Preparation of Tc-99m-macroaggregated albumin from recombinant human albumin for lung perfusion imaging.

Human serum albumin (HSA) extracted from pooled blood taken from human donors is used in the production of (99m)Tc-labelled macroaggregated albumin (MAA) for lung perfusion imaging. However, concerns for the safety of blood-derived products due to potential contamination by infective agents (e.g. new variant CJD), make alternative production methods necessary. Recombinant DNA technology is a promising method of albumin production avoiding problems associated with human-derived HSA. This paper presents results comparing MAA prepared from recombinant human albumin (rHA, Recombumin) (rMAA) with in-house produced HSA MAA (hMAA) and commercially available MAA (cMAA). (99m)Tc-MAA was prepared using previously published production methods by heating a mixture of albumin and stannous chloride in acetate buffer (pH 5.4) at 70 degrees C for 20 min. Parameters investigated include aggregate size, radiolabelling efficiency, radiochemical and aggregate stability at 4 degrees C and in vitro (in whole human blood) at 37 degrees C and biodistribution studies. Results showed that rMAA could be produced with similar morphology, labelling efficiency and stability to hMAA and cMAA. Our findings confirm that rHA shows significant potential as a direct replacement for HSA in commercially available MAA.

The use of scintigraphy to demonstrate the rapid esophageal transit of the oval film-coated placebo risedronate tablet compared to a round uncoated placebo tablet when administered with minimal volumes of water.

As our population ages, and the consumption of pharmaceutical products rises, the incidence of solid oral dosage forms lodging in the esophagus is likely to increase and may be formulation dependent. The aim of this study was to compare the esophageal transit of the commercial film-coated risedronate tablet and a round uncoated tablet resembling the alendronate 10 mg tablet which is reported to cause esophagitis if ingested with little to no water. Water volumes of 30 ml and 50 ml were selected as these volumes can detect formulations prone to esophageal adhesion and a habits and practice study showed that these volumes are within the range preferred by women (7-385 ml). A total of 28 healthy postmenopausal women completed the four-way crossover scintigraphy study. For both volumes of water, the film-coated placebo risedronate tablet had a statistically significant faster esophageal transit time than the uncoated placebo tablet (P=0.002 for 30 ml water and P<0.001 for 50 ml water). Among those taking the round, flat, uncoated tablet, five subjects had esophageal stasis (transit >20 s) and in three subjects the tablet remained in the esophagus at the end of the 10-min imaging period. No stasis was observed for the oval film-coated placebo risedronate tablet. This study demonstrates that tablet size, shape and coating are pharmaceutical parameters which can be controlled to minimize esophageal contact of a dosage form with esophageal tissue.

The effect of the nasal cycle on mucociliary clearance.

The nasal cycle is a well-recognised physiological phenomenon where each side of the nose alternates through phases of congestion and decongestion. Although many physiological properties of the nose alternate with the nasal cycle whether this has any effect on the nasal mucociliary clearance is less clear. As the nose is a potential site for the administration of pharmaceuticals, it is essential that any factors that could affect clearance (and hence absorption) are identified. This study set out to investigate if mucociliary clearance rates differed between the clear and obstructed airway at a morning peak of the nasal cycle in five healthy volunteers with normal nasal anatomy using a dual-radioisotope labelling procedure that allows both sides of the nose to be assessed simultaneously. The clearance of the radiopharmaceutical formulations from the nasal cavity was monitored using gamma scintigraphy and decay-adjusted 50%-clearance times were calculated for each nostril. The ratios of clearance times from the patent nostril when compared to the obstructed nostril were statistically significant (two-tailed t-test; P = 0.039), the mean ratio being 2.5 : 1 (SEM +/- 0.5). It can be concluded that the nasal cycle has a marked effect on the mucociliary clearance patterns of the nose. This may have both theoretical and practical implications for the nasal delivery of drugs.

Oesophageal transit, disintegration and gastric emptying of a film-coated risedronate placebo tablet in gastro-oesophageal reflux disease and normal control subjects.

BACKGROUND: Risedronate sodium is a pyridinyl bisphosphonate, proven effective for the treatment and prevention of postmenopausal osteoporosis and glucocorticoid-induced osteoporosis and Paget's disease of the bone. AIM: To compare the oesophageal transit, disintegration and gastric emptying of the commercial film-coated risedronate tablet in subjects with gastro-oesophageal reflux disease (GERD) and normal control subjects. METHODS: A total of 30 subjects, 15 patients with GERD and 15 age- and sex-matched, normal control subjects, participated in a single-centre, open-label, comparative gamma scintigraphy study. The GERD subjects had active erosive oesophagitis within 4 weeks prior to dosing. RESULTS: The mean oesophageal transit (GERD, 4.4 s; controls, 3.1 s), mean disintegration (GERD, 21.8 min; controls, 19.2 min) and mean gastric emptying (GERD, 15.9 min; controls, 15.0 min) were similar in the two subject groups. The oesophageal transit is rapid and given the rapid disintegration and gastric emptying, oesophageal contact occurring via reflux of risedronate was unlikely since most, if not all, of the dosage form exited from the stomach within 30 min. CONCLUSIONS: The oval shape and film-coating on the commercial risedronate tablet promotes rapid oesophageal transit and minimizes oesophageal contact, even in the high-risk GERD population.

Imaging for staging bladder cancer: a clinical study of intravenous 111indium-labelled anti-MUC1 mucin monoclonal antibody C595.

