Merck, Daiichi pull US application for 'guided missile' therapy for lung cancer

May 29 (Reuters) - Merck MRK.N and Japan-based Daiichi Sankyo 4568.T have withdrawn their U.S. application for an experimental lung cancer treatment after it failed to prolong the lives of patients in a late-stage study, the companies said on Thursday.

The treatment, patritumab deruxtecan, belongs to a class of targeted cancer therapies called antibody drug conjugates (ADC) that work like "guided missiles" by killing tumor cells while leaving healthy ones unharmed.

Patritumab deruxtecan is one of the three lucrative "guided missile" therapies that Merck has been working on with Daiichi in an effort to offset the loss of exclusivity for its top-selling cancer drug Keytruda.

The therapy failed the secondary goal of the study as it did not improve overall survival, defined as the length of time patients lived from the start of treatment. However, it met the main goal of helping delay progression of the cancer last year.

Patritumab deruxtecan and two other ADCs - ifinatamab deruxtecan and raludotatug deruxtecan - were part of Merck's up to $22 billion joint development and commercialization deal with Daiichi signed in 2023.

The companies said on Thursday they were conducting further analyses to better identify lung cancer patients that may benefit from patritumab deruxtecan.

The U.S. Food and Drug Administration had declined to approve the therapy last year due to issues with a third-party manufacturing facility.

The companies had sought approval for the drug to treat non-small cell lung cancer in patients who have failed two or more prior lines of therapy and who had a mutation in the EGFR gene that leads to abnormal cell growth.

EGFR-positive lung cancer represents about 10% to 15% of lung cancers in the United States, according to the American Lung Association.

Johnson & Johnson's JNJ.N Rybrevant and AstraZeneca's AZN.L Tagrisso are currently approved in the U.S. for EGFR-mutated non-small cell lung cancer.