Oncological applications of gene therapy

Despite the rapid technological advances that continue to sustain the field of cancer gene therapy, few individual patients have benefited from the revolution so far. The plethora of clinical trials described confirms that each malignancy will have its own ideal strategy based on the associated molecular defects, and there has been rapid progress from this viewpoint. At the same time, there has been a renewed appreciation for the limitations to gene therapy, which include low efficiency of gene transfer, poor specificity of response and methods to accurately evaluate responses, and lack of truly tumor-specific targets at which to aim. As with all new therapies, we are climbing a steep learning curve in terms encountering treatment-related toxicities, as well as profound ethical and regulatory issues.

Gene therapy: recent progress in the clinical oncology arena

Despite the rapid technological advances that continue to sustain the field of cancer gene therapy, few individual patients have benefited from the revolution so far. The plethora of clinical trials described confirms that each malignancy will have its own ideal strategy based on the associated molecular defects, and there has been rapid progress from this viewpoint. At the same time, there has been a renewed appreciation for the limitations to gene therapy, which include low efficiency of gene transfer, poor specificity of response and methods to accurately evaluate responses, and lack of truly tumor-specific targets at which to aim. As with all new therapies, we are climbing a steep learning curve in terms encountering treatment-related toxicities, as well as profound ethical and regulatory issues.

Steady-state and transient kinetics of Escherichia coli nitric-oxide dioxygenase (flavohemoglobin). The B10 tyrosine hydroxyl is essential for dioxygen binding and catalysis

Escherichia coli expresses an inducible flavohemoglobin possessing robust NO dioxygenase activity. At 37 degrees C, the enzyme shows a maximal turnover number (V(max)) of 670 s(-1) and K(m) values for NADH, NO, and O(2) equal to 4.8, 0.28, and approximately 100 microM, respectively. Individual reduction, ligand binding, and NO dioxygenation reactions were examined at 20 degrees C, where V(max) is approximately 94 s(-1). Reduction by NADH occurs in two steps. NADH reduces bound FAD with a rate constant of approximately 15 microM(-1) s(-1), and heme iron is reduced by FADH(2) with a rate constant of 150 s(-1). Dioxygen binds tightly to reduced flavohemoglobin, with association and dissociation rate constants equal to 38 microM(-1) s(-1) and 0.44 s(-1), respectively, and the oxygenated flavohemoglobin dioxygenates NO to form nitrate. NO also binds reversibly to reduced flavohemoglobin in competition with O(2), dissociates slowly, and inhibits NO dioxygenase activity at [NO]/[O(2)] ratios of 1:100. Replacement of the heme pocket B10 tyrosine with phenylalanine increases the O(2) dissociation rate constant approximately 80-fold and reduces NO dioxygenase activity approximately 30-fold, demonstrating the importance of the tyrosine hydroxyl for O(2) affinity and NO scavenging activity. At 37 degrees C, V(max)/K(m)(NO) is 2,400 microM(-1) s(-1), demonstrating that the enzyme is extremely efficient at converting toxic NO into nitrate under physiological conditions.

Effectiveness of the Quick Medical Reference as a diagnostic tool

A number of computer-based systems with diagnostic capabilities have been developed for internal medicine. Quick Medical Reference (QMR) is one such program. The authors describe key features of QMR and report on their study of its effectiveness as a diagnostic tool. They investigated how frequently the correct diagnosis would appear among the 5 highest ranked diagnoses generated by QMR. The charts of 1144 consecutive patients admitted to a teaching unit were retrospectively screened. Eligible cases included those referred for investigation of an undiagnosed illness with an objectively proven final diagnosis (n = 154). Two physicians familiar with, but not experts in, the use of QMR entered clinical information abstracted from the patients' charts into the program. Physician A obtained the correct diagnosis in 62 (40%) of the 154 cases, and physician B was successful in 56 (36%) of the cases. The authors use study cases to illustrate QMR's strengths and weaknesses.

