The firm said in a statement on Monday it had struck supply deals with Israel and Singapore - where it is working on the vaccine with a university and has been conducting trials - and was urgently working to start later stage trials.
The California-based company's announcement came as Pfizer said its COVID-19 vaccine is more than 90% effective based on initial trial results, a major victory in the war against a virus that has killed over a million people and battered the world's economy.
The news from Pfizer, which could pave the way for its vaccine to be rolled out by year end, weighed sharply on the shares of Arcturus, which closed down 45%, and other smaller vaccine developers.
Arcturus added in its statement that its ARCT-021 candidate has been generally well tolerated in trials so far.
Equity analysts at Laidlaw & Company attributed the weakness in Arcturus' stock to concern that the efficacy of ARCT-021 might not be as robust as other competitors, while Roth Capital Partners said its results showed a continually improving immune response. Both firms have a buy rating on the stock.Elsewhere, Inovio Pharmaceuticals and Sorrento Therapeutics closed down 19% and 17%, respectively.