Liposomal Muramyl Tripeptide Phosphatidylethanolamine Research Articles

Immunotherapy of Childhood Sarcomas.

Pediatric sarcomas are a heterogeneous group of malignant tumors of bone and soft tissue origin. Although more than 100 different histologic subtypes have been described, the majority of pediatric cases belong to the Ewing’s family of tumors, rhabdomyosarcoma and osteosarcoma. Most patients that present with localized stage are curable with surgery and/or chemotherapy; however, those with metastatic disease at diagnosis or those who experience a relapse continue to have a very poor prognosis. New therapies for these patients are urgently needed. Immunotherapy is an established treatment modality for both liquid and solid tumors, and in pediatrics, most notably for neuroblastoma and osteosarcoma. In the past, immunomodulatory agents such as interferon, interleukin-2, and liposomal-muramyl tripeptide phosphatidyl-ethanolamine have been tried, with some activity seen in subsets of patients; additionally, various cancer vaccines have been studied with possible benefit. Monoclonal antibody therapies against tumor antigens such as disialoganglioside GD2 or immune checkpoint targets such as CTLA-4 and PD-1 are being actively explored in pediatric sarcomas. Building on the success of adoptive T cell therapy for EBV-related lymphoma, strategies to redirect T cells using chimeric antigen receptors and bispecific antibodies are rapidly evolving with potential for the treatment of sarcomas. This review will focus on recent preclinical and clinical developments in targeted agents for pediatric sarcomas with emphasis on the immunobiology of immune checkpoints, immunoediting, tumor microenvironment, antibody engineering, cell engineering, and tumor vaccines. The future integration of antibody-based and cell-based therapies into an overall treatment strategy of sarcoma will be discussed.

Immunotherapy for Bone and Soft Tissue Sarcomas.

Although multimodal therapies including surgery, chemotherapy, and radiotherapy have improved clinical outcomes of patients with bone and soft tissue sarcomas, the prognosis of patients has plateaued over these 20 years. Immunotherapies have shown the effectiveness for several types of advanced tumors. Immunotherapies, such as cytokine therapies, vaccinations, and adoptive cell transfers, have also been investigated for bone and soft tissue sarcomas. Cytokine therapies with interleukin-2 or interferons have limited efficacy because of their cytotoxicities. Liposomal muramyl tripeptide phosphatidylethanolamine (L-MTP-PE), an activator of the innate immune system, has been approved as adjuvant therapeutics in combination with conventional chemotherapy in Europe, which has improved the 5-year overall survival of patients. Vaccinations and transfer of T cells transduced to express chimeric antigen receptors have shown some efficacy for sarcomas. Ipilimumab and nivolumab are monoclonal antibodies designed to inhibit immune checkpoint mechanisms. These antibodies have recently been shown to be effective for patients with melanoma and also investigated for patients with sarcomas. In this review, we provide an overview of various trials of immunotherapies for bone and soft tissue sarcomas, and discuss their potential as adjuvant therapies in combination with conventional therapies.

Muramyl tripeptide-phosphatidyl ethanolamine encapsulated in liposomes (L-MTP-PE) in the treatment of osteosarcoma.

Bacille Calmette-Guerin (BCG) has been used for decades as an immune stimulant to treat cancer. Early work by Fidler and Kleinerman identified muramyl dipeptide (MDP) as a critical component of the BCG cell wall which retained most of the immunostimulatory properties of the native BCG. Addition of a peptide to MDP resulted in muramyl tripeptide (MTP) which allowed incorporation into liposomal membranes. The resulting pharmaceutical, liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE or mifamurtide) showed activity in preclinical models of human cancers. Phase I studies documented the safety of the compound for human administration. These trials did not reach a maximally tolerated dose (MTD), and the dose chosen for phase II trials was a biologically optimized dose, not an MTD. Phase II studies showed decreased risk of further recurrence in patients who received mifamurtide after surgical ablation of metastatic osteosarcoma. A phase III prospective randomized trial demonstrated a statistically significant reduction in the risk of death from osteosarcoma when MTP was added to systemic chemotherapy for the treatment of localized osteosarcoma. The same trial allowed treatment of patients who presented with initially metastatic disease. While the overall and event-free survival was improved in patients with metastatic osteosarcoma who received L-MTP-PE, the sample size was small and the improvement did not achieve conventional statistical significance. From 2008 to 2012, patients with metastatic and recurrent osteosarcoma were given L-MTP-PE in an expanded access trial, and the results suggest a decreased risk of subsequent recurrence and death with the inclusion of L-MTP-PE in the treatment strategy for these high-risk patients.

