SLS Stock Extends Rally To 4 Days: Jefferies Discloses New Stake, CEO Signals AML Database-Lock Preparations

A separate pediatric study delivered “striking” WT1 vaccine results, supporting GPS’s scientific rationale, the company's CEO said.

• Jefferies disclosed a new 200,459-share position in SLS worth nearly $3 million.
• Susquehanna boosted its holding more than 5x, while several other institutions added shares.
• Sellas is preparing for the database lock and advancing potential FDA application work for its AML drug.

Shares of Sellas Life Sciences (SLS) extended their winning streak to four sessions on Monday after Jefferies disclosed a new stake, while CEO Angelos Stergiou said the company was preparing for a database lock as its pivotal leukemia trial nears final analysis.

SLS stock rose 2% on Monday to end the session at $13.

Jefferies Takes New SLS Stake

Jefferies Financial Group held 200,459 Sellas shares valued at nearly $3 million as of June 30, according to institutional ownership data from Fiscal.ai. Other firms also expanded their positions during the second quarter. Susquehanna increased its holding more than fivefold to 2.05 million shares, while Jones Financial, Bank of America, Wellington Management and Goldman Sachs added to their stakes.

The institutional activity comes as investor attention remains fixed on Sellas’ Phase 3 Regal trial of Galinpepimut-S (GPS) in acute myeloid leukemia (AML).

Regal has recorded 78 of the 80 events required to trigger its final analysis. Once the 80th event occurs, Sellas will announce the milestone before beginning the customary database lock, blinded review, statistical analysis and unblinding process. Stergiou said on LinkedIn that Sellas had entered a quiet period covering clinical updates and other corporate matters as the trial approached its final trigger.

“The executive team is currently focused on operational execution, preparing for the database lock, advancing BLA/CTD regulatory work, and driving the SLS009 program forward,” he said. The study will be considered successful if GPS produces median overall survival of 12.6 months, compared with eight months for the control arm. A positive result could support a potential biologics license application to the FDA.

“We are approaching the pre-specified 80th event in the Phase 3 REGAL trial, marking a critical step toward the final efficacy analysis and, if successful, a potential BLA submission to the FDA,” Stergiou said recently.

SLS CEO Highlights ‘Striking’ AML Data

While maintaining the company’s clinical quiet period, Stergiou highlighted a separate Phase 2 study published in Blood Advances examining a WT1 peptide vaccine as post-transplant maintenance in pediatric acute leukemia. The study reported a three-year overall survival rate of 70.6%, compared with a 30% historical benchmark. It also recorded no non-relapse deaths or increase in graft-versus-host disease.

Stergiou called the findings “striking” and said they provide “further powerful real-world validation of WT1 as a primary target for post-transplant maintenance.” WT1 is also the target behind GPS, but the therapies and patient populations are different. The outside study therefore does not predict Regal’s outcome. Stergiou argued, however, that it supports the underlying strategy of using WT1-directed immune responses to attack residual leukemia cells.

“These data directly support the mechanistic basis of our Phase 3 REGAL trial in adult AML,” he said. Unlike the pediatric study’s single-peptide vaccine, GPS uses multiple engineered peptides to activate two key types of immune cells against leukemia, potentially allowing it to work across a broader range of patients. 

How Do Retail Traders Feel About SLS?

On Stocktwits, retail sentiment for SLS was ‘bullish’ amid a 246% jump in 24-hour message volumes. 

One user called the study “meaningful context heading into the readout,” while cautioning that it was “not proof of success.”

Another user dismissed the publication as “no help” for Sellas because it evaluated a different therapy. Bullish traders, meanwhile, focused on the slowing pace of events and the approaching final-analysis trigger, although their projections about Regal outcome remain speculative.

SLS  stock has surged 698% over the past year. 

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