In a Phase II part B trial of its H5N1 avian influenza, Medicago found that the VLP vaccine induced a solid immune response and was safe and well tolerated. In the earlier Phase II part A trial, 135 volunteers received varying dosages or a placebo to determine the optimal dose. Two doses were given 21 days apart, and 20 micrograms proved the best dosage. The part B study gave an additional 120 volunteers the optimal dosage or the placebo.
The results also showed that older and younger volunteers responded similarly to the H5N1 vaccine, an advantage over other vaccine technologies. Among vaccinated volunteers who were 18 to 49 years old, 77% developed an immune response against the H5N1 virus, as did 76% of vaccinated volunteers older than age 50 years.
The H5N1 vaccine is intended as a pandemic product in case the virus mutates and becomes capable of human-to-human passage. If that occurs, “we could create stockpiles of vaccine around the world,” says Sheldon.
Medicago has other undisclosed vaccine candidates in its pipeline. It also plans to make monoclonal antibodies and biosimilars. Ten monoclonal antibodies have been efficiently expressed in tobacco.
“Many monoclonal antibodies are coming off patent by 2020. This is a real opportunity for us,” says Sheldon. However, biosimilars and monoclonal antibodies are more difficult and costly to manufacture than vaccines, “so we will be looking for partners to move forward,” says Sheldon.
Adapting plants as production systems has evolved slowly. “Like the early days of cell culture, it took time to get it right. But our time has come, and we have the opportunity to benefit human health,” says Sheldon.