Pharmacokinetics of oral and intravenous melphalan during routine treatment of multiple myeloma

Optimizing high dose melphalan

Melphalan, has been a major component of myeloma therapy since the 1950s. In the context of hematopoietic cell transplantation (HCT), high dose melphalan (HDM) is the most common conditioning regimen used due to its potent anti-myeloma effects and manageable toxicities. Common toxicities associated with HDM include myelosuppression, gastrointestinal issues, and mucositis. Established approaches to reduce these toxicities encompass dose modification, nausea prophylaxis with 5HT3 receptor antagonists, cryotherapy, amifostine use, and growth factors. Optimization of melphalan exposure through personalized dosing and its combination with other agents like busulfan, or bendamustine show promise. Propylene glycol-free melphalan (Evomela) represents a novel formulation aiming to enhance drug stability and reduce adverse effects. This review explores strategies to enhance the efficacy and mitigate the toxicity of HDM in multiple myeloma. Future directions involve exploring these strategies in clinical trials to improve the safety and efficacy of HDM, thereby enhancing outcomes for multiple myeloma patients undergoing autologous HCT.

Liposomal Formulation of a Melphalan Lipophilic Prodrug: Studies of Acute Toxicity, Tolerability, and Antitumor Efficacy

BACKGROUND

Recently we developed a scalable scheme of synthesis of melphalan ester conjugate with 1,2-dioleoyl-sn-glycerol (MlphDG) and a protocol for the fabrication of its lyophilized liposomal formulation.

OBJECTIVE

Herein we compared this new convenient in use formulation of MlphDG with parent drug Alkeran® in rats concerning several toxicological parameters and evaluated its antitumor efficacy in the model of breast cancer in mice.

METHOD

Liposomes of approximately 100 nm in diameter, consisting of egg phosphatidylcholine, soybean phosphatidylinositol, and MlphDG, or placebo liposomes without the drug were produced by extrusion and lyophilized. Alkeran® or liposomes recovered by the addition of water were injected into the tail vein of animals. Clinical examination of rats consisted of detailed inspection of the behavior, general status, and hematological parameters. Mice with transplanted breast cancer WNT-1 were subjected to multiple treatments with the drugs; tumor growth inhibition was assessed, together with cellular immunity parameters.

RESULTS

Liposomes showed approximately two times lower acute toxicity and better tolerability than Alkeran® in terms of behavioral criteria. The toxic effects of liposomes on hemopoiesis were manifested at higher doses than in the case of Alkeran®, proportionally to the difference in LD50 values. The formulation inhibited tumor growth significantly more effectively than Alkeran®, delaying the start of the exponential growth phase and exhibiting no additional toxic effects toward bone marrow.

CONCLUSION

Lower toxicity of the liposomal formulation of MlphDG promises improved quality of life for cancer patients in need of treatment with melphalan. Presumably, the list of indications for melphalan therapy could be extended.

Treatment of Multiple Myeloma and the Role of Melphalan in the Era of Modern Therapies-Current Research and Clinical Approaches

Multiple myeloma (MM) accounts for 10% of all hematological malignancies, and it is the second most common hematological neoplasm for which chemotherapy is an important pharmacological treatment. High dose melphalan followed by autologous stem cell transplantation remains the standard of treatment for transplant-eligible patients with MM. In this review, we describe aspects of the pharmacokinetics and pharmacodynamics of melphalan therapy and related compounds. In addition, we describe the use of melphalan in innovative therapies for the treatment of MM, including the development of drug carriers to reduce systemic toxicity, combination therapy to improve the effectiveness of cancer therapy, and the chemical modification of the melphalan molecule to improve antitumor activity.

Clinical pharmacokinetics of oral drugs in the treatment of multiple myeloma

Treatment of myeloma is a long-term treatment mainly based on all-oral combinations of drugs. Because oral drugs have a more complex pharmacokinetics compared with IV treatments, an appropriate knowledge of the factors that may alter their systemic exposure is of particular clinical relevance. Both drug-drug interactions, food-effect, and dose-adaptation in renal and hepatic impairment may influence the systemic drug levels with a potential impact on drug efficacy or safety. Moreover, a better control of drug exposure may improve the side effect profiles of these treatments with a favourable impact on patient compliance. Furthermore, as long-term treatments, these drugs may also alter the systemic exposure of coadministered medications in these rather old patients. The aim of this review was to identify the factors modifying the systemic exposure of oral drugs used in myeloma by focusing on the pharmacokinetic drug-drug interactions and the effects of renal and hepatic impairment and of food impact.

Inventory of oral anticancer agents: Pharmaceutical formulation aspects with focus on the solid dispersion technique

Dissolution from the pharmaceutical formulation is a prerequisite for complete and consistent absorption of any orally administered drug, including anticancer agents (oncolytics). Poor dissolution of an oncolytic can result in low oral bioavailability, high variability in blood concentrations and with that suboptimal or even failing therapy. This review discusses pharmaceutical formulation aspects and absorption pharmacokinetics of currently licensed orally administered oncolytics. In nearly half of orally dosed oncolytics poor dissolution is likely to play a major role in low and unpredictable absorption. Dissolution-limited drug absorption can be improved with a solid dispersion which is a formulation method that induces super-saturated drug dissolution and with that it enhances in vivo absorption. This review discusses formulation principles with focus on the solid dispersion technology and how it works to enhance drug absorption. There are currently three licensed orally dosed oncolytics formulated as a solid dispersion (everolimus, vemurafenib and regorafenib) and these formulations result in remarkably improved dissolution and absorption compared to what can be achieved with conventional formulations of the respective oncolytics. Because of the successful implementation of these three solid dispersion formulations, we encourage the application of this formulation method for poorly soluble oral oncolytics.

