On June 4, 2025 Moleculin Biotech, Inc., (Nasdaq: MBRX) ("Moleculin" or the "Company"), a late-stage pharmaceutical company with a broad portfolio of drug candidates targeting hard-to-treat cancers and viruses,reported positive topline efficacy results from its completed U.S. Phase 1B/2 clinical trial evaluating Annamycin for the treatment of soft tissue sarcoma lung metastases ("STS lung mets") (MB-107) (Press release, Moleculin, JUN 4, 2025, View Source [SID1234653713]).
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The MB-107 trial was a multi-center, open-label, single-arm monotherapy study that in Phase 1B determined the Maximum Tolerable Dose and Recommended Phase 2 Dose ("MTD", "RP2D" respectively) and safety of Annamycin and in Phase 2 explored the efficacy of Annamycin as a single agent for the treatment of subjects with STS lung mets for which chemotherapy was considered appropriate. For more information about the MB-107 trial visit clinicaltrials.gov and reference identifier NCT04887298.
"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. 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," commented 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."
Topline Efficacy Results Summary
Clinical Benefit Rate ("CBR") was 59.4% (n=32), comprised of 18 subjects with stable disease and 1 subject with a partial response (no subjects achieved Complete Response or CR)
Progression Free Survival ("PFS") & Overall Survival ("OS"):
Dose and regimen optimized subjects demonstrated PFS of ~4 months and OS of ~20 months
Overall (N=36) Median PFS was 63 days, with a 95% Confidence Interval ("CI") between 43 and 105 days
Median OS was 411 days, with a 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) of 13.5 months exceeded typical results for 2nd line monotherapies (8-12 months)1
OS/PFS was higher (19.9 months/127 days) for subjects with fewer prior therapies ( 2) (n=7) and receiving doses of Annamycin 330 mg/m2 (the RP2D)
Results suggest overall disease control was better at 330 mg/m2, but once combined with Phase 1B data OS and PFS was the same as overall
Subjects achieving a Partial Response ("PR") or Stable Disease ("SD") with 2 cycles also experienced higher OS/PFS (19.7 months/122 days), demonstrating that achieving CBR from Annamycin resulted in better outcomes
No cardiotoxicity demonstrated in all subject data as noted by an independent Expert
Annamycin currently has Fast Track Status and Orphan Drug Designation from the FDA for the treatment of relapsed or refractory acute myeloid leukemia, in addition to Orphan Drug Designation for the treatment of soft tissue sarcoma. Furthermore, Annamycin has Orphan Drug Designation for the treatment of relapsed or refractory acute myeloid leukemia from the EMA.
On-Demand Webcast Details
An on-demand Virtual STS Lung Mets KOL Webcast to discuss the MB-107 data will be available for investors, analysts, and other interested parties on Thursday, June 5, 2025 beginning at 8:30 AM ET.
For the event, Walter Klemp, Chairman and Chief Executive Officer, and Dr. Paul Waymack, Senior Chief Medical Officer of Moleculin will be joined by Key Opinion Leaders: Mohamad Cherry, MD, Medical Director of Hematology at Atlantic Health System; Prof. Bernd Kasper, Sarcoma Unit of the Mannheim Cancer Center (MCC) at the Mannheim University Medical Center, University of Heidelberg; and Sant P. Chawla, MD, Director, Sarcoma Oncology Center, Director, Cancer Center of Southern California.
Interested participants and investors may access the on-demand video webcast on the Events page of the Investors section of the Moleculin website, moleculin.com. The webcast will be accessible for 90 days.
About STS Lung Mets
Soft tissue sarcoma is a type of cancer that originates in the soft tissues of the body, including muscles, tendons, fat, blood vessels and nerves. Lung metastases are a common occurrence in STS, and can impact overall survival. According to The American Cancer Society approximately 13,500 individuals, both adults and children, will be diagnosed with soft tissue sarcoma in 20252. Soft tissue sarcomas account for 1% of all adult cancers, 7% of cancers in children up to age 15, and 3% of cancers in children under the age of 14. The Soft Tissue Sarcoma Market was valued at USD 1.58 Billion in 2024, and is expected to reach USD 2.57 Billion by 2030, rising at a CAGR of 8.43%. OS for standard of care for metastatic STS has been estimated at 8-12 months and certain experimental targeted and cytotoxic therapies (as monotherapies or some in combination) have yielded OS of 13.4 months as second line therapy.3
MB-107 Study Design
In Phase 2, Annamycin was administered as an intravenous (IV) infusion over 2 hours on Day 1, followed by 20 days off (1 cycle = 21 days). Subjects visit the study site every 21 days (±3 days) at which time safety monitoring – including for adverse events (AEs), as well as a physical examination, laboratory evaluations (clinical chemistry, complete blood count), vital signs, weight measurements, Eastern Cooperative Oncology Group (ECOG) performance status, and electrocardiograms (ECGs) – is performed, followed by an IV infusion of study drug. Cardiac function is followed by echocardiogram (ECHO) scans at screening, at the end of the first two cycles and then following every other cycle thereafter, at the End of Treatment visit, and if feasible, during follow up at 6 months (±1 month) and 1 year (±1 month) after study drug discontinuation. As long as the Investigator considers that the benefits of treatment with Annamycin continue to outweigh the risks, treatment will continue every 21 days until tumor progression is observed or unacceptable toxicity occurs.
Tumor response is monitored every 6 weeks (±1 week) from Cycle 1 Day 1 during treatment, at the End of Treatment visit, and then every 3 months (±1 month) until disease progression using RECIST 1.1 criteria. Those subjects who leave the study after a maximum response is achieved and who do not start another therapy will be followed every 3 months (±1 month) for progression-free survival (PFS). If a subject receives further therapy after discontinuing from the study, they will be followed only for overall survival (OS) and if feasible, follow-up ECHO scans at 6 months (±1 month) and 1 year (±1 month) were conducted after study drug discontinuation.