Merck Doses First Patient in Phase 3 ADC for Colorectal Cancer – Pipeline Progress, but No Near-Term Impact

What happened

Merck announced the first patient dosed in a Phase 3 study for an investigational antibody-drug conjugate (ADC) in colorectal cancer, marking a step in its pipeline expansion. However, this early-stage trial is years from potential commercialization and does not alter the company's near-term dependence on Keytruda, which generated 49% of 2025 sales. The DeepValue report highlights that Merck's valuation hinges on containing the ~$2.5B 2026 headwind from generics/IRA and resolving the Gardasil China shipment pause, not on unproven pipeline candidates. While ADC development supports the post-2028 strategy, the news does not change the 6–12 month re-assessment window focused on Keytruda exclusivity and vaccine recovery. As such, the positive sentiment from pipeline progress is unlikely to sustain without more concrete catalysts.

Implication

For investors, the Phase 3 start is a non-event for current fiscal year earnings and a minor positive for long-term pipeline optionality. The stock remains tied to observable near-term catalysts: the April 28 Keytruda PDUFA date, Q2 closure of the Terns acquisition, and any update on China Gardasil shipment resumption. Without data readouts or revenue projections from this ADC, the thesis remains unchanged – wait for evidence that the $2.5B headwind is contained and that Gardasil-China normalizes. Investors should not chase the news, as early-stage oncology trials have high failure rates and provide no margin of safety. The attractive entry zone remains below $105, while upside above $135 would require proof of launch acceleration (Winrevair, Capvaxive) beyond the current base case.

Thesis delta

No material shift. The Phase 3 ADC announcement is a routine pipeline milestone that does not affect the central thesis: MRK is in a holding pattern until the Keytruda LOE and Gardasil China visibility improve. The Wait rating and $105–$135 range remain appropriate, as the news lacks the revenue or regulatory certainty needed to re-rate the stock.