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Extrapolation of Experimental Safety Data to Humans: The Interleukin-6 Case
CLINICAL IMMUNOLOGY AND IMMUNOPATHOLOGY
Vol. 83, No. 1, April, pp. 15–17, 1997 Article No. II964305
Extrapolation of Experimental Safety Data to Humans: The Interleukin-6 Case M. KAMMU¨LLER
AND
B. RYFFEL
Sandoz Pharma, Drug Safety Department, Basel, Switzerland; and Institute of Pathology, Basel, Switzerland
ety of nonlymphoid cells (2). The IL-6 receptor consists of two proteins, the p80 binding protein and the gp130 signal transducing protein. IL-6 is produced by many different cell types and has a broad spectrum of biological activity: IL-6 plays an important role in the differentiation of B-cells, growth of myeloma, plasmacytoma, hybridoma cells, induction of IL-2 and IL-2 receptor expression, proliferation and differentiation of T-cells, enhancement of IL-3-induced colony formation in hematopoietic stem cells and maturation of megakaryocytes, synthesis of acute-phase proteins in the liver, mesangial cell growth, neural cell differentiation, and keratinocyte growth (3–5). Based on the broad biological activity it was predicted that the development of a specific therapy with rhIL-6 may be difficult. Furthermore, the introduction of the human IL-6 gene into mice caused plasmacytosis associated with polyclonal IgG1 increases in serum and mesangioproliferative glomerulonephritis (6).
Interleukin 6 (IL-6) has a broad spectrum of biological activities, which include stimulation of hemopoiesis, especially thrombopoiesis, of the immune response, proliferation of mesangium cells, and induction of acute-phase proteins in the liver. Therefore, the therapeutic use of IL-6 for any specific clinical indication, e.g., stimulation of thrombopoiesis in severe thrombocytopenia, may be complicated by nonspecific effects. Preclinical experimental investigations of the safety evaluation performed in primates and rodents showed that rhIL-6 is well tolerated. A two- to threefold increase in thrombocyte counts was observed along with an increase in acute-phase proteins and immunostimulation in the absence of target organ toxicity. Patients receiving rhIL-6, however, had a vigorous acute-phase response, with fever, anemia, and general malaise. Importantly, rhIL-6 administration did not cause mesangioproliferative nephritis or an uncontrolled lymphoproliferation as predicted from IL6 transgenic mice. Although preclinical investigations are in general quite predictive for humans, safety data should be extrapolated carefully, since important quantitative differences may occur. q 1997 Academic Press
SAFETY STUDIES OF rhIL-6 IN RODENTS
Based on the results with IL-6 transgenic mice we were interested in whether the administration of high doses of rhIL-6 in mice and rats would cause renal and lymphoproliferative disease. RhIL-6 was given as a continuous infusion over 10 days or daily by subcutaneous injections over 30 days to Wistar rats (7–9). The main findings were increased platelet counts, slight leukocytosis, and anemia. There was no evidence of hepato- or nephrotoxicity. The bone marrow was slightly hypercellular, and increased numbers and hyperploidy of megakaryocytes were seen. In the spleen the lymphoid follicles were slightly increased in size and there was evidence of increased extramedullary hemopoiesis (7, 8). The bioavailability of rhIL-6 was confirmed by ELISA. After an intravenous injection, rhIL-6 was rapidly eliminated; in contrast, subcutaneous administration resulted in a peak serum level between 30 and 120 min in the range of 50 ng/ml and was detectable in the circulation for a few hours (7). Since IL-6 transgenic mice developed glomerulonephritis (6), and since no glomerular disease was found after prolonged administration of rhIL-6 in experimen-
INTRODUCTION: BIOLOGY OF INTERLEUKIN-6
Interleukin 6 (IL-6) is a multifunctional cytokine produced by lymphoid and nonlymphoid cells of the body and has regulatory effects on the immune and hematopoietic systems (1–4). Human IL-6 is a glycoprotein consisting of 212 amino acids with a molecular mass of 21–28 kDa. The homology of the human IL-6 protein with murine and rat IL-6 is 42 and 58% at the protein level. The highest homology among human, murine, and rat IL-6 was found in the region containing the four cysteine residues, suggesting that this cysteinerich middle region of the protein may play a critical role in IL-6 activity. The homology in this region may explain the biologic activity of human IL-6 in rodents despite the limited sequence homology. IL-6 exerts its biologic effects through specific membrane receptors. IL-6 receptors are expressed on resting and activated lymphocytes, monocytes, and a vari15
AID
Clin 4305
/
a50d$$$141
02-26-97 09:57:11
0090-1229/97 $25.00 Copyright q 1997 by Academic Press All rights of reproduction in any form reserved.
