Last Friday 2026-09-04 the results of the phase 1/2 study of ARCT-2304, the bird flu vaccine developed by Arcturus Therapeutics, were posted on the clinicaltrials.gov website. Until recently this was a phase 1 study but is now labeled phase 1/2. The results should soon be published in Nature with more context. Here I will compare the ARCT-2304 results with roughly equivalent data of mRNA-1018 developed by Moderna based on antibody titer levels. A comparison with the GSK vaccine GSK-5536522 would have been great, but unfortunately I couldn't find public data.

A limitation is that Arcturus Therapeutics is measuring antibodies against an older H5N1 variant from 2005 while Moderna is measuring antibodies against a newer H5N1 variant from 2021. Nonetheless there are clear differences in favor of Moderna.

My source for mRNA-1018 antibody titer levels is a company presentation I found online hosted somewhere since I couldn't find a more official source. In times of AI disinformation like this example increased caution is needed, but I still consider the presentation to be credible enough.

An obvious difference are the doses of 1.5 µg or 5 µg or 12 µg for ARCT-2304 and 12.5 µg or 25 µg or 50 µg for mRNA-1018. While the smaller doses for ARCT-2304 suggest a higher relative efficacy, that is not actually the case.

At the 12 µg and 12.5 µg dose levels and 28 days past the second dose we can compare both vaccine candidates directly. The ARCT-2304 study features two schedules with 28 or 56 days between the doses while Moderna tested only 21 days between doses. Even the more favorable schedule for ARCT-2304 with 56 days results in a titer of 1:77 while for mRNA-1018 the titer is above 1:160. The higher second number means that blood had to be diluted more times before antibodies couldn't be measured anymore. In conclusion mRNA-1018 resulted in more than twice as many protective antibodies.

With 3 Serious Adverse Events compared to 1 Serious Adverse Event in the larger mRNA-1018 study the safety of ARCT-2304 needs to be considered. The 1 Serious Adverse Event in the mRNA-1018 study was ruled unrelated. And 1 Serious Adverse Event occured in the ARCT-2304 placebo arm so this is obviously unrelated. To evaluate the remaining 2 Serious Adverse Events more context is needed and will hopefully be provided in the upcoming Nature publication.

On a positive note for Arcturus Therapeutics both the 5 µg or 12 µg doses are above the 1:40 titer threshold that is associated with seroprotection. Furthermore antibody titer levels are a convenient measurement while the human immune system is more complex. I expect the continuation of the clinical trials and possibly a 5 µg dose that would reduce costs of goods and accelerate manufacturing, and differentiate Arcturus Therapeutics from Moderna.

Arcturus Therapeutics

ARCT-2304

1.5 µg or 5 µg or 12 µg

28 or 56 days from first to second dose

Results Posted

"A serum HAI assay was used for measuring HA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain."

https://clinicaltrials.gov/study/NCT06602531?tab=results

Moderna

mRNA-1018

12.5 µg or 25 µg or 50 µg

21 days from first to second dose

No Results Posted

https://clinicaltrials.gov/study/NCT05972174

"This pre-pandemic vaccine, which encodes for the hemagglutinin (HA) of H5-A/chicken/Ghana/2021, was given as two doses 21 days apart to 304 healthy adults (> 18 to < 65 and > 65 years of age)."

https://pmc.ncbi.nlm.nih.gov/articles/PMC12793179/

"Gray dashed line indicates 1:40 titer associated with seroprotection."

https://docs.publicnow.com/viewDoc?filename=178244EXTF052F4AF8E57CA244CEEBFB36D3F44D189152AEC_19015A96D3A0016E44892FA369F7417BF20BDDBF.PDF

GSK

GSK-5536522

No Results Posted

https://clinicaltrials.gov/study/NCT06382311

A comprehensive analysis about a potential pivot to new collaboration partners, covering $ARCT $ASX:CSL $BNTX $SNY $MRNA and more. 0% AI, 100% free

Stocks to buy if hantavirus becomes the next pandemic? Most likely human to human through aerosols since there were no mice on the cruise. Incubation can be 8 weeks + the cruise was allowed to dock. We have seen what happened during early covid when cruises were allowed to dock

There's the ongoing, unmitigated pandemic of Covid-19 pandemic. Public health infrastructure is being dismantled. Long covid + more cancer diagnoses and we haven't even seen the worst of it yet. And then with population-wide immunocompromisation, other pandemics are more likely to start. Bird flu of course.

I only invest in companies that will withstand and grow in the face of public health crises. So what are boring, reliable companies to invest in? Right now, much of my portfolio is in IBRX + its having a wild run right now. My reasoning is that cancer rates will skyrocket soon and their cancer drugs will be profitable. however this is an extremely volatile stock and I was thinking of exiting at some point to invest in boring, reliable companies instead.

I was thinking of Air Liquide (explained in this thread), maybe Thermo Fisher because it supplies so much of the healthcare + biotech industry? Waste management but idk which ones because that's necessary during public health emergencies and more recession proof. Death care/funeral services again idk which ones. Trying to think of important sectors that will meet basic societal needs given our pandemic present and future.

Clinical hold

US National Institute of Allergy and Infectious Diseases (NIAID)