** Brokerage TD Cowen downgrades drugmaker Merck's MRK.N shares to "hold" from "buy" on weak forecast and a "lack of clarity" regarding shipment of its HPV vaccine Gardasil in China

** Last week, MRK forecast total revenues below Wall Street estimates and said it would not ship Gardasil in China until at least the middle of the year

** Lowers PT to $100 from $121 on reduced profit and sales estimates for each year through 2030

** Brokerage says MRK's business development effort seems to have lost momentum ahead of blockbuster cancer therapy Keytruda losing key patents in 2028

** Beyond Keytruda, MRK's growth story "has not improved convincingly" despite a promising pipeline of experimental treatments, brokerage says

** MRK's price to earnings ratio (P/E), a common benchmark for valuing stocks, will trough in 2026 - two years before Keytruda loses exclusivity, TD Cowen says

** Stock has fallen 24% since late July when it first disclosed Gardasil troubles

(Reporting by Padmanabhan Ananthan)

((Padmanabhan.Ananthan@thomsonreuters.com;))