SLS, IBRX Stocks In Focus: Analyst Says Moderna-Merck Cancer Vaccine Success ‘Bodes Well’ For Oncology

Moderna soared 177% Wednesday, while Merck gained 13% and the rally spread to BioNTech, Arcturus, Tempus AI and Novavax.

• Morningstar raised its 2035 Intismeran sales forecast to $16.8 billion and said the result “bodes well” for studies in larger cancers.
• Sellas’ Phase 3 GPS cancer vaccine targets WT1 and has previously been tested with Keytruda.
• ImmunityBio’s approved Anktiva activates cancer-fighting immune cells and has been studied with checkpoint inhibitors.

Sellas Life Sciences (SLS) and ImmunityBio (IBRX) are in focus after Moderna and Merck’s landmark Phase 3 cancer-vaccine update triggered an oncology rally and boosted investor confidence in immune-based cancer therapies.

Merck and Moderna said their personalized mRNA cancer vaccine, Intismeran Autogene, helped patients with high-risk melanoma remain cancer-free longer and delayed the disease from spreading to distant parts of the body when combined with Keytruda, compared with Keytruda alone.

The Phase 3 INTerpath-001 trial enrolled patients whose tumors had been completely removed through surgery. The companies called it the first positive late-stage trial for both a personalized therapy designed around each patient’s unique tumor mutations and an mRNA-based cancer vaccine.

Analysts See $16.8B Intismeran Opportunity 

Morningstar called the early Phase 3 success a “good sign” and said it “bodes well” for Intismeran studies in other cancers, including lung cancer, which represents a substantially larger patient population. The brokerage raised its 2035 Intismeran sales forecast to $16.8 billion from $7.2 billion, with Moderna and Merck splitting profits equally. 

The firm increased its assumed probability of melanoma approval to 100% from 60% and lifted the figure for lung cancer to 60% from 40%. It expects a potentially rapid approval in the first half of 2027 once the data are submitted.

Meanwhile, Goldman Sachs called the readout the “initial unlock” for Moderna’s cancer business. UBS highlighted the therapy as a potentially meaningful new growth driver, while Morgan Stanley cautioned that Moderna’s valuation already reflects more than $20 billion in risk-adjusted peak Intismeran sales, nearing Keytruda’s blockbuster scale on an unadjusted basis. 

Cancer Vaccine Win Sparks Oncology Rally 

Moderna surged 177% on Wednesday, marking its best session ever, while Merck gained about 13% and hit a record high. The rally spread to other mRNA and oncology stocks: BioNTech climbed 22%, Arcturus Therapeutics jumped more than 25%, Tempus AI advanced 24%, and Novavax added 11%.

Momentum cooled on Thursday as Moderna, Merck and BioNTech pulled back. SLS and IBRX also gave back part of their Wednesday gains. Meanwhile, Arcturus and Tempus AI bucked the trend, rising another 7% and 9%, respectively, with Arcturus reaching its highest level in nearly 10 months.

What The Win Means For SLS, IBRX 

Sellas’ lead candidate, Galinpepimut-S (GPS), is a cancer vaccine designed to train the immune system to recognize WT1, a protein found at high levels in several cancers. It is currently being tested as a maintenance treatment for acute myeloid leukemia (AML) in the Phase 3 Regal trial.

Sellas has also worked with Merck to combine GPS with Keytruda. In patients with WT1-positive ovarian cancer, the combination kept the disease under control longer and delayed its progression compared with historical results for Keytruda alone.

ImmunityBio’s connection is through combination immunotherapy rather than cancer vaccines. Its approved drug Anktiva activates natural killer cells and T cells—two key parts of the immune system’s cancer defenses. The company has tested Anktiva with Keytruda and similar checkpoint inhibitors in lung cancer, aiming to restore immune activity and help patients whose tumors stopped responding to PD-1 or PD-L1 therapies.

How Do Retail Traders Feel About Oncology Stocks?

On Stocktwits, retail sentiment was ‘extremely bullish’ for MRNA, TEM and ARCT, with ‘extremely high’ message volume across all three. Sentiment was ‘bullish’ for MRK and BNTX amid ‘extremely high’ volume, while SLS was ‘bullish’ with ‘high’ volume. IBRX sentiment remained ‘neutral’ amid ‘normal’ message volume. 

Over the past year, SLS has surged 624%, followed by MRNA at 296%, IBRX at 246%, and MRK at 82%. Meanwhile, BNTX has edged 0.4% lower, while TEM and ARCT have fallen 9% and 37%, respectively. 

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