clina
AP: Clin
16
SYMPOSIUM-IN-WRITING
tal toxicity studies, the absence of glomerulonephritis might have been due to reduced bioavailability by the formation of IL-6 neutralizing antibodies. Therefore, murine IL-6 was injected into mice. Long-term administration of the homologous protein to mice did not, however, cause glomerulonephritis (10). Interestingly, IL-6 aggravated the development of lupus nephritis in BxW-F1 mice, which is related to its immunostimulatory property, since cyclosporin was able to inhibit IL6-induced nephritis in BxW-F1 mice (10).
In conclusion, rhIL-6 was well tolerated by rodents and nonhuman primates. The desired pharmacodynamic effect (stimulation of thrombopoiesis and immunostimulation) occurred in the absence of renal or hepatic adverse effects. A vigorous acute-phase response was detected in the serum in the absence of fever, which was extensively analyzed in the marmoset (12, 13).
EXPERIMENTAL STUDIES IN NONHUMAN PRIMATES
Based on the absence of major adverse effects in preclinical investigations, it was assumed that the clinical use of rhIL-6 should be safe and well tolerated. While no severe target organ toxicity was identified and no glomerulonephritis developed during phase I and II clinical trials, rhIL-6 caused in many patients a distinct acute-phase response with malaise, headache, myalgia, fever, and anemia (14–16). Therefore, the acute-phase response induced by the administration of rhIL-6 is more important in patients than that observed in experimental studies.
Studies in healthy rhesus monkeys given daily subcutaneous injections of rhIL-6 confirmed again a thrombopoietic activity, as shown by a twofold increase in blood platelet counts and a distinct upregulation of acute-phase proteins in the serum at doses of 10 and 30 mg/kg/day (11). For the safety evaluation rhIL-6 was given at high doses (25, 100, and 500 mg/kg) subcutaneously to rhesus monkeys and marmosets for 4 weeks. The main objective of these studies was to exclude any adverse effect which was not predicted from the pharmacological property of this cytokine. Furthermore, we were interested in whether an excessive stimulation of hemopoiesis, especially thrombopoiesis, induction of acute-phase response, stimulation of the immune system, and effects on the renal mesangium cells by the prolonged administration of rhIL-6 might cause disease. Observations related to rhIL-6 administration were noted at 100 and 500 mg/kg and included pallor, erythema, dehydration, rough coat, decreased food consumption, and decreased body weight (9 and 15%, respectively). Total blood leukocytes (essentially segmented neutrophils and monocytes) were two- to threefold increased in all rhIL-6-administered animals. Platelet counts showed a slow increase reaching a maximum at 2 weeks, which was not sustained. The decline of thrombocyte counts was likely due to the formation of neutralizing antibodies. A slight anemia with increased reticulocyte counts was found in each group, but a dose dependence was apparent. The erythrocyte sedimentation rate and the g-globulin, a2-macroglobulin, and fibrinogen levels were increased, whereas serum albumin was decreased. These changes were expected, since IL-6 is known to induce an acute-phase reaction. Antibodies against rhIL-6 were found at all doses in every animal after sc administration over 4 weeks. In the liver minimal mononuclear infiltrates were found in the portal area without any sign of hepatocyte degeneration at 100 and 500 mg/kg. Examination of the kidneys did not reveal any glomerular pathology at light microscopy. The bone marrow was hypercellular, with essentially normal composition, but increased megakaryocyte numbers.
