Immunotherapy company ImmunityBio has reported that a challenge study showed its Covid-19 vaccine candidate provided complete protection of nasal and lung airways of non-human primates against the SARS-CoV-2 virus, which causes Covid-19.

The study involved a subcutaneous (SC) injection of ImmunityBio’s hAd5-COVID-19 vaccine and an oral enteric-coated capsule version of the vaccine.

A thermally stable oral version was made by drying (lyophilised) and encapsulating the hAd5-COVID-19 liquid drug substance.

The US Biomedical Advanced Research and Development Authority (BARDA) sponsored in vivo non-human primate challenge study evaluated the safety, immunogenicity and protection from infection and disease provided by ImmunityBio’s hAd5-COVID-19 vaccine.

The vaccine was given in two separate regimens and placebo controls were used for comparison.

Some primates were administered SC dose of hAd5-COVID-19 vaccine on day zero, followed by an SC boost on day 14 and an oral boost on day 28.

Another group received the SC prime followed by two oral doses.

Data from the study showed that the vaccine was well tolerated following both subcutaneous and oral capsule administration.

Both vaccination regimens provided complete protection from subsequent viral challenge by reducing viral RNA levels by day seven post-challenge.

In the study, immunisation with the vaccine stopped virus replication in all (10) Rhesus macaques. A drop in viral replication was noted on the first day itself and undetectable viral levels by day three to five post-challenge in many animals.

ImmunityBio chairman and CEO Patrick Soon-Shiong said: “These results provide compelling evidence of the need for vaccines to target both S and N proteins and to activate T cells to produce immune system memory to combat this virus.

“The exciting finding that the thermally-stable oral formulation triggers immune responses sufficient to inhibit virus replication to undetectable levels bodes well for the possibility that this oral formulation could serve as a universal heterologous booster.”

On discussions with the US FDA, the oral vaccine candidate will progress to Phase I human trials as a prime and a boost and as a boost to subcutaneous doses.