Pharmacokinetics and immunomodulatory effects on monocytes during prolonged therapy with liposomal muramyltripeptide

Pharmacokinetics and pharmacodynamics of liposomal mifamurtide in adult volunteers with mild or moderate renal impairment

AIMS

To evaluate the pharmacokinetics and pharmacodynamics following a single dose of liposomal mifamurtide (L-MTP-PE, MEPACT(®)) in adult subjects with mild (calculated creatinine clearance [CLcr ] of 50-80 ml min(-1)) or moderate (CLcr 30-50 ml min(-1)) renal impairment in comparison with age-, weight- and gender-matched healthy subjects with normal renal function (CLcr >80 ml min(-1)).

METHODS

Subjects received a 4 mg dose of liposomal mifamurtide via 1 h intravenous infusion. Blood samples were collected over 72 h for analysis of plasma pharmacokinetics of total and non-liposome-associated (free) mifamurtide and assessment of pharmacodynamics (changes in serum interleukin-6 [IL-6], tumour necrosis factor-α [TNF-α], C-reactive protein [CRP]).

RESULTS

Thirty-three subjects were enrolled: nine with mild renal impairment, eight with moderate renal impairment and 16 healthy subjects. Geometric mean (%CV) AUCinf for total mifamurtide was 89.5 (58.1), 94.8 (27.8), 85.1 (29.0), 95.4 (18.1) nM h in the mild renal impairment, mild-matched healthy subject, moderate renal impairment and moderate-matched healthy subject groups, respectively. Mifamurtide clearance was not correlated with CLcr, estimated glomerular filtration rate or iohexol clearance (all r(2) < 0.01). AUCinf of free mifamurtide was similar across the renal function groups. There were no readily apparent differences in serum pharmacodynamic effect parameters (baseline-adjusted AUEClast for IL-6 and TNF-α and Emax for CRP) between the renal function groups. No subjects reported grade ≥3 or serious adverse events.

CONCLUSIONS

Mild or moderate renal impairment does not alter the clinical pharmacokinetics or pharmacodynamics of mifamurtide. No dose modifications appear necessary for these patients based on clinical pharmacologic considerations.

Pharmacokinetics and pharmacodynamics of liposomal mifamurtide in adult volunteers with mild or moderate hepatic impairment

AIMS

To evaluate the pharmacokinetics and pharmacodynamics after a single dose of liposomal mifamurtide (liposomal muramyl tripeptide phospatidyl ethanolamine; MEPACT(®)) in adult subjects with mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment in comparison with age-, weight- and sex-matched healthy subjects with normal hepatic function.

METHODS

Subjects received a 4 mg dose of liposomal mifamurtide via 1 h intravenous infusion. Blood samples were collected over 72 h for pharmacokinetic and pharmacodynamic assessments (changes in serum interleukin-6, tumour necrosis factor-α and C-reactive protein).

RESULTS

Thirty-seven subjects were enrolled: nine with mild hepatic impairment, eight with moderate hepatic impairment and 20 matched healthy subjects. Geometric least-square mean ratios of total mifamurtide AUCinf for the mild hepatic impairment and moderate hepatic impairment groups vs. matched healthy subjects were 105% (90% confidence interval, 83.6-132%) and 119% (90% confidence interval, 94.1-151%), respectively, which are below the protocol-specified threshold (150%) to require development of dose-modification recommendations. Pharmacodynamic parameters for changes in serum interleukin-6 and tumour necrosis factor-α concentrations were generally similar across hepatic function groups. Mifamurtide-induced increases in serum C-reactive protein were attenuated in the moderate hepatic impairment group, consistent with the liver being the major organ of C-reactive protein synthesis. No grade ≥3 adverse events were seen in subjects administered mifamurtide (4 mg).

CONCLUSIONS

These results support the conclusion that mild or moderate hepatic impairment does not produce clinically meaningful effects on the clinical pharmacokinetics or pharmacodynamics of mifamurtide; no dose modifications are needed in these special patient populations based on clinical pharmacological considerations.

