Randomised trial of clazosentan, an endothelin receptor antagonist, in patients with aneurysmal subarachnoid hemorrhage undergoing surgical clipping (CONSCIOUS-2)

We report here results of a randomized, double-blind, placebo-controlled study ( http://www.ClinicalTrials.gov , NCT00558311) that investigated the effect of clazosentan (5 mg/h, n = 768) or placebo (n = 389) administered for up to 14 days in patients with aneurysmal subarachnoid hemorrhage (SAH) repaired by surgical clipping. The primary endpoint was a composite of all-cause mortality, new cerebral infarction or delayed ischemic neurological deficit due to vasospasm, and rescue therapy for vasospasm. The main secondary endpoint was the Glasgow Outcome Scale Extended (GOSE), which was dichotomized. Twenty-one percent of clazosentan- compared to 25% of placebo-treated patients met the primary endpoint (relative risk reduction [RRR] [95% CI]: 17% [-4% to 33%]; p = 0.10). Poor outcome (GOSE score ≤ 4) occurred in 29% of clazosentan- and 25% of placebo-treated patients (RRR: -18% [-45% to 4%]; p = 0.10). In prespecified subgroups, mortality/vasospasm-related morbidity was reduced in clazosentan-treated patients by 33% (8-51%) in poor WFNS (World Federation of Neurological Surgeons) grade (≥III) and 25% (5-41%) in patients with diffuse, thick SAH. Lung complications, anemia and hypotension occurred more frequently with clazosentan. Mortality (week 12) was 6% in both groups. The results showed that clazosentan nonsignificantly decreased mortality/vasospasm-related morbidity and nonsignificantly increased poor functional outcome in patients with aneurysmal SAH undergoing surgical clipping.

Targeted radiotherapy of prostate cancer with a gastrin-releasing peptide receptor antagonist is effective as monotherapy and in combination with rapamycin

UNLABELLED The gastrin-releasing peptide receptor (GRPr) is overexpressed in prostate cancer and is an attractive target for radionuclide therapy. In addition, inhibition of the protein kinase mammalian target of rapamycin (mTOR) has been shown to sensitize various cancer cells to the effects of radiotherapy. METHODS To determine the effect of treatment with rapamycin and radiotherapy with a novel (177)Lu-labeled GRPr antagonist ((177)Lu-RM2, BAY 1017858) alone and in combination, in vitro and in vivo studies were performed using the human PC-3 prostate cancer cell line. PC-3 cell proliferation and (177)Lu-RM2 uptake after treatment with rapamycin were assessed in vitro. To determine the influence of rapamycin on (177)Lu-RM2 tumor uptake, in vivo small-animal PET studies with (68)Ga-RM2 were performed after treatment with rapamycin. To study the efficacy of (177)Lu-RM2 in vivo, mice with subcutaneous PC-3 tumors were treated with (177)Lu-RM2 alone or after pretreatment with rapamycin. RESULTS Stable expression of GRPr was maintained after rapamycin treatment with doses up to 4 mg/kg in vivo. Monotherapy with (177)Lu-RM2 at higher doses (72 and 144 MBq) was effective in inducing complete tumor remission in 60% of treated mice. Treatment with 37 MBq of (177)Lu-RM2 and rapamycin in combination led to significantly longer survival than with either agent alone. No treatment-related toxicity was observed. CONCLUSION Radiotherapy using a (177)Lu-labeled GRPr antagonist alone or in combination with rapamycin was efficacious in inhibiting in vivo tumor growth and may be a promising strategy for treatment of prostate cancer.

