Pharmacokinetics and the transition to extended half-life factor concentrates: communication from the SSC of the ISTH.

Extended half-life proteins (EHL) are increasingly used in clinical practice, but there is no standardized approach to sampling, interpretation and implementation of pharmacokinetics (PK) data to maximize treatment benefit. The goal of EHL treatment is to attain a trough level sufficient to protect against spontaneous bleeds and reduce infusion frequency and limitations on individual activity and lifestyle. Performing classical PK assessments requires multiple blood samples, which is burdensome for patients and providers. Herein we review a population pharmacokinetic (popPK) approach to estimate individual PK parameters to transition patients from standard half-life (SHL) to EHL concentrates. We propose that a minimum of two to four post-infusion samples is sufficient to estimate individual PK profiles, with sufficient certainty to maintain factor levels above 1% and achieve bleed-free lifestyles. We also survey current PK use in patients transitioning to EHL, review key PK parameters and popPK models, and recommend an approach to using PK in patients initiating or switching to EHL.

Fifth Åland Island conference on von Willebrand disease.

The fifth Åland Island meeting on von Willebrand disease (VWD) was held on the Åland Islands, Finland, from 22 to 24 September 2016-90 years after the first case of VWD was diagnosed in a patient from the Åland Islands in 1926. This meeting brought together experts in the field of VWD to share knowledge and expertise on current trends and challenges in VWD. Topics included the storage and release of von Willebrand factor (VWF), epidemiology and diagnostics in VWD, treatment of VWD, angiogenesis and VWF inhibitors.

The spectrum of bleeding in women and girls with haemophilia B.

Although hemophilia B affects 1 in 25,000 males there may be 3 female hemophilia B carriers per affected male. This clinical review highlights the unique challenges faced by hemophilia B carriers including the under-recognition of bleeding symptoms associated with and without FIX deficiency, discrepancies in correlation between genotype and bleeding phenotype and therapeutic considerations utilizing clinical vignettes of common scenarios.

Recombinant porcine factor VIII for high-risk surgery in paediatric congenital haemophilia A with high-titre inhibitor.

INTRODUCTION: High-titre factor VIII (FVIII) inhibitors complicate peri-operative haemostasis. Recombinant porcine FVIII (r-pFVIII) may provide an alternative haemostatic agent for high-risk procedures and allow FVIII activity monitoring. AIM: Devise an effective haemostatic plan for repair of a progressively symptomatic aortic coarctation in a 5-year-old male with immune tolerance induction (ITI) refractory high-titre FVIII inhibitors. METHODS: Preprocedure human FVIII inhibitor titre was 58 Bethesda Units mL-1 (BU) and cross-reacted to neutralize porcine FVIII at 30 BU. Daily ITI with plasma-derived FVIII concentrate was supplemented with anti-B-cell and anti-plasma cell immunotherapy to reduce FVIII inhibitor titres. Potential haemostatic agents were evaluated in comparative ex vivo thrombin generation assays (TGA). RESULTS: Four weeks after immunosuppression, human and porcine inhibitor titres declined to 16 and 2 BU respectively. TGA with r-pFVIII was less robust than with activated prothrombin complex concentrate (aPCC); however, r-pFVIII was selected for cardiac surgery to secure the ability to assay FVIII levels throughout this high-bleeding risk procedure. Haemostasis with r-pFVIII was excellent; initial trough FVIII activity levels ranged from 0.81-1.17 IU mL-1 . On postoperative day 3, peak and trough levels markedly declined suggesting a rising porcine inhibitor titre. Postprocedure prophylaxis was transitioned to aPCC, informed by TGA. CONCLUSIONS: R-pFVIII provided effective peri-procedural haemostasis with no adverse events. Rapid neutralization of r-pFVIII after the first 60 hours, despite intensive immune suppression, accentuates the importance of careful monitoring. Use of TGA can support bypassing agent selection for convalescence. The comparative cost of r-pFVIII may limit its use to high morbidity clinical scenarios.

Correlation between dispensed and prescribed doses of factor products for bleeding disorders: can a small, centre-based pharmacy hit the mark?

The prescribing and dispensing of factor replacement products have come under scrutiny in recent years. Some payers are shunting patients away from local 340B pharmacies anticipating larger pharmacies will be better able to match dispensed antihaemophilic factor vials to the prescribed dose. Our aims were to assess our baseline ability to achieve an aggregate and per patient dispensed to prescribed factor ratio (D:P ratio) of 1 and to evaluate obstacles to achieving unity. We conducted a retrospective review of the factor products dispensed from our 340B pharmacy and the corresponding prescriptions over the 6-month period prior to instituting routine D:P ratio assessment. The mean D:P ratio for all 65 patients was 1.00 (SD = 0.07). The mean paediatric D:P ratio differed from unity (P = 0.017) and from the mean adult D:P ratio (P = 0.003) in favour of a higher dispensed dose. A correlation between lighter patients and a higher dispensed dose was observed. Also, paediatric patients receiving 2 vials per dose had a mean D:P ratio greater than unity (P = 0.002). Pharmacy size does not dictate the ability to achieve a D:P ratio of unity. Ongoing monitoring of D:P ratios and dose ranges prescribed should be performed by all pharmacies to ensure acceptable allocation and cost of factor replacement for each patient. To further improve the D:P ratio metric in the paediatric population manufacturers should strongly consider adding more nominal dose increments within their lower range of vial sizes.