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COVID-19: Moderna Registers Positive Phase 1 Results for mRNA Vaccine
By Ruchi Jhonsa, Ph.D.
Two months into the Phase 1 trial, Moderna Inc. today announced encouraging interim results from the Phase 1 trial of the vaccine. The company reported that the vaccine could successfully induce an immune response in the participants to the same levels as patients recovered from COVID-19. More importantly, it was found safe and generally well-tolerated in the participants with all the three doses. Based on this interim data, the company is expected to launch the Phase 3 trial in July. If the vaccine is found effective and safe to use, it could be out in the market by 2021, the company said.
“These interim Phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection starting with a dose as low as 25 µg,” said Tal Zaks, M.D., Ph.D., Chief Medical Officer at Moderna.
Key Interim Results from the Study
A total of 45 participants were enrolled in the study for 6 weeks where each received two doses of the vaccine intramuscularly. Participants were given two doses of either 25μg, 100μg, or 250 μg of the vaccine every 28 days. According to the data, all the participants showed the presence of antibodies in their blood as early as 15 days from the day of their first dose. Interestingly, 6 weeks after the first dose of 25μg vaccine, levels of antibody in the healthy participants were found equivalent to that of patients recovered from COVID-19 infection. Moreover, when dosed with 100μg of vaccine, the level of antibodies in the study participants “significantly exceeded” that of recovered patients. These results indicate that the vaccine has a “high probability to provide protection from COVID-19 disease in humans” Moderna CEO Stephane Bancel said during a conference call with the investors.
Although the data is encouraging, it doesn’t necessarily mean that the antibodies produced by the vaccine can neutralize the pathogen. The neutralizing antibodies bind to the viral surface and block its interaction with the host cells thereby rendering the infectious agent or pathogen ineffective. However, not all antibodies that bind a pathogen are neutralizing. Therefore it is important to determine the neutralization power of the antibodies generated by the mRNA vaccine. So far, the company has reported the presence of neutralizing antibodies in only eight participants, four from 25μg and 4 from 100μg dosing arms. Interestingly, the level of these neutralizing antibodies crossed that of the recovered patient when measured on the 43rd-day post first dosing. The presence of neutralizing antibodies is a strong indication of the effectiveness of the vaccine.
mRNA-1273 was generally safe with very few adverse events. To date, the most notable adverse events with grade 3 symptoms were seen for patients dosed with 250μg of the vaccine. However, these were transient and resolved by themselves.
The interim data is complemented by preclinical results from a viral challenge study conducted in mice in collaboration with NIAID. The preclinical data showed that the vaccination prevented viral replication in the lungs of animals infected with the SARS-CoV-2 virus. Based on interim data, the phase 2 study will now include 50μg and 100μg dosing arms with the aim of picking the effective dose for the pivotal Phase 3 study. The company anticipates that the dose for the Phase 3 study will be between 25μg and 100μg.
“With today’s positive interim Phase 1 data and the positive data in the mouse challenge model, the Moderna team continues to focus on moving as fast as safely possible to start our pivotal Phase 3 study in July and, if successful, file a BLA,” said Stéphane Bancel. “We are investing to scale up manufacturing so we can maximize the number of doses we can produce to help protect as many people as we can from SARS-CoV-2.” The company’s vaccine planning, execution, and scale-up efforts are being supported by BARDA. The funding body committed up to $483 million last month for conducting late-stage trials.
Timeline of Vaccine Development
Days after the Chinese government released the genomic sequence of the novel coronavirus, Moderna and NIAID decided to collaborate on developing the vaccine for coronavirus. Taking advantage of Moderna’s expertise in mRNA vaccines, the duo determined the sequence of mRNA that will be used for developing the vaccine. The company chose mRNA that encoded prefusion stabilized form of the Spike (S) protein important for viral attachment. Within 25 days of finalizing the mRNA sequence, Moderna came out with the first batch of clinical trial-ready vaccine. On March 16, the first participant of the Phase 1 study was dosed to determine the safety and immunogenicity of mRNA-1273. The open-label trial enrolled 45 healthy adults in the age group 18-55. On May 12, the US FDA granted fast track designation to the mRNA vaccine a week after it got a green signal for Phase 2 study. The Phase 2 study is expected to begin with a larger cohort of 600 participants testing the efficacy and side effects of the vaccine.
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