Conjugation with L-Glutamate for in vivo brain drug delivery

In vitro studies have shown that conjugation of a model compound [p-di(hydroxyethyl)-amino-D-phenylalanine (D-MOD)] with L-Glu can improve D-MOD permeation through the bovine brain microvessel endothelial cell monolayers (Sakaeda et al., 2000). The transport of this D-MOD-L-Glu conjugate is facilitated by the L-Glu transport system. In this paper, we evaluate the in vivo brain delivery of model compounds (i.e. D-MOD, p-nitro-D-phenylalanine (p-nitro-D-Phe), 5,7-dichlorokynurenic acid (DCKA) and D-kyotorphin) and their L-Glu conjugates. DCKA was also conjugated with L-Asp and L-Gln amino acids. The analgesic activities of D-kyotorphin and its L-Glu conjugate were also evaluated. The results showed that the brain-to-plasma concentration ratio of D-MOD-L-Glu was higher than the D-MOD alone; however, the plasma concentration of both compounds were the same. The plasma concentration of p-nitro-D-Phe-L-Glu conjugate was higher than the parent p-nitro-D-Phe; however, the brain-to-plasma concentration ratio of p-nitro-D-Phe was higher than its conjugate. On the other hand, both DCKA and DCKA conjugates have a low brain-to-plasma concentration ratio due to their inability to cross the blood-brain barrier (BBB). The L-Asp and L-Glu conjugates of DCKA have elevated plasma concentrations relative to DCKA; however, the DCKA-L-Gln conjugate has the same plasma concentration as DCKA. For D-kyotorphin, both the parent and the L-Glu conjugate showed similar analgesic activity. In conclusion, conjugation of a non-permeable drug with L-Glu may improve the drug's brain delivery; however, this improvement may depend on the physicochemical and receptor binding properties of the conjugate.

Melphalan monitoring during hyperthermic perfusion of isolated limb for melanoma: pharmacokinetic study and 99mTc-albumin microcolloid technique

BACKGROUND

The kinetics of melphalan leakage from extracorporeal fluid to the peripheral blood was studied in ten patients undergoing hyperthermic isolation perfusion of the lower limbs as an adjuvant treatment in high-risk melanoma.

MATERIALS AND METHODS

Systemic leakage was monitored by a new technique using 99mTc-albumin microcolloid. Serial samples were drawn from a peripheral vein and from the perfusion circuit during surgical treatment and analysed by HPLC.

RESULTS

The leakage measured with 99mTc-albumin microcolloid ranged from 1.5 to 18%/h (mean 8%/h). The average concentrations in the perfusate were 200-300-fold those found in the systemic circulation. A good correlation (R=0.945) was obtained between systemic AUC (0 to 1 hour) and leakage measured through the 99mTc procedure. Negligible toxicity was found and the survival rate yielded 92% of objective response.

CONCLUSION

By studying the pharmacokinetic data of melphalan in the circuit and in the systemic circulation, we were able to validate the 99mTc procedure used during clinical perfusion. Moreover, considering the efficiency of the system as well as the minimum toxicity and the high survival rate, a reduction of perfusion time may be considered.

[Chemobiokinetics of sarcolysin and its peptides with glutaminic acid]

A 14C study of chemobiokinetics of sarcolysin and its peptides of glutaminic acid, dosage and routes of administration was conducted in intact rats and those bearing Walker's carcinoma. Similar in shape for peptides, kinetic curves differed from those found for sarcolysin. The rates of absorption and excretion of sarcolysin peptides in intraperitoneal and, particularly, oral administration were lower than those of sarcolysin. Tumor appeared to play a role in a higher rate of peptide excretion. While sarcolysin and its peptides distribution in organs and tissues was generally identical, time of peak radioactive concentration build-up was different. Time needed for accumulation and excretion of peptides from tumor was much longer than from other organs or tissues. Sarcolysin went chiefly to urine while peptides--to faeces.

