Combined immunosuppression and radiotherapy in thyroid eye disease (CIRTED): a multicentre, 2 × 2 factorial, double-blind, randomised controlled trial

BACKGROUND

Standard treatment for thyroid eye disease is with systemic corticosteroids. We aimed to establish whether orbital radiotherapy or antiproliferative immunosuppression would confer any additional benefit.

METHODS

CIRTED was a multicentre, double-blind, randomised controlled trial with a 2 × 2 factorial design done at six centres in the UK. Adults with active moderate-to-severe thyroid eye disease associated with proptosis or ocular motility restriction were recruited to the trial. Patients all received a 24 week course of oral prednisolone (80 mg per day, reduced to 20 mg per day by 6 weeks, 10 mg per day by 15 weeks, and 5 mg per day by 21 weeks) and were randomly assigned via remote computerised randomisation to receive either radiotherapy or sham radiotherapy and azathioprine or placebo in a 2 × 2 factorial design. Randomisation included minimisation to reduce baseline disparities in potential confounding variables between trial interventions. Patients and data analysts were masked to assignment, whereas trial coordinators (who monitored blood results), pharmacists, and radiographers were not. The radiotherapy dose was 20 Gy administered to the retrobulbar orbit in ten to 12 fractions over 2 to 3 weeks. Azathioprine treatment was provided for 48 weeks at 100-200 mg per day (dispensed as 50 mg tablets), depending on bodyweight (100 mg for <50 kg, 150 mg 50-79 kg, 200 mg for ≥80 kg). The primary outcomes were a binary composite clinical outcome score and an ophthalmopathy index at 48 weeks, and a clinical activity score at 12 weeks. The primary analysis was based on the intention-to-treat allocation and safety was assessed in all participants. This study is registered with ISRCTN, number 22471573.

FINDINGS

Between Feb 15, 2006, and Oct 3, 2013, 126 patients were recruited and randomly assigned to groups: 31 patients to radiotherapy plus azathioprine, 31 to sham radiotherapy and azathioprine, 32 to radiotherapy and placebo, and 32 to sham radiotherapy and placebo. Outcome data were available for 103 patients (54 for sham radiotherapy vs 49 for radiotherapy and 53 for placebo vs 50 for azathioprine), of whom 84 completed their allocated treatment of radiotherapy or sham radiotherapy and 57 continued to take azathioprine or placebo up to 48 weeks. There was no interaction betweeen azathioprine and radiotherapy (p_interaction=0·86). The adjusted odds ratio (OR_adj) for improvement in the binary clinical composite outcome measure was 2·56 (95% CI 0·98-6·66, p=0·054) for azathioprine and 0·89 (0·36-2·23, p=0·80) for radiotherapy. In a post-hoc analysis of patients who completed their allocated therapy the OR_adj for improvement was 6·83 (1·66-28·1, p=0·008) for azathioprine and 1·32 (0·30-4·84, p=0·67) for radiotherapy. The ophthalmopathy index, clinical activity score, and numbers of adverse events (161 with azathioprine and 156 with radiotherapy) did not differ between treatment groups. In both groups, the most common adverse events were mild infections. No patients died during the study.

INTERPRETATION

In patients receiving oral prednisolone for 24 weeks, radiotherapy did not have added benefit. We also did not find added benefit for addition of azathioprine in the primary analysis; however, our conclusions are limited by the high number of patients who withdrew from treatment. Results of post-hoc analysis of those who completed the assigned treatment suggest improved clinical outcome at 48 weeks with azathioprine treatment.

FUNDING

National Eye Research Centre, Above and Beyond, and Moorfields Eye Charity.

Addition of gemcitabine to paclitaxel, epirubicin, and cyclophosphamide adjuvant chemotherapy for women with early-stage breast cancer (tAnGo): final 10-year follow-up of an open-label, randomised, phase 3 trial

BACKGROUND

The tAnGo trial was designed to investigate the potential role of gemcitabine when added to anthracycline and taxane-containing adjuvant chemotherapy for early breast cancer. When this study was developed, gemcitabine had shown significant activity in metastatic breast cancer, and there was evidence of a favourable interaction with paclitaxel.