Abstract 3980: The immunomodulatory agent L-MTP-PE induces activation and expansion of human γδ T cells capable of lysing osteosarcoma cells.

Abstract The outcome of patients with metastatic osteosarcoma remains poor despite aggressive multimodality therapy. Liposomal Muramyl Tripeptide Phosphatidyl Ethanolamine (L-MTP-PE) is a non-specific immune modulator that activates monocytes and macrophages and has shown antitumor activity in osteosarcoma. The mechanism of action of L-MTP-PE remains unresolved. Here we investigated the effects of the agent on lymphocyte subpopulations. Whole peripheral blood from 9 healthy donors were stimulated with L-MTP-PE for 24 hours. Compared to non-stimulated controls, a proliferative response of CD3+ lymphocytes was found (1.77±0.06 fold expansion, p=<0.001). The strongest effect was observed on the γδ TCR+ CD3+ T cell subpopulation which expanded 5.0±1.0 fold. To further evaluate the effects of L-MTP-PE on γδ T cell proliferation, mononuclear cells were isolated from peripheral blood of 5 healthy donors and cultured in the presence of L-MTP-PE. On day 11, γδ T cells had expanded 4.6±0.6 fold compared to medium-controls. Addition of interleukin-2 (IL-2) to the cultures increased expansion of γδ T cells up to 9.8±1.6. In comparison, the known γδ T-cell stimulatory aminobisphosphonate agent zoledronic acid (ZA) combined with IL-2 induced 25.8±7.2-fold expansion. γδ T cell stimulation by ZA was previously shown to involve inhibition of the mevalonate pathway enzyme farnesyl diphosphate synthase and subsequent increase of isopentyl pyrophosphate levels. To explore the mechanism of γδ T cell expansion by L-MTP-PE, coincubation experiments were repeated in the presence of the HMG-CoA reductase inhibitor mevastatin. Addition of mevastatin resulted in a 5.1±1.8-fold reduction of L-MTP-PE induced γδ T cell expansion, confirming a critical role of the mevalonate pathway in γδ T cell expansion and thus a mechanism comparable to ZA. To explore the in vitro antitumor activity of L-MTP-PE activated γδ T cells, 24 hour coincubation experiments were performed with the osteosarcoma cell lines HOS and SAOS on day 6 of cultures. In a flow-cytometry based cytotoxicity assay, substantial cytolysis of osteosarcoma cells from both cell lines was observed after coincubation with both L-MTP-PE- and L-MTP-PE/IL-2-stimulated γδ T cells. At an effector-to-target-ratio of 1:1, L-MTP-PE-stimulated γδ T cells reduced viable cell counts of HOS and SAOS to 41.4±2.7% and 54.0±7.6%, respectively, and L-MTP-PE/IL-2-stimulated γδ T cells decreased cell counts to 33.7±2.0% and 23.0±0.9%. In comparison, ZA/IL-2-stimulated γδ T cells resulted in reduced viability to 46.2±1.0% (HOS) and 38.9±3.8% (SAOS). We conclude that L-MTP-PE induces effective in vitro expansion of γδ T cells via a mechanisms involving the mevalonate pathway, in a manner similar to aminobisphosphonate agents. L-MTP-PE-activated γδ T cells have the potential to lyse osteosarcoma cells and may thus be involved in the antitumor effects of this agents. Citation Format: Sibylle Mellinghoff, Bianca Altvater, Uta Dirksen, Heribert Juergens, Claudia Rossig, Martina Ahlmann. The immunomodulatory agent L-MTP-PE induces activation and expansion of human γδ T cells capable of lysing osteosarcoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3980. doi:10.1158/1538-7445.AM2013-3980

