Pipeline Impact of Radiolabeled Compounds in Drug Discovery and Development

The long-lived radionuclides tritium and carbon-14 have been used for many years in pharmaceutical research and development for making key efficacy and toxicological decisions. Early discovery utilizes radiolabels for compound selection through radioligand binding assays and autoradiography. In preclinical safety evaluation, the use of labeled compounds for adsorption, distribution, metabolism, and excretion studies is often preferred for the added detection sensitivity. As the drug substance proceeds to the clinic, human metabolism studies are reliant on the use of labeled materials to fulfill required regulatory applications.

[18F]BTK-1: A Novel Positron Emission Tomography Tracer for Imaging Bruton's Tyrosine Kinase

PURPOSE

Bruton's tyrosine kinase (BTK) is a key component of B cell receptor (BCR) signaling, and as such a critical regulator of cell proliferation and survival. Aberrant BCR signaling is important in the pathogenesis of various B cell malignancies and autoimmune disorders. Here, we describe the development of a novel positron emission tomography (PET) tracer for imaging BTK expression and/or occupancy by small molecule therapeutics.

METHODS

Radiochemistry was carried out by reacting the precursor with [¹⁸F]fluoride on a GE FX-FN TracerLab synthesis module to produce [¹⁸F]BTK-1 with a 6% decay-corrected radiochemical yield, 100 ± 6 GBq/µmol molar activity, and a radiochemical purity of 99%. Following intravenous administration of [¹⁸F]BTK-1 (3.63 ± 0.59 MBq, 0.084 ± 0.05 µg), 60-min dynamic images were acquired in two xenograft models: REC-1, an efficacious mantle cell lymphoma model, and U87MG, a non-efficacious glioblastoma model. Subsequent studies included vehicle, pretreatment (10 min prior to tracer injection), and displacement (30 min post-tracer injection) studies with different reversible BTK inhibitors to examine BTK binding. Human radiation dosimetry was estimated based on PET imaging in healthy rats.

RESULTS

Uptake of [¹⁸F]BTK-1 was significantly higher in BTK expressing REC-1 tumors than non-BTK expressing U87MG tumors. Administration of BTK inhibitors prior to tracer administration blocked [¹⁸F]BTK-1 binding in the REC-1 tumor model consistent with [¹⁸F]BTK-1 binding to BTK. The predicted effective dose in humans was 0.0199 ± 0.0007 mSv/MBq.

CONCLUSION

[¹⁸F]BTK-1 is a promising PET tracer for imaging of BTK, which could provide valuable information for patient selection, drug dose determination, and improving our understanding of BTK biology in humans.

Radiosynthesis of 3 H- and 14 C-labeled Veliparib

Veliparib, a potent PARP inhibitor used against multiple cancerous cells such as metastatic melanoma, breast, non-small cell lung cancer (NSCLC) and prostatic cancer, is required for absorption, distribution, metabolism and excretion (ADME) and environmental toxicology assessments studies. Tritium-labeled Veliparib was prepared via the tritiodebromination using tritium gas (T₂ ) in two steps. [¹⁴ C]Veliparib was achieved through an asymmetric synthetic route in seven radioactive steps starting from [¹⁴ C] (S)-benzyl 2-aminopropanoate.

Machine learning-based FDG PET-CT radiomics for outcome prediction in larynx and hypopharynx squamous cell carcinoma

AIM

To determine whether machine learning-based radiomic feature analysis of baseline integrated 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET) computed tomography (CT) predicts disease progression in patients with locally advanced larynx and hypopharynx squamous cell carcinoma (SCC) receiving (chemo)radiotherapy.

MATERIALS AND METHODS

Patients with larynx and hypopharynx SCC treated with definitive (chemo)radiotherapy at a specialist cancer centre undergoing pre-treatment PET-CT between 2008 and 2017 were included. Tumour segmentation and radiomic analysis was performed using LIFEx software (University of Paris-Saclay, France). Data were assigned into training (80%) and validation (20%) cohorts adhering to TRIPOD guidelines. A random forest classifier was created for four predictive models using features determined by recursive feature elimination: (A) PET, (B) CT, (C) clinical, and (D) combined PET-CT parameters. Model performance was assessed using area under the curve (AUC) receiver operating characteristic (ROC) analysis.

RESULTS

Seventy-two patients (40 hypopharynx 32 larynx tumours) were included, mean age 61 (range 41-77) years, 50 (69%) were men. Forty-five (62.5%) had chemoradiotherapy, 27 (37.5%) had radiotherapy alone. Median follow-up 26 months (range 12-105 months). Twenty-seven (37.5%) patients progressed within 12 months. ROC AUC for models A, B, C, and D were 0.91, 0.94, 0.88, and 0.93 in training and 0.82, 0.72, 0.70, and 0.94 in validation cohorts. Parameters in model D were metabolic tumour volume (MTV), maximum CT value, minimum standardized uptake value (SUVmin), grey-level zone length matrix (GLZLM) small-zone low grey-level emphasis (SZLGE) and histogram kurtosis.

