Cytarabine

Moleculin Biotech, Inc. INTERIM EFFICACY - N=45 INTENT TO TREAT (ITT) Both Annamycin dose arms outperformed control on the primary endpoint of complete remission (CR): 43% and 36% versus 12% — reported on a full intent-to-treat (ITT) basis with no patient exclusions Composite complete remission (CRc) reached 50% and 57% in the respective Annamycin arms versus 29% for control Enrollment in the MIRACLE trial continues with more than two-thirds (67 of 90 subjects) of Part A target as Company advances toward optimal dose selection HOUSTON, June 30, 2026 (GLOBE NEWSWIRE) -- Moleculin Biotech, Inc. , (Nasdaq: MBRX) (“Moleculin” or the “Company”), today announced positive preliminary unblinded efficacy results from the first 45 patients enrolled in Part A of the Company's pivotal Phase 2/3 MIRACLE trial, analyzed on a full intent-to-treat basis with no patient exclusions. Both Annamycin treatment arms demonstrated favorable efficacy trends compared with the control arm in patients with relapsed or refractory acute myeloid leukemia (R/R AML). The interim analysis demonstrated a clear efficacy advantage for both Annamycin treatment arms, 190 mg/m² plus HiDAC and 230 mg/m² plus HiDAC, over the HiDAC control arm. CR reached 43% and 36% in the respective Annamycin cohorts, compared with 12% for control, while CRc reached 50% and 57%, respectively, versus 29% for the control arm. The n=45 population contained 75.6% over 60 years of age, 55.6% 7+3 and 31.1% venetoclax regimens for first line (1L) therapies. Importantly, the remission rates for all three arms, including the control arm, reflect outcomes measured after only a single cycle of therapy, as specified by the MIRACLE protocol. The most commonly cited historical benchmarks in this setting, including the MIRROS and CLASSIC I studies, as well as Moleculin’s own MB-106 study, permitted multiple cycles of treatment. The Company therefore expected absolute remission rates for both the control and Annamycin arms in this single-cycle interim analysis to be lower than those reported in such multi-cycle datasets and believes the most meaningful comparison is the performance of the Annamycin arms relative to the concurrent, randomized control arm evaluated on the same single-cycle basis. "These interim Phase 2/3 results on such a challenging subject population represent a defining moment for Moleculin and, we believe, the strongest clinical validation of Annamycin we have seen to date," said Walter Klemp, Chairman and Chief Executive Officer of Moleculin. "To see both Annamycin dose arms meaningfully outperform the control arm across both the primary endpoint of complete remission as well as composite complete remission in patients with relapsed or refractory AML is an exceptional outcome. Importantly, these responses were achieved after only a single treatment cycle, providing what we believe is compelling evidence of Annamycin's anti-leukemic activity. We believe these results further validate Annamycin's differentiated pro strengthen our confidence as we advance the MIRACLE trial toward completion." "From a clinical perspective, these interim results are highly encouraging," Mr. Klemp continued. "Historically, achieving meaningful remission rates in relapsed or refractory AML has been exceptionally difficult, especially with subjects pretreated with venetoclax, which is why seeing both Annamycin treatment arms outperform the control arm across both efficacy endpoints is so noteworthy. The remission rates observed to date are particularly compelling when viewed in the context of outcomes historically reported for currently available therapies in this setting, especially given that patients in MIRACLE were evaluated after only a single treatment cycle. While cross-trial comparisons should be made with caution, these findings suggest the potential for a level of clinical activity that could meaningfully advance the treatment landscape for patients with relapsed or refractory AML. If these results continue to be observed as the trial progresses, Annamycin could represent an important new option for patients facing a disease with substantial unmet medical need." The interim review was conducted by the trial's Independent Data Monitoring Committee (iDMC). The committee unanimously concluded that for the primary efficacy endpoint of CR rates, although there was no statistical significance, there was a strong numeric trend suggesting