Compass Therapeutics reports additional COMPANION-002 study results

Compass Therapeutics (CMPX) announced that it met the secondary endpoint of PFS and showed additional results in the randomized COMPANION-002 study, which evaluated tovecimig plus paclitaxel versus paclitaxel alone in patients with unresectable advanced, metastatic or recurrent biliary tract cancer treated in the second-line setting. The complete dataset, including duration of response, will be presented at a medical conference later this year. In total, 17.1% overall response rate, or ORR, for tovecimig in combination with paclitaxel including one complete response, compared to 5.3% for paclitaxel alone, in patients with BTC in the second line setting. This 11.8% improvement in ORR for those receiving tovecimig was statistically significant. All responses were assessed by blinded independent central review. Tovecimig in combination with paclitaxel demonstrated a statistically significant improvement in median PFS of 4.7 months compared to 2.6 months for paclitaxel alone. Progression was confirmed in each case by BICR. Tovecimig did not meet the OS secondary endpoint due to high crossover from the control arm and prolonged survival of those crossover patients after receiving tovecimig, as further described below. As a result of this crossover, 85% of patients in the study received tovecimig plus paclitaxel with a pooled OS in the study of 8.9 months. In the ITT OS analysis, tovecimig in combination with paclitaxel had a median OS of 8.9 months compared to 9.4 months for the control arm, which included 26 patients who received paclitaxel alone and 31 patients who crossed over to receive tovecimig in combination with paclitaxel. In the rank-preserving structural failure time OS analysis, the combination also had a median OS of 8.9 months compared to 9.4 months for paclitaxel alone. Though the RPSFT analysis is intended to adjust for crossover, its validity depends on certain assumptions that were not met in this study and thus its results here are largely uninterpretable. An additional, pre-specified secondary endpoint analyzed PFS in the patients in the paclitaxel arm who crossed over to receive tovecimig plus paclitaxel. In this analysis, the pre-crossover PFS on paclitaxel alone was compared to PFS with tovecimig post-crossover in the same crossover patients. In this subset, tovecimig demonstrated a statistically significant improvement with median PFS2 of 3.5 months after treatment with tovecimig compared to median PFS1 of 1.9 months for paclitaxel. In an analysis of OS in all patients randomized to the paclitaxel control arm, crossover patients who subsequently received tovecimig demonstrated a statistically significant improvement in median OS of 12.8 months compared to 6.1 months for non-crossover patients who received only paclitaxel. Another analysis of these same patients randomized to the paclitaxel control arm demonstrated that the crossover patients initially progressed faster on paclitaxel monotherapy compared to the non-crossover patients, with a median PFS of 1.9 months versus 3.6 months. Thus, notably, despite progressing more quickly on initial paclitaxel monotherapy, crossover patients still demonstrated a statistically significant median 12.8 months OS after being treated with tovecimig. Tovecimig was generally well tolerated and the safety profile was consistent with previously reported data from prior studies, with no new safety signals. The most commonly reported treatment emergent adverse events in the tovecimig combination arm were hypertension and fatigue. The most common related treatment-emergent adverse events of Grade 3 or higher included hypertension and neutropenia.