1508P - Mifamurtide (L-MTP-PE) for Metastatic and Recurrent Osteosarcoma (OS): Survival and Safety Profile from a Patient Access Study

ABSTRACT Introduction and research objectives Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE; mifamurtide) is approved for treatment of non-metastatic osteosarcoma (OS) in Europe, Israel, and Mexico. The primary objective of MTP-OS-403 was to collect information regarding the safety and tolerability of MTP in patients with high-risk OS. The open label access study called for L-MTP-PE 2mg/m2 twice /week x 24 doses, then weekly (total doses= 48 in 9 months). OS patients could receive MTP as a single agent or with appropriate chemotherapy. Results As of April 2012, 202 patients were registered at 8 participating centers. Most had metastases at initial presentation or recurrent OS. Median age was 16 yr. Time from initial diagnosis to L-MTP-PE treatment was 29 +/- 23 months (median 24 mo). Although >88% had metastases, 27% had been resected to no evidence of disease (NED) before study entry. The most common Infusion related AE (IRAE) within 24 hours of infusion were chills (37%), fever (25%), nausea (21%), headache (19%), and fatigue (15%). The most common AE (grade 3-4) other than IRAE were chemotherapy-related and included thrombocytopenia (22%), neutropenia (19%), leukopenia (18%), febrile neutropenia (16%), lymphopenia (15%), and anaemia (15%). At MDACC, there was 1 episode of pleural effusion and one episode of pericardial effusion that were possibly L-MTP-PE related. The median number of L-MTP-PE doses given was 34 (mean 30.1 +/- 17.5); 32% of these high risk OS patients received 48 doses. As of April 2012 45% (90/202) of these high risk OS patients continue to be followed for survival. Conclusion The safety profile of L-MTP-PE in high-risk OS patients is consistent with the known toxicity of the product. The infusion related AEs were generally mild to moderate. Since survival benefit in high-grade OS from MTP may be related to disease burden (i.e. achieving NED status using local control measures such as surgery and/or radiotherapy), L-MTP-PE may be more effective when used in the adjuvant setting. A randomized multi-institutional clinical trial in OS patients presenting with metastases at diagnosis should be considered. Disclosure C. Oliva: Cristina Oliva is a Takeda employee. Y. Liu: I am a Millennium employee. All other authors have declared no conflicts of interest.

New treatment options for nonmetastatic osteosarcoma: focus on mifamurtide in adolescents

New treatment options for nonmetastatic osteosarcoma: focus on mifamurtide in adolescents Winston W Huh, Daniela Egas-Bejar, Peter M AndersonDivision of Pediatrics, The Children's Cancer Hospital of the University of Texas MD Anderson Cancer Center, Houston, TX, USAAbstract: New treatments are needed to improve the clinical outcome for patients with osteosarcoma. Liposomal muramyl tripeptide phosphatidylethanolamine (mifamurtide) is a synthetic peptidoglycan component packaged in multilamellar liposomes. Mifamurtide has been demonstrated to induce recruitment and activation of macrophages and monocytes of the host innate immune system, which leads to antitumoricidal activity. Early clinical trials have demonstrated the safety and tolerability of mifamurtide combined with chemotherapy, and one major study has demonstrated an overall survival benefit in patients with newly diagnosed nonmetastatic osteosarcoma. This review summarizes the mechanism of action, clinical results, and the optimal biologic dose, and raises potential questions for future development of mifamurtide.Keywords: osteosarcoma, childhood cancer, adolescent, sarcoma, immunotherapy, bone

