Assessing Haemostatic Efficacy In VWF/FVIII Replacement Therapy Trials Utilizing Subjective Vs. Objective Criteria – a Way to Improve Comparability and Accuracy of Clinical Outcome.

The assessment of the clinical efficacy during the conduct of a clinical trial is critical to the potential acceptance of that product to be a viable therapeutic option. This is especially true in the conduct of clinical trials involving rare bleeding disorders such as VWD, where there is predictably small patient enrollment and limited use of a control group. A 4-point Likert hemostatic efficacy scale with mostly subjective general criteria (excellent, good, moderate, none) has been used previously in most clinical trials published to date in the VWD field.

A validated and more objective set of criteria, intended to more specifically assess the therapeutic efficacy of VWF/FVIII replacement therapy was developed. These objective criteria include: quantization of transfusions of blood components; the need for salvage therapy utilizing alternative VWF/FVIII concentrates or other hemostatically active products; the requirement for significant dosing increases of replacement products; etc.

Patients in a VWD clinical trial with a new VWF/FVIII replacement product, wilate^Ò (Octapharma AG, Lachen, Switzerland), were assessed for clinical hemostatic efficacy in the treatment of their acute bleeding episodes, using both the traditional 4 point Likert scale, as assessed by the treating physician, and the newly proposed set of objective success and failure criteria for bleeding episodes during treatment, as determined by evaluation of the actual clinical data generated for each individual patient.

Results of the analysis using the new objective criteria when compared to the previous subjective efficacy assessment approach showed a comparable efficacy profile. This proposed objective hemostatic efficacy assessment examined specific clinical criteria that could be considered as indicative of a more accurate status of treatment.

This objective approach avoids the potential pitfalls of observer bias and inconsistency, which form the basis of criticism of the previously used subjective assessment tools. Furthermore, this more objective type of assessment approach has been requested and accepted in recent registration trials by FDA in the US.

Kessler:Grifols S.A.: Research Funding; Baxter-Immuno: Research Funding; NovoNordisk: Research Funding. Schwartz:Octapharma: Employment. Hegener:octapharma: Employment. Walter:Octapharma: Employment. Knaub:Octapharma: Employment.