Gritstone bio down 49% as trial results underwhelm

Shares in Gritstone bio (Nasdaq: GRTS), a US biotech that claims to be developing the world’s most potent vaccines, closed Tuesday’s trading nearly 49% lower.

This followed the firm’s presentation of preliminary data from the ongoing, signal seeking Phase II portion of the Phase II/III study evaluating GRANITE, its personalized neoantigen cancer vaccine, in front-line metastatic microsatellite stable colorectal cancer (MSS-CRC).

"With regard to defining molecular response, we simply got it wrong"The primary endpoint was not met, with short-term circulating tumor (ctDNA) response analysis—molecular response as defined per protocol - failing to demonstrate a difference between study arms.