Takeda spinout HilleVax sees stock sink 80% as norovirus vaccine flunks phase 2 trial in infants

HilleVax's stock took a nosedive after the vaccine biotech’s sole clinical-stage candidate failed a phase 2b trial in norovirus-related acute gastroenteritis (AGE).

The virus-like particle-based vaccine, dubbed HIL-214, missed all primary and secondary endpoints of the NEST-IN1 study of more than 2,800 infants aged about five months of age in the U.S. and Latin America.

The vaccine showed an efficacy of 5%, with 51 primary endpoints among the 1,425 infants who received HIL-214 and 25 of these endpoints among the 1,399 infants who received placebo.

As a result, the study did not meet the key endpoint of demonstrating efficacy against moderate or severe AGE events caused by the GI.1 or GII.4 norovirus genotypes, HilleVax noted. Even a look at the secondary endpoints was unable to produce any evidence of clinical benefit, according to the company.

The biotech’s stock was trading down 88% to $1.70 in premarket trading Monday from a Friday closing price of $14.06. HilleVax went public in 2022, less than a year after spinning out from Takeda.

Based on today’s results, the company will discontinue testing HIL-214 in infants, and is now “exploring the potential for continued development of HIL-214 and HIL-216 in adults.” In today’s release, HilleVax described HIL-216 as a “phase 1-ready vaccine candidate,” although the company doesn’t mention the vaccine on its pipeline page or in the most recent company update.

“We are disappointed that the NEST-IN1 study did not meet its primary efficacy endpoint,” CEO Rob Hershberg, M.D., Ph.D., said in the July 8 release.

“While HIL-214 previously showed clinical benefit in adults, NEST-IN1 was the first efficacy study conducted in infants for a norovirus vaccine candidate,” Hershberg added. “We believe the efficacy in the infant setting may have been impacted by the appearance of multiple emerging GII.4 strains in this trial.”

Hopes had been high for HIL-214 after a phase 2b study in adults, NEST-IN1, demonstrated statistically significant efficacy. As recently as the company’s May earnings report, the biotech was outlining to investors how positive results from NEST-IN1 would set the company up to “rapidly progress into phase 3 clinical trials in both infants and older adults.”