An investor consortium led by Madison Dearborn Partners has agreed to sell Ikaria to specialty biopharmaceutical company Mallinckrodt (NYSE: MNK) in a transaction valued at roughly $2.3 billion. The deal is expected to close in early 2Q. Ikaria develops therapies and delivery systems to address the needs of critically ill infants in hospital neonatal intensive care units. Its lead product treats hypoxic respiratory failure associated with clinical or echocardiographic evidence of pulmonary hypertension. MDP acquired a majority shareholding stake at a roughly $1.6 billion valuation early last year; the company's other backers have included New Mountain Capital, 5AM Ventures, ARCH Venture Partners and Venrock.