Muscarinic facilitation of the occurrence of depolarization-induced suppression of inhibition in rat hippocampus

Depolarization-induced suppression of inhibition is a transient decrease in GABAergic input to a hippocampal pyramidal cell following a brief depolarization of that cell. When recorded under whole-cell voltage clamp, monosynaptic, bicuculline-sensitive, GABA(A)-mediated currents are suppressed for a period lasting up to 1 min in response to a retrograde signal released by the pyramidal cell. The depolarization-induced suppression of inhibition process affects spontaneous, action-potential-dependent inhibitory postsynaptic currents, but suppression of these currents is seldom observed in the absence of carbachol, a cholinergic agonist. Because of the central roles played by cholinergic and GABAergic transmission in the regulation of hippocampal rhythmic activity, it will be important to understand the mechanism by which carbachol facilitates the appearance of depolarization-induced suppression of inhibition. As preliminary steps in the investigation of cholinergic actions on depolarization-induced suppression of inhibition, it is necessary to determine which cholinergic receptors are involved and the degree to which activation of these receptors is required for depolarization-induced suppression of inhibition. Nicotine did not mimic the effects of carbachol, and mecamylamine, a nicotinic receptor antagonist, did not block them. In contrast, the actions of carbachol were abolished by atropine and other muscarinic receptor antagonists. The actions of antagonists with relative selectivities for various subtypes of muscarinic receptors [4-diphenylacetoxy-N-methylpiperidine methiodide, pirenzepine, 11-([2-1-piperidinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzod iaz epine-6-one] suggested that cholinergic facilitation of the occurrence of depolarization-induced suppression of inhibition is likely to be mediated through muscarinic receptors of the M1 or M3 rather than M2 subtype. Despite its potent facilitation of the occurrence of depolarization-induced suppression of inhibition, muscarinic stimulation was not required for expression of depolarization-induced suppression of inhibition. Occasionally, depolarization-induced suppression of inhibition of spontaneous inhibitory postsynaptic currents occurred in the absence of carbachol and could not be blocked by atropine, and hence was not likely to be mediated by endogenous acetylcholine. Also, depolarization-induced suppression of inhibition of monosynaptically evoked inhibitory postsynaptic currents occurred without carbachol perfusion, and this was also insensitive to atropine. Therefore, the mechanism of depolarization-induced suppression of inhibition is not dependent on muscarinic receptor activation. Nevertheless, in vivo, septal cholinergic input to the hippocampus may provide the necessary activation of interneurons to allow depolarization-induced suppression of inhibition to occur.

Genetic prodrug activation therapy for breast cancer: A phase I clinical trial of erbB-2-directed suicide gene expression

PURPOSE

This trial was designed to test the safety and efficacy of a tumor-specific genetic prodrug activation therapy targeted by use of the human erbB-2 gene promoter. The erbB-2 oncogene is overexpressed in approximately 20% of cases of breast cancer and is associated with poor prognosis.

PATIENTS AND METHODS

Twelve breast cancer patients received transcriptionally targeted gene therapy in a phase I clinical trial using direct intratumoral injection of plasmid construct combined with systemic administration of prodrug. The genetic prodrug activation therapy is specifically targeted to erbB-2-overexpressing breast cancer cells by use of a therapeutic cassette that contains the Escherichia coli cytosine deaminase gene driven by the tumor-specific erbB-2 promoter, thus allowing activation of fluorocytosine to the active cytotoxic fluorouracil only within tumor cells that express the oncogene.

RESULTS

The approach was shown to be safe and to result in targeted gene expression in up to 90% of cases. Using a number of different assays, we demonstrated that significant levels of expression of the suicide gene were specifically restricted to erbB-2-positive tumor cells, confirming the selectivity of the approach.

CONCLUSION

The results of this study, the first targeted gene therapy for breast cancer and the first to use the cytosine deaminase system in human subjects, are encouraging for the development of genetic prodrug activation therapies that exploit the transcriptional profile of cancer cells.

Essentials of radiation oncology chart design

Medical Dosimetrists are commonly called upon to participate in the design of radiation oncology treatment records. The Medical Dosimetrist is uniquely qualified to provide input in the areas of treatment planning, simulation and delivery documentation. An idealized chart can facilitate the planning and delivery of quality patient care and lead the user to document such care. This publication outlines the essential minimum requirements for inclusion in a radiation oncology treatment chart. Conventional treatment record keeping has been by hard-copy documentation. Paperless treatment record models are presently being tested for efficacy. Either approach should seek to: maintain quality of patient care, enhance communication, and provide integrity in documentation.

