Shares of Compass Therapeutics (NASDAQ:CMPX) plunged roughly 80% on Monday after the company released mixed data from its Phase II/III COMPANION-002 study. The trial tested the combination of tovecimig and paclitaxel in patients receiving second-line treatment for biliary tract cancer.
Company announcements indicated the study achieved high statistical significance for the trial's key secondary endpoint - progression-free survival. Despite that result, the trial did not meet its secondary endpoints for overall survival, prompting questions about how regulators will view the dataset.
Compass said the overall survival findings were affected by a high rate of crossover from the control arm to the tovecimig arm. According to the company, 54% of patients in the control group switched to receive tovecimig, and that dynamic contributed to the observed overall survival outcomes.
Market analysts at William Blair commented that the mixed dataset will likely be scrutinized by regulators. Their note stated, "This will raise questions on the approvability of this dataset, and while we believe the totality of the data shows that tovecimig provides clinical benefit in this patient population, it will clearly be a review issue at the FDA. Therefore, we expect shares of Compass to be volatile as investors weigh the totality of the data and FDA uncertainty."
Beyond the headline efficacy measures, the company and external observers are now focused on the next regulatory milestone: feedback from a pre-BLA meeting slated for mid-2026. William Blair highlighted that investors will be watching for indications of whether the company has sufficient support to file a Biologics License Application and whether the agency would consider accelerated approval versus a full approval pathway.
The sharp drop in Compass stock reflects market concern about the path to approval following the mixed results, particularly given the potential for the crossover effect to complicate assessments of overall survival. Investor reaction underscores uncertainty about whether the dataset, despite a positive progression-free survival outcome, will be judged acceptable by the FDA for an approval decision.
Contextual note - The trial evaluated tovecimig in combination with paclitaxel for second-line biliary tract cancer. Progression-free survival showed a statistically significant benefit, while overall survival secondary endpoints were not met. The company attributed the overall survival result in part to a 54% crossover rate from control to active treatment.