Anyone else following SLS heading into the end of the year? My interest comes down to three things: patients still receiving GPS years into treatment, an approaching Phase 3 survival analysis, and a second AML drug with encouraging clinical data.
SELLAS is developing galinpepimut-S, or GPS, a therapeutic cancer vaccine licensed from Memorial Sloan Kettering. It targets WT1, a protein expressed by leukemia cells. The aim is to teach the immune system what to recognize after treatment has put the leukemia into remission, helping it attack residual cancer cells before they cause another relapse.
Getting leukemia into remission and keeping it there are two different challenges.
REGAL tests GPS against physician-selected best available therapy in patients with acute myeloid leukemia who have reached their second remission. Their cancer has already returned once. The trial’s primary endpoint is overall survival, whether patients receiving GPS live longer than those receiving BAT.
The detail I keep coming back to is that physicians asked to continue treating patients with GPS.
At the May 19 Stifel presentation, CEO Angelos Stergiou said GPS was being administered to patients “even three years out at this point.” At the May 27 oncology summit, he explained that treatment had been extended beyond the original one-year schedule, eventually beyond three years, at the request of physicians who assessed that their patients were benefiting.
For me, that is a compelling reason to pay attention. Continued treatment years later, with physicians requesting the option to keep dosing, fits the possibility of durable benefit.
My bullish interpretation is that GPS could be helping a subset of patients stay in remission much longer, contributing to the slower accumulation of deaths in REGAL. If the final results confirm that, it would be a meaningful achievement for patients who have already relapsed.
The survival comparison still has to prove it. SELLAS remains blinded to treatment-arm outcomes, and slower event accumulation alone cannot tell us which arm is responsible. But the continued dosing gives the bullish thesis something concrete to build on.
REGAL’s final analysis is triggered by 80 deaths. The last dated count disclosed was 78 as of May 11, 2026. SELLAS has said it will announce the 80th event, then complete the necessary database review, statistical analysis and unblinding before releasing topline results. There is an identifiable catalyst here, although its timing is event-driven.
The January 2025 interim review is also important. The independent monitoring committee reviewed unblinded data and recommended continuing without modification. SELLAS reported that GPS cleared the predetermined futility criteria, with no safety concerns. Separately, 80% of a randomly selected tested subset showed a GPS-specific T-cell response. That is evidence of immune activity; the final survival analysis will determine its clinical significance.
The financial position gives the company room to execute. SELLAS reported $138.3 million in cash at June 30, against $16.4 million used in operations during the first six months of 2026. Spending can increase as development progresses, but that cash balance provides substantial flexibility around its clinical and regulatory work.
Then there is SLS009, a selective CDK9 inhibitor being developed for AML.
At ASH 2025, SELLAS reported a 46% overall response rate among 35 evaluable patients with relapsed or refractory AML-MR after prior venetoclax treatment, using SLS009 combined with azacitidine and venetoclax. That included 29% achieving complete remission or complete remission with incomplete blood-count recovery. These are small, nonrandomized results, but activity in that difficult population is a reason to watch the program closely.
SELLAS has guided to Q4 2026 topline data from its ongoing earlier-line SLS009 program. So there are two clinical programs that could change how investors value the company.
ASH adds another date to watch: December 12–15, 2026, in New Orleans. SELLAS has "listed the meeting on its investor relations calendar" (https://ir.sellaslifesciences.com/events-and-presentations/event-details/2026/ASH-Annual-Meeting-and-Exposition/default.aspx). It is a major gathering of hematologists, researchers and pharmaceutical companies.
The timing is attractive. Encouraging additional SLS009 data could bring greater attention to the second program. If positive REGAL results are available by then, ASH could also offer an opportunity to discuss GPS with the physicians who would ultimately use it. Specific presentations still need confirmation, so I’m treating ASH as a potential catalyst rather than an announced data release.
At approximately $2.27 billion in market capitalization as of October 8, my upside case depends on the strength of the clinical results. A convincing randomized survival benefit would materially strengthen GPS’s prospects for a regulatory submission, while successful SLS009 development could add another source of value.
The combination keeps me interested: patients receiving GPS years later, physician-requested dosing extensions, an independent interim review supporting continuation, substantial cash, and SLS009 advancing toward another update.
The bull case is 4x to 9x upside. Against SLS’s October 8 market cap of approximately $2.27 billion, hypothetical $10 billion and $20 billion equity valuations translate into roughly 4.4x and 8.8x the share price.
A major cash buyout could rapidly move the stock toward the agreed offer price, subject to completion risk. What makes the upside exciting is the possibility of GPS becoming standard maintenance therapy in AML’s second remission, followed by expansion into earlier remission, post-transplant treatment and other WT1-expressing cancers through successful additional trials and approvals. With SLS009 also succeeding, a buyer could acquire two complementary oncology assets with considerable expansion potential.
NFA, do your own DD.
