Second pivotal study bodes well for VBI's hep B vaccine
Investors of VBI Vaccines were unimpressed last year when the company’s hep B vaccine fell short in comparison to GSK’s established Engerix-B in a key late-stage study. On Thursday, the Cambridge, Massachusetts-based company unveiled data from a second pivotal trial that appears to ameliorate some of those concerns.
VBI’s vaccine, Sci-B-Vac, has already secured approval in Israel and ten other countries. It is engineered to mimic all three surface antigens of the hep B virus to induce a potent immune response and is being developed to work at lower doses than existing hep B vaccines.
The second pivotal study, dubbed CONSTANT, was designed to assess the safety and immunogenicity of Sci-B-Vac versus Engerix-B, as well as evaluate the lot-to-lot manufacturing consistency of Sci-B-Vac.
The main goal of the 2,838-subject study — manufacturing consistency — was met. The key secondary endpoint, to achieve non-inferior immunogenicity as measured by seroprotection rates (SPR) at day 196, one month after completion of the full course of vaccination with either Sci-B-Vac or Engerix-B, was also achieved, the company said.
At day 196, the pooled SPR in subjects who received Sci-B-Vac was 99.3% compared to 94.8% for those on Engerix-B – a difference of 4.49% (95% confidence interval [2.90%, 6.63%]). Previously, on day 168 (after two vaccinations only) subjects on Sci-B-Vac were at 90.4%, while those on Engerix-B were at 51.6%.
VBI’s shares $VBIB jumped about 24% to $1.69 in morning trading.
The company plans to use CONSTANT data, along with the results of the PROTECT study, to submit marketing applications in the United States, Canada, and Europe, the second half of this year.
Data from the 1,607-subject PROTECT trial were announced in June 2019. In the study, Sci-B-Vac failed to show that two doses of the drug were equally effective as three doses of Engerix-B in the study — a key secondary endpoint. However, the VBI vaccine was found to be as protective as Engerix-B at the end of the third vaccination — meeting the main goal of the study.
VBI must also contend with another rival. After being linked to a string of inexplicable safety issues, Dynavax’s hep B vaccine Heplisav-B was finally approved in November 2017 — but despite its checkered path to the finish line, the vaccine’s efficacy and convenience profile appear to supersede Engerix-B.
Hep B is transmitted through contact with blood and bodily fluids of an infected person and is a highly infectious virus, and is 50 to 100 times more infectious than HIV — even slight lapses in infection control can result in patient-to-patient transmission. Since the early 1990’s the United States has implemented vaccination programs in newborn children, but those born before remain susceptible. CDC data now suggests 95% percent of new hep B infections in the United States occur in adults, as there is no standardized system for vaccinating people after school age, and particularly since spikes in injection drug use may be leading to acute outbreaks.