A bioreversible prodrug approach designed to shift mechanism of brain uptake for amino-acid-containing anticancer agents

By derivatization at the N-terminus of amino acid-based anticancer agents (e.g. melphalan and acivicin) to form a drug delivery system (TDDS), we demonstrate a change in the mechanism of brain uptake from the large neutral amino acid transporter (LAT) pathway to passive. An in situ rat brain perfusion technique was used to determine the brain capillary permeability-surface area (PA) product for [(14)C]L-Leu as control (5.18 +/- 0.32 x 10(-2) mL/s/g), which was inhibited competitively (to 7-18% of control) by an excess concentration of the amino-acid-containing anticancer agents, acivicin and melphalan. However, TDDS did not compete for LAT-mediated brain uptake of the radiotracer [(14)C]L-Leu. Brain uptake of TDDS was determined after in situ brain perfusion followed by RP-HPLC along with LC-MS/MS detection of the analytes in brain samples. The PA product for CH(3)-TDDS containing melphalan (5.09 +/- 2.0 x 10(-2) mL/s/g) shows that these agents rapidly cross the blood-brain barrier. Furthermore, competition studies of CH(3)-TDDS with [(3)H]verapamil suggest that the TDDS interacts significantly with the multidrug resistant efflux system (P-glycoprotein) at the blood-brain barrier. Therefore, TDDS were shown to lack LAT-mediated brain uptake. The drug delivery systems, however, showed uptake predominantly via the passive route along with recognition by the multidrug resistant efflux protein at the cerebrovasculature.

High-dose thiotepa and melphalan with hemopoietic progenitor support following induction therapy with epirubicin-paclitaxel-containing regimens in metastatic breast cancer (MBC)

BACKGROUND

Preliminary data from phase III randomized studies have failed to show benefit of HDC given as consolidation after anthracycline and alkylating-based chemotherapy in metastatic breast cancer (MBC). Moderate activity of induction regimens and selection of chemoresistant clones are among the possible reasons for these disappointing results. We therefore have designed a phase II study where high-dose alkylating agents are given as consolidation after an induction treatment including the most active agents (epirubicin and paclitaxel) without alkylating agents.

PATIENTS AND METHODS

Patients with MBC not previously treated with chemotherapy for metastatic disease were eligible. After six courses of epirubicin-paclitaxel +/- gemcitabine patients received a course of thiotepa 600 mg/m2 + melphalan 160 mg/m2 with hemopoietic support. Pharmacokinetic parameters of thiotepa and melphalan were measured and related to treatment outcomes. The L-VEF of the patients was monitored before and after treatment.

RESULTS

Forty-eight patients have been treated. Before HDC 14 patients were in CR, and 34 in PR. A median of 6.92 x 10(6) (range 1.53-16.6) CD34+ cells/kg were reinfused after HDC. Median days (range) to neutrophils > 0.5 x 10(9)/l and platelets > 20,000 x 10(9)/l were 9.5 (9-33) and 10 days (9-32), respectively. Symptomatic CHF was observed in two patients (4.1%). Cmax and AUC of thiotepa showed a linear relationship with time to progression (TTP) and overall survival (OS): r2 = 0.6. After HDC the conversion rate from PR to CR was 44.1%. At five years progression-free and overall survival rates are 37.5% and 65%, respectively. A treatment-related death was observed.

CONCLUSIONS

High-dose thiotepa and melphalan after an epirubicin-paclitaxel-containing treatment is feasible, devoid of significant cardiotoxicity and very active. Pharmacokinetic parameters of high-dose thiotepa might be linked to treatment outcome.

Identification of the interferon-inducible double-stranded RNA-dependent protein kinase as a regulator of cellular response to bulky adducts

The double-stranded RNA-dependent protein kinase PKR plays a central role in IFN-mediated antiviral response. The ability of PKR mutants to transform rodent fibroblasts led to the hypothesis that PKR acts as a tumor suppressor. Recent studies have identified an expanding network of PKR signaling partners, including signal transducers and activators of transcription 1 (STAT1), p53, and IkappaB-kinase. Here we demonstrate that PKR is involved in the cellular response to genotoxic stress. PKR-deficient mouse-embryonic fibroblasts (PKR-/-) are hypersensitive to bulky adduct DNA damage caused by cisplatin, melphalan, and UV radiation but not to other DNA-damaging agents such as Adriamycin. PKR-deficient cells are highly susceptible to cisplatin-induced apoptosis. They demonstrate retarded cisplatin adduct removal kinetics. Most strikingly, PKR localizes to the nucleus rapidly upon cisplatin treatment. Restoration of PKR in PKR-/- cells results in resistance to cisplatin and enhanced cell capacity to remove cisplatin DNA adducts. We conclude that PKR has a function in the regulation of cellular response to bulky adduct-inducing agents, possibly by modulating DNA repair mechanisms.

