Our second therapeutic candidate, XCUR17, is an SNA that targets the mRNA that encodes interleukin 17 receptor alpha, or IL-17RA, a protein that is considered essential in the initiation and maintenance of psoriasis. Although the availability of inhibitors of TNF revolutionized the systemic treatment of severe psoriasis, studies of disease pathogenesis have shifted attention to the IL-17 pathway, in which IL-17RA is a key driver of psoriasis. Our strategy is to reduce the levels of IL-17RA in the skin by topically applying XCUR17. In preclinical studies, XCUR17 inhibited IL-17RA in the keratinocytes of the skin. We filed a CTA for a Phase 1 clinical trial of XCUR17 in patients with psoriasis in Germany in the third quarter of 2017. Our CTA was approved in February 2018 and we expect the first patient in our Phase 1 clinical trial to be dosed in early 2018. We expect this clinical trial to be completed in mid-2018.
Our third therapeutic candidate, AST-008, is an SNA consisting of toll-like receptor 9, or TLR9, agonists designed for immuno-oncology applications. TLR9 agonists bind to and activate TLR9 receptors. We believe AST-008 may be used for immuno-oncology applications as a monotherapy or in combination with checkpoint inhibitors. Checkpoint inhibitors are therapeutics that prevent tumors from evading destruction by the immune system. We have observed that administration of AST-008 as a monotherapy can have anti-tumor activity in colon cancer, breast cancer, lymphoma and melanoma mouse models. We have also observed that, in preclinical studies in a variety of tumor models, AST-008 applied in combination with certain checkpoint inhibitors exhibited anti-tumor responses and survival rates that were greater than those demonstrated by checkpoint inhibitors alone. Importantly, in an anti-PD-1 antibody-resistant breast cancer mouse model, administration of AST-008 with certain anti-PD-1, or programmed death 1, antibodies restored the anti-tumor activity of these antibodies. We have also demonstrated that AST-008 was active when administered subcutaneously, intratumorally or intravenously, in both prevention and established mouse tumor models. The administration of AST-008 also produced localized as well as abscopal anti-tumor activity in mouse cancer models. Additionally, administration of AST-008 in combination with certain checkpoint inhibitors conferred adaptive immunity in breast and colon cancer mouse models. We filed a CTA for a Phase 1 clinical trial of AST-008 in the United Kingdom in the second quarter of 2017. In the third quarter of 2017, we received an authorization from the MHRA, the competent health authority of the United Kingdom, to conduct a Phase 1 clinical trial with AST-008. We began subject dosing in our Phase 1 clinical trial for AST-008 in the fourth quarter of 2017. We expect this trial to be completed in mid-2018. We ultimately plan to clinically advance AST-008 in combination with checkpoint inhibitors.
Given the extensive potential therapeutic applications for our SNA platform, we believe it is important to enter into selective partnerships to broaden the indications we can pursue and accelerate the development of new programs. To that end, on December 2, 2016, we entered into the Purdue Collaboration. We believe this collaboration exemplifies our strategy of establishing alliances with leaders with a proven track record in the development and global commercialization of treatments for patients with chronic conditions.
We believe that we have a strong intellectual property, or IP, position in the field of SNA therapeutics. As of December 31, 2017, our patent portfolio consisted of over 55 issued patents and allowed patent applications and over 135 pending patent applications. We have licensed IP from Northwestern University and have also independently filed patents to protect our IP. Our license from Northwestern University is for exclusive worldwide rights to the use of SNA technology for therapeutic applications. Any patents arising from AST-005, XCUR17 or AST-008 applications would expire by 2035, 2037, and 2034 or 2035, respectively.
We intend to build a leading nucleic acid therapeutics company based on our proprietary SNA technology. The key elements of our strategy are:
Advance therapeutics incorporating our SNA technology for the treatment of skin diseases. We filed a CTA for a Phase 1 clinical trial of XCUR17 in patients with psoriasis in Germany in the third quarter of 2017. We expect the first patient in our Phase 1 clinical trial to be dosed in early 2018. We expect this clinical trial to be completed in mid-2018.