The interaction between oral melphalan and gastric antisecretory drugs: Impact on clinical efficacy and toxicity

The aim of the present study was to clarify whether gastric antisecretory drugs affect the clinical efficacy and toxicity of orally administered melphalan in patients with multiple myeloma. A total of 10 patients receiving bortezomib plus oral melphalan and prednisolone (VMP) therapy between December 2011 and November 2014 were analyzed retrospectively. The patients were divided into a control group (seven patients) and a concomitant group (three patients, who were also administered with gastric antisecretory drugs). The gastric antisecretory drugs included rabeprazole sodium (two patients) and famotidine (one patient). No significant differences between the groups were observed in either the characteristics of the patients or the VMP regimen. The levels of monoclonal protein (M protein) in the control group tended to decrease (with a VMP cycle-dependency), although they were primarily stable in the concomitant group. During the second and third VMP cycles, the levels of M protein were markedly lower in the control group compared with the concomitant group. All the patients in the control group achieved a partial response, whereas those in the concomitant group exhibited stable disease. Hematological toxicity levels were revealed to be comparable between the two groups, whereas gastrointestinal toxicity was more prevalent in the control group. In conclusion, the results of the present study suggested that the clinical efficacy of melphalan may be reduced by the co-administration of gastric antisecretory drugs. This interaction may result in decreased toxicity and clinical efficacy of melphalan.

Intravenous injection of bortezomib, melphalan and dexamethasone in refractory and relapsed multiple myeloma

BACKGROUND

A combination of bortezomib (1.3 mg/m(2)), melphalan (5 mg/m(2)), and dexamethasone (40 mg) (BMD), with all three drugs given as a contemporary intravenous administration, was retrospectively evaluated.

PATIENTS AND METHODS

Fifty previously treated (median 2 previous lines) patients with myeloma (33 relapsed and 17 refractory) were assessed. The first 19 patients were treated with a twice-a-week (days 1, 4, 8, 11, 'base' schedule) administration while, in the remaining 31 patients, the three drugs were administered once a week (days 1, 8, 15, 22, 'weekly' schedule).

RESULTS

Side-effects were predictable and manageable, with prominent haematological toxicity, and a better toxic profile in 'weekly' schedule (36% versus 66% in 'base' schedule). The overall response rate was 62%. After median follow-up of 24.5 months (range 2.7-50 months), the median progression-free survival (PFS) was 21.6 with no difference between the two schedules and the median overall survival (OS) was 33.8 months. Independently from the adopted schedule, we found that also in a cohort of relapsed/refractory patients achieving at least partial remission improved PFS (35.2 versus 9 months) and OS (unreached median versus 18 months).

CONCLUSION

Taken together, our observations suggest that BMD is an effective regimen in advanced myeloma patients with acceptable toxicity.

Fifty years of melphalan use in hematopoietic stem cell transplantation

Melphalan remains the most widely used agent in preparative regimens for hematopoietic stem cell transplantation (SCT). From its initial discovery more than 50 years ago, it has been gradually incorporated in the conditioning regimens for both autologous and allogeneic transplantations because of its myeloablative properties and broad antitumor effects as a DNA alkylating agent. Melphalan remains the mainstay conditioning for multiple myeloma and lymphomas, and it has been used successfully in preparative regimens of a variety of other hematological and nonhematological malignancies. The addition of newer agents to conditioning, such as bortezomib or lenalidomide for myeloma or clofarabine for myeloid malignancies, may improve antitumor effects for transplantation, whereas melphalan in combination with alemtuzumab may represent a backbone for future cellular therapy because of reliable engraftment and low toxicity profile. This review summarizes the development and the current use of this remarkable drug in hematopoietic SCT.

Redeployment-based drug screening identifies the anti-helminthic niclosamide as anti-myeloma therapy that also reduces free light chain production

Despite recent therapeutic advancements, multiple myeloma (MM) remains incurable and new therapies are needed, especially for the treatment of elderly and relapsed/refractory patients. We have screened a panel of 100 off-patent licensed oral drugs for anti-myeloma activity and identified niclosamide, an anti-helminthic. Niclosamide, at clinically achievable non-toxic concentrations, killed MM cell lines and primary MM cells as efficiently as or better than standard chemotherapy and existing anti-myeloma drugs individually or in combinations, with little impact on normal donor cells. Cell death was associated with markers of both apoptosis and autophagy. Importantly, niclosamide rapidly reduced free light chain (FLC) production by MM cell lines and primary MM. FLCs are a major cause of renal impairment in MM patients and light chain amyloid and FLC reduction is associated with reversal of tissue damage. Our data indicate that niclosamides anti-MM activity was mediated through the mitochondria with rapid loss of mitochondrial membrane potential, uncoupling of oxidative phosphorylation and production of mitochondrial superoxide. Niclosamide also modulated the nuclear factor-κB and STAT3 pathways in MM cells. In conclusion, our data indicate that MM cells can be selectively targeted using niclosamide while also reducing FLC secretion. Importantly, niclosamide is widely used at these concentrations with minimal toxicity.