METHODS

tAnGo was an international, open-label, randomised, phase 3 superiority trial that enrolled women aged 18 years or older with newly diagnosed, early-stage breast cancer who had a definite indication for chemotherapy, any nodal status, any hormone receptor status, Eastern Cooperative Oncology Group performance status of 0-1, and adequate bone marrow, hepatic, and renal function. Women were recruited from 127 clinical centres and hospitals in the UK and Ireland, and randomly assigned (1:1) to one of two treatment regimens: epirubicin, cyclophosphamide, and paclitaxel (four cycles of 90 mg/m2 intravenously administered epirubicin and 600 mg/m2 intravenously administered cyclophosphamide on day 1 every 3 weeks, followed by four cycles of 175 mg/m2 paclitaxel as a 3 h infusion on day 1 every 3 weeks) or epirubicin, cyclophosphamide, and paclitaxel plus gemcitabine (the same chemotherapy regimen as the other group, with the addition of 1250 mg/m2 gemcitabine to the paclitaxel cycles, administered intravenously as a 0·5 h infusion on days 1 and 8 every 3 weeks). Patients were randomly assigned by a central computerised deterministic minimisation procedure, with stratification by country, age, radiotherapy intent, nodal status, and oestrogen receptor and HER-2 status. The primary endpoint was disease-free survival and the trial aimed to detect 5% differences in 5-year disease-free survival between the treatment groups. Recruitment completed in 2004 and this is the final, intention-to-treat analysis. This trial is registered with EudraCT (2004-002927-41), ISRCTN (51146252), and ClinicalTrials.gov (NCT00039546).

FINDINGS

Between Aug 22, 2001, and Nov 26, 2004, 3152 patients were enrolled and randomly assigned to epirubicin, cyclophosphamide, paclitaxel, and gemcitabine (gemcitabine group; n=1576) or to epirubicin, cyclophosphamide, and paclitaxel (control group; n=1576). 11 patients (six in the gemcitabine group and five in the control group) were ineligible because of pre-existing metastases and were therefore excluded from the analysis. At this protocol-specified final analysis (median follow-up 10 years [IQR 10-10]), 1087 disease-free survival events and 914 deaths had occurred. Disease-free survival did not differ significantly between the treatment groups at 10 years (65% [63-68] in the gemcitabine group vs 65% [62-67] in the control group), and median disease-free survival was not reached (adjusted hazard ratio 0·97 [95% CI 0·86-1·10], p=0·64). Toxicity, dose intensity, and a detailed safety substudy showed both regimens to be safe, deliverable, and tolerable. Grade 3 and 4 toxicities were reported at expected levels in both groups. The most common were neutropenia (527 [34%] of 1565 patients in the gemcitabine group vs 412 [26%] of 1567 in the control group), myalgia and arthralgia (207 [13%] vs 186 [12%]), fatigue (207 [13%] vs 152 [10%]), infection (202 [13%] vs 141 [9%]), vomiting (143 [9%] vs 108 [7%]), and nausea (132 [8%] vs 102 [7%]).

INTERPRETATION

The addition of gemcitabine to anthracycline and taxane-based adjuvant chemotherapy at this dose and schedule confers no therapeutic advantage in terms of disease-free survival in early breast cancer, although it can cause increased toxicity. Therefore, gemcitabine has not been added to standard adjuvant chemotherapy in breast cancer for any subgroup.

FUNDING

Cancer Research UK core funding for Clinical Trials Unit at the University of Birmingham, Eli Lilly, Bristol-Myers Squibb, and Pfizer.

Loading dose ibandronate versus standard oral ibandronate in patients with bone metastases from breast cancer

INTRODUCTION

In this phase II trial, the efficacy and safety of loading-dose I.V. ibandronate in patients with breast cancer with bone metastases were evaluated.

PATIENTS AND METHODS

Thirty-four patients were randomized to receive a loading dose of 12 mg I.V. ibandronate on day 1 then oral ibandronate 50 mg daily (arm A), or standard oral therapy of 50 mg ibandronate daily from day 1 (arm B). The primary end point was percentage change in serum C-terminal crosslinking telopeptide of type I collagen (S-CTX) from baseline by day 5 of study. Secondary/exploratory end points included percentage change in other bone turnover markers (N-terminal cross-linking telopeptides of type I collagen [NTX], procollagen type I N propeptide, bone alkaline phosphatase) and change in average bone pain score.

RESULTS

There was a significantly greater reduction in S-CTX at day 5 in arm A compared with arm B (median difference, 15.82%; P = .005). There was also a significantly greater reduction in urine NTX/creatinine at day 5 (P = .009) and at the end of weeks 1 to 8 (averaged; P = .006). Average bone pain score was lower in arm A at the end of 8 weeks (P = .012). There were no additional adverse events after administration of 12 mg I.V. loading dose of ibandronate.

CONCLUSION

A 12-mg dose of I.V. ibandronate rapidly reduced markers of bone turnover and can be administered without additional toxicity.