Toward a drug development path that targets metastatic progression in osteosarcoma

Despite successful primary tumor treatment, the development of pulmonary metastasis continues to be the most common cause of mortality in patients with osteosarcoma. A conventional drug development path requiring drugs to induce regression of established lesions has not led to improvements for patients with osteosarcoma in more than 30 years. On the basis of our growing understanding of metastasis biology, it is now reasonable and essential that we focus on developing therapeutics that target metastatic progression. To advance this agenda, a meeting of key opinion leaders and experts in the metastasis and osteosarcoma communities was convened in Bethesda, Maryland. The goal of this meeting was to provide a "Perspective" that would establish a preclinical translational path that could support the early evaluation of potential therapeutic agents that uniquely target the metastatic phenotype. Although focused on osteosarcoma, the need for this perspective is shared among many cancer types. The consensus achieved from the meeting included the following: the biology of metastatic progression is associated with metastasis-specific targets/processes that may not influence grossly detectable lesions; targeting of metastasis-specific processes is feasible; rigorous preclinical data are needed to support translation of metastasis-specific agents into human trials where regression of measurable disease is not an expected outcome; preclinical data should include an understanding of mechanism of action, validation of pharmacodynamic markers of effective exposure and response, the use of several murine models of effectiveness, and where feasible the inclusion of the dog with naturally occurring osteosarcoma to define the activity of new drugs in the micrometastatic disease setting.

Review of mifamurtide in the treatment of patients with osteosarcoma

Osteosarcoma is the most common primary malignant tumor of bone. The disease, however, is very rare with less than 2,000 expected patients at all age groups per year within the European Union and the United States of America. With multimodal therapy, which combines multiagent chemotherapy and complete resection of all macroscopically detectable tumors, about 60%–70% of patients with localized osteosarcoma can be cured. The prognosis, however, is still poor for patients with synchronous or metachronous metastatic or nonresectable primary disease, with reported 5-year event-free survival (EFS) rates of less than 30%. Overall, the EFS rate has been rather stable since the introduction of combination chemotherapy including doxorubicin, cisplatin, high-dose methotrexate with leukovorin rescue, and/or ifosfamide. Mifamurtide, a modulator of innate immunity, which activates macrophages and monocytes, which in turn release chemicals with potential tumoricidal effects, may help to control microscopic metastatic disease and has been safely given together with standard adjuvant chemotherapy to patients with high-grade osteosarcoma. Results of the recently published intergroup study 0133 trial from the Children’s Cancer and Pediatric Oncology Groups suggest that mifamurtide is a medicine that deserves further investigation in this orphan disease.

Mifamurtide: a review of its use in the treatment of osteosarcoma

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.

Muramyl tripeptide (mifamurtide) for the treatment of osteosarcoma

Osteosarcoma is an ultraorphan disease. There are approximately 1000 new patients diagnosed with osteosarcoma each year in the USA and Europe. Current treatment for osteosarcoma utilizes multiagent chemotherapy and surgical resection of all clinically detectable disease. Current treatments for osteosarcoma achieve 60-70% event-free survival (EFS) for patients with localized disease and approximately 20% EFS for patients who present with metastasis. These results have been stable for two decades. The addition of muramyl tripeptide (mifamurtide) to chemotherapy resulted in a trend towards improved EFS and a one-third reduction in the risk of death from osteosarcoma. Mifamurtide has been approved in Europe for the treatment of newly diagnosed osteosarcoma in combination with chemotherapy.

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.

Regional muramyl tripeptide phosphatidylethanolamine administration enhances hepatic immune function and tumor surveillance

BACKGROUND

Immune status of the liver may affect growth of liver metastases. We analyzed the ability of muramyl tripeptide phosphatidylethanolamine (MTP-PE), an immunomodulatory bacterial cell wall analog, to stimulate Kupffer cells (KCs) and protect against tumor growth, with or without an immunosuppressive partial hepatectomy (PH). Impact of MTP-PE's route of administration on KC function was assessed.

METHODS

Buffalo rats (n = 7 to 12/group) were treated with saline, 40 microg MTP-PE intraportally (portal) or intravenously (IV) and challenged with 5 x 10(5) hepatoma cells, and tumors counted on day 21. To assess MTP-PE's impact on KC stimulation in animals undergoing PH, a known stimulant of tumor cell growth, groups were treated with saline or MTP-PE and challenged with tumor and underwent 30% PH. KCs were harvested and analyzed for superoxide production. Statistical analysis was performed with Mann-Whitney U test or chi-square test.

RESULTS

MTP-PE-treated animals had fewer tumor nodules than control animals (19 vs 184, P <.005). MTP-PE-portal animals had fewer nodules than MTP-PE-IV (2 vs 36, P <.05). MTP-PE treatment before PH resulted in fewer tumor nodules compared with control animals (192 vs 276, P <. 05). MTP-PE administration increased macrophage superoxide production (20.6 +/- 2 vs 11.9 +/- 1.1 nmol/10(6) cells, P <.005).

CONCLUSIONS

MTP-PE improved KC function and decreased growth of microscopic tumor cells. MTP-PE's effects persist after an immunosuppressive hepatectomy. Portal administration was the most effective. MTP-PE administration may be useful as a neoadjuvant therapy for patients undergoing resection of liver malignancies.