Treatment with intravenous melphalan and dexamethasone is not able to overcome the poor prognosis of patients with newly diagnosed systemic light chain amyloidosis and severe cardiac involvement

Treatment with oral melphalan and dexamethasone (M-Dex) was reported to be effective and feasible in patients with systemic light chain amyloidosis (AL) not eligible for high-dose melphalan. We report on 61 patients with advanced AL who were treated with intravenous M-Dex as first-line therapy. Estimated median overall survival (OS) was 17.5 months. Seventeen patients (28%) died within 3 months, mostly of disease-related complications. In addition, nonhematologic toxicity of Common Terminology Criteria grade 3 or 4 was observed in 20 patients, whereas hematologic toxicity was low. Twenty-seven patients (44%) had hematologic response, including complete in 7 patients (11%) and partial remission in 20 patients (33%). Organ response was observed in 15 patients (25%). The amount of the involved free light chains in serum and Karnofsky Index at diagnosis significantly influenced OS. Plasma levels of the cardiac biomarkers before start of treatment and their increase after the third M-Dex cycle also were strong negative predictors of OS. These parameters might help to identify patients who will not benefit from M-Dex chemotherapy.

Population pharmacokinetics of melphalan and glutathione S-transferase polymorphisms in relation to side effects

Melphalan is associated with severe side effects such as mucositis, diarrhea, and myelosuppression. We investigated how much the individual severity of these side effects is predicted by pharmacokinetics. In addition, we studied glutathione S-transferase GSTM1, GSTT1, and GSTP1 polymorphisms in relation to adverse events. A high interindividual pharmacokinetic variability was observed in 84 patients. There was a linear correlation between creatinine and melphalan clearance (P=0.0004). Patients treated with a dose > or = 70 mg/m(2) had a 23-fold increased risk to develop mucositis (P<0.001) and a 12-fold increased risk to develop diarrhea (P<0.001) compared with lower doses. The GSTP1 codon 105 polymorphism may be relevant for development of mucositis and the GSTT1 deletion may predict diarrhea, but these findings require confirmation. Melphalan-induced side effects were significantly dependent only on dose. Therapeutic drug monitoring or genotyping for GST does not appear to be very helpful in optimizing therapy with melphalan.

Melphalan: old and new uses of a still master drug for multiple myeloma

The treatment of multiple myeloma has seen significant changes from the initial use of melphalan to the introduction of stem cell transplantation and, most recently, to the era of novel targeted agents. Melphalan still remains as a reference drug for combination regimens, including emerging newer therapeutic options, either used at a standard dose for initial or salvage treatments in patients who are not eligible for more intensive therapies, or in conjunction with new molecules within high-dose chemotherapy programs. In this review, the authors analyze old and novel regimens, including melphalan for the treatment of newly diagnosed or relapsed/resistant patients with multiple myeloma in the clinical settings of standard chemotherapy, as well as autologous or allogeneic stem cell transplantation.

Genetic polymorphisms in the amino acid transporters LAT1 and LAT2 in relation to the pharmacokinetics and side effects of melphalan

OBJECTIVES

Melphalan is widely used in the treatment of multiple myeloma. Pharmacokinetics of this alkylating drug shows high inter-individual variability. As melphalan is a phenylalanine derivative, the pharmacokinetic variability may be determined by genetic polymorphisms in the L-type amino acid transporters LAT1 (SLC7A5) and LAT2 (SLC7A8).

METHODS

Pharmacokinetics were analysed in 64 patients after first administration of intravenous melphalan. Severity of side effects was documented according to WHO criteria. Genomic DNA was analysed for polymorphisms in LAT1 and LAT2 by sequencing of the entire coding region, intron-exon boundaries and 2 kb upstream promoter region. Selected polymorphisms in the common heavy chain of both transporters, the protein 4F2hc (SLC3A2), were analysed by single nucleotide primer extension.

RESULTS

Melphalan pharmacokinetics was highly variable with up to 6.2-fold differences in total clearance. A total of 44 polymorphisms were identified in LAT1 and 21 polymorphisms in LAT2. From all variants, only five were in the coding region and only one heterozygous non-synonymous polymorphism (Ala94Thr) was found in LAT2. Numerous polymorphisms were found in the LAT1 and LAT2 5'-flanking regions but did not correlate with expression of the respective genes. No significant correlations could be observed between the polymorphisms in 4F2hc, LAT1, and LAT2 with melphalan pharmacokinetics or with melphalan side effects.

CONCLUSIONS

The study confirmed that these transporter genes are highly conserved, particularly in the coding sequences. Genetic variation in 4F2hc, LAT1, and LAT2 does not appear to be a major cause of inter-individual variability in pharmacokinetics and of adverse reactions to melphalan.

Autologous peripheral blood stem cell transplantation in multiple myeloma using oral versus I.V. melphalan

Autologous peripheral blood stem cell transplantation is the therapy of choice for the treatment of multiple myeloma (MM) patients younger than 70 years old. Between August 1993 and November 2004, 54 patients with MM were autografted after conditioning with high-dose oral melphalan 140 mg/m(2) in combination with etoposide and carmustine (28 patients) or with high-dose melphalan 200 mg/m(2) I.V. (26 patients). The oral and IV melphalan groups were comparable. There were no significant differences in disease-free survival (DFS) and overall survival (OS) between the groups; however, in patients transplanted in remission, OS and DFS were better in the I.V. melphalan group. Four good-prognostic factors were identified: interval between diagnosis and transplant <18 months, number of prior chemotherapy lines < or =2, remission status (complete or partial), and the use of I.V. melphalan. In conclusion, I.V. melphalan is the therapy of choice for conditioning patients with MM who are in remission.