Mifamurtide for the treatment of nonmetastatic osteosarcoma

Introduction: The standard treatment for osteosarcoma requires both macroscopic surgical wide resection and postoperative multi-drug chemotherapy in neoadjuvant and adjuvant settings. However, the 5-year event-free survival has remained at a plateau of 60 – 70% of patients with nonmetastatic osteosarcoma for more than 30 years.Areas covered: Mifamurtide (liposomal muramyl tripeptide phosphatidylethanolamine; L-MTP-PE) is a new agent. L-MTP-PE is a nonspecific immunomodulator, which is a synthetic analog of a component of bacterial cell walls. L-MTP-PE activates macrophages and monocytes as a potent activator of immune response in addition to standard chemotherapy. It also improves the overall survival from 70 to 78% and results in a one-third reduction in the risk of death from osteosarcoma. This review summarizes the most recent findings about L-MTP-PE and its therapeutic application for nonmetastatic osteosarcoma.Expert opinion: Recently, L-MTP-PE has been approved in Europe for the treatment of nonmetastatic osteosarcoma with chemotherapy. L-MTP-PE in combination with traditional treatment is expected to go mainstream and to be beneficial for patients with osteosarcoma. Information about potential benefit regarding mifamurtide use in the neoadjuvant setting (i.e., before surgery) and/or usefulness of L-MTP-PE in metastatic in relapsed and metastatic osteosarcoma requires analysis of expanded access and/or future clinical trials of L-MTP-PE in high-burden and low-burden situations.

Mifamurtide

Mifamurtide (liposomal muramyl tripeptide phosphatidyl ethanolamine; Mepact) is an immunomodulator with antitumor effects that appear to be mediated via activation of monocytes and macrophages. In the EU, mifamurtide is indicated in children, adolescents, and young adults for the treatment of high-grade, resectable, non-metastatic osteosarcoma after macroscopically complete surgical resection; it is administered by intravenous infusion in conjunction with postoperative multiagent chemotherapy. In the US, mifamurtide is currently an investigational agent that holds orphan drug status for the treatment of osteosarcoma. In a large, randomized, open-label, multicenter, phase III trial, the addition of adjuvant (postoperative) mifamurtide to three- or four-drug combination chemotherapy (doxorubicin, cisplatin, and high-dose methotrexate with, or without, ifosfamide) was associated with a statistically significant improvement in overall survival in patients with newly diagnosed, high-grade, non-metastatic, resectable osteosarcoma. The pattern of outcome was generally similar in a small cohort of patients with metastatic disease who were enrolled in this trial. Mifamurtide is generally well tolerated; adverse events attributed to administration of the drug include chills, fever, headache, nausea, and myalgias. Based on the available data, mifamurtide can be considered for inclusion in treatment protocols for localized osteosarcoma.

Mifamurtide in osteosarcoma - A practical review

Mifamurtide, also known as liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE), has been approved for the treatment of osteosarcoma in Europe. Mifamurtide's rational drug design employs MTP-PE for macrophage activation in a multilamellar liposome drug carrier, containing the synthetic phospholipids 1-palmitoyl-2-oleoyl phosphatidyl choline (POPC) and 1,2-dioleoyl phosphatidyl serine (OOPS). Although the drug is not cytotoxic towards normal or tumor cells in vitro, immune activation against osteosarcoma lung metastases in vivo accounts for mifamurtide's antiosteosarcoma effects. Phosphatidyl serine-containing lipids signal macrophage cells that have "flipped phosphatidyl serine" to the outer membrane after apoptosis (e.g., after damage of tumor cells from chemotherapy); thus, both mifamurtide's active and inactive ingredients target immune cells in the lungs. Mifamurtide administration has resulted in 8% and 13% improvement in 6- and 5-year overall survivals, when added to chemotherapy in nonmetastatic and metastatic patients with osteosarcoma, respectively. The short-term toxicities of mifamurtide (fever, headache, flu-like symptoms and rigors) are reduced or eliminated using ibuprofen (200 mg) as premedication for the first infusion; an algorithm for pre- and postmedication is presented. To date, no long-term side effects of mifamurtide have been reported. Compassionate access programs based in two major cancer centers (MD Anderson and Memorial Sloan-Kettering), have recently provided this potentially life-saving drug in North America. The experience with mifamurtide provides an outstanding example of successful cooperation among regulatory bodies and agencies, the pharmaceutical industry and pediatric oncologists to improve cancer care and outcomes for children and young people with a rare sarcoma.

