Hexamethylmelamine: pharmacology and mechanism of action

Several conclusions can be drawn from a review of HMM preclinical and clinical pharmacology data. The drug is extensively metabolized by animals and by man. The drug is well absorbed following oral administration to animals, but oral bioavailability is low due to first pass metabolism. Based on limited human data and more complete animal data, absorption of HMM following oral administration may be quite high in man. We do not yet know the oral bioavailability of HMM in patients, but again based primarily on animal studies, oral bioavailability is most likely low and variable due to extensive first pass metabolism. Systemic exposure to HMM and demethylated metabolites following oral administration varies greatly from patient to patient and is sometimes quite low. Most patients are, however, exposed to a substantial fraction of the administered dose when determined by urinary recovery of the total dose (based on parent drug and metabolites or total radioactivity) or by the total plasma AUC of parent drug and all metabolites. Systemic exposure to HMM following intravenous administration is clearly greater and less variable than following oral administration. An unresolved question is whether the highly variable and often low systemic exposure after oral administration compromise antitumor activity when compared to intravenous administration. A key issue is whether or not one accepts the hypothesis that metabolism is a prerequisite for antitumor activity. The metabolic activation studies do not rule out other mechanisms of HMM antitumor activity. Modest activity of HMM was observed after prolonged exposure to cells which did not metabolize the drug. However, most of the accumulated data are consistent with the metabolic activation hypothesis. Certainly HMM has clinical activity when administered by mouth. If metabolism is required, then exposure to the total dose (parent drug and metabolites) could be of significance even when exposure to HMM is low, since every demethylated metabolite must have come ultimately from the initial HMM demethylation. We do not know whether the initial metabolic reaction (occurring in the liver rather than in the tumor) provides sufficient exposure of tumor to reactive species. Specifically, does the variable HMM plasma AUC seen after oral administration lead to variable delivery of potentially reactive species to tumor (by rapid breakdown and/or further metabolism of MPMM before it leaves the gut and/or liver) or are quantities of MPMM delivered to tumor comparable to those delivered following intravenous administration. The issue of rate of MPMM formation compared to rate of breakdown and ultimate delivery to tumor has been noted by Judson and Rutty.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of hexamethylmelamine in the management of ovarian cancer

Hexamethylmelamine has been recognized as having useful single-agent activity for the treatment of ovarian cancer for the past 25 years, with some patients surviving disease-free for periods in excess of 12 years. Data from recently analysed and mature trials demonstrate that the addition of hexamethylmelamine to first-line combination chemotherapy results in significant improvements in survival compared to what is achieved with regimens of cisplatin and cyclophosphamide with or without doxorubicin.

Analysis of prognostic factors and survival in patients with ovarian cancer treated with second-line hexamethylmelamine (altretamine)

Hexamethylmelamine (altretamine, HMM) 260 mg/m2/day p.o. for 14 days followed by a 14-day drug-free interval was administered to 52 outpatients with advanced ovarian cancer who had previously been treated with chemotherapy. Prior to HMM, 92% (48/52) of these patients had received cisplatin and cyclophosphamide with or without doxorubicin. Two more patients received other cisplatin-based regimens. At the completion of HMM therapy, 15% (8/52) displayed no evidence of disease (NED). Of these eight patients, five are still alive 32 to 82 months after altretamine therapy (median follow-up of 46 months). At 41 months, one patient died of intercurrent illness with no clinical evidence of recurrence; the other two patients died of their disease at 21 and 31 months following HMM therapy. The median survival of the total group was 11 months: nine months for patients who did not respond to altretamine and 46+ months for patients with NED after altretamine (p less than 0.05). Intermittent oral administration of single-agent altretamine was well tolerated: eight patients reported moderate gastrointestinal symptoms, and only one patient reported severe gastrointestinal symptoms. Moderate neurologic toxicity was reported by five patients. No WBC fell below 2000 mm3 and platelet counts fell below 100,000 mm3 in only three patients; no patient experienced severe hematologic toxicity. In this series of patients, the overall response (15%) was comparable to or better than those reported for more toxic chemotherapeutic regimens. On the basis of these data and those reported by other investigators, HMM warrants consideration as a reasonable option in the management of recurrent or persistent ovarian cancer.

