Summary Imiquimod is an orally active interferon inducer with anti-tumour activity in experimental animals. In this study the tolerability, toxicity and biological effects of daily oral imiquimod administration were investigated in 21 patients with refractory cancer. Patients were treated with doses of 25 mg, 50 mg, 100 mg or 200 mg on a projected 112 day course. Only three patients completed the course, all at the 50 mg dose.Treatment toxicities were dose related and mainly comprised flu-like symptoms, nausea and lymphopenia. Of the 21 patients, five received dose reductions and in five treatment was discontinued because of treatmentrelated toxicity. The biological activity of imiquimod was confirmed by significant and sustained rises in peripheral blood mononuclear cell (PBMC) 2-5A synthetase (2-5AS) levels at all doses. At 100 mg and 200 mg these occurred within the first 24 h of administration. Levels of neopterin and fi2-microglobulin (A32M) were also significantly elevated when assessed after three weeks' treatment. Interferon production was not demonstrated within the first 24 h of the initial dose but, following repeated doses, ten of the patients developed detectable serum interferon concentrations with a maximum value of 5600 IU ml recorded. Administration of imiquimod did not have any significant effect on serum levels of tumour necrosis factor (TNF) or interleukin 1 (IL-1), nor did it lead to development of detectable levels of antibodies to interferon.One mixed clinical response was observed after 4 weeks' treatment at 100 mg in a patient with renal cell cancer. Daily administration of imiquimod causes activation of the interferon production system but at higher doses results in unacceptable toxicity. Further investigation of imiquimod as an interferon-inducing agent in cancer patients is suggested at either the lower dose levels or employing alternative dosing schedules.

Summary Interleukin 2 (IL-2) immunotherapy has met with limited success in the treatment of renal cell carcinoma (RCC) and malignant melanoma (MM). However, non-responders still account for up to 80% of those patients receiving IL-2. A high concentration of soluble IL-2 receptor (sIL-2R) is commonly found in the blood of such patients. We investigated the possibility that high sIL-2R concentration pretreatment may interfere with the bioavailability of IL-2. The mean concentration of sIL-2R in plasma from patients with MM, RCC and head and neck cancer was 3378 U ml-', 8778 U ml-' and 764 U ml-' respectively, compared with 1315 U ml-' in plasma from healthy volunteers. Inclusion of plasma from patients with RCC and MM patient plasma in cytotoxic T-lymphocyte leukaemic (CTLL) cell/IL-2 assays inhibited the ability of CTLL cells to respond to IL-2, and an inverse correlation was found between the concentration of sIL-2R and the growth response of CTLL cell to IL-2 (r = -0.86, P = 0.003). Plasma with soluble IL-2R concentrations greater than 3000 U ml-' produced a reduction in cell growth of more than 50% when included in CTLL IL-2 assays. The addition of increasing concentrations of IL-2 to cultures containing suppressive plasma failed to restore CTLL cell growth response to normal. Failure to saturate sIL-2R by exogenous IL-2 addition therefore suggests that another factor, initially present at a concentration similar to the sIL-2R concentration, is responsible for the observed effect. Determination of the suppressive effect of patient plasma as presented here may allow more effective IL-2 dosing schedules.

We vaccinated metastatic melanoma patients with irradiated, autologous melanoma cells genetically engineered to secrete interleukin 2 (IL-2) to investigate whether an anti-tumor immune response would be induced. Melanoma cell cultures were established from surgical specimens and were engineered to secrete IL-2 by infection with recombinant retrovirus. Twelve patients were vaccinated subcutaneously one, two, or three times with approximately 10(7) irradiated, autologous, IL-2-secreting tumor cells. Treatment was well tolerated, with local reactions at 11 of 24 injection sites and minor systemic symptoms of fever and headache after 6 injections. One patient developed anti-tumor DTH after the first vaccination and showed an increased response after the second vaccination. Anti-autologous tumor CTLs could be detected prevaccination in the peripheral blood of seven patients and their activity increased after vaccination in four patients. No UICC-defined clinical responses were seen, but three patients had stable disease for 7-15 months, one of whom has not yet progressed (15+ months). Thus, patient vaccination with autologous, genetically engineered tumor cells is feasible and safe. Anti-tumor DTH and CTLs can be induced in some patients with such a vaccine.

The purpose of this study was to evaluate in a randomized phase II trial the efficacy and toxicity of combination biochemotherapy compared with chemotherapy alone in patients with metastatic melanoma. Sixty-five patients with metastatic melanoma (ECOG performance status 0 or 1) were randomized to receive intravenous BCNU 100 mg m(-2) (day 1, alternate courses), cisplatin 25 mg m(-2) (days 1-3), DTIC 220 mg m(-2) (days 1-3) and oral tamoxifen 40 mg (BCDT regimen) with (n = 35) or without (n = 30) subcutaneous interleukin 2 (IL-2) 18 x 10(6) iu t.d.s. (day - 2), 9 x 10(6) iu b.d. (day - 1 and 0) and interferon 2 alpha (IFN-alpha) 9 MU (days 1-3). Evidence for immune activation was determined by flow cytometric analysis of peripheral blood lymphocytes. Treatment was repeated every 4 weeks up to six courses depending on response. The overall response rate of BCDT with IL-2/IFN-alpha was 23% [95% confidence interval (CI) 10-40%] with one complete response (CR) and seven partial responses (PR), and for BCDT alone 27% (95% CI 12-46%) with eight PRs; the median durations of response were 2.8 months and 2.5 months respectively. Sites of response were similar in both groups. There was no difference between the two groups in progression-free survival or overall survival (median survival 5 months for BCDT with IL-2/IFNalpha and 5.5 months for BCDT alone). Although 3 days of subcutaneous IL-2 resulted in significant lymphopenia, evidence of immune activation was indicated by a significant rise in the percentage of CD56- (NK cells) and CD3/HLA-DR-positive (activated T cells) subsets, without any change in the percentage of CD4 or CD4 T-cell subsets. Toxicity assessment revealed a significantly higher incidence of severe thrombocytopenia in patients treated with combination chemotherapy than with chemotherapy alone (37% vs 13%, P = 0.03) and a higher incidence of grade 3/4 flu-like symptoms (20% vs 10%) and fatigue (26% vs 13%). The addition of subcutaneous IL-2 and IFNalpha to BCDT chemotherapy in a randomized phase II trial resulted in immune activation but did not improve response rates in patients with metastatic melanoma, and indeed may increase some treatment-related toxicity.

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