Form 8-K

8-K — Moleculin Biotech, Inc.

Accession: 0001437749-26-031280

Filed: 2026-09-28

Period: 2026-09-28

CIK: 0001659617

SIC: 2834 (PHARMACEUTICAL PREPARATIONS)

Item: Regulation FD Disclosure

Item: Financial Statements and Exhibits

Documents

8-K — mbrx20260925_8k.htm (Primary)

EX-99.1 — EXHIBIT 99.1 (ex_1019749.htm)

GRAPHIC (logo.jpg)

XML — IDEA: XBRL DOCUMENT (R1.htm)

8-K — FORM 8-K

8-K (Primary)

Filename: mbrx20260925_8k.htm · Sequence: 1

mbrx20260925_8k.htm

false

0001659617

2026-09-28

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): September 28, 2026

MOLECULIN BIOTECH, INC.

(Exact Name of Registrant as Specified in its Charter)

Delaware

001-37758

47-4671997

(State or Other Jurisdiction of

Incorporation or Organization)

(Commission File No.)

(I.R.S. Employer Identification

No.)

5300 Memorial Drive, Suite 950, Houston, TX 77007

(Address of principal executive offices and zip code)

(713) 300-5160

(Registrant’s telephone number, including area code)

(Former name or former address, if changed from last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐

Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐

Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐

Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐

Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-14(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol (s)

Name of each exchange on which registered

Common Stock, par value $.001 per share

MBRX

The NASDAQ Stock Market LLC

Item 7.01

Regulation FD Disclosure

On June 30, 2026, Moleculin Biotech, Inc. (the “Company”), issued a press release which announced the publication of a peer-reviewed analysis of the cardiac safety of Annamycin (also known as L-Annamycin or naxtarubicin) in Frontiers in Cardiovascular Medicine. The publication, titled “Cardiac safety of L-Annamycin: a pooled analysis of five clinical trials,” reports cardiac safety findings from 90 patients treated across five clinical trials in acute myeloid leukemia (AML) and metastatic soft tissue sarcoma (STS).

A copy of the press release is attached to this report as Exhibit 99.1 and is incorporated by reference herein.

The information contained in Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.1, is being furnished and shall not be “filed” for the purpose of the Securities Exchange Act of 1934, as amended (“Exchange Act”), nor shall it be incorporated by reference in any filing under the Exchange Act or the Securities Act of 1933, as amended (“Securities Act”), unless specifically identified therein as being incorporated by reference.

Item 9.01

Financial Statements and Exhibits.

(d)

Exhibits.

Exhibit

No.

Description

99.1

Press Release dated September 28, 2026

104

Cover page Interactive Data File (formatted as Inline XBRL document)

SIGNATURE

Pursuant to the requirements of the Securities and Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

MOLECULIN BIOTECH, INC.

Date:

September 28, 2026

By:

/s/ Jonathan P. Foster

Jonathan P. Foster

EX-99.1 — EXHIBIT 99.1

EX-99.1

Filename: ex_1019749.htm · Sequence: 2

ex_1019749.htm

Exhibit 99.1

Moleculin Announces Publication of Peer-Reviewed Cardiac Safety Analysis of Annamycin in Frontiers in Cardiovascular Medicine

–

Pooled analysis of five clinical trials found no clinical or subclinical evidence of cardiotoxicity at cumulative doses exceeding traditional anthracycline limits

–

Independent Cleveland Clinic cardio-oncology evaluation supports continued clinical development of Annamycin as a potentially safer anthracycline

HOUSTON, September 28, 2026 /PRNewswire/ -- Moleculin Biotech, Inc. (Nasdaq: MBRX) (“Moleculin” or the “Company”) today announced the publication of a peer-reviewed analysis of the cardiac safety of Annamycin (also known as L-Annamycin or naxtarubicin) in Frontiers in Cardiovascular Medicine. The publication, titled “Cardiac safety of L-Annamycin: a pooled analysis of five clinical trials,” reports cardiac safety findings from 90 patients treated across five clinical trials in acute myeloid leukemia (AML) and metastatic soft tissue sarcoma (STS).

