Immune thrombocytopenic purpura (ITP), also known as idiopathic thrombocytopenic purpura, is a blood disorder characterised by weakened functioning of clotting of blood. People with the disease have a tendency to bleed or bruise as a result of a low number platelets or thrombocytes which results from the self-destruction of platelets by body’s own immune system. Some of the risk factors for the disease include viral infection, use of certain drugs during pregnancy or other immune disorder. ITP is more common in women and children. According to the National Organization for Rare Disorders, the prevalence of the disease is 9.5 cases per 100,000 people.
Significant growth is expected in the therapeutics pipeline for ITP in the near future primarily driven by the rising demand for combination therapies due to their superior safety and efficacy profile as compared with other treatments, rising prevalence of viral diseases that are a major risk factor for ITP, favourable government regulations such as the Orphan Drug Act in the U.S. resulting in increasing research and development investments for new drug candidates for ITP.
In September 2015, Kyowa Hakko Kirin China Pharmaceutical Co. Limited initiated a Phase III clinical trial to evaluate the efficacy and safety of AMG531 (romiplostim) for injection in adult subjects with persistent or chronic primary ITP. The results of the trial are expected to come in December 2017. AMG531 is a thrombopoietin receptor agonist being evaluated in the form of an injection formulation. In March 2016, UCB Biopharma S.P.R.L. initiated a Phase II clinical trial to evaluate the safety, tolerability and efficacy of UCB7665 in subjects with primary ITP. The clinical trial is expected to be completed in June 2017. UCB7665 is a humanized and chimeric monoclonal antibody and an immunomodulator. In April 2017, S-888711 (lusutrombopag) by Shionogi Inc. completed a Phase III clinical trial for ITP. S-888711 is a thrombopoietin receptor agonists that belongs to the chemical class of thiazoles. In March 2017, arGEN-X BVBA initiated a Phase II clinical trial to evaluate the safety, efficacy and pharmacokinetics of ARGX-113 in patients with primary ITP. ARGX-113 is a monoclonal antibody which reduces the levels of pathogenic immunoglobulin G, or IgG. ARGX-113 is developed using the ABDEG technology. In September 2015, Protalex, Inc. started an open-label, dose escalation Phase I/II study of its drug candidate, PRTX-100, in adults with persistent/chronic ITP. The study is expected to be completed in June 2018. PRTX-100 is a highly-purified form of the Staphylococcal Protein A, which is an immunomodulatory protein generated by Staphylococcus aureus bacteria. PRTX-100 binds to human B-lymphocytes and macrophages and modulates immune processes pertaining to inflammation seen in autoimmune diseases. Also, Rigel Pharmaceuticals, Inc. completed and reported results from its Phase III clinical study of R788 (fostamatinib) in ITP in 2016. The company submitted a New Drug Application (NDA) to the USFDA for fostamatinib in patients with chronic or persistent ITP in April 2017. Fostamatinib inhibits Syk kinase (spleen tyrosine kinase) thereby blocking IgG receptor signalling in macrophages and B cells.
Some of the major players involved in the development of drugs for ITP include 3SBio Inc., AkaRx Inc., arGEN-X BV, Jiangsu Hengrui Medicine Co., Ltd., UCB Biopharma S.P.R.L., Kyowa Hakko Kirin China Pharmaceutical Co. Limited, Shionogi Inc., Protalex, Inc., Momenta Pharmaceuticals, Inc., Amgen Inc., Shire plc, Rigel Pharmaceuticals, Inc., Genosco, Inc.