P4-16-05: A Randomized Phase 2 Study of a Loading Dose of Ibandronate in Patients with Bone Metastases from Breast Cancer

Bisphosphonates have proven efficacy in reducing skeletal complications in metastatic breast cancer. Potent third generation bisphosphonates are more effective but the dose limiting toxicity is usually renal. Ibandronate is a 3rd generation bisphosphonate available in oral and intravenous form which offers many clinical advantages in ease of administration and lack of renal toxicity. A dose-response effect has been observed between 2mg and 6 mg IV doses and there is a single study suggesting that higher dosing (4 mg IV daily for 3 days) is tolerable and effective. A steady state of oral ibandronate is achieved at 8 days with oral administration but time to response is not known. In trials so far, IV ibandronate 6mgs appears safe. Due to lack of renal toxicity there is potential for further escalation of IV ibandronate. The objective of this study was to establish if an IV loading dose can improve efficacy and time to biochemical response compared to oral standard therapy and to assess the safety of a higher IV dose of ibandronate.

Methods and Patients: This was an open randomised phase II study conducted on patients with bone metastases from breast cancer comparing IV ibandronate 12 mg on day 1 followed by oral ibandronate 50 mgs daily (Arm A) with standard oral therapy of 50 mgs daily from day 1 (Arm B). The primary study end-point was the percentage reduction in serum CTX from baseline by day 5 on study, secondary end- points were the percentage reduction of bone turnover markers including serum CTX from baseline end of week 8 and percentage reduction in urine NTX from baseline to day 5 on study and baseline to end of week 1–8. Bone pain was recorded by Brief Pain Inventory. Patients had metastatic breast cancer with proven bone metastases, no previous treatment with bisphosphonates or other bone directed therapy within 6 months and no change in systemic therapy within a 3 months preceding trial therapy. Sample size of 22 patients in each arm was calculated to give a 90% chance detecting a 20% difference in average percentage reduction between the IV and oral arms.

Results: Seventeen patients were randomised to each study arm. A more rapid change in bone turnover markers was demonstrated in patients recieving the 12 mg loading dose of ibandronate. There was a 15.8% greater reduction of serum CTX in Arm A compared with Arm B at day 5, p=0.005. The percentage reduction of serum PINP at day 5 was also greater in Arm A, p=0.002. Over the 8 week period of study there was no overall significant difference in bone turnover markers. All patients had pain at study entry, median baseline pain severity scores were 3 in study arm and 4 in controls. Average bone pair score remained higher in treatment arm B at the end of 8 weeks. There were no additional adverse side-effects following administration of 12 mg of IV ibandronate and no evidence of additional renal toxicity. Conclusion: A 12 mg dose of IV ibandronate can be safely administered without additional renal toxicity. A rapid reduction in bone turnover markers is demonstrated within 5 days of IV loading dose of ibandronate. Potential exists for dose escalation of ibandronate. The clinical benefit of a more rapid reduction in bone turnover markers is unknown.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-16-05.

tAnGo: a randomised phase III trial of gemcitabine in paclitaxel-containing, epirubicin/cyclophosphamide-based, adjuvant chemotherapy for early breast cancer: a prospective pulmonary, cardiac and hepatic function evaluation

tAnGo is a large randomised trial assessing the addition of gemcitabine(G) to paclitaxel(T), following epirubicin(E) and cyclophosphamide(C) in women with invasive higher risk early breast cancer. To assess the safety and tolerability of adding G, a detailed safety substudy was undertaken. A total of 135 patients had cardiac, pulmonary and hepatic function assessed at (i) randomisation, (ii) mid-chemotherapy, (iii) immediately post-chemotherapy and (iv) 6 months post-chemotherapy. Skin toxicity was assessed during radiotherapy. No differences were detected in FEV₁ or FVC levels between treatment arms or time points. Diffusion capacity (TL_CO) reduced during treatment (P<0.0001), with a significantly lower drop in EC-GT patients (P=0.02). Most of the reduction occurred during EC and recovered by 6-months post treatment. There was no difference in cardiac function between treatment arms. Only 11 patients had echocardiography/MUGA results change from normal to abnormal during treatment, with only five having LVEF<50%. Transient transaminitis occurred in both treatment arms with significantly more in EC-GT patients post-chemotherapy (AST P=0.03, ALT P=0.003), although the majority was low grade. There was no correlation between transaminitis and other toxicities. Both treatment regimens reported temporary reductions in pulmonary functions and transient transaminitis levels. Despite these being greater with EC-GT, both regimens appear well tolerated.

Acute Supraclavicular Skin Toxicity in Patients Undergoing Radiotherapy for Breast Cancer: An Evaluation of the ‘T’-Grip Method of Patient Positioning

AIMS

Supraclavicular fossa (SCF) radiotherapy plays an important part in the adjuvant management of breast cancer but data on acute radiotherapy toxicity are lacking, particularly when differing patient treatment positions are used to allow computed tomography planning or to reduce cardiac doses.