CONCLUSION

FDG PET-CT derived radiomic features are potential predictors of early disease progression in patients with locally advanced larynx and hypopharynx SCC.

Protocol-driven multidetector SPECT/CT: integration of hybrid imaging into the routine workflow of whole-body bone scintigraphy in oncology patients

AIM

To analyse the additional clinical value of protocol-driven and selective use of multidetector single-photon-emission tomography/computed tomography (SPECT/CT) in oncology patients undergoing whole-body bone scintigraphy (BS) and to analyse reporter confidence in diagnosis with and without SPECT/CT.

MATERIALS AND METHODS

During a 2-year period, 2,954 whole-body BS examinations were performed in oncology patients, with 444 (15%) undergoing additional protocol-driven SPECT/CT. Retrospective evaluation of planar BS and SPECT/CT images was performed by two experienced dual-trained nuclear medicine radiologists. The BS and SPECT/CT images were graded blindly using a five-point scale designed to evaluate the likelihood of a lesion being benign or malignant. Interpretation was applied on a per-patient basis.

RESULTS

There was a 74.5% increase in definitive diagnostic classification and a 26.6% reduction in equivocal findings with SPECT/CT when compared to BS alone (p<0001). Of cases initially classified as "probably benign" on BS, 5.1% (10/193) were reclassified to "probably malignant" (1%) or "malignant" (4.1%) using the SPECT/CT data. The highest impact in reporter confidence was seen with SPECT/CT in the interpretation of lesions within the pelvis (34%), ribs (23%), lumbar spine (22%), and thoracic spine (21%).

CONCLUSION

Protocol-driven, selective use of SPECT/CT imaging to augment planar BS reduces equivocal findings and improves reporter confidence whilst minimising the impact on patient and reporting workflows.

Radiological-pathological correlation of the British Thyroid Association ultrasound classification of thyroid nodules: a real-world validation study

AIM

To evaluate the real-world performance of the British Thyroid Association (BTA) U classification, specifically focusing on radiology-pathology correlation and to glean learning points.

METHODS AND MATERIALS

Adults undergoing a neck ultrasound for thyroid nodules were reviewed over a period of 1-year. Data including demographics, nodule characteristics, BTA grading, and cytology/histopathology were retrieved with a minimum 24-month follow-up.

RESULTS

Of 1,225 graded nodules in 964 patients, cytology and/or histology were available for 300 (24%). 57 cancers were detected. Of 24 (2%) U5 nodules, 14 were malignant, of 51 (4%) U4, 22 were malignant, of 256 (21%) U3, 20 were malignant, and from 894 (73%) U2 nodules, one cancer was discovered. BTA U grading with fine-needle aspiration (FNA)/core biopsy achieved 96.5% sensitivity, 93.7% specificity, and 93.9% accuracy compared to excision. There was no association between nodule size and rate of malignancy.

CONCLUSION

This is the first study to validate the use of the BTA U-grading system in UK clinical practice. The BTA U-grading system is a robust and reliable method of evaluating the risk of malignancy in thyroid nodules with a high negative predictive value. Key learning points gleaned from the study were accurate assessment of nodule echogenicity, careful evaluation of solid-cystic nodules, optimising ultrasound technique, and the low-risk nature of U3 nodules.

Metabolism and Disposition of a Novel B-Cell Lymphoma-2 Inhibitor Venetoclax in Humans and Characterization of Its Unusual Metabolites

Venetoclax (ABT-199), a B-cell lymphoma-2 (Bcl-2) protein inhibitor, is currently in clinical development for the treatment of hematologic malignancies. We characterized the absorption, metabolism, and excretion of venetoclax in humans. After a single oral dose of [¹⁴C]venetoclax to healthy volunteers, the recovery of total radioactive dose was 100%, with feces being the major route of elimination of the administered dose, whereas urinary excretion was minimal (<0.1%). The extent of absorption was estimated to be at least 65%. Venetoclax was primarily cleared by hepatic metabolism (∼66% of the administered dose). ∼33% of the administered dose was recovered as the parent drug and its nitro reduction metabolite M30 [2-((1H-pyrrolo[2,3-b]pyridin-5-yl)oxy)-N-((3-amino-4-(((tetrahydro-2H-pyran-4-yl)methyl)amino)phenyl)sulfonyl)-4-(4-((4'-chloro-5,5-dimethyl-3,4,5,6-tetrahydro-[1,1'-biphenyl]-2-yl)methyl)piperazin-1-yl)benzamide] (13%) in feces. Biotransformation of venetoclax in humans primarily involves enzymatic oxidation on the dimethyl cyclohexenyl moiety, followed by sulfation and/or nitro reduction. Nitro reduction metabolites were likely formed by gut bacteria. Unchanged venetoclax was the major drug-related material in circulation, representing 72.8% of total plasma radioactivity. M27 (oxidation at the 6 position of cyclohexenyl ring followed by cyclization at the α-carbon of piperazine ring; 4-[(10aR,11aS)-7-(4-chlorophenyl)-9,9-dimethyl-1,3,4,6,8,10,10a,11a-octahydropyrazino[2,1-b][1,3]benzoxazin-2-yl]-N-[3-nitro-4-(tetrahydropyran-4-ylmethylamino)phenyl]sulfonyl-2-(1H-pyrrolo[2,3-b]pyridin-5-yloxy)benzamide) was identified as a major metabolite, representing 12% of total drug-related material. M27 was primarily formed by cytochrome P450 isoform 3A4 (CYP3A4). Steady-state plasma concentrations of M27 in human and preclinical species used for safety testing suggested that M27 is a disproportionate human metabolite. M27 is not expected to have clinically relevant on- or off-target pharmacologic activities.

