Evaluation of the safety and pharmacodynamics of Hematide, a novel erythropoietic agent, in a phase 1, double-blind, placebo-controlled, dose-escalation study in healthy volunteers.

Hematide is an investigational pegylated synthetic peptide that stimulates erythropoiesis in animal models and is being developed for the treatment of anemia associated with chronic renal failure and cancer. This study evaluated the safety and pharmacodynamics of single, intravenous doses (0.025, 0.05, and 0.1 mg/kg) of Hematide in 28 healthy male volunteers. All doses of Hematide were well tolerated, with safety profiles similar to those of placebo. Hematide showed a dose-dependent increase in reticulocytes. The 0.1-mg/kg dose was associated with a statistically significant increase in hemoglobin (Hgb) from baseline compared to the placebo group (13.6 +/- 3.9 g/L [1.36 +/- 0.39 g/dL] versus 3.9 +/- 3.8 g/L [0.39 +/- 0.38 g/dL]; P < .001) that was sustained for longer than 1 month. These results support phase 2 studies in patients with anemia associated with chronic kidney disease or cancer and suggest that Hematide administered as infrequently as once a month may result in a sustained elevation of Hgb levels. (Please note that Hematide is a proposed trade name; the compound does not yet have a nonproprietary name.).

Safety and immunogenicity of a booster dose of Staphylococcus aureus types 5 and 8 capsular polysaccharide conjugate vaccine (StaphVAX) in hemodialysis patients.

StaphVAX, an unadjuvanted, bivalent vaccine composed of Staphylococcus aureus (S. aureus) capsular polysaccharides (CPS) types 5 and 8 bound to the mutant non-toxic recombinant Pseudomonas aeruginosa exotoxin A (rEPA) conferred approximately 60% protection for 10 months against bacteremia caused by this pathogen in hemodialysis patients. A protective level of 80 microg/ml was estimated based upon geometric mean (GM) antibody levels at the end of the efficacy period. To extend the duration of protection conferred by StaphVAX in hemodialysis patients, recipients of the vaccine were reinjected in a randomized double-blinded, placebo-controlled study. Vaccinees received StaphVAX and a saline placebo injection 14 days apart according to the randomization schedule. The booster dose of StaphVAX was administered an average of 958 days (753-1167 days) after the first injection. There were no serious adverse reactions. Antibody levels at day 14, 28, 92, and 182 post-injection were measured by ELISA. Maximal levels of IgG anti-CPS were observed at the 28-day interval. For type 5, GM antibody levels increased from 73 microg/ml at day 0 to 162 microg/ml (P < 0.001) and for type 8 from 59 microg/ml to 133 microg/ml (P < 0.001). Anti-CPS antibody levels of approximately 80 microg/ml to type 5 and type 8 were achieved in 72.4 and 74.3% of vaccinees, respectively. There was excellent correlation between the level of anti-CPS and opsonic titer (r = 0.93). Moreover, the decline of anti-CPS antibody levels at six months was significantly less rapid than that observed from the first immunization (P < 0.001). We conclude that a booster immunization to maintain protective levels of specific antibodies for an extended period of time is feasible for patients at continuous risk for S. aureus bacteremia.

Staphylococcus aureus types 5 and 8 capsular polysaccharide-protein conjugate vaccines.

BACKGROUND: Staphylococcus aureus, the first or second most common pathogen isolated from patients, is capsulated; there are at least 12 capsular types, and types 5 and 8 comprise approximately 85% of blood. Types 5 and 8, composed of a trisaccharide repeat unit including a mannose uronic acid and 2 fucoses, are non-immunogenic. As protein conjugates, they induce opsonophagocytic antibodies that confer type-specific active and passive protection in mice. METHODS: A phase II study of patients with end-stage renal disease showed that these conjugates induced approximately one third of the immunoglobulin G antibody of healthy individuals. Increasing the dose to 100 microg of polysaccharide induced levels similar to that in healthy individuals injected with 25 microg. RESULTS: In a double-blinded randomized and controlled study of patients undergoing renal dialysis, the conjugates induced statistically significant protection against bacteremia for as long as 10 months after immunization. The estimated protective level was 80 microg Ab/mL. At re-injection approximately 2 years later, 83 of 83 recipients responded with protective levels. CONCLUSIONS: Conjugate vaccine-induced antibodies to the types 5 and 8 capsular polysaccharide antibodies of S aureus prevent bacteremia caused by this pathogen. The extent and duration of conjugate-induced immunity can be extended by re-immunization approximately 1 year later. Studies of patients undergoing cardiovascular surgery who would be immunized with the staphylococcus conjugates when they are immunologically intact are planned.