AID
Clin 4305
/
a50d$$$142
02-26-97 09:57:11
CLINICAL INVESTIGATIONS
CONCLUSION
IL-6 is a multifunctional cytokine which plays an important role in the immune response, hemopoiesis, and host defense. RhIL-6 was administered at high daily doses to mice, rats, and nonhuman primates. In all species IL-6 had an immunostimulatory and hemopoietic (especially on megakaryocytes) effect. An acutephase response was most pronounced in nonhuman primates, which was, however, not associated with any major histopathological liver change. Neutralizing antibodies were detected within 10 days of rhIL-6 administration in all species. By contrast, the acute-phase response appears to be dose-limiting in clinical therapy. Although an acute response was predicted from the experimental studies, the severity was underestimated. Therefore, data from preclinical studies may be extrapolated to humans, but there may be distinct quantitative differences. There is no evidence that IL-6 induces de novo glomerulonephritis. The risk of enhancing a lymphoproliferative disorder is likely inherent, as with any growth factor therapy. REFERENCES 1. Kishimoto, T., The biology of interleukin-6. Blood 74, 1–10, 1989. 2. Kishimoto, T., Akira, S., Narazaki, M., and Taga, T., Interleukin6 family of cytokines and gp130. Blood 86, 1243–1254, 1995. 3. Hirano, T., Akira, S., Taga, T., and Kishimoto, T., Biological and clinical aspects of interleukin 6. Immunol. Today 11, 443–449, 1990.
clina
AP: Clin
SYMPOSIUM-IN-WRITING 4. Van Snick, J., Interleukin-6: An overview. Annu. Rev. Immunol. 8, 253–278, 1990. 5. Le, J., and Vilcek, J., Interleukin 6: A multifunctional cytokine regulating immune reactions and the acute-phase protein response. Lab. Invest. 61, 588–602, 1989. 6. Suematsu, S., Matsuda, T., Aozasa, K., Akira, S., Nakano, M., Ohno, S., Hirano, T., and Kishimoto, T., IgG1 plasmacytosis in interleukin 6 transgenic mice. Proc. Natl. Acad. Sci. USA 86, 7547–7551, 1989. 7. Ryffel, B., Kammuller, M., Robison, R., and Myers, L., Pathology induced by interleukin-6. Toxicol. Lett. 311–319, 1992. 8. Ryffel, B., Mihatsch, M. J., and Woerly, G., Pathology induced by interleukin-6. Int. Rev. Exp. Pathol. 34, 79–89, 1993. 9. Kammu¨ller, M. E., Recombinant human interleukin-6: Safety issues of a pleiotropic growth factor. Toxicology 105, 91–107, 1995. 10. Ryffel, B., Car, B. D., Gunn, H., Roman, D., Hiestand, P., and Mihatsch, M. J., Interleukin-6 exacerbates glomerulonephritis in (NZB 1 NZW)F1 mice. Am. J. Pathol. 144, 927–937, 1994. 11. Myers, L. A., Boyce, J. T., and Robison, R. L., The tolerability and pharmacology of interleukin-6 administered in combination with GM-CSF or G-CSF in the rhesus monkey. Toxicology 101, 157–166, 1995. 12. Klug, S., Neubert, R., Stahlmann, R., Thiel, R., Ryffel, B., Car,
B. D., and Neubert, D., Effects of recombinant human interleukin 6 (rhIL-6) in marmosets (Callithrix jacchus). 1. General toxicity and hematological changes. Arch. Toxicol. 68, 619–631, 1994. 13. Ryffel, B., Car, B. D., Woerly, G., Weber, M., DiPadova, F., Kammuller, M., Klug, S., Neubert, R., and Neubert, D., Long-term interleukin-6 administration stimulates sustained thrombopoiesis and acute-phase protein synthesis in a small primate— the marmoset. Blood 83, 2093–2102, 1994. 14. Scheid, C., Young, R., McDermott, R., Fitzsimmons, L., Scarffe, J. H., and Stern, P. L., Immune function of patients receiving recombinant human interleukin-6 (IL-6) in a phase I clinical study: Induction of C-reactive protein and IgE and inhibition of natural killer and lymphokine-activated killer cell activity. Cancer Immunol. Immunother. 38, 119–126, 1994. 15. Weber, J., Gunn, H., Yang, J., Parkinson, D., Topalian, S., Schwartzentruber, D., Ettinghausen, S., Levitt, D., and Rosenberg, S. A., A phase I trial of intravenous interleukin-6 in patients with advanced cancer. J. Immunother. Emphasis Tumor Immunol. 15, 292–302, 1994. 16. van Gameren, M. M., Willemse, P. H., Mulder, N. H., Limburg, P. C., Groen, H. J., Vellenga, E., and de Vries, E. G., Effects of recombinant human interleukin-6 in cancer patients: A phase III study. Blood 84, 1434–1441, 1994.