Addition of muramyl tripeptide to chemotherapy for patients with newly diagnosed metastatic osteosarcoma

The addition of liposomal muramyl tripeptide phosphatidylethanolamine (MTP-PE) to chemotherapy has been shown to improve overall survival in patients with nonmetastatic osteosarcoma (OS). The authors report the results of addition of liposomal MTP-PE to chemotherapy for patients with metastatic OS. Intergroup-0133 was a prospective randomized phase 3 trial for the treatment of newly diagnosed patients with OS. The authors compared 3-drug chemotherapy with cisplatin, doxorubicin, and high-dose methotrexate (Regimen A) to the same 3 drugs with the addition of ifosfamide (Regimen B). The addition of liposomal MTP-PE to chemotherapy was evaluated. Five-year event-free survival (EFS) for patients who received liposomal MTP-PE (n = 46) was 42% versus 26% for those who did not (n = 45) (relative risk for liposomal MTP-PE, 0.72; P = .23; 95% confidence interval [CI], 0.42-1.2). The 5-year overall survival for patients who received MTP-PE versus no MTP-PE was 53% and 40%, respectively (relative risk for liposomal MTP-PE, 0.72; P = 0.27; 95% CI, 0.40-1.3). The comparison of Regimen A with Regimen B did not suggest a difference for EFS (35% vs 34%, respectively; relative risk for Regimen B, 1.07; P = .79; 95% CI, 0.62-1.8) or overall survival (52% vs 43%, respectively; relative risk for Regimen B, 1.1, P = .75; 95% CI, 0.61-2.0). When the metastatic cohort was considered in isolation, the addition of liposomal MTP-PE to chemotherapy did not achieve a statistically significant improvement in outcome. However, the pattern of outcome is similar to the pattern in nonmetastatic patients.

Well-defined and potent liposomal hepatitis B vaccines adjuvanted with lipophilic MDP derivatives

The characterization of immunological cascades of the innate immune system activated by invariant molecular structures termed as pathogen-associated molecular patterns recognized by pattern recognition receptors of macrophages and dendritic cells, have allowed the elucidation of the mechanisms underlying the immunomodulatory properties of adjuvants. Thus, adjuvant-active lipophilic analogues of N-acetyl muramyl dipeptide (MDP) were incorporated in liposomal hepatitis B surface antigen (HBsAg) formulations. The immunoreactivity of the formulations was evaluated by measuring anti-HBs, immunoglobulin G (IgG), and isotype antibody titer and compared with alum-adsorbed HBsAg formulation. The formulations were also evaluated for cell-mediated immune response by HBsAg-specific proliferation of splenocytes and simultaneous estimation of cytokines (interleukin-4 [IL-4], interferon-γ [IFN-γ]). Results indicate that the serum IgG and anti-HBs titer obtained after intramuscular administration of liposomal muramyl tripeptide–phosphatidylethanolamine (MTP-PE) and liposomal N-acetylmuramyl-l-alanyl-d-isoglutamine–glycerol dipalmitate (MDP-GDP) antigenic formulations were significantly higher. The incorporation of MTP-PE on the liposomal HBsAg increased the stimulation index (SI) four to five times as compared to plain HBsAg solution, and it also induced significantly higher Th1 cellular immune response with a predominant IFN-γ level. So it is the novel effective and potentially safe approach in which liposomes act as delivery vehicles for hepatitis B viral antigen to antigen-presenting cells and is ornamented with a biological response modifier that could activate these target cells to enhance the antigen presentation to T lymphocytes. From the Clinical Editor In this study, adjuvant-active lipophilic analogues on N-acetyl muramyl dipeptide (MDP) were incorporated in liposomal hepatitis B surface antigen (HBsAg) formulations. The immunoreactivity of the formulations was evaluated and found effective, leading to a potentially enhanced immune response against the delivered antigen.

