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MRNA Tanks as Positive Phase III Cancer Therapy Data Fails to Impress

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Key Takeaways

  • Moderna's intismeran plus Keytruda cut recurrence or death risk by 42% in a Phase III melanoma study.
  • After six months, the combination reduced recurrence risk by 58% and distant metastasis risk by 50%.
  • MRNA plunges 18% after early data disclosure, as investors weighed results against elevated expectations.

Moderna (MRNA - Free Report) , along with partner Merck (MRK - Free Report) , reported detailed positive results from the phase III INTerpath-001 study evaluating their investigational personalized cancer therapy in certain patients with high-risk melanoma, a serious form of skin cancer.

The study evaluated Moderna’s investigational mRNA-based individualized neoantigen therapy (“INT”), intismeran autogene (mRNA-4157 or V940), in combination with Merck’s blockbuster PD-L1 inhibitor, Keytruda (pembrolizumab), as an adjuvant treatment for patients with completely resected stage IIB-IV melanoma.

What Did MRNA & MRK’s Latest Findings Show?

The detailed data builds on the positive top-line results Moderna and Merck announced in August 2026, when the combination met the trial’s primary endpoint of recurrence-free survival (RFS) and key secondary endpoint of distant metastasis-free survival (DMFS).

The company had previously announced that INTerpath-001 had achieved the primary endpoint but is now releasing detailed data.

At a prespecified primary analysis, after a median follow-up of 24.6 months, treatment with intismeran plus Keytruda reduced the risk of recurrence or death by 42%. The combination regimen also reduced the risk of distant metastasis or death by 38% versus Keytruda alone.

In a prespecified sensitivity analysis, the benefit was greater after six months, following the intismeran immunization regimen. The combination reduced the risk of recurrence or death by 58% and the risk of distant metastasis or death by 50% compared with Keytruda alone. The companies also reported that the improvements observed in RFS and DMFS were generally consistent across pre-specified patient subgroups.

Overall survival data remain immature, although the companies observed a favorable trend. The study will continue to evaluate overall survival and other key endpoints. The safety profile of intismeran plus Keytruda was generally consistent with earlier studies, with no new safety signals reported.

Moderna and Merck are engaging with regulatory authorities based on the phase III findings.

The detailed results follow a data leak ahead of MRNA and MRK’s planned presentation at the 2026 European Society for Medical Oncology (ESMO) Congress. The companies formally disclosed the findings on Oct. 22, ahead of their presentation at the ESMO Presidential Symposium. The findings were supposed to be reported on Oct. 24, after the data presentation at ESMO, but due to the data leak, MRK and MRNA announced the data on Oct. 22. The data will still be presented at the ESMO as planned.

The latest phase III results build on the phase IIb KEYNOTE-942 study, which reported long-term benefits for the combination regimen. Five-year follow-up data presented at the 2026 ASCO annual meeting showed that the combination reduced the risk of recurrence or death by 49% and the risk of distant metastasis or death by 59% versus Keytruda alone.

Impact on MRNA Stock

Despite the positive clinical findings, Moderna’s shares plunged 18% on Oct. 22. The steep decline followed the premature disclosure of the INTerpath-001 data ahead of the planned ESMO presentation. Some market reports suggest the sell-off reflected a “sell-the-news” reaction, with investors weighing the results against elevated expectations for the personalized cancer therapy. Investors also seemed unimpressed when they compared the latest findings with the phase IIb study data, especially the risk of distant metastasis or death. Merck’s shares fell around 1.8% on the same day.

Year to date, shares of Moderna have skyrocketed 587.2% compared with the industry’s increase of 6.8%.

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More on MRK & MRNA’s Personalized Cancer Therapy

Intismeran autogene is an experimental, personalized mRNA-based cancer therapy that is designed using the unique genetic mutations found in a patient’s tumor and can target up to 34 tumor-specific antigens.

Unlike conventional vaccines, intismeran is individually designed for each patient, using mutations identified from the patient’s tumor to create a personalized treatment intended to help the immune system recognize and attack cancer cells. This individualized approach could allow the therapy to be adapted to the unique characteristics of different patients and tumor types.

Merck and Moderna are evaluating intismeran across the broader INTerpath clinical development program, which currently includes nine phase II and phase III studies across melanoma, non-small cell lung cancer, bladder cancer and renal cell carcinoma. The program is evaluating intismeran in combination with Keytruda and other anticancer therapies, as well as as a monotherapy.

If successfully developed and upon potential, intismeran autogene could provide a new growth driver for Moderna and establish oncology as a key growth driver beyond its vaccines business. However, the near-term impact remains limited as the candidate is still investigational, overall survival data are immature, and regulatory review and commercialization timelines remain uncertain.

MRNA Zacks Rank & Stocks to Consider

Moderna currently carries a Zacks Rank #3 (Hold).

Some better-ranked stocks in the biotech sector are TG Therapeutics (TGTX - Free Report) and Halozyme Therapeutics (HALO - Free Report) , each currently sporting a Zacks Rank #1 (Strong Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.

Over the past 60 days, estimates for TG Therapeutics’ 2026 earnings per share have risen from 92 cents to 94 cents, while estimates for 2027 have increased from $2.65 to $2.66 during the same time. TGTX shares have surged 78.4% year to date.

TG Therapeutics’ earnings beat estimates in one of the trailing four quarters, while missing the same on the remaining three occasions, with the average surprise being 184.65%.

Over the past 60 days, estimates for Halozyme’s 2026 earnings per share have risen from $8.37 to $8.80, while estimates for 2027 have increased from $9.75 to $10.29 during the same time. HALO shares have soared 85.1% year to date.

Halozyme’s earnings beat estimates in three of the trailing four quarters, while missing the same on the remaining occasion, with the average negative surprise being 19.12%.

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