Received November 6, 1996; accepted November 7, 1996
AID
Clin 4305
/
a50d$$$142
02-26-97 09:57:11
17
clina
AP: Clin
Vol. 83, No. 1, April, pp. 15–17, 1997 Article No. II964305
Extrapolation of Experimental Safety Data to Humans: The Interleukin-6 Case M. KAMMU¨LLER
AND
B. RYFFEL
Sandoz Pharma, Drug Safety Department, Basel, Switzerland; and Institute of Pathology, Basel, Switzerland
ety of nonlymphoid cells (2). The IL-6 receptor consists of two proteins, the p80 binding protein and the gp130 signal transducing protein. IL-6 is produced by many different cell types and has a broad spectrum of biological activity: IL-6 plays an important role in the differentiation of B-cells, growth of myeloma, plasmacytoma, hybridoma cells, induction of IL-2 and IL-2 receptor expression, proliferation and differentiation of T-cells, enhancement of IL-3-induced colony formation in hematopoietic stem cells and maturation of megakaryocytes, synthesis of acute-phase proteins in the liver, mesangial cell growth, neural cell differentiation, and keratinocyte growth (3–5). Based on the broad biological activity it was predicted that the development of a specific therapy with rhIL-6 may be difficult. Furthermore, the introduction of the human IL-6 gene into mice caused plasmacytosis associated with polyclonal IgG1 increases in serum and mesangioproliferative glomerulonephritis (6).
Interleukin 6 (IL-6) has a broad spectrum of biological activities, which include stimulation of hemopoiesis, especially thrombopoiesis, of the immune response, proliferation of mesangium cells, and induction of acute-phase proteins in the liver. Therefore, the therapeutic use of IL-6 for any specific clinical indication, e.g., stimulation of thrombopoiesis in severe thrombocytopenia, may be complicated by nonspecific effects. Preclinical experimental investigations of the safety evaluation performed in primates and rodents showed that rhIL-6 is well tolerated. A two- to threefold increase in thrombocyte counts was observed along with an increase in acute-phase proteins and immunostimulation in the absence of target organ toxicity. Patients receiving rhIL-6, however, had a vigorous acute-phase response, with fever, anemia, and general malaise. Importantly, rhIL-6 administration did not cause mesangioproliferative nephritis or an uncontrolled lymphoproliferation as predicted from IL6 transgenic mice. Although preclinical investigations are in general quite predictive for humans, safety data should be extrapolated carefully, since important quantitative differences may occur. q 1997 Academic Press
SAFETY STUDIES OF rhIL-6 IN RODENTS
Based on the results with IL-6 transgenic mice we were interested in whether the administration of high doses of rhIL-6 in mice and rats would cause renal and lymphoproliferative disease. RhIL-6 was given as a continuous infusion over 10 days or daily by subcutaneous injections over 30 days to Wistar rats (7–9). The main findings were increased platelet counts, slight leukocytosis, and anemia. There was no evidence of hepato- or nephrotoxicity. The bone marrow was slightly hypercellular, and increased numbers and hyperploidy of megakaryocytes were seen. In the spleen the lymphoid follicles were slightly increased in size and there was evidence of increased extramedullary hemopoiesis (7, 8). The bioavailability of rhIL-6 was confirmed by ELISA. After an intravenous injection, rhIL-6 was rapidly eliminated; in contrast, subcutaneous administration resulted in a peak serum level between 30 and 120 min in the range of 50 ng/ml and was detectable in the circulation for a few hours (7). Since IL-6 transgenic mice developed glomerulonephritis (6), and since no glomerular disease was found after prolonged administration of rhIL-6 in experimen-
INTRODUCTION: BIOLOGY OF INTERLEUKIN-6
Interleukin 6 (IL-6) is a multifunctional cytokine produced by lymphoid and nonlymphoid cells of the body and has regulatory effects on the immune and hematopoietic systems (1–4). Human IL-6 is a glycoprotein consisting of 212 amino acids with a molecular mass of 21–28 kDa. The homology of the human IL-6 protein with murine and rat IL-6 is 42 and 58% at the protein level. The highest homology among human, murine, and rat IL-6 was found in the region containing the four cysteine residues, suggesting that this cysteinerich middle region of the protein may play a critical role in IL-6 activity. The homology in this region may explain the biologic activity of human IL-6 in rodents despite the limited sequence homology. IL-6 exerts its biologic effects through specific membrane receptors. IL-6 receptors are expressed on resting and activated lymphocytes, monocytes, and a vari15
AID
Clin 4305
/
a50d$$$141
02-26-97 09:57:11
0090-1229/97 $25.00 Copyright q 1997 by Academic Press All rights of reproduction in any form reserved.
