Presentation of data on Romacyclib (RVU120) and Dapolsertib (MEN1703) atthe 2025 Annual Meeting of the American Society of Hematology (ASH)

The Management Board of Ryvu Therapeutics S.A., headquartered in Kraków(the "Company" or "Ryvu"), announces that the Company will present thelatest data on romacyclib (RVU120) and dapolsertib (MEN1703) during the2025 Annual Meeting of the American Society of Hematology (ASH), whichwill take place on December 6-10, 2025, in Orlando, USA.

Details on the abstracts, which were submitted on July 31, 2025, are asfollows:

Abstract Title: Preliminary results from RIVER-81, a phase 2 study ofromaciclib (RVU120) + venetoclax in patients with acute myeloid leukemiafailing first-line venetoclax + hypomethylating agent (HMA)

Session name: 616. Acute myeloid leukemias: Investigational drug andcellular therapies: Poster 2

Session date and time:December 7, 6:00-8:00 PM EST

Poster number: 3424

The Phase II RIVER-81 study evaluates the combination of romaciclib(RVU120), a selective CDK8/CDK19 inhibitor, with venetoclax (VEN) inpatients with relapsed or refractory AML following frontline VEN+HMAtherapy. As of July 11, 2025, 48 patients with relapsed/refractory AMLafter VEN+HMA failure were treated in the ongoing RIVER-81 study. Nodose-limiting toxicities were observed up to romaciclib 200 mg QDcombined with venetoclax 400 mg QD, supporting favorable tolerabilityacross dose levels. Pharmacokinetic analyses confirmed dose-proportionalexposure, andpharmacodynamic assessments demonstrated robust inhibitionof STAT5 phosphorylation, consistent with on-target CDK8/19 activity.The most common adverse events were low-grade gastrointestinal symptoms,anemia, febrile neutropenia, and pneumonia. Among 28 evaluable patients,composite complete remission (CR + CRi) rates were 23% in Stage 1 ofPart 2 and 43% among treated patients in Cohort 4, with several ongoingdurable responses. In Cohort 6, two patients were evaluable, with oneachieving a CRi and the other patient achieving a substantial blastreduction. Fiveofeight responding patients remain on therapy, withdurations ranging from 0.6 to 7 months. Early efficacy signals suggestromaciclib may restore sensitivity to venetoclax in resistant AML.Thesefindings support continued enrollment and further evaluation ofromaciclib + VEN as a potential therapeutic option for patients withpoor-prognosis AML.

Abstract Title:An open-label, phase I/II clinical trial of wromaciclib(RVU120) as monotherapy andincombination with ruxolitinib in patientswith intermediate or high-risk, primary or secondary myelofibrosis(POTAMI-61)

Session name: 634. Myeloproliferative syndromes: Clinical andepidemiological: Poster 1

Session date and time:December 6, 5:30-7:30 PM EST

Poster number: 2045

The Phase II POTAMI-61 study evaluates romaciclib (RVU120), a selectiveCDK8/19 inhibitor, asmonotherapy and in combination with ruxolitinib(RUX) in patients with myelofibrosis (MF) whohave failed or shownsuboptimal response to JAK inhibitor therapy. As of July 25, 2025, 23patients were enrolled in Part A (12 monotherapy, 11 combination), withenrollment in Part B ongoing. Romaciclib was administered in 21-daycycles, and treatment was generally well tolerated; the most commonadverse events were grade 1-2 nausea (52%) and vomiting (43%). Grade 3events included anemia, thrombocytopenia, nausea, vomiting, urinarytract infection, and fatigue, each reported in3patients. Among fourevaluable patients, one achieved spleen volume reduction (SVR) 20%at24weeks, three showed some degree of SVR, and two achieved >50%reduction in total symptom score (TSS). One patient demonstratedcomplete symptom resolution, and another achieved improvement in bonemarrow fibrosis after 12 weeks. Pharmacokinetic results confirmedexpected exposure and no drug-drug interaction between romaciclib andRUX. These early data indicate that romaciclib is well tolerated andshow initial clinical activity, supporting continued evaluationofromaciclib as a potential therapeutic option for patients with MF.

