Phase I Trial of Anti-PSMA Designer CAR-T Cells in Prostate Cancer: Possible Role for Interacting Interleukin 2-T Cell Pharmacodynamics as a Determinant of Clinical Response

BACKGROUND Chimeric antigen receptor (CAR)‐modified “designer” T cells (dTc, CAR‐T) against PSMA selectively target antigen‐expressing cells in vitro and eliminate tumors in vivo. Interleukin 2 (IL2), widely used in adoptive therapies, was proven essential in animal models for dTc to eradicate established solid tumors. METHODS Patients under­went chemotherapy condi­tion­ing, followed by dTc dosing under a Phase I escalation with continuous infusion low dose IL2 (LDI). A target of dTc escalation was to achieve ≥20% engraftment of infused activated T cells. RESULTS Six patients enrolled with doses prepared of whom five were treated. Patients received 109 or 1010 autologous T cells, achieving expansions of 20–560‐fold over 2 weeks and engraftments of 5–56%. Pharmacokinetic and pharmacodynamic analyses established the impact of conditioning to promote expansion and engraftment of the infused T cells. Unexpectedly, administered IL2 was depleted up to 20‐fold with high engraftments of activated T cells (aTc) in an inverse correlation (P