Moderna stock rose 8% to $143.79 Friday morning, extending a third consecutive session of sharp reversals after surging 177% Wednesday on a Phase 3 melanoma result, falling 18% Thursday and initially trading sharply lower Friday. The move came as the S&P 500 gained 0.3% and the NASDAQ 100 rose 0.1%, indicating that the volatility was concentrated in the biotech sector rather than driven by a broad macro shift. BioNTech rose 4% to $114.97, while Merck traded at $149.36 as investors assessed the potential contribution to its Keytruda franchise. Moderna and Merck said intismeran, their individualized mRNA cancer vaccine, met the primary endpoint in a Phase 3 melanoma trial by improving recurrence-free and metastasis-free survival when combined with Keytruda in patients whose tumors had been surgically removed. It was described as the first successful late-stage trial of its kind, although the complete dataset has not been publicly presented and could be released at the ESMO conference in Madrid from October 23 to 27. Retail activity added to the swings, with a widely shared WallStreetBets post receiving 4,914 upvotes and 476 comments and Reddit sentiment registering as very bullish across 52 qualified mentions. Moderna is up 352% year to date, compared with BioNTech’s 16% gain, Merck’s 44% increase and a 25% rise for the iShares Biotechnology ETF, which traded at $212.28. Moderna’s full-chain put/call ratio (puts relative to calls across listed options) was 0.86, with expirations ranging from 0.79 near-dated to 8.54 in early October; BioNTech’s ratio was 0.28. Traders are watching whether Moderna holds its Friday gains after two full reversals and whether the late-October ESMO schedule pulls positioning forward. The source also recommends sizing speculative positions at 5% of a portfolio and references a free playbook covering sizing and exit rules.