PAMAM Dendrimers as Quantized Building Blocks for Novel Nanostructures

The desire to synthesize soft supramolecular structures with size scales similar to biological systems has led to work in assembly of polymeric nanomaterials. Recent advances in the isolation of generationally homogenous poly(amidoamine) (PAMAM) dendrimer enables their use as quantized building blocks. Here, we report their assembly into precise nanoclusters. In this work, click-functional ligands are stochastically conjugated to monomeric generation 5 PAMAM dendrimer and separated via reverse-phase HPLC to isolate dendrimers with precise numbers of click ligands per dendrimer particle. The click-ligand/dendrimer conjugates are then employed as modular building blocks for the synthesis of defined nanostructures. Complimentary click chemistry employing dendrimers with 1, 2, 3, or 4 ring-strained cyclooctyne ligands and dendrimers with 1 azide ligand were utilized to prepare megamer structures containing 2 to 5 ~30,000 kDa monomer units as characterized by mass spectrometry, size exclusion chromatography, and reverse-phase liquid chromatography. The resulting structures are flexible with masses ranging from 60,000 to 150,000 kDa, and are soluble in water, methanol, and dimethylsulfoxide.

Airway dysfunction in nasal polyposis: a spectrum of asthmatic disease?

BACKGROUND

Chronic rhinosinusitis with nasal polyposis (CRSwNP) represents an interesting model to investigate the existence of a non-allergic unified airway. The factors associated with airway dysfunction in CRSwNP are not fully understood.

OBJECTIVE

To assess the impact of nasal disease on lower airway dysfunction in CRSwNP.

METHODS

Fifty-seven patients with CRSwNP underwent spirometry, nasal endoscopy, exhaled nitric oxide, methacholine bronchial challenge, blood sampling for total IgE, eosinophil count and radioallergosorbent testing (NCT00788749). Three phenotypic groups were identified: 'asthma group' (asthma diagnosis); 'inflammatory group' [no asthma diagnosis, but elevated fractionated exhaled nitric oxide (FE(NO)) and/or bronchial-hyperreactivity (BHR)]; and 'non-inflammatory group' (no asthma diagnosis, no BHR and normal FE(NO)). Group comparisons, univariate and multivariate analyses were performed to examine associations with airway dysfunction.

RESULTS

FEV(1) and FEF(25-75%) were reduced in asthma, but there was no difference between the non-asthmatic groups. Total IgE and eosinophils were elevated in asthma vs. the non-inflammatory group, but there was no difference for asthma vs. inflammatory groups. BHR was the only significant predictor of FEV(1) (P<0.001). For FEF(25-75), BHR and eosinophil count were independent predictors (P<0.001 and P=0.04). Nasal outcomes were not predictors of spirometry.

CONCLUSION AND CLINICAL RELEVANCE

In CRSwNP there is asymptomatic airway dysfunction suggestive of an asthmatic phenotype. Impairment of lung function is significantly associated with BHR and eosinophilia but not parameters of nasal disease suggesting that severity of airway dysfunction relates to the spectrum of asthma rather than rhinosinusitis. Lower airway dysfunction is common in CRSwNP but does not correlate to the severity of nasal disease. Signs and symptoms of asthma should be sought and treated in CRSwNP.

Supervised step-down of inhaled corticosteroids in the community--an observational study

INTRODUCTION

Current asthma guidelines recommend step-down of inhaled corticosteroids (ICS) to the minimum dose required for control of symptoms.

AIM

To determine if supervised step-down of (ICS) in the community has any effect on asthmatic inflammation.

