ReiThera, a biotech company, announces the preliminary safety and immunogenicity data from the phase 2 clinical COVITAR trial with GRAd-COV2, its novel Covid-19 vaccine candidate.
The trial's Independent Data Safety Monitoring Board (independent Committee for the evaluation of safety) and the Steering Committee (Scientific Committee for the evaluation of efficacy) recommended the continuation of the clinical development of the GRAd-COV2 vaccine following a recent review of the data.
The study, which was conducted in 24 clinical centers in Italy, enrolled 917 volunteers over the age of 18; 25% of subjects were over the age of 65 and/or with conditions associated with an increased risk of severe disease in case of SARS-CoV-2 infection. Volunteers were randomized in three regimens (1:1:1), receiving either a single vaccine dose followed by a placebo dose, or two vaccine doses, or two doses of placebo, with a three-week interval between the two administrations.
As agreed with the independent advisory boards and the competent regulatory authorities, ReiThera unblinded the trial participants at the two-month check-up stage following the administration of the first dose, to allow those who had received the placebo to take part in the Covid-19 vaccination campaign.
The safety profile and the immune response to vaccination with GRAd-COV2 confirm what was observed in the phase 1 clinical study. In particular, the vaccine was well tolerated at the first, and even better at the second administration. Adverse events, mostly mild to moderate and of short duration, were mainly related to pain and induration at the site of injection, fatigue, muscle pain and headache. There were no vaccine-related serious adverse events.
Antibody responses (seroconversion) against the SARS-CoV-2 spike protein were achieved in over 93% of the volunteers at three weeks after the first dose, reaching 99% after the second dose. Five weeks after the first vaccination, the titer of both spike-binding and SARS-CoV-2 neutralizing antibodies was comparable to that measured in a reference group of patients recovering from Covid-19 infection.
“We are very excited about the preliminary phase 2 data from our COVITAR trial,” said Roberto Camerini, MD Reithera medical director. “Our vaccine candidate confirmed its excellent safety and good immunogenicity profile in a large cohort. ReiThera reaffirms its commitment to the fight against Covid-19 in the face of pressing global demand for additional vaccines. The phase 3 program, based on a non-inferiority design with a primary immunological endpoint in comparison with a viral vectored vaccine already marketed, has received a positive opinion from the European Medicines Agency and other important regulatory agencies. We hope to be able to start phase 3 trial as soon as possible.”
“Adenoviral vector vaccines induce more potent and persistent cell-mediated responses than other vaccine platforms, due to the activation of T lymphocytes against the spike protein, as we confirmed in our phase 1 study of our candidate vaccine GRAd-COV2. We and others have shown that, unlike antibody immunity, T lymphocyte responses do not lose potency against SARS-CoV-2 variants of concern. Therefore, in the context of current and future epidemics, vaccines with this property could prove to be important weapons in offering protection from Covid-19, alone or in heterologous combination with other vaccine platforms,” adds Stefania Capone, Head of Preclinical and Clinical Immunology unit at ReiThera.
GRAd-COV2, the candidate vaccine against SARS-CoV-2 recently developed by ReiThera, is based on a novel and proprietary replication-defective simian (gorilla) adenoviral vector (called GRAd) encoding the full-length coronavirus spike protein (GRAd-COV2). The spike protein enables the coronavirus to enter human cells.
Simian adenoviral (SAd) vectors have been extensively used as delivery agents for genetic vaccine candidates against multiple infectious diseases, including Ebola and RSV (Respiratory Syncytial Virus), in different populations, including elderly and infants enrolled in early and late stage clinical trials to date. Preclinical and clinical evidence have demonstrated that ReiThera's vaccine technology is safe and induces robust cellular and humoral immune responses.