Intravenous pharmacokinetics and absolute oral bioavailability of dolasetron in healthy volunteers: part 1

In this first part of a two-part investigation, the intravenous dose proportionality of dolasetron mesylate, a 5-HT3 receptor antagonist, and the absolute bioavailability of oral dolasetron mesylate were investigated. In an open-label, randomized, four-way crossover design, 24 healthy men between the ages of 19 and 45 years received the following doses: 50, 100, or 200 mg dolasetron mesylate administered by 10-min intravenous infusion or 200 mg dolasetron mesylate solution administered orally. Serial blood and urine samples were collected for 48 h after dosing. Following intravenous administration, dolasetron was rapidly eliminated from plasma, with a mean elimination half-life (t1/2) of less than 10 min. Dolasetron was rarely detected in plasma after oral administration of the 200 mg dose. Hydrodolasetron, the active primary metabolite of dolasetron, appeared rapidly in plasma following both oral and intravenous administration of dolasetron mesylate, with a mean time to maximum concentration (t(max)) of less than 1 h. The mean t1/2 of hydrodolasetron ranged from 6.6-8.8 h. The plasma area under the concentration-time curve (AUC0-infinity)) for both dolasetron and hydrodolasetron increased proportionally with dose over the intravenous dose range of 50-200 mg dolasetron mesylate. Approximately 29-33%) and 22% of the dose was excreted in urine as hydrodolasetron following intravenous and oral administration of dolasetron, respectively. For dolasetron as well as hydrodolasetron, mean systemic clearance (C1), volume of distribution (Vd), and t1/2 were similar at each dolasetron dose. The mean 'apparent' bioavailability of dolasetron calculated using plasma concentrations of hydrodolasetron was 76%. The R(+) enantiomer of hydrodolasetron represented the majority of drug in plasma (> 75%) and urine (> 86%). Dolasetron was well tolerated following both oral and intravenous administration.

Single- and multiple-dose pharmacokinetics of oral dolasetron and its active metabolites in healthy volunteers: part 2

The single- and multiple-dose pharmacokinetics and dose-proportionality of oral dolasetron and its active metabolites over the therapeutic dose range was investigated in 18 healthy men. In an open-label, randomized, complete three-way crossover design, each subject received three separate doses: 50, 100, and 200 mg doses of dolasetron mesylate solution given orally. Each dose was administered on the morning of Days 1 and 3-7 during each of the three treatment periods. Serial blood and urine samples were collected for 48 h after the first and last doses. Blood was analysed for dolasetron and hydrodolasetron concentrations; urine was analysed for dolasetron, the R(+) and S(-)-enantiomers of hydrodolasetron, and the 5'-hydroxy and 6'-hydroxy metabolites of hydrodolasetron. Dolasetron was rarely detected in plasma. Hydrodolasetron was formed rapidly, with a time to maximum concentration (t(max)) of less than 1 h. Steady-state conditions for hydrodolasetron were reached 2-3 days after starting once-daily dosing. Although statistical significance was found for hydrodolasetron AUC(0->infinity) and C(max) between dose groups after both single and multiple doses of dolasetron, the differences were small and unlikely to be of clinical significance. About 17-22% of the dose was excreted in urine as hydrodolasetron, with the majority (> 83%) as the R(+) enantiomer.

Development of a mouse model system, coding assignments and identification of the genome segments controlling virulence of African horse sickness virus serotypes 3 and 8

Attenuated (att) and wild type (wt) strains of the nine AHSV serotypes were evaluated for virulence in adult Balb C mice. Although most were avirulent in this system, isolates of AHSV 1att, 3wt, 3att, 4wt, 5att, 7att and 8att caused some mortality when administered via an intranasal route. After plaque cloning, only the attenuated vaccine strain of AHSV 7att caused any mortality via an intravenous route. AHSV 3att and AHSV 8wt were virulent (V) and avirulent (AV) (respectively) in the mouse model and were selected as parental strains for production of genome segment reassortants. These progeny virus strains were plaque cloned, then characterised to identify the genome segments that influence virulence of AHSV in the mouse model. Three virulence phenotypes were observed: fully virulent (V); fully avirulent (A); and a novel intermediate virulence (N) not expressed by either parental strain. Genome segment 2 (encoding outer capsid protein VP2) from the avirulent parent appeared to have a controlling influence in production of the A phenotype. Reassortants with the V phenotype all contained segment 2 from the virulent parent, however in each case they also contained genome segments 5 and 10, also from AHSV 3 (V). Genome segments 5 and 10 encode the smaller outer capsid protein VP5 and the non structural proteins NS3/NS3a, respectively. A combination of genome segments 2, 5 and 6 from the avirulent parent and segment 10 from the virulent parent were found in each of the virus strains with the N phenotype. However, comparison of two reassortants (A79 and A790), which differ only in a single segment, showed that replacement of genome segment 10 from the avirulent parent with that from the virulent parent, conferred the N phenotype on A790.

