8-K: Moleculin Biotech Reports Positive Topline Efficacy from Annamycin Phase 1B/2 Trial for Soft Tissue Sarcoma Lung Metastases

Moleculin Biotech, Inc. announced positive topline efficacy results from its completed U.S. Phase 1B/2 clinical trial (MB-107) evaluating Annamycin for the treatment of soft tissue sarcoma lung metastases, demonstrating promising survival rates and no cardiotoxicity.

Summary

• Moleculin Biotech, Inc. reported positive topline efficacy results from its completed U.S. Phase 1B/2 clinical trial (MB-107) evaluating Annamycin for the treatment of soft tissue sarcoma lung metastases (STS lung mets).
• The Clinical Benefit Rate (CBR) was 59.4% (n=32), comprising 18 subjects with stable disease and 1 subject with a partial response, with no subjects achieving Complete Response (CR).
• For dose and regimen optimized subjects, Progression Free Survival (PFS) was approximately 4 months and Overall Survival (OS) was approximately 20 months.
• Overall (N=36), the Median PFS was 63 days (95% Confidence Interval (CI) between 43 and 105 days), and Median OS was 411 days (95% CI between 241 and 583 days).
• In Phase 2 (N=17) at 330 mg/m2, Median PFS was 105 days and OS for all-comers (median 6 prior therapies) was 13.5 months, which exceeded typical results for 2nd line monotherapies (8-12 months).
• OS/PFS was higher (19.9 months/127 days) for subjects with fewer prior therapies (2) (n=7) receiving Annamycin at 330 mg/m2 (the Recommended Phase 2 Dose or RP2D).
• Subjects achieving a Partial Response (PR) or Stable Disease (SD) with 2 cycles also experienced higher OS/PFS (19.7 months/122 days), indicating that achieving CBR from Annamycin led to better outcomes.
• No cardiotoxicity was demonstrated in any subject data, as confirmed by an independent expert.

Sentiment

Score: 8

Explanation: The document reports positive topline efficacy results for Annamycin in STS lung metastases, with overall survival exceeding typical benchmarks for 2nd line monotherapies despite patients being heavily pre-treated. The absence of cardiotoxicity is a significant safety advantage. The company also highlights progress in AML. The primary concern is the explicit mention of the need for significant additional financing without current commitments, which introduces a financial risk.

Positives

• Annamycin demonstrated positive topline efficacy results in the MB-107 trial for soft tissue sarcoma lung metastases.
• The Clinical Benefit Rate (CBR) of 59.4% is encouraging, indicating disease control in a significant portion of patients.
• Annamycin showed better performance in 7th line treatment than would typically be expected even in 2nd line monotherapy.
• Median Overall Survival (OS) for all-comers in Phase 2 (13.5 months) exceeded typical results for 2nd line monotherapies (8-12 months), despite patients having a median of 6 prior therapies.
• Higher OS (19.9 months) and PFS (127 days) were observed in subjects with fewer prior therapies (2) receiving the Recommended Phase 2 Dose (RP2D) of 330 mg/m2.
• Achieving Clinical Benefit Rate (CBR) from Annamycin resulted in better outcomes, with OS of 19.7 months and PFS of 122 days.
• No cardiotoxicity was demonstrated in any subject data, which is a significant safety advantage for an anthracycline.
• Annamycin has Fast Track Status and Orphan Drug Designation from the FDA for relapsed or refractory acute myeloid leukemia (AML) and Orphan Drug Designation for soft tissue sarcoma.
• Annamycin also holds Orphan Drug Designation from the EMA for the treatment of relapsed or refractory acute myeloid leukemia.
• The company believes it has substantially de-risked the development pathway towards potential approval for Annamycin for AML following a successful Phase 1B/2 study (MB-106).

Negatives

• No subjects achieved a Complete Response (CR) in the trial.
• The overall (N=36) Median Progression Free Survival (PFS) was 63 days, which is relatively short.

