ABL Bio's U.S. partner Compass Therapeutics said its bile duct cancer treatment "tovensimig," now in phase 2/3 trials, slowed tumor progression. However, it did not show a clear improvement in overall survival, suggesting the treatment effect may be limited in scope.
Compass Therapeutics on the 27th (local time) announced trial results comparing a combination of tovensimig and the chemotherapy paclitaxel with paclitaxel alone. The trial enrolled 168 patients receiving second-line treatment for bile duct cancer, randomly assigning 111 to the combination and 57 to monotherapy at a 2-to-1 ratio. For ethical reasons, the design allowed patients in the monotherapy arm to cross over to the combination arm upon disease progression.
Analysis showed the median progression-free survival (PFS) for the tovensimig combination was 4.7 months, a statistically significant improvement over 2.6 months with paclitaxel alone. PFS refers to the length of time the disease does not worsen.
By contrast, overall survival (OS), which shows how much longer patients actually lived, was 8.9 months with the combination and 9.4 months with monotherapy, showing little difference and failing to meet the secondary endpoint.
The company said survival data were diluted because 31 patients in the monotherapy arm crossed over to the combination after disease progression.
A post hoc analysis excluding the impact of crossover found a clearer difference. The median OS for the 31 crossover patients was 12.8 months, a large increase compared with 6.1 months for the 26 patients who remained on monotherapy. Notably, even though these patients had faster disease progression early in treatment, their survival improved significantly after switching to the combination.
In terms of safety, overall tolerability was favorable and consistent with prior findings. The most common adverse events were hypertension (69%) and fatigue (67%); at grade 3 or higher, hypertension (44%) and neutropenia (36%) were most frequently reported.
Based on these results, Compass Therapeutics plans to meet with the U.S. Food and Drug Administration (FDA) regarding a biologics license application (BLA).
Compass Therapeutics CEO Thomas Schuetz said, "The tovensimig combination showed improvement in PFS, and it also recorded a 17.1% rate for the primary endpoint, ORR (the proportion of patients whose tumors shrink by at least a certain threshold after anticancer treatment)," adding, "Based on these clinical results, we plan to work with the FDA to submit a BLA seeking approval as a second-line treatment for bile duct cancer."