Enhancement of transport of D-melphalan analogue by conjugation with L-glutamate across bovine brain microvessel endothelial cell monolayers

In this paper, the L-glutamate (L-Glu) transport system was targeted to improve the delivery of a model compound, p-di(hydroxyethyl)-amino-D-phenylalanine (D-MOD), through the blood-brain barrier (BBB) in vitro cell culture model. D-MOD is an analogue of an antitumor agent D-melphalan. To target the L-Glu transport system, D-MOD was conjugated to L-Glu to give D-MOD-L-Glu conjugate. D-MOD and D-MOD-L-Glu transport properties were evaluated using the bovine brain microvessel endothelial cell (BBMEC) monolayers. The results suggest that D-MOD-L-Glu conjugate permeates through the BBMEC monolayers more readily than the parent D-MOD. The improvement of transport may be due to the recognition of D-MOD-L-Glu by the L-Glu transport system. The transport mechanism was evaluated using several different experiments including: (a) concentration-dependent studies; (b) temperature-dependent studies; (c) substrate inhibition studies; and (d) metabolic inhibitor studies. The D-MOD-L-Glu transport was inhibited by the change of temperature from 37 degrees C to 4 degrees C. At higher concentrations, the transport of D-MOD-L-Glu reached plateau due to saturation. Furthermore, some amino acids (i.e., L-Glu, L-Asp, D-Asp, and L-Gln) inhibited the transport of D-MOD-L-Glu; presumably the conjugate was competing with these amino acids for the same transport system. Metabolic inhibitors (i.e., 2,4-dinitrophenol and sodium azide) suppressed the transport of the conjugate. However, the conjugate was not transported by monocarboxylic acid, dipeptide and neutral amino acid transporters. In conclusion, the L-Glu transport system can be utilized to facilitate a non-permeable drug across the BBB by conjugating the drug with L-Glu amino acid.

Alkylator resistance in human B lymphoid cell lines: (1). Melphalan accumulation, cytotoxicity, interstrand-DNA-crosslinks, cell cycle analysis, and glutathione content in the melphalan-sensitive B-lymphocytic cell line (WIL2) and in the melphalan-resistant B-CLL cell line (WSU-CLL)

Two human B lymphoid cell lines WIL2 (melphalan sensitive. ***IC50:8.57 +/- 1.08 mM) and WSU-CLL (melphalan resistant, ***IC50:223.18 +/- 6.45 mM) were used as models to study alkylator resistance in human lymphoid cells. Melphalan transport studies demonstrated decreased initial melphalan accumulation in WSU-CLL cells as compared to WIL2 cells. Lineweaver-Burk plots of the rate of initial melphalan uptake showed an approximately 3.5-fold decrease of Vmax in WSU-CLL cells as compared to WIL2 cells. Melphalan transport was inhibited by 2-amino-bicyclo[2,2,1] heptane-2-carboxylic acid(BCH) in both cell lines, indicating that the amino acid transport (System L, which is sodium independent and inhibited by BCH) is functional in these two cell lines. Only a minor degree of inhibition of melphalan transport was noted after sodium depletion (System ASC, which is sodium dependent and unaffected by BCH). Interstrand-DNA-cross-link formation showed a highly significant correlation with in-vitro cytotoxicity in both two cell lines. However, the melphalan concentration at which such interstrand DNA cross-linking occurred differed significantly when WIL2 cells and WSU-CLL cells were compared. The kinetics of interstrand-DNA-cross-link formation and removal following treatment with melphalan also differed significantly, with WSU-CLL cells, showing a much more rapid rate of removal of interstand DNA cross-links as compared to WIL2 cells. Cell cycle analysis showed that melphalan treatment resulted in the progressive arrest of the WSU cells in G1 and G2 phases. But WIL2 cells failed to enter G1 or G2 arrest after melphalan treatment, suggesting an increased rate of DNA repair occurring in melphalan-resistant WSU-CLL cells. There was no significant difference between the two cell lines in regard to either glutathione content or glutathione-S transferase activity. These findings indicate that multiple factors are associated with alkylator resistance in lymphoid cells including alteration of uptake, DNA repair and cell cycle progression. However no evidence for alteration in glutathione content and glutathione-S-transferase activity was found.

[Chemotherapy by isolated liver perfusion with endovascular occlusion catheter: preliminary experience in pigs]

Very high concentrations of cytotoxic drug may be obtained with chemotherapy performed with vascular exclusion.

OBJECTIVE

To study the pharmacokinetics and toxicity of melphalan during in situ isolated liver perfusion, and to test an endovascular occlusion catheter.

METHODS

Isolated liver perfusion with melphalan (15 mg bolus) was performed in 6 pigs (50-60 kg) for 30 min, with non-oxygenated Ringer's solution. Hepatic outflow, collected by a double balloon catheter inserted into the retrohepatic inferior vena cava, was pumped into the gastroduodenal artery, while the common hepatic artery and portal vein were clamped.