Treatment of bendamustine and prednisone in patients with newly diagnosed multiple myeloma results in superior complete response rate, prolonged time to treatment failure and improved quality of life compared to treatment with melphalan and prednisone--a randomized phase III study of the East German Study Group of Hematology and Oncology (OSHO)

PURPOSE

This randomized phase III study compared bendamustine and prednisone (BP) to standard melphalan and prednisone (MP) treatment in previously untreated patients with multiple Myeloma (MM).

PATIENTS AND METHODS

To be included, patients had to have histologically and cytologically proven stage II with progressive diseases or stage III MM. They were randomly assigned to receive BP (n=68) or MP (n=63). The primary endpoint was the time to treatment failure (TTF). Secondary endpoints included survival, remission rate, toxicity and quality of life.

RESULTS

The overall response rate was 75% in the BP and 70% in the MP group. A significantly higher number of patients treated with BP achieved a complete remission than did patients receiving MP (32 vs. 13%; P=0.007), and the maximum response was achieved more rapidly in patients treated with BP compared to those receiving MP (6.8 vs. 8.7 cycles; P<0.02). TTF and remission duration were significantly longer in the BP group. Patients receiving BP had higher QoL scores and reported pain less frequently than patients receiving MP.

CONCLUSION

BP is superior to MP with respect to complete remission rate, TTF, cycles needed to achieve maximum remission and quality of life and should be considered the new standard in first-line treatment of MM patients not eligible for transplantation.

Myeloid clonogenic assays for comparison of the in vitro toxicity of alkylating agents

A battery of clonal assays for myeloid progenitor cells (HPP-CFC, CFU-gemm, CFU-gm, CFU-g) was utilized to evaluate the myelotoxicity of a series of alkylating agents representing the spectrum of clinical times to nadir. Bone marrow aspirates from normal volunteers were incubated with mechlorethamine, busulfan, melphalan, carmustine or lomustine for 1 h and then cultured in methylcellulose with 30% serum and cytokines. There was a concentration-dependent inhibition of colony formation and often a differential toxicity to the myeloid progenitors with the alkylators tested. On a molar basis, mechlorethamine and melphalan were the most toxic of the alkylator drugs to the myeloid precursors. The most sensitive progenitor was CFU-gemm with the lowest inhibitory concentration IC(70) concentrations for mechlorethamine, melphalan, carmustine and lomustine. Generally, there was great similarity for drug effects between CFU-g and CFU-gm with overlapping inhibition curves. HPP-CFC proved to be the least sensitive of the progenitors to the toxic actions of the drugs. While there was no correlation between the time to clinical neutropenic nadir and the most sensitive progenitor in the clonal assays, the CFU-gm assay remains a suitable method for determining the myelotoxic potential of cytotoxic agents.

Successful allogeneic blood stem cell transplantation for aplastic anemia in a patient with renal insufficiency requiring dialysis

A 27-year-old man with aplastic anemia and renal insufficiency requiring dialysis underwent allogeneic PBSCT. The preparative regimen consisted of melphalan, ATG and TLI. GVHD prophylaxis consisted of cyclosporine and prednisolone. He was dialyzed prior to administration of melphalan and at 24 and 72 h after it. Otherwise, the dialysis schedule was unchanged, at three times a week. Engraftment was rapid. Regimen-related toxicity was minimal. Pharmacokinetic parameters of melphalan were not significantly altered with its plasma half-life 1.5 h. Patients with renal failure can receive allogeneic HSCT, and a combination of melphalan, ATG and TLI may serve as an alternative to CY and ATG.

Current drug therapy for multiple myeloma

Recent years have witnessed tremendous advances in the molecular pathogenesis and management of multiple myeloma. Standard chemotherapy (melphalan and prednisone; MP) has been the mainstay of treatment of multiple myeloma for about 3 decades. However, it is no longer considered the 'gold standard', particularly for those patients who will subsequently undergo intensive chemotherapy with autologous or allogeneic peripheral blood stem cell (PBSC) or bone marrow transplantation (BMT), or for patients with refractory myeloma. A variety of induction combination chemotherapy regimens have been developed, some of which have demonstrated an improved response rate and duration and a superior 5-year survival rate when compared with standard chemotherapy. The early use of high dose chemotherapy with autologous PBSC support or BMT has significantly increased the complete remission rate, and has prolonged event-free sur vival and overall survival. Allogeneic bone marrow or PBSC transplantation may be a good option for selected patients with poor prognostic features. The role of interferon-alpha in multiple myeloma is still inconclusive despite many years of clinical evaluation. The clinical application of chemosensitising agents that can inhibit P-glycoprotein (P-gp) expression and function, and particularly the development of more potent P-gp modulators such as valspodar (PSC 833) and elacridar (GF120918) has made it possible to reverse multidrug resistance in some refractory patients and to enhance the efficacy of chemotherapeutic agents. Immunotherapeutic approaches to purging of autologous bone marrow or PBSC, or as adjuvant therapy for minimal residual disease, show great promise. Finally, a number of new therapies specifically designed to treat many of the complications of multiple myeloma are improving clinical outcomes and quality of life for these patients.

