Glycoengineered factor IX variants with improved pharmacokinetics and subcutaneous efficacy

BACKGROUND

The rapid clearance of factor IX (FIX) necessitates frequent intravenous administration to achieve effective prophylaxis for patients with hemophilia B. Subcutaneous administration would be a preferred route of administration but is limited by bioavailability.

OBJECTIVES

To improve the pharmacokinetics (PK) and bioavailability of FIX, a screen was performed to identify positions for the introduction of novel glycosylation sites with maximal effect on PK and maintenance of coagulation activity.

METHODS

Two hundred fifty-one variants, each containing one additional N-linked glycosylation site, were screened in vitro, and the PK profiles of selected variants mapping to spatially distinct regions of FIX were evaluated in mice. Optimal variants were combined, and their PK and efficacy were determined in mice with hemophilia B.

RESULTS

Variants that mapped to spatially distinct regions of the FIX structure exhibited different degrees of improved PK and enabled selection of optimized sites while minimizing the loss of FIX activity. Combining the most effective N-glycan sites in the same FIX molecule resulted in further improvements in PK. An optimized variant containing three novel N-glycan sites (at amino acids 103, 151, and 228), and the activity enhancing 338A variant had double the specific activity of wild-type FIX, exhibited 4.5-fold reduced clearance and 2.4-fold increased subcutaneous bioavailability, and was efficacious at a fivefold lower mass dose than wild-type FIX after subcutaneous injection in a bleeding model in mice with hemophilia B.

CONCLUSIONS

Glycoengineering was used to significantly improve the subcutaneous PK and efficacy of FIX and may have advantages for subcutaneous dosing.

The impact of introducing thioguanine nucleotide monitoring into an inflammatory bowel disease clinic

BACKGROUND

Thioguanine nucleotides (TGNs) are the active product of thiopurine metabolism. Levels have been correlated with effective clinical response. Nonetheless, the value of TGN monitoring in clinical practice is debated. We report the influence of introducing TGN monitoring into a large adult inflammatory bowel disease (IBD) clinic.

PATIENTS AND METHODS

Patients with IBD undergoing TGN monitoring were identified from Purine Research Laboratory records. Whole blood TGNs and methylated mercaptopurine nucleotides were hydrolysed to the base and measured using HPLC. Clinical and laboratory data were obtained retrospectively.

RESULTS

One hundred and eighty-nine patients with 608 available TGN results were identified. In non-responders, TGNs directed treatment change in 39/53 patients. When treatment was changed as directed by TGN, 18/20 (90%) improved vs. 7/21 (33%) where the treatment decision was not TGN-directed, p < 0.001. Where treatment change was directed at optimisation of thiopurine therapy, 14/20 achieved steroid-free remission at 6 months vs. 3/10 where the TGN was ignored, (p = 0.037). Six per cent of patients were non-adherent, 25% under-dosed and 29% over-dosed by TGN. Twelve per cent of patients predominantly methylated thiopurines, this group had low TGN levels and high risk of hepatotoxicity. In responders, adherence and dosing issues were identified and TGN-guided dose-reduction was possible without precipitating relapse. Mean cell volume (MCV), white blood cell count (WBC) and lymphocyte counts were not adequate surrogate markers. MCV/WBC ratio correlated with clinical response, but was less useful than TGN for guiding clinical decisions.

CONCLUSIONS

Monitoring TGNs enables thiopurine therapy to be optimised and individualised, guiding effective treatment decisions and improving clinical outcomes.

The effects of Robotic-Assisted Locomotor training on spasticity and volitional control

We studied the effects of Robotic-Assisted Locomotor (LOKOMAT) Training on spasticity and volitional control of the spastic ankle in persons with incomplete Spinal Cord Injury (SCI). LOKOMAT training was performed 3 days/week during a 1-hr period including set-up time with up to 30 minutes of training during a single session. The training was provided for 4 weeks and subjects were evaluated before and after 1, 2, and 4 weeks of training. Spasticity was charterized in terms of neuromuscular abnormalities associated with the spastic joint. A system identification technique was used to quantify the effects of LOKOMAT training on these neuromuscular abnormalities. The effect of LOKOMAT training on volitional control was determined by measuring isometric maximum voluntary contraction (MVC) of ankle extensor and flexor muscles. Our results indicated that the reflex stiffness, abnormally increases in SCI, was significantly reduced (up to 65%) following 4-weeks of LOKOMAT training. Similarly, intrinsic (muscular) stiffness, which also abnormally increases in SCI, decreased significantly (up to 60%). MVCs were increased substantially (up to 93% in extensors and 180% in flexors) following 4-week training. These findings demonstrate that LOKOMAT training is effective in reducing spasticity and improving volitional control in SCI.