Risks

• Moleculin will require significant additional financing to conduct its clinical trials as described in the press release.
• The company currently has no commitments for the necessary additional financing.
• The achievement of milestones described in the press release assumes the company's ability to secure such financing on a timely basis.
• Expectations reflected in forward-looking statements may prove to be materially different from the results expressed or implied by such statements.
• Forward-looking statements involve known and unknown risks, uncertainties, and other factors, including those discussed under Item 1A. Risk Factors in the company's most recently filed Form 10-K and updated from time to time in Form 10-Q filings and other public SEC filings.

Future Outlook

The company believes these positive results strongly support further evaluations of Annamycin for the treatment of STS lung mets and looks forward to exploring opportunities to potentially bring this important treatment option to patients. Additionally, the company believes it has substantially de-risked the development pathway towards a potential approval for Annamycin for the treatment of AML.

Management Comments

• "These positive topline results from MB-107 are incredibly encouraging. The impact Annamycin demonstrated on median overall survival, particularly with patients who received multiple prior chemotherapy regimens, exceeded expectations." Walter Klemp, Chairman and Chief Executive Officer of Moleculin.
• "Additionally, the improvement seen with PFS after two doses represents a real potential for Annamycin to provide a meaningful treatment option for the treatment of STS lung mets." Walter Klemp, Chairman and Chief Executive Officer of Moleculin.
• "Looking ahead, we believe these results strongly support further evaluations of Annamycin for the treatment of STS lung mets and we look forward to exploring opportunities to potentially bring this important treatment option to patients." Walter Klemp, Chairman and Chief Executive Officer of Moleculin.

Industry Context

Soft tissue sarcoma is a significant cancer with approximately 13,500 new diagnoses annually in the U.S., and lung metastases are a common and impactful complication. The market for STS treatment was valued at $1.58 billion in 2024 and is projected to grow to $2.57 billion by 2030, indicating a substantial and growing need for effective therapies. Annamycin's ability to exceed typical 2nd line monotherapy OS results, especially in heavily pre-treated patients, positions it as a potentially valuable new option in a market seeking improved outcomes and better safety profiles.

Comparison to Industry Standards

• Median Overall Survival (OS) for all-comers in Phase 2 (13.5 months) exceeded typical results for 2nd line monotherapies (8-12 months), despite patients having a median of 6 prior therapies.
• OS for standard of care for metastatic STS has been estimated at 8-12 months.
• Certain experimental targeted and cytotoxic therapies (as monotherapies or some in combination) have yielded OS of 13.4 months as second line therapy; Annamycin's 13.5 months OS in heavily pre-treated patients (median 6 prior therapies) compares favorably to these 2nd line results.
• Annamycin's demonstrated lack of cardiotoxicity is a significant advantage compared to currently prescribed anthracyclines, which are known for cardiotoxic effects.

Stakeholder Impact

• Shareholders/Investors: Positive clinical trial results could increase investor confidence and potentially lead to share price appreciation. However, the explicit need for future financing introduces potential dilution risk.
• Patients: Annamycin offers a potential new, meaningful treatment option for soft tissue sarcoma lung metastases, especially for heavily pre-treated patients, and without the cardiotoxicity common to other anthracyclines.
• Medical Community: The positive efficacy and favorable safety profile (no cardiotoxicity) could lead to increased interest and potential adoption of Annamycin if it progresses to approval.

Next Steps

• Further evaluations of Annamycin for the treatment of STS lung mets.
• Exploring opportunities to potentially bring Annamycin to patients for STS lung mets.
• Continued development of Annamycin for relapsed or refractory acute myeloid leukemia (AML) in the pivotal Phase 3 MIRACLE trial (MB-108).
• Continued development of WP1066, an Immune/Transcription Modulator, targeting brain tumors, pancreatic, and other cancers.
• Continued development of a portfolio of antimetabolites, including WP1122, for the potential treatment of pathogenic viruses and certain cancer indications.
• An on-demand Virtual STS Lung Mets KOL Webcast will be available for investors, analysts, and other interested parties on Thursday, June 5, 2025, beginning at 8:30 AM ET.

Key Dates

Recommendation

Keywords

Moleculin Biotech, MBRX, Annamycin, Soft Tissue Sarcoma, STS lung metastases, clinical trial, Phase 1B/2, oncology, cancer treatment, drug development, Orphan Drug Designation, Fast Track Status, acute myeloid leukemia, AML, chemotherapy, pharmaceutical