Abstract Title:REMARK: A phase II, open-label, multicenter study oforally administered romaciclib (RVU120) for the treatment of anemia inpatients with lower-risk myelodysplastic neoplasms (LR-MDS)

Session name: 637. Myelodysplastic syndromes: Clinical andEpidemiological: Poster 3

Session date and time:December 8, 6:00-8:00 PM EST

Poster number: 5649

The Phase II REMARK study evaluates romaciclib (RVU120), an oralCDK8/CDK19 inhibitor, in patients with lower-risk myelodysplasticneoplasms (LR-MDS), a disease characterized by anemia and limitedtreatment options. As of the data cutoff, 42 patients had initiatedtreatment, of whom 15 remained on therapy. Romaciclib was administeredat 150 mg every other day for 13 days in 21-day cycles, withan optionto escalate to 250 mg in non-responders or relapsing patients.Preliminary results demonstrated early signs of clinical activity,including one patient with high transfusion burden (8RBCunits/16weeks) who achieved a primary erythroid response (HI-E) per IWG 2018criteria after 24 weeks of treatment. This responder carried an SF3B1mutation and had previously failed three standard therapies (ESA,luspatercept, lenalidomide). No new safety signals were identified; themost frequent treatment-related adverse events were nausea, vomiting,asthenia, and decreased appetite. These AEs were predominantly lowgrade; however, they led to discontinuation in some patients. Ongoinganalyses aim to define further romaciclib's erythroid activity, optimaldosing, and molecular predictors of response in LR-MDS.

Abstract Title:An open-label, phase 2 study of dapolsertib (MEN1703,SEL24) as monotherapy andincombination with glofitamab in patientswith relapsed or refractory aggressive B-cell non-Hodgkin lymphoma

Session name: 627. Aggressive lymphomas: Targeted and pharmacologictherapies: Poster 3

Session date and time:December 8, 6:00-8:00 PM EST

Poster number: 5481

The Phase II JASPIS-01 study evaluates dapolsertib (MEN1703), a dualPIM/FLT3 kinase inhibitor, asmonotherapy and in combination with theCD20xCD3 bispecific antibody glofitamab in patients withrelapsed orrefractory (R/R) aggressive B-cell lymphomas who have received at least2 prior lines of therapy. Dapolsertib targets key oncogenic and survivalpathways, including MYC- and BCL6-associated signaling, and hasdemonstrated preclinical synergy with anti-CD20 antibodies. The studyaims to assess the safety, tolerability, and preliminary efficacy ofdapolsertib while exploring itspotential to overcome resistanceassociated with CD20 downregulation. In Part 1, patients areenrolledinto two groups: bispecific-nave patients receiving dapolsertib +glofitamab in dose-optimization cohorts, and heavily pretreated patientsreceiving dapolsertib monotherapy. Two dosing schedules are beingexplored - 125 mg (2 weeks on/1 week off) and 150 mg (1 week on/2 weeksoff) - to identify the optimal therapeutic window. Dose selection forPart 2 will be guided by the Data andSafety Monitoring Board, followingsafety review after 2 treatment cycles. As of July 11, 2025, enrollmentin Part 1 is ongoing in France, Poland, Spain, and the UK, withadditional site activations planned. This study represents the firstclinical evaluation of dapolsertib in B-cell lymphoma and seeks toestablish a foundation for novel combination strategies addressingresistance to CD20-targeted immunotherapies.

All abstracts are now available online and can be obtained from theconference site:

https://worldannualmeeting.com/ash/index.php

Disclaimer: This English language translation has been prepared solelyfor the convenience of English-speaking readers. Despite all the effortsdevoted to this translation, certain discrepancies, omissions orapproximations may exist. In case of any differences between the Polishand the English versions, the Polish version shall prevail. RyvuTherapeutics S.A., its representatives and employees decline allresponsibility in this regard.