San Diego, California-based Companion Medical, a stealthy medical device startup developing a Bluetooth-connected insulin pen and connected app, has closed its second round of funding, led by Eli Lilly and Company. The funding amount was not disclosed.

Companion Medical previously raised $400,000 last year from Diamyd Medical, according to an SEC filing and a statement from the company. A representative from Lilly will join Diamyd on Companion's board of directors.

"We are very excited to have Lilly as the lead investor in our series B financing," Sean Saint, president and CEO of Companion Medical, said in a statement. "Lilly is a global leader in insulin, as well as other medicines and devices in the international diabetes space, and we look forward to their involvement in potentially bringing our device to market."

Saint is a veteran engineer of Dexcom, Medtronic, and Tandem Diabetes Care. Though the company has kept quiet about its product details, it writes on its website that it intends to improve on the insulin pump for people living with type 1 diabetes.

"While insulin pumps currently offer the best tools available, the vast majority of people with diabetes either cannot or will not use a pump," they write. "Companion is developing a superior, cost effective solution that combines the best attributes of current solutions with advanced data management technologies to address the large global market for insulin delivery systems."

Lilly's investment comes on the heels of its announcement of a new innovation center in Kendall Square in Cambridge, Massachusetts. The focus of that center will also be on drug delivery and device innovation with a particular focus on diabetes.

"Lilly is focused on delivering the broadest portfolio of diabetes treatments in the industry, including innovative delivery methods to advance the treatment of diabetes," Divakar Ramakrishnan, VP for Delivery and Device Research and Development at Lilly, who will also be heading up the new innovation center, said in a recent statement.  "Companion's smart pen and app represent innovation that could one day fill a gap for millions of people with diabetes."