Arcturus Therapeutics (ARCT) : "underwhelming" coronavirus vaccine results

•  ARCT stock plunged 54.2% to 42.36 on Tue, Dec 30.

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(Tue 12/30/20) The biotech company said late Monday it received approval from Singapore health officials to begin a Phase 2 study of its experimental Covid-19 vaccine. The study will enroll up to 600 volunteers and evaluate two dosing regimens of the drug.

In early-stage testing, the coronavirus vaccine — dubbed ARCT-021 — generated neutralizing antibodies after a single dose. However, the levels of antibodies were lower than other rival vaccines that were able to match or exceed the levels in people recovered from Covid-19.

Raymond James analyst Steven Seedhouse called the results "underwhelming." In a report to clients, he said the lower number of antibodies than expected "reduces our confidence that ARCT-021 will be able to achieve competitive levels of vaccine (effectiveness) with single-shot dosing."

In the early-stage test, the levels of antibodies in volunteers were largely below what vaccines from Moderna (MRNA) and Pfizer (PFE) with its partner BioNTech (BNTX) were able to generate. Those coronavirus vaccines are now authorized and rolling out in the U.S. and other countries.

Pfizer's vaccine is 95% effective and Moderna's is 94.1%, but Arcturus' drug might be only 62% effective at blocking Covid-19, Seedhouse said. Still, anything north of 60% would be a decent outcome for this type of vaccine, the ARCT stock analyst added.

Single-Shot Coronavirus Vaccine?

Like Pfizer and Moderna, Arcturus' vaccine uses messenger RNA technology. But the biotech company had been hoping to use a single shot, making it easier to administer. Both Pfizer's and Moderna's vaccines require two doses given several weeks apart.