 3 had completed at least eight weeks of treatment and evaluation as of the data cut-off date (which we refer to as the “evaluable patients”). The 16 evaluable patients were comprised of four non-transfused (“NT”), three low transfusion burden (“LTB”) and nine high transfusion burden (“HTB”) patients. Of the 12 LTB and HTB patients, six were non-RS and six were RS positive.

As of the data cut-off date, 50% (n=8/16) of the evaluable patients, three of whom were non-RS and five of whom were RS positive, achieved an overall erythroid response, which is defined as meeting one of the following two endpoints:

• IWG 2006 Hematological improvement-erythroid (“HI-E”), which is defined as either:
  • a ≥ 1.5 g/dL increase in hemoglobin for eight weeks in LTB and NT patients; or
  • a reduction by ≥ 4 red blood cell (“RBC”) units transfused during any eight-week period during the trial, compared with the eight-week period prior to Cycle 1, Day 1 in HTB patients.
• Transfusion independence (“TI”) for at least eight weeks in patients who require ≥ 2 RBC units transfused at baseline.

Additional data from the evaluable patients in Cohorts 1, 2 and 3 of the trial, as of the data cut-off date, include:

• 43.8% (n=7/16) of the evaluable patients achieved HI-E over an eight-week period.
• 45.5% (n=5/11) of the transfused patients receiving ≥ 2 RBC units at baseline achieved TI for at least eight weeks.

In addition, the following pharmacodynamic data were observed:

• Reticulocyte increases observed in patients achieving HI-E or TI endpoints.
• Increases in serum soluble transferrin receptor and decreases in serum ferritin observed in patients achieving HI-E or TI endpoints.
• Increases in platelets observed in patients achieving HI-E or TI.

Together, these data demonstrate the effects of KER-050 on both erythropoiesis and thrombopoiesis and support the continued development of KER-050 as a potential treatment option for ineffective hematopoiesis in MDS.

Preclinical Presentations

• KER-050, an Inhibitor of TGF-β Superfamily Signaling, Promoted Thrombopoiesis and Reversed Immune Thrombocytopenia in a Mouse Model of Disease

Administration of a mouse research form of KER-050 (“RKER-050”) increased differentiation of early- and late-stage megakaryocyte precursors and increased platelet count:

• Healthy mice treated with a single 10 mg/kg dose of a research form of KER-050 (“RKER-050”) had a 100% increase in platelets 12 hours after administration compared to vehicle-treated mice (p