Hexamethylmelamine: activity in lymphoma and other tumors

Hexamethylmelamine, an orally administered substituted melamine, has single agent activity in lymphoma (39% PR + CR), cervical cancer (28% PR), transitional carcinoma of the bladder (27% PR + CR), and Bilharzial bladder cancer (38% PR). Toxicity is mild and reversible and is manifested by myelosuppression, neurotoxicity and gastrointestinal toxicity. The potential role of hexamethylmelamine in combination chemotherapy in the diseases in which it has single agent activity is largely unexplored and should be investigated in clinical trials.

Altretamine

Altretamine is a National Cancer Institute-designated group C antineoplastic agent used in the treatment of advanced ovarian cancer. Altretamine is a highly lipid-soluble drug available only for oral administration as a capsule. The drug is activated through metabolic oxidation to intermediate methylol derivatives and formaldehyde. It is unclear which metabolite is the major species responsible for cytotoxicity or the primary mechanism of cytotoxicity. As a single agent in the treatment of ovarian cancer, altretamine demonstrates a response rate similar to other active agents in this disease (21-39 percent). The major utility of altretamine is in combination with other agents such as cyclophosphamide, doxorubicin, fluorouracil, melphalan, and cisplatin. However, few randomized trials have evaluated the contribution of altretamine in these multiagent combinations. Dose-limiting toxicities include gastrointestinal (nausea, vomiting, anorexia), hematologic, and neurotoxic (peripheral neurotoxicity). The therapeutic role of altretamine is limited because of a toxicity profile similar to that of cisplatin, one of the more active agents in ovarian cancer. Its use should be reserved for patients who are not candidates for more standard platinum-based regimens.

Prognostic factors in advanced epithelial ovarian cancer. (Gruppo Interregionale Cooperativo di Oncologia Ginecologica (GICOG))

The data on 914 patients enrolled in four randomised trials in advanced ovarian cancer, consecutively conducted by the same cooperative group between 1978 and 1986, were analysed with the aims of: (1) determining the impact of selected prognostic variables on survival; (2) finding, from the interaction of favourable prognostic factors and treatment, an approximate estimate of the magnitude of the survival advantage associated with the use of platinum-based combination chemotherapy. The overall 3-year survival in this series of patients is twice that reported historically (22%; 95% CL 18.7-25.4). The proportional hazard regression model was used to perform the analysis on survival. Residual tumour size, age, FIGO stage and cell type were all independent determinants of survival. Differences in survival from the various prognostic groups were impressive with 5-year survival rates ranging from 7 to 62%. However, these differences were not qualitative (i.e. the kinetics of survival were similar for the best and the worst groups) suggesting that current prognostic factors are of little use for selecting 'biologically' different sub-populations. Platinum-based regimens were associated to an overall prolonged median survival, but this benefit was not observable in the subgroup with most favourable prognosis (less than 2 cm residual tumour size). The implications of these observations for clinical research and ovarian cancer patients care are discussed.

Long-term follow-up of patients with advanced ovarian carcinoma treated with debulking surgery and chemotherapy consisting of cisplatin, doxorubicin, and cyclophosphamide. Gynecologic Oncology Group of the Comprehensive Cancer Center

Between June 1980 and December 1984, 88 patients with stage III-IV ovarian carcinoma were entered in a study evaluating the role of debulking surgery and chemotherapy consisting of cyclophosphamide, doxorubicin, and cisplatin intravenously on day 1, every 4 weeks (CAP-1). The results after a median follow-up of 62 months (range 41-93 months) are presented. The median survival of all patients was 24 months (30 alive, 58 dead). The 5-year progression-free survival of all patients was 27% and the overall survival was 33%. Of patients with stage III disease debulked to lesions less than or equal to 1.5 cm before the initiation of chemotherapy (n = 34) the 5-year progression-free survival was 52%. Of 31 patients with a histologically documented complete response the median survival was 55+ months; 9 (29%) of them relapsed as opposed to 8 of 10 achieving microscopic residual disease at second look. Of 22 patients with stage IV disease, 20 died. This report confirms that patients who have undergone surgical removal of of bulk tumor and who achieve a complete remission have an improved survival outcome.

