Factor VIII with a 237 amino acid B-domain has an extended half-life in F8-knockout mice

Essentials Factor (F)VIII with an intermediate-length B-domain showed higher levels in murine gene therapy. FVIII with different B-domain lengths were analysed. FVIII variants with B-domains between 186 and 240 amino acids (aa) have extended half-life in mice. Reduced cell binding of FVIII with a 237aa B-domain may explain the extended half-life. SUMMARY: Background Factor VIII consists of the A1-domain, A2-domain, B-domain, A3-domain, C1-domain, and C2-domain. FVIII with an intermediate-length B-domain of 226 amino acids (aa) has previously been evaluated in murine gene therapy studies. Objective To characterize FVIII with intermediate-length B-domains in vitro and in vivo in F8-knockout (KO) mice. Methods and results FVIII molecules with B-domains of 186-240aa had longer half-lives in F8-KO mice than FVIII molecules with shorter or longer B-domains. FVIII with a B-domain containing the 225 N-terminal aa fused to the 12 C-terminal aa of the wild-type B-domain (FVIII-237) had a 1.6-fold extended half-life in F8-KO mice as compared with FVIII with a 21aa B-domain (FVIII-21). The in vitro and in vivo activity of FVIII-237 were comparable to those of FVIII-21, as was binding to von Willebrand factor. Cell binding to LDL receptor-related protein 1 (LRP-1)-expressing cells was markedly reduced for FVIII-237 as compared with FVIII-21, whereas the affinity for LRP-1 was not reduced in surface plasmon resonance (SPR) studies. FVIII-21 cell binding and internalization could be inhibited by a fragment consisting of the 226 N-terminal aa of the FVIII B-domain, and SPR analysis suggested that this B-domain fragment might bind with weak affinity to FVIII-21. Conclusion Reduced cell binding of FVIII-237 might explain the observed extended half-life in F8-KO mice. This may contribute to the increased FVIII levels measured in murine gene therapy studies using FVIII constructs with similar B-domain lengths.

Preclinical pharmacokinetics and biodistribution of subcutaneously administered glycoPEGylated recombinant factor VIII (N8-GP) and development of a human pharmacokinetic prediction model

Essentials N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous (SC) FVIII dosing might reduce the treatment burden of prophylaxis. SC N8-GP has a favorable PK profile in animal models and disappears from skin injection sites. Combined animal (SC) and clinical (IV) data suggest that daily SC dosing may provide prophylaxis.

SUMMARY

Background N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous administration of FVIII may reduce the treatment burden of prophylaxis; however, standard FVIII products have low bioavailability after subcutaneous dosing in animals. Objective To evaluate the pharmacokinetics, effectiveness and local distribution of subcutaneously administered N8-GP in preclinical models and predict the human pharmacokinetic (PK) profile. Methods The pharmacokinetics of subcutaneously administered N8-GP were evaluated in FVIII knockout (F8-KO) mice and cynomolgus monkeys; a human PK prediction model in hemophilia A patients was developed. The hemostatic effect was evaluated in a tail vein bleeding model in F8-KO mice. The injection-site distribution and absorption of subcutaneously administered N8-GP were assessed in F8-KO mice by the use of temporal fluorescence imaging and immunohistochemistry. Results Subcutaneously administered N8-GP had a bioavailability, a first-order absorption rate and a half-life, respectively, of 24%, 0.094 h-1 and 14 h in F8-KO mice, and 26%, 0.33 h-1 and 15 h in cynomolgus monkeys. A dose-dependent effect of subcutaneously administered N8-GP on blood loss was observed in mice. A minimal amount of N8-GP was detected at the injection site 48-72 h after single or multiple dose(s) in F8-KO mice. Subcutaneously administered N8-GP was localized to the skin around the injection site, with time-dependent disappearance from the depot. PK modeling predicted that subcutaneously administered N8-GP at a daily dose of 12.5 IU kg-1 will provide FVIII trough levels of 2.5-10% in 95% of patients with severe hemophilia A. Conclusions Subcutaneously administered N8-GP may provide effective hemophilia A prophylaxis. A phase I clinical trial is underway to investigate this possibility.