Development of StaphVAX, a polysaccharide conjugate vaccine against S. aureus infection: from the lab bench to phase III clinical trials.

Staphylococcus aureus is the most common nosocomial pathogen and is responsible for approximately one-third of hospital-acquired bacteremias. The emergence of strains with multidrug resistance, including resistance to vancomycin, the antibiotic of last resort, presents the medical community with a major public health problem. Alternative therapies, including immunotherapy, have been in development for several decades. The discovery of S. aureus capsular polysaccharides from clinical isolates, and their importance to pathogenicity via antiphagocytic activity, opened a new window of opportunity for development of vaccines and immunotherapy against this pathogen. A conjugate vaccine, StaphVAX that includes the two most prevalent capsular polysaccharides, types 5 and 8, coupled to a carrier protein efficient in promoting a Th2 response, was developed. In a recent phase III clinical study in hemodialysis patients, StaphVAX was shown to prevent S. aureus bacteremia for up to 10 months following a single immunization. The history, epidemiology, serology, and development of StaphVAX, including preclinical and clinical studies demonstrating efficacy are described in this review.

Potent inhibition of NTPase/helicase of the West Nile Virus by ring-expanded ("fat") nucleoside analogues.

A series of ring-expanded ("fat") nucleoside analogues (RENs) containing the 6-aminoimidazo[4,5-e][1,3]diazepine-4,8-dione ring system have been synthesized and screened for inhibition of NTPase/helicase of the West Nile Virus (WNV). To assess the selectivity of RENs against the viral enzymes, a truncated form of human enzyme Suv3((Delta)(1)(-)(159)) was also included in the study. Ring-expanded nucleosides 16, 17, and 19, which possess the long C(12), C(14), and C(18) side-chains, respectively, at position 6, as well as the ring-expanded heterocycle 39, which contains aralkyl substitution at position 1, were all found to have excellent profiles of activity and selectivity toward the viral versus human enzymes against the West Nile Virus (IC(50) ranging 1-10 muM). Compound 30, while being an equally potent inhibitor of WNV, was found to be somewhat less selective, whereas compound 36, which is an alpha-anomeric counterpart of 30, exhibited potent and selective inhibition of WNV (IC(50) 1-3 muM). The same compounds that showed potent inhibition of viral helicase activity completely failed to show any activity against the viral NTPase reaction even up to 500 muM. However, at concentrations >500 muM of RENs and the ATP concentrations >10 times the K(m) value of the enzyme, a significant activation of NTPase activity was observed. This activating effect underwent further dramatic enhancement (>1000%) by further increases in ATP concentration in the reaction mixture, suggesting that the viral helicase and NTPase reactions are not coupled. A tentative mechanistic model has been proposed to explain the observed results.

Ring-expanded ("fat") nucleoside and nucleotide analogues exhibit potent in vitro activity against flaviviridae NTPases/helicases, including those of the West Nile virus, hepatitis C virus, and Japanese encephalitis virus.

A series of ring-expanded ("fat") heterocycles, nucleoside and nucleotide analogues (RENs) containing the imidazo[4,5-e][1,3]diazepine ring system (9, 14, 15, 18, 24-26, 28, 31, and 33) and imidazo[4,5-e][1,2,4]triazepine ring systems (30b, 30c, 32, and 34), have been synthesized as potential inhibitors of NTPases/helicases of Flaviviridae, including the West Nile virus (WNV), hepatitis C virus (HCV), and Japanese encephalitis virus (JEV). An amino-terminal truncated form of human enzyme Suv3(delta1-159) was also included in the study so as to assess the selectivity of RENs against the viral enzymes. The analogues of RENs included structural variations at position 1 of the heterocyclic base and contained changes in both the type of sugar moieties (ribo, 2'-deoxyribo, and acyclic sugars) and the mode of attachment (alpha versus beta anomeric configuration) of those sugars to the heterocyclic base. The target RENs were biochemically screened separately against the helicase and ATPase activities of the viral NTPases/helicases. A number of RENs inhibited the viral helicase activity with IC50 values that ranged in micromolar concentrations and exhibited differential selectivity between the viral enzymes. In view of the observed tight complex between some nucleosides and RNA and/or DNA substrates of a helicase, the mechanism of action of RENs might involve their interaction with the appropriate substrate through binding to the major or minor groove of the double helix. The REN-5'-triphosphates, on the other hand, did not influence the above unwinding reaction, but instead exerted the inhibitory effect on the ATPase activity of the enzymes. The activity was found to be highly dependent upon the low concentration levels of the substrate ATP. At concentrations >500 microM of RENs and the ATP concentrations >10 times the Km value of the enzyme, a significant activation of NTPase activity was observed. This activating effect underwent further dramatic enhancement (>1000%) by further increases in ATP concentration in the reaction mixture. A tentative mechanistic model has been proposed to explain the observed results, which includes an additional allosteric binding site on the viral NTPases/helicases that can be occupied by nucleoside/nucleotide-type molecules such as RENs.