RESULTS

A maximum concentration of 30,000 ng/mL was obtained in the circuit before an exponential decrease, while the concentration in systemic blood was less than 500 ng/mL (n = 3). Before closing the abdomen, melphalan concentrations were about 2,000 ng/mg in the liver, and undetectable in the muscle. Postoperative course (2 weeks, n = 2) was uneventful with minor alterations in blood tests and hepatic histology.

CONCLUSION

This method of local chemotherapy with melphalan appears to be safe with minor leakage and minimal toxicity.

Increased local cytostatic drug exposure by isolated hepatic perfusion: a phase I clinical and pharmacologic evaluation of treatment with high dose melphalan in patients with colorectal cancer confined to the liver

A phase I dose-escalation study was performed to determine whether isolated hepatic perfusion (IHP) with melphalan (L-PAM) allows exposure of the liver to much higher drug concentrations than clinically achievable after systemic administration and leads to higher tumour concentrations of L-PAM. Twenty-four patients with colorectal cancer confined to the liver were treated with L-PAM dosages escalating from 0.5 to 4.0 mg kg(-1). During all IHP procedures, leakage of perfusate was monitored. Duration of IHP was aimed at 60 min, but was shortened in eight cases as a result of leakage from the isolated circuit. From these, three patients developed WHO grade 3-4 leukopenia and two patients died due to sepsis. A reversible elevation of liver enzymes and bilirubin was seen in the majority of patients. Only one patient was treated with 4.0 mg kg(-1) L-PAM, who died 8 days after IHP as a result of multiple-organ failure. A statistically significant correlation was found between the dose of L-PAM, peak L-PAM concentrations in perfusate (R = 0.86, P< or =0.001), perfusate area under the concentration-time curve (AUC; R = 0.82, P<0.001), tumour tissue concentrations of L-PAM (R = 0.83, P = 0.011) and patient survival (R = 0.52, P = 0.02). The peak L-PAM concentration and AUC of L-PAM in perfusate at dose level 3.0 mg kg(-1) (n = 5) were respectively 35- and 13-fold higher than in the systemic circulation, and respectively 30- and 5-fold higher than reported for high dose oral L-PAM (80-157 mg m(-2)) and autologous bone marrow transplantation. Median survival after IHP (n = 21) was 19 months and the overall response rate was 29% (17 assessable patients; one complete and four partial remissions). Thus, the maximally tolerated dose of L-PAM delivered via IHP is approximately 3.0 mg kg(-1), leading to high L-PAM concentrations at the target side. Because of the complexity of this treatment modality, IHP has at present no place in routine clinical practice.

Tumour necrosis factor alpha increases melphalan concentration in tumour tissue after isolated limb perfusion

Several possible mechanisms for the synergistic anti-tumour effects between tumour necrosis factor alpha (TNF-alpha) and melphalan after isolated limb perfusion (ILP) have been presented. We found a significant sixfold increase in melphalan tumour tissue concentration after ILP when TNF-alpha was added to the perfusate, which provides a straightforward explanation for the observed synergism between melphalan and TNF-alpha in ILP.

Can tissue drug concentrations be monitored by microdialysis during or after isolated limb perfusion for melanoma treatment?

Isolated limb perfusion (ILP) with melphalan is used to treat recurrent melanoma. This study aimed to develop a microdialysis technique for melphalan tissue concentration measurement during ILP. The effects of melphalan concentration (50-600 microg/ml), microdIalysis flow rate (0.55-17.5 microl/min), probe length (5-50 mm) and temperature (25-41.5 degrees C) on in vitro recovery were studied. In addition, in vivo recovery was measured in rat hindlimbs perfused with melphalan using 50 mm microdialysis probes implanted subcutaneously and into muscle. Both dialysate and tissue sample melphalan concentrations were determined by high performance liquid chromatography. The in vitro recovery of melphalan was not affected by melphalan concentration or temperature, but increased with probe length and decreased with flow rate. The melphalan concentrations in subcutaneous and muscle dialysates were not significantly different. A linear relationship was found between tissue dialysate concentrations and actual tissue concentrations of melphalan (r2 = 0.97). Microdialysis is a potential method for tissue drug monitoring which may assist in the efficacious use of cytotoxics in human ILP.

