SLS Vs ATNM: Which Cancer Stock Has Bigger Upside Ahead Of Fresh Data Reveal?

• SLS and ATNM are heading into the AACR summit with fresh leukemia-focused data catalysts expected to refocus investor attention.
• Sellas will present preclinical AML data on SLS009, demonstrating increased cancer cell death and activity in models harboring ASXL1 and TP53 mutations.
• Actinium will present two AACR posters on its Actinium-225 radiotherapy platform, including new data on ATNM-400 and Actimab-A across leukemia and solid-tumor programs.

Sellas Life Sciences (SLS) and Actinium Pharmaceuticals (ATNM) investors are bracing for the American Association for Cancer Research (AACR) 2026 Annual Meeting, one of the world’s largest cancer-research conferences scheduled later this week, with fresh leukemia data catalysts. Analyst estimates suggest one stock may offer significantly more upside than the other. 

Both companies are scheduled to present new oncology data on Tuesday at the AACR annual meeting in San Diego, placing their acute myeloid leukemia (AML) programs back in investor focus. Both SLS and ATNM logged two straight weekly gains, with SLS rising 10% last week and ATNM climbing 20% over the same period.

SLS Pipeline Draws Focus Ahead Of AACR

Sellas is preparing to present new early-stage laboratory findings on SLS009, its experimental leukemia drug, during a poster session on April 21.

The company said studies in AML cells showed SLS009 increased caspase-3 activity, a protein that helps trigger cancer-cell death, while reducing levels of survival proteins such as MCL-1 and Survivin that leukemia cells rely on to stay alive. The drug also appeared to become more effective with repeated exposure and remained active in leukemia models carrying ASXL1 and TP53 mutations, genetic changes linked to treatment resistance and poorer outcomes.

However, investor attention to Sellas remains focused on its Phase 3 Regal study evaluating GPS as a maintenance therapy for AML patients whose disease returned but later entered remission after additional treatment. The event-driven study is expected to begin final analysis once 80 overall-survival events are recorded. The company previously said 72 events had been logged as of Dec. 26, bringing the trial closer to the threshold required to initiate topline analysis.

Analyst Targets Favor ATNM Into AACR

Consensus estimates compiled by Koyfin suggest Actinium currently offers the wider valuation runway from recent levels ahead of the AACR presentations.

ATNM holds a 12-month average analyst price target of $5.75, implying a 342% upside from its last close. The stock carries ‘Strong Buy’ ratings from four covering analysts, with no ‘Hold’ or ‘Sell’ recommendations.

Meanwhile, Sellas carries a 12-month average analyst price target of $8.67, implying about 66% upside from current levels. Analyst sentiment on SLS also remains positive, with two ‘Buy’ ratings and one ‘Strong Buy’ rating.

AACR Posters Spotlight ATNM Radiotherapy Pipeline

Actinium will also present two posters on Tuesday, highlighting new data from its Actinium-225 radiotherapy platform across both leukemia and solid-tumor programs.

The company said the presentations will include previously undisclosed findings showing broader activity for ATNM-400, its radiotherapy that delivers cancer-killing radiation directly to tumors. It will also reveal new insight into how Actimab-A, its leukemia radiotherapy candidate, works in AML and its ability to improve responses to standard treatments regardless of mutation type.

In December, the company reported significant tumor-growth inhibition with ATNM-400 across hormone-positive and triple-negative breast cancer models, including disease resistant to commonly used therapies.

ATNM-400 targets a newly identified cancer marker different from PSMA, a well-known target used in radiotherapy treatments, and has shown notable results in lab models of prostate, lung and breast cancers. 

How Do Retail Traders Feel About SLS, ATNM?

On Stocktwits, retail sentiment for ATNM was 'extremely bullish' with 'high' message volume, while sentiment toward SLS was 'bearish' with 'normal' message volume.

One user said, “The reason for the excitement at the AACR Tuesday session [for SLS] is that SLS009 targets a 'Master Switch' that exists in almost all cancer cells, not just leukemia.”

Another user bullish on ATNM said, “This might be the time. Bought another 4,000 shares!”

While SLS stock has surged nearly 300% over the past year, ATNM has climbed 7% over the same period.

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