Liposomal Annamycin Shows Early Clinical Activity in Soft Tissue Sarcoma Lung Metastases


A phase 1b/2 study has shown an 80% clinical activity rate with liposomal annamycin as treatment of soft tissue sarcoma lung metastases.

Treatment with liposomal annamycin demonstrated 80% preliminary clinical activity as treatment of soft tissue sarcoma (STS) lung metastases, according to interim results from the phase 1b/2 clinical trial (NCT04887298) announced in a press release by Moleculin Biotech, Inc.1

“These interim data bolster our optimism about the potential for Annamycin to address the limitations with the current standard-of-care treatment options for STS lung metastases. 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," commented Walter Klemp, chairman, and chief executive officer, Moleculin, in the press release.

In the ongoing study, approximately 55 patients with STS lung metastases will receive 2-hour intravenous infusions of liposomal annamycin on day 1 of 21-day cycles followed by 20 days off treatment. The primary end point of the study is dose-limiting toxicity, and the secondary end points include efficacy per RECIST v1.1 and pharmacokinetics.2

To determine the maximum tolerated dose (MTD) of liposomal annamycin, up to 6 cohorts will include 3 patients each in the phase 1b portion of the study. Then, 25 patients will be enrolled to evaluate the recommended phase 2 dose of liposomal annamycin.

Interim data were available from the first 2 cohorts of patients with STS lung metastases. Of the 3 patients enrolled in cohort 1, all had stable disease (SD) through to cycle 6, and then 1 developed progressive disease and discontinued treatment.1

In cohort 2, 1 out of 3 patients had a partial response to liposomal annamycin, which was a 30% reduction in tumor size. The other 2 patients in the cohort had discontinued treatment due to 1 case of progressive disease and the other due to a reason unrelated to liposomal annamycin.

No dose-limiting toxicities have been reported in the study to date.

Currently, patients who have a pathologically confirmed diagnosis of STS and documented lung metastases and are ineligible to receive chemotherapy or curative resection; progressive and measurable disease; a life expectancy of at least 3 months; an ECOG performance status of ≤ 2; and adequate laboratory test results are being recruited at sites in California, Missouri, and New Jersey.

“We are also encouraged by the pace of recruitment so far in this trial. To have completed 2 full cohorts in just the first 4 months of the study with only one site open is faster than we would have expected, especially for a rare disease like STS lung metastases. And, with more sites joining the study before the end of the year, we believe there is the potential for this pace of recruitment to continue or even accelerate, said Klemp.

Liposomal annamycin has fast track status and orphan drug designations from the FDA for the treatment of STS lung metastases. The agent has also shown early promise in relapsed or refractory (R/R) acute myeloid leukemia (AML) and was granted an orphan drug designation for the treatment R/R AML.


1. Moleculin announces interim data in phase 1b/2 clinical trial of annamycin for the treatment of soft tissue sarcoma lung metastases. News release. October 19, 2021. Accessed October 19, 2021.

2. Study of liposomal annamycin for the treatment of subjects with soft-tissue Sarcomas (STS) with pulmonary metastases. Accessed October 19, 2021.

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