Moderna (MRNA -1.75%) announced positive results today from an early stage clinical study of its novel coronavirus vaccine candidate mRNA-1273. The phase 1 clinical study included three cohorts with 15 participants in each between the ages of 18 and 55. Each cohort was given a different dose of mRNA-1273 -- either 25 micrograms, 100 micrograms, or 250 micrograms. 

Early but promising

Moderna reported that two weeks after the second dose (day 43), participants receiving the 25 microgram dose of mRNA-1273 had levels of antibodies that bind to the novel coronavirus at similar levels to those seen in patients who have recovered from COVID-19. Ten participants who received the 100 microgram dose of the vaccine candidate had levels of binding antibodies at day 43 that were significantly higher than levels seen in patients who have recovered from COVID-19.

COVID-19 vaccine on top of tiny house with doctor in background

Image source: Getty Images.

The most important thing that researchers are looking for in the early stage study is neutralizing antibodies that prevent the novel coronavirus from infecting a person. Moderna said that data was only available at present for the first four participants in the 25 microgram and 100 microgram cohorts. The levels of neutralizing antibodies in each of these eight participants at day 43 were at or higher than levels generally seen in patients who have recovered from COVID-19.

Moderna reported that mRNA-1273 was "generally safe and well tolerated." It said that all adverse events lasted only for a short time and resolved themselves.

Next steps

Moderna now plans to add a 100 microgram dose cohort to its phase 2 study of mRNA-1273 based on the early stage study data. The company hopes to begin a phase 3 study of its coronavirus vaccine in July that could lead to a regulatory filing if all goes well.