(Oslo, Norway, 18 July 2014) Bionor Pharma ASA (OSE: BIONOR) announces that results of the ad hoc, subset analysis of the large Phase II clinical study of therapeutic HIV vaccine candidate Vacc-4x – which identified C5/gp41 antibody levels as a potential biomarker for improved response to Vacc-4x – were presented today as a poster at the AIDS 2014 Conference in Melbourne, Australia.The biomarker analysis that identified patients more likely to respond to Vacc-4x was originally reported to the Norwegian Stock market on 3 February 2014.
“The identification of a potential biomarker has been one of the most important results for Bionor Pharma and the development of our lead therapeutic vaccine candidate Vacc-4x,” says Bionor CEO Dr. Anker Lundemose. “Our key focus is to enhance the effects of Vacc-4x in the treatment of HIV, and the identification of a biomarker is fundamental in the development of Vacc-4x as a monotherapy. It could also prove to be an integral part of our combination strategy ‘Kick, Kill & Boost.'”
Biomarkers may predict improved reductions in HIV viral load in response to Vacc-4x. Response to Vacc-4x was defined as reduction in viral load following a six-month scheduled interruption of standard HIV treatment (ART) compared to participants’ historic viral load values (pre-ART values). The analysis showed that participants more likely to respond to Vacc-4x, known as ‘responders’, were characterized by pre-existing high levels of anti-C5/gp41 antibodies prior to Vacc-4x vaccination in the 2010 study.
The subset analysis was based on the large Phase II Vacc-4x study (published in The Lancet Infectious Diseases 2014; 14: 291-300) that showed that study participants vaccinated with Vacc-4x experienced a 60% or log 0.4 reduction in median viral load compared to pre-ART viral load following a six-month ART treatment interruption. There was no corresponding reduction in median viral load reduction for participants who received the placebo. Some participants who received Vacc-4x responded more profoundly than others. The subset analysis shows that participants whose baseline anti-C5/gp41-antibody levels were above 4µg/ml had a median viral load reduction of log 0.94 or 88% (p=0.005, n=12) compared to median pre-ART values. Participants with anti-C5/gp41 antibodies below 4µg/ml had a median viral load reduction of 0.20 log or 37% (p=0.019, n=27) compared to pre-ART values.
Approximately 21% of participants in the 2010 Vacc-4x study had antibody levels above 4µg/ml prior to Vacc-4x vaccination. Confirmation of anti-C5/gp41 antibodies as a genuine biomarker for improved response to Vacc-4x will be subject to a larger prospective trial assuming approval of such trial by regulators.
About the 2010 Vacc-4x trial
The study was a phase II randomized, multicenter, double-blind, placebo-controlled multinational clinical trial of Vacc-4x. The trial enrolled 137 participants and was conducted at clinical trial sites in the UK, the US, Germany, Italy and Spain between July 2008 and June 2010. The 52-week follow-up period was completed in June 2011. The study is registered with Clinicaltrials.gov with the identifier NCT00659789 and was published in The Lancet Infectious Diseases 2014; 14: 291-300.
For study participants who completed a six-month treatment interruption of ART, there was a 64% reduction in median viral load set point between the two groups, which was statistically significant (Vacc-4x 22300 copies/mL, n=56; and placebo 61900 copies/mL, n=25; p=0.040) corresponding to a 0.44 log reduction. For participants with a pre-ART value available, a reduction in the median viral load set point of 0.40 log compared to pre-ART values was observed (24150 compared to 60470 copies/mL, p=0.0001) in the Vacc-4x group (n=45). This result was in contrast to the placebo group, in which no reduction was observed (n=18) (50400 compared to 52731 copies/mL, log 0.02, p=0.980).
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