Noxopharm Limited announced that the U.S. Patent Office has allowed patent claims relating to the use of a combination of Veyonda and radiotherapy, including external beam radiotherapy (EBRT), with the purpose of generating abscopal responses in patients with metastatic prostate cancer. These claims are fundamental to helping secure the commercial success of the Company's DARRT (Direct and Abscopal Response to Radiotherapy) therapy involving a combination of Veyonda and low-dose EBRT. DARRT therapy is a form of immuno-oncology treatment. It involves the delivery of a short course of a low dose of radiotherapy to a single tumour in the body of a patient with metastatic disease. The aim is to trigger a local immune response in the irradiated tumour that spills over into an all-of-body immune response resulting in the resolution of all (complete response) or some (partial response) of the other tumours in the body. Most solid cancers, including the common prostate, breast and colorectal cancers, have proved to be overwhelmingly resistant to immuno-oncology (IO) treatments to date. This includes immunecheckpoint inhibitors and CAR-T cell therapy. Against that background, the Company's DARRT-1 study already has delivered a 25% partial abscopal response rate in men with late-stage prostate cancer (ASX announcement 1 June 2020), something that the Company is confident can be repeated in other forms of solid cancer. Compared to current IO treatments, the abscopal response is substantially better tolerated, potentially effective across a broader spectrum of cancer types, considerably more affordable, and more accessible. However, the challenge remains developing a method of lifting the abscopal response rate to a level where it will be accepted as a mainstream treatment. Idronoxil, the active ingredient in Veyonda, meets two putative key prerequisites for an abscopal response: i. the need to augment the local radiation-induced immune response by blocking autophagic clearance of mitochondrial DNA fragments following irradiation (ASX announcement 13 November 2020); ii. the need to facilitate the entry of activated immune cells into non-irradiated tumours (the so-called COLD to HOT tumour effect) (ASX announcement 18 November 2020). Compared to the DARRT-1 trial, patients in the multi-national Phase 2 DARRT-2 trial will receive considerably higher Veyonda doses as well as an increased number of Veyonda treatment cycles. DARRT-2 currently is preparing to enrol patients with late-stage prostate, breast and lung cancer. The patent application number is US 16/091706 and will be in force until at least 6 April 2037. This is just the seventh known patent issued by the U.S. Patent Office in the field of abscopal responses. Only two of the other six patents cite clinical examples, and none of those six patents involve technologies related in any way to the Noxopharm patent. The significance of patent grant lies in providing Noxopharm with an exclusive market position in the U.S. should the DARRT treatment of Veyonda plus low-dose radiotherapy be approved for use in the treatment of prostate cancers. While the Company's initial focus is on the use of DARRT therapy in late-stage prostate cancer, the Company sees the DARRT concept potentially applicable to early-stage disease where radiotherapy remains a standard form of treatment. With approximately 250,000 men diagnosed each year in the U.S. with prostate cancer, it is understandable that deals for new prostate cancer treatments in recent years have included multi-billion dollar corporate transactions.