MATERIALS AND METHODS

We evaluated SCF and breast/chest wall acute skin toxicity in a cohort of 92 women with breast cancer, who were planned in a 'T'-grip (n = 72) or 90 degrees-grip (n = 20) position, while 'on treatment' and at 6 weeks. The modified Radiation Therapy Oncology Group (RTOG) criteria were used to score toxicity. Data on age, body mass index, smoking history, type of breast operation, prior chemotherapy, radiation dose, number of fields and field size were recorded and correlated with outcome.

RESULTS

Maximum SCF reaction score was RTOG 2a, with no moist desquamation observed. SCF reactions were less severe compared with chest wall reactions and no worse than breast reactions. There was significant resolution of toxicity at 6 weeks. SCF radiotherapy in 'T'-grip patients was well tolerated and no worse than the 90 degees-grip group. Pain scores and sore throat occurrences were minimal. Univariate and multivariate analyses showed that smoking was associated with worsening SCF toxicity (odds ratio [OR] 2.92; P = 0.045) and delayed healing. Incremental SCF dose worsened toxicity (OR 3.65; P = 0.023). Smoking worsened breast but not chest wall toxicity.

CONCLUSIONS

SCF radiotherapy was at least as well tolerated as breast radiotherapy and better tolerated than chest wall radiotherapy. The 'T'-grip position did not affect toxicity negatively. Smoking and radiation dose affected SCF toxicity.

The new pre-preclinical paradigm: compound optimization in early and late phase drug discovery

The attrition rates of new chemical entities (NCEs) in preclinical and clinical development are staggeringly high. NCEs are abandoned due to insufficient efficacy, safety issues, and economic reasons. Uncovering drug defects that produce these failures as early as possible in drug discovery would be highly effective in lowing the cost and time of developing therapeutically useful drugs. Unfortunately, there is no single factor that can account for these NCE failures in preclinical and clinical development since factors, such as solubility, pKa, absorption, metabolism, formulation, pharmacokinetics, toxicity and efficacy, to name a few, are all interrelated. In addition, there are many problems in scaling-up drug candidates from the laboratory bench scale to the pilot plant scale. To address the problem of attrition rates of NCEs in preclinical and clinical development and drug scale-up issues, pharmaceutical companies need to reorganize their preclinical departments from a traditional linear approach to a parallel approach. In this review, a strategy is put forth to integrate certain aspects of drug metabolism/pharmacokinetics, toxicology functions and process chemistry into drug discovery. Compound optimization in early and late phase drug discovery occurs by relating factors such as physicochemical properties, in vitro absorption, in vitro metabolism, in vivo pharmacokinetics and drug scale-up issues to efficacy optimization. This pre-preclinical paradigm will improve the success rate of drug candidates entering development.

1,3-Diarylcycloalkanopyrazoles and diphenyl hydrazides as selective inhibitors of cyclooxygenase-2

Novel 1,3-diarylcycloalkanopyrazoles 1, and diphenyl hydrazides 2 were identified as selective inhibitors of cyclooxygenase-2. The 1,3-diaryl substitution pattern of the pyrazole ring in 1 differentiates these compounds from most of the known selective COX-2 inhibitors that contain two aryl rings at the adjacent positions on a heterocyclic or a phenyl ring. Similarly, the two phenyl rings in 2 are also separated by three atoms. SAR of both phenyl rings in 1 and 2, and the aliphatic ring in 1 will be discussed.

N-hydroxyurea and hydroxamic acid inhibitors of cyclooxygenase and 5-lipoxygenase

Two series of compounds (1 and 2) having structural features of the dual COX/5-LO inhibitor tepoxalin and the 5-LO inhibitor ABT-761 were prepared. Many of these hybrid compounds are potent COX and 5-LO inhibitors; two compounds (1a and 2t) inhibit eicosanoid biosynthesis in an ex vivo assay.

Design and discovery of RWJ 22108--a novel bronchoselective calcium channel blocker

A series of cyclic sulfone dihydropyridines ranging in sulfone ring size from five to nine membered have been evaluated for calcium antagonist activity. Increasing the sulfone ring size from 5 to 8 membered resulted in a two orders of magnitude in vitro potency increase. Aromatic substitution which favored tracheal effects over aortic effects was found to be 2-NO2 and 2-Cl, 6-F. The ester side chain which was found to maximize in vivo activity was the N-benzyl-N-methyl aminoethyl moiety. Combination of all these structural features resulted in RWJ 22108, a bronchoselective calcium channel blocker which preclinically exhibits an antiasthmatic profile.

