Eli Lilly and Co. plans to use an implantable drug-delivery system made by Medtronic Inc. to precisely target patients' brains with an experimental drug for Parkinson’s disease. The two companies announced their partnership on the Parkinson’s medication Tuesday morning.

Indianapolis-based Lilly has not yet begun human trials of its drug, known as a glial cell derived neurotrophic factor, or GDNF. Lilly said in a press release that it has engineered the biotech drug to distribute more broadly than other neurotrophic agents have in previous tests. Minneapolis-based Medtronic’s system, which uses a pump and catheter, supplies a steady amount of the drug to a specific brain region over time.

Financial terms of the partnership were not disclosed.

“By collaborating with Medtronic from the earliest phase of research, we are maximizing the potential for this therapy's efficient and effective development,” said Michael L. Hutton, chief scientific officer of Lilly’s neurodegeneration team, in a prepared statement.

There is no known cure for Parkinson’s, a condition caused by the loss of brain neurons that produce dopamine, a chemical messenger key to the brain’s coordination of movement. Parkinson’s patients suffer from imbalance, tremors and muscle stiffness.

Some of the most famous victims of Parkinson’s are the former boxer Muhammad Ali and actor Michael J. Fox. They are among more than 7 million estimated Parkinson’s patients worldwide.

By injecting neurotrophic factors into the brain, scientists expect that they would strengthen existing neurons, helping them produce more dopamine, said Ros Smith, senior director of regenerative biology at Lilly. Keeping neurons functioning longer could slow progression of Parkinson’s rather than treating its symptoms, as existing therapies do.

However, because neurotrophic factors are large proteins, they don’t easily cross from the bloodstream into the brain, Smith said. But Lilly scientists hope that Medtronic’s delivery system can overcome that obstacle.

"One of the most significant challenges in delivering a biologic treatment for neurodegenerative diseases is crossing the blood brain barrier. We have extensive experience in targeted drug delivery and technology that allow delivery of therapeutic agents directly to the brain,” said Dr. Steve Oesterle, senior vice president of medicine and technology at Medtronic.