Wire reporting: (AP, via WPRI 12)

Merck and Moderna said Thursday that a personalized mRNA vaccine given with Merck's immunotherapy Keytruda (pembrolizumab) cut the risk of melanoma returning or of death by 42% compared with Keytruda alone in a late-stage trial after surgery^2,5,6.

The Phase 3 study enrolled 1,137 people with stage IIB through IV melanoma that had already been removed, randomized 2-to-1 to the custom shot plus Keytruda or Keytruda plus placebo². The Associated Press described the same trial as more than 1,100 patients on standard Keytruda who were randomly assigned to the vaccine or a placebo^5,6.

The investigational product, intismeran (also called mRNA-4157), is built from each patient's tumor: researchers compare cancer and healthy DNA and encode up to 34 cancer-specific mutations so the immune system can target those cells if they return². The AP account said patients received nine doses three weeks apart while already on Keytruda^5,6.

Company figures reported by Ars Technica said that after two years, 82% of people on the combination were alive without recurrence, versus 70% on Keytruda and placebo². The AP report gave the same two-year split as 82% versus 70%^5,6.

Moderna and Merck had said in August that the trial met its goal but held detailed numbers for the European Society of Medical Oncology meeting in Madrid this weekend; after an oncology site reported results early, the companies released top-line data Thursday, Ars Technica said². The AP report likewise said a leak prompted an early release ahead of Saturday's presentation^5,6. Ars Technica said the full dataset has been accepted by the New England Journal of Medicine².

Moderna chief executive Stéphane Bancel said in a company statement that the results "show what's possible when we rethink how medicines are made"². Merck and Moderna are already talking with regulators about next steps toward approval, both Ars Technica and the AP account said^2,5,6.

The AP report said side effects were mainly sore arm, fatigue and other reactions typical of mRNA coronavirus shots, according to trial investigator Dr. Hussein Tawbi of MD Anderson Cancer Center^5,6. Moderna president Stephen Hoge told the AP that brewing a dose takes a few days but the full process from tumor genetics can take about six weeks^5,6. The companies have not discussed a possible price, the AP said^5,6.

The AP report said Moderna shares fell 18% Thursday after the detailed results, while remaining well above late-August levels^5,6. Independent overall survival data and a published peer-reviewed paper are not yet public^2,5,6,7.

The Guardian, which could not be quoted here, reported the same 1,137-patient trial as Australian-led across 157 sites, with all participants on pembrolizumab for 12 months and some also given intismeran⁷. It said trial investigator Prof. Georgina Long of Melanoma Institute Australia will present the data at ESMO, that the findings have been accepted by the New England Journal of Medicine, and that the manufacturers said it was too early to say whether the combination improved long-term survival⁷. Independent researchers cited there said not all patients respond at the outset and that longer follow-up is needed⁷. The paper said the shot would not be standard care until further study and regulatory review, which may take several years⁷.

The New York Times published a Friday follow-up on the same Merck-Moderna melanoma results; the full text could not be read here and is not used for facts⁸.

ABC-owned stations including ABC7 Los Angeles, ABC7 News Bay Area, ABC30, ABC7 Chicago, ABC11, ABC7 New York, 6abc, and ABC13 Houston later posted the same Associated Press report already cited via The Seattle Times and AP, including the 42% risk figure, more than 1,100 patients, nine doses, and comments from trial investigator Dr. Hussein Tawbi^{9,10,11,12,13,14,15,16,5,6}. KTLA also posted that AP report; the page was blocked by a captcha here and is not used for additional facts^17,6. FOX 8 Cleveland posted the same AP report via Nexstar Media Wire^18,6. WGN posted the same AP report; the page was blocked by a captcha here and is not used for additional facts^19,6. WFLA posted the same AP report^20,6. KHON2 posted the same AP report^21,6.

WSVN 7 carried a CNN report that repeated the 42% risk figure and said the vaccine or placebo was given as an intramuscular shot every three weeks for up to nine doses, while Keytruda was infused every six weeks for up to about a year²². CNN quoted Memorial Sloan Kettering melanoma chief Dr. Michael Postow, who treated trial patients, as saying the shot's efficacy and mechanism were unlike prior options²². The CNN account said companies called overall survival too early to judge but described a favorable trend, and that RBC Capital Markets said the Phase 3 effect was weaker than an earlier smaller trial while still expecting likely FDA action next year²². CNN said Moderna shares fell 18% Thursday and Merck's fell 1.8%²².

Not medical advice.

Sources

1. New York TimesCancer Vaccine Cuts the Risk of Melanoma Recurrence, Merck and Moderna ReportOct 22, 10:02 PM
2. Ars TechnicaModerna and Merck say their mRNA cancer vaccine cut death, recurrence by 42%Oct 22, 6:12 PM
3. ReutersMerck/Moderna cancer vaccine cuts risk of death or recurrence from melanoma by over 40%Oct 22, 2:35 PM
4. (AP, via WPRI 12)Novel mRNA cancer vaccine helps reduce the chances of melanoma patients' tumors returningAlso (AP, via The Seattle Times), (AP, via ABC7 Los Angeles), (AP, via ABC7 News Bay Area), (AP, via ABC30), (AP, via ABC7 Chicago), (AP, via ABC11), (AP, via ABC7 New York), (AP, via 6abc), (AP, via ABC13 Houston), (AP, via KTLA), (AP, via FOX 8 Cleveland), (AP, via WGN), (AP, via WFLA), (AP, via KHON2)Oct 22, 8:10 PM
5. APA novel mRNA cancer vaccine helps reduce the chances of melanoma patients' tumors returningOct 23, 12:30 AM

The Guardian · New York Times · WSVN 7ShowHide

1. The Guardian‘Bespoke’ mRNA vaccine significantly reduces risk of melanoma recurrence or death, clinical trial showsOct 23, 12:27 AM
2. New York TimesMelanoma Vaccine Ushers in New Hope for Cancer PatientsOct 23, 5:00 AM
3. WSVN 7Experimental mRNA vaccine cuts risk that melanoma returns by 42%Oct 23, 6:45 PM

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