✦ Intismeran: A Cancer Vaccine Given With KeytrudaThin moat

Merck & Co. (MRK) — the future bets

Merck's personalised cancer vaccine worked in a 1,137-patient melanoma trial, and it is given with Keytruda, which keeps Keytruda in the treatment.

Intismeran autogene is a personalised cancer vaccine that Merck is developing with Moderna. It is manufactured for each patient from the genetic profile of the tumour and is designed to encode up to 34 neoantigens1. In August 2026 the Phase 3 INTerpath-001 trial, which recruited 1,137 patients with completely resected stage IIB to IV melanoma, met both primary endpoints, with the vaccine given together with Keytruda2.

Merck share price, year to September 2026 ($)77.5852-week low147.98Close, 24 Sep 2026156.9252-week highstockanalysis, 24 September 2026
The pipeline news nearly doubled the price.

The market reaction was immediate. Merck's shares rose by approximately 12% on the announcement and touched a new record high3. Overall survival data remain immature, and the timing of regulatory review, manufacturing cost and price are unknown4.

The strategic interest is obvious. A product given alongside Keytruda keeps Keytruda in the treatment, and if the combination becomes standard in early-stage cancers, Merck has a reason for doctors to stay with its antibody, even as biosimilars arrive.

The risk is equally obvious. A personalised vaccine is expensive to make, one patient at a time, and the economics are shared with a partner.

The share price reflects the hope. Merck's shares traded between $77.58 and $156.92 over the fifty-two weeks to 24 September 2026, closing at $147.985, and the analyst report on the trial noted that the rise reflected the vaccine as a possible additional oncology revenue stream as Merck begins to lose revenue from patent expirations6.

This is a high-value, early bet. Merck's unallocated research spending, $14,987 million in 20257, funds programmes like it; the signal to wait for is regulatory filings and overall survival data, and a delay in either beyond 2027 would leave the vaccine arriving after Keytruda's American exclusivity has ended.

Moat trajectory: Widening

Phase 3 met both primary endpoints in August 2026.

The number that tests this moat
Reported
Unallocated research and development, full year
$14,987M (2025)

The laboratory spending that funds bets like this; a sharp cut would mean fewer shots at a successor.

Source: Merck Form 10-K, FY2025 ↗
References
  1. ReportedIt is manufactured for each patient from the genetic profile of the tumour and is designed to encode up to 34 neoantigens.
    TradingKey, 20 August 2026 - the INTerpath-001 Phase 3 result for intismeran autogene with Keytruda (1,137 patients) and the share price reaction of approximately 12%. — August 2026 · publ. 20 August 2026 · source ↗
  2. ReportedIn August 2026 the Phase 3 INTerpath-001 trial, which recruited 1,137 patients with completely resected stage IIB to IV melanoma, met both primary endpoints, with the vaccine given together with Keytruda.
    TradingKey, 20 August 2026 - the INTerpath-001 Phase 3 result for intismeran autogene with Keytruda (1,137 patients) and the share price reaction of approximately 12%. — August 2026 · publ. 20 August 2026 · source ↗
  3. ReportedMerck's shares rose by approximately 12% on the announcement and touched a new record high.
    TradingKey, 20 August 2026 - the INTerpath-001 Phase 3 result for intismeran autogene with Keytruda (1,137 patients) and the share price reaction of approximately 12%. — August 2026 · publ. 20 August 2026 · source ↗
  4. ReportedOverall survival data remain immature, and the timing of regulatory review, manufacturing cost and price are unknown.
    TradingKey, 20 August 2026 - the INTerpath-001 Phase 3 result for intismeran autogene with Keytruda (1,137 patients) and the share price reaction of approximately 12%. — August 2026 · publ. 20 August 2026 · source ↗
  5. ReportedMerck's shares traded between $77.58 and $156.92 over the fifty-two weeks to 24 September 2026, closing at $147.98, and the analyst report on the trial noted that the rise reflected the vaccine as a possible additional oncology revenue stream as Merck begins to lose revenue from patent expirations.
    Merck & Co. (MRK) market data - $147.98 at the close on 24 September 2026, market cap $365.09B, trailing P/E 116.26, forward P/E 17.19, trailing net income $3.17B, 52-week range 77.58-156.92. — September 2026 · publ. 24 September 2026 · source ↗
  6. ReportedMerck's shares traded between $77.58 and $156.92 over the fifty-two weeks to 24 September 2026, closing at $147.98, and the analyst report on the trial noted that the rise reflected the vaccine as a possible additional oncology revenue stream as Merck begins to lose revenue from patent expirations.
    TradingKey, 20 August 2026 - the INTerpath-001 Phase 3 result for intismeran autogene with Keytruda (1,137 patients) and the share price reaction of approximately 12%. — August 2026 · publ. 20 August 2026 · source ↗
  7. ReportedMerck's unallocated research spending, $14,987 million in 2025, funds programmes like it; the signal to wait for is regulatory filings and overall survival data, and a delay in either beyond 2027 would leave the vaccine arriving after Keytruda's American exclusivity has ended.
    Merck & Co. Form 10-K for fiscal 2025 - patents, exclusivity dates, biosimilar competition and royalties. — FY2025 · publ. 24 February 2026 · source ↗
Sources
Generated September 25, 2026