Sounds like it's a type of immunotherapy that can work for some people:
webmd.com/vitamins/ai/ingre...
A preliminary report on the use of transfer factor for treating stage D3 hormone-unresponsive metastatic prostate cancer.
ncbi.nlm.nih.gov/pubmed/899...
Abstract
As conventional treatments are unsuccessful, the survival rate of stage D3 prostate cancer patients is poor. Reports have suggested the existence of humoral and cell-mediated immunity (CMI) against prostate cancer tumour-associated antigens (TAA). These observations prompted us to treat stage D3 prostate cancer patients with an in vitro produced transfer factor (TF) able to transfer, in vitro and in vivo, CMI against bladder and prostate TAA. Fifty patients entered this study and received one intramuscular injection of 2-5 units of specific TF monthly. Follow-up, ranging from 1 to 9 years, showed that complete remission was achieved in 2 patients, partial remission in 6, and no progression of metastatic disease in 14. The median survival was 126 weeks, higher than the survival rates reported in the literature for patients of the same stage.
I think this may be the same thing, but only available in Mexico - much more recent, 2018:
The dialyzable leukocyte extract TransferonTM inhibits tumor growth and brain metastasis in a murine model of prostate cancer.