The Prostate Cancer Clinical Trials Consortium (PCCTC) bone scan data capture tool for clinical trials using Prostate Cancer Working Group 2 (PCWG2) criteria: Effect on data accuracy and workload

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Background: PCWG2 Concensus Criteria proposed time-to-event endpoints in early phase clinical trials. Chief among these was time to radiographic progression for bone scintigraphy (BS), based on a standardized definition with additional rulesets to account for early flare. The PCCTC created a tool to operationalize these definitions in clinical trials. We tested the impact of the tool on clinical trial workload and data adequacy.

Methods: The BS capture tool was vetted and amended through nine versions by a multidisciplinary group from PCCTC participating institutions. Accruals at Memorial Sloan-Kettering Cancer Center on two phase III trials using the same drug, contracting research organization (CRO), and electronic data capture system were analyzed. The first trial did not use the PCCTC tool. The second incorporated the tool in its data collection plan and case report form. Workload and data capture adequacy for each trial were determine by examining the total number of imaging queries from the database query reports obtained from the CRO as a function of the total number of scans and patients.

Results: Data from this analysis are found in the table . The relative number of queries per scan was reduced by 85.33% by use of the tool. The queries:scan ratios were 0.82 versus 0.12 before and after the use of the tool respectively; likewise, the ratios of queries: patient were 2.81 vs. 0.44.

Conclusions: Using the PCCTC BS tool to standardize data capture and operationalize PCWG2 radiographic progression criteria, imaging data are more completely reported and workload for study research staff decreased. The reproducibility and feasibility of the BS tool is further being tested in two ongoing phase III studies in which PCWG2 criteria are being clinically qualified. These efforts to quantitate, standardize, and qualify imaging data advance the goal of developing an imaging biomarker in metastatic prostate cancer.

[Table: see text]

No significant financial relationships to disclose.

Setting events in applied behavior analysis: Toward a conceptual and methodological expansion

The contributions of applied behavior analysis as a natural science approach to the study of human behavior are acknowledged. However, it is also argued that applied behavior analysis has provided limited access to the full range of environmental events that influence socially significant behavior. Recent changes in applied behavior analysis to include analysis of side effects and social validation represent ways in which the traditional applied behavior analysis conceptual and methodological model has been profitably expanded. A third area of expansion, the analysis of setting events, is proposed by the authors. The historical development of setting events as a behavior influence concept is traced. Modifications of the basic applied behavior analysis methodology and conceptual systems that seem necessary to setting event analysis are discussed and examples of descriptive and experimental setting event analyses are presented.

Radiological impact of the use of calcium hydroxylapatite dermal fillers

AIM

To report a case series in which the radiological features of the subcutaneous use of calcium hydroxylapatite (CaHa) dermal fillers are described for the first time.

MATERIALS AND METHODS

Five patients with facial hyperattenuating hypermetabolic subcutaneous lesions were identified on 2- [(18)F]-fluoro-2-deoxy-D-glucose (FDG) positron-emission tomography/computed tomography (PET/CT), who gave a history of facial injections to augment physical appearance. Correlation with additional imaging studies was performed.

RESULTS

All cases had subcutaneous high attenuation material on CT (range 280-700HU), which was FDG avid on PET, with a standardized uptake value (SUV) range of 2.9-13.4. Magnetic resonance imaging (MRI) demonstrated a heterogeneous intermediate signal intensity subcutaneous lesion with enhancement post-gadolinium in one case.

CONCLUSIONS

CaHa dermal filler is hyperattenuating on CT, hypermetabolic on FDG-PET imaging, of intermediate signal intensity on MRI, and is a potential cause of a false-positive imaging study.

The plateau outward current in canine ventricle, sensitive to 4-aminopyridine, is a constitutive contributor to ventricular repolarization

BACKGROUND AND PURPOSE

I(Kur) (Ultra-rapid delayed rectifier current) has microM sensitivity to 4-aminopyridine (4-AP) and is an important modulator of the plateau amplitude and action potential duration in canine atria. Kv1.5 encodes I(Kur) and is present in both atria and ventricles in canines and humans. We hypothesized that a similar plateau outward current with microM sensitivity to 4-AP is present in canine ventricle.

EXPERIMENTAL APPROACH

We used established voltage clamp protocols and used 4-AP (50 and 100 microM) to measure a plateau outward current in normal canine myocytes isolated from the left ventricular mid-myocardium.

KEY RESULTS

Action potential recordings in the presence of 4-AP showed significant prolongation of action potential duration at 50 and 90% repolarization at 0.5 and 1 Hz (P<0.05), while no prolongation occurred at 2 Hz. Voltage clamp experiments revealed a rapidly activating current, similar to current characteristics of canine atrial I(Kur), in approximately 70% of left ventricular myocytes. The IC(50) of 4-AP for this current was 24.2 microM. The concentration of 4-AP used in our experiments resulted in selective blockade of an outward current that was not I(to) or I(Kr). Beta-adrenergic stimulation with isoprenaline significantly increased the 4-AP sensitive outward current density (P<0.05), suggesting a role for this current during increased sympathetic stimulation. In silico incorporation into a canine ventricular cell model revealed selective AP prolongation after current blockade.

CONCLUSIONS AND IMPLICATIONS

Our results support the existence of a canine ventricular plateau outward current sensitive to micromolar 4-AP and its constitutive role in ventricular repolarization.

Synchronization in Relaxation Oscillator Networks with Conduction Delays

We study locally coupled networks of relaxation oscillators with excitatory connections and conduction delays and propose a mechanism for achieving zero phase-lag synchrony. Our mechanism is based on the observation that different rates of motion along different nullclines of the system can lead to synchrony in the presence of conduction delays. We analyze the system of two coupled oscillators and derive phase compression rates. This analysis indicates how to choose nullclines for individual relaxation oscillators in order to induce rapid synchrony. The numerical simulations demonstrate that our analytical results extend to locally coupled networks with conduction delays and that these networks can attain rapid synchrony with appropriately chosen nullclines and initial conditions. The robustness of the proposed mechanism is verified with respect to different nullclines, variations in parameter values, and initial conditions.