Evaluation of the antiinflammatory activity of a dual cyclooxygenase-2 selective/5-lipoxygenase inhibitor, RWJ 63556, in a canine model of inflammation

Sterile perforated polyethylene spheres (wiffle golf balls) were implanted s.c. in beagle dogs. A local inflammatory reaction was elicited within the spheres by injecting carrageenan. Changes in leukocyte count, prostaglandin E2, thromboxane B2 and leukotriene B4 levels were monitored in fluid samples collected over a 24-hr period. Blood samples were also collected at various time points and analyzed for prostaglandin E2 and leukotriene B4 production after ex vivo calcium ionophore treatment. Effects of standard antiinflammatory agents (aspirin, indomethacin, dexamethasone, tenidap and zileuton) and newer cyclooxygenase-2 (COX-2) selective agents (nimesulide, nabumetone and SC-58125) were determined after oral administration. Ex vivo inhibition of cyclooxygenase product synthesis (prostaglandin E2, thromboxane B2) in whole blood was used as an indicator of activity for the constitutive COX-1 isoform, although inhibition of the synthesis of these mediators in the chamber exudate during an inflammatory process is believed to represent COX-2 inhibition. Treatment effects on leukotriene B4 production were also determined both ex vivo in whole blood and in the fluid. All of the compounds tested, except aspirin, inhibited leukocyte infiltration into the fluid exudate. Inhibitors that exert their effects on both isozymes of cyclooxygenase attenuate production of cyclooxygenase metabolites in both the inflammatory exudate and in peripheral blood ex vivo, although COX-2 selective inhibitors only demonstrated activity in the exudate. A 5-lipoxygenase inhibitor (zileuton), a corticosteroid (dexamethasone) and a dual COX-2 selective/5-lipoxygenase inhibitor (RWJ 63556) had similar profiles in that they all inhibited cell infiltration and eicosanoid production in the fluid and also attenuated leukotriene B4 production in both the fluid and blood.

Effects of tepoxalin, a dual inhibitor of cyclooxygenase/5-lipoxygenase, on events associated with NSAID-induced gastrointestinal inflammation

Prostaglandins and thromboxanes are products of arachidonic acid metabolism via the cyclooxygenase (CO) enzyme and are responsible for the pain and swelling common to sites of inflammation. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the production of these substances and are used in the treatment of inflammatory diseases such as arthritis. However, one of the major side-effects of NSAID therapy is gastric ulceration. It is possible that inhibition of prostaglandin production and a related increase in the formation of leukotrienes via the 5-lipoxygenase (5-LO) enzymatic pathway are responsible for attracting inflammatory cells, causing local sites of inflammation and producing ulceration. To determine the effects of 5-LO inhibition on this hypothesis, studies were performed in rats to evaluate the effects of tepoxalin, a dual CO/LO inhibitor on leukotriene B4 levels in gastric mucosa and neutrophil adhesion in mesenteric venules. In rats, chronic oral administration of an NSAID, indomethacin (2 mg/kg daily over 4 days), resulted in 40% mortality, accompanied by intestinal adhesions and perforations when evaluated 24 h after the fourth dose of drug. Additionally, neutrophil adhesion was increased in the mesenteric venules and cell infiltration was evident in the mesenteric interstitium. These gastrointestinal side-effects were inhibited in a separate group of rats administered tepoxalin (20 mg/kg, p.o) 30 min prior to each daily indomethacin treatment. Further studies were performed to determine tepoxalin's effects on early events associated with NSAID-induced gastrointestinal inflammation, including neutrophil adhesion, lipid peroxide generation and LTB4 production. Indomethacin (100 mg/kg, p.o.) produced elevated levels of LTB4 in rat gastric mucosa 90 min after administration. Additionally, neutrophil adhesion in mesenteric venules was increased at this dose and with the administration of another NSAID, naproxen. No generation of lipid peroxides was evident in the gastric mucosa at this timepoint. Tepoxalin (up to 400 mg/kg, p.o.) did not have an effects on gastric mucosal LTB4 generation and lipid peroxide levels. A decrease in neutrophil adhesion was observed at the highest dose. In another study, pretreatment with tepoxalin (ED50=7.5 mg/kg, p.o.) or the selective 5-LO inhibitor zileuton (100 mg/kg, p.o.) prevented the increases in gastric mucosal LTB4 levels and neutrophil adhesion induced by indomethacin (100 mg/kg, p.o.). These data suggest that LO inhibition may play a vital role in the prevention of NSAID-induced gastric inflammation, providing insight into the lack of ulcerogenicity with tepoxalin and new approaches to anti-inflammatory therapy which may prevent gastric side effects.

