Compass Therapeutics Reports Mixed Biliary Tract Cancer Data, Plans FDA Meeting for Tovecimig BLA

Compass Therapeutics Inc. reported mixed data from the Phase 2/3 Companion-002 study testing the bispecific antibody tovecimig in biliary tract cancer and plans to meet with the U.S. FDA to discuss a Biologics License Application (BLA). Shares of the Boston-based firm (NASDAQ:CMPX) closed April 27 at $1.79, down about 64%, or $3.23, as Wall Street sifted the results.

The phase 2/3 Companion-002 study tests tovecimig (a DLL4 x VEGF-A bispecific antibody) in combination with paclitaxel, versus paclitaxel alone, in patients with advanced biliary tract cancer who have previously progressed on gemcitabine and platinum-containing chemotherapy.

The company had already hit the primary endpoint of overall response rate (ORR). Last April the company reported a 17% ORR among 111 patients receiving the combo, compared with 5% for paclitaxel, a result that hit statistical significance with a p value of 0.031.

Also vital will be the key secondary metrics of progression-free survival (PFS) and overall survival (OS), which are due late this quarter. At the time of the ORR data, survival data were delayed from the second half until the fourth quarter of 2025, and they were later pushed back further, until the first quarter of 2026. Compass blamed fewer deaths in the study than initially expected, leading to hopes that tovecimig might be improving survival. However, it is also possible that all Companion-002 patients — not just those on tovecimig — are living longer than expected owing to certain baseline characteristics.

Compass has said it hopes to file the project with regulators later this year, assuming positive survival data. Investors seem optimistic, with the group's share price having almost tripled since the ORR data were reported.

However, Companion-002 has drawn criticism for using paclitaxel as the comparator, with NCCN guidelines citing Folfox chemo as the preferred second-line regimen. Compass has given survival numbers with Folfox as a benchmark to hit in its quest to make tovecimig the second-line standard of care. In the ABC-06 trial, Folfox led to median PFS of 4.0 months and median OS of 6.2 months.

Toxicity will also be closely watched when the full results are reported. All Compass said was that tovecimig's safety profile in Companion-002 was in line with previous studies, and that full data would be released along with the PFS and OS results.

Compass also has ambitions in first-line biliary tract cancer, where an MD Anderson-sponsored phase 1/2 trial is ongoing, testing tovecimig plus Imfinzi and chemo; results could come this year. The company also plans to start a solid tumor basket trial this half in DLL4-positive tumors including colorectal, gastric, ovarian, renal and liver.

DLL4 is involved in angiogenesis, but previous attempts to hit it have been limited by adverse events such as pulmonary hypertension and heart failure. It is hoped that targeting both DLL4 and VEGF could improve potency, although other projects with this dual mechanism appear to have fallen by the wayside, such as AbbVie's dilpacimab (ABT-165) and Feng Biosciences' navicixizumab.