CD20 antigen imaging with ¹²⁴I-rituximab PET/CT in patients with rheumatoid arthritis

INTRODUCTION

Visualization of the CD20-antigen expression could provide a tool to localize sites of inflammation and could be of additive value in the diagnosis, and subsequently, in the treatment follow-up of patients with rheumatoid arthritis. In this study, an anti-CD20 monoclonal antibody, rituximab (Mabthera®), was radiolabeled with ¹²⁴Iodine. We report the first results of I¹²⁴-rituximab PET/CT in patients with rheumatoid arthritis.

METHODS

Eligible patients received 50 MBq ¹²⁴I-rituximab. Wholebody PET/CT imaging was performed at 10 min, 24 h, 48 h and 72-96 h post injection. Images were evaluated primarily on a visual basis and were correlated with disease activity as determined by physical examination and clinical measures.

RESULTS

Joints with visually detectable targeting of ¹²⁴I-rituximab were observed in 4 out of 5 evaluable patients. Only the images at 24 h and later showed accumulation in joints, indicating that the visualized signal represented active targeting of rituximab to the CD20 antigen. Several images showed CD20 positive B-cell infiltration in joints which were clinically normal, while a few clinically diagnosed arthritis localizations were not visualized. This discrepancy suggests that infiltration of CD20 positive B-cells in synovium is a phenomenon that is at least partially independent of clinical inflammation. The level of uptake in joints was generally low, representing less than 0.5% of the injected dose.

CONCLUSION

We have shown the feasibility of CD20 antigen imaging using ¹²⁴I-rituximab in patients with rheumatoid arthritis. Further research is needed to elucidate the clinical significance of demonstrated B-cell infiltration in rheumatic joints.

The pharmacokinetics of ¹²⁴I-rituximab in patients with rheumatoid arthritis

Rheumatoid arthritis is a destructive inflammatory joint disorder. Pre- and mature B-cells, characterized by CD20 antigen expression, play an important role in the inflammatory process. Rituximab, a chimeric monoclonal antibody against the CD20 antigen, has been approved since 2006 for the treatment of patients with rheumatoid arthritis. However, not all patients benefit from this treatment. Persistent activity of the disease has been reported despite treatment with rituximab. Imaging of radiolabeled rituximab can be used to monitor the biodistribution of rituximab, and potentially to predict the efficacy of the treatment. In this study, rituximab was radiolabeled with ¹²⁴Iodine for positron emission tomography (PET) imaging. The aim of this study was to investigate the pharmacokinetics and biodistribution of ¹²⁴I-rituximab in patients with rheumatoid arthritis, to establish the optimal procedure for PET imaging. Eligible patients received 50 MBq ¹²⁴I-rituximab, corresponding to approximately 1.5 mg rituximab. Wholebody PET/CT imaging was performed at 10 min, 24 hrs, and 48 hrs post injection. The total body activity, radioactivity in whole blood, and rituximab serum levels were determined. ¹²⁴I-rituximab has favorable pharmacokinetics for targeting of (pathological) B cells and imaging over several days, but only after pre-treatment with unlabeled rituximab. In addition, protection of the thyroid is recommended to prevent uptake of released ¹²⁴I.

Pharmacokinetics of rituximab in patients with CD20 positive B-cell malignancies

BACKGROUND

In this study, we investigated the pharmacokinetics of rituximab in patients with CD20 positive non-Hodgkin lymphoma, to get more insight into the factors that influence the pharmacokinetics of rituximab. This may aid to understand variability of treatment outcome, in patients with a CD20 positive malignancy treated with rituximab.

METHODS

In this study, patients with a CD20 positive B-cell malignancy who were treated with rituximab containing regimens were included. Induction treatment schedules consisted of a combination of rituximab with chemotherapy for 4-8 cycles. Maintenance treatment consisted of a 2 or 3-monthly dose of 375 mg/m2 rituximab intravenously for 2 years. On the day of the treatment with rituximab, preinfusion blood samples were taken. Also, after the end of treatment, selected blood samples were taken. Rituximab levels were measured with a validated enzyme-linked immunosorbent assay (ELISA). An antigen binding assay was applied for determination of human-antibodies against chimeric-antibodies (HACAs).