Dipyridamole potentiates pulmonary vasodilation induced by acetylcholine and nitric oxide in the ovine fetus

Nitric oxide (NO) modulates pulmonary vascular resistance (PVR) in the normal fetus by increasing the cyclic guanosine 3',5'-monophosphate (cGMP) content of pulmonary vascular smooth muscle cells. Although several vasodilator stimuli, including acetylcholine, decrease fetal PVR through the release of endogenous NO, fetal pulmonary vasodilation is often transient despite prolonged treatment. Because cGMP is hydrolyzed and inactivated by cGMP-specific (type 5) phosphodiesterases (PDE5), we hypothesized that PDE5 activity contributes to high fetal PVR and limits the capability of the fetal pulmonary circulation to dilate or sustain vasodilation in response to cGMP-dependent stimuli. To test this hypothesis, we studied the hemodynamic effects of dipyridamole in 19 late-gestation fetal lambs. To determine whether dipyridamole-induced vasodilation is dependent upon basal NO release, we measured the response to dipyridamole before and after pretreatment with the NO synthase antagonist nitro-L-arginine (L-NA) in five fetal lambs. L-NA completely blocked dipyridamole-induced pulmonary vasodilation. To evaluate the effect of dipyridamole on pulmonary vasodilation due to the stimulated release of NO, we studied effects of prolonged intrapulmonary acetylcholine infusions, with and without concomitant administration of low-dose dipyridamole, in six fetal lambs. During prolonged (2-h) infusions, acetylcholine and dipyridamole individually caused transient pulmonary vasodilation. When administered together, pulmonary vasodilation was of greater magnitude and was sustained for the entire study period. To determine the effects of dipyridamole on endothelium-independent pulmonary vasodilation, we investigated the hemodynamic effects of inhaled NO (5 and 20 ppm) alone and in combination with dipyridamole during mechanical ventilation with low FlO2. The combination of dipyridamole with inhaled NO resulted in a greater degree of pulmonary vasodilation than that achieved with inhaled NO alone. We conclude that dipyridamole-induced pulmonary vasodilation is dependent on endogenous (basal) NO production and that dipyridamole potentiates vasodilator responses to endothelium-dependent and -independent dilators in the ovine fetal pulmonary circulation. We speculate that PDES activity opposes vasodilation and maintains high PVR in the normal fetal lung.

Role of nitric oxide and cGMP system in regulation of ductus arteriosus tone in ovine fetus

Although endogenous nitric oxide (NO) modulates basal tone in the fetal pulmonary and systemic circulations, little is known about its role in regulating ductus arteriosus (DA) tone. Immunostaining of DA tissue from late-gestation fetal lambs demonstrated strong staining for endothelial NO synthase (eNOS) in DA endothelium. To study the physiological role of the NO and guanosine 3',5'-cyclic monophosphate (cGMP) system in the DA in vivo, we measured the hemodynamic effects of NG-nitro-L-arginine (L-NNA; 30 mg), a NOS inhibitor, methylene blue (40 mg), a guanylate cyclase inhibitor, and indomethacin (0.8 mg), a cyclooxygenase inhibitor, in 10 chronically prepared late-gestation fetal lambs. L-NNA increased main pulmonary artery (MPA) and aortic pressures (P < 0.05 vs. baseline) but did not change the pressure gradient between the MPA and the aorta. L-NNA caused a small decrease in DA flow and a slight rise in resistance across the DA. Methylene blue increased both MPA pressure and the pressure gradient between the MPA and the aorta from 0.3 +/- 0.2 (baseline) to 7.0 +/- 2.7 mmHg (P < 0.05). Indomethacin increased both MPA pressure and the pressure gradient between the MPA and the aorta from 1.1 +/- 0.4 (baseline) to 6.3 +/- 1.5 mmHg (P < 0.05) after 40 min. Indomethacin decreased DA flow and increased DA resistance. We conclude that eNOS is in fetal DA endothelial cells and that NOS inhibition causes constriction of the DA in vivo. DA constriction after NOS inhibition is minimal, especially in comparison with cyclooxygenase inhibition. Methylene blue also constricts the DA, suggesting that guanylate cyclase activity contributes to DA relaxation. We speculate that, although the NO and cGMP system modulates DA tone, prostaglandins may play a greater role.

Chronic intrauterine pulmonary hypertension alters endothelin receptor activity in the ovine fetal lung

Although endothelin (ET) contributes to the regulation of pulmonary vascular tone in the normal fetus, little is known about its role in pulmonary hypertension in the perinatal period. To examine the role of the ETB receptor in the normal ovine fetal lung, we studied the hemodynamic effects of ET-3 (a selective ETB receptor agonist) before and after RES-701 (a selective ETB receptor antagonist). RES-701 (10 mu g/min for 10 min) did not change basal pulmonary tone and blocked pulmonary vasodilation to ET-3 (500 ng/min for 10 min). To examine the effects of experimental perinatal pulmonary hypertension on activity of the ETA and ETB receptors, we studied the hemodynamic effects of ET-3, ET-1 (a nonselective ETA and ETB receptor agonist), and BQ 123 (a selective ETA receptor antagonist) in 12 chronically prepared late gestation fetal lambs after partial ligation of the ductus arteriosus. Serial changes in the pulmonary vascular effects of these agents were measured early (1-3 d) and late (7-10 d) after partial ductus arteriosus ligation. Left lung total pulmonary resistance in the normal late-gestation fetus was 0.62 +/- 0.01 mm Hg/ml/min (n = 4). After partial ductus arteriosus ligation, total pulmonary resistance increased to 1.2 +/- 0.3 (early; p < 0.05 versus normal), and progressively rose to 1.9 +/- 0.2 mm Hg/ml/min (late; p < 0.05 versus early). Intrapulmonary infusion of ET-3 (500 ng/min for 10 min) increased pulmonary blood flow from 94 +/- 11 to 183 +/- 17 mL/min in the normal fetus, but had no effect during late pulmonary hypertension. Infusions of ET-1 (50 ng/min for 30 min) caused transient pulmonary vasodilation followed by vasoconstriction during early pulmonary hypertension. During late pulmonary hypertension, however, infusion of ET-1 caused predominantly vasoconstriction. Pulmonary vasodilation to BQ 123 (100 mu g/min for 10 min) was greater during late than early pulmonary hypertension (43 versus 21%; p < 0.05). After 10 d of ductus arteriosus ligation, immunoreactive ET-1 content in whole lung tissue was 3-fold higher in hypertensive (n = 7) than control (n = 10) lungs (p < 0.05). We conclude that the ETB receptor contributes little to regulation of basal vascular tone in the normal ovine fetal lung and that chronic intrauterine pulmonary hypertension causes the loss of ETB-mediated vasodilation, progressive ETA-mediated vasoconstriction, and increased lung ET-1 content. We speculate that diminished ETB receptor-mediated vasodilation in combination with enhanced ETA receptor-mediated vasoconstriction and increased ET-1 production contributes to high pulmonary vascular resistance in perinatal pulmonary hypertension.