Phylogenetic analysis of African horse sickness virus segment 10: sequence variation, virulence characteristics and cell exit

African horse sickness virus (AHSV) genome segment 10 encodes the non-structural proteins NS3/NS3a, which is involved in release of virus from cells. Full length segment 10 cDNAs were amplified by reverse transcription-polymerase chain reaction, from isolates of AHSV serotypes 2, 3, 4, 5, 7, 8 and 9. These cDNAs were cloned, sequenced and their phylogenetic relationships analysed. High levels of sequence homology were detected in segment 10 from some isolates of different serotypes, confirming that they could be grouped on this basis (serotypes 4, 5, 6 and 9 (group alpha); serotypes 3 and 7 (group beta); serotypes 1, 2, and 8 (group gamma). However, data from bluetongue virus (the prototype orbivirus) indicate that the AHSV serotype is determined exclusively by the structural outer coat proteins VP2 and VP5, encoded by genome segments 2 and 5 respectively. Therefore, as a direct consequence of genome segment reassortment between AHSV strains from different serotypes, the differences observed in segment 10 do not give a reliable indication of virus serotype. Segment 10 of AHSV 3 (virulent) and AHSV 3att (attenuated) were also analysed. These strains, together with AHSV 8, have been used to study of the genetic basis of virulence using reassortment (O'Hara et al., this publication). Virus release studies, using Culicoides cell cultures, indicate that differences in segment 10 of AHSV 3att and 8 can influence the timing of virus release from the infected cell.

Nitric oxide dioxygenase: an enzymic function for flavohemoglobin

Nitric oxide (NO*) is a toxin, and various life forms appear to have evolved strategies for its detoxification. NO*-resistant mutants of Escherichia coli were isolated that rapidly consumed NO*. An NO*-converting activity was reconstituted in extracts that required NADPH, FAD, and O2, was cyanide-sensitive, and produced NO3-. This nitric oxide dioxygenase (NOD) contained 19 of 20 N-terminal amino acids identical to those of the E. coli flavohemoglobin. Furthermore, NOD activity was produced by the flavohemoglobin gene and was inducible by NO*. Flavohemoglobin/NOD-deficient mutants were also sensitive to growth inhibition by gaseous NO*. The results identify a function for the evolutionarily conserved flavohemoglobins and, moreover, suggest that NO* detoxification may be a more ancient function for the widely distributed hemoglobins, and associated methemoglobin reductases, than dioxygen transport and storage.

Use of transcriptional regulatory elements of the MUC1 and ERBB2 genes to drive tumour-selective expression of a prodrug activating enzyme

In order to exploit differences in gene expression between normal and malignant cells for genetic prodrug-activation therapy, we have generated recombinant retroviruses containing the herpes simplex virus thymidine kinase coding region cloned downstream of sequences derived from the 5'-flanking regions of the MUC1 and ERBB2 genes. Transduction with retroviruses containing MUC1 promoters resulted in an increase in GCV sensitivity in MUC1 positive cells. A further increase in GCV sensitivity was achieved when MUC1-positive cells were transduced with retroviruses containing chimeric-MUC1/ERBB2 promoters. No significant sensitization to GCV was observed when MUC1-negative cells were transduced with these recombinant retroviruses. These results suggest that one may be able to develop a tumour-selective therapy by utilizing the transcriptional regulatory regions of the MUC1 and ERBB2 genes to drive the expression of suicide genes.

