Moleculin Announces Abstract Accepted for Poster Presentation at the 2026 ASCO Annual Meeting

Moleculin Biotech, Inc. , (Nasdaq: MBRX) (“Moleculin” or the “Company”), today announced that an abstract highlighting data on its lead drug candidate, annamycin, has been accepted for poster presentation at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting , taking place May 29 – June 2, 2026, in Chicago, Illinois.

The abstract, titled “Cardiac safety of L-annamycin at high cumulative anthracycline exposure: Pooled analysis,” will be presented in a poster session focused on Symptom Science and Palliative Care.

Presentation Details:

Session Type: Poster Session - Symptom Science and Palliative Care

Presentation Date and Time: May 30, 2026, 1:30 PM – 4:30 PM CDT

Location: Poster Board #8

The abstract presents a pooled analysis evaluating the cardiac safety profile of annamycin in patients with high cumulative exposure to anthracyclines, an important consideration given the known risk of cardiotoxicity associated with this class of chemotherapeutic agents.

“We are pleased to have this abstract accepted for presentation at ASCO, one of the most prestigious oncology conferences globally,” said Walter Klemp, Chairman and CEO of Moleculin. “These data further support the potential of annamycin as a differentiated anthracycline with a favorable cardiac safety profile, even at higher cumulative exposure levels. We look forward to sharing these findings with the oncology community.”

The ASCO Annual Meeting is one of the largest and most influential gatherings of oncology professionals worldwide, featuring cutting-edge research and advances in cancer treatment. For more information, please visit asco.org .

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 next-generation 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 Phase 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 www.moleculin.com 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 expected timing and results of the 45-subject interim data unblinding in the MIRACLE trial, the anticipated clinical milestones set forth above, and the potential efficacy and safety of Annamycin and AnnAraC in R/R AML and other indications. 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