Cytokine-modulating activity of tepoxalin, a new potential antirheumatic

Tepoxalin is a new dual cyclooxygenase/5-lipoxygenase anti-inflammatory compound currently under clinical investigation. It has been shown to possess anti-inflammatory activity in a variety of animal models and more recently to inhibit IL-2 induced signal transduction. The current study was conducted to evaluate the cytokine modulating activity of tepoxalin and the role of iron in these effects. In human peripheral blood mononuclear cells (PBMC) stimulated with OKT3/PMA, tepoxalin inhibited lymphocyte proliferation with an IC50 of 6 microM. Additionally, it inhibited the production of LTB4 (IC50 = 0.5 microM) and the cytokines IL-2, IL-6 and TNF alpha (IC50 = 10-12 microM). Cytotoxicity was not demonstrated at these concentrations. Add-back experiments with either cytokines (IL-2 or IL-6), LTB4 or conditioned media failed to restore the proliferative response in the presence of tepoxalin. However, the concurrent addition of iron (in the form of ferrous or ferric chloride and other iron salts) reversed the inhibition of proliferation caused by tepoxalin. Tepoxalin also inhibits the activation of NF kappa B, a transcription factor which acts on several cytokine genes. Tepoxalin's effect on NF kappa B is also reversed by the addition of iron salts. These data suggest that the action of tepoxalin to inhibit proliferation in PBMC may be at least in part due to its ability to reduce the amount of available iron resulting in decreased activation of NF kappa B and subsequent inhibition of cytokine production.

Tepoxalin: a dual cyclooxygenase/5-lipoxygenase inhibitor of arachidonic acid metabolism with potent anti-inflammatory activity and a favorable gastrointestinal profile

Tepoxalin [5-(4-chlorophenyl)-N-hydroxy-(4-methoxyphenyl)-N-methyl-1H- pyrazole-3-propanamide] is a potent inhibitor of sheep seminal vesicle cyclooxygenase (CO) (IC50 = 4.6 microM), rat basophilic leukemia cell (RBL-1) lysate CO (IC50 = 2.85 microM) and CO from intact RBL-1 cells (IC50 = 4.2 microM). The compound inhibits the production of thromboxane B2 (TxB2) in Ca++ ionophore A-23187-stimulated human peripheral blood leukocytes (HPBL; IC50 = 0.01 microM) and human whole blood (IC50 = 0.08 microM) and is a potent inhibitor of epinephrine-induced human platelet aggregation (IC50 = 0.045 microM). Tepoxalin inhibits lipoxygenase (LO) in RBL-1 lysates (IC50 = 0.15 microM) and intact RBL-1 cells (IC50 = 1.7 microM) and inhibits the generation of leukotriene B4 (LTB4) in calcium ionophore A-23187-stimulated HPBL (IC50 = 0.07 microM) and human whole blood (IC50 = 1.57 microM). Human platelet 12-LO (IC50 = 3.0 microM) is inhibited, but 15-LO is only weakly so (IC50 = 157 microM). In vivo, tepoxalin, administered orally, demonstrated potent anti-inflammatory activity in the established adjuvant arthritic rat (ED50 = 3.5 mg/kg) and potent analgesic activity in the acetic acid abdominal construction assay in mice (ED50 = 0.45 mg/kg). In an ex vivo whole blood eicosanoid production assay, tepoxalin produces a dose-related inhibition of prostaglandin (PG) and LT production in dogs (PGF2 alpha - ED50 = 0.015 mg/kg; LTB4 - ED50 = 2.37 mg/kg) and adjuvant arthritic rats following oral administration. In adjuvant arthritic rats, tepoxalin is devoid of ulcerogenic activity within its anti-inflammatory therapeutic range (1-33 mg/kg p.o.) and does not exhibit ulcerogenic activity in normal rats at doses lower than 100 mg/kg (UD50 = 173 mg/kg p.o.). Tepoxalin represents a new class of anti-inflammatory drugs which may exhibit less gastrointestinal toxicity and may be efficacious in immunoinflammatory disease states where excessive PG and LT production has been implicated and may offer a significant alternative to nonsteroidal and corticosteroidal anti-inflammatory therapy.

Reticulocyte measurements as a bioassay for erythropoietin

The possibility of using reticulocyte counts in peripheral blood to assay erythropoietic activity of recombinant human erythropoietin (r-HuEPO) was evaluated in normal mice. Mice were injected subcutaneously with r-HuEPO on days 0, 1 and 2 and bled on day 4 for reticulocyte count determinations, using an automated counting system with thiazole orange fluorescent staining and flow cytometric analysis. Reticulocyte counts increased in a dose-dependent fashion upon administration of r-HuEPO. The reticulocyte count was unaffected by asialylated EPO as well as other substances tested (interleukin-1, interleukin-3, dexamethasone, human chorionic gonadotropin). These data demonstrate the usefulness of employing reticulocyte counts as a rapid, specific and reproducible assay for in vivo erythropoietic activity of r-HuEPO.

