New York, Jan 7, 2026, 15:40 (EST) — Regular session
Merck & Co (MRK.N) shares were down about 0.3% at $108.59 in afternoon trade on Wednesday after the drugmaker said it had completed its cash tender offer for Cidara Therapeutics (CDTX.O) and expected to finish the acquisition through a merger later in the day. The company said the deal will be treated as an asset acquisition, lifting 2026 research and development expense by about $9.0 billion and cutting earnings per share by roughly 30 cents in the first 12 months. “The acquisition of Cidara strengthens and complements our expanding respiratory portfolio,” Chief Executive Robert M. Davis said. 1
Merck agreed to buy Cidara in November for $221.50 per share, valuing the biotech at about $9.2 billion, to add CD388, an experimental long-acting antiviral designed to prevent influenza infection in people at higher risk of complications. Merck has described CD388 as a late-stage program aimed at season-long protection, rather than a vaccine. 2
The accounting label matters because it pulls costs forward, putting a big one-time hit into 2026 R&D and leaving investors to judge the underlying run-rate. At the same time, U.S. health officials this week updated the childhood immunization schedule and said one dose of the HPV vaccine is as effective as two — a shift that could ripple into demand for Merck’s Gardasil; the update also put rotavirus vaccination into “shared clinical decision-making,” meaning doctors and families decide based on individual risk rather than a blanket recommendation. 3
On the pipeline front, Merck said it has started a Phase 3 lung-cancer study of calderasib (MK-1084), its KRAS G12C inhibitor, in combination with Keytruda QLEX, a subcutaneous version of its blockbuster immunotherapy. The trial plans to enroll about 675 patients and will track progression-free survival — the time until the disease worsens — as a main endpoint in a key subgroup, the company said. “We will evaluate whether this chemotherapy-free combination … may help improve outcomes,” said Dr. Gregory Lubiniecki, a vice president in Merck Research Laboratories. 4
Merck’s Davis and R&D chief Dr. Dean Y. Li are due to appear at the J.P. Morgan Healthcare Conference on Jan. 12, a marquee stop where drugmakers often face pointed questions on deals, trials and guidance. Investors will listen for any added detail on CD388’s path inside Merck and whether management flags any near-term vaccine demand impact. 5
But the near-term setup cuts both ways: CD388 still has to clear late-stage testing, and policy shifts on vaccines can change behavior in messy ways that are hard to model, even if insurance coverage stays intact. The upfront R&D charge also risks muddying comparisons in 2026, especially if financing costs move with rates.
Merck is set to hold its fourth-quarter and full-year 2025 sales and earnings conference call on Feb. 3 at 9:00 a.m. ET. Traders will be watching for the 2026 outlook — particularly how Merck frames the Cidara charge, R&D spend and any early read on vaccines as the new schedule takes hold. 6