METHODS

119 Community based asthmatics underwent progressive step-down of therapy until they became unstable or reached an (ICS) dose of ≤200 μg beclomethasone dipropionate (BDP) or equivalent. Once unstable, participants stepped back up to the last stable dose of ICS. Exhaled nitric oxide (NO) and mannitol challenge were performed at the start and end of step-down. Asthma Quality of Life Questionnaire (AQLQ) and spirometry were recorded at each step-down visit.

RESULTS

The median (interquartile range) BDP equivalent dose was significantly higher pre vs. post step-down: 400 μg (400-800) and 250 μg (200-400) per day respectively (P < 0.05). Examination of change in PD(10) in individual patients revealed that 34% had an improvement (>+1 dd), 47% had no change (±-1 dd), and 19% had a worsening (<-1 dd). The geometric mean fold ratio in NO for pre vs. post was 0.96 (95% CI 0.87 to 1.06, P = 0.43). Mean (SEM) values for FEV(1) were 86.2% (1.51) vs. 84.5% (1.46) (P = 0.04). There was a significant improvement in AQLQ.

CONCLUSIONS

We have demonstrated that a significant reduction in ICS dose may be achieved in a community setting without any worsening of airways inflammation or lung function, and with an associated improvement quality of life in the majority of patients. This apparent disconnect may reflect enhanced adherence due to supervision of step-down.

Steroid sparing effects of intranasal corticosteroids in asthma and allergic rhinitis

BACKGROUND

Treating allergic rhinitis may have a downstream anti-inflammatory effect on the lower airways. We conducted a dose ranging study in asthma and persistent allergic rhinitis to evaluate if intranasal corticosteroids exhibit a sparing effect on the dose of inhaled corticosteroid.

METHODS

Twenty five participants were randomized to receive two weeks of 100 microg/day (Low dose) or 500 microg/day (High dose) of inhaled fluticasone propionate both with intranasal placebo; or inhaled fluticasone 100 microg/day with intranasal fluticasone 200 microg/day (Combined) in a double-blind cross-over fashion.

RESULTS

Low dose fluticasone produced a shift of 1.20 doubling-dilutions (95% CI, 0.63, 1.77); Combined fluticasone, 1.79 doubling-dilutions (95% CI, 0.77, 2.80) and high dose fluticasone, 2.01 doubling-dilutions (95% CI, 1.42, 2.61) in methacholine PC(20) from respective baselines. There was a significant difference between high and low doses: 0.82 doubling dilutions (95%CI, 0.12, 1.50) but not between combined and low dose 0.58 doubling dilutions (95% CI, -0.78, 1.95). Combined treatment alone produced improvements in peak nasal inspiratory flow (P < 0.001), rhinitis quality of life (P = 0.004) and nasal NO (P = 0.01); reduced blood eosinophil count (P = 0.03), and serum eosinophil cationic protein (P = 0.02). All treatments significantly improved tidal NO, FEV(1) and asthma quality of life.

CONCLUSIONS

High-dose fluticasone was superior to low dose fluticasone for methacholine PC20, demonstrating room for further improvement. Combined treatment was not significantly different from low dose fluticasone and we could not demonstrate a steroid sparing effect on methacholine PC20. Combined treatment alone produced improvements in upper airway outcomes and suppressed systemic inflammation but not adrenal function.

Disconnect between standardized field-based testing and mannitol challenge in Scottish elite swimmers

BACKGROUND

Elite swimmers have high rates of rhinoconjunctivitis and exercise-induced bronchoconstriction. Moreover, exposure to chlorine and chlorine metabolites is known to induce bronchial hyper-reactivity.

OBJECTIVE

To assess the early and late effects of chlorine and exercise on the unified airway of elite swimmers, and to compare the response to mannitol and field-based exercise challenge.

METHODS

The Scottish national squad underwent exhaled tidal (FE(NO)) and nasal (N(NO)) nitric oxide measurement, peak nasal inspiratory flow (PNIF), and forced expiratory volume in 1 s before, immediately after, and 4-6 h post-swimming. A sport-specific exercise test was carried out during an intensive lactate set (8 min at >/=80% maximum hear rate). All swimmers underwent mannitol challenge, and completed a health questionnaire.

RESULTS

N=61 swimmers were assessed: 8/59 (14%) of swimmers had a positive mannitol challenge. Nine out of 57 (16%) of swimmers had a positive exercise test. Only one swimmer was positive to both. Swimmers with a positive mannitol had a significantly higher baseline FE(NO) (37.3 vs. 18.0 p.p.b., P=0.03) than those with a positive exercise challenge. A significant decrease in FE(NO) was observed pre vs. immediate and delayed post-chlorine exposure: mean (95% CI) 18.7 (15.9-22.0) p.p.b. vs. 15.9 (13.3-19.1) p.p.b. (P<0.01), and 13.9 (11.5-16.7) p.p.b. (P<0.01), respectively. There were no significant differences in N(NO.) Mean PNIF increased from 142.4 L/min (5.8) at baseline to 162.6 L/min (6.3) immediately post-exposure (P<0.01). Delayed post-exposure PNIF was not significantly different from pre-exposure.