Pharmacokinetics of dolasetron after oral and intravenous administration of dolasetron mesylate in healthy volunteers and patients with hepatic dysfunction

In previous studies, dolasetron was shown to have both renal and hepatic elimination mechanisms. This study was conducted to determine the impact of varying degrees of hepatic dysfunction on the pharmacokinetics and safety of dolasetron and its reduced metabolites. Seventeen adults were studied: six healthy volunteers (group I), seven patients with mild hepatic impairment (Child-Pugh class A; group II), and four patients with moderate to severe hepatic impairment (Child-Pugh class B or C1; group III). Single 150-mg doses of dolasetron mesylate were administered intravenously and orally, with a 7-day washout period separating treatments. After intravenous administration, no differences were observed between healthy volunteers and patients with hepatic impairment in maximum plasma concentration (Cmax), areas under the plasma concentration-time curve (AUC), or elimination half-life (t1/2) of intact dolasetron. No significant differences were found in Cmax, AUC, or apparent clearance (C(lapp)) of hydrodolasetron, the primary metabolite of dolasetron. The mean t1/2 increased from 6.87 hours in group I to 11.69 hours in group III. After oral administration, C(lapp) of hydrodolasetron decreased by 42%, and Cmax increased by 18% in patients with moderate to severe hepatic impairment. There were less changes in patients with mildly hepatic impairment. Total percentage of dose excreted as metabolites was similar for healthy volunteers and patients with hepatic impairment, although urinary metabolite profiles differed slightly. Dolasetron was well tolerated and there were no apparent differences in adverse effects between groups or treatments. Because hepatic impairment did not influence Cl(app) of hydrodolasetron after intravenous administration, and the range of plasma concentrations of hydrodolasetron after oral administration was not different from those observed in healthy volunteers, dosage adjustments are not recommended for patients with hepatic disease and normal renal function.

Neuropathic pain in cancer patients: mechanisms, syndromes, and clinical controversies

The identification of a neuropathic pain syndrome in a cancer patient requires a focused clinical evaluation based on knowledge of common neuropathic pain syndromes. If a tumor is directly involved in the etiology of the pain, oncologic treatment is an initial consideration and may include surgery, radiation, or chemotherapy. There is no single accepted algorithm for the analgesic treatment of neuropathic pain and a systematic approach utilizing therapeutic trials of specific agents at gradually increasing doses is warranted. A trial of opioids, perhaps in combination with an NSAID, is warranted. If the pain is relatively unresponsive to an opioid, a trial with an adjuvant analgesic is reasonable. For example, a tricyclic antidepressant might be selected early for patients with continuous dysesthesia, and early treatment with an anticonvulsant might be used if the pain is predominantly lancinating or paroxysmal. Other adjuvant analgesics can be selected if there is insufficient response to these agents. A trial of sympathetic blockade, pharmacologic, anesthetic or surgical, should be considered in patients with evidence of causalgia or reflex sympathetic dystrophy. Physiatric modalities such as massage, heat, or cold; counterstimulation or transcutaneous electrical nerve stimulation (TENS), and orthopedic interventions, such as braces and splints may be useful. Epidural injections or neurostimulation of the spinal cord or brain can be considered in selected cases where appropriate expertise is available. Treatment of neuropathic pain remains a challenge for both clinicians and patients. The complexity of syndromes and underlying etiologic mechanisms warrants further clinical trials to determine the best treatment modalities for individual pain syndromes.

N-ethylmaleimide blocks depolarization-induced suppression of inhibition and enhances GABA release in the rat hippocampal slice in vitro

Regulation of synaptic, GABAA receptor-mediated inhibition is a process of critical importance to normal brain function. Recently, we have described a phenomenon in hippocampus of a transient, yet marked, decrease in spontaneous, GABAA receptor-mediated IPSCs after depolarization activated Ca2+ influx into a pyramidal cell. This process, depolarization-induced suppression of inhibition (DSI), is absent in hippocampal cells that previously had been exposed to pertussis toxin in vivo, implicating a G-protein in the DSI process. To circumvent the problem that a single cell cannot be studied before and after G-protein block using the pertussis toxin pretreatment method, we have used the sulfhydryl alkylating agent N-ethylmaleimide (NEM), which blocks pertussis toxin-sensitive G-proteins, to determine whether acute inhibition of G-proteins can eliminate DSI of spontaneous IPSCs (sIPSCs). In whole-cell recordings from CA1 pyramidal cells that were first determined to express DSI, we have found that NEM does block DSI of sIPSCs. We also report that DSI of monosynaptic, evoked IPSCs is blocked by NEM, suggesting that a similar mechanism underlies both forms of DSI. It was of interest that DSI was abolished at a time when NEM had increased, not decreased, GABA transmission. Indeed, NEM greatly increased quantal GABA release by a Ca(2+)-independent mechanism, an observation with potentially important implications for understanding synaptic GABA release.

