Treg depletion with denileukin difititox (DD) enhances lymphocytosis and eosinphilia in patients treated with high-dose IL-2 (HDIL-2) for metastatic renal cell cancer (MRCC)

Abstract

14627 Background: CD4+CD25+ T cells (Treg) play a suppressive role in immune regulation. DD is an IL-2 receptor specific cytotoxin. We postulated depletion of Treg with DD may enhance immune effector cell populations during HDIL-2 tx, including eosinophilia which was reported to be involved in immune response to neoplasm (Mattes et al. J Exp Med 197: 387, 2003). Methods: Seven pts (5 male, median age 58 yrs) with MRCC were tx’d with HDIL-2 and DD in different schedules to determine safety and effect on immune response as manifested by changes in Treg, lymphocyte, and peak eosinophil counts. Pts were tx’d with IL-2 600,000 IU/kg Q8H on days (d) 1–5 and 15–19. Three (group A) and 2 (group B) pts were given 6 and 9 ug/kg daily on d 8–10 respectively, while 2 (group C) pts received 9 ug/kg of DD on d -4- -2. Four (group D) pts with metastatic melanoma who received HDIL-2 as above but without DD were included as controls. Flow cytometry was done on days -4, 1,8,10,15 for group C and on days 1, 8, 10, 15, 22 for groups A, B, and D. CBC was obtained within 24 hours of flow cytometry. Results: After DD Treg increased in group A (mean change in absolute T-reg count of 16%) and decreased in groups B and C (34.5 and 20% respectively) compared to baseline. Group C trended toward a greater lymphocytosis at day 8 compared to all other groups (mean increase of 8.6 vs. 3.3 K/ul p = 0.059). A higher peak level of eosinophilia was noted in group C compared with groups A, B and D combined (mean increase of 9.9 vs. 3.0 k/ul p = 0.03). Group C demonstrated a higher mean % change in absolute number of CD8+ T-cells between onset of therapy and Day 8 compared to groups A, B, D combined (increase of 1095% vs. 496% respectively, p = 0.35). Toxicity was similar to that expected with HDIL-2. Conclusions: Administration of DD in conjunction with HDIL-2 was associated with a decrease in Treg that may be schedule and dose dependent. The results suggest an enhanced immune stimulatory effect as manifested by lymphocytosis and peak eosinophilia and CD8+ T-cells in group C. Despite small pt numbers, results suggest that pre-treatment with DD may confer an advantage. It is too early to know if laboratory results correlate to clinical benefit. [Table: see text]