Hexamethylmelamine as a single second-line agent in ovarian cancer

Fifty-two patients with advanced ovarian cancer were treated with single-agent hexamethylmelamine (HMM), 260 mg/m2 po per day for 14 days followed by 14 days off drug. All patients had been previously treated with chemotherapy. Of these patients, 92% (48/52) received cisplatin and cyclophosphamide +/- doxorubicin prior to hexamethylmelamine. Two additional patients received other cisplatin-based regimens. Fifteen percent (8/52) were found to have no evidence of disease (NED) at the completion of treatment with HMM. Five of these patients are alive at 12 to 65 months (median follow-up of 32 months); one patient died at 41 months of an intercurrent illness with no clinical evidence of recurrence; two patients died of recurrent tumor at 21 and 31 months. The median survival of the series of 52 patients is 11 months: 9 months for patients who did not respond versus 41 months for patients with NED post-HMM (P less than 0.05). The regimen was well tolerated: moderate gastrointestinal toxicity was reported by 8 patients; only one patient reported severe gastrointestinal toxicity. Moderate neurologic toxicity (primarily sensory) was reported by 5 patients, 3 patients experienced white counts less than 2000 or platelet counts less than 100,000, and no patient sustained severe hematologic toxicity. This moderate-dose intermittent regimen was associated with moderate toxicity and was well accepted by patients. The overall response is comparable to or higher than that reported for more toxic chemotherapy regimes. Based on these data and those recently reported by other authors, hexamethylmelamine should be considered in the treatment of recurrent ovarian cancer.

Concurrent chemotherapy and single high-dose plus whole abdominopelvic radiation for persistent ovarian carcinoma

Twenty-two patients were treated with concurrent single high-dose and standard fractionated abdominopelvic radiation and chemotherapy (cisplatin or hexamethylmelamine). Those who had prior cisplatin received hexamethylmelamine and radiation (16 patients) while those without prior cisplatin received cisplatin and radiation (6 patients). The primary aim of the study was to assess the tolerance and effectiveness of concurrent radiation and chemotherapy in patients who had failed prior chemotherapy. All patients experienced mild to moderate nausea, vomiting, and diarrhea. Hematologic adverse effects were minimal. Three patients requiring laparotomy for radiation induced small bowel obstruction had confirmed complete responses but 2 died acutely of treatment-related complications without evidence of tumor. In the 15 patients with suboptimal disease (greater than 1 cm residual disease) prior to the study, only 1 had a complete response while 2 of 7 optimal patients (less than or equal to 1 cm residual disease) had a complete response. All 3 complete responders received cisplatin and 2 had 1 cm or less of residual disease prior to the study. In the hexamethylmelamine group 3 of 16 patients had a partial response. Concurrent single high-dose whole abdominopelvic radiation and cisplatin may be effective in patients with minimal disease (less than or equal to 1 cm); however, radiation-associated bowel complications were severe.

Hexamethylmelamine as first-line chemotherapy in the treatment of advanced or recurrent carcinoma of the endometrium: a phase II trial of the Gynecologic Oncology Group

Thirty-eight patients with advanced or recurrent carcinoma of the endometrium who had received no prior chemotherapy were placed on study by the Gynecologic Oncology Group. One was deemed histologically ineligible. Three patients had insufficient trials to evaluate response. Of the remaining 34 who received hexamethylmelamine 280 mg/m2 orally daily on Days 1 through 14 of each 4-week course, there were only three objective responses, two complete and one partial. Although toxicity was tolerable, hexamethylmelamine has minimal activity in advanced or recurrent endometrial carcinoma at the dose and schedule tested.

Combined effects of host antitumor immune responses and chemotherapy. Studies with hexamethylmelamine

The antitumor activity of hexamethylmelamine (HMM) was tested in various mouse tumor models in the presence or absence of host-vs-tumor graft responses. The drug was moderately active against Sarcoma-180 growing in different strains of non-sensitized mice. Strong protection was afforded when recipients were preimmunized with irradiated tumor cells 15 days before tumor challenge followed by HMM treatment. The drug did not show antitumor activity against two radiation-induced lymphomas of congenic mice of B10 background, inoculated into H-2 compatible hosts, or into mice incompatible for subregions of H-2. In this model HMM increased mortality of allogeneic mice presumably through impairment of host-vs-lymphoma graft resistance. In conclusion this study shows that synergistic or antagonistic effects can be obtained by combining chemotherapy with antitumor immune responses.