Dipyridamole, a cGMP phosphodiesterase inhibitor, causes pulmonary vasodilation in the ovine fetus

Endogenous nitric oxide (NO) modulates fetal pulmonary vascular tone by stimulating guanosine 3',5'-cyclic monophosphate (cGMP) production in vascular smooth muscle. Because cGMP is hydrolyzed and inactivated by phosphodiesterase enzymes, we evaluated the hemodynamic effects of two cGMP-specific phosphodiesterase (PDE5) inhibitors, dipyridamole and zaprinast, in the near-term chronically prepared ovine fetus. Brief (10 min) intrapulmonary infusions of dipyridamole caused dose-dependent increases in left pulmonary artery flow and decreases in left pulmonary arterial resistance that persisted for > 40 min after termination of the infusion. Prolonged (2 h) infusions of dipyridamole caused sustained pulmonary vasodilation throughout the infusion period. To compare the hemodynamic effects of dipyridamole with the PDE5 antagonist zaprinast, we studied the responses to equimolar doses of both agents in four fetuses. Zaprinast caused dose-dependent pulmonary vasodilation that was equivalent to that noted with equimolar doses of dipyridamole. To determine whether adenosine is involved with dipyridamole-induced pulmonary vasodilation, we compared the hemodynamic response to dipyridamole before and after administration of the potent adenosine receptor (P1) antagonist 8-phenyltheophylline (8-PT). Pretreatment with 8-PT markedly attenuated adenosine-induced pulmonary vasodilation but had no effect on the hemodynamic response to dipyridamole. We conclude that cGMP-specific phosphodiesterase activity is important in regulating fetal pulmonary vascular tone. In addition, dipyridamole administration causes dose-dependent pulmonary vasodilation that is equivalent to zaprinast and not primarily due to its effects on adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessing and enhancing generalization and social validity of social-skills interventions with children and adolescents

Generalization and social validity are necessary aspects of any applied behavior analytic endeavor. They are especially critical to social-skills training research and practice. Investigators have demonstrated the effectiveness of various learning theory-based interventions in teaching social skills to and increasing peer interactions of children with and without disabilities. However, development of a technology for reliably transferring these changes across different situations or ensuring their persistence over time has proven to be more problematic. From both a conceptual and empirical standpoint, this article reviews progress in and barriers to assessing and enhancing generality of social behavior change and its relationship to social validity. If progress is to be made, then it will be necessary to (a) distinguish between generalization and generality in developing and evaluating social-skills interventions; (b) expand the concept of social validity to give more emphasis to objective measurement of social skills, interventions, and outcomes; and (c) pursue a systematic analysis of generality- and durability-programming tactics.

Effects of 2'-fluorinated arabinosyl-pyrimidine nucleosides on duck hepatitis B virus DNA level in serum and liver of chronically infected ducks

The 2'-fluorinated arabinosyl-pyrimidine nucleosides, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) and 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), are new antiviral compounds with in vitro inhibitory activity against the DNA polymerase of hepadnaviruses. Those compounds also induced permanent inhibition of viral replication in woodchucks chronically infected by woodchuck hepatitis virus. The effects of these antiviral compounds were assessed in ducks chronically infected by duck hepatitis B virus (DHBV). Following intraperitoneal administration for 5 days, FMAU (2 mg/kg/day) and FIAC (10 mg/kg/day) induced a transient decrease in DHBV replication, as shown by the decrease in both the serum and liver DHBV DNA level. After stopping therapy, DHBV replication rebounded immediately to the pretreatment level. The supercoiled form of liver viral DNA was found to be less affected by the therapy. By contrast, no obvious antiviral effect was observed with vidarabine monophosphate (ara-AMP) (80 mg/kg/day) therapy. No sign of toxicity was observed during the course of the treatment. These preliminary results confirmed in the DHBV model the higher efficacy of FIAC and FMAU as compared to ara-AMP. Pharmacokinetic studies are needed to explain the differences observed in viral replication in these 2 models of HBV infection.

Evaluation of 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-ethyluracil in a rabbit model of herpetic keratitis

The nucleoside analog 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5- ethyluracil (FEAU) was tested in a rabbit model of acute herpetic keratitis and its effectiveness compared with that of acyclovir (ACV). FEAU or ACV was applied topically 3 times daily, beginning 3 days post-HSV-1 inoculation and continued for a period of 7 days. FEAU at a concentration of 1% (w/v) or 3% ACV resulted in significant lessening of the severity of corneal lesions, conjunctivitis, iritis, and corneal clouding at 24 to 48 h after beginning chemotherapy. No toxic reaction was observed in any rabbit eyes treated with either FEAU or ACV. The duration of virus shedding into tear film and colonization of the trigeminal ganglia, however, were not reduced by either FEAU or ACV treatment begun 3 days post-inoculation. Fifty percent effective dose (ED50) of FEAU determinations performed on isolates from tear film and on the virus inoculum in secondary rabbit kidney cultures yielded a range of 4.6-7 microM, with two in vitro resistant isolates having ED50S of greater than or equal to 1500 microM of FEAU. Fifty percent cell growth inhibition for FEAU was 3000 microM at 72 h.

Synthesis and anti-HIV-1 activity of 2'-"up"-fluoro analogues of active anti-AIDS nucleosides 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxycytidine (DDC)

1-(3-Azido-2,3-dideoxy-2-fluoro-beta-D-arabinofuranosyl)thymine (6, F-AZT) and 1-(2,3-dideoxy-2-fluoro-beta-D-threopentofuranosyl)cytosine (12, F-DDC) were synthesized from the potent antiherpes virus nucleosides 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)thymine (1, FMAU) and 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) in the hope that introduction of a 2-"up"-fluoro substituent might potentiate the anti-HIV activity of AZT and DDC. FMAU (1) was converted in three steps into 2,3'-anhydro-1-(2-fluoro-2-deoxy-5-O-trityl-beta-D-lyxofuranosyl)thymine (4), which when treated with NaN3 followed by detritylation afforded 6. F-DDC was prepared by two methods. Tritylation of FIAC followed by treatment of the product with thiocarbonyldimidazole afforded the 5'-O-trityl-3'-O-(imidazolyl)thiocarbonyl nucleoside 9. Upon radical reduction of 9 with Bu3SnH and AIBN, 5'-O-trityl-DDC 10 was obtained. Compound 10 was detritylated to give 12, which (when obtained by this procedure) resisted crystallization, but the diacetate 12' was obtained in crystalline form. Alternatively, FAC (14) was converted into N4,O5'-dibenzoyl derivative 15, which was treated with thiocarbonyldiimidazole. Reduction of 16 with Bu3SnH/AIBN followed by debenzoylation afforded 12, which was obtained in crystalline form. F-AZT did not exhibit any significant activity against the human immunodeficiency virus (HIV) in vitro. F-DDC, however, showed activity against HIV-1, but the therapeutic index is much inferior to that of AZT.

