Pharmacokinetics of CAMPATH-1H: assay development and validation

CAMPATH-1H is a humanised monoclonal antibody against the CD52 antigen which is being developed for treatment of chronic lymphocytic leukaemia (CLL), autoimmune disease and prevention of transplant rejection. Measurement of antibody serum levels is important for optimising dose regimens but difficult owing to the low concentration compared with normal human IgG.

After consideration of various methods, a suitable assay was developed based on indirect immunofluorescence. Test samples were incubated with target cells (HUT-78, a human T cell line) and the CAMPATH-1H was detected by binding of a fluorescent-labelled anti-human Ig using a flow cytometer. Robustness of the assay was demonstrated under a range of experimental conditions. Because of the low affinity of CAMPATH-1H, only a weak signal was seen at low concentrations. The limit of detection was 0.15 μg/ml and the limit of quantitation was 0.25 μg/ml. Since serum samples were diluted at least 1:2, the lowest concentration which can be measured in patient serum was 0.5 μg/ml. The overall precision (coefficient of variation) was ±13% and the overall accuracy (bias) was +9%. There was a low incidence of false-positive results (<2%) in normal or pre-treatment patient serum. Quantitative recovery was obtained from serum samples spiked with CAMPATH-1H and stored under a variety of conditions, including being treated at 56 °C for 30 min and frozen and thawed up to four times.

This validated assay is suitable for the measurement of CAMPATH-1H levels in clinical trials and the same principles may be applied to any other cell-binding monoclonal antibody.     

Ceftriaxione associated biliary lithiasis in newborns-report of two cases

The occurrence of biliary calculosis as a complication of the use of ceftriaxone was first described in an 18-year-old patient with chronic granulomatosis. Since then many reports have been published on this type of complication both in children and in adults, but until the present moment, this complication had never been reported in pre-term neonates.The authors describe two cases of biliary calculosis associated with the use of ceftriaxone in preterm-newborns, emphasizing that due to the frequent use of this type of antibiotic in neonatal I.C.U., routine ultrasonographic control exams should be performed to diagnose this possible complication in all neonates receiving ceftriaxone.     

Recombinant Kunitz protease inhibitory domain of the amyloid beta-protein precursor as an anticoagulant in venovenous extracorporeal circulation in rabbits

Investigations were performed to characterize a recombinant Kunitz protease inhibitory domain of the amyloid beta-protein precursor (rKPI) as anticoagulants. After a single intravenous infusion of wild type rKPI into dogs, its elimination fit a two compartment model with a t1/2alpha and t1/2beta of 5 and 77 min, respectively. Further investigations determined if a variant form of rKPI with 178-fold more potent anti-factor Xa activity (rKPI-DD135, Ki = 0.9 nM) could serve as an anticoagulant in a rabbit model of extracorporeal circulation using a venovenous shunt. A prospective investigation was initiated to compare standard heparin (n = 8) at 400 U/kg with different infusion concentrations of rKPI-DD135. After a single intravenous infusion of 1.89 mg/kg of rKPI-DD135 followed by a constant infusion at 0.003 (n = 3), 0.03 (n = 7), or 0.3 (n = 5) mg/kg/min, the anti-factor Xa activity of the animals' plasma rapidly reaches a steady state for the two lower infusion concentrations of the agent. All infusions of rKPI-DD135 prolong the activated clotting time with less variation than that seen with heparin administration. rKPI-DD135 anticoagulation does not prevent a drop in the platelet counts. Fibrinogen levels decrease only slightly when the circuit is anticoagulated with rKPI-DD135. rKPI-DD135 markedly prolongs the APTT, has little effect on the PT, and reduces plasma prekallikrein and plasminogen activation. The 0.3 mg/kg/min infusion concentration of rKPI-DD135 results in reduced deposition of 111Indium-labeled platelets on the circuit when compared to heparin. Last, after a steady state level is achieved, 60% of the plasma anti-factor Xa activity of rKPI-DD135 is eliminated within 60 min after stopping the infusion. These data show the rKPI-DD135 can provide single agent anticoagulation in a rabbit extracorporeal circuit. Development of short acting factor Xa inhibitors may be useful anticoagulants for cardiopulmonary bypass.     

