By Manojna Maddipatla and Tamara Mathias
(Reuters) - VBI Vaccines Inc said on Monday a late-stage study was unsuccessful in showing two doses of its hepatitis B vaccine were as effective as three doses of an older vaccine from GlaxoSmithKline, sending its shares plunging 66%.
The study tested VBI's Sci-B-Vac against GSK's Engerix-B, a vaccine which was approved in the United States in 1989.
Two doses of Sci-B-Vac did not meet the trial's secondary goal of non-inferiority in all patients aged 18 and above, when compared to three doses of Engerix-B.
This marks a setback for the vaccine that will likely compete with Heplisav-B, a two-dose vaccine from Dynavax Technologies Corp's which gained FDA approval https://www.reuters.com/article/us-dynavax-techs-fda/dynavaxs-hepatitis-b-vaccine-gets-fda-nod-on-third-try-shares-up-idUSKBN1D93AN in November 2017.
"Without a two-dose non-inferiority claim on a potential label, it will be difficult for Sci-B-Vac to gain significant share from Heplisav-B, even if its three-dose regimen does enter and compete in some markets," RBC Capital Markets analyst Brian Abrahams said.
Dynavax shares rose 6.4% to $4.06 in afternoon trading.
VBI's trial, however, met its main goals and the company said its two-dose regimen could still hold potential in treating adults younger than 45.
The seroprotection rate, a measure of clinical protection provided by the vaccine, in all patients aged 18 and older who received Sci-B-Vac was 91.4% compared with 76.5% for those who received Engerix-B, the company said.
In harder-to-treat patients aged 45 and older, three doses of Sci-B-Vac was shown to be superior to the same amount of Engerix-B, with 89% protection versus 73%.
"We remain on track to submit applications for regulatory approvals in the U.S., Europe, and Canada beginning mid-year 2020," Chief Executive Officer Jeff Baxter said in a statement.
Baxter added that VBI intended to price the vaccine competitively with Engerix-B.
"We do not see ourselves competing with Engerix-B and GlaxoSmithKline. We rather see this product being complementary," he said.
Sci-B-Vac is also being studied in another late-stage trial, whose results are expected by the year end.
The vaccine is approved in over ten countries including Israel.
Hepatitis B, a viral infection that attacks the liver, is spread by contact with the blood or bodily fluids of an infected person. The World Health Organization estimates 257 million people are living with hepatitis B virus infection.
Hepatitis B vaccines have been available for more than two decades, but infection remains a worldwide issue, largely due to low vaccination rates.
(Reporting by Tamara Mathias and Manojna Maddipatla in Bengaluru; Editing by Shailesh Kuber)