Inhibition of simian varicella virus infection of monkeys by 1-(2-deoxy-2- fluoro-1-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU) and synergistic effects of combination with human recombinant interferon-beta

1-(2-Deoxy-2-fluoro-1-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU) has been shown to be a highly effective inhibitor of Simian varicella virus infection in African green monkeys. Administration of FEAU by either intravenous injection or gavage at doses as low as 1 mg/kg/day prevented the development of rash and reduced viremia. The effective dose could be further reduced to 0.2 mg/kg/day when administered in combination with a sub-effective dose of human recombinant interferon-beta. No evidence of toxicity was seen in monkeys treated for 10 days with FEAU doses of 10 mg/kg/day when they were monitored by hematology and clinical chemistry tests and by clinical observations.

Effect of histocompatibility factors on pulmonary retention of indium-111-labeled granulocytes

Granulocyte transfusions are associated with a number of side effects including febrile transfusion reactions and occasionally pulmonary infiltrates. There is evidence that the presence of preformed antibodies may be a cause of these complications. In this study, allogeneic 111Indium-labeled granulocytes were used to evaluate the pulmonary retention of radioactivity in alloimmunized and non-alloimmunized patients in an attempt to assess antibody effect on granulocyte migration. After injection of labeled allogeneic granulocytes into neutropenic patients, the ratios of lung to heart activity were calculated for the first 30 min of scanning. There was significantly greater retention of radioactivity from cells in the lungs of patients who were alloimmunized, having both lymphocytotoxic (anti-HLA) and leuko-agglutinating antibodies, compared to the activity in the lungs of non-alloimmunized patients (P less than .001) or of patients receiving autologous granulocytes (P less than .001). This study demonstrates that labeled, mismatched granulocytes may be retained in the lungs for a significantly longer time in patients with preformed antibodies. This implies that transfusion of large numbers of such mismatched granulocytes, i.e., granulocyte transfusions, may also be retained in the lungs of alloimmunized patients, which could lead to pulmonary compromise. Therefore, granulocyte transfusions from random donors should not be given to alloimmunized patients.

Inhibitory effects of 2'-fluorinated arabinosyl-pyrimidine nucleosides on woodchuck hepatitis virus replication in chronically infected woodchucks

The treatment of woodchuck hepatitis virus infections with 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) and 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), given intraperitoneally, caused complete and permanent decrease of serum virus endogenous DNA polymerase and viral DNA in all treated woodchucks but was associated with severe toxicity. By contrast 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU) induced a sustained, although less dramatic, decrease of viral replication without apparent toxic effect. FEAU was also effective when given orally. However, in both cases this inhibitory effect was transient.

Nucleosides. CXXXV. Synthesis of some 9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-9H-purines and their biological activities

Seven purine nucleosides containing the 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl moiety were synthesized and tested for their antitumor activity. Direct condensation of 3-O-acetyl-5-O-benzoyl-2-deoxy-2-fluoro-D-arabinofuranosyl bromide (1) with N6-benzoyladenine in CH2Cl2 followed by saponification of the product afforded the adenine nucleoside (I, 2'-F-ara-A). Deamination of I with NaNO2 in HOAc gave the hypoxanthine analogue (II, 2'-F-ara-H). The 6-thiopurine nucleoside (III, 2'-F-ara-6MP) was prepared by condensation of 1 with 6-chloropurine by the mercury procedure followed by thiourea treatment and saponification of the product. Methylation of III gave the 6-SCH3 analogue (IV). Raney Ni desulfurization of III afforded the unsubstituted purine nucleoside (V, 2'-F-ara-P). Condensation of 1 with 2-acetamido-6-chloropurine by the silyl procedure afforded the protected 2-acetamido-6-chloropurine nucleoside which served as the precursor for both the guanine and 6-thioguanine nucleosides (VI, 2'-F-ara-G and VII, 2'-F-ara-TG, respectively). Thus, alkaline hydrolysis of the precursor gave VI. Thiourea treatment prior to alkaline hydrolysis gave VII. The new nucleoside, 2'-F-ara-G (VI) is found to be selectively toxic to human T-cell leukemia CCRF-CEM.

Incorporation and metabolism of 2'-fluoro-5-substituted arabinosyl pyrimidines and their selective inhibition of viral DNA synthesis in herpes simplex virus type 1 (HSV-1)-infected and mock-infected Vero cells

The incorporation and metabolism of 2'-fluoro-5-substituted arabinosyl pyrimidine analogs, and their selective inhibition of viral DNA synthesis in herpes simplex virus type 1 (HSV-1)-infected and mock-infected Vero cells were studied by HPLC and CsCl isopycnic density gradient analysis of isolated DNAs. The amounts of radiolabeled analogs incorporated as parent compound following 10 microM exposure for 4 h were 10-fold higher in HSV-1-infected vs mock-infected cells for 2'-fluoro-5-difluoromethyl-Ara-U (F2FMAU); 4.3-fold higher for 5-ethyl deoxyuridine (EdU); 2.6-fold higher for 2'-fluoro-5-methyl-Ara-U (FMAU) and 1.7-fold higher for dThd. For 2'-fluoro-5-ethyl-Ara-U (FEAU), 3.0 pmole of unchanged moiety was incorporated per 10(6) HSV-1-infected cells but no incorporation was detected in mock-infected cells. HPLC profiles showed that the percentages of radiolabeled analogs incorporated as parent compound in the DNA extracted from HSV-1-infected cells were 31.0% for F2FMAU, 99.6% for EdU, 83.5% for FEAU and 98.3% for FMAU; from mock-infected cells, they were 63.6% for F2FMAU, 96.7% for EdU, 97.3% for FMAU and no incorporation into DNA for FEAU was detected. CsCl density gradient analyses of isolated DNA showed that viral DNA synthesis was inhibited 98% by 10 microM FEAU, 92% by 10 microM F2FMAU, 90% by 2 microM FMAU and 80% by 50 microM EdU, whereas cellular DNA synthesis was inhibited by 53, 44, 61, 66 and 54%, respectively. We conclude that: (a) FEAU incorporation into host-cell DNA was not detectable but FEAU was selectively incorporated into HSV-infected cells; (b) FMAU and FEAU were metabolically stable; however, F2FMAU was extensively metabolized; (c) FEAU and F2FMAU were among the most selective inhibitors of HSV-1 DNA synthesis while allowing cellular DNA synthesis to continue.