CONCLUSIONS

No association was found between mannitol and standardized field-based testing in elite swimmers. Mannitol was associated with a high baseline FE(NO); however, exercise/chlorine challenge was not. Thus, mannitol may identify swimmers with a 'traditional' inflammatory asthmatic phenotype, while field-based exercise/chlorine challenge may identify a swimmer-specific bronchoconstrictor response. A sustained fall in FE(NO) following chlorine exposure suggests that a non-cellular, perhaps neurogenic, response may be involved in this group of athletes.

Effects of chlorine and exercise on the unified airway in adolescent elite Scottish swimmers

BACKGROUND

Chlorine metabolites and high training load may produce exercise-induced bronchospasm (EIB) in elite swimmers. The aim of this study was to assess the combined effects of chlorine and exercise on the unified airway of adolescent elite swimmers.

METHODS

The Scottish Midlands District squad were assessed during an indoor pool session at the National Swimming Academy. Athletes trained at least 8 h per week. Subjects underwent tidal (T(NO)) and nasal (N(NO)) exhaled NO and peak nasal inspiratory flow (PNIF) pre and post a 2 h session. A physiological exercise challenge assessed EIB in n = 36 swimmers (>10% fall in forced expiratory volume in 1 s (FEV(1))).

RESULTS

Combined and free chlorine levels (mg/l) were 1.66 and 0.3 respectively. n = 36 swimmers (mean age 13.3 years) were assessed: n = 8 (22%) had known asthma; n = 13 (36%) had a positive physiological challenge; 18 (50%) complained of symptoms suggestive of EIB. n = 10/28 (36%) who did not have asthma were found to have a positive exercise challenge. There was no significant association between reported exercise symptoms and positive exercise test. There was no significant change in T(NO) or N(NO) for pre vs postexposure, irrespective of asthma diagnosis or AHR. n = 15 (42%) swimmers complained of worsening nasal symptoms postexposure, but only n = 7 (14%) had a demonstrable fall in PNIF (mean 33 l/min). No significant association was found between PNIF and symptoms.

CONCLUSIONS

Combined exposure to chlorine and exercise did not affect surrogate markers of inflammation in the unified airway. There was a high prevalence of undiagnosed EIB.

The minimal clinically important difference in allergic rhinitis

BACKGROUND

When presented with results from clinical measurements or research findings, clinicians must first make an interpretation of their importance, not only in statistical terms, but also the 'clinical importance' given the size of the change observed. To do this, they require an understanding of the relationship between their outcome measures, and the patient's perception of change. The minimal clinically important difference (MCID) illustrates this relationship by calculating the smallest change in a given outcome that is meaningful to a patient. There are few reports of calculated MCIDs in the Rhinology literature.

OBJECTIVE

To calculate MCIDs for common subjective and objective outcome measures in allergic rhinitis (AR).

METHODS

Nine randomized, blinded, placebo-controlled clinical trials in intermittent and persistent AR (pooled subjects, n=204) were analysed using anchor- and distribution-based approaches, applying regression and meta-analysis techniques.

RESULTS

MCIDs were obtained for the Mini Rhinoconjunctivitis Quality of Life Questionnaire: 0.4 units, peak nasal inspiratory flow: 5 L/min and total nasal symptoms score: 0.55 units. Nasal NO measurement changes had no correlation with patient perceptions of benefit.

CONCLUSION

Estimates of MCIDs were obtained for common subjective and objective rhinological outcomes. MCIDs can and should be applied by physicians interpreting research findings, as well as researchers reporting their findings. We can then be confident that our changes in practice will be of perceptible benefit to the patient.

Effect of levocetirizine on nasal provocation testing with adenosine monophosphate compared with allergen challenge in allergic rhinitis

BACKGROUND

End-organ hyperreactivity is an important feature of the allergic airway. There are no data directly comparing the responsiveness to treatment of different nasal provocation tests (NPT).

OBJECTIVE

We compared the effect of levocetirizine on nasal adenosine 5'-monophosphate (AMP) with specific allergen challenge in patients with intermittent and persistent allergic rhinitis (AR).

METHODS

Patients with AR were randomized in double-blind cross-over fashion to receive single doses of levocetirizine 5 mg or identical placebo, with nasal challenge performed 12 h after dosing. Sixteen participants completed per protocol. Nasal AMP or allergen challenge was conducted on separate days with 1- and 2-week washout periods in between, respectively. Measurements of peak nasal inspiratory flow (PNIF) were made over 60 min after each challenge. The primary end-point was the provocative concentration of AMP or allergen causing a 20% drop in the PNIF (PC(20)).

