Degarelix therapy for prostate cancer in a real-world setting: experience from the German IQUO (Association for Uro-Oncological Quality Assurance) Firmagon® registry.

BACKGROUND: We investigated the use of the gonadotropin-releasing hormone (GnRH) antagonist degarelix in everyday clinical practice using registry data from uro-oncology practices in Germany. METHODS: Data were analysed retrospectively from the IQUO (Association for uro-oncological quality assurance) patient registry. Data were prospectively collected from all consecutive PCa patients treated with degarelix (n = 1010) in 138 uro-oncology practices in Germany between May 2009 and December 2013. RESULTS: Median overall survival had not yet been reached in the all-patient group or in subgroups who had or had not received prior hormonal therapy (HT). Cox regression analysis showed that patients who had received prior HT (n = 542) had a 58 % increased mortality risk (hazard ratio 1.58, 95 % CI 1.20-2.09) versus patients who had not (n = 468) (p = 0.001). Also, in patients who had received prior luteinizing hormone-releasing hormone (LHRH) analogue therapy (LHRH agonists or GnRH antagonists), median time to PSA progression was shorter (209 weeks) than in those who had not received prior LHRH analogues (n = 555; median PSA progression-free survival not yet reached). Degarelix was generally well tolerated. CONCLUSIONS: Degarelix was effective and well tolerated in everyday clinical practice, confirming observations from clinical studies. Patients who received prior HT appeared to have a significantly higher mortality risk.

Reformable intramolecular cross-linking of the N-terminal domain of heparin cofactor II: effects on enzyme inhibition.

The crystal structure of a heparin cofactor II (HCII)-thrombin Michaelis complex has revealed extensive contacts encompassing the N-terminal domain of HCII and exosite I of the proteinase. In contrast, the location of the N-terminal extension in the uncomplexed inhibitor was unclear. Using a disulfide cross-linking strategy, we demonstrate that at least three different sites (positions 52, 54 and 68) within the N terminus may be tethered in a reformable manner to position 195 in the loop region between helix D and strand s2A of the HCII molecule, suggesting that the N-terminal domain may interact with the inhibitor scaffold in a permissive manner. Cross-linking of the N terminus to the HCII body does not strongly affect the inhibition of alpha-chymotrypsin, indicating that the reactive site loop sequences of the engineered inhibitor variants, required for interaction with one of the HCII target enzymes, are normally accessible. In contrast, intramolecular tethering of the N-terminal extension results in a drastic decrease of alpha-thrombin inhibitory activity, both in the presence and in the absence of glycosaminoglycans. Treatment with dithiothreitol and iodoacetamide restores activity towards alpha-thrombin, suggesting that release of the N terminus of HCII is an important component of the multistep interaction between the inhibitor and alpha-thrombin.

Zinc ions promote the interaction between heparin and heparin cofactor II.

The effects of bivalent cations on heparin binding, structure, and thrombin inhibition rates of heparin cofactor II were examined. Zn(2+) - and to a lesser extent Cu(2+) and Ni(2+) - enhanced the interaction between heparin cofactor II and heparin as demonstrated by heparin affinity chromatography and surface plasmon resonance experiments. Metal chelate chromatography and increased intrinsic protein fluorescence in the presence of Zn(2+) indicated that heparin cofactor II has metal ion-binding properties. The results are compatible with the hypothesis that Zn(2+) induces a conformational change in heparin cofactor II that favors its interaction with heparin.