Increasing social interactions of severely handicapped autistic children

A peer-initiation training procedure was implemented across multiple peer trainers to investigate social interactions between severely withdrawn autistic children and their nonhandicapped peers. For one subject, substantial increases in spontaneous interactions with training and nontraining peers occurred after the peer-initiation procedure was applied across two training exemplars. Spontaneous social interactions continued even after the training procedure was removed. Although experimental control was established with the second subject during training, spontaneous interactions during nontraining periods were primarily with training peers. The results contribute to an emerging data base on the social interactions of autistic and severely withdrawn handicapped children and on peer-initiation training procedures.

Synthesis and biological effects of 2'-fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil

2'-Fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil (FEAU) was synthesized, and its biological activities were compared with those of 2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil (FMAU). Earlier studies indicated that both compounds showed potent anti-herpes simplex virus activity, with a 50% effective dose (ED50) of less than 0.25 microM. In the present study the cell growth inhibitory activity of FEAU (ED50, 200 to 2,060 microM) was found to be about 100-fold less than that of FMAU. With an ED50 ranging from 630 to 3,700 microM, FEAU only weakly inhibited thymidine incorporation into DNA, as compared with FMAU with an ED50 of 9 to 28 microM. Following exposure to [2-14C]FEAU (100 microM), 0.48 pmol/10(6) cells per h was incorporated into the DNA of herpes simplex virus type 1-infected Vero cells, whereas no detectable incorporation was found in uninfected Vero cells or L1210 cells. The Ki of FEAU for thymidine kinase purified from human leukemic cells was greater than 150 microM. For herpes simplex virus type 1- and 2-encoded thymidine kinases, the Kis were 0.6 and 0.74 microM, respectively. Both FEAU and FMAU were relatively nontoxic for mice, with a 50% lethal dose of greater than 800 mg/kg per day (four intraperitoneal doses). However, the lethal dose of FEAU for dogs was 100 mg/kg per day (10 intravenous doses), a dose which is 40- to 80-fold greater than the toxic dose of FMAU. These results suggest that FEAU is a worthy candidate for further development as an antiherpetic agent.

Nucleosides. 139. Synthesis and anticytomegalovirus and antiherpes simplex virus activity of 5'-modified analogues of 2'-fluoroarabinosylpyrimidine nucleosides

In order to determine if modification of the 5'-position reduces or abolishes the antiviral activity of 2'-fluoro-5-iodo-ara-C (FIAC), 2'-fluoro-5-iodo-ara-U (FIAU), or 2'-fluoro-5-methyl-ara-U (FMAU) against human cytomegalovirus (HCMV) and herpes simplex virus (HSV), the 5'-deoxy, 5'-mercapto, and 5'-amino analogues of these nucleosides were prepared. 5'-Deoxy-FIAC and 5'-deoxy-FIAU were prepared by catalytic hydrogenation of 5'-iodo-FIAC and 5'-iodo-FIAU to 5'-deoxy-FAC and 5'-deoxy-FAU, respectively, followed by reiodination at C-5. Reduction of 5'-iodo-FMAU afforded 5'-deoxy-FMAU. These 5'-deoxy nucleosides were found to be inactive against HCMV, indicating that the conversion to 5'-phosphate by the cellular enzyme(s) is a requirement for antiviral activity against this virus. Other 5'-modified (NH2 and SH) analogues were also prepared from 5'-O-tosyl-FIAC and 5'-O-tosyl-FMAU. Treatment of these tosylates with LiN3 in DMF afforded the corresponding 5'-N3 products. Catalytic hydrogenation of 5'-N3-FMAU afforded 5'-NH2-FMAU, whereas 5'-NH2-FIAC was obtained by treatment of 5'-N3-FIAC with Ph3P in pyridine. 5'-Mercapto analogues were prepared by treatment of 5'-O-tosyl-3'-O-acetyl nucleosides with KSAc followed by deacetylation. 5'-NH2-FMAU was the only compound that showed good activity against HSV-1 and HSV-2 in vitro. However, this compound was less potent and had a lower therapeutic index than FMAU.

Cell differentiation effects of 2'-fluoro-1-beta-D-arabinofuranosyl pyrimidines in HL-60 cells

A group of 2'-fluoro and 5-substituted arabinosyl pyrimidines and a group of base-substituted pseudoisocytidine analogs were evaluated for their capacity to induce differentiation in the human promyelocytic leukemia cell line, HL-60. These compounds were compared to 1-beta-D-arabinofuranosylcytosine (Ara-C) by monitoring: (1) inhibition of cell growth; (2) morphological maturation; (3) nitroblue tetrazolium (NBT) reduction; (4) expression of a myeloid differentiation antigen, Mo1; and (5) inhibition of colony formation. Exposure of logarithmically growing cells for 5 days to Ara-C, 2'-fluoro-Ara-C (FAC), 2'-fluoro-5-methyl-Ara-C (FMAC) and 2'-fluoro-5-ethyl-Ara-C (FEAC) resulted in cell growth inhibition at ED50 concentrations of 0.007, 0.11, 1.7 and 18 microM, and at cytostatic concentrations of 0.1, 0.5, 5.0 and 50 microM, respectively. These compounds induced granulocytic and monocytic maturation, reduction of NBT, increased expression of Mo1 antigen and a decrease or loss of both cell proliferation and colony formation in semisolid medium. There were few, if any, cell differentiation effects for the uracil nucleosides and pseudoisonucleosides tested. We found that Ara-C was the most cytotoxic of the compounds, and that when comparing absolute numbers of differentiated cells, i.e. percent of positive cells multiplied by the number of viable cells, FAC, FMAC and FEAC were superior to Ara-C inducing differentiation of HL-60 cells.