A phase I and pharmacokinetic study of melphalan using a 24-hour continuous infusion in patients with advanced malignancies

The objectives of the present study were to determine the following: (a) the maximum tolerated dose (MTD) of melphalan using a 24-h continuous infusion; (b) the clinical toxicity; and (c) the pharmacokinetic characteristics of melphalan at each dose level. Twenty-one patients with refractory solid tumors were enrolled in the study. Melphalan, packaged in 3% sodium chloride, was administered i.v. over a 24-h period. Patients were assigned to one of three escalating dose levels of melphalan: (a) 20 mg/m2 (n = 5); (b) 30 mg/m2 (n = 7); and (c) 40 mg/m2 (n = 6). Each patient underwent pharmacokinetic evaluation during the first cycle of treatment. Melphalan concentrations in plasma were determined by high-performance liquid chromatography. Toxicity was evaluated after each course of chemotherapy. All of the patients were assessable for toxicity and pharmacokinetics, and 20 patients were assessable for response analysis. A total of 50 courses of melphalan was studied. The MTD was 30 mg/m2. The dose-limiting toxicity was neutropenia and thrombocytopenia. Hematotoxicity was reversible (nadir, 14-15 days; recovery, 3.5 and 12.5 days for 30 and 40 mg/m2, respectively), cumulative, and related to the administered dose and to the history of previous therapy. There were six episodes of neutropenic sepsis. Individual pharmacokinetic parameters were estimated using a Bayesian approach and linear elimination kinetics. Data were compatible with a one-compartment model. Relationships have been found between the area under the plasma concentration-time curve and doses and between Css and doses. Moreover, clearance, t1/2 elimination, and volume of distribution did not change statistically with dose, which suggests linear kinetics. Two partial responses were observed in patients with ovarian carcinoma or adenocarcinoma of unknown primary origin, and another patient had stabilization disease. In conclusion, melphalan MTD was determined to be 30 mg/m2 when administered as a 24-h infusion. Hematological toxicity was the dose-limiting toxicity. The most important nonhematological toxicity encountered was nausea and vomiting. The recommended dose for Phase II studies was 30 mg/m2.

[Intratumoral chemotherapy in an experimental animal model: another therapeutic possibility in cancerology]

OBJECTIVE

Assess the efficacy of intratumoral chemotherapy in a colonic tumor model implanted subcutaneously in the BD IX rat.

METHOD

In order to determine their antitumoral effect, 5 anticancer drugs were administered via intravenous and direct intratumoral routes 2 or 10 days after subcutaneous inoculation of tumoral cells. Intratumoral diffusion was evaluated using Patent blue injected directly into the tumoral tissue. Cisplatinum was administered via intratumoral, intravenous and intra-arterial routes to determine the intratumoral and intrarenal concentrations achieved with each of these administration routes. Cisplatinum was also administered via intravenous and intratumoral infusion for 30 minutes to determine the antitumoral effect of each of these routes.

RESULTS

Mitomycin and cisplatinum inhibited growth of tumors which had not yet become established and caused advanced stage tumors to regress. For early stage tumors, the intratumoral route was always more effective than the intravenous route. Patent blue diffusion demonstrated a nonhomogeneous intratumoral distribution. Compared with intravenous or intra-arterial infusion, intratumoral infusion gave much higher concentrations of cisplatinum within the tumors and reduced systemic diffusion. At 7 weeks, the antitumoral effect was equivalent for the 2 administration routes while at 13 weeks, the intratumoral treatment was more effective than the intravenous treatment.

CONCLUSION

These findings in an experimental animal model demonstrate that intratumoral chemotherapy is more effective than intravenous chemotherapy. It is however still impossible to consistently cure tumors induced in animals.

Pharmacokinetics of melphalan in isolated limb perfusion

The pharmacokinetics of melphalan was studied by sampling of tissue and plasma in 72 rats that underwent isolated hyperthermic limb perfusion under different conditions. A miniaturized extracorporeal circulation system for small animals was used for perfusion of the rat hindlimb. Melphalan levels (L-phenylalanine mustard, L-PAM) were determined by high-performance liquid chromatography (HPLC). The temperature of the perfusate plasma and tissue, pH, administration method, and flow rate were modified and compared with regard to their influence on pharmacokinetic parameters. The highest tissue penetration of melphalan was observed under the following conditions: (a) pH range of the perfusate plasma between 7.3 and 7.7 (physiological environment), (b) temperature range of the perfusate from 40 degrees to 41.5 degrees C (destruction of cellular carrier systems at higher temperatures and increased inactivation by hydrolysis of melphalan above 41.5 degrees C), (c) application of melphalan as a single dose into the reservoir of the extracorporeal circuit (optimal tissue penetration), and (d) reduced perfusate flow (prolonged contact time between perfusate and tissue).

