Anti GnRH antibodies can induce castrate levels of testosterone in patients with advanced prostate cancer

D17DT consists of the GnRH decapeptide linked to diphtheria toroid. The aim of this pilot study was to assess the tolerance of D17DT and the productio n of anti-GnRH antibodies from two doses, 30 and 100 mu g, in patients with locally advanced prostate cancer. Twelve patients with histologically prov en prostate cancer in whom hormonal therapy was indicated were recruited. P atients received either 30 or 100 mu g given intramuscularly on three separ ate occasions over six weeks. Patients were followed up and blood was taken for estimation of serum testosterone, PSA and anti-GnRH antibody titre. Ov erall the drug was well tolerated, in 5 patients a significant reduction in serum testosterone and PSA was seen. Castrate levels of testosterone were achieved in 4 and maintained for up to 9 months. Patients with the highest antibody titre had the best response in terms of testosterone suppression. This study shows that it is possible to immunize a patient with prostate ca ncer against GnRH to induce castrate levels of testosterone. This state app ears to be reversible. This novel form of immunotherapy may have advantages over conventional forms of hormonal therapy and further studies are warran ted in order to try and increase the proportion of responders. (C) 2000 Can cer Research Campaign.