Data on RVU120 presented at the 2025 European Hematology AssociationCongress

The Management Board of Ryvu Therapeutics S.A. with its registeredoffice in Krakow, Poland ("Company", "Ryvu") announces that the Companywill be presenting data on RVU120 at the 2025 European HematologyAssociation Congress (EHA), which takes place from June 12 to June 15 inMilan, Italy.

Details on the oral and poster presentations are described below. Thepresentation related to the presented posters is attached to this report.

# RVU120 in combination with venetoclax in AML

Poster PS1509: Preliminary results from RIVER-81, a Phase II study ofRVU120+VEN in patients with AML failing first-line VEN+HMA

Session date and time: 14 June 2025, 6:30 pm - 7:30 pm CEST

Preliminary results from the open-label RIVER-81 Phase II clinical studydemonstrate that RVU120, when combined with venetoclax (VEN), showspromising anti-leukemic activity in patients with relapsed or refractoryacute myeloid leukemia (r/r AML) who failed first-line VEN-basedtreatment. As of May 14, 2025, 43 patients had been treated, of which 27patients were evaluable for response across exploratory Parts 1 and 2.In total, 7 out of 27 evaluable patients (26%) achieved a completeremission with or without incomplete hematologic recovery (CR/CRi). Oneout of three evaluable patients from Cohort 2 achieved a completeremission (CR). 3 out of 13 evaluable patients from stage 1 of Part 2achieved a complete remission with incomplete count recovery (CRi),suggesting that RVU120 may help overcome VEN resistance. With optimizeddosing in Cohort 4 (150mg of RVU120 QD + 400mg VEN), the efficacyresults have further improved - the CR rate in the evaluable populationin this cohort was 50% (3 out of 6 patients. As of June 6, 2025, 4patients who have achieved a CR/CRi across all cohorts remain inremission on study treatment. The study continues enrollment in Cohort 6at a dose of 200mg of RVU120 QD + 400mg VEN, with the potential tomaximize the duration of response. The study supports furtherexploration of RVU120+VEN as a potential therapeutic strategy for AMLwith poor prognosis. The combination has been tolerated, with nausea asthe most common adverse event.

Poster PF415: Overcoming venetoclax resistance: synergistic potential ofRVU120, a CDK8/CDK19 inhibitor, in combination treatment

Session date and time: 13 June 2025, 6:30 pm - 7:30 pm CEST

RVU120 demonstrates strong synergy when combined with venetoclax (VEN)to overcome resistance to VEN in the treatment of AML. Preclinicalstudies reveal that RVU120+VEN effectively targets key VEN resistancepathways, including IL6/JAK/STAT3, TGF-, and PI3K/AKT/mTOR. Thecombination also retains efficacy in models of bone marrowstroma-mediated resistance, a common mechanism of therapy failure. Thesefindings support the ongoing Phase II RIVER-81 trial, exploringRVU120+VEN in patients with AML who have failed prior VEN-basedtreatments. This research underscores RVU120's potential to improvetreatment outcomes by overcoming venetoclax resistance in AML.

# RVU120 as a monotherapy and in combination with RUX in MF

Poster PF861: An Open-Label Clinical Trial of RVU120 as Monotherapy andin Combination with Ruxolitinib in Patients with Intermediate orHigh-Risk, Primary or Secondary Myelofibrosis (POTAMI-61)

Session date and time: 13 June 2025, 6:30 pm - 7:30 pm CEST

The open-label POTAMI-61 Phase II clinical trial evaluates RVU120 as amonotherapy and in combination with ruxolitinib (RUX) for patients withintermediate or high-risk myelofibrosis (MF). As of May 14, 2025, 21patients were treated, completing the enrollment in the exploratorypart. The median time on treatment was 10 weeks, with 8 patientscompleting at least 12 weeks of treatment, but no patient had met thefollow-up for the primary endpoint at 24 weeks due to insufficient timeon study. The ongoing trial is assessing spleen volume reduction,symptom burden, and safety over a 24-week period. Initial signs ofclinical activity were observed in selected patients: TSS improvementwas noted in 3 out of 4 patients at week 12; initial changes in spleensize reduction were observed in 4 out of 8 patients. Considering theearly read-out after only 12 weeks, the data are encouraging and warrantfurther exploration of RVU120 in patients with MF. RVU120 was found tobe tolerated by patients with MF, both when used as a single agent or incombination with RUX. The full week 24 data are anticipated in Q4 2025.

# RVU120 in MDS

Oral Presentation: RVU120 enhances erythroid potential in MDSpatient-derived cells: preclinical mechanistic insights into CDK8/CDK19inhibition and potential patient stratification

Session date and time: 12 June 2025, 5:00pm - 6:15pm CEST

Session title: s450 MDS cellular and molecular therapeutic targeting

RVU120 demonstrates significant potential in enhancing erythroiddifferentiation in MDS patient-derived cells confirmed by transcriptomicand functional analysis. Data show that RVU120 promotes erythropoiesisin CD34+ bone marrow cells derived from MDS patients, particularlybenefiting those with differentiation defects. Results from multiplepatient-derived samples indicate potential patient stratification basedon ASXL1 mutations. These findings support RVU120 as a promisingtherapeutic candidate in the REMARK Phase II clinical study in patientswith low-risk myelodysplastic syndromes (LR-MDS).

# RVU120 as a monotherapy in AML

Poster PF548: RIVER-52: A Multicenter, Open-Label Clinical Trial ofRVU120 in Patients with Relapsed or Refractory High-Risk MyelodysplasticSyndrome or Acute Myeloid Leukemia

Session date and time: 13 June 2025, 6:30 pm - 7:30 pm CEST

The open-label RIVER-52 Phase II clinical study evaluated RVU120monotherapy in patients with acute myeloid leukemia (AML) or relapsed orrefractory high-risk myelodysplastic syndrome (HR-MDS). As of May 14,2025, 39 patients received RVU120 (27 AML and 12 HR-MDS patients).RVU120 demonstrated a manageable safety profile, with gastrointestinaland infectious adverse events being the most common. Two patients, oneNPM1-mutated and one DNMT3A-mutated, showed more than 50% bone marrowblast reduction at their C2D13 disease assessment. A patient with HR-MDSachieved a CR but was lost to follow-up. Despite relevant blastreductions in some patients, no durable CRs were observed, andenrollment was suspended. The data collected will be used to support theRVU120 safety and efficacy database.

Posters are now available through the EHA Congress platform or throughthe Ryvu website: https://ryvu.com/publications.

Ryvu Management will host a webinar to discuss these data on Thursday,June 12 at 9:45 CEST:https://ryvu.clickmeeting.com/ryvu-eha-2025-results/register

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.