Eli Lilly (LLY) - Get Report   are falling Monday despite the fact that the drug company announced that its experimental cancer drug shrank tumors in nearly 70% of advanced lung cancer patients whose tumors carried specific abnormalities in the RET gene. 

RET abnormalities occur in about 2% of non-small cell lung cancers, between 10% and 20% of papillary thyroid cancers and about 60% of medullary thyroid cancers. 

Eli Lilly acquired the drug, LOXO-292, as part of its $8 billion acquisition of Loxo Oncology in January. 

"We're very excited to partner with Loxo Oncology to continue to accelerate this important medicine. In two and half years, Loxo Oncology advanced this molecule from first human dose to submission ready data, demonstrating the power of precision oncology to rapidly translate scientific discovery into treatments for patients," said Annie White, president of Lily Oncology. 

About 68% of patients treated in the drug's trial reported shrinkage of 30% or more. Of the 11 patients whose cancers had spread to the brain, 10 saw significant tumor shrinkage of 30% or more. 

Eli Lilly shares were falling 0.7% to $113.28 in trading Monday.