in vitro inhibition of the measles virus by novel ring-expanded ('fat') nucleoside analogues containing the imidazo[4,5-e]diazepine ring system.

The synthesis and in vitro anti-measles virus (anti-MV) activity of a class of ring-expanded ('fat') nucleoside analogues (1-4) containing the title heterocyclic ring system are reported. The target compounds were synthesized by base-catalyzed condensations of 4,5-dicarboxylic acid esters of the appropriately substituted imidazole-1-ribosides with suitably substituted guanidine derivatives. Compounds were screened for anti-MV activity in African green monkey kidney cells (CV-1), employing ribavirin as the control standard. While the parent compound 1 itself failed to show any significant antiviral activity against MV, its analogues containing hydrophobic substituents at the 2-position (2) or the 6-position (4) showed promising antiviral activity at submicromolar or micromolar concentration levels with no apparent toxicity to the host cell line. Both compounds showed higher anti-MV activity than the control drug ribavirin.

Use of a Staphylococcus aureus conjugate vaccine in patients receiving hemodialysis.

BACKGROUND: In patients with decreased resistance to infection, Staphylococcus aureus is a major cause of bacteremia and its complications. The capsular polysaccharides are essential for the pathogenesis of and immunity to S. aureus infection and are targets for vaccines. METHODS: In a double-blind trial involving patients with end-stage renal disease who were receiving hemodialysis, we evaluated the safety, immunogenicity, and efficacy of a vaccine with S. aureus type 5 and 8 capsular polysaccharides conjugated to nontoxic recombinant Pseudomonas aeruginosa exotoxin A. Between April 1998 and August 1999, 1804 adult patients at 73 hemodialysis centers were randomly assigned to receive a single intramuscular injection of either vaccine or saline. IgG antibodies to S. aureus type 5 and 8 capsular polysaccharides were measured for up to two years, and episodes of S. aureus bacteremia were recorded. Efficacy was estimated by comparing the incidence of S. aureus bacteremia in the patients who received the vaccine with the incidence in the control patients. RESULTS: Reactions to the vaccine were generally mild to moderate, and most resolved within two days. The capsular polysaccharides elicited an antibody response of at least 80 microg per milliliter (the estimated minimal level conferring protection) in 80 percent of patients for type 5 and in 75 percent of patients for type 8. The efficacy during weeks 3 to 54 was only 26 percent (P=0.23). However, between weeks 3 and 40 after vaccination, S. aureus bacteremia developed in 11 of 892 patients in the vaccine group who could be evaluated for bacteremia, as compared with 26 of 906 patients in the control group (estimate of efficacy, 57 percent; 95 percent confidence interval, 10 to 81 percent; nominal P=0.02). CONCLUSIONS: In patients receiving hemodialysis, a conjugate vaccine can confer partial immunity against S. aureus bacteremia for approximately 40 weeks, after which protection wanes as antibody levels decrease.

Novel ring-expanded nucleoside analogs exhibit potent and selective inhibition of hepatitis B virus replication in cultured human hepatoblastoma cells.

Novel ring-expanded nucleoside (REN) analogs (1-3) containing 5:7 fused ring systems as the heterocyclic base were found to be potent and selective inhibitors of hepatitis B virus (HBV) replication in cultured human hepatoblastoma 2.2.15 cells. The most active compound, 6-amino-4,5-dihydro-8H-1-(beta-D-ribofuranosyl)imidazo[4,5-e][1,3]diazepine-4,8-dione (1), inhibited the synthesis of intracellular HBV replication intermediates and extracellular virion release in 2.2.15 cells with 50% effective concentration (EC50) of 0.604 and 0.131 microM, respectively. All three compounds had no effect on the synthesis of viral ribonucleic acids (RNA) in 2.2.15 cells. These compounds also exhibited low cellular toxicity in stationary and rapidly growing cell systems.