SELLAS Life Sciences has been putting out a steady drumbeat of press releases about its pivotal Phase 3 REGAL trial in AML: 60 events reached the interim analysis threshold in late 2024, 72 events by December 2025, 78 events by mid-May 2026. Each release is framed as progress. Each time, the stock has moved on the news. And each time, the update is genuinely, deliberately uninformative about whether the drug works.
That's not a criticism of SELLAS's disclosure — it's a structural feature of how event-driven survival trials work, and it's worth understanding before you react to the next headline that says "X of Y events reached."
What "event-driven" means
REGAL is a randomized trial testing galinpepimut-S (GPS) as maintenance therapy in AML patients who've achieved a second complete remission. Its primary endpoint is overall survival (OS). Rather than reading out at a fixed calendar date, the trial's final analysis triggers once a pre-specified number of events — in this case, deaths — has accumulated across the trial population: 80 events, following an interim analysis at 60.
This design exists because survival trials need enough deaths to have statistical power to detect a difference between arms. Read out too early, with too few events, and even a real treatment effect can be statistically invisible. The event count is a proxy for statistical maturity, not for how the drug is performing.
Why the running tally tells you almost nothing
Here's the part that trips people up: the company remains blinded to which events are occurring in which arm. SELLAS has been explicit about this in every REGAL update — the contract research organization reports a pooled, aggregate event count, and neither the company nor investors know whether those events are disproportionately occurring in the treatment arm, the control arm, or split evenly.
What can be informative, and what SELLAS has also disclosed, is the outcome of the pre-specified interim analysis: in January 2025, the Independent Data Monitoring Committee (IDMC) completed its interim review at 60 events and recommended the trial continue without modification, having confirmed the drug exceeded pre-specified futility criteria with no safety concerns. That's a real, if limited, signal — an unblinded committee looked at the data and didn't see grounds to stop the trial for futility or harm. It is not equivalent to a positive efficacy read; futility thresholds are set deliberately low so that only a clearly failing trial gets stopped early.
What to actually watch for
- IDMC recommendations, not raw event counts — a "continue without modification" is more informative than "N events reached," though still not a proxy for the eventual result.
- The final analysis announcement itself — this is the actual unblinding, and the only point at which the efficacy data becomes knowable.
- Company cash position relative to the expected timeline — see our companion piece on small-cap AML balance sheets. A company that can comfortably fund the wait to final analysis is in a very different position than one racing its runway against an event-driven clock it can't control.
The read
Every event-count update is real information about trial timeline and essentially no information about trial outcome. Treat "78 of 80" the way you'd treat a countdown clock, not a scoreboard — it tells you roughly when you'll know the answer, not what the answer is.
This piece reflects clinical and financial analysis based on public filings and disclosures as of August 2026. It is not investment advice, and Stevenson HemOnc Advisors does not hold, and has not been compensated by, any company named above.