29 December 2020 - - US-based clinical-stage messenger RNA medicines company Arcturus Therapeutics Holdings Inc. (NASDAQ: ARCT) has received approval from the Singapore Health Sciences Authority to proceed with a Phase 2 clinical study of its vaccine candidate ARCT-021, the company said.

This study will build upon the favorable Phase 1/2 study results, as well as supportive preclinical data.

ARCT-021, both single administration and prime-boost regimens, are significantly effective in a primate challenge model.

Vaccinated macaques show substantial reductions in lung viral titers. Preliminary data shows that lung viral titers are between 3.30 and 3.81 log lower in ARCT-021 vaccinated primates, in both single dose and prime-boost groups (see figure below), respectively.

One week after SARS-CoV-2 virus challenge, geometric mean titers exceeded 1.31 x 104 in non-vaccinated primates compared with geometric mean titers of less than 10 in those vaccinated with ARCT-021.

ARCT-021 vaccination effective in humoral immunodeficient mice depleted of B cells
ARCT-021 vaccination (1 ug, single administration) is protective in animals depleted of B cells (see figure below).

Notably, ARCT-021 vaccination was not effective in mice depleted of CD8+ T-cells suggesting that cellular immunity, specifically CD8+ T cells, plays a critical role in preventing SARS-CoV-2 infection.

Founded in 2013 and based in San Diego, California, Arcturus Therapeutics Holdings Inc. (NASDAQ: ARCT) is a clinical-stage mRNA medicines and vaccines company with enabling technologies.

Arcturus' pipeline of RNA therapeutic and vaccine candidates includes self-replicating mRNA vaccine programs for SARS-CoV-2 (COVID-19) and Influenza, and other programs to potentially treat Ornithine Transcarbamylase Deficiency, Cystic Fibrosis, and Cardiovascular Disease along with partnered programs including Glycogen Storage Disease Type 3, Hepatitis B Virus, and non-alcoholic steatohepatitis.