Synthesis and biological activities of 5-deaza analogues of aminopterin and folic acid

N-[p-[[(2,4-Diaminopyrido[2,3-d]pyrimidin-6-yl)methyl] amino]benzoyl]-L-glutamic acid (1a, 5-deazaaminopterin) and the 5-methyl analogue (1b) were synthesized in 14 steps from 5-cyanouracil (4a) and 5-cyano-6-methyluracil (4b), respectively, by exploitation of the novel pyrimidine to pyrido[2,3-d]pyrimidine ring transformation reaction. The 5-cyanouracils 4 were treated with chloromethyl methyl ether to the 1,3-bis(methoxymethyl)uracils (5, which were treated with malononitrile in NaOEt/EtOH to give the pyrido[2,3-d]pyrimidines 6. Diazotization of 6 in concentrated HCl afforded the 7-chloro derivatives 8 in high yield. After reduction of 8, the 7-unsubstituted products 9 were reduced in the presence of Ac2O and the products, 6-(acetamidomethyl)pyridopyrimidines 10, were converted into the 6-acetoxymethyl derivatives 12 via nitrosation. After removal of the N-methoxymethyl groups from 12, the 6-(acetoxymethyl)pyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones 14 were converted into 2,4-diamino-6-(hydroxymethyl)pyrido[2,3-d]pyrimidine (15a) and its 5-methyl analogue 15b by the silylation-amination procedure. Compounds 15 were brominated to the 6-bromomethyl derivatives 16, which were treated with diethyl (p-aminobenzoyl)-L-glutamate, and the products 17 were saponified to afford 5-deazaaminopterin (1a) and its 5-methyl analogue 1b. Compound 1b was also prepared by an alternative procedure in 10 steps from cyanothioacetamide and ethyl beta-(ethoxymethylene)acetoacetate via 2,4-diamino-6-(hydroxymethyl)-5-methylpyrido[2,3-d]pyrimidine (15b). 5-Deaza-5-methylfolic acid (2) was also prepared in four steps from 15b. The aminopterine analogues 1 showed significant anticancer activity in vitro and in vivo, whereas the folic acid analogue 2 did not exhibit any significant toxicity.

Activities of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine and its metabolites against herpes simplex virus types 1 and 2 in cell culture and in mice infected intracerebrally with herpes simplex virus type 2

As measured by plaque and yield reduction assays, several metabolites of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) were highly active against herpes simplex virus types 1 and 2. These metabolites included the 2'-deoxy-2'-fluoroarabinosyl derivatives of 5-iodouracil (FIAU), cytosine (FAC), uracil (FAU), and thymine (FMAU). In mice inoculated intracerebrally with herpes simplex virus type 2, the relative order of potency of these compounds and licensed antiviral drugs was as follows: FMAU much greater than FIAC approximately equal to FIAU greater than acyclovir approximately equal to vidarabine much greater than FAC approximately equal to FAU. One of the main metabolites of FMAU, 2'-fluoro-5-hydroxymethyl-arabinosyluracil, was essentially inactive in vivo. FIAC-, FIAU-, FMAU-, FAC-, and FAU-resistant herpes simplex virus variants prepared in cell culture were found to be (i) devoid of viral thymidine kinase, (ii) cross-resistant to one another and resistant to drugs requiring viral thymidine kinase for activation, and (iii) sensitive to vidarabine or phosphonoformate. These results indicate that FIAC, FIAU, and FMAU require the virally encoded thymidine kinase for activation and suggest that the antiviral activity of FAU and FAC in cell cultures is also mediated by this enzyme. The interaction of the fluoroarabinosyl pyrimidine nucleosides with herpes simplex virus thymidine kinase in a cell-free system is also described.

Nucleosides. 136. Synthesis and antiviral effects of several 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-alkyluracils. Some structure-activity relationships

In order to study structure-activity relationships between antiherpetic activity and the size of the C-5 alkyl substituents of 2'-fluoro-ara-U derivatives, six new nucleosides (1c-h) were synthesized. The 5-allyl analogue 1c was prepared by a Pd(II)-catalyzed reaction of 5-(chloromercuri)-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)uracil with allyl chloride. Partial hydrogenation of 1c afforded the 5-n-propyl derivative 1d (FPAU). Nucleosides 1e-h were obtained by condensation of 3-O-acetyl-5-O-benzoyl-2-deoxy-2-fluoro-D-arabinosyl bromide with the corresponding 5-substituted uracils. Preliminary in vitro data show that, as the alkyl side chain is increased by one carbon unit, the antiherpetic potency is decreased by approximately 1 log order. The cytotoxicity also diminishes as the size of the 5-substituent is increased. FPAU exerts good activity against HSV-1 and HSV-2. FiPAU still shows good therapeutic indices, whereas the higher alkyl analogues are essentially inactive.

Nucleosides. 133. Synthesis of 5-alkenyl-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)cytosines and related pyrimidine nucleosides as potential antiviral agents

The synthesis of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)cytosines with a halovinyl or vinyl substituent at C-5 was accomplished from the corresponding 5-iodo (FIAC, 1) and/or 5-chloromercuri nucleoside analogues with use of Li2PdCl4- and Pd(OAc)2-mediated coupling reactions. Thiation of the benzoylated derivative of the 5-ethyluracil nucleoside 3 followed by S-methylation and then ammonolysis provided 5-ethyl-2'-fluoro-ara-C. 5-Ethynyl-2'-fluoro-ara-C (19a) and 5-ethynyl-2'-fluoro-ara-U (19b) were also obtained from the persilylated 5-iodo nucleosides 1 and 16, respectively, by PdII/CuI catalyzed coupling with (trimethylsilyl)acetylene. With use of selective sugar deprotection of the initial coupling products with H2O/Me2SO, the corresponding 5-[2-(trimethylsilyl)ethynyl] derivatives 18a and 18b could be isolated. Most of the new compounds showed activity in vitro against both HSV-1 and HSV-2, as did the known corresponding 5-alkenyluracil nucleosides synthesized earlier. The 5-vinylcytosine and -uracil nucleosides 10 and 24, respectively, were highly effective against HSV-1 (ED90 = 0.40 and 0.043 microM, respectively) and HSV-2 (ED90 = 0.59 and 0.56 microM, respectively). Unlike BVDU, the 2'-fluoroarabinosyl derivatives of 5-(halovinyl)cytosine and -uracil showed activity against both types of herpes simplex virus. The therapeutic indices of these compounds are in some cases superior to those of 2'-fluoro-5-methyl-ara-U (FMAU, 2). Moderate antileukemic activity was observed in vitro for the 5-alkynyl and 5-vinyl compounds. The competition of these compounds with thymidine for viral-induced thymidine kinases was also studied.