Diagnosis, prognosis, and standard treatment of multiple myeloma

The diagnosis of multiple myeloma (MM) is often difficult; most patients present with asymptomatic gammopathy. The only findings that confirm a diagnosis of MM are an elevation in the M-component or extension of the lytic bone lesions that are the hallmark of the disease. Tests that delineate plasma cell biology, such as plasma cell proliferation rate, are helpful; magnetic resonance imaging can disclose bone marrow lesions leading to subsequent osteolytic disease. After the diagnosis of MM has been established and prognostic factors identified, the appropriate therapy can be determined. Melphalan and prednisone are no longer considered to be the "gold standard" of therapy. In fact, this approach is suitable for less than half of patients with myeloma. This article presents guidelines for standard treatment options and examines the efficacy of new high-dose chemotherapy approaches.

Randomized comparison of etoposide pharmacokinetics after oral etoposide phosphate and oral etoposide

Etoposide phosphate is a water-soluble prodrug of etoposide. The plasma pharmacokinetics of etoposide following oral administration of etoposide phosphate or oral etoposide were compared. Seventeen patients with solid tumours were enrolled to receive oral etoposide phosphate 125 mg m(-2) on days 1-5 every 3 weeks, with escalation to 175 mg m(-2) from course 3 when possible. Patients were randomized to receive oral etoposide phosphate or oral etoposide on day 1 of course 1 and the alternative compound on day 1 of course 2. Fifteen patients received two or more courses and were evaluable for pharmacokinetic comparisons. The median AUC(inf) (area under the concentration vs time curve from zero to infinity) of etoposide was 77.7 mg l(-1) h after etoposide phosphate (95% CI 61.3-100.5) and 62.0 mg l(-1) h after oral etoposide (95% CI 52.2-76.9). The difference in favour of etoposide phosphate was borderline significant: median 9.9 mg l(-1) h (95% CI 0.1-32.8 mg l(-1) h; P = 0.05). However, the inter-patient variability of etoposide AUC(inf) was not improved (coefficients of variation 42.3% and 48.4%). Etoposide phosphate was undetectable in plasma after oral administration. Toxicities of oral etoposide phosphate were not different from those known for etoposide. In conclusion, oral etoposide phosphate does not offer a clinically relevant benefit over oral etoposide.

The role of chemotherapy in the treatment of multiple myeloma

Plasma cell neoplasms often present in an asymptomatic, stable phase. Treatment should not be started until manifestations, such as bone pain, increased susceptibility to infections, renal failure, anaemia and weight loss, announce that the disease has progressed to the MM phase. Conventional therapy with melphalan and prednisone results in objective improvement in about 50% of patients and improves median survival to about 32 months from the start of treatment. Induction therapy should be continued until the M-protein reaches a stable plateau that lasts for at least 4 months. Maintenance therapy with melphalan prolongs the duration of the initial response, but does not improve overall survival, in comparison with patients receiving no maintenance therapy, because survival following relapse is shortened in those receiving maintenance melphalan. In two randomized clinical trials, maintenance treatment with interferon alpha prolonged remissions durations and overall survival of MM patients who responded to induction chemotherapy. Second-line treatment for MM patients who are primary refractory to melphalan, and for those who respond initially and then relapse with refractory disease, is outlined. Although long-term control is possible for a minority of patients, it is unlikely that MM can be cured with currently available chemotherapeutic agents. We need to learn more about the basic biology of the disease.

Phase II study of intravenous melphalan (NSC-8806) in the treatment of patients with advanced squamous carcinoma of the head and neck

The Illinois Cancer Center entered 25 patients on a phase II trial of intravenous melphalan treating patients with recurrent, metastatic or locally advanced and inoperable squamous cell carcinoma of the head and neck. All patients had bi-dimensionally measurable disease, at least a sixty day life expectancy, and adequate performance status (ECOG scale < or = 2). All patients except one had received prior radiotherapy, chemotherapy or both. Melphalan dosage was 30 mg/m2 every three weeks. Twenty-four patients were evaluable for response. One patient with laryngeal carcinoma had a clinical complete response of a nodal metastasis. Four patients had stabilization of disease for one to three months. There was formidable toxicity, including neutropenia (ANC < 1000/microliters 36%), and thrombocytopenia (< 50,000/microliter 32%). There were no drug-related deaths. Melphalan administered intravenously does not appear to be efficacious therapy in patients with previously treated advanced head and neck squamous carcinomas.

Glutathione depletion increases the cytotoxicity of melphalan to PC-3, an androgen-insensitive prostate cancer cell line

Prostate cancer that is androgen-insensitive is unresponsive to a wide spectrum of cytotoxic agents, including all of the alkylating agents. Since a major pathway for the detoxification of the alkylating agents is conjugation with glutathione (GSH), GSH depletion has proved to be effective as a technique to restore melphalan sensitivity in melphalan-resistant cancer cell lines. However, the effect of GSH depletion has not been widely studied in tumor cell lines that have not developed resistance due to previous exposure to alkylating agents. Thus, we decided to investigate GSH depletion as a technique to increase melphalan cytotoxicity to PC-3 cells, an androgen-insensitive prostate cancer line. After 2 and 6 h incubation with 0.25-5 microM melphalan, virtually no effect was observed on either clonogenic lethality or MTT viability until 5 microM exposures. A 24-h incubation of the cells with 100 microM buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, reduced the GSH content by 70%-75%. Following GSH depletion, an increase in clonogenic lethality and a decrease in MTT viability occurred after exposure to concentrations as low as 0.25 microM. The dose modification factor ranged from 2.9 after 2 h incubation to 4.5 at 6 h. These results provide support for additional studies in prostate cancer for further investigation of GSH depletion as a technique to induce sensitivity to alkylating agents in this chemotherapy-resistant tumor.