Experimental antiasthmatic activity of RWJ 22108: a bronchoselective calcium entry blocker

RWJ 22108 (N-benzyl-N-methylaminoethyl 9-(2-chloro-6-fluorophenyl)-2,3,4,5,6,9-hexahydro-7-methyl-1, 1-dioxothiacyclohepteno-[3,2-b]pyridine-8-carboxylate) is a new bronchoselective calcium entry blocker with potential use as an antiasthmatic agent. Previous studies have shown that RWJ 22108 is a potent calcium entry blocker in vitro and demonstrates tissue selectivity for airway smooth muscle over vascular smooth muscle. The current study demonstrates the in vivo activity of RWJ 22108 in several different models of airway obstruction and asthma. RWJ 22108 relaxes preconstricted airways in dogs with little effect on blood pressure when administered by aerosol. In addition, it inhibits airway obstruction induced by antigen, histamine and exogenous leukotriene D4 in guinea pigs. In a conscious sheep model of allergic asthma, aerosol RWJ 22108 inhibits antigen-induced early and late phase airway obstruction and also the cellular infiltration associated with late phase. Total leukotrienes production is decreased in the guinea pig model probably as a result of fewer inflammatory cells infiltrating the lungs as shown in the sheep model of late phase. These data suggest that RWJ 22108 may have pharmacological potential in the clinical management of asthma.

Evaluation of calcium entry blockers in several models of immediate hypersensitivity

Several calcium-entry blockers, i.e., verapamil, nifedipine, flunarizine and diltiazem, were evaluated for their effects in models of immediate hypersensitivity disease. Verapamil, flunarizine and diltiazem were all effective in inhibiting antigen-induced bronchospasm in the guinea pig; however, the effects seen were at relatively high doses compared to the doses known to cause cardiovascular effects. Nifedipine caused no significant inhibition of resistance or compliance changes induced by antigen. Flunarizine, verapamil and diltiazem were ineffective in inhibiting antigen-induced histamine release from rat peritoneal mast cells in vitro. Although these compounds were active inhibitors of 5-D-[5,6,8,9,H,12,14,15-3H(N)]-hydroxy-6,8,11,14-eicosatetraenoic acid production in rat basophilic leukemia-1 cells, only flunarizine and verapamil showed effects on the 5-lipoxygenase enzyme when assayed directly. Also, these compounds were ineffective on SRS-A mediated bronchospasm in vivo. These data suggest that the currently available calcium entry blockers have little potential use in immediate hypersensitivity reactions.

Flunarizine and verapamil: effects on central nervous system and peripheral consequences of cytotoxic hypoxia in rats

Flunarizine is a calcium entry blocking drug possessing antihypoxic activity in animal models of cerebral and peripheral ischemia-anoxia and has clinical usefulness in circulatory disorders of both central and peripheral origin. This report compares the activity of flunarizine and verapamil, another calcium entry blocking drug, on the central nervous system (CNS) and peripheral consequences of cytotoxic hypoxia induced by high and low doses of KCN. The lethal effect of KCN (6 mg/kg, i.p.) in rats was prevented by orally administered flunarizine (ED50 = 12 mg/kg with four-hr pretreatment) but not by verapamil (at oral doses up to 80 mg/kg with one-hr pretreatment). Since the lethal effect of KCN involves failure of respiration at the CNS level, these results suggest that flunarizine protects against the hypoxic effect of the cyanide ion by an action in brain tissue. We found also that the stimulant effect of low intravenous doses (0.5 mg/kg/min) of KCN upon respiration rate was not altered in pentobarbital- and chloralose-anesthetized rats treated with oral doses of flunarizine up to 80 mg/kg (with four hr pretreatment). In contrast, KCN-stimulated respiration rate in pentobarbital anesthetized rats was significantly attenuated by verapamil (20 and 40 mg/kg, p.o. with one hr pretreatment). Since low doses of the cyanide ion render respiration quicker and deeper by an action on chemoreceptive cells in peripheral arteries, the effect of verapamil against the hypoxic effect of KCN is mediated by an action in the periphery. In summary, we have shown that the physiological consequences of cytotoxic hypoxia can be affected by calcium entry blocking drugs having site-specific activities. Based on our results, flunarizine is more effective than verapamil against cellular anoxia involving the CNS.

Smooth muscle contraction as a model to study the mediator role of endogenous lipoxygenase products of arachidonic acid

In the lung, the contraction of smooth muscle, or bronchospasm, is generally caused by an immunologic insult resulting in mast cell degranulation and the release of histamine, slow reacting substances, and other mediators of inflammation (1). Although the immediate response is bronchospasm, continued activation of this sequence of events results in a chronic inflammatory disease. In the uterus, numerous conditions can result in smooth muscle contraction. One major pathophysiological syndrome associated with increased uterine tone and severe rhythmic contraction is primary dysmenorrhea (2). In this disease state, prostaglandins have been shown to play a major role in these contractions (3,4), and inhibitors of cyclooxygenase have proven beneficial in clinical practice (5). Both dysmenorrhea and cervical ripening have been likened to inflammatory reactions due to varying degrees of vasodilation, invasion by inflammatory cells, proliferation of fibroblasts and smooth muscle contraction (6,7). Metabolism of arachidonic acid (AA) via cyclooxygenase to prostaglandins and thromboxanes and via lipoxygenase to hydroxyeicosatetraenoic acids (HETEs) and leukotrienes is an integral part of both the acute and chronic inflammatory reaction in the lung or uterus. The material reviewed here examines the effect of endogenous leukotrienes on both the lung and uterus and suggests that other smooth muscles and pathophysiological states may be more involved with the lipoxygenase pathway of AA metabolism than previously believed.

