** Shares of drug developer Arvinas ARVN.O fall 3% to $6.98

** Brokerage Leerink lowers ARVN's PT to $9 from $10; cuts rating to "market perform" from "outperform"

** Leerink cuts ARVN rating due to pending visibility on whether it can unlock "vepdegestrant's fundamental value and create a compelling investment thesis"

** ARVN and Pfizer's PFE.N experimental treatment, vepdegestrant, delayed progression of breast cancer by more than three months compared to AstraZeneca's AZN.L Faslodex in patients with ESR1 mutations

** Commitment from PFE in developing vepdegestrant combinations remains uncertain, and it is unlikely another partnership strategy could materialize - Leerink

** New rating reflects uncertainties on the market opportunity and path forward around vepdegestrant as well as the early stage of the pipeline - brokerage

** ARVN has fallen 62.4% YTD, as of last close

(Reporting by Juby Babu in Mexico City)

((Juby.Babu@thomsonreuters.com;))