Tumour cell retention of rucaparib, sustained PARP inhibition and efficacy of weekly as well as daily schedules

Background:

Poly(ADP-ribose) polymerase-1 (PARP) inhibitors (PARPi) exploit tumour-specific defects in homologous recombination DNA repair and continuous dosing is most efficacious. Early clinical trial data with rucaparib suggested that it caused sustained PARP inhibition. Here we investigate the mechanism of this durable inhibition and potential exploitation.

Methods:

Uptake and retention of rucaparib and persistence of PARP inhibition were determined by radiochemical and immunological assays in human cancer cell lines. The pharmacokinetics and pharmacodynamics of rucaparib were determined in tumour-bearing mice and the efficacy of different schedules of rucaparib was determined in mice bearing homologous recombination DNA repair-defective tumours.

Results:

Rucaparib accumulation is carrier mediated (Km=8.4±1.2 μM, Vmax=469±22 pmol per 10⁶ cells per 10 min), reaching steady-state levels >10 times higher than the extracellular concentration within 30 min. Rucaparib is retained in cells and inhibits PARP ⩾50% for ⩾72 h days after a 30-min pulse of 400 nM. In Capan-1 tumour-bearing mice rucaparib accumulated and was retained in the tumours, and PARP was inhibited for 7 days following a single dose of 10 mg kg⁻¹ i.p or 150 mg kg⁻¹ p.o. by 70% and 90%, respectively. Weekly dosing of 150 mg kg⁻¹ p.o once a week was as effective as 10 mg kg⁻¹ i.p daily for five days every week for 6 weeks in delaying Capan-1 tumour growth.

Conclusions:

Rucaparib accumulates and is retained in tumour cells and inhibits PARP for long periods such that weekly schedules have equivalent anticancer activity to daily dosing in a pre-clinical model, suggesting that clinical evaluation of alternative schedules of rucaparib should be considered.

MEDITERRANEAN DIET AND MAGNETIC RESONANCE IMAGING-ASSESSED BRAIN ATROPHY IN COGNITIVELY NORMAL INDIVIDUALS AT RISK FOR ALZHEIMER’S DISEASE

OBJECTIVES: Epidemiological evidence linking diet, one of the most important modifiable environmental factors, and risk of Alzheimer’s disease (AD) is rapidly increasing. Several studies have shown that higher adherence to a Mediterranean diet (MeDi) is associated with reduced risk of AD. This study examines the associations between high vs. lower adherence to a MeDi and structural MRI-based brain atrophy in key regions for AD in cognitively normal (NL) individuals with and without risk factors for AD. DESIGN: Cross-sectional study. SETTING: Manhattan (broader area). PARTICIPANTS: Fifty-two NL individuals (age 54+12 y, 70% women) with complete dietary information and cross-sectional, 3D T1-weighted MRI scans were examined. MEASUREMENTS: Subjects were dichotomized into those showing higher vs. lower adherences to the MeDi using published protocols. Estimates of cortical thickness for entorhinal cortex (EC), inferior parietal lobe, middle temporal gyrus, orbitofrontal cortex (OFC) and posterior cingulate cortex (PCC) were obtained by use of automated segmentation tools (FreeSurfer). Multivariate general linear models and linear regressions assessed the associations of MeDi with MRI measures. RESULTS: Of the 52 participants, 20 (39%) showed higher MeDi adherence (MeDi+) and 32 (61%) showed lower adherence (MeDi-). Groups were comparable for clinical, neuropsychological measures, presence of a family history of AD (FH), and frequency of Apolipoprotein E (APOE) ε4 genotype. With and without controlling for age and total intracranial volume, MeDi+ subjects showed greater thickness of AD-vulnerable ROIs as compared to MeDi- subjects (Wilk’s Lambda p=0.026). Group differences were most pronounced in OFC (p=0.001), EC (p=0.03) and PCC (p=0.04) of the left hemisphere. Adjusting for gender, education, FH, APOE status, BMI, insulin resistance scores and presence of hypertension did not attenuate the relationship. CONCLUSION: NL individuals showing lower adherence to the MeDi had cortical thinning in the same brain regions as clinical AD patients compared to those showing higher adherence. These data indicate that the MeDi may have a protective effect against tissue loss, and suggest that dietary interventions may play a role in the prevention of AD