Comparative studies of experimental oral inoculation of pigs with Ascaris suum eggs or third stage larvae

This experimental study was designed to compare the acquired resistance in pigs to Ascaris suum eggs following 4-weekly oral immunizations with either 200 A. suum infective eggs or 50 A. suum third stage larvae (L3). The two immunized groups (n = 7) together with an unimmunized control group (n = 7) of pigs were challenged orally with 50 infective A. suum eggs per kilogram bodyweight on day 19 after the last immunization. Seven days post-challenge the group immunized with eggs showed signs of resistance as evidenced by reduced lung larval counts compared with the challenge control group. Such significant resistance was not observed in the L3-immunized group. However, a markedly increased inflammatory liver reaction and white spot formation was demonstrated in the L3-immunized pigs after challenge compared with both control animals and egg-immunized pigs. On the day of challenge only the egg-immunized pigs mounted an anti-Ascaris antibody response both in serum and in lung lavage fluid. Ascaris-antigen induced increased histamine release from peripheral leucocytes following both immunization and challenge could only be demonstrated in the egg-immunized pigs. On day 7 post-challenge local IgA-anti-Ascaris antibodies were further demonstrated in bile of the egg-immunized group and in the small intestine of both immunized groups. In conclusion, oral A. suum egg immunization of pigs induced a significant reduction in lung larval counts upon challenge. In contrast, oral L3 immunization seemed to prime the pigs as observed by the presence of stunted lung larval growth and increased liver reaction post-challenge with A. suum eggs.

Fast acting nervous regulation of immunoglobulin A secretion from isolated perfused porcine ileum

BACKGROUND

The intestinal mucosa harbours a large number of nerve fibres and also plasma cells, providing the anatomical basis for studies of neuroimmune interactions.

AIMS

To study the effect of different neurotransmitters and electrical stimulation of the extrinsic intestinal nerves on secretion of immunoglobulin A (IgA).

METHODS

IgA was measured, using a specific ELISA, in the luminal and venous effluent from isolated vascularly perfused porcine ileal segments with preserved extrinsic nerve supply.

RESULTS

Infusion of several neuropeptides stimulated IgA output. Somatostatin (10(-8) M) stimulated IgA secretion in the luminal effluent from 46.6 (14.3) to 79.3 (19.0) microg/5 min and increased the venous output to 148.3 (23.0)% (n=6) of basal output, whereas noradrenaline (10(-6) M) inhibited the secretion (to 49.2 (6.5)% of basal output, n=6). Electrical stimulation of the mixed extrinsic nerves supplying the intestinal segment had no effect by itself. However, electrical stimulation during infusion of alpha adrenergic blockers or coinfusion of both alpha adrenergic and muscarinic blockers resulted in an immediate and significant increase in IgA, an effect that was abolished by nicotinic blockade.

CONCLUSION

The extrinsic nerve supply to the intestine could be involved in fast acting regulation of mucosal immune functions.

Time-action profile of the soluble, fatty acid acylated, long-acting insulin analogue NN304

AIMS

To compare the pharmacokinetic and pharmacodynamic properties of subcutaneously injected NN304, a novel long-acting insulin analogue, to NPH-insulin during euglycaemic glucose clamps in 11 healthy volunteers.

METHODS

On three study days NN304 was injected in three different doses (0.15, 0.3, 0.6 U/kg body weight), while NPH-insulin (0.3 U/kg) was injected in identical dose on two other days.

RESULTS

Injection of NN304 resulted in a linear and proportional increase in total NN304 concentrations (AUC0-1440 min: 0.15 U/kg: 344+/-43, 0.3 U/kg: 666+/-82, 0.6 U/kg: 1295+/-210 nmol/l; P<0.001). Maximal concentrations (609+/-140, 1046+/-283, 2033+/-460 pmol/l; P<0.001) were reached after 4-6 h. The metabolic response (expressed as maximal glucose infusion rates (GIR)) induced by subcutaneous injection of NN304 did not show the pronounced peak seen with NPH-insulin in an identical dose: GIRmax 3.2+/-1.1 vs. 4.4+/-1.8 mg/kg/min (P<0.05 for 0.3 U/kg NN304 vs. NPH-insulin; mean of both study days with NPH-insulin, all others not significant). NN304 also showed a slower onset of action, as indicated by a significantly higher tmax (446+/-162 vs. 359+/-175 min) and lower AUC0-240min (0.5+/-0.3 vs. 0.8+/-0.4 g/kg/240min; P<0.05, respectively). The three different doses of NN304 induced a significantly different glucose consumption in the first 720 min after injection (AUC0-720 min 1.1+/-0.6, 1.9+/-0.8, 1.7+/-0.8 g/kg; P<0.05 for 0.15 U/kg), but not over the whole study period (AUC0-1440 min 1.8+/-1.1, 3.1+/-1.3, 2.8+/-1.4 g/kg).

CONCLUSIONS

Injection of NN304 at different doses resulted in an increase in total NN304 concentration in a linear dose-response effect and a more even metabolic effect than NPH-insulin. However, we found no clear dose-response in its metabolic effect.