| Popis: |
The present studies were undertaken to examine the immunotherapeutic properties of recombinant murine interferon-gamma (rM IFN-gamma), recombinant human tumour necrosis factor (rH TNF), and recombinant human interleukin-2 (rH IL-2) in preclinical metastasis models. It was observed that these cytokines have disparate mechanisms of therapeutic activity as well as different optimal therapeutic protocols. Thus, not only is the dose important to the therapeutic activity of each of the agents; so also is the route of administration, schedule of administration, duration of administration, and sequence of administration. The rM IFN-gamma has a narrow window of activity, with a bell-shaped therapeutic response with a dosage optimum at 50,000 U/animal of rM IFN-gamma administered 3 times per week. In contrast, rH IL-2 has optimal therapeutic activity for the treatment of metastatic disease after i.p. as compared to i.v. administration. This appears to be associated with the serum pharmacokinetics, since longer serum concentrations are achieved following i.p. administration although lower serum levels are also achieved. RH IL-2 has a biphasic dose-response curve for therapeutic activity with optima from 100 to 1000 U/animal and at doses greater than 100,000 U/animal. The lower doses appear to be associated with T cell augmentation whereas the higher doses are associated with NK cell or LAK cell augmentation. RH TNF has therapeutic activity for the treatment of metastatic disease after i.v. but not i.p. administration. High levels of rH TNF are readily detected in the serum following i.v. administration, with a serum half-life of approximately 30 min. In contrast, only minimal serum TNF activity is observed after i.p. administration, suggesting that this may be the origin of the increased therapeutic activity following i.v. administration. Furthermore, rH TNF has additive therapeutic activity when administered in conjunction with suboptimal doses of rM IFN-gamma. Unfortunately, the additive therapeutic activity of rM IFN-gamma and rH TNF is also associated with increased toxicity. However, in preliminary experiments it was found that the b.i.d. administration of aspirin at 25 mg/kg resulted in decreased toxicity. In summary, the recombinant cytokines provide a challenge both preclinically and clinically to the development of optimal therapeutic protocols, and suggest that close attention must be paid to the dose, route, schedule, duration, and sequence of their administration. |