Novel bone cancer drugs: investigational agents and control paradigms for primary bone sarcomas (Ewing's sarcoma and osteosarcoma)

Background: New investigational agents and chemotherapy regimens including cyclophosphamide + topotecan, temozolomide + irinotecan, and anti-IGF-1R antibodies in Ewing's sarcoma (ES) and liposomal muramyltripeptide phosphatidylethanolamine (L-MTP-PE), aerosol therapy, and bone-specific agents in osteosarcoma (OS) may improve survival and/or quality of life on ‘continuation’ therapy. Objective: Review of investigational approaches and control paradigms for recurrent or metastatic primary bone tumors. Methods: Analyze temozolomide + irinotecan data and review in the context of other newer approaches including antiangiogenesis, anti-IGF-1R antibodies and bisphosphonates for ES. Review some current state-of-the-art approaches for OS including L-MTP-PE, anti-IGF-1R inhibition, aerosol therapies and bone specific agents. Results/conclusion: L-MTP-PE with chemotherapy in OS has been shown to improve survival; compassionate access is available for recurrence and/or metastases. Aerosol therapy (granulocyte–macrophage colony stimulating factor, cisplatin, gemcitabine) for lung metastases is a promising approach to reduce systemic toxicity. The bone-specific agents including denosumab (anti-receptor activator of NF-κB ligand antibody) and bisphosphonates may have benefit against giant cell tumor, ES and OS. Anti-IGF-1R antibody SCH717454 has preclinical activity in OS but best effectiveness will most likely be in combination with chemotherapy earlier in therapy. Both temozolomide + irinotecan and cyclophosphamide + topotecan combinations are very active in ES and are likely to be tested with anti-IGF-1R antibodies against ES.

Liposomal muramyl tripeptide phosphatidyl ethanolamine: a safe and effective agent against osteosarcoma pulmonary metastases

Osteosarcoma is the most common form of primary malignant bone tumor. The use of chemotherapy drugs with many side effects, including high-dose methotrexate, doxorubicin, cisplatin and ifosfamide, has greatly improved osteosarcoma survival compared with surgery alone. However, for 20 years, overall survival remained at a plateau of 60–70% in nonmetastatic disease and 20–30% in metastatic osteosarcoma owing to lung metastases. Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE) is a new agent that improves overall osteosarcoma survival (chemotherapy without L-MTP-PE 70% versus with L-MTP-PE 78%; p = 0.03). L-MTP-PE offers additional benefit for osteosarcoma treatment in combination with chemotherapy, particularly ifosfamide-containing regimens. Clinical experience indicates that side effects such as fever are temporary and controlled or prevented with ibuprofen and/or acetoaminophen premedication; severe side effects are rare. Although surgery will remain the main approach for osteosarcoma treatment of lung metastases, L-MTP-PE combined with other modalities, including chemotherapy, appears to be of benefit in these patients as well.

Liposomal Muramyl Tripeptide Phosphatidyl Ethanolamine: Ifosfamide-Containing Chemotherapy In Osteosarcoma

Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE) is a synthetic biological investigational agent used for treating osteosarcoma. It has been used in both canine and human osteosarcoma to reduce pulmonary metastases, the most common pattern of treatment failure for sarcomas. L-MTP-PE has been well tolerated using the concept of biological cancer therapy during chemotherapy. The use of L-MTP-PE with ifosfamide is the best studied combination with single agent chemotherapy. This may represent a new treatment choice for osteosarcoma patients receiving ifosfamide. Such patients include those with a poor initial histological response to primary therapy and/or metastatic disease including pulmonary metastases. Reduction of side effects of L-MTP-PE, such as fever and/or flu-like symptoms, with ibuprofen has not reduced efficacy. Since improved symptom control is possible using drug combinations that are especially effective for delayed nausea, outpatient high-dose ifosfamide chemotherapy combined with L-MTP-PE may lead to a safe and effective therapy while maintaining the patients' quality of life.