Isolated hypoxic hepatic perfusion with tumor necrosis factor-alpha, melphalan, and mitomycin C using balloon catheter techniques: a pharmacokinetic study in pigs

OBJECTIVE

To validate the methodology of isolated hypoxic hepatic perfusion (IHHP) using balloon catheter techniques and to gain insight into the distribution of tumor necrosis factor-alpha (TNF), melphalan, and mitomycin C (MMC) through the regional and systemic blood compartments when applying these techniques.

SUMMARY BACKGROUND DATA

There is no standard treatment for unresectable liver tumors. Clinical results of isolated limb perfusion with high-dose TNF and melphalan for the treatment of melanoma and sarcoma have been promising, and attempts have been made to extrapolate this success to the isolated liver perfusion setting. The magnitude and toxicity of the surgical procedure, however, have limited clinical applicability.

METHODS

Pigs underwent IHHP with TNF, melphalan, and MMC using balloon catheters or served as controls, receiving equivalent dosages of these agents intravenously. After a 20-minute perfusion, a washout procedure was performed for 10 minutes, after which isolation was terminated. Throughout the procedure and afterward, blood samples were obtained from the hepatic and systemic blood compartments and concentrations of perfused agents were determined.

RESULTS

During perfusion, locoregional plasma drug concentrations were 20- to 40-fold higher than systemic concentrations. Compared with systemic concentrations after intravenous administration, regional concentrations during IHHP were up to 10-fold higher. Regional MMC and melphalan levels steadily declined during perfusion, indicating rapid uptake by the liver tissue; minimal systemic concentrations indicated virtually no leakage to the systemic blood compartment. During isolation, concentrations of TNF in the perfusate declined only slightly, indicating limited uptake by the liver tissue; no leakage of TNF to the systemic circulation was observed. After termination of isolation, systemic TNF levels showed only a minor transient elevation, indicating that the washout procedure at the end of the perfusions was fully effective.

CONCLUSIONS

Complete isolation of the hepatic vascular bed can be accomplished when performing IHHP using this balloon catheter technique. Thus, as in extremities, an ideal leakage-free perfusion of the liver can now be performed, and repeated, without major surgery. The effective washout allows the addition of TNF in this setting.

Hyperthermia, cyclosporine A and melphalan cytotoxicity and transport in multidrug resistant cells

The ability of hyperthermia and cyclosporine A to modulate melphalan cytotoxicity and transport processes was investigated in a pleiotropic MDR Chinese hamster ovary cell line (CH(R)C5) and in the drug-sensitive parent line (AuxB1). Cyclosporine A increased cytotoxicity of melphalan in MDR cells, but not in drug-sensitive cells. In MDR cells, hyperthermia caused marked enhancement of melphalan cytotoxicity when cyclosporine A was present. The increased melphalan cytotoxicity in MDR cells was accompanied by changes in membrane permeability to the drug. Cyclosporine A caused an increase in melphalan uptake in MDR cells and a decrease in melphalan efflux out of cells, leading to an overall increase in intracellular drug accumulation. Drug transport processes were not affected by cyclosporine A in drug-sensitive cells.

Isolated lung perfusion with melphalan and tumor necrosis factor for metastatic pulmonary adenocarcinoma

BACKGROUND

Isolated left lung perfusion with melphalan and human tumor necrosis factor-alpha for pulmonary metastatic adenocarcinoma in the WAG/Rij rat was studied.

METHODS

Survival was determined for melphalan, human tumor necrosis-alpha. Lung, pulmonary effluent, and serum melphalan were analyzed by chromatography after isolated lung perfusion or intravenous injection. On day 0, rats were injected with 2.0 x 10(6) CC531S cells intravenously. On day 7, rats underwent sham thoracotomy, received melphalan intravenously, or underwent isolated left lung perfusion with saline, melphalan, tumor necrosis factor, and a combination of the latter two. On day 14, tumor nodules were counted.

RESULTS

For the doses of 400 microg tumor necrosis factor, 1,000 microg tumor necrosis factor, or both melphalan and tumor necrosis factor (2 mg + 200 microg), survival rates after contralateral pneumonectomy were 33%, 17%, and 80%, respectively. Survival in all other groups was 100%. Left lung melphalan level was significantly higher after isolated lung perfusion compared to intravenous administration. Significantly fewer left lung nodules were found for 0.5 mg isolated lung perfusion with melphalan (28+/-17) compared to isolated administration (200+/-0) (p = 0.001), and for 1.0 mg intravenous lung perfusion with melphalan (16+/-10) compared to controls (171+/-65) (p = 0.00047). Tumor necrosis factor showed no significant effect.

CONCLUSIONS

Isolated lung perfusion with melphalan is an effective treatment for pulmonary metastases from adenocarcinoma in the rat.

