Luigi Quintieri

A Paclitaxel-Hyaluronan Bioconjugate Targeting Ovarian Cancer Affords a Potent In vivo Therapeutic Activity

Purpose: This study was designed to evaluate the pharmacologic and biological properties of a paclitaxel-hyaluronan bioconjugate (ONCOFID-P) against IGROV-1 and OVCAR-3 human ovarian cancer xenografts following i.p. administration. Experimental Design:In vitro tumor sensitivity to ONCOFID-P was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, whereas bioconjugate interaction with cells was studied cytofluorimetrically and by confocal microscopy. In vivo toxicity was assessed by a single-dose maximum-tolerated dose, peripheral blood cell count determination and by histologic analysis. Biodistribution of the compound was evaluated with a small animal–dedicated scintigraphy gamma camera following injection of 99mTc-labeled ONCOFID-P. Pharmacokinetic analysis was also carried out. Female severe combined immunodeficiency mice implanted with ovarian cancer cells underwent treatment with ONCOFID-P or free paclitaxel starting from day 7 or 14 after tumor injection, and survivals were compared. Results: ONCOFID-P interacted with CD44, entered cells through a receptor-mediated mechanism, and exerted a concentration-dependent inhibitory effect against tumor cell growth. After i.p. administration, the bioconjugate distributed quite uniformly within the peritoneal cavity, was well-tolerated, and was not associated with local histologic toxicity. Pharmacokinetic studies revealed that blood levels of bioconjugate-derived paclitaxel were much higher and persisted longer than those obtained with the unconjugated free drug. Intraperitoneal treatment of tumor-bearing mice with the bioconjugate revealed that ONCOFID-P exerted a relevant increase in therapeutic activity compared with free drug. Conclusions: ONCOFID-P significantly improved results obtained with conventional paclitaxel, in terms of in vivo tolerability and therapeutic efficacy; these data strongly support its development for locoregional treatment of ovarian cancer.

Glutathione Transferases as Targets for Cancer Therapy

Besides catalyzing the inactivation of various electrophile-producing anticancer agents via conjugation to the tripeptide glutathione, some cytosolic proteins belonging to the glutathione transferase (formerly glutatione-S-transferase; GST) superfamily are emerging as negative modulators of stress/drug-induced cell apoptosis through the interaction with specific signaling kinases. In addition, several data link the overexpression of some GSTs, in particular GSTP1-1, to both natural and acquired resistance to various structurally unrelated anticancer drugs. Tumor overexpression of these proteins has provided a rationale for the search of GST inhibitors and GST-activated cytotoxic prodrugs. In the present review we discuss the current structural and pharmacological knowledge of both types of GST-targeting compounds.

Formation and Antitumor Activity of PNU-159682, A Major Metabolite of Nemorubicin in Human Liver Microsomes

Purpose: Nemorubicin (3′-deamino-3′-[2″(S)-methoxy-4″-morpholinyl]doxorubicin; MMDX) is an investigational drug currently in phase II/III clinical testing in hepatocellular carcinoma. A bioactivation product of MMDX, 3′-deamino-3″,4′-anhydro-[2″(S)-methoxy-3″(R)-oxy-4″-morpholinyl]doxorubicin (PNU-159682), has been recently identified in an incubate of the drug with NADPH-supplemented rat liver microsomes. The aims of this study were to obtain information about MMDX biotransformation to PNU-159682 in humans, and to explore the antitumor activity of PNU-159682. Experimental Design: Human liver microsomes (HLM) and microsomes from genetically engineered cell lines expressing individual human cytochrome P450s (CYP) were used to study MMDX biotransformation. We also examined the cytotoxicity and antitumor activity of PNU-159682 using a panel of in vitro-cultured human tumor cell lines and tumor-bearing mice, respectively. Results: HLMs converted MMDX to a major metabolite, whose retention time in liquid chromatography and ion fragmentation in tandem mass spectrometry were identical to those of synthetic PNU-159682. In a bank of HLMs from 10 donors, rates of PNU-159682 formation correlated significantly with three distinct CYP3A-mediated activities. Troleandomycin and ketoconazole, both inhibitors of CYP3A, markedly reduced PNU-159682 formation by HLMs; the reaction was also concentration-dependently inhibited by a monoclonal antibody to CYP3A4/5. Of the 10 cDNA-expressed CYPs examined, only CYP3A4 formed PNU-159682. In addition, PNU-159682 was remarkably more cytotoxic than MMDX and doxorubicin in vitro, and was effective in the two in vivo tumor models tested, i.e., disseminated murine L1210 leukemia and MX-1 human mammary carcinoma xenografts. Conclusions: CYP3A4, the major CYP in human liver, converts MMDX to a more cytotoxic metabolite, PNU-159682, which retains antitumor activity in vivo.