Phase I study of an engineered aglycosylated humanized CD3 antibody in renal transplant rejection

BACKGROUND: The potential therapeutic benefits of CD3 monoclonal antibodies, such as OKT3, have been limited by their immunogenicity and their propensity to activate a severe cytokine release syndrome. This has constrained the clinical use of OKT3 to the treatment of acute rejection episodes of organ allografts. METHODS: We have humanized a rat CD3 antibody and created a single amino acid substitution in position 297 of the IgG1 heavy chain to prevent glycosylation and, consequently, binding of the therapeutic antibody to Fc receptors and to complement. This antibody has been given as first line antirejection therapy in nine kidney transplant recipients with biopsy-proven acute rejection episodes. RESULTS: None of the patients demonstrated any antiglobulin response nor any significant cytokine release syndrome. Seven of the nine showed evidence of resolution of their rejection, although some patients experienced re-rejection. CONCLUSIONS: These findings suggest that CD3 antibodies can be engineered to lose their toxicity while retaining their potency as immunosuppressants. Nonactivating humanized CD3 monoclonal antibodies now merit further investigation in the management of transplant patients and in therapy of autoimmune diseases.     

Electrical impedance tomography to evaluate air distribution prior to extubation in very-low-birth-weight infants: a feasibility study

OBJECTIVES:

Nasal continuous positive airway pressure is used as a standard of care after extubation in very-low-birth-weight infants. A pressure of 5 cmH₂O is usually applied regardless of individual differences in lung compliance. Current methods for evaluation of lung compliance and air distribution in the lungs are thus imprecise for preterm infants. This study used electrical impedance tomography to determine the feasibility of evaluating the positive end-expiratory pressure level associated with a more homogeneous air distribution within the lungs before extubation.

METHODS:

Ventilation homogeneity was defined by electrical impedance tomography as the ratio of ventilation between dependent and non-dependent lung areas. The best ventilation homogeneity was achieved when this ratio was equal to 1. Just before extubation, decremental expiratory pressure levels were applied (8, 7, 6 and 5 cmH₂0; 3 minutes each step), and the pressure that determined the best ventilation homogeneity was defined as the best positive end-expiratory pressure.

RESULTS:

The best positive end-expiratory pressure value was 6.3±1.1 cmH₂0, and the mean continuous positive airway pressure applied after extubation was 5.2±0.4 cmH₂0 (p = 0.002). The extubation failure rate was 21.4%. X-Ray and blood gases after extubation were also checked.

CONCLUSION:

This study demonstrates that electrical impedance tomography can be safely and successfully used in patients ready for extubation to suggest the best ventilation homogeneity, which is influenced by the level of expiratory pressure applied. In this feasibility study, the best lung compliance was found with pressure levels higher than the continuous positive airway pressure levels that are usually applied for routine extubation.     

Comparison of static friction with self-ligating,modified slot design and conventional brackets

Objective

To compare the static frictional forces generated at the bracket/wire interface of stainless steel brackets with different geometries and angulations, combined with orthodontic wires of different diameters.

Material and Methods

The frictional forces were evaluated with three different types of metal brackets: a passive self-ligating (SmartClip^TM, 3M/Unitek, Monrovia, USA), with a modified slot design (Mini Uni Twin^TM, 3M/Unitek, Monrovia, USA) and conventional (Kirium, Abzil, São José do Rio Preto, Brazil). The samples were mounted in a testing device with three different angulations and tested with 0.014" and 0.018" stainless steel wires (American Orthodontics, Sheboygan, USA). The static frictional force was measured using a universal testing machine (DL 500, EMIC^®, São José dos Pinhais, Brazil) with a crosshead speed of 1 mm/min. Statistical analysis was performed by two-way ANOVA followed by Bonferroni''s post hoc test.

Results

There was a significant difference (p<0.05) in static friction when the three types of brackets were tested with the same wire size. The wire diameter influenced friction only when the brackets had a 10º angulation (p<0.05). The angulation influenced friction (p<0.05) when the brackets were associated with a 0.018" wire.

Conclusion

Brackets with a modified slot design showed intermediate static frictional force values between the conventional and self-ligating brackets tested.