Phase I trial of 1-(2'-deoxy-2'-fluoro-1-beta-D-arabinofuranosyl)-5-methyluracil (FMAU)

1-(2'-Deoxy-2'-fluoro-1-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), a new pyrimidine nucleoside, is of potential clinical interest both as an anticancer and as an antiviral drug. FMAU is active in vitro and in vivo against P815 and L1210 cell lines resistant to cytarabine. Moreover, in mice inoculated ic with herpes simplex virus Type II, FMAU is 100-fold more potent than vidarabine or acyclovir. We have conducted a phase I trial of FMAU in 17 patients with advanced cancer. The dose levels studied were 2, 4, 8, 16, 32, 64, and 128 mg/m2/day iv for 5 days. The dose-limiting toxic effect was drug-induced central nervous system dysfunction. Although 32 mg/m2/day for 5 days produced only transient, mild symptoms, severe encephalopathy with extrapyramidal dysfunction occurred at 64 and 128 mg/m2/day for 5 days and contributed to two deaths. No toxicity was observed at less than 32 mg/m2. A dose of 32 mg/m2/day for 5 days is suggested for phase II study. Because of its potent and selective antiviral activity, future trials of low doses of FMAU in immunosuppressed patients with herpes virus infections are under consideration.

Metabolic competition studies of 2'-fluoro-5-iodo-1-beta-d-arabinofuranosylcytosine in vero cells and herpes simplex type 1-infected vero cells

2'-Fluoro-5-iodo-1-beta-D-arabinofuranosylcytosine (FIAC) is a potent antiviral agent with minimal cytotoxicity. In Vero cells, incorporation of labeled dCyd and dThd into the acid-insoluble DNA fraction was, respectively, competitively and noncompetitively inhibited by FIAC. In herpes simplex type 1 (HSV-1) infected Vero cells, these inhibition patterns became noncompetitive. The inhibition constants of FIAC on dThd and dCyd incorporation into the acid-insoluble fraction during a 15-min period were greater than 30 microM which were much higher than the antiviral concentration of FIAC (ED90 = 0.003-0.013 microM) for continuous exposure. Incorporation of dUrd into acid-insoluble DNA was inhibited by 10 microM FIAC in HSV-1-infected Vero cells, but not in uninfected cells. The radioactivity of [2-14C]FIAC was incorporated into the acid-insoluble DNA fraction, and this incorporation in uninfected cells was strongly inhibited by 10 microM dCyd but not by dThd. By contrast, the incorporation in HSV-1-infected Vero cells was strongly inhibited by 10 microM dThd but not by dCyd. These data indicate that FIAC behaves metabolically like dThd, dUrd, or 5-iodo-dUrd in HSV-1-infected cells but like dCyd in noninfected cells. Thus, combined use of dCyd and FIAC may reduce cytotoxicity of FIAC or incorporation of FIAC into host cell DNA without affecting its antiviral activity. This finding is of significance since, for practical reasons, incorporation of FIAC into host cell DNA needs to be reduced as much as possible.

Diagnostic imaging of herpes simplex virus encephalitis using a radiolabeled antiviral drug: autoradiographic assessment in an animal model

To develop a new approach to the diagnosis of herpes simplex encephalitis, we used a radiolabeled antiviral drug, 2'-fluoro-5-methyl-1-beta-D-arabinosyluracil labeled with carbon 14 ([14C]FMAU), as a probe for selectively imaging brain infection in a rat model by quantitative autoradiography. A high correlation was found between focal infection, as defined by immunoperoxidase viral antigen staining, and increased regional [14C]FMAU uptake in brain sections. Two potential sources of false-positive imaging were defined: high concentrations of drug in the choroid plexus because of its higher permeability compared with brain, and drug sequestration by proliferating uninfected cell populations. Our results support the soundness of the proposed strategy of using a labeled antiviral drug that is selectively phosphorylated by herpes simplex virus type 1 thymidine kinase in conjunction with scanning methods for human diagnosis, and also define some of the factors that must be taken into account when planning clinical application.

Effects of certain nucleoside analogues on human cytomegalovirus replication in vitro

Four nucleoside analogues, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), -5-iodouracil (FIAU), -5-methylcytosine (FMAC) and -5-iodocytosine (FIAC), were studied for their effect on human cytomegalovirus (HCMV) replication in vitro. FMAU, FIAU, FMAC and FIAC showed antiviral activities for four strains of HCMV (Major, Clegg, D550 and Towne) in a plaque reduction assay, with a dose required for 50% inhibition (ED50) in the range of 0.1 to 0.65 microM. At a concentration of 1 microM-FMAU or -FIAC, the synthesis of five virus-specific late polypeptides of molecular weights 150 000, 120 000, 67000, 54000 and 27000 was entirely blocked. Quantification of Towne viral DNA synthesis, using complementary RNA-DNA hybridization with a Towne-specific cRNA probe, demonstrated a complete inhibition of HCMV DNA replication at 1 microM of FMAU or FIAC. After the removal of the inhibitors, however, viral DNA synthesis resumed, and infectious virus reappeared, indicating that the inhibition of HCMV replication by these nucleoside analogues was of a virostatic reversible type.

Nucleosides. 129. Synthesis of antiviral nucleosides: 5-alkenyl-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)uracils

Synthesis of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)uracils containing a vinyl (4a), 2-halovinyl (4b-d), or ethyl substituent at C-5 was achieved. These nucleosides were found to be about a log order less active than 2'-fluoro-5-iodo-ara-C (FIAC) against HSV-1, but they are much less cytotoxic against normal human lymphocytes than FIAC. Nucleosides 4a and 4e showed good activity against HSV-1 (ED50 = 0.16 and 0.24 microM, respectively) and HSV-2 (ED50 = 0.69 and 0.65 microM) with very little cytotoxicity (ID50 greater than 100 microM).