Hyperthermic Isolated Perfusion With Low-Dose Tumor Necrosis Factor α and Doxorubicin for the Treatment of Limb-Threatening Soft Tissue Sarcomas

BackgroundTumor necrosis factor (TNF)-α–based hyperthermic isolated limb perfusion (HILP) is one of the most active available approaches for locally advanced soft tissue sarcomas (STS) of the limbs. The aim of this study was to investigate the anticancer activity of a novel drug regimen including doxorubicin (DXR) and low-dose TNF-α.MethodsHILP with low-dose TNF-α (1 mg) and DXR (8.5 mg/L of limb volume) was given to 21 patients with limb-threatening STS: 14 had primary and 7 had recurrent STS, most of which were high grade (grade 1, n = 3; grade 2, n = 6; grade 3, n = 12). Resection of the tumor remnant was performed 6 to 8 weeks after HILP. TNF-α concentrations in plasma and perfusate were measured throughout perfusion.ResultsA major tumor response was observed at histology and clinical evaluation in 90% and 62% of patients, respectively. After a median follow-up of 30 months, limb salvage and local disease control were achieved in 71% and 81% of cases, respectively. Fourteen patients had moderate regional toxicity, which was resolved in all cases. One patient had severe limb toxicity, which did not require amputation. Systemic side effects were minimal, and there were no postoperative deaths. The perfusate/plasma area under the curve ratio for TNF-α was 56.ConclusionsHILP with low-dose TNF-α and DXR seems to be an active neoadjuvant drug regimen against limb-threatening STS. This therapeutic approach can achieve high limb-sparing surgery rates with acceptable local and negligible systemic toxicity.

Pharmacokinetics of intraperitoneal cisplatin and doxorubicin

Intraperitoneal chemotherapy, mainly when performed during HIIC after cytoreductive surgery, is considered potentially curative for the treatment of solid tumors with spread to the peritoneal surface. When selecting antiblastic agents to be administered intraperitoneally, it is important to bear in mind that a low lipophility and a high molecular weight are the ideal drug characteristics. Drugs with these features allow a favorable ratio to be achieved between peritoneal and plasma concentrations, due to the reduced tendency to diffuse through the plasma-peritoneal barrier, even after extensive removal of the peritoneum. Moreover, a low rate of diffusion through the tumor capillaries implies a low rate of drug clearance, with a higher intratumoral drug accumulation. Among the drugs used so far for intraperitoneal chemotherapy, the combination of CDDP and DXR appears to be one of the most effective available regimens with acceptable local-regional toxicity. CDDP has also been extensively employed as a single agent for ovarian and gastrointestinal cancers, under both normal and hyperthermic conditions, while intraperitoneally administered DXR appears to be of greater potential efficacy when associated with CDDP and hyperthermia (41.5 degrees C) following cytoreductive surgery. In our clinical experience with this drug combination, DXR showed a much more advantageous plasma/peritoneal AUC ratio than CDDP (162 +/- 113 and 20 +/- 6, respectively). On the other hand, it has been demonstrated that very high intraperitoneal concentrations of CDDP can be achieved without incurring significant systemic toxicity by using intravenous injection of sodium thiosulphate during HIIC. Penetration of the tumor mass by CDDP is greater than DXR. This phenomenon is enhanced by hyperthermia and by hypotonic solutions of sodium chloride used as the perfusate. Following experimental and clinical results of TNF alpha-based isolated limb perfusion for locally advanced soft tissue sarcoma or melanoma, greater efforts are being made to exploit the potential effect of this cytokine used in association with hyperthermia and other drugs (i.e., CDDP and DXR) suitable for intraperitoneal infusion/perfusion. However, it is not yet clear whether the observed effect of TNF alpha on the peritoneal-plasma barrier, which seems to favor the passage of both drugs into the systemic circulation, is overcome by the positive effect of this agent on drug penetration into tumor. Further pharmacologic studies should be undertaken to clarify whether or not these interactions will be of benefit to the patient. Likewise, liposomes, which in animal models seem to favor tumor uptake of encapsulated DXR, should now be tested in the clinical setting.

Identification of molecular determinants of tumor sensitivity and resistance to anticancer drugs.

Resistance to drugs is a major problem in cancer chemotherapy. Various cellular mechanisms of drug resistance have been identified in cultured tumor cell lines selected for growth in the presence of sublethal concentrations of various anticancer drugs. They involve drug transport and detoxification, qualitative or quantitative alterations of the drug target, repair of drug-induced DNA lesions, and alterations in signaling or execution of apoptosis. More recently, the possibility to simultaneously analyze the expression of thousands of genes using DNA microarrays has allowed exploring the relationships between gene expression and sensitivity to several anticancer drugs. A number of studies using microarrays for identifying genes governing tumor chemosensitivity focused on tumor cell lines. Some clinical studies have also been carried out to investigate whether tumor gene expression patterns could predict clinical response to chemotherapy. Results of these studies are encouraging, indicating that individualization of drug treatment based on multigenic response-predictive markers is feasible.

