FRANKFURT (Reuters) - Merck KGaA and Pfizer's cancer drug Bavencio could not be shown to improve survival in lung cancer patients that had previously undergone unsuccessful chemotherapy, Merck said.

The results revealed on Thursday mark another setback for a drug that is a late starter in the rapidly evolving field of cancer immunotherapies.

Merck shares turned negative following the news, trading 1.1 percent lower.

(Reporting by Ludwig Burger; Editing by Edward Taylor)