Phase II trial and pharmacokinetic assessment of intravenous melphalan in patients with advanced prostate cancer

Alkylating agents have been reported to yield response rates of up to 20% in hormone-refractory prostate cancer. Melphalan was studied in four small trials in which the drug was given orally. In this phase II trial, melphalan (30 mg/m2) was given intravenously every 28 days to 27 patients with hormone-refractory prostate cancer. Pharmacokinetic sampling was performed so as to describe the clearance of melphalan in this population and in an attempt to carry out pharmacodynamic modeling for toxicity and response. Prostate-specific antigen (PSA) was also assessed prospectively. No objective responses to this regimen were documented. The median survival for patients on this trial was 11.5 months. There was no correlation between drug clearance and measured creatinine clearance and no relationship between systemic exposure and toxicity. A decrease of > 50% in serum PSA that was sustained for > 6 weeks was documented in two patients, most notably in one patient who has survived for more than 29 months. Intravenous melphalan is not an active agent in hormone-refractory prostate cancer.

Pharmacokinetically guided dosing for intravenous melphalan: a pilot study in patients with advanced ovarian adenocarcinoma

Pharmacokinetically guided administration of melphalan was investigated during a pilot study in patients with advanced ovarian adenocarcinoma. The schedule involved a fixed dose on day 1 (7.9 mg) followed by a second dose on day 2, calculated on the basis of pharmacokinetic data to achieve a target area under the concentration-time curve (AUC). 20 courses of intravenous melphalan were administered to 7 patients. AUC, standardised to 1 mg/m2, ranged between 4.3 and 8.9 (mg/l) min. In 12 fully evaluable courses, less than 15% deviation from the target AUC was found, showing that AUC monitoring was possible by means of the test dose. Pharmacodynamic effects showed a positive correlation with melphalan AUC. Myelosuppression appeared at 47 (mg/l) min and grade 3 or 4 haematological toxicities were observed in 4 cycles, associated with AUC values ranging between 86 and 112 (mg/l) min. Relative leucocyte decreases were well correlated with AUC values.

Interphase cell death as related to the cell cycle of melphalan-treated human myeloma cells

The effect of melphalan on cell loss, cell growth and cell-cycle traverse was studied on the human myeloma cell line RPMI 8226. Melphalan treatment resulted in arrest of cells in late S- and G2-phases in a population of unsynchronized cells. At high concentrations of melphalan (e.g. 40 microM), cell loss was noticed during the first cell cycle after melphalan treatment in addition to the aforementioned arrest of cells in late S and G2. The cell loss after melphalan treatment was further analysed in cells enriched for G1-phase. Cell death in this population of cells occurred between 24 and 48 hr after treatment as the cells were in S and moving over to G2.

Interaction between cytostatics and nutrients

Cancer patients have the highest prevalence of malnutrition of any group of hospitalized patients. The presence of the tumor alone may lead to reduced intake of different nutrients and treatment modalities such as surgery, chemotherapy and radiation therapy may further exacerbate nutritional disturbances. Dietary manipulation in experimental systems has shown improvement of tumor response to cancer therapy. Drug pharmacokinetics has been shown to be altered by changes in nutritional delivery. This article reviews the present knowledge, from experimental and clinical standpoints, of the potential role of different nutritional factors on the specific cancer treatment. It is obvious that alteration of at least some dietary factors affect the outcome of different forms of cancer treatment. Indeed, although interest in the clinical significance of optimal dietary intake and supplementation during cancer therapy so far remain marginal, accumulating data indicate that this area deserves further research attention.

Kinetics of melphalan leakage during hyperthermic isolation perfusion in melanoma of the limb

The kinetics of melphalan leakage into the peripheral blood were studied in 21 patients undergoing hyperthermic isolation perfusion of the upper or lower limb as an adjuvant treatment in high-risk melanoma; in 5 patients cisplatin was added. The melphalan concentrations in the peripheral blood rose predominantly during the first 20 min of perfusion and levelled out to an apparent steady state of about 0.28 micrograms/ml in upper extremity perfusions, and 0.34 (without cisplatin) and 0.37 micrograms/ml (with cisplatin) in lower extremity perfusion. Erythrocytes labelled with technetium Tc 99m, which were added concomitantly with melphalan to the perfusion medium, appeared in the systemic circulation of the patients at an almost constant rate of 0.32% (lower and upper limb perfusions without cisplatin and 0.37% (with cisplatin) of total tracer/min. This perfusate flow rate indicated by labelled erythrocytes completely explained the leakage of melphalan from the perfusion circuit into the peripheral blood. Peak concentrations of melphalan in the peripheral blood were observed immediately after reconstitution of normal hemodynamic conditions once isolation perfusion had been terminated. This fraction of melphalan might originate from tissue-binding sites, but also from vascular compartments; therefore, a thorough washing-out procedure might minimize this effect.