Irreversible CYP3A inhibition accompanied by plasma protein-binding displacement: a comparative analysis in subjects with normal and impaired liver function.

In this study, quinine was used as a probe substrate and erythromycin as a prototypical irreversible inhibitor of CYP3A to ascertain whether, like reversible CYP inhibition, the magnitude of irreversible inhibition is also strictly dependent on the status of liver function. The effect of erythromycin on oral quinine disposition was studied in 10 healthy subjects and in 20 patients with cirrhosis of the liver who had varying degrees of liver dysfunction. This effect was shown to be the result of two types of interaction: (i) irreversible inhibition of CYP3A‐mediated quinine metabolism, the extent of which proved to be independent of liver function, and (ii) displacement of quinine from plasma protein–binding sites, the magnitude of the displacement increasing dramatically as liver function worsened. Such an interaction causes limited increases in the total concentration of the displaced drug but disproportionate increases in its free concentration; the latter increases are magnified by liver dysfunction, thereby requiring that the monitoring of free drug concentrations be made mandatory.

Polysialic acid as a drug carrier: evaluation of a new polysialic acid–epirubicin conjugate and its comparison against established drug carriers

This paper explores the potential of polysialic acid (PSA) as a carrier for low molecular weight anticancer drugs. A PSA–epirubicin (Epi) conjugate was synthesized and compared against Epi conjugates containing established carriers, namely: N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers, poly(ethylene glycol) (PEG) and polyglutamic acid (PGA). Biological assessments in the breast cancer cell line MCF-7 and in the anthracycline resistant MCF-7/DX showed that the PSA–Epi conjugate had the highest activity (40% and 30% cell death in the two cell lines at 1 μM Epi equiv., respectively). FACS studies confirmed internalization of all conjugates by cholesterol-dependent endocytosis. PSA–Epi showed release of Epi (40% at 5 h) when incubated with lysosome extracts. In vivo evaluation showed that all conjugates had a significantly longer half-life compared to free Epi. This study also allowed an investigation on the effect of the polymeric carrier on the biological activity of a conjugate, with the biodegradability of the carrier emerging as an important feature.

In vitro hepatic conversion of the anticancer agent nemorubicin to its active metabolite PNU-159682 in mice, rats and dogs: A comparison with human liver microsomes

We recently demonstrated that nemorubicin (MMDX), an investigational antitumor drug, is converted to an active metabolite, PNU-159682, by human liver cytochrome P450 (CYP) 3A4. The objectives of this study were: (1) to investigate MMDX metabolism by liver microsomes from laboratory animals (mice, rats, and dogs of both sexes) to ascertain whether PNU-159682 is also produced in these species, and to identify the CYP form(s) responsible for its formation; (2) to compare the animal metabolism of MMDX with that by human liver microsomes (HLMs), in order to determine which animal species is closest to human beings; (3) to explore whether differences in PNU-159682 formation are responsible for previously reported species- and sex-related differences in MMDX host toxicity. The animal metabolism of MMDX proved to be qualitatively similar to that observed with HLMs since, in all tested species, MMDX was mainly converted to PNU-159682 by a single CYP3A form. However, there were marked quantitative inter- and intra-species differences in kinetic parameters. The mouse and the male rat exhibited V(max) and intrinsic metabolic clearance (CL(int)) values closest to those of human beings, suggesting that these species are the most suitable animal models to investigate MMDX biotransformation. A close inverse correlation was found between MMDX CL(int) and previously reported values of MMDX LD(50) for animals of the species, sex and strain tested here, indicating that differences in the in vivo toxicity of MMDX are most probably due to sex- and species-related differences in the extent of PNU-159682 formation.

Metabolic effects of antiangiogenic drugs in tumors: Therapeutic implications

Antiangiogenic therapy has become a mainstay of cancer therapeutics, but clinical responses are generally short-term owing to the development of secondary resistance. Tumor starvation by antiangiogenic drugs is largely attributed to increased hypoxia and impaired nutrients supply, suggesting that angiogenesis inhibition causes remarkable metabolic perturbations in the tumor microenvironment. We review here recent acquisitions concerning metabolic effects of angiogenesis blockade in tumors and discuss the possibility that some metabolic features of tumor cells - i.e. their dependency from glucose as primary energy substrate - might affect tumor responses to anti-vascular endothelial growth factor treatment. Moreover, we discuss the hypothesis that anti-angiogenic therapy might foster metabolic evolution of tumors. The therapeutic implications of this hypothesis will be discussed further here.