Carboplatin in combination therapy for ovarian cancer

Cisplatin today is a cornerstone of combination chemotherapy for ovarian cancer. Carboplatin seems equal to cisplatin in antitumour activity, but has a different toxicity profile. After a feasibility study, a randomized phase III study in ovarian cancer stage II, III, and IV was undertaken, comparing carboplatin with cisplatin in combination with cyclophosphamide, doxorubicin and hexamethylmelamine. Preliminary analysis of this study reveals no statistically significant difference in response rate. Notwithstanding equal haematological toxicity, the other side effects evoked by carboplatin in combination treatment are much milder than those evoked by cisplatin. Further analysis will be necessary to draw definite conclusions about the results obtained.

Chemotherapeutic and surgical induction of pathological complete remission and whole abdominal irradiation for consolidation does not enhance the cure of stage III ovarian carcinoma

Thirty-eight patients with stage III ovarian carcinoma were treated with a protocol consisting of an initial phase of induction of remission with cyclophosphamide, hexamethylmelamine, doxorubicin, and cisplatin (CHAD) combination chemotherapy and a second laparotomy for resection of residual tumors, followed by a consolidation phase with curative doses of whole abdominal radiation. Six patients (16%) had stage IIIA disease, ten (26%) IIIB, and 22 (58%) had stage IIIC disease. All patients received three to 14 courses of CHAD chemotherapy with a clinical response rate (complete [CR] and partial [PR]) of 91%. Thirty-three patients underwent the second operation. In 14 patients no residual tumor was found, and in another 11 residual tumors found were totally resected. Thus, 25 of 33 (76%) were classified as in pathological complete remission (PCR) after this operation. Whole abdominal irradiation was well tolerated, although 12 of 29 (42%) of the irradiated patients required more than a 2-week interruption of the treatment course because of leukopenia and/or thrombocytopenia. The actuarial 5-year survival and disease-free survival rates for the whole group were 27% and 17%, respectively, and for the 29 patients who received the complete sequence of the prescribed protocol treatments, 35% and 20%, respectively. A univariate analysis of clinical parameters showed that inherent biological features, such as histology and grade, were the most dominant factors affecting prognosis, and that neither the aggressive surgical approach employed, nor the high-dose whole abdominal irradiation, significantly affected the outcome. The long-term results suggest that although our combined modality protocol was well tolerated, it failed to enhance the cure of stage III ovarian carcinoma. The possible biological and therapeutic vectors affecting this outcome are discussed.

Contribution of prednisone to the effectiveness of hexamethylmelamine in multiple myeloma

The Eastern Cooperative Oncology Group evaluated hexamethylmelamine in 89 patients with advanced refractory or relapsing multiple myeloma. Hexamethylmelamine was initially used as a single agent administered orally at 200 mg/m2/day for the first 3 weeks of each 4-week cycle. When this regimen proved to be ineffective, it was modified first by increasing the dose of hexamethylmelamine to 280 mg/m2/day and subsequently by adding prednisone at 75 mg for the first 7 days of each 28-day cycle. None of the 39 patients receiving hexamethylmelamine without prednisone had an objective response, while two patients had minimal objective improvement (25%-50% decrease in M protein with symptomatic improvement). Only 14% of these patients had objective or symptomatic response or both. In contrast, patients treated with hexamethylmelamine plus prednisone had a 22% objective response rate, with another 14% showing lesser degrees of objective improvement. Fifty-one percent of the patients treated with this regimen had either objective or symptomatic improvement or both. Severe (grade 3) toxicity was seen in nearly two-thirds of the patients on the higher-dose hexamethylmelamine regimens compared with 37% of the patients receiving low-dose hexamethylmelamine; however, in most instances this represented rapidly reversible cytopenias. Because all but one of the patients responding to hexamethylmelamine plus prednisone had experienced previous treatment failure on regimens containing prednisone in similar dose and schedules, it is unlikely that the responses are due to prednisone alone. Instead, this study suggests that the activity of hexamethylmelamine in multiple myeloma is dependent on the concomitant administration of prednisone and that the combination regimen appears to be synergistic.

