Investors fret as VBI's hep B vaccine fails key secondary PhIII study goal
Sobered by mounting costs, Dynavax $DVAX last month made the decision to focus all its resources on its 2017-approved hepatitis B vaccine Heplisav-B, which rivals and supersedes the efficacy and convenience profile of GSK’s $GSK established Engerix-B. The California-based company will be on the lookout for another competitor — VBI Vaccines, which on Monday unveiled late-stage data on its hep B vaccine: Sci-B-Vac.
Sci-B-Vac, which has already secured approval in Israel and 10 other countries, is in Phase III development in North America and Europe. 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.
VBI on Monday broke out data from the PROTECT study, in which 1,607 subjects aged 18 years and older were either given a three-dose course of Sci-B-Vac (10 µg) or a three-dose course of Engerix-B (20 µg).
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. Investors were not impressed, and the Cambridge, Massachusetts-based company’s shares $VBIV cratered 58% taking VBI into penny stock territory at 81 cents before the opening bell on Monday.
Meanwhile, 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. In fact, data showed that the rate of seroprotection (an antibody response capable of preventing infection) — was 91.4% for Sci-B-Vac-treated subjects, versus 76.5% for Engerix-B — a statistically significant difference.
In addition, the seroprotection rate (SPR) in subjects aged 45 and over was 89.4% for Sci-B-Vac, versus 73.1% for Engerix-B after the third vaccination — meeting the co-primary endpoint. It also cleared other secondary goals in sub-analyses stratified by age, gender, body mass index, diabetic status and smoking status.
Data from another late-stage trial, CONSTANT, comparing Sci-B-Vac and Engerix-B is expected by the end of 2019. Pending the successful completion of CONSTANT, VBI is on to submit marketing applications in the U.S., Europe, and Canada next year, company chief Jeff Baxter said on Monday.
Hep B is transmitted through contact with blood and bodily fluids of an infected person and is a highly infectious virus, 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.
After being linked to a string of inexplicable safety issues, Heplisav-B was finally approved in November 2017. Despite its checkered path to the finish line, the vaccine’s efficacy and convenience profile supersedes Engerix-B.
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