clina
AP: Clin
16
SYMPOSIUM-IN-WRITING
tal toxicity studies, the absence of glomerulonephritis might have been due to reduced bioavailability by the formation of IL-6 neutralizing antibodies. Therefore, murine IL-6 was injected into mice. Long-term administration of the homologous protein to mice did not, however, cause glomerulonephritis (10). Interestingly, IL-6 aggravated the development of lupus nephritis in BxW-F1 mice, which is related to its immunostimulatory property, since cyclosporin was able to inhibit IL6-induced nephritis in BxW-F1 mice (10).
In conclusion, rhIL-6 was well tolerated by rodents and nonhuman primates. The desired pharmacodynamic effect (stimulation of thrombopoiesis and immunostimulation) occurred in the absence of renal or hepatic adverse effects. A vigorous acute-phase response was detected in the serum in the absence of fever, which was extensively analyzed in the marmoset (12, 13).
EXPERIMENTAL STUDIES IN NONHUMAN PRIMATES
Based on the absence of major adverse effects in preclinical investigations, it was assumed that the clinical use of rhIL-6 should be safe and well tolerated. While no severe target organ toxicity was identified and no glomerulonephritis developed during phase I and II clinical trials, rhIL-6 caused in many patients a distinct acute-phase response with malaise, headache, myalgia, fever, and anemia (14–16). Therefore, the acute-phase response induced by the administration of rhIL-6 is more important in patients than that observed in experimental studies.
Studies in healthy rhesus monkeys given daily subcutaneous injections of rhIL-6 confirmed again a thrombopoietic activity, as shown by a twofold increase in blood platelet counts and a distinct upregulation of acute-phase proteins in the serum at doses of 10 and 30 mg/kg/day (11). For the safety evaluation rhIL-6 was given at high doses (25, 100, and 500 mg/kg) subcutaneously to rhesus monkeys and marmosets for 4 weeks. The main objective of these studies was to exclude any adverse effect which was not predicted from the pharmacological property of this cytokine. Furthermore, we were interested in whether an excessive stimulation of hemopoiesis, especially thrombopoiesis, induction of acute-phase response, stimulation of the immune system, and effects on the renal mesangium cells by the prolonged administration of rhIL-6 might cause disease. Observations related to rhIL-6 administration were noted at 100 and 500 mg/kg and included pallor, erythema, dehydration, rough coat, decreased food consumption, and decreased body weight (9 and 15%, respectively). Total blood leukocytes (essentially segmented neutrophils and monocytes) were two- to threefold increased in all rhIL-6-administered animals. Platelet counts showed a slow increase reaching a maximum at 2 weeks, which was not sustained. The decline of thrombocyte counts was likely due to the formation of neutralizing antibodies. A slight anemia with increased reticulocyte counts was found in each group, but a dose dependence was apparent. The erythrocyte sedimentation rate and the g-globulin, a2-macroglobulin, and fibrinogen levels were increased, whereas serum albumin was decreased. These changes were expected, since IL-6 is known to induce an acute-phase reaction. Antibodies against rhIL-6 were found at all doses in every animal after sc administration over 4 weeks. In the liver minimal mononuclear infiltrates were found in the portal area without any sign of hepatocyte degeneration at 100 and 500 mg/kg. Examination of the kidneys did not reveal any glomerular pathology at light microscopy. The bone marrow was hypercellular, with essentially normal composition, but increased megakaryocyte numbers.