RESULTS

Eight patients were on induction therapy. Rituximab levels of one patient on induction therapy remained very low after the first course. This patient had a chronic lymphoid leukemia with circulating tumor cells and a high tumor burden. Apart from one patient with mantle cell lymphoma, all patients on induction therapy had a complete response. Five patients were on maintenance therapy. Trough levels of 4 patients on three-monthly schedule maintenance therapy remained constant, with a median concentration of 6 mu g/mL (range 0.5-11.7 microg/mL). One patient had a relapse during his maintenance treatment. The elimination half-life at steady state of rituximab in all patients was estimated to be 19.2 (+/- 15.2%) days with a between-subject variability of 54%, indicating wide variability. Possible pharmacokinetic-pharmacodynamic relationship was observed as rituximab levels of the non-responders remained low compared to the rituximab levels of the responders. For all patients, concentration of HACAs remained below the quantification limit.

SUMMARY/CONCLUSION

Considerable inter-individual variability of rituximab levels was observed. Although the patient population was small, the results support the need for more research into the pharmacokinetics and factors that might influence the pharmacokinetic-pharmacodynamic relationships of rituximab in patients with non-Hodgkin lymphoma.

Erythrocytic pyruvate kinase deficiency and AB blood types in Australian Abyssinian and Somali cats

OBJECTIVE

To determine the frequency of the mutant pyruvate kinase (PK) allele, haematological parameters and AB blood types of Abyssinian and Somali cats in Australia.

DESIGN

Complete blood cell and reticulocyte counts, DNA PK mutation testing and blood typing were performed in all cats.

RESULTS

A total of 60 cats (36 Abyssinians, 24 Somalis) were included (37 females, 23 males). For the mutant PK allele, three female Somalis were homozygous (affected, 5%), 17 cats were heterozygous (carrier, 28%) and 40 cats tested negative (normal, 67%). Pedigree analysis revealed common ancestry of affected and many carrier cats. Of affected cats, two had regenerative anaemias and all had reticulocytosis (range 64-390 x 10(9)/L; P < 0.001 compared with normal or carrier cats). The only consistent historical sign was lethargy. One affected cat was euthanased 18 months after testing, because of anaemia, neutropenia, anorexia and weight loss. The mutant allele frequency was 0.19 overall (0.29 in Somalis, 0.13 in Abyssinians). All cats had blood type A. The commercial blood typing card method incorrectly identified 12 cats as having type AB blood.

CONCLUSIONS

The frequency of the mutant PK allele is high in Australia. Screening for PK deficiency is indicated before mating and in individual cats of these breeds, even in the absence of anaemia and especially when there is reticulocytosis. Although all cats in the present study had blood type A, blood type B is common in these breeds worldwide. Retyping of any AB typed cats by a laboratory technique is recommended.

Repaglinide induced acute hepototoxicity

Repaglinide is considered a safe drug; adverse events are mild to moderate which includes hypoglycemia, headache, nausea, vomiting, diarrhea and dyspepsia as similar to sulphonylureas. This case report describes a rare side effect of repaglinide. In rare cases, elevated liver enzymes have been noted. We report a case of acute hepatotoxicity in a 78-year-old woman who developed acute hepatotoxicity while taking repaglinide.

Repaglinide induced Acute Hepatotoxicity

Repaglinide is considered a safe drug; adverse events are mild to moderate which includes hypoglycemia, headache, nausea, vomiting, diarrhea and dyspepsia as similar to sulphonylureas. This case report describes a rare side effect of repaglinide. In rare cases, elevated liver enzymes have been noted. We report a case of acute hepatotoxicity in a 78 year old woman who developed acute hepatotoxicity while taking repaglinide.Key Words: hepatotoxicity, hypoglycemia, repaglinide,

Low-dose, time-resolved, contrast-enhanced 3D MR angiography in cardiac and vascular diseases: correlation to high spatial resolution 3D contrast-enhanced MRA

AIM

To evaluate the effectiveness of low-dose, contrast-enhanced, time-resolved, three-dimensional (3D) magnetic resonance (MR) angiography (TR-MRA) in the assessment of various cardiac and vascular diseases, and to compare the results with high-resolution contrast-enhanced MRA (CE-MRA).