Liposomal Muramyl Tripeptide Phosphatidylethanolamine: Targeting and Activating Macrophages for Adjuvant Treatment of Osteosarcoma

About one third of osteosarcoma patients develop lung metastasis refractory to chemotherapy. Recent studies indicate that biological response modifiers activating the patient's immune system may help controlling minimal residual disease via pathways distinct from those used by cytotoxic drugs, and therefore prove effective against tumor resistance. Muramyl tripeptide phosphatidylethanolamine (MTP-PE) is a synthetic lipophilic glycopeptide capable of activating monocytes and macrophages to a tumoricidal state. When intercalated in multilamellar liposomes (L-MTP-PE) and injected intravenously, it targets lung, liver, and spleen macrophages. Therapeutic activity of L-MTP-PE was demonstrated in several preclinical models of experimental lung metastasis and in clinical trials in dogs with osteosarcoma. Although macrophage activation was shown to be directly involved in the in vivo anti-metastatic activity of this molecule, cytokine and chemokine secretion by activated macrophages could induce recruitment and stimulation of other immune cells, which may in turn indirectly contribute to the anti-tumor effect. L-MTP-PE has undergone clinical development in humans. In early trials, most side effects of L-MTP-PE were minimal. L-MTP-PE showed signs of efficacy in treatment of patients with recurrent osteosarcoma and the encouraging results from phase II studies led to a phase III trial conducted by the Children's Oncology Group in patients with newly diagnosed high-grade osteosarcoma. Patients were treated with or without L-MTP-PE in combination with multi-drug chemotherapy in adjuvant setting; significantly higher overall survival and disease-free survival were observed in the group receiving L-MTP-PE.

Prospectively Planned Analysis of Data From a Phase III Study of Liposomal Muramyltripeptide Phosphatidylethanolamine in the Treatment of Osteosarcoma

Prospectively Planned Analysis of Data From a Phase III Study of Liposomal Muramyltripeptide Phosphatidylethanolamine in the Treatment of Osteosarcoma

Effect of liposomal muramyl tripeptide phosphatidylethanolamine and indomethacin on hematopoietic recovery in irradiated mice

The effects of liposomal muramyl tripeptide phosphatidylethanolamine (MTP-PE/MLV, radioprotective immunomodulator; 10 mg/kg) and indomethacin (INDO, inhibitor of prostaglandin production; 2 mg/kg) on post-irradiation recovery of hematopoietic functions in mice were investigated. Two agents with distinct radioprotective mechanisms were administered alone or in combination 24 h and 3 h before exposure to 7 Gy 60Co radiation. In the post-irradiation period (3-14 days) combined pre-treatment of mice accelerated recovery of bone marrow cellularity, weight of spleen and myelopoietic and erythropoietic activity in both hematopoietic organs, compared to treatment with MTP-PE/MLV or indomethacin alone. In the peripheral blood, improved radioprotective effects of combined drug administration were found in the recovery of reticulocytes and platelet count. No further significant differences in the recovery of leukocyte count were observed in the examined groups until post-irradiation day 14. Within the first 3-6 post-irradiation days, the bone marrow and peripheral blood smears of mice pre-treated with indomethacin alone or its combination with MTP-PE/MLV more frequently featured blast cells and large cells with abundant cytoplasm which could be considered the hematopoietic stem cells.

Involvement of T cells in enhanced resistance to Klebsiella pneumoniae septicemia in mice treated with liposome-encapsulated muramyl tripeptide phosphatidylethanolamine or gamma interferon.

We have previously shown that prophylactic administration of the liposome-encapsulated immunomodulating agents muramyl tripeptide phosphatidylethanolamine (MTPPE) and gamma interferon (IFN-gamma) results in strongly increased survival of mice from a normally lethal septicemia with Klebsiella pneumoniae. It was anticipated that the treatment acts on macrophages and nonspecifically augments host resistance to various infections. In the present study, we provide evidence for a key role for T cells in host defense potentiation by the liposomal immunomodulators toward K. pneumoniae septicemia. It is shown that both CD4 and CD8 cells are important in immunomodulation, most likely due to production of IFN-gamma. Depletion of circulating IFN-gamma resulted in strong reduction of the antimicrobial host defense activation. Administration of interleukin-10 resulted in decreased antimicrobial host defense activation by liposomal immunomodulators. Moreover, administration of liposomal immunomodulators was shown to induce predominantly T-helper type 1 (Th1) cell populations in the spleen. These findings indicate that immunomodulation with liposomal MTPPE and IFN-gamma favors Th1 and NK cell activation.

