[CANCER RESEARCH 50. 2979-2986. May 15. 1990| Phase I and Immunomodulatory Study of a Muramyl Peptide, Muramyl Tripeptide Phosphatidylethanolamine1 Walter J. Urba,2 Lynn C. Hartmann, Dan L. Longo, Ronald G. Steis, John W. Smith II, Igal Kedar, Stephen Creekmore, Mario Sznol, Kevin Gonion, William G. Kopp, Christoph Huber, Manfred Herold, W. Gregory Alvord, Sandra Snow, and Jeffrey W. Clark Program Resources, Inc. JW. ]. U., L. C. H., I. K., W. C. K.], Biological Response Modifiers Program, National Cancer Institute-Frederick Cancer Research Facility [D. L. L., R. G. S., J. W. S., S. C., K. C., J. W. C.], Frederick Memorial Hospital ¡S.S.J, Frederick, Maryland; CTEP, Bethesda, Mary-land [M. S.J; Department of Internal Medicine, L'niversity of Innsbruck, Innsbruck, Austria [C. H., M. H.J; and Data Management Services, Inc., Computer and Statistical Services, National Cancer Institute-Frederick Cancer Research Facility, Frederick, Maryland (W. C. A.] ABSTRACT Muramyl tripeptide phosphatidylethanolamine (MTP-PE; CGP 19835A from Ciba Geigy) is a synthetic muramyl tripeptide structurally related to bacterial cell wall constituents. MTP-PE activates monocytes in vitro to a tumoricidal state and has in vivo antitumor effects in animal models. We studied the toxicity and immunomodulatory effects of once weekly i.v. administration of liposomal-encapsulated MTP-PE for 8 weeks in 27 patients with advanced malignancies. Doses ranged from 0.1 to 2.7 mg/m2. No major tumor responses were seen; 11 patients had stable disease after 8 weeks of therapy and 3 continued on maintenance therapy because of minor tumor regressions and/or clinical improvement. MTP-PE at these doses was well tolerated. Shaking chills and fevers were the most common toxicities and occurred at all dose levels. There was no treatment-induced loss of performance status. Immunomodulatory studies revealed evidence of a biological effect on monocytes. C-reactive protein levels rose in the majority of patients with end-of-treatment values 2 to 10 times higher than baseline. Serum neopterin levels were consistently increased 24 h after MTP-PE administration and significant decreases in expression of two different types of Fc receptors on periph eral blood monocytes were noted 6 h after treatment. Although no major tumor responses were seen in this group of patients with advanced malignancies, MTP-PE was well tolerated and exerted biological effects on monocytes. Serum neopterin levels may be a useful marker for the biological effects of MTP-PE. INTRODUCTION Peripheral blood monocytes and tissue macrophages partici pate in various aspects of the immune system. They process antigen and present it to T-cells, and as effector cells, activated monocytes/macrophages can recognize and kill tumor cells (1). Activating monocytes to a tumoricidal state is one immuno- therapeutic approach to the treatment of cancer. Tumoricidal monocytes are selective for neoplastic cells in vitro (2) and can kill tumor cells despite their phenotypic heterogeneity and regardless of their growth rate or susceptibility to cytotoxic T- cells or natural killer cells (3). Moreover, tumor cell variants resistant to macrophage-mediated lysis evolve uncommonly, even under selective pressure (4). There are a variety of methods to activate monocytes. Lymphokines such as IFN-7,1 granulo- Received 8/21/89; revised 1/16/90. 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. 1This project has been funded at least in part with Federal funds from the Department of Health and Human Services under Contract N01-CO-74102. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the United States Government. 2To whom requests for reprints should be addressed. 3The abbreviations used: IFN-7, -y-interferon; MDP. muramyl dipeptide; MTP-PE, muramyl tripeptide phosphatidylethanolamine(/V-acetylmuramyl-L- alanyl-D-isoglutaminyi-L-alanylphosphatidylethanolamine); PT, prothrombin time; PTT, partial thromboplastin time; CrP, C-reactive protein; EKG, electro cardiogram; MTD, maximal tolerated dose; FcRI, high affinity IgG Fc receptor; FcRII, low affinity IgG Fc receptor; MFI, mean fluorescence intensity; RIA, radioimmunoassay. cyte-macrophage, and monocyte colony-stimulating factors, or the bacterial products Bacillus Calmette-Guérinand lipopoly- saccharide can deliver activating signals to monocytes (5). The muramyl dipeptides are structurally related to bacterial cell wall constituents and MDP is the smallest component of B. Calmette-Guérinthat retains adjuvant properties. MDP has potent monocyte-activating properties, but its use in vivo is limited by its short half-life and rapid renal excretion. Attempts at targeting delivery to monocytes by encapsulating MDP in liposomes were complicated by its rapid diffusion out of the liposome. Lipophilic muramyl tripeptide also has potent mon ocyte-activating properties and can be stably incorporated within liposomes (MTP-PE). Monocytes harvested from both normal donors and patients with colorectal cancer can be acti vated to lyse various tumor cell lines by in vitro exposure to MTP-PE (6, 7). In vivo administration of MTP-PE encapsu lated in liposomes has resulted in inhibition of tumor growth and prolonged survival in a number of animal models (8-10). On the basis of these observations, we performed a phase I study of MTP-PE incorporated into multilamellar lipid vesicles (liposomes) in patients with advanced malignancies. The objec tives of our study were: (a) to assess the safety of various doses of MTP-PE in humans; (b) to measure any immunological changes in cancer patients treated with MTP-PE; and (c) to record any antitumor effects. PATIENTS AND METHODS Patients. For entry into this study, all patients had to meet the following requirements: histologically proven malignancy other than hairy cell leukemia; previous failure of standard therapy or disease for which there is no standard therapy; age 18-70 years; Eastern Cooper ative Oncology Group performance score of 0-2; estimated survival of at least 3 months; measurable or évaluable disease; adequate physiolog ical function as judged by WBC > 4.000/mm3, granulocytes > 2.000/ mm1, platelets > 100,000/mm3, serum bilirubin < 1.5 mg/dl. serum creatinine < 1.5 mg/dl, aspartate aminotransferase < 75 lU/liter, and a plasma PT and PTT of <1.5 x normal, respectively. Patients were excluded for the following reasons: pregnancy; the presence of acute intercurrent illnesses, hepatitis B surface antigen, or antibodies to human immunodeficiency virus; major surgery, radiation therapy, chemotherapy, hormonal or immunotherapy within 3 weeks of study entry; a history of deep venous thrombosis; a history of a bleeding diathesis; hypertension; diabetes; documented coronary or peripheral arterial disease; or the presence of untreated brain métas tases. The pretreatment evaluation included the following: history and physical examination; complete blood count; chemistry profile; urinal- ysis; PT; PTT; fibrinogen; fibrin degradation products; CrP; antinuclear antibodies; rheumatoid factor; quantitative immunoglobulins; EKG; chest X-ray; and other radiological studies as required to evaluate the extent of tumor. The protocol was approved by the Institutional Review Boards of both the Clinical Oncology Program, Division of Cancer Treatment, National Cancer Institute, and the Frederick Cancer Re- 2979 Research. on November 11, 2015. © 1990 American Association for Cancer cancerres.aacrjournals.org Downloaded from