Robotic-assisted locomotor training impact on neuromuscular properties and muscle strength in spinal cord injury

We studied the effects of Robotic-Assisted Locomotor (LOKOMAT) Training on neuromuscular properties and muscle strength of the spastic ankle in persons with incomplete Spinal Cord Injury (SCI). LOKOMAT training was performed 3 days/week during a 1-hr period including set-up time. The training was provided for 4 weeks and subjects were evaluated before and after 1, 2, and 4 weeks of training. A system identification technique was used to quantify the effects of LOKOMAT training on neuromuscular abnormalities. The effect of LOKOMAT training on muscle strength was determined by measuring isometric maximum voluntary contraction (MVC) of ankle extensor and flexor muscles. Our results indicated that the reflex stiffness, abnormally increases in SCI, was significantly reduced (up to 65%) following 4-weeks of LOKOMAT training. Similarly, intrinsic (muscular) stiffness, which also abnormally increases in SCI, decreased significantly (up to 60%). MVCs were increased substantially (up to 93% in extensors and 180% in flexors) following 4-week training. These findings demonstrate that LOKOMAT training is effective in reducing spasticity and improving muscle strength in SCI.

The effect of robot-assisted lokomotor training on gait recovery: a multivariate analysis

To explore the effect of LOKOMAT and LOKOMAT+Tizanidine on the improvement of walking capacity for people with spinal cord injury (SCI), 20 SCI subjects with hypertonia spasticity at their ankle joints participated in a 12-session Lokomat training; among them, 10 subjects received Tizanidine. 1-hour LOKOMAT training was provided 3 times per week for 4-weeks. Subjects were evaluated 4 times for Timed-Up-and-Go, 10-Meter-Walking, and 6-Minute-Walking testings, at the baseline, 1-, 2- and 4-weeks after training. Latent Class Growth model was used to classify the LOKOMAT training speed, and clinical walking evaluations. Subjects in each treatment group could be classified into two subclasses for training speed and clinical evaluation. It was found that the training speed increased in all treatment group, while the subjects in LOKOMAT+Tizanidine presented a significant improvement of their training speed from the training session. The clinical evaluations classified subjects similarly, and no significant improvement of clinical measurements was observed for either treatment. The MVC dorsiflexion torque at the ankle joint was able to predict the class memberships of subjects for their walking capacity and can be used as a significant predictor for therapeutic functional recovery after spinal cord injury.

The centrality of community dynamics in the socio-economic recovery of devastated communities

OBJECTIVE

To assess and explore the health and socio-economic outcomes of Jubilee, a community on the Caribbean island of Grenada hit by Hurricane Ivan in 2004 and to identify remaining barriers to recovery.

METHODS

The assessment consisted of a mixed methods approach employing observations, household surveys, in-depth interviews and focus groups.

RESULTS

Eighty-five per cent of the residents live in a single-family home type dwelling which is occupied by multiple families. Twenty-seven per cent of the respondents depended on a river or stream for water and 83% utilized an outdoor pit latrine. Construction accounted for 28% of the employment while 16% reported having no occupation. Public and private transportation was limited and 48% of the residents lived on less than one United States of America (US) dollar per day. Access to healthcare was reported by 89% and the prevalence of diabetes and hypertension was identified by 13% and 30% of the residents respectively. Social fragmentation within the community represents a barrier that keeps the community from developing common goals leading to full economic recovery.

CONCLUSION

Jubilee has not fully recovered from the effects of Hurricane Ivan, but progress has been made in the reconstruction effort. These efforts have addressed the most immediate and basic needs of the community, mainly utility service infrastructure and home repairs. However issues related to the community's economic recovery are still unresolved.

Conserved epitopes in the protein tyrosine phosphatase family of diabetes autoantigens

IA2 and phogrin are important targets of humoral and cell-mediated autoimmunity in type 1 diabetes in man. They belong to a conserved subfamily of transmembrane protein tyrosine phosphatases (PTPs) associated with the regulatory pathway of secretion. To examine potential cross-reactivity between PTP family members we tested sera from T1D patients for reactivity to IA2, and the Drosophila (FLYDA) and C. elegans (IDA) orthologs using radioimmunoprecipitation assays of (35)S Met-labeled in vitro translated products of the cytosolic domains of these proteins. Approximately 80% of sera reacted with at least one probe. Of these, 82.5% showed reactivity to human IA2, 74.1% to FLYDA, and 33.7% to IDA. The majority of sera that bound FLYDA and/or IDA also recognized IA2. This raises the possibility that in some cases reactivity to IA2 may have arisen by molecular mimicry.