CTLA4-Ig-Based Bifunctional Costimulation Inhibitor Blocks CD28 and ICOS Signaling to Prevent T Cell Priming and Effector Function

CTLA4-Ig/abatacept dampens activation of naive T cells by blocking costimulation via CD28. It is an approved drug for rheumatoid arthritis but failed to deliver efficacy in a number of other autoimmune diseases. One explanation is that activated T cells rely less on CD28 signaling and use alternate coreceptors for effector function. ICOS is critical for activation of T-dependent humoral immune responses, which drives pathophysiology of IgG-mediated autoimmune diseases. In this study, we asked whether CD28 and ICOS play nonredundant roles for maintenance of T-dependent responses in mouse models. Using a hapten-protein immunization model, we show that during an ongoing germinal center response, combination treatment with CTLA4-Ig and ICOS ligand (ICOSL) blocking Ab completely dissolves ongoing germinal center responses, whereas single agents show only partial activity. Next, we took two approaches to engineer a therapeutic molecule that blocks both pathways. First, we engineered CTLA4-Ig to enhance binding to ICOSL while retaining affinity to CD80/CD86. Using a library approach, binding affinity of CTLA4-Ig to human ICOSL was increased significantly from undetectable to 15-42 nM; however, the affinity was still insufficient to completely block binding of ICOSL to ICOS. Second, we designed a bispecific costimulation inhibitor with high-affinity CTLA4 extracellular domains fused to anti-ICOSL Ab termed bifunctional costimulation inhibitor. With this bispecific approach, we achieved complete inhibition of CD80 and CD86 binding to CD28 as well as ICOS binding to ICOSL. Such bispecific molecules may provide greater therapeutic benefit in IgG-mediated inflammatory diseases compared with CTLA4-Ig alone.

Ibuprofen pharmacokinetics in preterm infants with patent ductus arteriosus

OBJECTIVE

Our objective was to study the pharmacokinetics of ibuprofen in premature infants with patent ductus arteriosus on day 3 and day 5 after birth.

METHODS

Ibuprofen was administered on days 3, 4, and 5 by a 15-minute intravenous infusion of 10, 5, and 5 mg/kg, respectively, with the aim of closing the ductus arteriosus. Blood samples were drawn at time zero and at 0.5, 1, 2, 4, 12, and 24 hours after the first and third doses. Ibuprofen plasma concentrations were assayed by HPLC.

RESULTS

A total of 27 premature infants were included (gestational age, 28.6 +/- 1.9 weeks; birth weight, 1250 +/- 460 g; values are mean +/- standard deviation). Ibuprofen pharmacokinetics followed a 2-compartment open model. Between the first and third doses (day 3 and day 5) there was a significant decrease of the volume of distribution of the central compartment (Vd(c)) (0.244 versus 0.171 L/kg; P =.03) and area under the plasma concentration-time curve (524 versus 447 mg. h/L; P =.01). The decrease in Vd(c) was most pronounced in patients with a closing ductus. Total body clearance and plasma half-life did not change significantly. No significant differences were observed in ibuprofen peak plasma concentrations after the first and third doses in relation to ductal status after treatment.

CONCLUSION

Ibuprofen pharmacokinetics showed a large interindividual variation in premature infants during treatment for patent ductus arteriosus, and significant changes may occur between day 3 and day 5 after birth in those infants with a closing ductus. These findings may have implications for the treatment schedule with ibuprofen in patients with patent ductus arteriosus.

Amphotericin B colloidal dispersion (Amphocil) vs fluconazole for the prevention of fungal infections in neutropenic patients: data of a prematurely stopped clinical trial

We conducted an open label, randomised clinical trial to compare amphotericin B colloidal dispersion (ABCD, Amphocil) 2 mg/kg/day intravenously with fluconazole 200 mg/day orally, for the prevention of fungal disease in neutropenic patients with haematological malignancies. In the event of unresolved fever after 4 days of empirical antibacterial therapy, patients in both treatment groups were to receive ABCD, 4 mg/kg/day. However, the study had to be stopped in an early phase, due to severe side-effects of ABCD. A total of 24 patients were enrolled, 12 patients were randomly assigned to receive prophylactic ABCD, which was administered for a mean of 13.9 days. Fluconazole prophylaxis was given to 12 patients for a mean of 21.2 days. Therapeutic ABCD, 4 mg/kg, was initiated in four patients because of suspected fungal infection, all of whom had initially received fluconazole. A high rate of infusion-related toxicity of ABCD was observed. Chills occurred in 15/16 ABCD recipients (94%), accompanied by a temperature rise of >/=2 degrees C in 4/16 patients and of >/=1 degrees C but <2 degrees C in 10/16 patients. Other ABCD-related adverse events were hypotension (4/16), nausea with vomiting (5/16), tachycardia (7/16), headache (3/16) and dyspnoea (3/16). For premedication patients received: antihistamines (12/16), hydrocortisone (9/16) and/or morphine (6/16). ABCD was discontinued in 8/16 patients (50%) due to side-effects, which ultimately dictated early termination of the study. We conclude that ABCD is not suitable for antifungal prophylaxis in neutropenic patients due to severe infusion-related side-effects. Subject numbers were too low for conclusions on variables of antifungal efficacy.