RESULTS

The time-profile for PNIF recovery [area under the 60 min time-response curve as % PNIF change (min)] were significantly attenuated for AMP challenge, as mean difference [95% confidence interval (CI)]: 11.57 (3.87, 19.25), P=0.005 and for allergen challenge: 17.82 (0.11, 35.53), P=0.04. A highly significant correlation was shown between methods for the area under the curve: (R=0.86, P<0.001). A statistically significant correlation was also seen for the PC(20): (R=0.94, P<0.001). PC(20) improvement amounted to a 1.26 (95% CI 0.16, 2.35) and 0.16 (95% CI -0.41, 0.73) doubling-dilution shifts for allergen and AMP challenges, respectively. Bland-Altman plots confirmed good agreement between methods.

CONCLUSION

A high correlation and statistical agreement has been demonstrated between AMP and allergen challenge for all outcome measures. In particular, the recovery profile after NPT is a sensitive and discriminatory measure of anti-allergic treatment.

Effect of aliskiren, an oral direct renin inhibitor, on the pharmacokinetics and pharmacodynamics of a single dose of acenocoumarol in healthy volunteers

OBJECTIVE

Aliskiren is a direct renin inhibitor approved for the treatment of hypertension. This study investigated the effects of aliskiren on the pharmacokinetics and pharmacodynamics of a single dose of acenocoumarol in healthy volunteers.

METHODS

This two-sequence, two-period, randomized, double-blind crossover study recruited 18 healthy subjects (ages 18-45) to receive either aliskiren 300 mg or placebo once daily on days 1-10 of each treatment period and a single dose of acenocoumarol 10 mg on day 8. Treatment periods were separated by a 10-day washout. Blood samples were taken frequently for determination of steady-state plasma concentrations of aliskiren (LC-MS/MS) and of R(+)- and S(-)-acenocoumarol (HPLC-UV), prothrombin time (PT) and international normalized ratio (INR).

RESULTS

Co-administration with aliskiren had no effect on exposure to R(+)-acenocoumarol. Geometric mean ratios (GMR; aliskiren:placebo co-administration) for R(+)-acenocoumarol AUC(0-t) and C(max) were 1.08 and 1.04, respectively, with 90% CI within the range 0.80-1.25. Co-administration of aliskiren resulted in a 19% increase in S(-)-acenocoumarol AUC(0-t) (GMR 1.19; 90% CI 0.92, 1.54) and a 9% increase in C(max) (GMR 1.09; 90% CI 0.88, 1.34). The anticoagulant effect of acenocoumarol was not affected by co-administration of aliskiren. Geometric mean ratios were 1.01 for all pharmacodynamic parameters (AUC(PT), PT(max), AUC(INR) and INR(max)), with 90% CI within the range 0.97-1.05.

CONCLUSION

Aliskiren has no clinically relevant effect on the pharmacokinetics or pharmacodynamic effects of a single dose of acenocoumarol in healthy volunteers, hence no dosage adjustment of acenocoumarol is likely to be required during co-administration with aliskiren.

Stridor: an unusual presentation of lateral medullary syndrome

We report an unusual case of lateral medullary syndrome which presented with symptoms of acute upper airway obstruction mimicking angioneurotic oedema. Although dysphonia and dysphagia are common symptoms of lateral medullary syndrome, we have found no other reports of this condition presenting as stridor. This case highlights the importance of maintaining a high index of suspicion for central causes of common otolaryngological symptoms in the absence of local signs.

Lack of pharmacokinetic interactions of aliskiren, a novel direct renin inhibitor for the treatment of hypertension, with the antihypertensives amlodipine, valsartan, hydrochlorothiazide (HCTZ) and ramipril in healthy volunteers