Retrograde signalling in depolarization-induced suppression of inhibition in rat hippocampal CA1 cells

1. We have investigated the phenomenon of 'depolarization-induced suppression of inhibition' (DSI) using whole-cell voltage-clamp techniques in Ca1 pyramidal cells of rat hippocampal slices. DSI was induced by eliciting voltage-dependent calcium (Ca2+) currents with 1 s voltage steps of +60 to +90 mV from the holding potential. DSI was apparent as a reduction in synaptic GABAA responses for a period of about 1 min following the voltage step. 2. TTX-sensitive spontaneous IPSCs (sIPSCs) were susceptible to DSI, while TTX-resistant miniature inhibitory postsynaptic current (mIPSCs) were not. Miniature IPSCs are ordinarily infrequent and independent of external Ca2+ in the CA1 region. To increase the frequency of mIPSCs and to induce a population of Ca(2+)-sensitive mIPSCs, we increased the bath K+ concentration to 15 mM. The increased mIPSCs were also insensitive to DSI, however. 3. T whole-cell pipette-filling solution contained 5 mM 2(triethylamino-N-(2,6-dimethyl-phenyl)acetamide (QX-314) to block voltage-dependent Na+ currents and caesium to block K+ currents. Nevertheless, bath application of 50 microM 4-aminopyridine (4-AP) or 250 nM veratridine both clearly reduced DSI, evidently by acting at presynaptic sites. 4. The amplitudes of monosynaptically evoked IPSCs (elicited in the presence of 10 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 50 microM 2-amino-5-phosphonovaleric acid (APV)) were dramatically reduced during the DSI period. Weak stimulation produced small IPSCs and occasional 'failures' of transmission during the control period. The percentage of failures increased markedly during the DSI period. Moderate-intensity stimulation produced larger IPSCs that were often composed of distinguishable multiquantal components. All-or-none failures of multiquantal IPSC components also occurred during DSI. 5. The degree of paired-pulse IPSC depression did not change during DSI, whereas it was decreased, as expected, by baclofen. 6. We conclude that the data represent novel evidence that DSI is mediated by a retrograde signalling process possibly involving presynaptic axonal conduction block.

Direct cell killing by suicide genes

Cell death can be induced by genetic intervention in a variety of ways. We review genetic prodrug activation therapies using both mammalian and non-mammalian enzyme systems as well as the expression of toxin genes and apoptotic triggers. Targeting of the genetic intervention using both transductional restriction and transcriptional control elements is examined in both in vitro and in vivo systems, and the present state of clinical trials is reviewed.

NIRCA: a rapid robust method for screening for unknown point mutations

We describe a method for screening for dispersed point mutations, based on the observation that RNase frequently cleaves both strands of base pair mismatches in duplex RNA targets. The mismatched substrates are generated by in vitro transcription of wild-type and mutant templates amplified by the PCR or reverse transcription (RT)-PCR; bacteriophage promoters are incorporated into the PCR primers to permit both strands of the products to be transcribed into RNA. Complementary wild-type and mutant transcripts are hybridized and treated with RNase, and the cleavage products are separated on agarose gels and detected by visualization of the ethidium-stained sample under UV light. The method is thus non-isotopic, and since the cleavage products remain double-stranded during analysis, the labor-intensive RNase inactivation steps required in the original procedure can be eliminated. Also, nonspecific background cleavage is reduced so that longer target regions (1 kb) can be screened in a single step. The Non-Isotopic RNase Cleavage Assay (NIRCA) achieved a detection rate of 88%-90% in blind studies in a Factor IX model system, and it was also used to detect unknown p53 mutations in breast tumor samples. NIRCA provides a rapid method for sensitive, non-isotopic, high-throughput genetic screening.

