What happened

Shares of BioCryst Pharmaceuticals (NASDAQ:BCRX) are up 9% at 2:00 p.m. EDT after the biotech increased the number of COVID-19 patients expected to enroll in its phase 1 clinical trial. The study, which is testing BioCryst's RNA synthesis blocker, galidesivir, will now enroll 132 patients, double the 66 patients who were previously expected to enroll.

So what

Investors seem to be seeing the increase in enrollment as a sign that galidesivir is working, but there's a simpler explanation.

The two-part clinical trial consists of a dose-ranging study, which was expected to enroll three dose levels of 8 patients each for a total of 24 patients. The second part would test the best dose on up to 42 patients. That's how the company arrived at the 66 patients originally.

A doctor positions a breathing mask over a patient's face.

Image source: Getty Images.

Now what's interesting about this study is that it was originally designed to test galidesivir in patients with yellow fever. In fact, the clinical trial was first posted on March 27, 2019, well before the pandemic started.

With a clinical trial already set up, BioCryst likely saw adding the new disease to the established clinical trial as the fastest way to test galidesivir in patients with COVID-19. Given the need for speed, investors shouldn't fault the company for that.

According to the description of the study on ClinicalTrials.gov, yellow fever and COVID-19 "will proceed independently through the study," which would seem to mean there will be 66 yellow fever patients and 66 COVID-19 patients, for a total of 132.

The simple explanation for the update in expected enrollment is that whoever updated the ClinicalTrials.gov entry when COVID-19 was added to the clinical trial forgot to double the number of participants. By publication time, BioCryst Pharmaceuticals hadn't responded to a request for clarification on why the expected enrollment in the clinical trial was doubled.

Now what

Data from the first part of the study should be ready fairly soon. And the most recent clinical trial update added additional clinical trial sites, so BioCryst should be able to enroll the second part of the study more quickly.

But investors would likely be better off waiting for the results than trying to read into what the company's every little move means for the fate of galidesivir as a treatment for COVID-19.