GSK announced that dosing has commenced in a phase III study evaluating sirukumab, a human anti-interleukin (IL)-6 monoclonal antibody, for the treatment of patients with giant cell arteritis (GCA).

GCA, a disease characterised by inflammation of large and medium sized arteries predominantly in the head and neck, occurs in people aged 50 years or over. Patients typically experience severe headache, visual loss, jaw and muscular pain and may be at risk of permanent sight loss if not treated promptly. The mainstay of treatment is with high doses of steroids to rapidly reduce the inflammation and prevent sight loss. In order to minimise side effects that can occur with high doses and long term use, steroids are tapered after remission to lower maintenance doses. However, disease relapse is common during steroid taper and remission with steroids is often followed by subsequent relapse requiring repeat high dose treatment. As a result over 70% of patients experience significant side effects from steroids such as osteoporosis, cataract, hypertension and type 2 diabetes mellitus.

The phase III randomised, double-blind, placebo-controlled study (named the “SIRRESTA” study) will evaluate the efficacy and safety of two subcutaneous doses of sirukumab (100mg every two weeks and 50mg every four weeks) with a pre-specified tapering dose of prednisone for the treatment of GCA.  This approach will specifically answer whether treatment with sirukumab can reduce the duration of steroid treatment typical in clinical practice. The study comprises two distinct parts: a 52 week double-blind treatment phase (Part A) and a 104 week long term extension phase (Part B).  The primary endpoint of the study is the proportion of patients that achieve sustained remission.

Paul-Peter Tak, senior vice president, GSK Immuno-Inflammation R&D, said: “The use of high dose steroids to treat giant cell arteritis can cause severe side effects with prolonged use. Alternative treatments are required and we believe sirukumab could be an important option for patients with this disease. The start of our study with sirukumab for GCA, which is currently under investigation for rheumatoid arthritis, marks the progress we are making to apply our knowledge of the underlying cause of a variety of immune-mediated inflammatory diseases and explore the potential of our immuno-inflammation pipeline to treat multiple conditions.”

Sirukumab is not approved as a treatment for any indication anywhere in the world.

Sirukumab is an investigational human anti-IL-6 monoclonal antibody that selectively binds with high affinity to the IL-6 cytokine, a naturally occurring protein that is believed to play a role in autoimmune conditions. It is in phase III development for rheumatoid arthritis (RA) and GCA.

As part of a collaboration with Janssen Biologics (Ireland) [Janssen], a phase III programme began in August 2012 to investigate sirukumab for the treatment of moderately to severely active RA.  The licensing and co-development collaboration agreement, which was entered into by GSK and Janssen in December 2011, gives both companies the option to investigate sirukumab for other indications beyond RA.

The phase III study investigating sirukumab for GCA is fully funded and sponsored by GSK. Janssen has the right to opt into the GCA programme at any stage of development.

Giant Cell Arteritis (GCA) is a type of vasculitis (inflammation of blood vessels) which results in inflammation of large and medium-sized arteries. The inflammation can inhibit blood flow which can cause damage to the body's organs. It is the most common form of vasculitis in the United States and Europe. In addition to the first line use of steroids, patients that relapse may also require glucocorticoid-sparing agents to help reduce the dose of steroids. Many patients experience significant side effects as a result of long term steroid treatment.