BOSTON—In June, VBI Vaccines announced that its hepatitis B candidate Sci-B-Vac bested GlaxoSmithKline’s Engerix-B in older adults. But the company’s stock still nosedived, thanks to the study missing a secondary endpoint that could have helped its case for a reduced dosing schedule.
Now, at the annual meeting of the American Association for the Study of Liver Diseases, VBI Vaccines is emphasizing a different secondary endpoint: the time it takes for the vaccine to protect people. A two-dose vaccine has obvious advantages over a three-dose one. But in a three-dose world where people aren’t very good at getting all of them, it’s important to have a vaccine that acts quickly.
“There is a compliance issue,” VBI Chief Medical Officer Francisco Diaz-Mitoma told FierceBiotech. “In the real world, only one in four people come back to have their three shots, so it’s very important to have a vaccine that is effective since the first vaccination.”
RELATED: Brii Biosciences ramps up with VBI Vaccines partnership, new R&D headquarters
Sci-B-Vac protected fewer people after the second dose than Engerix-B did after the third dose—66% versus 77%—but it protected twice as many people than Engerix-B did at every time point in the study up until the third dose. One month after the second dose, 51.5% of Sci-B-Vac patients were protected, compared to 24% of Engerix-B patients. At the six-month mark, 66% of Sci-B-Vac patients were protected versus 27%. It took more than six months for Engerix-B to protect 50% of patients, a number that Sci-B-Vac hit after two months.
Diaz-Mitoma underlined the vaccine’s efficacy in an older population “that normally has a very high proportion of people who do not respond to standard vaccination. This is through the aging process … People start to have decreased T-cell immunity and they are less able to respond to normal vaccination,” he said.
Add in conditions such as obesity, diabetes and metabolic syndrome, and a patient’s ability to respond to a vaccine drops even lower. Those patients need a vaccine that calls forth a stronger immune response—and that stays effective for longer.
In the late-breaking poster, the company also reported antibody concentrations that were five to eight times higher in the Sci-B-Vac group than in the Engerix-B group. For example, Sci-B-Vax patients with diabetes had a geometric mean concentration of anti-hepatitis B antibodies that was five times higher than that of Engerix-B patients. The trend held regardless of patients’ BMI, age, gender and whether they had diabetes.
RELATED: VBI tanks after missing secondary goal in GSK head-to-head trial
“The high concentration of antibody determines how long people are going to be protected. This is particularly important in people who are immunosuppressed, say, people with diabetes,” Diaz-Mitoma said. Patients like these may still be at risk of hepatitis B infection, even if they have been immunized against it, he said. So, having more antibodies to start with will keep vulnerable patients protected longer.
VBI plans to file Sci-B-Vac for FDA approval in the middle of 2020, with a European submission to follow. The vaccine is already licensed in Israel and a handful of other countries.