that the experimental treatment arms (L-Annamycin at one of two doses plus high dose cytarabine) were superior to the placebo plus high dose cytarabine control arm. To that end, there was sufficient evidence of efficacy to support continuing the trial. The committee also concluded that the data did not support dropping either of the two experimental treatment arms since the efficacy data were too similar between these two treatment arms. The Company decided to accept the recommendation of the iDMC and continue with the MIRACLE trial as planned. The absence of formal statistical significance at this first interim analysis reflects the trial’s prespecified statistical design, not the strength of the data. As in most group-sequential studies, MIRACLE distributes its statistical “budget” across three planned analyses using a conservative O’Brien-Fleming spending function, which by design sets a very high bar for significance at an early interim look and reserves essentially the entire budget for the final analysis in the full population of approximately 282 subjects. Statistical significance was therefore neither expected nor required at this stage; the relevant question at an interim look is the direction and strength of the efficacy trend, which the iDMC found clearly favored both Annamycin arms over control. The trial remains fully powered, at 80%, to establish statistical significance at its planned final analysis (calculated to detect 20% vs. 35% CR for control vs. test, respectively). The MIRACLE trial is a pivotal Phase 2/3, multi-center, randomized, double-blind, placebo-controlled, adaptive design study of L-Annamycin for injection in combination with Cytarabine injection versus placebo in combination with Cytarabine injection as second line therapy for remission induction in adult subjects with R/R AML. Part A of the study is designed to identify the optimal Annamycin dose before advancing into the pivotal portion of the trial. Moleculin reported that 67 of the targeted 90 patients for Part A have been enrolled, representing approximately 74% of the planned enrollment. Following completion of Part A, the selected dose arm is expected to advance into Part B, where efficacy data from Part A will be carried forward into the pivotal analysis. Acute myeloid leukemia remains an area of significant unmet medical need, particularly among patients who relapse after frontline therapy. Moleculin believes the preliminary MIRACLE results further support Annamycin's potential to improve remission outcomes in this patient population and strengthen the rationale for the program's continued advancement toward registration. The interim results related to efficacy are final and other data remain subject to Part A final database review and readout. About Moleculin Biotech, Inc. Moleculin Biotech, Inc. is a Phase 3 clinical stage pharmaceutical company advancing a pipeline of therapeutic candidates addressing hard-to-treat tumors and viruses. The Company’s lead program, Annamycin (also known as naxtarubicin), is a highly efficacious and well tolerated anthracycline designed to avoid multidrug resistance mechanisms and to lack the cardiotoxicity common with currently prescribed anthracyclines. Annamycin is currently in development for the treatment of relapsed or refractory acute myeloid leukemia (AML) and soft tissue sarcoma (STS) lung metastases. The Company has begun the MIRACLE ( M olecul i n R /R AML A nnAraC Cl inical E valuation) Trial (MB-108), a pivotal, adaptive design, multi-center, randomized, double-blind, placebo-controlled Phase 2/3 trial evaluating Annamycin in combination with cytarabine, together referred to as AnnAraC (the combination of Annamycin and cytarabine, also referred to as “Ara-C”) for the treatment of relapsed or refractory acute myeloid leukemia. Following a successful Phase 1B/2 study (MB-106), with input from the FDA, the Company believes it has substantially de-risked the development pathway towards a potential approval for Annamycin for the treatment of AML. This study remains subject to appropriate future filings with potential additional feedback from the FDA and their foreign equivalents. Additionally, the Company is developing WP1066, an Immune/Transcription Modulator capable of inhibiting p-STAT3 and other oncogenic transcription factors while also stimulating a natural immune response, targeting brain tumors, pancreatic and other cancers. Moleculin