Sellas Life Sciences: From 330% Rally to Waiting for One More Event

Sellas shares swing wildly as market awaits 80th event in REGAL phase 3 AML study; cash runway extends to 2029, with SLS009 data due in 2026.

The past week for Sellas Life Sciences has been a trader’s rollercoaster. Shares surged 18 percent on Wednesday, only to plunge 16 percent the next day, before recovering 4 percent on Friday to close at €6.76. The moves have little to do with company announcements and everything to do with mounting anticipation of a single clinical milestone. Over the past month, the stock has climbed 65 percent, and over the past twelve months it has rocketed 330 percent.

At the heart of this volatility lies the REGAL phase 3 study of galinpepimut-S (GPS) in acute myeloid leukemia. As of May 11, 78 of the required 80 events had been recorded by the contract research organization. Sellas itself remains blinded to the data. Once the 80th event occurs, the company will trigger a database lock, followed by unblinding and topline results — a process it has promised to communicate publicly. The market is therefore betting on timing rather than data, a speculative posture that leaves the stock exposed to sharp swings in either direction.

Financially, the company enters this binary phase on solid footing. Cash and equivalents stood at $107.1 million at the end of the first quarter, with an additional $7.5 million raised through warrant exercises in the current quarter. Management expects this runway to extend into 2029. The net loss for Q1 was a manageable $8.4 million. Operating expenses rose partly due to preparations for a potential regulatory submission following the REGAL analysis.

Beyond GPS, Sellas is advancing SLS009 (tambiciclib), a CDK9 inhibitor. A phase 2 trial with 80 newly diagnosed AML patients is ongoing, with topline data anticipated in the fourth quarter of 2026. Preclinical data presented at AACR showed that SLS009 induces apoptosis in AML cell lines, including those with high-risk mutations such as ASXL1 and TP53. While REGAL dominates investor attention, SLS009 provides a secondary timeline that could reshape the pipeline narrative later this year.

Analyst views remain divided. A May 22 report downgraded the stock to "Strong Sell," flagging the risk that a longer study duration could reflect improved survival in the control arm rather than a treatment benefit. The more bullish interpretation holds that prolonged follow-up may signal extended survival among GPS patients. On the institutional side, BlackRock increased its stake by 62 percent, and at the peak of the week’s trading, more than 25 million shares changed hands.

From a technical perspective, the stock closed at its weekly support of €6.76 on Friday, with the 50-day moving average at €4.57 — well below the current price. The 52-week high of €7.70, set on May 20, lies only 12 percent above Friday’s close. The relative strength index of 59.8 suggests the stock is neither overbought nor oversold, leaving room for continued momentum in either direction. The immediate support on the downside is the Thursday low of €6.35.

The next catalyst window opens on May 27, when Sellas presents at the TD Cowen investor day. That event could serve as the venue for an announcement of the 80th event, or it could see the company remain silent — a scenario that would raise the risk of profit-taking. Whether the stock extends its remarkable rally or retreats ahead of the actual data readout depends entirely on when that final event ticks over. For now, Sellas sits at the intersection of high hope and hard data, with only two missing events separating them.