Padlock Therapeutics Accelerates Pipeline Development Through Agreement with GSK

-- Creates Industry-Leading R&D Effort Focused on Creating PAD Inhibitors for the

Treatment of Autoimmune Diseases –

CAMBRIDGE, Mass. – May 28, 2015 – Padlock Therapeutics, a biotechnology company dedicated to creating new medicines for destructive autoimmune diseases, today announced that the company has entered into an agreement to license intellectual property and a collection of assets targeted at protein-arginine deiminases (PADs) from GSK. Padlock plans to use these assets to expand the breadth and depth of its proprietary chemistry portfolio in an effort to create fundamentally new treatments for autoimmune disease by targeting the PAD enzymes. Clinical applications under evaluation at Padlock include rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis.

Under the terms of the agreement, Padlock will receive exclusive rights to a package of assets including intellectual property, selected compounds in several chemical series, assays, data and crystal structures developed by GSK scientists. In return, GSK will receive an undisclosed equity grant and board observer rights. Per the transaction, GSK receives no option to license or acquire Padlock assets nor does Padlock owe any future milestone or royalty payments.

"Since our founding just over a year ago, the Padlock team has achieved numerous research milestones as we build our PAD enzyme chemistry engine," said Michael Gilman, Ph.D., Founder and Chief Executive Officer at Padlock. "We are thrilled to add GSK's assets and know-how to our platform. We believe that the compounds, methods, and data obtained from GSK, combined with our own internal expertise and proprietary chemistry, create an industry-leading R&D effort focused on the PAD enzymes and will expedite getting PAD-directed medicines to patients with serious autoimmune diseases."

About PAD Enzymes and Autoimmune Disease

Padlock's founding hypothesis is that autoantigens drive the initiation and development of autoimmunity by perpetuating, maturing, and intensifying a destructive autoimmune attack on healthy tissue. Autoantigens also drive the formation and deposition of immune complexes, which account for much of the morbidity and mortality in patients with autoimmune disease. In patients where the source of autoantigen is known, extinguishing autoantigen production offers the potential to impact disease progression and intensity without affecting systemic immunity. The protein-arginine deiminases (PADs) are a family of enzymes that post-translationally modify arginine side chains on proteins to the related amino acid citrulline. In some patients, these citrullinated proteins are immunogenic – in other words, in these patients PAD enzymes produce the autoantigens that drive disease. Inhibiting PADs in these patients may provide an innovative, alternative approach to treating patients who suffer from rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, and other destructive autoimmune diseases.

About Padlock

Padlock Therapeutics is a private, Cambridge, Massachusetts-based biotechnology company dedicated to creating new medicines to treat destructive autoimmune diseases. The company leverages breakthrough science on the biochemistry of the protein-arginine deiminase (PAD) enzymes, the role of PADs in generating autoantigens, and the role of protein citrullination in disease to develop novel drugs targeting the PAD enzymes. Padlock was founded by scientists at The Scripps Research Institute in conjunction with Atlas Venture. Padlock's Series A investors include Atlas VentureJohnson & Johnson Innovation – JJDC, Inc.MS Ventures, and Index Ventures. For more information on Padlock, visit