AACR 2021 – Pieris might have to bet on combinations
Pieris’s lead Her2-targeting asset, PRS-343, has shown additional signs of monotherapy efficacy, though the data, revealed at AACR over the weekend, do not suggest a competitive profile. The molecule, an anti-Her2 x 4-1BB bispecific now known as cinrebafusp alfa, had spent half of 2020 on partial clinical hold, and its phase 1 study previously yielded a 13% remission rate in Her2-positive tumours. With 42 evaluable subjects the ORR reported at AACR is now 12%, with all five remissions, including one complete, occurring on 8mg/kg every two weeks. This includes one additional response in an unknown cancer, and the deepening of an earlier partial response into a complete remission. But this is where the good news ended: three of the responding subjects, including the one with a CR, have relapsed. Pieris highlighted preliminary evidence of PRS-343’s activity in poorly immunogenic and low-Her2 expressing tumours, but it seems likely that the project’s best chances to compete against the likes of Enhertu will be as part of combinations. A separate phase 1 trial with Tecentriq is ongoing, while a phase 2 test combining PRS-343 with Lilly’s Cyramza or Seagen’s Tukysa is to begin in the summer.