Annamycin Demonstrates Positive Clinical Activity for Soft Tissue Sarcoma Lung Metastases

The interim results of a phase 1b/2 trial showed that patients with soft tissue sarcoma and lung metastases who were treated with annamycin experienced positive clinical activity.

The use of annamycin to treat lung metastases in soft tissue sarcoma induced promising preliminary responses, according to a press release on the interim results of a phase 1b/2 study (NCT04887298) from drug developer Moleculin Biotech Inc.

Annamycin demonstrated a clinical activity rate of 80% that consisted of patients who achieved stable disease and or better. Moreover, investigators reported that no dose limiting toxicities have been observed.

“To witness the activity of annamycin in the treatment of STS lung metastases, even this early in a phase 1 trial, we believe is encouraging. Four of the 5 patients [who] have completed scans to date demonstrated a response to treatment, including 3 with extended and, in one case, continuing stable disease and one patient with a substantial (>30%) reduction in tumor size,” Walter Klemp, chairman and chief executive officer at Moleculin, said in a press release.

A total of 3 subjects will be enrolled into each of the 6 cohorts for phase 1b portion of the trial, until a maximum tolerated dose is identified. Investigators then plan to enroll 25 patients who will be treated with the recommended phase 2 dose in order to further evaluate the efficacy of annamycin.

Within the first cohort, investigators reported that 1 patient is currently in cycle 5 of treatment, with the expectation that they will continue onto cycle 6. Cycle 4 scans revealed that the patient achieved stable disease. After 6 cycles of treatment or 4.5 months, 1 patient discontinued due to progressive disease, although stable disease was maintained up until that cycle. After 1 cycle, an additional patient discontinued treatment, although stable disease was confirmed following the end of study scan; they discontinued as the time to cycle 2 was delayed longer than 6 weeks.

In the second cohort, 1 patient was still undergoing treatment in cycle 3, with a scan revealing a partial response after cycle 2. One patient discontinued because the scan after cycle 2 revealed progressive disease, and an additional patient discontinued for reasons unreleated to annamycin after 1 cycle.

Patients in phase 1b received annamycin intravenously over 2 hours on day 1 followed by 20 days off. Every 21 days, patients visited the study site and were examined for safety, laboratory evaluation, vital signs, and weight measurements. During each cycle, laboratory evaluation at 7 and 14 days were performed in order to monitor safety. Additionally, patients were given an echocardiogram at the end of the first 2 cycles and every other cycle, then during the 6-month and 1-year follow-ups.

Investigators monitored tumor response every 6 weeks beginning at cycle 1, day 1 to the end of treatment, and then every 3 months until disease progression. 

Annamycin has previously been granted a fast track designation by the FDA for the treatment of STS lung metastases. It is also currently in development for relapsed or refractory acute myeloid leukemia. 

“Ultimately, we believe annamycin has the potential to bring a new and effective treatment option to patients with a significant unmet need. With these data now in hand, we are cautiously optimistic as we begin patient enrollment and dosing in the next cohort,” Klemp concluded.


Moleculin announced interim data in phase 1b/2 clinical trial of annamycin for the treatment of soft tissue sarcoma lung metastases. News release. October 18, 2021. Accessed October 21, 2021.

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