Investing.com -- Compass Therapeutics (NASDAQ: CMPX) shares tumbled 80% Monday following mixed results from its Phase II/III COMPANION-002 trial evaluating tovecimig combined with paclitaxel in second-line biliary tract cancer.

The company announced the study achieved high statistical significance on the key secondary endpoint of progression-free survival. However, the trial did not meet overall survival secondary endpoints, raising questions about regulatory approval prospects.

According to the company, the overall survival results were impacted by significant benefit achieved by patients who crossed over from the control arm to the tovecimig arm, with 54% of patients switching treatments.

William Blair analysts noted, "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."

The trial evaluated tovecimig combined with paclitaxel in patients with second-line biliary tract cancer. The progression-free survival endpoint showed positive results with high statistical significance.

The next key milestone will be feedback from the company's pre-BLA meeting, expected in mid-2026. Investor focus will center on support for a BLA filing and potential commentary on accelerated versus full approval submissions, according to William Blair.

The steep decline in shares reflects investor concern about the regulatory path forward given the mixed trial results and uncertainty around FDA acceptance of the dataset for approval.

Investing.com -- Compass Therapeutics (NASDAQ: CMPX) shares tumbled 80% Monday following mixed results from its Phase II/III COMPANION-002 trial evaluating tovecimig combined with paclitaxel in second-line biliary tract cancer.

The company announced the study achieved high statistical significance on the key secondary endpoint of progression-free survival. However, the trial did not meet overall survival secondary endpoints, raising questions about regulatory approval prospects.

According to the company, the overall survival results were impacted by significant benefit achieved by patients who crossed over from the control arm to the tovecimig arm, with 54% of patients switching treatments.

William Blair analysts noted, "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."

The trial evaluated tovecimig combined with paclitaxel in patients with second-line biliary tract cancer. The progression-free survival endpoint showed positive results with high statistical significance.

The next key milestone will be feedback from the company's pre-BLA meeting, expected in mid-2026. Investor focus will center on support for a BLA filing and potential commentary on accelerated versus full approval submissions, according to William Blair.

The steep decline in shares reflects investor concern about the regulatory path forward given the mixed trial results and uncertainty around FDA acceptance of the dataset for approval.