Quantitative neuropathology associated with chronic manganese exposure in South African mine workers

Manganese (Mn) is a common neurotoxicant associated with a clinical syndrome that includes signs and symptoms referable to the basal ganglia. Despite many advances in understanding the pathophysiology of Mn neurotoxicity in humans, with molecular and structural imaging techniques, only a few case reports describe the associated pathological findings, and all are in symptomatic subjects exposed to relatively high-level Mn. We performed an exploratory, neurohistopathological study to investigate the changes in the corpus striatum (caudate nucleus, putamen, and globus pallidus) associated with chronic low-level Mn exposure in South African Mn mine workers. Immunohistochemical techniques were used to quantify cell density of neuronal and glial components of the corpus striatum in eight South African Mn mine workers without clinical evidence of a movement disorder and eight age-race-gender matched, non-Mn mine workers. There was higher mean microglia density in Mn mine workers than non-Mn mine workers in the globus pallidus external and internal segments [GPe: 1.33 and 0.87 cells per HPF, respectively (p=0.064); GPi: 1.37 and 0.99 cells per HPF, respectively (p=0.250)]. The number of years worked in the Mn mines was significantly correlated with microglial density in the GPi (Spearman's rho 0.886; p=0.019). The ratio of astrocytes to microglia in each brain region was lower in the Mn mine workers than the non-Mn mine workers in the caudate (7.80 and 14.68; p=0.025), putamen (7.35 and 11.11; p=0.117), GPe (10.60 and 16.10; p=0.091) and GPi (9.56 and 12.42; p=0.376). Future studies incorporating more detailed occupational exposures in a larger sample of Mn mine workers will be needed to demonstrate an etiologic relationship between Mn exposure and these pathological findings.

Study of the use of antidepressants for depression in dementia: the HTA-SADD trial--a multicentre, randomised, double-blind, placebo-controlled trial of the clinical effectiveness and cost-effectiveness of sertraline and mirtazapine

OBJECTIVE

Depression is common in dementia, causing considerable distress and other negative impacts. Treating it is a clinical priority, but the evidence base is sparse and equivocal. This trial aimed to determine clinical effectiveness of sertraline and mirtazapine in reducing depression 13 weeks post randomisation compared with placebo.

DESIGN

Multicentre, parallel-group, double-blind placebo-controlled randomised controlled trial of the clinical effectiveness of sertraline and mirtazapine with 13- and 39-week follow-up.

SETTING

Nine English old-age psychiatry services.

PARTICIPANTS

A pragmatic trial. Eligibility: probable or possible Alzheimer's disease (AD), depression (4+ weeks) and Cornell Scale for Depression in Dementia (CSDD) score of 8+.

EXCLUSIONS

clinically too critical (e.g. suicide risk); contraindication to medication; taking antidepressants; in another trial; and having no carer.

INTERVENTIONS

(1) Sertraline; (2) mirtazapine; and (3) placebo, all with normal care. Target doses: 150 mg of sertraline or 45 mg of mirtazapine daily.

MAIN OUTCOME MEASURES

OUTCOME

CSDD score. Randomisation: Allocated 1 : 1 : 1 through Trials Unit, independently of trial team. Stratified block randomisation by centre, with randomly varying block sizes; computer-generated randomisation. Blinding: Double blind: medication and placebo identical for each antidepressant. Referring clinicians, research workers, participants and pharmacies were blind. Statisticians blind until analyses completed.

RESULTS

Numbers randomised: 326 participants randomised (111 placebo, 107 sertraline and 108 mirtazapine).

