ASH 2023 – a short-lived success for Poseida

With Poseida opening up 16% today on the back of Sunday’s ASH poster for its allogeneic multiple myeloma Car-T therapy P-BCMA-ALLO1 it looked like the group was one of the few market winners of the conference so far, but within an hour its stock was off 15%. Investors are eyeing this T-stem cell memory-rich Cas-Clover gene-edited asset because it’s a key focus of Poseida’s 2022 allogeneic-focused tie-up with Roche, and what excited initially was the claim that high preconditioning might have solved the efficacy conundrum. Specifically, the poster cited an 82% ORR in 11 patients given P-BCMA-ALLO1 with high cyclophosphamide, versus 0% in the eight given standard lymphodepletion. Closer reading of the data, however, reveals that this only pertains to patients given a 2 million cell/kg dose. A further eight received much lower doses, and four got 6 million cells/kg – all with standard cyclophosphamide – and whether any remissions were seen here was not disclosed. It’s also too early to say anything meaningful about response durability, though slides on cell kinetics look promising. It might be that even higher cyclophosphamide might boost efficacy even further, but for now this remains a cherrypicked dataset.

Summary of efficacy in study NCT04960579

Source: ASH.