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Human central nervous system pharmacology of pentamethylmelamine and its metabolites
Abstract:
Pentamethylmelamine (PMM) 80 mg/m2 was administered I.V. to 8 patients during surgical resection of intracerebral tumors. PMM concentrations in tumors were generally much higher than concurrent plasma concentrations, ranging from undetectable (less than .01 micrograms/g) to as high as 4.47 micrograms/g and were much higher in malignant melanoma samples than in astrocytoma samples. PMM was barely detectable or undetectable in most samples of edematous brain tissue adjacent to intracerebral tumor and in temporalis muscle. The PMM metabolites tetramethylmelamine (TeMM), trimethylmelamine (TrMM), and dimethylmelamine (DMM) were each detectable in tumor samples from one or two patients. Monomethylmelamine (MMM) was present in tumor samples from all except one patient. MMM was noted in samples of edematous brain tissue adjacent to tumor from 4 of 8 patients. It was the only PMM metabolite found in brain. TrMM, DMM, and MMM but not PMM, and TeMM were found in tumor cyst fluid from a patient with an intracerebral malignant melanoma. Two patients receiving therapeutic doses of PMM had biopsies taken of subcutaneous malignant melanoma deposits. PMM was undetectable in samples from one patient but reached high concentrations in the other patient. In both patients, MMM was the major metabolite. There was no indication that PMM penetrated into extracerebral tumors more readily than into intracerebral tumors Cerebrospinal fluid (CSF) samples were obtained from one patient without neurological toxicity who received low doses of PMM and from 4 patients receiving high doses of PMM who had developed neurological toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Pentamethylmelamine (PMM) concentrates in brain tumors, particularly malignant melanoma, at higher levels than in plasma. Monomethylmelamine (MMM) is the primary metabolite found in brain tissue and tumors.
Area of Science:
- Pharmacokinetics
- Oncology
- Neuroscience
Background:
- Pentamethylmelamine (PMM) is an antineoplastic agent investigated for its potential in treating brain tumors.
- Understanding drug distribution and metabolism in the central nervous system is crucial for optimizing cancer therapy.
Purpose of the Study:
- To investigate the tissue distribution and metabolism of Pentamethylmelamine (PMM) in patients with intracerebral tumors.
- To compare PMM concentrations in tumor tissue, adjacent brain tissue, plasma, and cerebrospinal fluid (CSF).
Main Methods:
- Intravenous administration of PMM (80 mg/m2) to 8 patients undergoing surgical resection of intracerebral tumors.
- Analysis of PMM and its metabolites (TeMM, TrMM, DMM, MMM) in tumor samples, adjacent edematous brain tissue, temporalis muscle, and CSF.
- Biopsies of subcutaneous malignant melanoma deposits were also analyzed in two patients.
Main Results:
- PMM concentrations were significantly higher in tumor tissues compared to plasma, with higher levels observed in malignant melanoma than astrocytoma.
- Monomethylmelamine (MMM) was the predominant metabolite detected in tumor samples and was also found in adjacent brain tissue.
- PMM was generally undetectable in adjacent edematous brain tissue and muscle, but metabolites were present in tumor cyst fluid and CSF.
Conclusions:
- PMM exhibits preferential accumulation in intracerebral tumors, especially malignant melanoma.
- Monomethylmelamine (MMM) is a major metabolite and is present in both tumor and adjacent brain tissue, suggesting potential CNS activity.
- Further research is warranted to evaluate PMM's therapeutic efficacy and safety profile in brain tumor treatment.