MATERIALS AND METHODS

Thirty consecutive patients underwent contrast-enhanced 3D TR-MRA and high spatial resolution 3D CE-MRA for evaluation of cardiac and thoracic vascular diseases at 1.5 T, and neurovascular, abdominal and peripheral vascular diseases at 3T. Gadolinium-based contrast medium was administered at a constant dose of 5 ml for TR-MRA, and 20 ml (lower extremity 30 ml) for CE-MRA. Two readers evaluated image quality using a four-point scale (from 0=excellent to 3=non-diagnostic), artefacts and findings on both datasets. Interobserver variability was tested with kappa coefficient.

RESULTS

The overall image quality for TR-MRA was in the diagnostic range (median 0, range 0-1; k=0.74). Readers demonstrated important additional dynamic information on TR-MRA in 28 of 30 patients (k=0.84). Confident evaluation of organ perfusion (n=23), arteriovenous malformation/fistula flow patterns (n=7), exclusion of intra-cardiac shunts (n=6), and assessment of stent and conduit patency (n=5) were performed by both readers using TR-MRA. Readers demonstrated fine vascular details with higher confidence in 10 patients on CE-MRA. Using CE-MRA, Reader 1 and 2 depicted anatomical details in 6 and 5 patients, respectively, only on CE-MRA.

CONCLUSION

Low-dose TR-MRA yields rapid and important functional and anatomical information in patients with cardiac and vascular diseases. Due to limited spatial resolution, TR-MRA is inferior to CE-MRA in demonstrating fine vascular details.

A randomized trial comparing hormone replacement therapy (HRT) and HRT plus calcitriol in the treatment of postmenopausal osteoporosis with vertebral fractures: benefit of the combination on total body and hip density

We report a prospective, randomized, multicenter, open-label 2-year trial of 81 postmenopausal women aged 53-79 years with at least one minimal-trauma vertebral fracture (VF) and low (T-score below - 2) lumbar bone mineral density (BMD). Group HRT received piperazine estrone sulfate (PES) 0.625 - 1.25 mg/d +/- medroxyprogesterone acetate (MPA) 2.5 - 5 mg/d; group HRT/D received HRT plus calcitriol 0.25 microg bd. All with a baseline dietary calcium (Ca) of < 1 g/ d received Ca carbonate 0.6 g nocte. Final data were on 66 - 70 patients. On HRT/D, significant (P < 0.001) BMD increases from baseline by DXA were at total body - head, trochanter, Ward's, total hip, intertrochanter and femoral shaft (% group mean delta 4.2, 6.1, 9.3, 3.7, 3.3 and 3.3%, respectively). On HRT, at these 6 sites, significant deltaS were restricted to the trochanter and Wards. Significant advantages of HRT/D over HRT were in BMD of total body (- head), total hip and trochanter (all P = 0.01). The differences in mean delta at these sites were 1.3, 2.6 and 3.9%. At the following, both groups improved significantly -lumbar spine (AP and lateral), forearm shaft and ultradistal tibia/fibula. The weightbearing, site - specific benefits of the combination associated with significant suppression of parathyroid hormone-suggest a beneficial effect on cortical bone. Suppression of bone turnover was significantly greater on HRT/D (serum osteocalcin P = 0.024 and urinary hydroxyproline/creatinine ratio P = 0.035). There was no significant difference in the number of patients who developed fresh VFs during the trial (HRT 8/36, 22%; HRT/D 4/34, 12% - intention to treat); likewise in the number who developed incident nonvertebral fractures. This is the first study comparing the 2 treatments in a fracture population. The results indicate a significant benefit of calcitriol combined with HRT on total body BMD and on BMD at the hip, the major site of osteoporotic fracture.

Hepatocyte targeting with Gd-EOB-DTPA: potential application for gene therapy

RATIONALE AND OBJECTIVES

To evaluate the suitability of the liver-specific MRI contrast agent Gd-EOB-DTPA as a nonviral vector for gene therapy of hepatocellular carcinoma.