Oral melphalan pharmacokinetics--relation to dose in patients with multiple myeloma

The pharmacokinetics of melphalan have been studied after oral doses of 5, 10 and 20 mg, and 10 mg i.v. Seven patients with multiple myeloma received the drug on 4 consecutive days and the concentration of melphalan was determined by liquid chromatography. Melphalan was rapidly absorbed after p.o. administration. Absorption lag-time was less than 1 h. The median time for attaining the peak concentration was 1.12 h (97% confidence interval: 0.68-1.55), 1.21 h (0.85-1.43) and 1.08 h (0.84-1.29) after doses of 5, 10 and 20 mg. The bioavailability showed large interindividual variations, and was not significantly affected by the dose given. There was a significant decrease in bioavailability during the treatment course (P less than 0.05). Absorption of melphalan obeys first-order kinetics in the dose interval studied. The results indicate that it might be of benefit to administrate oral melphalan for fewer days than the usually used 4 day regimen, in an attempt to achieve a higher bioavailability.

Degradation of melphalan in vitro: rationale for the use of continuous exposure in chemosensitivity assays

The hydrolysis of melphalan in cell culture medium at 37 degrees C has been studied. Degradation of melphalan proceeded via monohydroxy-melphalan (MOH) to dihydroxymelphalan [M(OH)2] with a half-life of 66 min for melphalan and 58 min for MOH. The half-life for melphalan was similar to the terminal half-life of the drug in vivo. The effect of the two metabolites, MOH and M(OH)2, on the chemosensitivity of K562 leukaemia cells during continuous exposure to melphalan was also examined. M(OH)2 had no potentiating effect on melphalan cytotoxicity at concentrations up to 100 micrograms/ml. MOH also had little effect on cell kill at concentrations higher than those commonly achieved during in vitro chemosensitivity assays. The LD50 for 1 h exposure to melphalan was twice that for continuous exposure: this also suggests no interference by MOH and M(OH)2. These data suggest that continuous exposure of melphalan in in vitro chemosensitivity assays is probably preferable to the arbitrary 1 h drug exposure time commonly employed.

Comparative brain and plasma pharmacokinetics and anticancer activities of chlorambucil and melphalan in the rat

Equimolar doses of chlorambucil and melphalan (both 10 mg/kg) were administered i.v. to anesthetized rats, and the plasma and brain concentrations of chlorambucil, its metabolites 3,4-dehydrochlorambucil and phenylacetic mustard, and melphalan were determined by high-performance liquid chromatography from 5 to 240 min thereafter. Chlorambucil demonstrated a monophasic disappearance from plasma, with a half-life of 26 min. The compound was 99.6% plasma-protein-bound. Chlorambucil underwent beta-oxidation to yield detectable concentrations of 3,4-dehydrochlorambucil and substantial amounts of phenylacetic mustard in the plasma. Low concentrations of chlorambucil and phenylacetic mustard were detected in the brain. Calculated from the areas under the concentration-time curves, the brain:plasma concentration integral ratios of chlorambucil and phenylacetic mustard were 0.021 and 0.013, respectively. Melphalan demonstrated a biphasic disappearance from plasma, with half-lives of 1.9 and 78 min. The compound was approximately 86% plasma protein-bound. Low concentrations of melphalan were detected in the brain, and its brain:plasma ratio was 0.13. These data demonstrate that following the administration of chlorambucil and melphalan, only low concentrations of active drug are able to enter the brain. As a consequence, concentrations of both drugs that cause the complete inhibition of extracerebrally located tumor have no effect on those located within the brain. Further, the brain uptake of melphalan, although low, is greater than that of chlorambucil and its active metabolites, which coincides with its slightly greater intracerebral activity following the systemic administration of very high doses.

The pharmacokinetics of melphalan during intermittent therapy of multiple myeloma

During intermittent melphalan-prednisone therapy the area under the plasma concentration-time curve of melphalan increased by an average of 45% after oral or intravenous administration of the drug in myeloma patients during the initial three courses at six-week intervals. The rise in melphalan plasma concentrations could not be referred to an alteration in melphalan elimination, metabolism, erythrocyte/plasma partition ratio, or protein binding. A possible explanation could be that covalent binding sites of melphalan were successively saturated during intermittent treatment, resulting in higher drug concentrations during successive courses of therapy.

Therapeutic concentrations of melphalan do not affect yeast cell phagocytosis by monocytes

The effect of melphalan on monocyte phagocytosis was assessed by studying the uptake of fluorescent yeast cells by glass-adherent monocytes (a fluorescence-quenching technique). In contrast to several other cytotoxic agents, melphalan did not inhibit monocyte phagocytosis. Although the main immunosuppressive side effect of most cytotoxic drugs appears to be due to bone marrow depression with reduction of leukocyte counts, it is reasonable to assume that lack of interference with the function of mature leukocytes is a favourable feature of an antineoplastic drug.

