Moleculin Biotech, Inc., provided a preliminary update on recent clinical activity and expected near term milestones across its clinical development pipeline in its quarterly filing with the Securities and Exchange Commission. Ongoing Clinical Trial Updates: Next Generation Anthracycline ? Annamycin: Annamycin is the Company's next-generation anthracycline that has been designed to be non-cardiotoxic (unlike currently prescribed anthracyclines) and has been shown in animal models to accumulate in the lungs at up to 30-fold the level of doxorubicin (a commonly prescribed anthracycline and the standard of care chemotherapy for advanced STS), as well as demonstrating the ability to avoid the multidrug resistance mechanisms that typically limit the efficacy of doxorubicin and other currently prescribed anthracyclines.

An independent expert evaluated the first 62 subjects in the Company's four clinical trials and confirmed that there are no signs of cardiotoxicity. In total 66 subjects (4 are yet to be reviewed) have been treated in the Company's clinical trials and none have shown any signs of cardiotoxicity. This includes 50 subjects treated over the lifetime maximum anthracycline dose set by the U.S. Food and Drug Administration (FDA).

Annamycin is currently in development for the treatment of both first line therapy and therapy for relapsed or refractory acute myeloid leukemia (AML), as well as, STS lung metastases (STS lung mets), and the Company believes the drug may have the potential to treat additional indications. AML: The Company is currently conducting its Phase 1B/2 clinical trial evaluating Annamycin in combination with Cytarabine (also known as "Ara-C" and for which the combination of Annamycin and Ara-C is referred to as AnnAraC) for the treatment of subjects with AML as both first line therapy and for subjects who are refractory to or relapsed after induction therapy (MB-106). clinicaltrialsregister.eu: EudraCT 2020-005493-10 or clinicaltrials.gov: NCT05319587.

The Company has not treated any first line subjects to date. MB-106 Phase 1B/2 clinical trial began dosing subjects in March 2023. Nine clinical sites in Poland and Italy have been activated for the MB-106 trial.

The Company is planning for a total of up to [eleven] sites in the European Union (EU). The median number of prior therapies for these 3 subjects in the first cohort was five (range of one to ten). One subject, who was 78 years of age at the time of the study initiation and enrolled after a single prior multi-year therapy, achieved a CR that has continued to be durable at approximately 8 months.

This subject has received a second course of treatment at the direction of the treating physician and as allowed per the protocol. The other 2 subjects were shown to have disease progression. On August 7, 2023, Moleculin successfully completed the second cohort at 230 mg/m2 of Annamycin in this combination study.

Four subjects were treated in this cohort, 1 is believed to be relapsed from one or more prior therapies and 3 are believed to be refractory from up to three prior therapies. One subject was replaced due to a Serious Adverse Event (SAE) experienced on Day 1 of dosing. The SAE was determined to be unrelated to Annamycin and definitively related to Cytarabine.

The Company, at the recommendation of the safety review committee, deemed the second cohort dose as safe and opened recruitment, including for both first line therapy and for subjects who are refractory to or relapsed after induction therapy, to the Phase 2 portion of the trial. The median number of prior therapies for the 3 evaluable subjects in the second cohort was two (range of one to three) and the median age was 67. One subject, who was 64 years of age at the time of enrollment into the study with one prior therapy, was preliminarily recorded as a CR with an incomplete recovery of the bone marrow, or CRi, per the protocol.

This has since been deemed a CR, which has shown to be durable for approximately three months, which has allowed this subject to proceed to a bone marrow transplant. The other 2 subjects were shown to have disease progression. Durability of CR's is confirmed by and repeat bone marrow aspirates (BMA's).

The total CRs in the Phase 1B portion of this combination trial represent 33% (n=6). Notably, these CRs are considered durable. The median age of these subjects was 66.

On October 2, 2023, Moleculin announced the initial subjects had been treated in the Phase 2 portion of MB-106. The data above is as reported by the investigation sites as of November 9, 2023. The Company has recruited, treated, and evaluated 3 subjects in the Phase 2 portion of the trial.

One subject has been evaluated and determined to be a [CR]. The Company will assess the durability in the near future. Another subject in the Phase 2 portion died from a stroke (deemed not be related to Annamycin) prior to being re-biopsied to determine disease status.

The third has undergone a re-biopsy which shows zero blasts in the marrow and that data is now being assessed by the investigator. This latest subject is not included in the chart above. The median age of the first two subjects is 69 years (range of 69 to 70) and the median number of prior therapies for these subjects is three (both are three).

Other subjects in the Phase 2 portion of the trial are in the process of screening and treatment. The Company intends to treat up to 21 subjects in this Phase 2 portion of the trial. The Company may recruit an additional 3 subjects depending on recruitment.

At the Company's rate of recruitment plus the addition of another three sites for the trial, Moleculin expects to complete recruitment by early 2024. The total CRs in both Phases to date in MB-106 represent 38% (n=8), and although sufficient time has not passed to assess durability for the latest of these CRs, the 2 earlier CRs have now shown durability. The median baseline bone marrow assessments for the 3 CRs was 74.2 (range of 20 to 80).