OUTCOME

Differences in CSDD at 13 weeks from an adjusted linear-mixed model: mean difference (95% CI) placebo-sertraline 1.17 (-0.23 to 2.78; p = 0.102); placebo-mirtazapine 0.01 (-1.37 to 1.38; p = 0.991); and mirtazapine-sertraline 1.16 (-0.27 to 2.60; p = 0.112).

HARMS

Placebo group had fewer adverse reactions (29/111, 26%) than sertraline (46/107, 43%) or mirtazapine (44/108, 41%; p = 0.017); 39-week mortality equal, five deaths in each group.

CONCLUSIONS

This is a trial with negative findings but important clinical implications. The data suggest that the antidepressants tested, given with normal care, are not clinically effective (compared with placebo) for clinically significant depression in AD. This implies a need to change current practice of antidepressants being the first-line treatment of depression in AD. From the data generated we formulated the following recommendations for future work. (1) The secondary analyses presented here suggest that there would be value in carrying out a placebo-controlled trial of the clinical effectiveness and cost-effectiveness of mirtazapine in the management of Behavioural and Psychological Symptoms of Dementia. (2) A conclusion from this study is that it remains both ethical and essential for trials of new medication for depression in dementia to have a placebo arm. (3) Further research is required to evaluate the impact that treatments for depression in people with dementia can have on their carers not only in terms of any impacts on their quality of life, but also the time they spend care-giving. (4) There is a need for research into alternative biological and psychological therapies for depression in dementia. These could include evaluations of new classes of antidepressants (such as venlafaxine) or antidementia medication (e.g. cholinesterase inhibitors). (5) Research is needed to investigate the natural history of depression in dementia in the community when patients are not referred to secondary care services. (6) Further work is needed to investigate the cost modelling results in this rich data set, investigating carer burden and possible moderators to the treatment effects. (7) There is scope for reanalysis of the primary outcome in terms of carer and participant CSDD results.

Silicosis at autopsy in platinum mine workers

BACKGROUND

South Africa is the largest producer of platinum group metals in the world. Platinum is found in the Bushveld Complex in the north-east of the country. This volcanic intrusion contains many other minerals, including crystalline silica. Little is known about the health risks in the platinum mining industry.

AIMS

To explore the potential for platinum mine workers to develop silicosis.

METHODS

Autopsies are performed at the National Institute for Occupational Health, for compensation purposes. Platinum mine workers, who had worked for more than a year and had silicosis and/or fibrotic nodules in the lymph nodes, were identified from the autopsy database. An exhaustive search of other available data sources was undertaken to exclude exposure to silica dust in the gold mining industry.

RESULTS

Eighty-five of 3863 (2.2%) platinum mine workers employed for more than a year had silicosis at autopsy; an additional 490 (12.7%) had fibrotic nodules in the lymph nodes. After reviewing all data sources, five mine workers with silicosis and 25 with fibrotic nodules in the lymph nodes fulfilled the study inclusion criteria.

CONCLUSIONS

This case series supports the suggestion that there is a risk of silica exposure in platinum mine workers, a hypothesis supported by the few silica dust measurements taken in the platinum mines. The mining companies should be cognisant of this risk. The recording of comprehensive work histories and the routine measurement of silica dust levels should be enforced to enable risk of disease to be quantified in future studies.

Compensation for environmental asbestos-related diseases in South Africa: a neglected issue

Background

Environmentally acquired asbestos-related diseases (ARDs) are of concern globally. In South Africa, there is widespread contamination of the environment due to historical asbestos mining operations that were poorly regulated. Although the law makes provision for the compensation of occupationally acquired ARDs, compensation for environmentally acquired ARDs is only available through the Asbestos Relief Trust (ART) and Kgalagadi Relief Trust, both of which are administered by the ART. This study assessed ARDs and compensation outcomes of environmental claims submitted to the Trusts.

Methods

The personal details, medical diagnoses, and exposure information of all environmental claims considered by the Trusts from their inception in 2003 to April 2010 were used to calculate the numbers and proportions of ARDs and compensation awards.