also has in its pipeline a portfolio of antimetabolites, including WP1122 for the potential treatment of pathogenic viruses, as well as certain cancer indications. For more information about the Company, please visit and connect on X , LinkedIn and Facebook . Forward-Looking Statements Some of the statements in this release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995, which involve risks and uncertainties. Forward-looking statements in this press release include, without limitation, the potential efficacy and safety of Annamycin and AnnAraC in R/R AML and the expectation that interim efficacy trends observed in a limited patient population will be confirmed in the full study population (the interim results presented are based on a small sample size (n=45), have not achieved statistical significance, and may not be predictive of results from the completed trial). Moleculin will require significant additional financing, for which the Company has no commitments, in order to conduct its clinical trials as described in this press release, and the milestones described in this press release assume the Company’s ability to secure such financing on a timely basis. Although Moleculin believes that the expectations reflected in such forward-looking statements are reasonable as of the date made, expectations may prove to have been materially different from the results expressed or implied by such forward-looking statements. The Company relies on the reports of its expert with regard to the absence of cardiotoxicity. The dataset referenced in this press release is subject to the review of the data from future subjects in its current and future clinical trials and long-term follow-up with subjects in its current trials. Moleculin has attempted to identify forward-looking statements by terminology including ‘believes,’ ‘estimates,’ ‘anticipates,’ ‘expects,’ ‘plans,’ ‘projects,’ ‘intends,’ ‘potential,’ ‘may,’ ‘could,’ ‘might,’ ‘will,’ ‘should,’ ‘approximately’ or other words that convey uncertainty of future events or outcomes to identify these forward-looking statements. These statements are only predictions and involve known and unknown risks, uncertainties, and other factors, including those discussed under Item 1A. “Risk Factors” in our most recently filed Form 10-K filed with the Securities and Exchange Commission (SEC) and updated from time to time in our Form 10-Q filings and in our other public filings with the SEC. Any forward-looking statements contained in this release speak only as of its date. We undertake no obligation to update any forward-looking statements contained in this release to reflect events or circumstances occurring after its date or to reflect the occurrence of unanticipated events. Investor Contact: JTC Team, LLC Jenene Thomas (908) 824-0775 MBRX@jtcir.com Attachment Moleculin Biotech, Inc.

PRESS RELEASE AB SCIENCE REPORTS COMPLETION OF THE STEP 3 OF PHASE 1, EVALUATING THE COMBINATION OF AB8939 WITH VENETOCLAX FOR THE TREATMENT OF REFRACTORY OR RELAPSED ACUTE MYELOID LEUKEMIA THE COMBINATION OF AB8939 WITH VENETOCLAX GENERATED A 67% OVERALL RESPONSE RATE (ORR) AND A 100% DISEASE CONTROL RATE (DCR), WITH NO DOSE-LIMITING TOXICITIES (DLT) OBSERVED, IN A POOR-PROGNOSIS POPULATION WITH ADVERSE GENETICS TREATED IN THE SECOND - TO FOURTH-LINE RELAPSED OR REFRACTORY SETTING Paris, June 29, 2026, 8am CET AB Science SA (Euronext - FR0010557264 - AB) today provides an update on the Phase 1 study of the molecule AB8939 and the completion of Step 3, evaluating the combination of AB8939 + venetoclax in patients with acute myeloid leukemia (AML) associated with a very unfavorable genetic profile. Step 3 evaluated the combination of AB8939 plus venetoclax administered over a 14-day cycle. A total of six patients were treated across two dose levels of AB8939 (16 mg/m² and 21.3 mg/m²), each in combination with venetoclax. The combination was well-tolerated, with no dose-limiting toxicity (DLT) and no hematological toxicity observed at either dose level, allowing selection of the recommended Phase 2 dose (RP2D). Encouraging preliminary signs of efficacy were observed. Of the six patients treated, four achieved an objective response (one complete remission with incomplete hematologic recovery and three partial responses), corresponding to a 67% overall response rate (ORR). The two remaining patients achieved stable disease, resulting in a 100% disease control rate (CDR). These responses were achieved after a single cycle of treatment (14 days) in heavily pre-treated patients receiving second- to fourth-line therapy. Notably, two of the responding patients had previously progressed on venetoclax in combination with other chemotherapies. The patients treated all have very difficult to treat cytogenetic pro including complex karyotype, TP53 mutation, NRAS mutation, monosomy 5 and 7 and MECOM-rearrangement, that typically have a poor prognosis due to their aggressive disease course and treatment resistance This is a high response rate in a population where standard-of-care therapies achieve ORR of 10–30% in adverse-risk, multiply pre-treated AML (Gill H, et al. Cancer Med. 2020;9(10):3371-3382). Response after the first 14 days cycle in the six patients treated in Step 3 (AB8939 + venetoclax) Patient AB8939 dose Line of therapy Key adverse genetics Best response Patient 1 16 mg/m² 2nd RUNX1 and NRAS mutations CRi Patient 2 16 mg/m² 2nd MECOM-rearrangement, complex karyotype, monosomy 5 and 7 PR Patient 3 16 mg/m² 4th TP53 mutation, complex karyotype, monosomy 5 and 7 PR Patient 4 21.3 mg/m² 3rd TP53 mutation, complex karyotype, monosomy 5 and 7 PR Patient 5 21.3 mg/m² 2nd TP53 mutation SD Patient 6 21.3 mg/m² 2nd TP53 mutation (very high-risk MDS) SD Complete remission (CRc) is defined as CRc = CR + CRh + CRi + CRp CR=Bone marrow blasts 50% increase in marrow blasts over baseline (a minimum 15% increase is required in cases <30% blasts at baseline). This diversity of responsive patients appears to corroborate the mechanism of action of AB8939, which is capable of destabilizing microtubules while evading multi-drug resistance and also targeting cancer stem cells without eliminating non tumoral stem cells These results corroborate the positioning of AB8939 in patients with adverse genetics, complex karyotypes, TP53 mutations, NRAS and KRAS mutations, monosomy 5 and 7, and MECOM-rearrangement, which represents the highest unmet medical need. Nicholas J. Short, MD, Associate Professor and Co-Lead of the Section of Developmental Therapeutics, Department of Leukemia, MD Anderson Cancer Center, said, " This new data is very encouraging, particularly considering the very adverse risk pro this patient’s leukemia. These early efficacy and safety data suggest that AB8939 can be combined with venetoclax and could have significant activity in the highest-risk subtypes of AML. There is a strong interest in continuing the development of this combination in patients whose AML has high-risk features that are expected to lead to resistance to venetoclax + azacitidine. " Professor Olivier Hermine, MD, President of the Scientific Committee of AB Science and member of the Académie des Sciences in France, said, " There is a strong rationale to combine AB8939 and venetoclax as both molecules have low hematologic toxicity and complementary mode of actions. These first results are supportive of this rationale." With Step 3 completed, the next step is Step 4, evaluating the triple combination of AB8939 + venetoclax + azacitidine. About AB8939 AB8939 is a drug candidate that targets (i) cancer cells by destabilizing microtubules (essential for cell division) and (ii) cancer stem cells by inhibiting ALDH1A1 and ALDH2 (enzymes essential for maintaining their physiological state and survival). AB8939 has shown in vitro activity in Ara-C (cytarabine, which is one of the standards of care) resistant patient cell lines, including adverse genetic MECOM and TP53 mutations. Analysis of cell lines responsive to AB8939 showed that AB8939 is effective in cell lines with TP53 mutations, MECOM, and complex karyotypes, whereas ARAC and azacitidine are not effective. AB8939 increased survival and had an additive effect in combination with venetoclax (another standard of care) in vivo in a MECOM-grafted PDX mouse model. AB8939 increased survival and had an additive effect in combination with Vidaza (azacitidine, another standard of care) in vivo in the MECOM PDX#C1005 mouse model of leukemia. AB8939 eradicated Leukemia Cancer Stem Cells in vivo in a human PDX AML mouse model, which is compatible with targeting stem cells via ALDH. AB8939 is currently being evaluated in a Phase 1 clinical trial (study AB18001, NCT05211570) in patients with refractory and relapsed AML. The Phase 1 clinical trial of AB8939 has completed its first three steps. The first two steps determined the maximum