GLS-5300 MERS CoV Vaccine Candidate Shows Promise in Phase 1 Trial

Investigators on the first human trial of a vaccine candidate for Middle East respiratory syndrome coronavirus (MERS-CoV) indicate that the vaccine was well-tolerated and induced a strong immune response with no serious adverse events.

In 2019 the US Centers for Disease Control and Prevention (CDC) placed emerging coronaviruses—including MERS-CoV—on its list of list of the top 8 zoonotic diseases of most concern in the United States. Since the virus was first identified in 2012, there have been 2449 confirmed cases of MERS-CoV and 845 associated deaths in 27 countries according to the World Health Organization (WHO), making the disease a priority in vaccine and therapeutic research. In a recent study published in The Lancet Infectious Diseases, investigators detail the first human trial of the GLS-5300 MERS-CoV DNA vaccine candidate.

The study included 75 healthy adults aged 18 to 50 years, who were enrolled in a phase 1, open-label, single-arm, dose-escalation study of GLS-5300 done at the Walter Reed Army Institute for Research (WRAIR) Clinical Trials Center from February 17, 2016, to July 22, 2016. GeneOne Life Science Inc. and Inovio Pharmaceuticals co-developed the vaccine candidate.

“Our phase 1 trial with WRAIR, as a first-in-man study, was planned to primarily evaluate the safety of GLS-5300 and to determine if vaccines mounted immune responses,” explained study co-author, Christine C. Roberts, PhD, in an interview with Contagion^®. Roberts explained that a prior pre-clinical study showed that following challenge with MERS-CoV, un-vaccinated rhesus monkeys developed disease and pneumonia, whereas rhesus monkeys vaccinated with GLS-5300 were protected and did not show any clinical or radiographic signs of pneumonia.

Volunteers in the study received 3 doses of GLS-5300—an initial dose followed by 2 additional doses at 1 month and 3 months following the initial dose. The patient follow-up occurred 1 year following receipt of the final dose. Three groups of 25 participants were given either 0.67 mg, 2 mg, or 6 mg of GLS-5300. Injection site reactions were reported by 70 participants, with lesser-reported adverse events including headache and fatigue, which were commonly mild. After receiving 2 vaccinations, more than 85% of study participants exhibited a detectable immune response to MERS-CoV, which continued through 1 year of follow-up. In addition, investigators detected neutralizing antibodies in 34 out of 68 participants.

The study team highlights the importance of their findings for military personnel deployed in the Middle East and South Korea, areas where MERS-CoV is endemic and which have seen largest outbreaks of the virus.

“GeneOne is collaborating with the International Vaccine Institute in an ongoing Phase 1/2a of the GLS-5300 MERS DNA vaccine conducted in South Korea, one of the countries most affected by MERS in the past,” said Roberts of the next stage of research for the vaccine candidate. “This study is evaluating intradermal administration of the vaccine and to determine if lower doses can be used with this alternate dosing strategy. Additionally, our vaccine co-development partner, Inovio Pharmaceuticals, is planning a Coalition for Epidemic Preparedness Innovation-funded phase 2 trial of the vaccine to be conducted in the Middle East.”