Involvement of lipoxygenase products in myometrial contractions

Studies with an in situ preparation of guinea pig uterus suggest the possible involvement of the lipoxygenase pathway of arachidonic acid (AA) metabolism in myometrial contractions. Female guinea pigs were sensitized to ovalbumin (OA) on day one of their estrous cycle. On day 14, these pigs were anesthetized and the uterus was cannulated for measuring contractions. OA challenge, with histamine antagonism (methapyrilene) resulted in uterine contractions which significantly raised myometrial tonus, presumably due to AA metabolites. Pretreatment with high doses of indomethacin resulted in only 60% inhibition of the OA induced contraction, suggesting the remaining contraction was due to something other than cyclooxygenase products. In the presence of indomethacin and methapyrilene, the addition of AA to increase available substrate caused increased myometrial tone following antigen challenge. This increase in uterine tone was inhibited in a dose dependent fashion by FPL-55712 demonstrating that leukotrienes can contract the uterus and that antigen challenge may provide a means for studying leukotriene involvement in uterine pathophysiology.

SRS-A mediated bronchospasm by pharmacologic modification of lung anaphylaxis in vivo

Antigen challenge of actively sensitized guinea pigs results in the release of histamine eicosanoids (products of the cyclooxygenase pathway of arachidonic acid metabolism) and slow reducing substance of anaphylaxis (SRS-A). By antagonizing the effects of histamine, serotonin, and acetylcholine, inhibiting the cyclooxygenase pathway and supplying arachidonic acid as substrate, the contribution of SRS-A to anaphylactic bronchospasm can be enhanced, thus allowing suitable quantitation of antagonists. This SRS-A mediated bronchospasm can be inhibited in a dose dependent fashion by FPL55712, a selective antagonist of SRS-A. This system represents an in vivo method capable of detecting compounds which inhibit SRS-A synthesis/release of SRS-A action at the effector organ.

Comparison of the arrhythmogenic effect of myocardial infarction in the cat and dog

Myocardial infarction was produced in dogs and cats by occlusion of the left anterior descending coronary artery. Arrhythmia was present in dogs but not in cats 6 to 48 h after occlusion. The absence of arrhythmia in cats was not due to persistent myocardial depressant effects of anaesthesia administered during surgery. Studies in cats with surgically-induced heart block revealed multiple ventricular pacemakers but no change in average ventricular rate following coronary occlusion. These results suggest that sinus overdrive, although not elevated compared with the dog, is sufficient to suppress arrhythmia in the cat. Further, since small dogs developed significantly less arrhythmia than large dogs, heart size may be an additional factor in explaining the absence of arrhythmia in the cat.

Helium effect on isolated nerve activity

Various gases were administered to isolated frog sciatic nerves in which action potential amplitudes were recorded in sheathed and desheathed preparations. In the sheathed preparation, nitrogen and argon showed significant anesthetic effects while in the desheathed preparation, helium also depressed the action potential amplitude. In the desheathed frog sciatic nerve, helium demonstrates an anesthetic effect similar to 10(-6) M lidocaine suggesting that at long exposure periods helium may demonstrate anesthetic properties.

Cardiovascular and antiarrhythmic effects of carnitine

Thresholds for electrically induced atrial fibrillation were measured in response to IV carnitine. Mean arterial pressure, heart rate, and mean aortic flow rate were also monitored. Carnitine 100 mg/kg resulted in an increase in mean aortic blood flow. The antiarrhythmic effect was much less than with 5 mg/kg quinidine, but after atropinization, 100 mg/kg carnitine was similar in antiarrhythmic effect to quinidine and did not result in the blood pressure depression seen with quinidine.

Effect of helium on membrane resistance

Resistance measurements were made of bimolecular lipid membranes (BLM) according to Mueller and Rudin (10). With the addition of excitability inducing material (EIM), a bacterial protein, the electrical resistance of the BLM was reduced to within biological limits. Frog pericardium was used in the same system as a natural membrane comparison. Exposure of these membranes to air, oxygen and nitrogen resulted in no significant change in the resistance of the bilayers or the pericardium. Exposure to helium and helium 79%-oxygen 21% mixutre resulted in a significant increase in the membrane resistance.