SELLAS Life Sciences Group is advancing its highly selective CDK9 inhibitor SLS009 (tambiciclib) across multiple hematologic malignancies, with new preclinical data demonstrating statistically significant survival benefits in T-cell prolymphocytic leukemia and ongoing Phase 2 clinical trials in relapsed/refractory acute myeloid leukemia.
Breakthrough Results in T-Cell Prolymphocytic Leukemia
The company will present compelling preclinical efficacy data at the European Society for Medical Oncology (ESMO) Congress 2025 in Berlin, showcasing SLS009's performance in an in vivo patient-derived xenograft (PDX) model of relapsed/refractory T-PLL. The model successfully reproduced key human clinicopathological features of this aggressive leukemia.
In the study, SLS009 demonstrated meaningful single-agent activity, prolonging overall survival to 7.4 weeks compared to venetoclax alone at 4.4 weeks—a statistically significant difference (p<0.05). When combined with the BCL2 inhibitor venetoclax, the survival benefit extended to 7.9 weeks. Notably, SLS009 achieved superior control of circulating T-PLL cells in peripheral blood relative to other treatments, while the combination regimen maintained favorable tolerability.
"These results are highly encouraging and provide important preclinical evidence that selective CDK9 inhibition with SLS009 may play a critical role in the treatment of T-PLL, an aggressive leukemia with very limited treatment options," said Dr. Dragan Cicic, Senior Vice President and Chief Development Officer at SELLAS.
Clinical Translation and Model Validation
The research team, led by Dr. Francisco Vega from the University of Texas MD Anderson Cancer Center, developed a robust T-PLL patient-derived xenograft model that closely mirrors human disease behavior and progression. This breakthrough enables more rapid clinical translation by allowing evaluation of novel therapies without waiting years for early clinical trial results.
"The T-PLL patient-derived xenograft model we developed is highly robust and closely mirrors the behavior and progression of the disease in humans," Dr. Vega explained. "This breakthrough allows for more rapid and meaningful translation into the clinic, greatly accelerating drug development."
Phase 2 AML Trial Progress
SELLAS will also present Phase 2 data from its ongoing study evaluating SLS009 in combination with azacitidine and venetoclax for patients with relapsed/refractory AML with myelodysplastic syndrome-related changes (AML-MR) who have received prior venetoclax-based treatment. The presentation is scheduled for the 67th American Society of Hematology Annual Meeting in Orlando, Florida.
"Our participation at this year's ASH Annual Meeting underscores the growing body of evidence supporting SLS009 and its potential across hematologic malignancies," said Angelos Stergiou, President and Chief Executive Officer of SELLAS Life Sciences.
Mechanistic Insights
Additional preclinical research published in Blood describes SLS009's cytotoxic effects in AML cell lines harboring leukemia-driving mutations. The findings provide mechanistic support for SLS009's potential to address resistance to BCL-2 inhibition in AML, reinforcing its therapeutic relevance across multiple hematologic malignancies.
Previous data has shown SLS009 achieved high response rates in AML patients with unfavorable prognostic factors, including ASXL1 mutations commonly associated with poor prognosis in various myeloid diseases. The company positions SLS009 as potentially the first and best-in-class differentiated small molecule CDK9 inhibitor with reduced toxicity and increased potency compared to other CDK9 inhibitors.