Results

There were 146 environmental claimants of whom 35 (23.9%) had fibrotic pleural disease, 1 (0.7%) had lung cancer, and 77 (52.7%) had malignant mesothelioma. 53 (36.3%) claimants were compensated: 20 with fibrotic pleural disease and 33 with mesothelioma. Of the 93 (63.7%) claimants who were not compensated, 33 had no ARDs, 18 had fibrotic pleural disease, 1 had lung cancer, and 44 had mesothelioma. In addition to having ARDs, those that were compensated had qualifying domestic (33; 62.2%) or neighbourhood (20; 37.8%) exposures to asbestos. Most of the claimants who were not compensated had ARDs but their exposures did not meet the Trusts’ exposure criteria.

Conclusions

This study demonstrates the environmental impact of asbestos mining on the burden of ARDs. Mesothelioma was the most common disease diagnosed, but most cases were not compensated. This highlights that there is little redress for individuals with environmentally acquired ARDs in South Africa. To stop this ARD epidemic, there is a need for the rehabilitation of abandoned asbestos mines and the environment. These issues may not be unique to South Africa as many countries continue to mine and use asbestos.

Quantifying errors in the estimation of tuberculosis mortality in a population of South African miners

BACKGROUND

All-cause mortality, based on national tuberculosis programme (NTP) register deaths, may under- or overestimate tuberculosis (TB) specific mortality in the population.

OBJECTIVE

To assess the factors influencing this measurement in a single large population with high TB prevalence and mortality.

METHODS

Routinely collected data on TB cases and treatment outcomes were linked to population data from a cohort of South African miners from 1995 to 2008. Vital status and cause of death were determined from multiple sources, including the TB programme, death register and autopsy.

RESULTS

The TB mortality rate, based on 430 deaths on the TB register, was 192/100,000 person-years (py). Many of these deaths (57%) were not caused by TB, and 483 TB deaths were identified outside the programme. Overall, there were 674 TB-specific deaths; the TB-specific mortality rate was 302/100,000 py. These deaths included 191 (28%) on the TB register, 23 (3%) among defaulters/transfers, 153 (23%) after anti-tuberculosis treatment and 307 (46%) in men who had never been on the programme.

CONCLUSIONS

This study highlights methodological issues in estimating TB mortality. In this population, a method using the product of TB incidence and case fatality consistently underestimated TB mortality. Accurate estimates of TB-specific mortality are crucial for the proper evaluation of TB control programmes.

Lung fibrosis in deceased HIV-infected patients with Pneumocystis pneumonia

Background. Pneumocystis pneumonia (PcP) is one of the most common opportunistic infections found in patients with HIV. The prognosis if ventilation is required is poor, with mortality of 36 - 80%. Although more recent studies have shown improved survival, our experience has been that close to 100% of such patients die, and we therefore decided to investigate further. Methods. All patients with confirmed or suspected PcP who died owing to respiratory failure were eligible for the study. Where consent was obtained, trucut lung biopsies were performed post mortem, stored in formalin and sent for histopathological assessment. Results. Twelve adequate lung biopsies were obtained from 1 July 2008 to 28 February 2011 – 3 from men and 9 from women. The mean age was 34.7 years (range 24 - 46), and the mean admission CD4 count was 20.8 (range 1 - 68) cells/μl and median 18.5 cells/μl. All specimens demonstrated typical PcP histopathology; in addition, 9 showed significant interstitial fibrosis. Three had co-infection with cytomegalovirus (CMV), two of which had fibrosis present. There was no evidence of TB or other fungal infections. Conclusion. The high mortality seen in this cohort of PcP patients was due to intractable respiratory failure from interstitial lung fibrosis. whereas the differential includes ventilator induced lung injury, drug resistance or co-infections, we suggest that this is part of the disease progression in certain individuals. Further studies are required to identify interventions that could modify this process and improve outcomes in patients with PcP who require mechanical ventilation. S Afr J HIV Med 2012;13(2):64-67.