Aliskiren is a novel, orally active direct renin inhibitor that lowers blood pressure alone and in combination with existing antihypertensive agents. As aliskiren does not affect cytochrome P450 enzyme activities, is minimally metabolised, and is not extensively protein bound, the potential for drug interactions is predicted to be low. Four open-label studies investigated the pharmacokinetic interactions between aliskiren 300 mg and the antihypertensive drugs amlodipine 10 mg (n = 18), valsartan 320 mg (n = 18), hydrochlorothiazide 25 mg (HCTZ, n = 22) and ramipril 10 mg (n = 17) in healthy subjects. In each study, subjects received multiple once-daily doses of aliskiren and the test antihypertensive drug alone or in combination in two dosing periods separated by a drug-free washout period. Plasma concentrations of drugs were determined by liquid chromatography and mass spectrometry methods. At steady state, relatively small changes in exposure to aliskiren were observed when aliskiren was co-administered with amlodipine (AUC(tau) increased by 29%, p = 0.032), ramipril (C(max,ss) increased by 31%, p = 0.043), valsartan (AUC(tau) decreased by 26%, p = 0.002) and HCTZ (C(max,ss) decreased by 22%, p = 0.039). Co-administration with aliskiren resulted in small changes in exposure to ramipril (AUC(tau) increased by 22%, p = 0.002), valsartan (AUC(tau) decreased by 14%, p = 0.062) and HCTZ (AUC(tau) decreased by 10% and C(max,ss) by 26%, both p < 0.001). All other changes in pharmacokinetic parameters were also small, and not statistically significant. None of the observed pharmacokinetic changes was considered clinically relevant. Aliskiren inhibited plasma renin activity (PRA) and also prevented the reactive rise in PRA induced by valsartan. The most commonly reported adverse events were headache, dizziness and gastrointestinal symptoms (all mild in severity), which were similar in frequency during antihypertensive drug treatment alone and in combination with aliskiren except for an increase in dizziness during treatment with the combination of aliskiren and HCTZ. In conclusion, aliskiren shows no clinically relevant pharmacokinetic interactions and is generally well tolerated when administered in combination with amlodipine, valsartan, HCTZ or ramipril.

Chronic lymphocytic leukaemia, synchronous small cell carcinoma and squamous neoplasia of the urinary bladder in a paraplegic man following long-term phenoxybenzamine therapy

STUDY DESIGN

A case report.

OBJECTIVE

To raise awareness among spinal cord clinicians of the possible carcinogenic effect of phenoxybenzamine and of the rare occurrence of small cell carcinoma in the neuropathic bladder.

SETTING

Regional Spinal Injuries Centre and District General Hospital, Southport, Merseyside, United Kingdom.

CASE REPORT

A 28-year-old man sustained a fracture dislocation of L-1 with consequent paraplegia (ASIA impairment scale A). Phenoxybenzamine treatment enabled his indwelling catheter to be discarded in favour of a penile sheath, but it caused unacceptable dizziness and was stopped after 7 years. After 20 years, he developed chronic lymphocytic leukaemia, which was treated with chlorambucil and fludarabine. After 2 years, investigation of bilateral hydronephrosis revealed a primary small cell carcinoma of the bladder with coexistent squamous dysplasia. Uraemia supervened and, declining active treatment, the patient died 3 weeks after diagnosis.

CONCLUSION

Phenoxybenzamine, a known carcinogen in rodents, is likely also to be carcinogenic in humans, and patients with spinal cord injury who have received the drug for any significant period of time, need close follow-up to allow early detection of cancer. Phenoxybenzamine should not be prescribed on a long-term basis, and should instead be replaced with a selective alpha-blocker.

Evaluation of the pharmacokinetic interaction between fluvastatin XL and cyclosporine in renal transplant recipients

OBJECTIVE

To assess the pharmacokinetic interaction between cyclosporine and extended-release fluvastatin (fluvastatin XL), 80 mg for 7 days, in stable renal transplant recipients.

METHODS

This was a single-center, open-label study. 17 renal transplant recipients received their standard cyclosporine therapy (Days 1 - 9) plus a once-daily single oral dose of fluvastatin XL, 80 mg (Days 2 - 8). Blood samples were collected and cyclosporine (whole blood) and fluvastatin (plasma) concentrations determined by radioimmunoassay and HPLC fluorescence detection, respectively. Pharmacokinetic parameters were calculated using non-compartment analysis and fluvastatin results were compared with historical controls.

RESULTS

Treatment with fluvastatin XL, 80 mg for 7 days, had no significant effect on either the AUC0-12 (3,644 ng x h/ml in the absence of fluvastatin vs. 3,534 ng x h/ml in the presence of fluvastatin) or the Cmax of cyclosporine (983 ng/ml in the absence of fluvastatin vs. 945 ng/ml in the presence of fluvastatin). Co-administration of fluvastatin XL also had no effect on the tmax, t1/2 or apparent clearance (CL/F) of cyclosporine in renal transplant patients. The AUC and Cmax for fluvastatin XL in the presence of cyclosporine (AUC0-24 1,192 ng. x h/ml, Cmax 271 ng/ml) were approximately 2-fold higher compared with historical data for fluvastatin XL alone in healthy volunteers (AUC0-24 630 ng x h/ml, Cmax 102 ng/ml) but lower than the historical data for fluvastatin IR, 40 mg b.i.d. alone in healthy volunteers (AUC0-24 1,340 ng x h/ml, Cmax 443 ng/ml). Tmax, t1/2 and trough levels of fluvastatin in the presence of cyclosporine were also similar to the historical controls. Concomitant administration of cyclosporine and fluvastatin XL was well tolerated by renal transplant recipients.

CONCLUSIONS

Fluvastatin XL, 80 mg, and cyclosporine do not show clinically relevant pharmacokinetic interactions.