In vitro and in vivo enhancement of canine pulmonary alveolar macrophage cytotoxic activity against canine osteosarcoma cells

The combination of chemotherapy with immunotherapy may offer an advantage over either therapy alone and provide a greater potential for total tumor eradication. Monocyte/macrophage-mediated tumor cell killing is a major mechanism of the host's defense against primary and/or metastatic neoplasia. We evaluated the tumoricidal activity against canine osteosarcoma cells of canine pulmonary alveolar macrophages (PAM) exposed in vitro to two recombinant canine (rc) cytokines (rcTNF alpha and rcIFN gamma). We also evaluated the in vivo tumoricidal activity of PAM from dogs treated with the macrophage activator, liposome-encapsulated muramyl tripeptide-phosphatidyl-ethanolamine (L-MTP-PE) alone or in combination with doxorubicin (DOX). This study demonstrated that rcTNF alpha and rcIFN gamma significantly enhance in vitro canine PAM cytotoxicity against canine osteosarcoma cells, and that PAM from dogs treated with DOX + L-MTP-PE have enhanced cytotoxic activity against osteosarcoma cells when compared to dogs treated with DOX or L-MTP-PE alone. These findings support the rationale for combining a chemotherapy agent with an immunotherapy agent for the treatment of metastatic disease, and suggest a role for TNF alpha and IFN gamma as agents for stimulating the antitumor activity of macrophages.

Clinical pharmacology of anticancer agents in relation to formulations and administration routes

In the past years, alternative administration routes and pharmaceutical formulations of anticancer agents have been investigated in order to improve conventional chemotherapy treatment. The impact of these adjustments on the pharmacokinetics and pharmacodynamics is discussed. A review of the literature shows many examples of alternative administration forms of anticancer agents with improved pharmacokinetics. Local administration routes have been investigated in order to reduce the systemic toxicity and to enhance the local efficacy of conventional chemotherapy. Oral administration of anticancer agents is preferred by patients for its convenience and its potential for outpatient treatment. In addition, oral administration facilitates a prolonged exposure to the cytotoxic agent. However, poor bioavailability and substantial interpatient variability are noted as limitations for oral chemotherapy. Increased tumour selectivity can also be achieved by the use of specific pharmaceutical formulations, such as liposomes and macromolecular drug conjugates. The composition of these formulations often determine the pharmacokinetic behaviour of the formulated drug. In conclusion, several alternative administration forms of anticancer agents have been designed in the past years, with the potential for improvement of conventional chemotherapy, however, more extensive clinical evaluation of these novel strategies is warranted to prove their real clinical value.

Prostaglandin E2 affects differently the release of inflammatory mediators from resident macrophages by LPS and muramyl tripeptides

LPS and MTP-PE (liposome-encapsulated N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L-alanine-2-:[1',2'dipalmitoyl -sni-glycero-3-(hydroxy-phosphoryl-oxyl)] etylamide) induce in liver macrophages a synthesis and release of TNF-alpha, nitric oxide and prostanoids. Both agents induce an expression of mRNA's encoding TNF-alpha, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and of corresponding proteins. LPS and MTP-PE induce a rapid activation of the extracellular regulated kinase (ERK) isoenzymes-1 and -2. Inhibition of map kinase isoenzymes leads to a decreased release of TNF-alpha, nitric oxide and prostaglandin (PG) E2 after both agents. The transcription factors NF-kappaB and AP-1 are strongly activated by LPS within 30 minutes. MTP-PE induces a weak activation of both transcription factors only after 5 hours. Inhibition of NF-kappaB inhibits the LPS- but not the MTP-PE-induced release of TNF-alpha, nitric oxide and PGE2. PGE2 release after LPS is higher than after MTP-PE. Exogenously added PGE2 inhibits the activation of map kinase and TNF-alpha release by LPS, but not by MTP-PE. Release of nitric oxide after LPS and MTP-PE is enhanced after prior addition of PGE2. PGD2 is without any effect. MTP-PE, but not LPS, induces a cytotoxicity of Kupffer cells against P815 tumor target cells. The MTP-PE-induced cytotoxicity is reduced by TNF-alpha neutralizing antibodies, indicating the involvement of TNF-alpha. Thus our results suggest that the different potencies of LPS and MTP-PE as immunomodulators probably result from different actions on Kupffer cells, resulting in differences in the amounts and kinetics of released TNF-alpha and PGE2, and that PGE2 plays an important regulatory role in the action of LPS, but not in the actions of MTP-PE.