Cytotoxic and antitumor activity of MEN 10710, a novel alkylating derivative of distamycin

MEN 10710 is a new synthetic distamycin derivative possessing four pyrrole rings and a bis-(2-chloroethyl)aminophenyl moiety linked to the oligopyrrole backbone by a flexible butanamido chain. Its biological properties have been investigated in comparison with the structurally related compound, tallimustine (FCE24517), and the classical alkylating agent, melphalan (L-PAM). Cytotoxic potency of MEN 10710 was increased from 10- to 100-fold, as compared to tallimustine or L-PAM in murine L1210, human LoVo and MCF7 tumor cell lines. MEN 10710 was still active against L1210/L-PAM leukemic cells, while a partial cross-resistance was observed in LoVo/DX and in MCF7/DX cells selected for resistance to doxorubicin and expressing a MDR phenotype. Treatment with verapamil (VRP) reduced the resistance to tallimustine, but not to MEN 10710, in MCF7/DX cells. The cytotoxic effects reflect in vivo antitumor potency and toxicity in the treatment of human tumor xenografts. MEN 10710 was more effective in A2780/DDP, an ovarian carcinoma selected for resistance to cisplatin. On the other hand, the IC30 for inhibiting murine granulocyte/macrophage colony formation was 50 times higher for MEN 10710 than for tallimustine, suggesting a lower myelotoxic potential. In conclusion, the particular biological profile of MEN 10710 characterized by a marked cytotoxic potency, an interesting antitumor efficacy and a reduced in vitro myelosuppressive action may represent a further improvement in the rational design of a novel distamycin-related alkylating compound.

Tissue and perfusate pharmacokinetics of melphalan in isolated perfused rat hindlimb

Melphalan is commonly used as a cytotoxic agent in isolated limb perfusion for locally recurrent malignant melanoma. The time course of melphalan concentrations in perfusate and tissues during a 60-min melphalan perfusion and 30-min drug-free washout in the single-pass perfused rat hindlimb was examined using a physiologically based pharmacokinetic model. The rat hindlimbs were perfused with Krebs-Heinseleit buffer containing 4.7% bovine serum albumin (BSA) or 2.8% dextran 40 at a constant rate of 3.8 ml/min. The concentration of melphalan in perfusate and tissues was determined by high-performance liquid chromatography. The tissue concentrations of melphalan were significantly higher with the perfusate containing dextran than BSA during the 60-min perfusion. During the washout period, the melphalan concentration in the perfusates decreased rapidly in first few minutes, followed by a slower monoexponential decline. The estimated half life (t1/2) for melphalan removal from skin and fat was 59 +/- 2 min for both BSA and dextran perfusates. However, the estimated t1/2 for melphalan removal from muscle was 79 and 96 min for BSA and dextran washout perfusates, respectively. The predicted concentration-time profiles obtained for melphalan with BSA and dextran perfusates appear to correspond closely to the observed data. This study showed that the uptake of melphalan into perfused tissues is impaired by the use of perfusates in which melphalan is highly bound. Melphalan washout from muscle, but not skin and fat, was facilitated by the use of perfusates in which melphalan is highly protein bound.

Melphalan dosing regimens for management of recurrent melanoma by isolated limb perfusion: application of a physiological pharmacokinetic model based on melphalan distribution in the isolated perfused rat hindlimb

The optimal dosing schedule for melphalan therapy of recurrent malignant melanoma in isolated limb perfusions has been examined using a physiological pharmacokinetic model with data from isolated rat hindlimb perfusions (IRHP). The study included a comparison of melphalan distribution in IRHP under hyperthermia and normothermia conditions. Rat hindlimbs were perfused with Krebs-Hen-seleit buffer containing 4.7% bovine serum albumin at 37 or 41.5 degrees C at a flow rate of 4 ml/min. Concentrations of melphalan in perfusate and tissues were determined by high performance liquid chromatography with fluorescence detection. The concentration of melphalan in perfusate and tissues was linearly related to the input concentration. The rate and amount of melphalan uptake into the different tissues was higher at 41.5 degrees C than at 37 degrees C. A physiological pharmacokinetic model was validated from the tissue and perfusate time course of melphalan after melphalan perfusion. Application of the model involved the amount of melphalan exposure in the muscle, skin and fat in a recirculation system was related to the method of melphalan administration: single bolus > divided bolus > infusion. The peak concentration of melphalan in the perfusate was also related to the method of administration in the same order. Infusing the total dose of melphalan over 20 min during a 60 min perfusion optimized the exposure of tissues to melphalan whilst minimizing the peak perfusate concentration of melphalan. It is suggested that this method of melphalan administration may be preferable to other methods in terms of optimizing the efficacy of melphalan whilst minimizing the limb toxicity associated with its use in isolated limb perfusion.

