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FDA Fast Tracks SELLAS Life Sciences' CDK9 Inhibitor for Acute Myeloid Leukemia


SELLAS Life Sciences Group, Inc’s CDK9 inhibitor SLS009 is being evaluated in an ongoing Phase I/II study in combination with Venclexta and Vidaza for patients with relapsed or refractory acute myeloid leukemia.

Image credit: LASZLO | stock.adobe.com

Image credit: LASZLO | stock.adobe.com

The FDA has granted Fast Track Designation to SELLAS Life Sciences Group, Inc’s CDK9 inhibitor SLS009 for the treatment of patients with relapsed or refractory acute myeloid leukemia (AML). The regulatory action was based on safety and efficacy data for the drug, which is being evaluated in an ongoing Phase I/II study (NCT04588922) in combination with Venclexta (venetoclax) and Vidaza (azacytidine) for patients with AML.2

“Receiving fast track designation for SLS009 for relapsed or refractory AML, following the recent orphan drug designation for the same indication, underscores the potential for SLS009 and highlights the critical unmet need for patients with AML who face a poor prognosis due to the progressive nature of the disease,” said Angelos Stergiou, MD, ScD hc, president and chief executive officer of SELLAS Life Sciences Group, Inc., in a press release.1 “The initial positive topline Phase IIa data at the 45-mg (safety) dose level demonstrate that SLS009 in combination with venetoclax and azacitidine exhibits antileukemic effects with a favorable safety profile in AML patients resistant to venetoclax combination therapies.”

Among nine patients administered SLS009 in the trial’s safety cohort at a dose of 45 mg in combination with Venclexta and Vidaza, eight are still alive and six have continued on treatment. During follow-up that ranged from two to seven months in surviving patients, median overall survival had not yet been reached. Among the evaluable patients in the trial, seven of eight showed significant antileukemia effects, which was defined as having at least a 50% decrease in bone marrow blasts.

There have been no dose-limiting toxicities or significant safety signals observed to date with the therapy. In an open-label, single-arm, multicenter Phase I clinical trial, SLS009 monotherapy produced a durable complete response (CR) in one patient who had previously experienced treatment failure with Venclexta and Vidaza. Further, investigators did not observe minimal residual disease in the patient, who has survived at 16 months following initiation of treatment.

The trial enrolled patients with cytologically or histologically confirmed relapsed or refractory hematologic malignancies, which include AML, chronic lymphocytic leukemia, small lymphocytic lymphoma, and lymphoma.2

Enrollment criteria include being at least 18 years of age, at least one measurable or evaluable lesion by 2014 Lugano response criteria, and prior administration of at least two lines of systemic treatment. Patients enrolled in the Phase IIa AML combination cohort had to be relapsed or refractory to prior regimens that included Venclexta. Exclusion criteria included bulky disease of at least 10 cm and required receipt of cytoreductive chemotherapy, symptomatic central nervous system metastases or primary lymphoma, or severe cardiovascular disease within six months of enrollment.

The Phase IIa portion of the trial analyzed SLS009 is at doses of 45 mg and 60 mg, with both patient groups also administered Venclexta and Vidaza.1 Patients enrolled in the 60 mg dose cohort were randomly assigned to a fixed dose of 60 mg once weekly or a fixed dose of 30 mg twice weekly, with each group enrolling five to 10 patients.

The study’s primary endpoints include safety, tolerability, composite CR rate, and duration of response. The trial will also evaluate event-free survival, OS, pharmacokinetics, and pharmacodynamics.

“We have now also enrolled several patients in the ongoing 60-mg dose cohort,” Stergiou said in the release.1 “Our team is committed to advancing the development of SLS009 with the goal of providing effective solutions to patients in need of viable treatment options.”

SELLAS estimates that additional data from the 45-mg safety cohort and initial findings from the 60-mg cohort will be available in the first quarter of 2024.


  1. SELLAS Life Sciences receives FDA fast track designation for SLS009 for treatment of relapsed/refractory acute myeloid leukemia and provides updated data for phase 2a study of SLS009 in relapsed/refractory acute myeloid leukemia patients. News release. SELLAS Life Sciences Group, Inc. January 9, 2024. Accessed January 10, 2024. https://www.sellaslifesciences.com/investors/news/News-Details/2024/SELLAS-Life-Sciences-Receives-FDA-Fast-Track-Designation-for-SLS009-for-Treatment-of-RelapsedRefractory-Acute-Myeloid-Leukemia-and-Provides-Updated-Data-for-Phase-2a-Study-of-SLS009-in-RelapsedRefractory-Acute-Myeloid-Leukemia-Patients/default.aspx
  2. A study of GFH009 in patients with hematologic malignancies. ClinicalTrials.gov. Updated September 1, 2023. Accessed January 10, 2024. https://classic.clinicaltrials.gov/ct2/show/NCT04588922
  3. SELLAS announces positive initial topline phase 2a data of SLS009 in acute myeloid leukemia. News release. SELLAS. October 16, 2023. Accessed January 10, 2024. https://www.sellaslifesciences.com/investors/news/News-Details/2023/SELLAS-Announces-Positive-Initial-Topline-Phase-2a-Data-of-SLS009-in-Acute-Myeloid-Leukemia/default.aspx
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