Distinct Clinical and Laboratory Activity of Two Recombinant Interleukin-2 Preparations 1 Jacquelyn A. Hank, 2 Jean Surfus, Jacek Gan, Mark Albertini, Mary Lindstrom, Joan H. Schiller, Kirsten M. Hotton, Masoud Khorsand, 3 and Paul M. Sondel Departments of Human Oncology [J. A. H., J. S., J. G., P. M. S.], Pediatrics [P. M. S.], Genetics [P. M. S.], and Medicine [M. A., J. H. S., K. M. H., M. K.], and the Comprehensive Cancer Center [J. A. H., M. A., M. L., J. H. S., P. M. S.], University of Wisconsin, Madison, Wisconsin 53792 ABSTRACT Interleukin-2 (IL-2) is a potent lymphokine that acti- vates natural killer cells, T cells, and other cells of the immune system. Several distinct recombinant human IL-2 preparations have shown antitumor activity, particularly for renal cell cancer and melanoma. Somewhat distinct im- mune and clinical effects have been noted when different IL-2 preparations have been tested clinically; however, the regimens and doses used were not identical. To compare these more directly, we have evaluated two clinical recom- binant IL-2 preparations in vitro and in vivo using similar regimens and similar IUs of IL-2. We used the Food and Drug Administration-approved, commercially available Chiron IL-2 and the Hoffmann LaRoche (HLR) IL-2 sup- plied by the National Cancer Institute. Using equivalent IUs of IL-2, we noted quantitative differences in vitro and in vivo in the IL-2 activity of these two preparations. In patients receiving comparable IUs of the two preparations, HLR IL-2 induced the release of more soluble IL-2 receptor  into the serum than Chiron IL-2. In addition, more toxicities were noted in patients receiving 1.5  10 6 IU of HLR IL-2 than were seen in patients treated with 1.5  10 6 or even 4.5  10 6 IU of Chiron IL-2. These toxicities included fever, nausea and vomiting, and hepatic toxicity. In vitro prolifer- ative assays using IL-2-dependent human and murine cell lines indicated that the IU of HLR IL-2 was more effective than Chiron IL-2 at inducing tritiated thymidine incorpo- ration. Using flow cytometry, we also found quantitative differences in the ability of these two preparations to bind to IL-2 receptors. These findings indicate that 3–6 IU of Chiron IL-2 are required to induce the same biological effect as 1 IU of HLR IL-2. INTRODUCTION IL-2 4 is a 133 amino acid protein that is used clinically for cancer immunotherapy. The initial clinical studies of IL-2 eval- uated natural and recombinant preparations (1–3). When these studies were initiated, there was not a uniform standard for calibrating the various IL-2 preparations. Each preparation was calibrated against an “in house” standard, and individual com- panies defined their own units of IL-2. The International Stand- ard for IL-2 was established in 1988 (4). This standard is available in lyophilized form, 100 IU/vial, to calibrate and standardize other various IL-2 preparations. The IU is defined as the amount of IL-2 that induces 50% of maximal proliferation of an established IL-2-dependent cell line. Quantification of IL-2 content in other preparations is achieved by comparing dose- response curves for the standard and unknown sample using a parallel line analysis, or by computerized software such as the ALLFIT program (5). Clinical trials of IL-2 have used different IL-2 preparations, each individually calibrated to the International Standard. In addition, these different IL-2 preparations have been given using different schedule and dosing regimens. Unfortunately, there are no published data directly comparing the clinical effects of the different human recombinant IL-2 preparations. Recently, Lentsch et al. (6) noted significant differences when they com- pared systemic toxicities seen in mice given the same number of IUs of either the natural sequence IL-2 (nIL-2; HLR) or IL-2 with the serine amino acid substitution (ser-IL-2; Chiron). We have direct experience with two sequential clinical studies of recombinant IL-2 in which the same constant infusion IL-2 regimen was used in a similar patient population, and where reagent availability required changing from one recombinant product to another at the beginning of the second study. In the first study, using IL-2 manufactured by HLR and supplied by the Biological Resource Branch of the NCI, we determined that 1.5  10 6 IU/m 2 /day for 4 days/week for 3 weeks was a well tolerated, yet satisfactory outpatient dosing regimen (7). When Received 8/11/98; revised 11/2/98; accepted 11/9/98. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported by NIH Grants UO1-CA61498, U10-CA13539, RO1- CA32685, and RO1-CA68334 and American Cancer Society Grant RPG-82-001-16CM. 2 To whom requests for reprints should be addressed, at K4/454 CSC, 600 Highland Avenue, Madison, WI 53792. Phone: (608) 263-7262; Fax: (608) 263-4226. 3 Present address: ENMMC, Cancer Center, 405 West Country Club Road, Roswell, NM 88201. 4 The abbreviations used are: IL-2, interleukin-2; NK, natural killer; FDA, Food and Drug Administration; HLR, Hoffmann LaRoche; NCI, National Cancer Institute; BRMP, Biological Response Modifiers Pro- gram; GM-CSF, granulocyte-macrophage colony-stimulating factor; PBMC, peripheral blood mononuclear cell; PHA, phytohemagglutinin; AST, aspartate aminotransferase; LAK, lymphokine-activated killer; IL-2R, IL-2 receptor; sIL-2R, soluble IL-2R ; MTT, 3-(4,5-dimeth- ylthiazol-2yl)-2,5-diphenyltetrazolium bromide; MFI, mean fluores- cence intensity; dThd, thymidine; MTD, maximum tolerated dose; IU, international unit. 281 Vol. 5, 281–289, February 1999 Clinical Cancer Research Research. on October 8, 2021. © 1999 American Association for Cancer clincancerres.aacrjournals.org Downloaded from