Single-organism model of host defense against infection: a novel immunotoxicologic approach to evaluate immunomodulatory drugs.

The immunotoxicologic effects of drugs on host defense have been studied widely using various animal models of infection. Here we describe a new approach to testing host defense by using a single organism (Candida albicans) in CBA/J mice. The model is configured to test 3 effector systems via different routes of inoculation to stimulate different effector arms of the immune response. Nonspecific immunity was evaluated by C. albicans colony-forming unit (CFU) count from the spleen at 2 hr (uptake) and > or = 22 hr (clearance) following intravenous inoculation. Cell-mediated immunity was assessed by CFU count from an intramuscular injection site 6 days postinoculation. Humoral immunity was assessed by anti-Candida antibody titer, following multiple subcutaneous immunizations with C. albicans. Finally, overall immunity was evaluated following intravenous injection using survival as the endpoint. Histopathological, immunohistochemical, and electron microscopic evaluation of selected tissues revealed the involvement of the expected cell types in the different effector systems. Several immunomodulatory drugs--dexamethasone, cyclosporine, liposomal muramyltripeptide phosphatidylethanolamine, and SK&F 105685--were evaluated in the C. albicans model. Dexamethasone impaired host defense against C. albicans by suppressing all endpoints measured. Similarly, cyclosporine showed broad immunosuppressive activity, with the exception of yeast uptake from the spleen. In contrast, muramyl tripeptide-phosphatidylethanolamine enhanced all but cell-mediated immunity to C. albicans. SK&F 105685 displayed both stimulatory and inhibitory effects on immune responses to the infection. Our studies demonstrate that a single organism-based approach can be a useful method for evaluating the immunological hazards of drugs on host resistance to infection.

Combined modality radioprotection: enhancement of survival and hematopoietic recovery in gamma-irradiated mice by the joint use of liposomal muramyl tripeptide phosphatidylethanolamine (mtp-pe) and indomethacin

We have reported previously [Fedoročko, P., Int. J. Radiat. Biol. 65:465, 1994] that liposomal muramyl tripeptidephosphatidyl ethanolamine (MTP-PE/MLV) given prior to irradiation results in augmented hemopoietic recovery and enhanced animal survival as evidenced by increased pluripotent stem cells (CFU-S) and progenitor cells committed to granulocyte and/or macrophage development (GM-CFC) or white blood cells, neutrophil counts, as well as by survival rates of lethally irradiated mice. In this report the effects of liposomal MTP-PE (radioprotective immunomodulator; 10 mg/kg i.p., 24 h before irradiation) and indomethacin (inhibitor of prostaglandin production; 2 mg/kg i.m., 24 h and 3 h before irradiation) were studied. Both of the agents were administered either alone or in combination. The results included the assessment of preirradiation hemopoietic effects of drugs and postirradiation hemopoietic recovery in terms of bone marrow cellularity, number of bone marrow GM-CFC, endogenous spleen colony formation (endoCFU-S), and the determination of the survival of lethally irradiated mice. Experimental evidence elevated by the increased preirradiation numbers of GM-CFC and hydroxyurea kill of GM-CFC as well as a simultaneous significant diminution in bone marrow cellularity indicated that the beneficial action of the combined treatment could be a consequence of increased cell proliferation in the hemopoietic tissue and mobilization with redistribution of stem cells from bone marrow into the circulation. In the postirradiation period (3–14 days), combined pretreatment of mice accelerated myelopoietic regeneration in the bone marrow compared to treatment with MTP-PE/MLV alone or indomethacin alone. Combined administration of MTP-PE/MLV (10 mg/kg, -24 h, i.p.) and indomethacin (2 mg/kg, -24 h and -3 h, i.m.) to mice, prior to lethal irradiation, exerted an additional radioprotective effect and protected 100% of the C57B1/6 mice.