Melphalan concentration dependent plasma protein binding in healthy humans and rats

The binding of melphalan to plasma proteins from four healthy humans and from rats was measured by centrifugal ultrafiltration. Melphalan concentrations were determined by HPLC and by measuring 14C-melphalan activity. In whole blood, melphalan was distributed preferentially in plasma. However, a constant fraction, 37%, which was independent of the total melphalan concentration in whole blood, was present within the red blood cells. The binding of melphalan to plasma proteins from humans was less than that from rats. In both, however, the fraction bound was constant throughout the concentration range (0.1 to 9.0 microM) that is achieved during standard-dose melphalan therapy. Albumin was the primary binding protein. At concentrations equal to or in excess of 33 microM, which have been achieved during high-dose melphalan therapy, free plasma melphalan concentrations were no longer linearly related to total drug concentrations, and the plasma protein binding of melphalan in the human became concentration dependent. This occurred at concentrations of 70 microM in the rat. Scatchard analysis of the data indicated the presence of 2 groups of binding sites. Class I sites had 0.03 and 0.4 binding sites per albumin molecule in humans and rats, with respective association constants of 4.43 X 10(4) M-1 and 1.92 X 10(4) M-1. Class II sites had 5.18 and 2.60 binding sites per molecule, with respective association constants of 3.82 X 10(2) M-1 and 2.01 X 10(2) M-1.

Renal function in the elimination of oral melphalan in patients with multiple myeloma

Pharmacokinetic studies in 11 patients with multiple myeloma were undertaken on the first and last days of one course of chemotherapy. The drug was administered PO in single doses of 6-14 mg daily. Melphalan concentrations were determined by high-performance liquid chromatography. The interpatient variability of pharmacokinetic parameters noted by other authors was observed. Regression analysis showed a significant positive correlation between the elimination rate constant for melphalan and renal function (P = 0.003). The form of the line which describes the overall elimination rate constant for melphalan is given by the equation: Kel = 5.67 X 10(-3) + [4.90 X 10(-5) X GFR]. There was also a significant negative correlation between renal function and the area under the plasma melphalan concentration/time curve (P = 0.006). In vitro stability studies of melphalan in plasma at 37 degrees C and pharmacokinetic data suggest that hydrolysis and renal clearance are the major mechanisms of melphalan elimination. This work shows quantitatively the relationship between renal function and drug elimination and how the data may be used in predicting melphalan half-life from creatinine clearance.

Studies on the mechanism of gastrointestinal absorption of melphalan and chlorambucil

The uptake of melphalan into tumour cells has been shown previously to involve active transport, while that of chlorambucil is by passive diffusion. In view of these findings, the mechanism of their gastrointestinal absorption was investigated using the in situ rat intestinal model. Segment lengths in all cases were (mean +/- SD) 47.2 +/- 4.7 cm. Drug absorption was monitored from control intestinal segments and from segments pretreated with the metabolic inhibitors 2,4 dinitrophenol (DNP) or carbonylcyanide-M-chlorophenyl-hydrazone (CCCP). Aliquots of gut-perfusing solution were removed at 5-min intervals over 30 min and assayed for drug using a high-performance liquid chromatography (HPLC) method selective for the alkylating agents. Absorption of melphalan by control animals was (mean +/- SD) 1.22% +/- 0.25% cm-1 gut length, as against 0.59% +/- 0.13% cm-1 in DNP- and 0.45% +/- 0.07% cm-1 in CCCP-treated animals. Absorption of chlorambucil was 1.47% +/- 0.17% cm-1 (control), 1.49% +/- 0.06 cm-1 (DNP), and 1.58% +/- 0.23% cm-1 (CCCP). It was clear, therefore, that pretreatment of intestinal segments with metabolic inhibitors led to a reduced absorption of melphalan (P less than 0.01) but did not influence that of chlorambucil. The experimental data suggest that melphalan uptake from the intestine involves an energy-dependent system whereas chlorambucil is passively absorbed.

Stability of melphalan solutions during preparation and storage

A stability-indicating high-performance liquid chromatographic assay has been used to investigate the stability of solutions of melphalan under conditions that pertain to setting up in vitro chemosensitivity assays. Melphalan (1 and 20 micrograms/mL) was found to be 30% more stable in 150 mM NaCl solution (normal saline) than in Dulbecco's phosphate-buffered saline. The drug stored at 20 micrograms/mL in normal saline at room temperature (21.5 degrees C) lost 5% of its activity (t0.95) in 1.5 h; at 5 degrees C the t0.95 was 20 h. From an Arrhenius plot of the results, the activation energy of the hydrolysis reaction in normal saline was 100.2 kJ/mol. Less than 5% of drug activity was lost when solutions of melphalan were (a) stored at -20 degrees C and -35 degrees C for 7 months, (b) frozen and thawed up to four times, or (c) filtered through various membranes. Drug degradation was not affected by storage-container material. The half-life of melphalan in a Roswell Park Memorial Institute medium containing 10% fetal bovine serum at 37 degrees C was 1.13 +/- 0.10 h; the presence of 0.3% agar had no effect. It is suggested that melphalan be handled at temperatures greater than 5 degrees C for a minimum of time, but solutions of the drug can be stored for at least 6 and possibly up to 12 months at -20 degrees C without significant deterioration taking place.

Pharmacokinetics of high dose melphalan

A pharmacokinetic study of high dose intravenous melphalan, 180 mg/m2, was performed in eight patients. Plasma levels of melphalan declined in a biexponential fashion with a mean terminal half-life (t 1/2 beta) of 61 min (range 40.3-132.8 min). Estimated peak concentrations ranged from 5.45 to 16.57 mcg/ml. The average volume of distribution at steady state (Vdss) and clearance were 0.479 +/- 0.164 l/kg and 6.73 +/- 1.60 ml/min/kg, respectively. These kinetic parameters are similar to those reported from studies using lower doses of melphalan.