RA and limitations of current treatments
RA is a chronic autoimmune disease, characterized by inflammation and degeneration of the joints. It affects almost 1% of the adult population worldwide, with onset typically between the ages of 30 and 50 years, and with a high prevalence in women. Patients suffer from pain, stiffness, and restricted mobility due to a persistent inflammation of multiple joints, which ultimately results in irreversible damage of the joint cartilage and bone. As RA develops, the body’s immune cells perceive the body’s own protein as foreign and cells called lymphocytes react to this protein. The reaction then causes the release of cytokines, which are chemical messengers that trigger more inflammation and joint damage. The inflammation may spread to other areas in the body, ultimately causing not only joint damage but also chronic pain, fatigue, and loss of function. Inflammation has also been linked to heart disease and the risk of having a heart attack. RA nearly doubles the risk of having a heart attack within the first 10 years of being diagnosed, according to the American College of Rheumatology.
The primary goals in the treatment of RA are to control inflammation and slow or stop disease progression. Initial therapeutic approaches relied on disease-modifying anti-rheumatic drugs, or DMARDS, such as MTX and sulphasalazine. These oral drugs work primarily to suppress the immune system and, while effective in this regard, the suppression of the immune system leads to an increased risk of infections. These drugs are also associated with side effects including nausea, abdominal pain, and serious lung and liver toxicities. Further, because these drugs often take an average of 6–12 weeks to take effect, rheumatologists may also couple them with over-the-counter pain medications or non-steroidal anti-inflammatory drugs to treat the pain and inflammation. Despite these shortcomings, DMARDS are still considered first-line therapies.
The development of monoclonal antibodies and biologics represented a significant advance in RA treatment. Biologic therapies involve the use of antibodies or other proteins produced by living organisms to treat diseases. In the majority of people with arthritis, the tumor necrosis factor, or TNF, protein is present in the blood and joints in excessive amounts, thereby increasing inflammation, along with pain and swelling. Biologic therapies have been developed to address this overproduction of TNF by disrupting communication between the body’s immune cells. Thus, they block the production of TNF or are designed to attach to and destroy the body’s immune B-cells, which play a part in the pain and swelling caused by arthritis. Anti-TNFs are currently the standard of care for first- and second-line biologic therapies for RA patients who have an inadequate response to DMARDS. Since anti-TNF drugs function through a suppression of the immune system, they also lead to a significant increase in the risk of infections. In addition, all approved anti-TNFs need to be delivered by injection or intravenously, which is inconvenient and painful for some patients, and in some cases self-injection can be particularly difficult for patients who suffer joint pain and damage from RA.
Not all patients achieve sufficient clinical response or maintain clinical response to anti-TNFs over time, resulting in a need to switch or cycle to a new therapy to control their disease. Approximately one-third of RA patients do not adequately respond to anti-TNFs. In addition, anti-TNFs are associated with low rates of disease remission and the response to these agents is not typically durable. In more than 30% of this population, alternative treatment approaches are needed. A significant number of patients treated with an anti-TNF will be cycled to their second and third anti-TNF within 24 months of anti-TNF therapy initiation. Therapeutic cycling is a serious issue for patients because the efficacy of each successive drug is not known typically for several months, which contributes to progression of disease and continued irreversible structural joint damage. For RA patients who fail or for whom anti-TNFs are contra-indicated, biologics with distinct mechanism and the oral agent JAK inhibitors provide alternative treatment opportunities.
Despite these limitations, the global market for RA therapies is large and growing rapidly. The market for RA therapies across the 10 main healthcare markets was $15.6 billion in 2013 and is expected to grow in excess of $19 billion by 2023, according to a December 2014 GlobalData PharmaPoint report. Injectable, biological therapies are the largest component of this market.
There continues to be a considerable unmet need with regard to efficacy, including sustained efficacy, safety, and convenience of use with these existing first line treatments.