FDA Grants Orphan Drug Designation to SLS009 for AML


SLS009 represents a promising solution for patients with acute myeloid leukemia, addressing a significant unmet medical need. Top-line data on the agent are expected by the end of the year.

  • SLS009 (GFH009) is currently under evaluation in a phase 2a study for patients with relapsed/refractory acute myeloid leukemia (AML).

  • Positive data from a phase 1 study support the orphan drug designation (ODD) of SLS009.

  • ODD provides significant advantages to drug developers, including assistance in the development process, exemptions from certain fees, 7 years of marketing exclusivity, and more.

The FDA has granted an ODD to SLS009 for the treatment of patients with acute myeloid leukemia (AML), according to SELLAS Life Sciences Group, Inc.1

Leukemia: © Dr_Microbe - stock.adobe.com

Leukemia: © Dr_Microbe - stock.adobe.com

SLS009 is a novel, highly selective CDK9 inhibitor, currently under investigation in an open-label, single-arm, multicenter, phase 2a study (NCT04588922) for patients with relapsed or refractory AML.

The basis of this ODD is supported by findings from the phase 1 study (NCT04588922) which evaluated SLS009 in this patient population and showed that all the key end points of the study were met, including antitumor activity of up to 77.3% bone marrow blast reduction, and durable complete remission with no minimal residual disease.

Findings also showed desired 24 hours > IC90 peripheral blood concentrations after the first infusion, with IC90 concentrations resulting in up to 97% cancer cell killed, desired levels of MCL1 and MYC suppression in peripheral blood was achieved, and a decrease in MCL1 or MYC was seen in 97% of the patients who were evaluated.

For safety, there were no dose-limiting toxicities or higher grade non-hematologic toxicities observed. However, there were some hematologic toxicities which were difficult to determine in patients with hematologic cancers, but they were short in duration and reversible.

“We are honored to receive the ODD from the FDA. This designation underscores the potential of SLS009 to address a significant unmet medical need for patients with AML,” said Angelos Stergiou, MD, ScD hc, president and chief executive officer of SELLAS Life Sciences Group, Inc., in a press release.1

The primary end points being evaluated in the trial are safety, tolerability, and efficacy at 2 dose levels of SLS009. The first dose level is SLS009 once weekly at 45 mg, and the second is the recommended phase 2 dose, determined to be 60 mg in combination with azacitidine and venetoclax (Venclexta).2

Patients eligible for enrollment are those with cytological or histologically confirmed relapsed or refractory hematologic malignancies, including AML, chronic lymphocytic leukemia and small lymphocytic lymphoma, and lymphoma who have total bilirubin ≤ 1.5 × upper limit of normal (ULN), amylase ≤1.5 × ULN, and electrolytes and uric acid levels that are stable, which is judged by investigators for at least 3 days before the first dose the treatment.

Additionally, women of childbearing potential must agree to use highly effective methods of contraception during the duration of treatment and for 90 days following the last administration of SLS009. Male patients with a partner of childbearing potential must also use 2 highly effective methods of contraception during treatment and for an additional 90 days after the last administration of study drug.

Top-line data from the study are expected to be released by the end of this year.

“SLS009 is a novel and highly selective CDK9 inhibitor that has already shown a favorable safety profile, strong initial efficacy signals, and evidence of antitumor activity. With the support of this ODD, we look forward to accelerating SLS009 clinical development and bringing new hope to those suffering from this devastating disease,” added Stergiou, in the press release.1

  1. SELLAS receives FDA orphan drug designation for SLS009 for treatment of acute myeloid leukemia. News release. SELLAS Life Sciences Group, Inc. October 11, 2023. Accessed October 11, 2023. https://tinyurl.com/mvmfwydp
  2. A study of GFH009 in patients with hematologic malignancies. ClinicalTrials.gov. Updated September 1, 2023. Accessed October 11, 2023. https://tinyurl.com/459wkfwb
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