VBI Vaccines pursues future hepatitis B vaccine showdown with Dynavax

This past December, VBI Vaccines announced it had initiated two parallel Phase III trials of their hepatitis B vaccine, Sci-B-Vac (hepatitis B [virus-like particle] vaccine), in head-to-head studies against GlaxoSmithKline’s (GSK’s) Engerix-B (hepatitis B vaccine [recombinant]), with the goal of justifying regulatory approval in the US, EU, and Canada.

Even if VBI is able to demonstrate Sci-B-Vac’s superior efficacy compared with Engerix-B, GlobalData expects the firm will have to face off against Dynavax Technology’s Heplisav-B (hepatitis B vaccine [recombinant], adjuvanted),  which received FDA approval in November 2017 and will have a clear head start in penetrating the US marketplace.

Sci-B-Vac consists of all three surface antigens of the hepatitis B virus (HBV): the S antigen, which is the primary antigenic component of all hepatitis B vaccines currently approved in the US, EU, and Canada, plus the pre-S1 and pre-S2 surface antigens. The vaccine elicits protection by delivering these antigens as enveloped virus-like particles (eVLPs), which mimic the size and structure of the HBV.

A previously completed head-to-head Phase III trial demonstrated 96.6%  and 96.0% seroprotection following three doses of Sci-B-Vac in those ≤45 and >45 years old, respectively, compared with 86.0% and 78.6% seroprotection provided by three doses of Engerix-B. These results justified regulatory approval in Israel and 14 other countries.

If Sci-B-Vac is approved it will face serious competition from Dynavax Technology’s Heplisav-B (hepatitis B vaccine [recombinant], adjuvanted), which was approved in November 2017. Heplisav-B boasts a high seroprotection rate, ranging from 91.6–100% across all age groups following only two doses delivered one month apart.

VBI vaccines’ CEO has said that they might pursue approval for Sci-B-Vac as a two-dose regimen, but from the published Phase III results, seroprotection following two doses was found to only be 34.7%, and therefore it seems unlikely to be able to compete with the efficacy of Heplisav-B in just two doses. VBI Vaccines has also failed to include efficacy following two doses as a primary endpoint in either of the company’s new trials, so approval for a two-dose regimen seems unlikely at this point.

GlobalData believes that VBI Vaccines should consider altering the design of Phase III trials for Sci-B-Vac to include a more focused investigation into a two-dose regimen. However, Dynavax had a tough time when seeking approval for Heplisav-B due to its proprietary adjuvant contained in the vaccine, so marketing Sci-B-Vac as an adjuvant-free vaccine could remain an option to VBI Vaccines if it ends up going against Heplisav-B with a three-dose vaccine.

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