Positron emission tomography (PET) imaging of prostate cancer with a gastrin releasing peptide receptor antagonist - from mice to men

UNLABELLED Ex vivo studies have shown that the gastrin releasing peptide receptor (GRPr) is overexpressed on almost all primary prostate cancers, making it a promising target for prostate cancer imaging and targeted radiotherapy. METHODS Biodistribution, dosimetry and tumor uptake of the GRPr antagonist ⁶⁴Cu-CB-TE2A-AR06 [(⁶⁴Cu-4,11-bis(carboxymethyl)-1,4,8,11-tetraazabicyclo(6.6.2)hexadecane)-PEG₄-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-LeuNH₂] were studied by PET/CT in four patients with newly diagnosed prostate cancer (T1c-T2b, Gleason 6-7). RESULTS No adverse events were observed after injection of ⁶⁴Cu-CB-TE2A-AR06. Three of four tumors were visualized with high contrast [tumor-to-prostate ratio > 4 at 4 hours (h) post injection (p.i.)], one small tumor (T1c, < 5% tumor on biopsy specimens) showed moderate contrast (tumor-to-prostate ratio at 4 h: 1.9). Radioactivity was cleared by the kidneys and only the pancreas demonstrated significant accumulation of radioactivity, which rapidly decreased over time. CONCLUSION ⁶⁴Cu-CB-TE2A-AR06 shows very favorable characteristics for imaging prostate cancer. Future studies evaluating ⁶⁴Cu-CB-TE2A-AR06 PET/CT for prostate cancer detection, staging, active surveillance, and radiation treatment planning are necessary.

Radiolabelled GLP-1 receptor antagonist binds to GLP-1 receptor-expressing human tissues.

PURPOSE Radiolabelled glucagon-like peptide 1 (GLP-1) receptor agonists have recently been shown to successfully image benign insulinomas in patients. For the somatostatin receptor targeting of tumours, however, it was recently reported that antagonist tracers were superior to agonist tracers. The present study therefore evaluated various forms of the (125)iodinated-Bolton-Hunter (BH)-exendin(9-39) antagonist tracer for the in vitro visualization of GLP-1 receptor-expressing tissues in rats and humans and compared it with the agonist tracer (125)I-GLP-1(7-36)amide. METHODS Receptor autoradiography studies with (125)I-GLP-1(7-36)amide agonist or (125)I-BH-exendin(9-39) antagonist radioligands were performed in human and rat tissues. RESULTS The antagonist (125)I-BH-exendin(9-39) labelled at lysine 19 identifies all human and rat GLP-1 target tissues and GLP-1 receptor-expressing tumours. Binding is of high affinity and is comparable in all tested tissues in its binding properties with the agonist tracer (125)I-GLP-1(7-36)amide. For comparison, (125)I-BH-exendin(9-39) with the BH labelled at lysine 4 did identify the GLP-1 receptor in rat tissues but not in human tissues. CONCLUSION The GLP-1 receptor antagonist exendin(9-39) labelled with (125)I-BH at lysine 19 is an excellent GLP-1 radioligand that identifies human and rat GLP-1 receptors in normal and tumoural tissues. It may therefore be the molecular basis to develop suitable GLP-1 receptor antagonist radioligands for in vivo imaging of GLP-1 receptor-expressing tissues in patients.

Copper-64 Labeled Macrobicyclic Sarcophagine Coupled to a GRP Receptor Antagonist Shows Great Promise for PET Imaging of Prostate Cancer

The gastrin-releasing peptide receptor (GRPr) is an important molecular target for the visualization and therapy of tumors and can be targeted with radiolabeled bombesin derivatives. The present study aims to develop statine-based bombesin receptor antagonists suitable for labeling with 64Cu for imaging by positron emission tomography (PET). The potent GRPr antagonist D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 was conjugated to the sarcophagine (3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane=Sar) derivative 5-(8-methyl-3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid (MeCOSar) via PEG4 (LE1) and PEG2 (LE2) spacers and radiolabeled with 64Cu2+ with >95% yield and specific activities of about 100 MBq/nmol. Both Cu(II) conjugates have high affinity for GRPr (IC50: natCu-LE1, 1.4±0.1 nM; natCu-LE2, 3.8±0.6 nM). The antagonistic properties of both conjugates were confirmed by Ca2+-flux measurements. Biodistribution studies of Cu-64-LE1 exhibited specific targeting of the tumor (19.6±4.7% IA/g at 1 h p.i.) and GRPr-positive organs. Biodistribution and PET images at 4 and 24 h postinjection showed increasing tumor-to-background ratios with time. This was illustrated by the acquisition of PET images showing high tumor-to-normal tissue contrast. This study demonstrates the high affinity of the MeCOSar-PEGx-bombesin conjugates to GRPr. The stability of 64Cu complexes of MeCOSar, the long half-life of 64Cu, and the suitable biodistribution profile of the 64Cu-labeled peptides lead to PET images of high contrast suitable for potential translation into the clinic.

