Shares of Moderna traded lower during the stock market session by 25% or more because there was an early leak of results for it and its partner Merck’s first-in-class investigational messenger RNA [mRNA]-based individualized neoantigen therapy [INT] Intismeran autogene [V940 or mRNA-4157, which was being explored in combination with PD-1 inhibitor KEYTRUDA [pembrolizmab] as an adjuvant for the treatment of patients with completely resected stage IIB-IV melanoma.

The thing is that these late-breaker results were supposed to be set up to be presented this coming Satuday, October 24, 2026, at the upcoming European Society for Medical Oncology [ESMO] Congress. However, there appears to have been a slip-up and the results ended up being released earlier than anticipated. With that being said, both Moderna and its partner Merck decided to release the detailed data early.

The truth is that the data was positive, because in both instances the two efficacy endpoints being evaluated between the intismeran combination and KEYTRUDA alone ended up being achieved in a statistically significant manner. Taking the first endpoint, 42% of patients reduced the risk of disease recurrence, or recurrence-free survival [RFS], with intismeran plus KEYTRUDA, compared to those given KEYTRUDA alone.

Then, the drug even proved to do quite well when it came to helping patients see a reduction in disease metastases or distant metastasis-free survival [DMFS]. There was a 38% reduction for this efficacy endpoint measure. I think that there were two problems that happened here that are why the stock traded lower.

One reason indeed would be the leaked data that happened. However, there is another item that might have caused the stock price to drop, which is the fact that the results changed compared to the prior phase 2b KEYNOTE-942 [mRNA-4157-P201] study. For example, the goal was to see a lower hazard ratio as possible. In prior data, RFS ended up much higher at 49%, which means the HR was lower at .51. In the latest data the HR was .58 so it ended up being an RFS of 49%. The point is that the newest data ended up not meeting prior benchmarks, both in terms of RFS and DMFS.

Still, it is not to say that the data is not good enough to move forward with, though. Plus, how well it does on the market, if it is ultimately approved by the FDA, will depend upon its overall profile. In other words, it could create a competitive advantage in terms of safety and possibly the entire efficacy profile compared to KEYTRUDA alone in this adjuvant setting in these completely resected stage IIB-IV melanoma patients.

The beauty of this tech from Moderna and its partner Merck is that as an individualized RNA-based neoantigen therapy, it uses unique mutation signatures from the patient’s very own tumor. From there, an individualized treatment is created and placed back into the patient in order to present such neoantigens to the immune system and ultimately generate a highly substantial response.

I believe that Moderna should be good going forward with its partner Merck for this program. I’m not stating this randomly; it is because there is an entire INTerpath clinical development program using intismeran either alone as a monotherapy or in combination with KEYTRUDA to treat other types of solid tumors. In essence, this includes a total of 9 phase 2 and phase 3 trials that are using this neoantigen vaccine for these patients.

Speaking of which, this might be another issue to consider as to why the stock is falling. That’s because it remains to be seen how intismeran will fare in terms of treating these other types of solid tumors, like lung cancer, kidney cancer, and several others. Melanoma was likely the easiest bar for Moderna/Merck to start with. The good news is that Moderna believes this data is still ideal, and that’s why it is gearing up to file for FDA approval. Should that happen, and the drug be approved, then it should start being commercialized in the United States in 2027.