tolerated dose (MTD) after 3 and 14 consecutive days of monotherapy. In both cases, the MTD was 21.3 mg/m². The third step, now completed, evaluated the combination of AB8939 and venetoclax. Six patients were treated across two dose levels (AB8939 14 days at a dose of 16 mg/m² + venetoclax 14 days, then AB8939 14 days at a dose of 21.3 mg/m² + venetoclax 14 days), with no dose-limiting toxicity observed, supporting selection of the recommended Phase 2 dose. The next step (Step 4) will evaluate the triple combination of AB8939 + venetoclax + azacitidine. Medical need in AML and AB8939 mechanism of action Although several drugs have been registered for AML, 70% of patients still relapse and die, creating a persistent unmet medical need for effective treatments. Acute myeloid leukemia remains the most lethal form of leukemia in humans. AML is a heterogeneous disease, and its outcome is highly dependent on genetic factors. TP53 mutation has a very poor prognosis, with a median overall survival (OS) of 5.5 months. NRAS and KRAS mutants have a poor prognosis, with a median OS of 12.1 months. MECOM also has a very poor prognosis in AML, with a median OS of 5.5 months in relapsed or refractory settings. The challenge in AML is the recurrence of tumors due to a combination of two factors: the resistance of cancer cells to chemotherapy and relapse due to the persistence of cancer stem cells. This challenge may be overcome by AB8939’s dual mechanism of action. First, AB8939 blocks the proliferation of leukemia cells through microtubule disruption. It is not subject to multi-drug resistance as it does not bind to PgP, which is responsible for efflux outside the cells, and is not degraded by myeloperoxidase. Second, AB8939 targets leukemia cancer stem cells by inhibiting ALDH and promotes bone marrow repopulation of normal progenitors. AB8939 + venetoclax combination There is a strong rationale to combine AB8939 with venetoclax Both molecules exhibit low hematologic toxicity. This combination is expected to be less toxic than azacitidine + venetoclax as first-line treatment for AML These molecules have different and complementary targets in cancer cells. There is an additive, even synergistic, efficacy potential for the combination, with three mechanisms of action in a single treatment. Venetoclax’s mechanism of action inhibits the BCL2 pathway, a protein that prevents apoptosis (programmed cell death) in cancer cells. BCL2 is a key factor in AML resistance, as it allows cancer cells to survive despite treatment AB8939 is pro-apoptotic, destabilizing microtubules, and would benefit from BCL2 inhibition to optimize apoptosis In addition, AB8939 specifically targets cancer stem cells by inhibiting ALDH, reducing resistance to treatment and limiting the risk of relapse Next steps Following completion of Step 3, the next step is to initiate Step 4, evaluating the triple combination of AB8939 + venetoclax + azacitidine, and to launch an expansion study in approximately 15 AML patients eligible for AB8939 + venetoclax at the appropriate dose. The expansion phase is expected to generate robust preliminary evidence of efficacy in the AML label, sufficient to support the clinical development plan and a beneficial partnership agreement. AB Science has started to discuss three possibilities for registration studies, which are not mutually exclusive, with the European Medicines Agency (EMA) and US Food and Drug Administration (FDA): AB8939 + venetoclax as first-line treatment, with aged patients and/or patients with adverse genetics (complex karyotypes, TP53 mutations, NRAS and KRAS mutations, monosomy 5 and 7, and MECOM-rearrangement) AB8939 + venetoclax as a second- or third-line treatment, in all patients or patients with adverse genetics AB8939 as a single agent in MECOM as a second or third-line treatment. Addressable market with AB8939 in relapsed/refractory AML Treatments for relapsed or refractory AML represent an estimated market size potential of greater than EUR 2 billion per annum. Region Incidence Case (1) % Relapse or Refractory (2,3) % Insured Patients (4) Drug Price (€) Market Size (per in Mio EUR) USA / CANADA 23,700 50% 90% 100,000 (5) 1 000 000 EUROPE 27,600 90% 60,000 770 000 APAC 27,800 30% 60,000 250 000 INDIA 11,000 30% 60,000 100,000 LATAM 7,200 30% 60,000 65 000 MENA 3,900 30% 60,000 35 000 TOTAL 90,200 2 200 000 EUROPE = EU27 + Norway + United Kingdom + Switzerland ; APAC = Australia, People’s Republic of China , Japan, New Zealand, Singapore, Taiwan ; LATAM = Argentina, Brazil, Chile, Colombia, Costa Rica, Mexico ; MENA = Algeria, Bahrain, Egypt, Israel, Kuwait, Morocco, Oman, Qatar, Saudi Arabia, Tunisia, United Arab Emirates (1) Zhou, Y et al. Global, regional, and national burden of acute myeloid leukemia, 1990–2021: a systematic analysis for the global burden of disease study 2021. Biomark Res 12, 101 (2024). (2) Ravandi F. Relapsed acute myeloid leukemia: Why is there no standard of care Best Pract Res Clin Haematol. 