A T cell receptor antagonist peptide induces T cells that mediate bystander suppression and prevent autoimmune encephalomyelitis induced with multiple myelin antigens

Experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) residues 139–151 (HSLGKWLGHPDKF) can be prevented by treatment with a T cell receptor (TCR) antagonist peptide (L144/R147) generated by substituting at the two principal TCR contact residues in the encephalitogenic peptide. The TCR antagonist peptide blocks activation of encephalitogenic Th1 helper cells in vitro, but the mechanisms by which the antagonist peptide blocks EAE in vivo are not clear. Immunization with L144/R147 did not inhibit generation of PLP-(139–151)-specific T cells in vivo. Furthermore, preimmunization with L144/R147 protected mice from EAE induced with the encephalitogenic peptides PLP-(178–191) and myelin oligodendrocyte protein (MOG) residues 92–106 and with mouse myelin basic protein (MBP). These data suggest that the L144/R147 peptide does not act as an antagonist in vivo but mediates bystander suppression, probably by the generation of regulatory T cells. To confirm this we generated T cell lines and clones from animals immunized with PLP-(139–151) plus L144/R147. T cells specific for L144/R147 peptide were crossreactive with the native PLP-(139–151) peptide, produced Th2/Th0 cytokines, and suppressed EAE upon adoptive transfer. These studies demonstrate that TCR antagonist peptides may have multiple biological effects in vivo. One of the principal mechanisms by which these peptides inhibit autoimmunity is by the induction of regulatory T cells, leading to bystander suppression of EAE. These results have important implications for the treatment of autoimmune diseases where there are autopathogenic responses to multiple antigens in the target organ.

Preferential exclusion of sucrose from recombinant interleukin-1 receptor antagonist: Role in restricted conformational mobility and compaction of native state

Understanding the mechanism for sucrose-induced protein stabilization is important in many diverse fields, ranging from biochemistry and environmental physiology to pharmaceutical science. Timasheff and Lee [Lee, J. C. & Timasheff, S. N. (1981) J. Biol. Chem. 256, 7193–7201] have established that thermodynamic stabilization of proteins by sucrose is due to preferential exclusion of the sugar from the protein’s surface, which increases protein chemical potential. The current study measures the preferential exclusion of 1 M sucrose from a protein drug, recombinant interleukin 1 receptor antagonist (rhIL-1ra). It is proposed that the degree of preferential exclusion and increase in chemical potential are directly proportional to the protein surface area and that, hence, the system will favor the protein state with the smallest surface area. This mechanism explains the observed sucrose-induced restriction of rhIL-1ra conformational fluctuations, which were studied by hydrogen–deuterium exchange and cysteine reactivity measurements. Furthermore, infrared spectroscopy of rhlL-1ra suggested that a more ordered native conformation is induced by sucrose. Electron paramagnetic resonance spectroscopy demonstrated that in the presence of sucrose, spin-labeled cysteine 116 becomes more buried in the protein’s interior and that the hydrodynamic diameter of the protein is reduced. The preferential exclusion of sucrose from the protein and the resulting shift in the equilibrium between protein states toward the most compact conformation account for sucrose-induced effects on rhIL-1ra.

Functions of interleukin 1 receptor antagonist in gene knockout and overproducing mice.