METHODS

Specific uptake of Gd-EOB-DTPA was quantified by relaxometry in rat cultured hepatocytes and the hepatoma cells HepG2 and Huh7. Nonviral vectors for gene transfer were synthesized by coupling Gd-EOB-DTPA to polyethyleneimine or polylysine as DNA condensing agents, and their efficiency was studied using beta-galactosidase (lacZ) as the reporter gene.

RESULTS

Gd-EOB-DTPA was specifically taken up by rat cultured hepatocytes (4.32 vs. 1.08 mmol/L in nonhepatocyte control cells) but not by the hepatoma cells; this uptake was concentration-dependently inhibited by Bromsulphtalein. Polycation linkages were achieved with yields of 0.9 Gd-EOB-DTPA molecule per polyethyleneimine molecule and 10 Gd-EOB-DTPA molecules per polylysine molecule. Incubating the cells with plasmids containing lacZ reporter gene and polyethyleneimine-Gd-EOB-DTPA resulted in a few blue (transfected) cells, whereas no blue cells were observed on incubation with polylysine-Gd-EOB-DTPA.

CONCLUSIONS

Gd-EOB-DTPA is taken up by normal hepatocytes but not by HepG2 and Huh7 cells, probably because of the lack of the organic anion transporter in these hepatoma cells. The Gd-EOB-DTPA polycation conjugates, such as polyethyleneimine-Gd-EOB-DTPA, could serve as transfer vectors of interest for gene targeting imagery at the early stage of hepatocarcinogenesis. However, the transfer efficiency of such conjugates is low and requires improvement.

Strain differences in the expression of corticotropin-releasing hormone immunoreactivity in nerves that supply the spleen and thymus

The existence of nerve fibers containing corticotropin-releasing hormone (CRH) immunoreactivity in primary and secondary lymphoid organs from three strains of young adult male rats was examined. Spleens and thymuses from Fischer 344 (F344), Sprague-Dawley (SD) and Lewis (LEW) rats were prepared for immunocytochemistry using antisera directed against CRH. In F344 and SD rats, we were unable to demonstrate CRH-immunoreactive nerves in either the thymus or the spleen. Despite the lack of CRH-containing nerves, CRH immunoreactivity was present in pleotropic cells in the septum, cortex and medulla of the thymus, and in the red and white pulp of spleens from F344 and SD rats. In contrast, CRH+ nerves were found in thymuses and spleens from LEW rats. CRH+ nerves coursed in the interlobular septa, capsule, cortex and medulla of the LEW rat thymus. Large CRH-immunoreactive nerve bundles were present in the hilar region of the LEW rat spleen, and individual CRH+ fibers coursed in the capsule, trabeculae, red pulp, venous sinuses and marginal zone of the white pulp of the spleen. These findings indicate strain differences in neurotransmitter-specific nerves that innervate the rat spleen and thymus under basal conditions.

Model-free sib-pair linkage analysis: combining full-sib and half-sib pairs

When sampling full-sibs for linkage studies, half-sibs are often available. Not only are half-sibs convenient to sample, but they can sometimes offer greater power than full-sibs. We propose a method to combine the information from full-sibs and half-sibs into a single test for linkage. This method is based on the Haseman and Elston [1972] method of regressing the squared trait-difference for a pair of sibs (either full- or half-sibs) on the estimated proportion of alleles shared identical by descent. To approximate the distribution of the test statistic, we propose a correction factor that considers the correlation among sibs, and demonstrate by simulations that this approximation works well in many situations, although there are some conditions for which the statistic can have an inflated Type-I error rate. The main appeal of our proposed method is the speed at which it can be computed, offering a rapid way to perform genome-wide linkage screens.