The analysis was independently evaluated by a cardio-oncology laboratory at Cleveland Clinic and found no clinical or subclinical evidence of treatment-related cardiotoxicity, including at cumulative Annamycin exposures exceeding traditional lifetime limits for conventional anthracyclines.

“Publication of this comprehensive pooled analysis in a peer-reviewed cardiovascular medicine journal provides additional validation of the cardiac safety profile we have observed with Annamycin across our clinical development program,” said Walter Klemp, Chairman and Chief Executive Officer of Moleculin. “For decades, the clinical utility of anthracyclines has been limited by cumulative cardiotoxicity and associated lifetime dose limits. The absence of detectable cardiac toxicity in patients receiving cumulative doses of Annamycin beyond those traditional thresholds supports our continued development of Annamycin and its potential to address an important limitation of the anthracycline class.”

Pooled Analysis Evaluates Cardiac Safety Across Five Clinical Trials

The publication evaluated cardiac safety data from five sponsor- and investigator-initiated clinical trials, including three trials in AML and two trials in metastatic STS. Across the five studies, 90 patients received Annamycin, with paired echocardiographic data available for 78 patients.

Key findings from the pooled analysis include:

●

No significant change in cardiac function: Mean LVEF was 60.6% at baseline compared with 60.0% following treatment, with no statistically significant difference (p=0.84).

●

No relationship between cumulative dose and change in LVEF: The analysis found no association between cumulative Annamycin exposure and changes in LVEF.

●

No relationship between age and change in LVEF: Patient age was not associated with changes in LVEF.

●

No treatment-related cardiotoxicity identified: Serial ECGs, cardiac biomarkers including troponin I/T, and global longitudinal strain assessments showed no evidence of treatment-related cardiotoxicity.

●

High cumulative exposure: Patients received a median cumulative Annamycin dose of 660 mg/m², with findings observed despite cumulative exposures exceeding conventional anthracycline lifetime limits.

The authors concluded that Annamycin was not associated with clinical or subclinical evidence of cardiotoxicity at cumulative doses exceeding traditional anthracycline thresholds and that the findings support continued clinical evaluation of Annamycin as a potentially safer anthracycline platform.

Anthracyclines are among the most widely used and effective classes of cancer medicines, but their use can be limited by cumulative, dose-dependent cardiotoxicity. These cardiac risks can restrict treatment intensity, limit retreatment options and prevent some patients from receiving additional anthracycline therapy.

Annamycin is a fundamentally re-engineered anthracycline designed to maintain the antitumor activity of the anthracycline class while addressing the cardiotoxicity associated with conventional agents. Its liposomal formulation was developed to optimize tissue distribution and reduce cardiac exposure.

The newly published article builds upon previously presented clinical data demonstrating a lack of detectable cardiotoxicity with Annamycin despite cumulative exposure levels substantially exceeding conventional anthracycline limits. Moleculin previously reported that the pooled analysis included 90 patients across five completed clinical trials, with independent cardiac review conducted through the Cleveland Clinic Division of Cardiovascular Medicine.

Annamycin is currently being evaluated in Moleculin’s MIRACLE clinical development program for patients with relapsed or refractory AML.

About Moleculin Biotech, Inc.

Moleculin Biotech, Inc. is a Phase 2/3 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 (Moleculin R/R AML AnnAraC Clinical Evaluation) 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 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 potential efficacy and safety of Annamycin and AnnAraC in R/R AML, the potential immune-mediated mechanism of action of Annamycin, the relevance of preclinical findings in pancreatic cancer to the treatment of human disease, and the potential for Annamycin to be combined with other agents. 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

GRAPHIC

Filename: logo.jpg · Sequence: 7

Binary file (18313 bytes)

Download logo.jpg

XML — IDEA: XBRL DOCUMENT

XML

Filename: R1.htm · Sequence: 9

v3.26.3

Document And Entity Information

Sep. 28, 2026

Document Information [Line Items]

Entity, Registrant Name

MOLECULIN BIOTECH, INC.

