According to investigators, Zadaxin treatment given with the H1N1 vaccine led to an (p value=0.04) increase in the percentage of subjects who seroconverted, also when evaluated 42 days after vaccination, compared to those who received the H1N1 vaccine alone. In addition, the improvement in titers seen in Zadaxin-treated patients was maintained at this later timepoint.
Findings showed that, when measured 42 days following vaccination, 93% of patients in the low-dose Zadaxin arm and 94% of patients in the high-dose Zadaxin arm achieved seroconversion, compared to only 77% of patients in the vaccine-only arm of the study. This increased seroconversion with Zadaxin compares favorably with that seen at 21 days following vaccination, which the companies reported in January 2010 as being 89% and 88% in the two Zadaxin groups, compared to only 56% in patients treated with the vaccine alone, which was a statistical increase (p value < 0.01). A higher seroconversion rate is indicative of the robustness of the immune response and may lead to more durable protection.
The randomized, three-arm open label study is designed to evaluate efficacy based on the proportion of patients achieving seroconversion. The ongoing study, which has a planned duration of six months, is being conducted in patients with end-stage renal disease who are on chronic dialysis. One cohort of patients received the H1N1 vaccine only. The other groups received thymalfasin at either a low dose (3.2mg) or a high dose (6.4mg). Thymalfasin was given twice, the first injection seven days prior to vaccination and the second on the day of vaccination with Focetria.
All patients who did not achieve an antibody titer of at least 1:40 on day 21, received a second H1N1 vaccination on that day. Dosing regimens were based on preclinical results obtained in ferret and mouse models conducted in Europe and the US. All patients are being followed for six months, to measure the durability of the protective titers, the second key parameter for the assessment of the immunogenicity of a vaccination.
Friedhelm Blobel, president and chief executive officer of SciClone, said: “The seroconversion results that we have seen to date in this study are very encouraging and continue to demonstrate the value that Zadaxin may have in offering the public a more powerful vaccine regimen against the H1N1 virus.
“It is our hope that Zadaxin will ultimately provide the enhancement benefits to H1N1 vaccines for patients with compromised or weakened immune systems. If this study continues to show positive data, we may also explore the potential of Zadaxin to improve the response to vaccines with other flu or virus strains.”
The company will announce further data on the study after all patients have reached 184 days post vaccination and final topline results are available.