Threshold of toxicological concern for chemical substances present in the diet: a practical tool for assessing the need for toxicity testing

The de minimis concept acknowledges a human exposure threshold value for chemicals below which there is no significant risk to human health. It is the underlying principle for the US Food and Drug Administration (FDA) regulation on substances used in food-contact articles. Further to this, the principle of Threshold of Toxicological Concern (TTC) has been developed and is now used by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in their evaluations. Establishing an accepted TTC would benefit consumers, industry and regulators, since it would preclude extensive toxicity evaluations when human intakes are below such threshold, and direct considerable time and cost resources towards testing substances with the highest potential risk to human health. It was questioned, however, whether specific endpoints that may potentially give rise to low-dose effects would be covered by such threshold. In this review, the possibility of defining a TTC for chemical substances present in the diet was examined for general toxicity endpoints (including carcinogenicity), as well as for specific endpoints, namely neurotoxicity and developmental neurotoxicity, immunotoxicity and developmental toxicity. For each of these endpoints, a database of specific no-observed-effect levels (NOELs) was compiled by screening oral toxicity studies. The substances recorded in each specific database were selected on the basis of their demonstrated adverse effects. For the neurotoxicity and developmental neurotoxicity databases, it was intended to cover all classes of compounds reported to have either a demonstrated neurotoxic or developmentally neurotoxic effect, or at least, on a biochemical or pharmacological basis were considered to have a potential for displaying such effects. For the immunotoxicity endpoint, it was ensured that only immunotoxicants were included in the database by selecting most of the substances from the Luster et al. database, provided that they satisfied the criteria for immunotoxicity defined by Luster. For the developmental toxicity database, substances were selected from the Munro et al. database that contained the lowest NOELs retrieved from the literature for more than 600 compounds. After screening these, substances showing any effect which could point to developmental toxicity as broadly defined by the US were recorded in the database. Additionally, endocrine toxicity and allergenicity were addressed as two separate cases, using different approaches and methodology. The distributions of NOELs for the neurotoxicity, developmental neurotoxicity and developmental toxicity endpoints were compared with the distribution of NOELs for non-specific carcinogenic endpoints. As the immunotoxicity database was too limited to draw such a distribution of immune NOELs, the immunotoxicity endpoint was evaluated by comparing immune NOELs (or LOELs-lowest-observed-effect levels-when NOELs were not available) with non-immune NOELs (or LOELs), in order to compare the sensitivity of this endpoint with non-specific endpoints. A different methodology was adopted for the evaluation of the endocrine toxicity endpoint since data currently available do not permit the establishment of a clear causal link between endocrine active chemicals and adverse effects in humans. Therefore, this endpoint was analysed by estimating the human exposure to oestrogenic environmental chemicals and evaluating their potential impact on human health, based on their contribution to the overall exposure, and their estrogenic potency relative to endogenous hormones. The allergenicity endpoint was not analysed as such. It was addressed in a separate section because this issue is not relevant to the overall population but rather to subsets of susceptible individuals, and allergic risks are usually controlled by other means (i.e. labelling) than the Threshold of Toxicological Concern approach. (ABSTRACT TRUNCATED)

Accuracy and clinical impact of mediastinal lymph node staging with FDG-PET imaging in potentially resectable lung cancer

To determine the sensitivity, specificity, and accuracy of staging mediastinal nodal disease in potentially resectable lung cancer using fluorodeoxyglucose-positron emission tomography (FDG-PET), computed tomography (CT), or both and compare these results to surgical staging. We also assessed whether PET scanning results changed clinical management. From 1992 to 1997, 50 patients underwent CT, and PET scanning before or close to the time of surgical staging. Sensitivity, specificity, accuracy, and predictive values were then calculated based on pathology results. A retrospective review of the records was performed to determine how PET results affected clinical treatment decisions. Forty-seven of 50 patients had non-small-cell lung cancer. The prevalence of pathologically confirmed mediastinal and hilar involvement was 38%. The sensitivity, specificity, and accuracy of mediastinal disease staging were as follows: CT alone = 73%, 77%, 76%; PET alone = 73%, 94%, 87%; PET + CT = 82%, 96%, 91%, respectively. PET was more specific and accurate than CT (p = 0.025). The results of PET changed management decisions in 12 of 50 cases (24%). Using FDG-PET in conjunction with CT scanning provides the most accurate staging of mediastinal disease in lung cancer by contributing complementary information. Furthermore, PET can affect clinical decision-making and allow some patients considered unresectable a chance for resection.