AID
Clin 4305
/
a50d$$$142
02-26-97 09:57:11
CLINICAL INVESTIGATIONS
CONCLUSION
IL-6 is a multifunctional cytokine which plays an important role in the immune response, hemopoiesis, and host defense. RhIL-6 was administered at high daily doses to mice, rats, and nonhuman primates. In all species IL-6 had an immunostimulatory and hemopoietic (especially on megakaryocytes) effect. An acutephase response was most pronounced in nonhuman primates, which was, however, not associated with any major histopathological liver change. Neutralizing antibodies were detected within 10 days of rhIL-6 administration in all species. By contrast, the acute-phase response appears to be dose-limiting in clinical therapy. Although an acute response was predicted from the experimental studies, the severity was underestimated. Therefore, data from preclinical studies may be extrapolated to humans, but there may be distinct quantitative differences. There is no evidence that IL-6 induces de novo glomerulonephritis. The risk of enhancing a lymphoproliferative disorder is likely inherent, as with any growth factor therapy. REFERENCES 1. Kishimoto, T., The biology of interleukin-6. Blood 74, 1–10, 1989. 2. Kishimoto, T., Akira, S., Narazaki, M., and Taga, T., Interleukin6 family of cytokines and gp130. Blood 86, 1243–1254, 1995. 3. Hirano, T., Akira, S., Taga, T., and Kishimoto, T., Biological and clinical aspects of interleukin 6. Immunol. Today 11, 443–449, 1990.
clina
AP: Clin
SYMPOSIUM-IN-WRITING 4. Van Snick, J., Interleukin-6: An overview. Annu. Rev. Immunol. 8, 253–278, 1990. 5. Le, J., and Vilcek, J., Interleukin 6: A multifunctional cytokine regulating immune reactions and the acute-phase protein response. Lab. Invest. 61, 588–602, 1989. 6. Suematsu, S., Matsuda, T., Aozasa, K., Akira, S., Nakano, M., Ohno, S., Hirano, T., and Kishimoto, T., IgG1 plasmacytosis in interleukin 6 transgenic mice. Proc. Natl. Acad. Sci. USA 86, 7547–7551, 1989. 7. Ryffel, B., Kammuller, M., Robison, R., and Myers, L., Pathology induced by interleukin-6. Toxicol. Lett. 311–319, 1992. 8. Ryffel, B., Mihatsch, M. J., and Woerly, G., Pathology induced by interleukin-6. Int. Rev. Exp. Pathol. 34, 79–89, 1993. 9. Kammu¨ller, M. E., Recombinant human interleukin-6: Safety issues of a pleiotropic growth factor. Toxicology 105, 91–107, 1995. 10. Ryffel, B., Car, B. D., Gunn, H., Roman, D., Hiestand, P., and Mihatsch, M. J., Interleukin-6 exacerbates glomerulonephritis in (NZB 1 NZW)F1 mice. Am. J. Pathol. 144, 927–937, 1994. 11. Myers, L. A., Boyce, J. T., and Robison, R. L., The tolerability and pharmacology of interleukin-6 administered in combination with GM-CSF or G-CSF in the rhesus monkey. Toxicology 101, 157–166, 1995. 12. Klug, S., Neubert, R., Stahlmann, R., Thiel, R., Ryffel, B., Car,
B. D., and Neubert, D., Effects of recombinant human interleukin 6 (rhIL-6) in marmosets (Callithrix jacchus). 1. General toxicity and hematological changes. Arch. Toxicol. 68, 619–631, 1994. 13. Ryffel, B., Car, B. D., Woerly, G., Weber, M., DiPadova, F., Kammuller, M., Klug, S., Neubert, R., and Neubert, D., Long-term interleukin-6 administration stimulates sustained thrombopoiesis and acute-phase protein synthesis in a small primate— the marmoset. Blood 83, 2093–2102, 1994. 14. Scheid, C., Young, R., McDermott, R., Fitzsimmons, L., Scarffe, J. H., and Stern, P. L., Immune function of patients receiving recombinant human interleukin-6 (IL-6) in a phase I clinical study: Induction of C-reactive protein and IgE and inhibition of natural killer and lymphokine-activated killer cell activity. Cancer Immunol. Immunother. 38, 119–126, 1994. 15. Weber, J., Gunn, H., Yang, J., Parkinson, D., Topalian, S., Schwartzentruber, D., Ettinghausen, S., Levitt, D., and Rosenberg, S. A., A phase I trial of intravenous interleukin-6 in patients with advanced cancer. J. Immunother. Emphasis Tumor Immunol. 15, 292–302, 1994. 16. van Gameren, M. M., Willemse, P. H., Mulder, N. H., Limburg, P. C., Groen, H. J., Vellenga, E., and de Vries, E. G., Effects of recombinant human interleukin-6 in cancer patients: A phase III study. Blood 84, 1434–1441, 1994.
Received November 6, 1996; accepted November 7, 1996
AID
Clin 4305
/
a50d$$$142
02-26-97 09:57:11
17
clina
AP: Clin