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.”
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.
“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.