Sustained delivery of interleukin-2 from a poloxamer 407 gel matrix following intraperitoneal injection in mice.

Parenteral delivery of recombinant biologic response modifiers (BRMs) remains a challenge because of the brief intravascular half-life of most recombinant proteins and their associated rapid clearance from the circulation. Recombinant derived interleukin-2 (rIL-2) was formulated with Pluronic F-127, N.F. (poloxamer 407, N.F.) and the biological activity determined vs time at 4, 22, and 37 degrees C. As assessed by rIL-2-induced peripheral blood lymphocyte (PBL) uptake of [3H]thymidine, storage of rIL-2/poloxamer 407 (33% w/w) for 72 hr at 4 and 22 degrees C did not result in an overall negative slope of the [3H]thymidine vs time profiles. However, storage of an rIL-2/poloxamer formulation at 37 degrees C for 72 hr resulted in an approximate 15% reduction in the biological activity as assessed by [3H]thymidine incorporation. As assessed by bioassay ([3H]thymidine uptake), the cumulative percentage rIL-2 released in vitro at 22 degrees C after 8 hr from rIL-2/poloxamer 407 matrices containing either 30% (w/w) or 35% (w/w) poloxamer 407 was 81.8 +/- 1.7 and 82.1 +/- 4.7%, respectively. When ELISA was used to determine the amount of rIL-2 released vs time, the corresponding values for the cumulative percentage rIL-2 released were 82.6 +/- 10.1 and 40.9 +/- 8.8%. Cytotoxicity of rIL-2 stimulated PBLs cultured with poloxamer 407 (0.17%, w/w) toward malignant Daudi cells was significantly (P less than 0.05) enhanced compared to controls. Finally, mice injected with the rIL-2/poloxamer 407 formulation (1 x 10(5) U/inj. q.d. x 3 days) demonstrated a bioequivalent effect of rIL-2-induced natural killer (NK) cell activity in vitro toward malignant murine YAC-1 cells at one-half the standard exogenously administered dose of rIL-2 known to generate enhanced NK lytic activity in mice (1 x 10(5) U/inj. b.i.d. x 3 days). No untoward systemic side effects were observed for mice injected i.p. with polymer vehicle alone (30%, w/w) (0.15 ml q.d. x 3 days), pH 7 phosphate-buffered saline (PBS) (0.15 ml q.d. x 3 days), rIL-2 formulated with poloxamer 407 (30%, w/w) (1 x 10(5) U/0.15 ml q.d. x 3 days and 0.5 x 10(5) U/0.15 ml q.d. x 3 days), or rIL-2 dissolved in PBS (1 x 10(5) U/0.15 ml b.i.d. x 3 days).(ABSTRACT TRUNCATED AT 400 WORDS)