Eli Lilly and Co. said on Tuesday a midstage study of a brain cancer drug helped shrink tumors with minimal side effects.

Lilly said the compound, enzastaurin, is the first targeted agent to enter into late-stage clinical development. The pill is aimed at stopping blood flow to tumors in glioblastoma, a type of brain cancer that affects the central nervous system.

The phase II study included 92 patients with recurrent brain tumors who had failed more than one round of chemotherapy.

Preliminary results from the study showed 20 percent to 25 percent of patients responded to the drug, with the most common side effect being thrombocytopenia, or low platelet count.

Lilly said final results from the mid-stage study are expected by 2006, and the company is designing a late-stage study of the drug to confirm its safety and effectiveness in a bigger pool of patients.