Interleukin 1 receptor antagonist (IL-1ra) is a cytokine whose only known action is competitive inhibition of the binding of interleukin 1 (IL-1) to its receptor. To investigate the physiological roles of endogenously produced IL-1ra, we generated mice that either lack IL-1ra or overproduce it under control of the endogenous promoter. Mice lacking IL-1ra have decreased body mass compared with wild-type controls. They are more susceptible than controls to lethal endotoxemia but are less susceptible to infection with Listeria monocytogenes. Conversely, IL-1ra overproducers are protected from the lethal effects of endotoxin but are more susceptible to listeriosis. Serum levels of IL-1 following an endotoxin challenge are decreased in IL-1ra nulls and increased in IL-1ra overproducers in comparison to controls. These data demonstrate critical roles for endogenously produced IL-1ra in growth, responses to infection and inflammation, and regulation of cytokine expression.

Suppression of experimental arthritis by gene transfer of interleukin 1 receptor antagonist cDNA.

Restoration of the impaired balance between pro- and antiinflammatory cytokines should provide effective treatment of rheumatoid arthritis. Gene therapy has been proposed as an approach for delivery of therapeutic proteins to arthritic joints. Here, we examined the efficacy of antiinflammatory gene therapy in bacterial cell wall-induced arthritis in rats. Human secreted interleukin 1 receptor antagonist (sIL-1ra) was expressed in joints of rats with recurrent bacterial cell wall-induced arthritis by using ex vivo gene transfer. To achieve this, primary synoviocytes were transduced in culture with a retroviral vector carrying the sIL-1ra cDNA. Transduced cells were engrafted in ankle joints of animals prior to reactivation of arthritis. Animals in control groups were engrafted with synoviocytes transduced with lacZ and neo marker genes. Cells continued to express transferred genes for at least 9 days after engraftment. We found that gene transfer of sIL-1ra significantly suppressed the severity of recurrence of arthritis, as assessed by measuring joint swelling and by the gross-observation score, and attenuated but did not abolish erosion of cartilage and bone. The effect of intraarticularly expressed sIL-1ra was essentially local, as there was no significant difference in severity of recurrence between unengrafted contralateral joints in control and experimental groups. We estimate that locally expressed sIL-1ra was about four orders of magnitude more therapeutically efficient than systemically administered recombinant sIL-1ra protein. These findings provide experimental evidence for the feasibility of antiinflammatory gene therapy for arthritis.

Identification of receptor-binding domains on human interleukin 5 and design of an interleukin 5-derived receptor antagonist.

A detailed structure-function analysis of human interleukin 5 (hIL5) has been performed. The hIL5 receptor is composed of two different polypeptide chains, the alpha and beta subunits. The alpha subunit alone is sufficient for ligand binding, but association with the beta subunit leads to a 2- to 3-fold increase in binding affinity. The beta chain is shared with the receptors for IL3 and granulocyte/macrophage-colony-stimulating factor--hence the descriptor beta C (C for common). All hIL5 mutants were analyzed in a solid-phase binding assay for hIL5R alpha interaction and in a proliferation assay using IL5-dependent cell lines for receptor-complex activation. Most residues affecting binding to the receptor alpha subunit were clustered in a loop connecting beta-strand 1 and helix B (mutants H38A, K39A, and H41A), in beta-strand 2 (E89A and R91A; weaker effect for E90A) and close to the C terminus (T109A, E110A, W111S, and I112A). Mutations at one position, E13 (Glu13), caused a reduced activation of the hIL5 receptor complex. In the case of E13Q, only 0.05% bioactivity was detected on a hIL5-responsive subclone of the mouse promyelocytic cell line FDC-P1. Moreover, on hIL5-responsive TF1 cells, the same mutant was completely inactive and proved to have antagonistic properties. Interactions of this mutant with both receptor subunits were nevertheless indistinguishable from those of nonmutated hIL5 by crosslinking and Scatchard plot analysis of transfected COS-1 cells.