The Federal Circuit has overturned an Indiana district court's judgement in an inventorship dispute between Eli Lilly and Aradigm Corp over a patent covering a method of aerosolized rapid-uptake delivery of insulin. Lilly had successfully sued Aradigm in seeking to have two of its scientists recognized as joint inventors on Aradigm's patent (US 5,888,477), although the district court ordered the addition of only one of the scientists, Richard DiMarchi, as inventor. However, the Federal Circuit ruled that Lilly was unable to prove that its scientists were co-inventors on the Aradigm patent.

DiMarchi is the inventor of Lilly's insulin analogue Lispro (marketed as Humalog), covered by patent US 5,514,646. Insulin molecules tend to form stable hexamers in solution, leading to a delay between injection or inhalation and therapeutic effect. Slight structural modifications in Lispro result in less self-association and more rapid therapeutic onset. The '477 patent issued to Aradigm covers the use of monomeric insulin as a means for improving the bioavailability of inhaled insulin.

Lilly claimed that Aradigm improperly appropriated information about the advantages of pulmonary delivery of Lispro from Lilly and incorrectly claimed the invention in the '477 patent exclusively as their own. In 1995 and 1996, the two companies held four meetings to discuss a possible collaboration that would take advantage of the expertise of both companies. Lilly insists that its scientists showed Aradigm the specific advantages expected from using Lispro instead of regular insulin in an aerosol device.

The Federal court agreed with Aradigm that Lilly did not present substantial evidence for the jury to determine that its scientists communicated the subject matter to Aradigm to a clear and convincing standard. No Lilly scientists testified directly that they discussed with Aradigm the use of Lispro for aerosolized delivery. The district court therefore had improperly relied on circumstantial evidence.