2013;26(3):253-9 (3) Walter RB et al. Resistance prediction in AML: analysis of 4601 patients from MRC/NCRI, HOVON/SAKK, SWOG and MD Anderson Cancer Center. Leukemia (2015) 29:312–20. . (4) Estimated (5) Choi M. et al. Costs per patient achieving remission with venetoclax-based combinations in newly diagnosed patients with acute myeloid leukemia ineligible for intensive induction chemotherapy. Journal of Managed Care & Specialty Pharmacy Volume 28, Number 9. Intellectual property AB8939 intellectual property rights in AML are secured until 2036 through a ‘composition of matter’ patent and potentially until 2041 with a 5 years extension. Two additional ‘second medical use’ patent applications have been filed to protect the use of AB8939 in the treatment of AML with specific chromosomal abnormalities. If these applications are accepted, the protection for AB8939 will be extended until 2044 and 2046 for these AML subpopulations. AB8939 has also received orphan drug designation for AML by both the EMA and FDA. This orphan drug designation confers 10 and 7 years of marketing exclusivity in Europe and the US, respectively, from the date of product registration. AB Science is the sole proprietary holder of AB8939 and its family of compounds. About AB Science Founded in 2001, AB Science is a pharmaceutical company specializing in the research, development and commercialization of protein kinase inhibitors (PKIs), a class of targeted proteins whose action are key in signaling pathways within cells. Our programs target only diseases with high unmet medical needs, often lethal with short term survival or rare or refractory to previous line of treatment. AB Science has developed a proprietary portfolio of molecules and the Company’s lead compound, masitinib, has already been registered for veterinary medicine and is developed in human medicine in oncology, neurological diseases, inflammatory diseases and viral diseases. The company is headquartered in Paris, France, and listed on Euronext Paris (ticker: AB). Further information is available on AB Science’s website: . Forward-looking Statements - AB Science This press release contains forward-looking statements. These statements are not historical facts. These statements include projections and estimates as well as the assumptions on which they are based, statements based on projects, objectives, intentions and expectations regarding financial results, events, operations, future services, product development and their potential or future performance. These forward-looking statements can often be identified by the words "expect", "anticipate", "believe", "intend", "estimate" or "plan" as well as other similar terms. While AB Science believes these forward-looking statements are reasonable, investors are cautioned that these forward-looking statements are subject to numerous risks and uncertainties that are difficult to predict and generally beyond the control of AB Science and which may imply that results and actual events significantly differ from those expressed, induced or anticipated in the forward-looking information and statements. These risks and uncertainties include the uncertainties related to product development of the Company which may not be successful or to the marketing authorizations granted by competent authorities or, more generally, any factors that may affect marketing capacity of the products developed by AB Science, as well as those developed or identified in the public documents published by AB Science. AB Science disclaims any obligation or undertaking to update the forward-looking information and statements, subject to the applicable regulations, in particular articles 223-1 et seq. of the AMF General Regulations. For additional information, please contact: AB Science Financial Communication & Media Relations investors@ab-science.com Attachment CP_AB8939_STEP3_VENG VF