Moderna’s personalized melanoma vaccine beat its control arm in a 1,137-patient Phase 3 trial, and the stock fell 17.6% on Thursday anyway, closing at $202.63 after trading was briefly halted when the figures surfaced two days before their scheduled Saturday presentation. More than $17 billion of market value vanished. Our read: the market did not reject the trial. It rejected one number inside it. Protection against distant spread came in at 38%, against 59% in the Phase 2b study the rally was built on, and that shortfall is three times the size of the one on the headline endpoint.
The arithmetic comes from the companies’ own paperwork. Merck and Moderna’s October 22 release puts the cut in recurrence or death at 42% and the cut in distant metastasis or death at 38%. The August 19 release gave the Phase 2b five-year figures of 49% and 59%. Subtract and the recurrence number slipped 7 points while the distant-spread number slipped 21. We lined up both sets, hazard ratios and confidence intervals included.
| Measure | Phase 2b, five-year | Phase 3, 24.6-month median |
|---|---|---|
| Recurrence or death, hazard ratio (95% CI) | 0.51 (0.294 to 0.887) | 0.58 (0.45 to 0.75) |
| Relative risk cut | 49% | 42% |
| Distant metastasis or death, hazard ratio (95% CI) | 0.411 (0.200 to 0.843) | 0.62 (0.45 to 0.85) |
| Relative risk cut | 59% | 38% |
Why the Distant-Spread Gap Is the One That Matters
Read the intervals and the two trials agree on recurrence. The Phase 2b estimate of 0.51 sits inside the Phase 3 range of 0.45 to 0.75. On distant spread they part ways: the Phase 3 range of 0.45 to 0.85 excludes the Phase 2b estimate of 0.411, while the Phase 3 estimate of 0.62 sits comfortably inside the Phase 2b range of 0.200 to 0.843. The populations and follow-up differ, so this is not a clean head-to-head. But a wide interval on a small trial is a warning label, and the stock priced the point estimate.
It had priced it blind. When the companies announced on August 19 that the trial had met its primary endpoint, the release disclosed no Phase 3 hazard ratio at all. Moderna still rocketed 177% to close at $174.38 and kept climbing. For nine weeks, the only efficacy numbers holders had to fill the blank were the Phase 2b ones.
The Case That the Selloff Overshot
There is a fair bull argument, and the release contains it. After the first six months, a prespecified sensitivity analysis shows recurrence or death down 58% (hazard ratio 0.42) and distant metastasis or death down by half (0.50). Those look like Phase 2b. It is not the primary endpoint, so it supports the bull case without replacing the headline number. Overall survival data are still immature, with a favorable trend the companies describe but do not quantify.
The cautious reading has a voice too. RBC Capital Markets analyst Trung Huynh called the results “low end” of expectations and said “commercial success is far less certain.” The same report notes 7% of vaccine recipients discontinued over adverse events against 5% on Keytruda alone, with more fever and injection-site pain.
What the $202.63 Price Still Assumes
At the intraday low, Moderna was down about 25% at $183.88, roughly $24 billion gone. Even the close leaves a striking position. Working back from the 177% jump, the August 18 close was about $62.95 (174.38 divided by 2.77), so Thursday’s close is still 3.2 times where the stock stood before anyone knew the trial had succeeded.
A tripled stock after its worst day since August is paying for more than melanoma. Merck and Moderna are also testing the combination in lung, bladder and kidney cancer, with interim kidney results expected late this year or early next. Those readouts, not the melanoma leak, now carry the valuation. On Saturday at the ESMO Congress, watch two things in the full presentation: whether the survival curves separate after month six, and whether any overall survival figure appears. If the second half of the curve holds, Thursday was a repricing. If it does not, it was the first installment.