merck  co inc mrk said tuesday that it will stop a clinical trial evaluating keytruda with astrazenecas azn azn lynparza in advanced prostate cancer patients because the combination therapy doesnt work the company said the drugs did not show an improvement in overall survival which is one of the trials primary endpoints the companies will continue to test the keytrudalynparza combination in patients with other types of cancers the food and drug administration last week approved lynparza as a treatment for some people with earlystage breast cancer it was initially approved to treat ovarian cancer keytruda has been approved to treat several types of cancer and is mercks topselling drug bringing in 172 billion in sales in 2021 mercks stock is up 15 so far this year while the broader sp 500 spx has declined 124