Lah Ti Dar has been ruled out of the Investec Oaks at Epsom.
The unbeaten daughter of Dar Re Mi was the general ante-post favourite for the Classic, but she has returned an unsatisfactory blood test.
Trainer John Gosden told Press Association Sport: “It was a routine blood sample, but it was not to our satisfaction.
“Therefore she will not be able to work this weekend in preparation for the Oaks, so in view of that she will not be running at Epsom.”
Lah Ti Dar, owned by Lord Lloyd-Webber, has won her two career starts by an aggregate distance of nine and a quarter lengths and will now head to Royal Ascot.
Gosden said: “I’ll have to let that come right and hopefully it will be the Ribblesdale at Ascot now.
“It’s incredible bad luck for the owners it being the Oaks again. The mother (Dar Re Mi), her sister (So Mi Dar) and now another one, but that is the way it goes.
“They are fantastic owner-breeders and fully understand the need to do what is right for the filly.”