Natural killer (NK) cells are believed to contribute to the clinical efficacy of cancer immunotherapy using recombinant interleukin-2 (rIL·2) in humans. In previous trials of high-dose i.v. rIL-2, however, no correlation has been established between circulating NK cells and treatment response. Between January 1989 and October 1990, we treated a total of 47 outpatients with advanced tumors using low-dose s.c. rIL·2 and interferon-α-2 (rIFN-α). Therapy consisted of a 2-day rIL·2 pulse at 18 million IU/m2/ day, followed by 6 weeks of rIL-2 (3.6 × 106-4.8 × 106 IU/m2/day × 5 days/week) and rIFN-α (5 × 106-6 × 106U/m2 × 3/week). Before and after therapy, we phenotypically evaluated circulating lymphocytes and correlated them with clinical response. During 6-week therapy, peripheral blood lymphocytes bearing the CD 5 6 (NK-cell-associated) surface antigen were increased significantly (p < 0.005) in treatment responders [complete response (CR) and partial response (PR), n = 10; 3.8-fold] and stable disease (SD) patients (n = 20; 2.1-fold), while patients with progressive disease (PD, n = 17) exhibited no significant expansion of circulating NK cells (p > 0.1). After one 6-week treatment cycle, CR/PR patients had significantly more peripheral NK cells, when compared with patients in SD (1.6-fold) and PD (1.9-fold) (p < 0.04). The overall number of circulating lymphocytes was also increased upon therapy (1.6-fold; p ≤ 0.001), but remained independent of response (p > 0.4). These data demonstrate that s.c. rIL·2 and s.c. rIFN-α produce a significant increase in peripheral blood NK cells; this expansion correlates significantly with treatment response in advanced tumor patients receiving long-term combination immunotherapy at outpatient doses.
High dose interleukin-2 alone or in combination with lymphokine activated killer (LAK) cells has demonstrated antitumor activity in a variety of malignant diseases. The currently formulated recombinant human interleukin-2 (IL-2) has limited solubility and short circulatory half life resulting in limited bioavailability. To improve the bioavailability of IL-2 the protein was covalently bound to activated Polyethylenglycol (PEG). We designed a phase I/II trial to evaluate the bioactivity of PEG-IL-2 in man, given as intravenous (iv) bolus injection every two weeks, and to determine safety, efficacy, and the maximum tolerated dose (MTD) in patients with advanced malignancies. Assessment of cytokine levels, phenotypic analyses and differential blood counts were performed to investigate the effects of PEG-IL-2 in-vivo. To compare in-vitro PEG-IL-2 activity to activities of IL-2 we evaluated proliferation, cytotolytic activity, morphology, and phenotype of cytokine activated lymphocytes. Among seven patients treated with PEG-IL-2, there was no objective remission, three patients exhibited stabilisation of disease. Four patients presented with further disease progression. Treatment-related toxicity was mild to moderate (mainly WHO grades I and II) in patients receiving dose levels up to 10 x 10(6) IU/m2 (maximum tolerated single dose in the outpatient setting). No toxic deaths occurred. In comparison to IL-2, the pharmacokinetic profile of PEG-IL-2 exhibited increased plasma levels and a decreased clearance (alpha and beta half-life estimates of 4 and 14 hours, respectively). The analysis of a variety of immunologic parameters demonstrated that PEG-IL-2 has significant biologic activity both in vitro, and in man.
We treated 17 patients who had progressive metastatic renal carcinoma with a combination of subcutaneous recombinant human interleukin-2 (administered every 12 hours, at 9.0 million IU/m2 on days one and two, followed by 1.8 million IU/m2, five days per week, over six consecutive weeks) and interferon-alpha 2b (given at 5 million U/m2 three times weekly, for six consecutive weeks). Treatment courses were repeated in patients presenting with stable or regressive disease after the six weeks of combination therapy (11 of 14 evaluable). Two and three of 14 evaluable patients achieved complete and partial remissions, respectively. Toxicity of this regimen was moderate, with local inflammation of the injection sites, grade I-II (WHO) fevers, chills, malaise, nausea/vomiting, and anorexia in more than two-thirds of the patients treated.
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