The effects of perfusion conditions on melphalan distribution in the isolated perfused rat hindlimb bearing a human melanoma xenograft

An isolated rat hindlimb perfusion model carrying xenografts of the human melanoma cell line MM96 was used to study the effects of perfusion conditions on melphalan distribution. Krebs-Henseleit buffer and Hartmann's solution containing 4.7% bovine serum albumin (BSA) or 2.8% dextran 40 were used as perfusates. Melphalan concentrations in perfusate, tumour nodules and normal tissues were measured using high-performance liquid chromatography (HPLC). Increasing the perfusion flow rates (from 4 to 8 ml min(-1)) resulted in higher tissue blood flow (determined with 51Cr-labelled microspheres) and melphalan uptake by tumour and normal tissues. The distribution of melphalan within tumour nodules and normal tissues was similar for both Krebs-Henseleit buffer and Hartmann's solution; however, tissue concentrations of melphalan were significantly higher for a perfusate containing 2.8% dextran 40 than for one containing 4.7% BSA. The melphalan concentration in the tumour was one-third of that found in the skin if the perfusate contained 4.7% BSA. In conclusion, this study has shown that a high perfusion flow enhances the delivery of melphalan into implanted tumour nodules and normal tissues, and a perfusate with low melphalan binding (no albumin) is preferred for maximum uptake of drug by the tumour.

Mechanisms of enhancement of the antitumour activity of melphalan by the tumour-blood-flow inhibitor 5,6-dimethylxanthenone-4-acetic acid

Several studies show that the antitumour activity of melphalan (MEL) and other alkylating agents can be enhanced by the selective inhibition of tumour blood flow, although the mechanism(s) underlying these interactions are unclear. 5,6-Dimethylxanthenone-4-acetic acid (DMXAA), a new anticancer agent currently in phase I clinical trial, inhibits blood flow in murine tumours. DMXAA increased the activity of MEL against the MDAH-MCa-4 mouse mammary tumour maximally when MEL was given about 2 h after DMXAA, without compromising the maximal dose of the alkylating agent that could be given. The plasma pharmacokinetics of MEL were unchanged by DMXAA pretreatment, but the area under the concentration-time curve (AUC) for the tumour increased by 33% as a result of decreasing clearance (consistent with falling tumour blood flow). However, inhibition of tumour blood flow also leads to microenvironmental changes (e.g. acidosis and hypoxia) that might influence sensitivity to MEL. The sensitivity of KHT cells (freshly isolated from tumours) to MEL in vitro was increased by lowering of either pH or oxygen concentration (pO2), with an overall dose-modifying factor of 15 being recorded for aerobic cells at pH 7.4 versus hypoxic cells at pH 6.5. The cellular uptake of MEL by KHT cells was increased by 74% under hypoxia. Thus, DMXAA appears to augment the antitumour activity of MEL through two different mechanisms, increased exposure (via decreased tumour clearance of MEL) and increased sensitivity resulting from changes to the tumour microenvironment, both of which result from inhibition of tumour blood flow.

Pharmacokinetics of high-dose intravenous melphalan in patients undergoing peripheral blood hematopoietic progenitor-cell transplantation

The pharmacokinetics of melphalan following high-dose (140 mg/m2) i.v. administration were determined in 20 patients with advanced malignancies undergoing peripheral blood hematopoietic progenitor-cell transplantation. Melphalan was assayed in plasma by a specific HPLC method with UV detection. Plasma levels of melphalan declined in a biexponential fashion with a mean terminal half-life of 83 minutes (range 52-168 minutes). Estimated peak plasma concentrations ranged from 1.65 to 14.5 micrograms/ml. Plasma levels were lower than the limit of quantitation of the method used (20 ng/ml) 24 hours after drug administration. The average volume of distribution and total clearance were 317 ml/min/m2 (range 127-797 ml/min/m2) and 37.9 l/m2 (range 15.4-108 l/m2), respectively. These parameters are similar to those reported in the literature. A weak correlation was found between total clearance of melphalan and creatinine clearance (p < 0.05). No relationship between the pharmacokinetics of melphalan and myelosuppression and non-hematologic toxicities was recovered. This pharmacokinetic study indicates that on the assumption that there is no more circulating melphalan after seven elimination half-lives, it may be possible to reinfuse autologous PBPC 10-20 hours after melphalan administration.