Poseida Therapeutics' New Treatment For Multiple Myeloma Shows Early Success In Clinical Trial

Poseida Therapeutics Inc PSTX released early efficacy and safety results from its Phase 1 study of P-BCMA-ALLO1, its BCMA-targeted allogeneic, T stem cell memory (TSCM)-rich chimeric antigen receptor (CAR)-T therapy candidate. 

The company is investigating P-BCMA-ALLO1 in partnership with Roche Holdings AG RHHBY for relapsed/refractory multiple myeloma. 

Detailed study findings are being featured at the 65th ASH Annual Meeting and Exposition.

At the October 23, 2023, data cut-off, 39 patients were enrolled as an intent-to-treat (ITT) population in the ongoing Phase 1 multicenter, open-label dose-escalation study. 

An overall objective response rate (ORR) of 82% (9/11 total patients) was reached among patients in the pooled P1 and P2 arms.  

ORR in the P2 arm was 83% (5/6), with 100% (5/5) of the responding P2 patients achieving a very good partial response (VGPR) or better and 40% (2/5) achieving stringent complete response (sCR). 

80% ORR was obtained in the P1 arm (4/5), with 50% of responding patients achieving VGPR. Non-responding patients, one in each of the P1 and P2 arms, had received and not achieved clinical response with the BCMAxCD3 bispecific TCE antibody therapy teclistamab before receiving P-BCMA-ALLO1.

A 100% ORR (9/9) was achieved among patients in P1 and P2 arms who had not received a prior BCMA-targeting bispecific TCE antibody, as well as 100% ORR (2/2) in patients who had received prior autologous CAR-T BCMA targeted therapy.

P-BCMA-ALLO1 was very well tolerated, with no graft-vs-host disease at any dose and low rates of cytokine release syndrome and neurotoxicity, all Grade 2 or less, found among all evaluable patients.

Enrollment is ongoing, including additional exploration of dose and lymphodepletion conditioning regimens. 

Price Action: PSTX shares were up sharply in the premarket session, but were down 16% at $2.63 at last check on Monday.

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