Document, Type

8-K

Document, Period End Date

Sep. 28, 2026

Entity, Incorporation, State or Country Code

Entity, File Number

001-37758

Entity, Tax Identification Number

47-4671997

Entity, Address, Address Line One

5300 Memorial Drive, Suite 950

Entity, Address, City or Town

Houston

Entity, Address, State or Province

Entity, Address, Postal Zip Code

77007

City Area Code

713

Local Phone Number

300-5160

Written Communications

false

Soliciting Material

false

Pre-commencement Tender Offer

false

Pre-commencement Issuer Tender Offer

false

Entity, Emerging Growth Company

false

Title of 12(b) Security

Common Stock

Trading Symbol

MBRX

Security Exchange Name

NASDAQ

Amendment Flag

false

Entity, Central Index Key

0001659617

- Definition

Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

+ References

No definition available.

+ Details

Name:

dei_AmendmentFlag

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Area code of city

+ References

No definition available.

+ Details

Name:

dei_CityAreaCode

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:

dei_DocumentInformationLineItems

Namespace Prefix:

dei_

Data Type:

xbrli:stringItemType

Balance Type:

Period Type:

duration

- Definition

For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.

+ References

No definition available.

+ Details

Name:

dei_DocumentPeriodEndDate

Namespace Prefix:

dei_

Data Type:

xbrli:dateItemType

Balance Type:

Period Type:

duration

- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

+ References

No definition available.

+ Details

Name:

dei_DocumentType

Namespace Prefix:

dei_

Data Type:

dei:submissionTypeItemType

Balance Type:

Period Type:

duration

- Definition

Address Line 1 such as Attn, Building Name, Street Name

+ References

No definition available.

+ Details

Name:

dei_EntityAddressAddressLine1

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Name of the City or Town

+ References

No definition available.

+ Details

Name:

dei_EntityAddressCityOrTown

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Code for the postal or zip code

+ References

No definition available.

+ Details

Name:

dei_EntityAddressPostalZipCode

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Name of the state or province.

+ References

No definition available.

+ Details

Name:

dei_EntityAddressStateOrProvince

Namespace Prefix:

dei_

Data Type:

dei:stateOrProvinceItemType

Balance Type:

Period Type:

duration

- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityCentralIndexKey

Namespace Prefix:

dei_

Data Type:

dei:centralIndexKeyItemType

Balance Type:

Period Type:

duration

- Definition

Indicate if registrant meets the emerging growth company criteria.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityEmergingGrowthCompany

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

+ References

No definition available.

+ Details

Name:

dei_EntityFileNumber

Namespace Prefix:

dei_

Data Type:

dei:fileNumberItemType

Balance Type:

Period Type:

duration

- Definition

Two-character EDGAR code representing the state or country of incorporation.

+ References

No definition available.

+ Details

Name:

dei_EntityIncorporationStateCountryCode

Namespace Prefix:

dei_

Data Type:

dei:edgarStateCountryItemType

Balance Type:

Period Type:

duration

- Definition

The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityRegistrantName

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityTaxIdentificationNumber

Namespace Prefix:

dei_

Data Type:

dei:employerIdItemType

Balance Type:

Period Type:

duration

- Definition

Local phone number for entity.

+ References

No definition available.

+ Details

Name:

dei_LocalPhoneNumber

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 13e

-Subsection 4c

+ Details

Name:

dei_PreCommencementIssuerTenderOffer

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 14d

-Subsection 2b

+ Details

Name:

dei_PreCommencementTenderOffer

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Title of a 12(b) registered security.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b

+ Details

Name:

dei_Security12bTitle

Namespace Prefix:

dei_

Data Type:

dei:securityTitleItemType

Balance Type:

Period Type:

duration

- Definition

Name of the Exchange on which a security is registered.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection d1-1

+ Details

Name:

dei_SecurityExchangeName

Namespace Prefix:

dei_

Data Type:

dei:edgarExchangeCodeItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 14a

-Subsection 12

+ Details

Name:

dei_SolicitingMaterial

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Trading symbol of an instrument as listed on an exchange.

+ References

No definition available.

+ Details

Name:

dei_TradingSymbol

Namespace Prefix:

dei_

Data Type:

dei:tradingSymbolItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Securities Act

-Number 230

-Section 425

+ Details

Name:

dei_WrittenCommunications

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration