Moderna shares slip as William Blair cuts rating on valuation after rally

Moderna Inc (NASDAQ:MRNA) slid 3% in premarket trading after William Blair downgraded the biotechnology company to Market Perform from Outperform, citing valuation constraints following a meteoric run. The downgrade follows a staggering 545% year-to-date rally, driven by a near-250% surge since August after encouraging Phase 3 INTERPATH-001 data for its personalized cancer vaccine candidate.

While William Blair acknowledged that interim data for intismeran alongside Merck & Co.’s Keytruda in adjuvant melanoma supports a potential new standard of care, analyst Myles Minter indicated that current share levels already price in an aggressive trajectory. Minter noted that Moderna’s current valuation reflects an implied 70% to 75% probability of success across expanded oncology indications, leaving net present value only modestly above the company’s current market capitalization.

Investor focus is now shifting toward intismeran's commercial boundaries and whether the individual neoantigen therapy can expand beyond melanoma into broader solid tumors such as lung, renal, and bladder cancers. Although William Blair models $5.4 billion in peak melanoma sales shared equally with Merck, expanding into colder, lower tumor mutational burden cancers carries significant biological hurdles and distinct clinical risk.

The primary debate centers on the upcoming Phase 2 INTERPATH-004 trial in renal cell carcinoma, which is expected to deliver readouts by late 2026 or 2027 as a pivotal binary catalyst. In the near term, investors are also scrutinizing commercial scalability and complex supply-chain logistics ahead of a key manufacturing facility tour in Marlborough, Massachusetts, scheduled for November 12.