Arcturus Therapeutics drops a third in postmarket after vaccine data update
Dec. 28, 2020 5:04 PM ETArcturus Therapeutics Holdings Inc. (ARCT)By: Dulan Lokuwithana, SA News Editor22 Comments
Arcturus Therapeutics (NASDAQ:ARCT) is down 35.0% in after-hours as the company provided the clinical and preclinical data for its COVID-19 vaccine candidate, ARCT-021. Arcturus also announced that the Singapore Health Sciences Authority has signed off its Phase 2 clinical study backed by favorable Phase 1/2 study results, as well as supportive preclinical data.
Of the 106 participants in the Phase 1/2 trial, 78 received ARCT-021; 28 received placebo. 44 subjects have received ARCT-021 at doses selected for Phase 2 (27 young adults and 17 older adults). Two groups of 34 and 10 participants have each received a single administration of 5 µg and 7.5 µg, respectively, and a group of 24 participants has received a prime-boost regimen (5 µg x 2).
Only serious adverse event was in a placebo participant. Two subjects had mild or moderate adverse events at doses selected for Phase 2: Transient, asymptomatic Grade 3 lymphopenia, and in one older adult - transient Grade 3 fatigue and myalgia after the booster dose.
All 44 subjects receiving the doses selected for Phase 2 had humoral immune responses for binding (Luminex) and/or neutralizing antibodies (PRNT50), with cellular immune response evident by Day 15 for 5 µg and 7.5 µg doses.
In the preclinical study, the vaccinated macaques have demonstrated substantial reductions in lung viral titers with effectiveness for both single administration and prime-boost regimens in a primate challenge model.
ARCT-021 vaccination (1 ug, single administration) was protective in animals depleted of B cells, the company said in the statement. The lack of effectiveness of ARCT-021 in mice depleted of CD8+ T-cells indicates the crucial role played by cellular immunity, specifically CD8+ T cells, in preventing SARS-CoV-2 infection, it added.
Steve Hughes, M.D., Chief Development Officer of Arcturus, says: “The Phase 2 study will enable selection of the optimal ARCT-021 vaccination regimen for Phase 3 registrational studies.” The company expects to have interim Phase 2 data in early 2021 to support the initiation of a global Phase 3 study in Q2 2021.