New data pooled from four large, "real world" post-marketing surveillance studies showed that sucrose-formulated recombinant factor VIII (rFVIII-FS) reduced bleeding and provided data regarding adverse events in more than 950 patients with mild-to-severe hemophilia A. Additionally, rates of inhibitor formation were reported in both previously treated and previously untreated patients. The data were presented at the XXII Congress of the International Society on Thrombosis and Haemostasis (ISTH).(1)(2)

In this analysis, the investigators judged rFVIII-FS hemostasis to be "good" or "very good" in 98.9 percent of patients. Serious adverse drug reactions were seen in 1.1 percent of patients and new (de novo) inhibitors were observed in 0.8 percent of patients.

"In a 'real world' setting, these data reflect some of the extensive global clinical experience with rFVIII-FS," said Georg Lemm, M.D., Ph.D., vice president, Global Clinical Development, and head, Hematology Group, Bayer Schering Pharma. "It is particularly noteworthy that a low rate of inhibitor formation was observed in this analysis of data pooled from post-marketing surveillance studies. Inhibitor formation is a significant challenge for both clinicians and their patients, and its treatment is costly and requires significant time to overcome."

Open label study investigating the efficacy of prophylactic versus on-demand rFVIII-FS treatment

In another presentation, (3) data from an open label clinical study that enrolled 20 adult men with severe hemophilia A (with and without target joints) demonstrated that patients who were changed from on-demand to prophylactic (preventive) infusions of rFVIII-FS had significantly reduced median joint bleeds per 6-month treatment period (zero events versus 15.0 events, respectively; P One or two infusions were required to treat bleeds in 87.5 percent of patients who used rFVIII-FS for on demand bleeding. For prophylaxis, one or two infusions were used by 76.4 percent of patients. In addition, rFVIII-FS was effective in controlling bleeding during surgical procedures, with hemostasis judged as "excellent" or "good" in 93.4 percent of 61 procedures.

Poster no. PP-WE-579: Inhibitor formation with sucrose-formulated recombinant factor VIII in patients with hemophilia A: Results from post-marketing surveillance studies.

Dr. Fukutake also reported pooled results evaluating inhibitor formation following rFVIII-FS treatment from the same four open-label studies. The study assessed de novo, recurrent and ongoing inhibitor formation in 967 patients across the four studies. Nearly 95 percent of patients had received prior treatment, 76 (7.9 percent) of whom had a history of inhibitors.

Fourteen of the 967 patients evaluated (1.4 percent) experienced a positive inhibitor test during the study period. De novo inhibitors were detected in seven of 891 patients (0.8 percent; mean treatment duration 90 +/-50 days [mean+/-SD]) and recurrent or ongoing inhibitors were found in 7 of 76 patients with a positive inhibitor history (mean treatment duration 76.9+/-123.2 days). One patient of 51 previously untreated patients developed inhibitors and of the 348 patients who reported prior treatment with plasma-derived FVIII, none developed inhibitors upon switching to rFVIII-FS.

Poster no. PP-TH-584: Efficacy of secondary prophylactic versus on-demand sucrose-formulated recombinant factor VIII treatment in adults with severe hemophilia A with and without target joints.

The results of a Bayer-sponsored, open-label clinical trial were reported by lead investigator Peter Collins, M.D., centre director, Arthur Bloom Haemophilia Centre at the University Hospital of Wales, Cardiff, United Kingdom. The aim of the study was to evaluate the effect of prophylactic treatment on the number of joint bleeds in adult men with severe hemophilia A compared with on-demand treatment in a single-arm cross-over treatment trial. During the first six months of the study, all patients received on-demand rFVIII-FS treatment. Patient therapy was then changed to a prophylactic treatment regimen for seven months.

In this study, which enrolled 20 adult men, results showed the median number of joint bleeds per patient per 6-month treatment period was significantly lower during the prophylaxis period (0 events [range 0-3]) compared with the on-demand period (15.0 events [range 11-26]; P