Telementoring in Endocrine Surgery: Preliminary Indian Experience

Telemedicine is starting to play an important role in the health field in India. In this case report we describe the successful use of telementoring to remove a parathyroid tumor in a patient with residual hyperparathyroidism after two previous unsuccessful attempts in tumor excision. A 21-yr-old patient crippled with advanced hyperparathyroidism was taken up for third-time exploration at Amrita Institute of Medical Sciences (AIMS), Kochi, with guidance from the Sanjay Gandhi Postgraduate Institute of Medical Sciences (SGPGIMS), Lucknow, using telemedicine technology. These two centers are located 2,500 km apart, and telementoring from the more experienced endocrine surgeons at SGPGIMS resulted in successful tumor localization and removal. For this session both the institutions were provided with a dedicated 512 Kbps very small aperture terminal (VSAT) link and two-way video-audio connectivity. Even though two previous explorations were unsuccessful, with the help of telemedicine technology the same surgeon was successful in locating and removing the tumor. The video and audio quality was of good enough quality for the expert at SGPGIMS to guide the team at AIMS satisfactorily. The patient benefited since he did not have to travel to a far-off specialized center for surgery. This case report testifies to the usefulness of telemedicine in the field of surgery, especially in developing countries, which have few medical experts in certain specialized areas.

Pharmacokinetic interactions of the oral renin inhibitor aliskiren with lovastatin, atenolol, celecoxib and cimetidine

OBJECTIVE

Aliskiren is the first in a new class of orally effective renin inhibitors for the treatment of hypertension. This study investigated the interaction profile of aliskiren, which is of clinical importance because hypertensive patients often require concomitant drug therapy for associated comorbidities.

METHODS

Four separate studies investigated the pharmacokinetic interaction between single oral doses of aliskiren and lovastatin, atenolol, celecoxib or cimetidine, respectively. All studies involved healthy male volunteers aged 18-45 years. In 3 studies, subjects (n = 15 in each study) received single doses of aliskiren 150 mg alone, the test drug alone (lovastatin 40 mg, atenolol 100 mg or celecoxib 200 mg), or both drugs in combination, according to a 3-period crossover design. In the cimetidine study (n = 12), aliskiren 150 mg was administered alone or concomitantly with cimetidine 800 mg according to a two-period crossover design. Plasma concentrations of aliskiren and test drugs were determined by liquid chromatography and mass spectrometry methods. Pharmacokinetic parameters were derived from these data.

RESULTS

Mean AUC and t1/2 for aliskiren were not significantly changed by lovastatin, atenolol or celecoxib (< 10% difference between treatments). Aliskiren mean Cmax was not affected by either lovastatin or atenolol, although a non-significant 36% increase was observed with celecoxib. Modest, non-significant increases in aliskiren systemic availability followed coadministration with cimetidine (aliskiren mean AUC, Cmax and t1/2 increased by 17%, 19% and 15%, respectively). Aliskiren coadministration had no significant effect on the disposition of lovastatin, atenolol or celecoxib.

CONCLUSIONS

Overall, single doses of aliskiren showed no evidence of clinically important pharmacokinetic interactions with lovastatin, atenolol, celecoxib or cimetidine.

Pseudomonas sepsis with Noma: an association?

We report here a 2.5-year-old male child with community-acquired Pseudomonal sepsis showing the characteristic lesions of ecthyma gangrenosum. The child had development of gangrenous changes of the nose and face - the 'cancrum oris' or 'Noma'. We highlight the possible association of Pseudomonas sepsis and Noma, with malnutrition playing a central role in causing both the diseases.

Two case reports of cervical spinal cord injury in football (soccer) players

STUDY DESIGN

Two case reports of male football players who sustained injury to cervical spinal cord as a direct result of the sport.

OBJECTIVE

To raise the awareness that playing football (soccer), a very popular sport, may cause injury to the cervical spinal cord with dire consequences, albeit rarely.

SETTING

North West Regional Spinal Injuries Centre, Southport, UK.

CASE REPORT

We report two male football players, who sustained injury to the cervical spine and developed tetraplegia as a direct result of the sport. Case 1: A 21-year-old football player was tackled from behind while running with the football, he lost his balance and landed on his head resulting in burst fracture dislocation of C5/C6 associated with immediate onset of complete tetraplegia (ASIA-A). Case 2: A 24-year-old football player collided, head first, with his own team goalkeeper, causing a hyperextension of neck. He developed motor complete tetraplegia at C5 level, with some sensation sparing below the level of injury (ASIA-B).

CONCLUSION

Injury to the cervical spinal cord is known to occur in some team contact sports such as rugby and American football. Over time the laws and the preparation of the athletes for these games have been changed in order to minimize the neck injuries. What might not be appreciated is that playing football (soccer), a very popular sport worldwide, may cause injury to cervical spinal cord with dire consequences.