Phase I evaluation of 2'-fluoro-5-iodo-1-beta-D-arabinofuranosylcytosine in immunosuppressed patients with herpesvirus infection

2'-Fluoro-5-iodo-1-beta-D-arabinofuranosylcytosine (FIAC) is a potent selective inhibitor of the replication of herpes simplex virus types 1 and 2 (HSV-1, HSV-2), varicella zoster virus, and cytomegalovirus in cell culture systems. FIAC produces an unequivocal therapeutic effect in mice that have been inoculated with a lethal burden of HSV-1. We have administered FIAC to 32 host compromised patients, 30 with advanced cancer, who were experiencing acute herpesvirus infections (varicella zoster, 29; HSV-1, 2; HSV-2, 1); the drug was given by 20 min i.v. infusion twice a day for 7 days. The dosage levels explored were 60, 120, 240, 400, and 600 mg/sq m/day. Drug-induced myelosuppression became evident at 600 mg/sq m/day; thrombocytopenia exceeded leukopenia. The toxic low dose was 400 mg/sq m/day with mild nausea and rare myelosuppression. All 24 varicella zoster patients with cutaneous disease receiving FIAC, greater than or equal to 120 mg/sq m/day, experienced stabilization of cutaneous lesions within 48 to 72 hr; healing began promptly thereafter.

Mechanism of action of 2',5-difluoro-1-arabinosyluracil

Results are described which demonstrate that the cytotoxic action of 2',5-difluoro-1-arabinosyluracil (FFara-Ura) involves conversion to the corresponding 5'-phosphate, FFara-UMP, and subsequent inhibition of thymidylate synthetase. The evidence for this is as follows: (a) cells lacking thymidine kinase are 120-fold more resistant to FFara-Ura; (b) FFara-Ura markedly inhibits the incorporation of 2'-deoxyuridine (dUrd) into DNA with little or no effect on 2'-deoxythymidine (dThd) incorporation; (c) FFara-Ura causes changes in deoxynucleoside triphosphate pool sizes, which are characteristic of specific inhibition of dTMP synthetase. Binding and spectroscopic studies demonstrate that FFara-UMP inactivates dTMP synthetase from Lactobacillus casei in a manner analogous to that described for FdUMP. Furthermore, FFara-Ura is not a substrate for the pyrimidine phosphorylases; the significance of this finding with regard to the possible chemotherapeutic utility of FFara-Ura is discussed.

Activity of 1-(2'-fluoro-2'-deoxy-beta-D-arabinofuranosyl)thymine against herpes simplex virus in cell cultures and rabbit eyes

A new antiviral compound 1-(2'-fluoro-2'-deoxy-beta-D-arabinofuranosyl)thymine (2'-fluoro-5-methyl-ara-uracil [FMAU]), was compared with acyclovir and idoxuridine in vitro against two strains of both herpes simplex virus type 1 (HSV-1) and HSV-2. Determinations of the 50% effective dose varied slightly with each strain and with the host cells employed. The 50% effective dose for FMAU and acyclovir against HSV-1 ranged from 0.1 microM to 0.5 to 0.6 microM in rabbit kidney cells and from 0.5 microM to 0.6 to 0.78 microM in Vero cells. Beginning 4 days post-inoculation, topical FMAU therapy given five times per day to rabbits with acute herpetic keratitis either suppressed or delayed the severity of corneal epithelial involvement, conjunctivitis, iritis, and corneal clouding. Responses to treatment with FMAU were similar to those obtained with acyclovir and significantly better than those attained with idoxuridine and vidarabine. At 30 to 40 days after the end of treatment, rabbit eyes were subjected to iontophoresis with epinephrine in an attempt to induce reactivation and enhance detection of previously latent HSV-1. Latent HSV-1 was detected in 67 to 92% of trigeminal ganglia in FMAU-treated animals and in 90% of placebo-treated animals.

Nucleosides. 123. Synthesis of antiviral nucleosides: 5-substituted 1-(2-deoxy-2-halogeno-beta-D-arabinofuranosyl)cytosines and -uracils. Some structure-activity relationships

The syntheses of several 2'-halogeno-5-substituted-arabinofuranosylcytosines and -uracils are described, and relationships of structure to anti herpes virus activity in vitro were examined. Those arabinonucleosides containing the 2'-fluoro function exhibit, generally, more potent anti herpes virus (HSV) activity than do their 2'-chloro of 2'-bromo analogues. The importance of the fluorine in the 2'-"up" (arabino) configuration for enhancement of antiviral effectiveness is demonstrated by the superior activity of 2'-fluoro-5-iodo-ara-C [3a, FIAC] to that of 2'-fluoro-5-iodo-ribo-C. Of all the nucleosides tested herein, FIAC exhibited the most potent in vitro activity against HSV. 2'-Chloro-5-iodo- and -5-methyl-ara-C (3b and 4b) were 37 to greater than 500 times more effective in vitro against HSV type 2 than against type 1, suggesting that these latter derivatives might serve clinically as useful probes to distinguish between HSV types 1 and 2 in the diagnosis of HSV infections in man.

Comparison of 2'-fluoro-arabinosyl pyrimidine nucleosides and 1-beta-D-arabinofuranosylcytosine on immunological parameters in vitro

1-beta-D-arabinofuranosylcytosine (ara C)3, 2'-fluoro-5-iodo-arabinofuranosyl-cytosine (FIAC) and 2'-fluoro-5-methyl-arabinofuranosyluracil (FMAU) were analyzed for immunosuppressive activity in vitro. In assay systems quantifying both humoral and cellular immune reactivity, FMAU and FIAC were less immunosuppressive than ara C by several orders of magnitude.

Quantitative autoradiographic mapping of herpes simplex virus encephalitis with a radiolabeled antiviral drug

2'-Fluoro-5-methyl-l-beta-D-arabinosyluracil (FMAU) labeled with carbon-14 was used to image herpes simplex virus type 1-infected regions of rat brain by quantitative autoradiography. FMAU is a potent antiviral pyrimidine nucleoside which is selectively phosphorylated by virus-coded thymidine kinase. When the labeled FMAU was administered 6 hours before the rats were killed, the selective uptake and concentration of the drug and its metabolites by infected cells (defined by immunoperoxidase staining of viral antigens) allowed quantitative definition and mapping of HSV-1-infected structures in autoradiograms of brain sections. These results show that quantitative autoradiography can be used to characterize the local metabolism of antiviral drugs by infected cells in vivo. They also suggest that the selective uptake of drugs that exploit viral thymidine kinase for their antiviral effect can, by appropriate labeling, be used in conjunction with clinical neuroimaging techniques to define infected regions of human brain, thereby providing a new approach to the diagnosis of herpes encephalitis in man.