Shares of Sellas Life Sciences rose over 7% in premarket trading on Thursday as investors turned optimistic ahead of the company's Saturday presentation on new preclinical data for its experimental cancer drug SLS009 at the European Society for Medical Oncology Congress 2025 in Berlin.

Promising Data In Rare Leukemia 

Sellas said its selective CDK9 inhibitor, SLS009, showed significant activity in treating T-cell prolymphocytic leukemia (T-PLL), both as a standalone therapy and in combination with venetoclax. 

In a patient-derived xenograft model of relapsed or refractory T-PLL, SLS009 monotherapy extended survival to 7.4 weeks, while the combination reached 7.9 weeks, compared with 4.4 weeks for venetoclax alone, marking a statistically significant improvement. The company said both regimens also reduced circulating T-PLL cells more effectively and were well tolerated. 

Faster Clinical Translation

Dragan Cicic, Chief Development Officer at Sellas, said the findings provide“important preclinical evidence” that CDK9 inhibition may play a key role in addressing this aggressive and difficult-to-treat leukemia.

Francisco Vega of the University of Texas MD Anderson Cancer Center, the study's lead author, said the new T-PLL xenograft model“closely mirrors” the behavior and progression of the disease in humans. It allows for faster translation of promising preclinical data into the clinic.

Pipeline Expands Beyond Leukemia

SLS009 is one of Sellas' key oncology assets, alongside its lead WT1-targeting immunotherapy, GPS, licensed from Memorial Sloan Kettering Cancer Center. The company said both candidates are designed to address cancers with poor prognostic factors and limited treatment options.

Stocktwits Bulls Cheer Upcoming Presentation

On Stocktwits, retail sentiment for Sellas was 'extremely bullish' amid a 50% surge in 24-hour message volume.

One user cheered the global attention around the stock, noting strong overnight interest and hinting at excitement ahead of the company's planned Virtual R & D Day on Oct.29.

Another said they hoped Sellas would release both the new data and a buyout announcement at the same event, joking that such a move could send the stock straight to 125 a share.

Sellas' stock has more than doubled so far in 2025.

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