Kolltan Pharmaceuticals (New Haven, CT) Kolltan developed anti-cancer therapeutics targeting receptor tyrosine kinases (RTKs), beginning with the work of the lab of Dr. Joseph Schlessinger, chair of Pharmacology at Yale. Dr. Schlessinger previously co-founded SUGEN and Plexxikon. Kolltan initiated clinical trials for its first drug, licensed from MedImmune, while developing a substantial pipeline of other programs. Elm Street participated in the Series A and Series D preferred stock financings of the company. Co-investors included Fidelity, KLP Enterprises, Gilead Sciences, and Auven Therapeutics. In November, 2016, Kolltan was acquired by public company Celldex (NASDAQ: CLDX).