Mallinckrodt, a Dublin-based global specialty biopharmaceutical company, and The Gores Group, a global investment firm, have entered into a definitive agreement under which a subsidiary of Mallinckrodt will acquire Therakos, a West Chester, Pa.-based immunotherapy company, for about $1.3 billion. Subject to customary closing conditions, the transaction will close by the end of 2015.

Therakos is a global provider of autologous immune cell therapy delivered through extracorporeal photopheresis (ECP), and is focused on providing treatment platforms that harness patients’ immune systems to fight disease. Therakos Photopheresis is approved by the FDA for the palliative treatment of the skin manifestations of cutaneous T-cell lymphoma (CTCL) in persons who have not been responsive to other forms of treatment. Outside the U.S., Therakos Photopheresis also is broadly approved for ECP, and used by physicians globally in immune-modulating applications in a variety of conditions including CTCL, graft versus host disease, Crohn’s disease, solid organ transplants and other diseases.

Therakos therapeutic platforms, including the latest generation Therakos CELLEX Photopheresis System, are the only approved, fully integrated systems for administering autologous immune cell therapy through ECP. Used by academic medical centers, hospitals and treatment centers in more than 25 countries, Therakos systems have been used to deliver over 1 million photopheresis treatments globally.

“This transaction demonstrates our ongoing commitment to building a strong, highly profitable hospital growth business as we build and diversify Mallinckrodt’s Specialty Brands portfolio,” said Mark Trudeau, president and chief executive officer of Mallinckrodt. “With this expansion into immunotherapy, we add to our footprint of nuclear medicine, pain management and respiratory neonatal critical care, broadening our touch points in hospitals and further expanding our portfolio with innovative therapies.”

The Gores Group acquired Therakos from Ortho-Clinical Diagnostics, a former subsidiary of Johnson & Johnson, in December 2012.