MDL 201,307: a novel benzothiazepine modulator of multiple drug resistance

A series of novel benzothiazepine derivatives were evaluated for their relative potential to reverse multiple drug resistance (MDR) phenotype in vitro as well as for their relative cardiovascular activity and neurotoxicity. Compounds were evaluated for antiMDR activity using Chinese hamster ovary cells with derived resistance to either vincristine or doxorubicin, or a human lymphoblastic leukemia line with resistance to vinblastine. Lead compounds with good antiMDR activity were further evaluated for their relative potential to exhibit cardiovascular and neurological pharmacodynamic activity. A single compound, MDL 201,307 with good antiMDR activity and low cardiovascular and neurologic activity was chosen for further study. In contrast to (R)-verapamil, MDL 201,307 showed only a weak potential to block calcium channels. Using a series of related murine fibrosarcoma cell lines (UV-2237M) with varying levels of resistance to doxorubicin, it was shown that MDL 201,307 augmented inhibition of growth due to doxorubicin. The antiMDR compound was also effective in enhancing the cytotoxicity of actinomycin-D and vinblastine although it was ineffective in increasing cytotoxicity of the nonMDR compound, 5FU. MDL 201,307 increased uptake and decreased efflux of doxorubicin suggesting that MDL 201,307 blocks the GP170-mediated efflux pump mechanism. MDL 201,307 represents a novel antiMDR agent with diminished potential for cardiovascular activity and neurologic interactions which presently limit many of the currently available first and second generations of antiMDR compounds.

Dose-ranging evaluation of the antiemetic efficacy of intravenous dolasetron in patients receiving chemotherapy with doxorubicin or cyclophosphamide

Selective 5-HT3 antagonists have proven to be safe and effective for the prevention of chemotherapy-induced nausea and vomiting. Dolasetron is a new highly selective addition to this class of antiemetics that has been shown to have significant antiemetic activity in patients receiving cisplatin-containing regimens. This pilot study was designed to evaluate the antiemetic efficacy of dolasetron in cancer patients receiving doxorubicin and/or cyclophosphamide. This study used an open-label, non-randomized design to evaluate the efficacy and safety of intravenous dolasetron in the prevention of emesis in patients receiving doxorubicin (25-75 mg/m2) and/or cyclophosphamide (400-1200 mg/m2). Sixty-nine patients received a single, intravenous dose of dolasetron over 15-20 min beginning 30 min prior to the start of chemotherapy. Dose levels of dolasetron studied were: 0.3, 0.6, 1.2, 1.8 and 2.4 mg/kg. Patients were monitored for emesis, nausea and adverse events for 24h after the start of chemotherapy. Overall, 61% of patients experienced complete control of emesis. No significant trend towards increased antiemetic efficacy (P = 0.076) or nausea control with increasing dolasetron dose was noted, although the power to detect significant differences was limited by the small number of patients on the 0.3-mg/kg and 2.4-mg/kg dose levels. Age, gender, and type of chemotherapy were significant predictors of complete antiemetic control. Adverse events were generally mild and included headache, chills, lightheadedness, fever, diarrhea, dizziness, and asymptomatic prolongation of ECG intervals. Intravenous dolasetron is safe and effective in the prevention of emesis induced by doxorubicin and/or cyclophosphamide.

Your PC can enhance staff and patient education

Obtaining education materials for both staff and patients can be expensive. Tracking staff certification requirements and available references for individual units can be time consuming and awkward. Using a regular home personal computer and inexpensive software applications, the staff nurse, educator, and manager can produce quality education products, maintain records, and graph representation of administrative trends.

Influence of a sampling review process for radiation oncology quality assurance in cooperative group clinical trials--results of the Radiation Therapy Oncology Group (RTOG) analysis

The Radiation Therapy Oncology Group (RTOG) designed a random sampling process and observed its influence upon radiotherapy review mechanisms in cooperative group clinical trials. The method of sampling cases for review was modeled from sampling techniques commonly used in pharmaceutical quality assurance programs, and applied to the initial (on-study) review of protocol cases. 'In control' (IC) status is defined for a given facility as the ability to meet minimum compliance standards. Upon achieving IC status, activation of the sampling process was linked to the rate of continued patient accrual for each participating institution in a given protocol. The sampling design specified that > or = 30% cases not in compliance would be detected with 80% power. A total of 458 cases was analyzed for initial review findings in four RTOG Phase III protocols. Initial review findings were compared with retrospective (final) review results. Of the 458 cases analyzed, 370 underwent initial review at on-study, while 88 did not require review as they were enrolled from institutions that had demonstrated protocol compliance. In the group that had both initial and final review, 345/370 (93%) were found to have followed the protocol or had a minor variation. Of the exempted cases, 79/88 (90%) were found to be per protocol or a minor variant. The sampling process proved itself to be cost-effective and resulted in a noticeable reduction in the workload, thus providing an improved approach to resource allocation for the group. Continued evaluation of the sampling mechanism is appropriate as study designs and participants vary over time, and as more data become available to study.(ABSTRACT TRUNCATED AT 250 WORDS)