Hexamethylmelamine in ovarian cancer after failure of cisplatin-based multiple-agent chemotherapy

A prospective study was initiated in 1979 to investigate the effect of hexamethylmelamine (HMM) as a second-line chemotherapeutic agent in the treatment of advanced adenocarcinoma of the ovary after failure of cisplatin-based multiple-agent chemotherapy. Of 20 evaluable patients, there were 5 patients (25%) who had objective responses (4 complete and 1 partial). Four additional patients have remained without evidence of disease. Six of these 9 patients are still alive, disease free. There were significant differences (P less than 0.001) in both the progression-free interval and survival time for these 9 patients, 13.3 and 15.1 months, respectively, as compared to the 15 nonresponders, 0.8 and 5.8 months, respectively. There was no significant difference in survival between the 4 patients with stable disease and the 11 patients with progressive disease. Performance status less than 2 (P less than 0.05) and absence of clinically measurable disease at the time of entry into the study (P less than 0.05) were found to be significant variables with regard to determining outcome. Only 2 of 24 patients suffered severe enough side effects from the HMM to warrant its discontinuation. This study demonstrates that HMM at doses of 6-8 mg/kg/day for 21 out of every 28 days can induce a complete response and provide an extended disease-free interval and prolonged survival with tolerable side effects in a significant number of patients with ovarian cancer who have previously failed cisplatin-based multiple-agent chemotherapy.

Hexamethylmelamine: a critical review of an active drug

Hexamethylmelamine is an s-triazine that began clinical trials during the 1960s based on its level of antitumor activity in murine tumor models. Phase I studies were performed using an oral formulation given in divided doses for varying numbers of days. The most frequently reported toxicities included nausea, vomiting, abdominal cramps, anorexia, weight loss and malaise. Less frequently reported toxicities were anemia, thrombocytopenia, leucopenia and peripheral neuropathy. Clinical antitumor activity was noted in the phase I studies in a variety of tumor types. Since then a large number of studies have been performed using hexamethylmelamine as a single agent and in a variety of combinations. Unfortunately, almost none of these studies sought to define the utility of this drug relative to other treatments for the diseases in which it showed activity, or to define the contribution of this drug to the activity of any given combination. Thus its role in the treatment of patients with malignancies remains undefined.

Superior efficacy of trimelamol to hexamethylmelamine in human ovarian cancer xenografts

A series of eight human ovarian cancer lines grown in nude mice were used to compare the activity of hexamethylmelamine (HMM) and N2,N4,N6-trihydroxy methyl-N2,N4,N6-trimethylmelamine (trimelamol). The tumor lines differed in histological subtype and growth rate. The drugs were administered i.p. at the maximum tolerated dose at alternate days. Differences in volume of treated and control tumors were endpoints of the study. The tumor lines varied widely in sensitivity to HMM and in four lines a T/C% below 25% was achieved. Trimelamol appeared to be more active than HMM and achieved a T/C below 25% in seven tumor lines. Thus far, the drug has demonstrated significant activity in a phase I trial in ovarian cancer patients. Comparative clinical studies of HMM vs trimelamol have not yet been performed.

Preclinical toxicology, pharmacokinetics and formulation of N2,N4,N6-trihydroxymethyl-N2,N4,N6-trimethylmelamine (trimelamol), a water-soluble cytotoxic s-triazine which does not require metabolic activation

N2,N4,N6-Trihydroxymethyl-N2,N4,N6-trimethylmelamine (Trimelamol) is a water-soluble synthetic s-triazine which, unlike hexamethylmelamine (HMM) and pentamethylmelamine (PMM), does not require metabolic activation. The physico-chemical characteristics of Trimelamol were studied with the aim of overcoming the problems of chemical instability, low solubility and polymerisation which had hindered the development of the drug for clinical use. Trimelamol had similar activity to PMM against the murine PC6 plasmacytoma, but enhanced activity with respect to PMM against the Walker 256 carcinosarcoma in the rat, a species which metabolizes PMM less efficiently. Pharmacokinetic studies in mouse, rat and man did not show the major species differences characteristic of PMM. The drug exhibited similar toxicity to PMM against rodents, but had virtually no neurotoxicity. The potential advantages of Trimelamol over previously tested melamines are discussed.