OBJECTIVE: To investigate the clinical application of an 111In-labelled anti-MUC1 mucin monoclonal antibody (mAb) imaging for staging invasive bladder cancer. PATIENTS AND METHODS: Indirect immunohistochemistry was used to confirm the expression of the MUC1 target antigen by metastatic tumours. Twelve patients with bladder cancer (two with superficial and 10 with locally invasive/metastatic disease) underwent planar gamma-scintigraphy 48 h after an intravenous injection with 111In-labelled anti-MUC1 mucin mAb C595. RESULTS: No bladder uptake was detected in the two patients with superficial disease, but scintigraphy showed primary and recurrent bladder tumours and metastases in nine of the remaining 10 patients with invasive disease. In three patients additional staging information was obtained from the mAb imaging which would have altered patient management. There were no reported side-effects. CONCLUSION: This study confirmed the ability of the mAb technique to detect both primary and recurrent invasive bladder tumours and distant metastases. Some lesions shown by mAb imaging were not detected by other methods. The use of mAb imaging has the potential to improve clinical staging and assist in selecting those patients most likely to benefit from radical therapy.

Targeting superficial bladder cancer by the intravesical administration of copper-67-labeled anti-MUC1 mucin monoclonal antibody C595.

PURPOSE: More effective intravesical agents are required to limit the recurrence and progression of superficial bladder cancer. This study assessed the ability of copper-67 ((67)Cu)-C595 murine antimucin monoclonal antibody to bind selectively to superficial bladder tumors when administered intravesically, with a view to its development for therapy. PATIENTS AND METHODS: Approximately 20 MBq of (67)Cu-C595 monoclonal antibody was administered intravesically to 16 patients with a clinical indication of superficial bladder cancer. After 1 hour, the bladder was drained and irrigated. Tissue uptake was assessed by imaging and by the assay of tumor and normal tissues obtained by endoscopic resection. RESULTS: Tumor was correctly identified in the images of 12 of 15 patients who were subsequently found to have tumors. Assay of biopsy samples at 2 hours showed a mean tumor uptake of 59.4% of the injected dose per kilogram (SD = 48.0), with a tumor-to-normal tissue ratio of 14.6:1 (SD = 20). After 24 hours (n = 5), this decreased to 4.3% of the injected dose per kilogram (SD = 2.9), with a tumor-to-normal tissue ratio of 1.8:1 (SD = 0.8). CONCLUSION: This study indicates a promising method for the treatment of superficial bladder cancer. Although the mean initial tumor uptake was high, effective therapy of bladder tumors will require an increased retention of the cytotoxic radionuclide in tumor tissue.

Dry powder dosing in liquid vehicles: ocular tolerance and scintigraphic evaluation of a perfluorocarbon suspension.

The ocular tolerance and precorneal disposition of 99mTc-labelled sterile carbon-perfluorodecalin (PFD) and carbon-aqueous suspensions were examined in a cohort of healthy volunteers. Formulations were prepared in PFD or saline using charcoal particles, radiolabelled with [99mTc]diethylenetriaminepentaacetic acid (DTPA) under GMP conditions. Colloidal silicon dioxide was used as a suspending agent. Ocular tolerance was examined following the instillation of each formulation to the eyes of 12 volunteers. The precorneal distribution of both formulations in man was monitored using gamma scintigraphy. Dynamic and static data acquisitions were taken over a period of 150 min after dosing. Carbon particulates suspended in PFD did not show any irritation to the eye. Administration of PFD formulation in man produced a significant increase in ocular retention over a saline formulation (mean residence time (MRT)=157+/-42 and 0.29+/-0.08 min, respectively, P=0.0001). Distribution of the carbon in man followed the same pattern as in a previous reported study in animals. The carbon deposited uniformly along the lid margin in the case of the PFD vehicle, whereas it agglomerated following dosing in the saline vehicle and was ejected from the eye. The novel non-aqueous vehicle system is able to significantly improve the ocular retention of charcoal particles in man and provides a unique distribution of the particles in the eye, which suggests a potential for the PFD system for the treatment of periocular diseases.

Esophageal transit of risedronate cellulose-coated tablet and gelatin capsule formulations.

Risedronate sodium is an orally active antiresorptive agent and a member of the pyridinyl class of bisphosphonates. It has been approved for the treatment of Paget's disease of the bone and is under development as a chronic therapy for the treatment and prevention of osteoporosis. A novel cellulose film-coated tablet formulation was developed to optimize esophageal transit of this bisphosphonate. The aim of the present study was to compare the esophageal transit of the film-coated tablet formulation of risedronate with its original gelatin capsule dose form. A total of 25 elderly, healthy volunteers (mean 66 years), who were dysphagia-free, participated in this randomized cross-over study. On separate occasions, volunteers swallowed radiolabeled placebo formulations with 50 ml water. Dynamic images with participants in a sitting position were recorded for 10 min using a gamma camera. Scintigraphic imaging showed a delay in esophageal transit (greater than 15 s) in 28% of patients in the capsule group but in none of the tablet group (P<0.05). The mean transit times of the capsules and tablets were 23.8 and 3.3 s, respectively. Esophageal transit of film-coated tablets was faster than gelatin capsules, suggesting that film-coated tablets would be the appropriate formulation for all pivotal trials with risedronate and for subsequent commercialization.

Regional differences in quinine absorption from the undisturbed human colon assessed using a timed release delivery system.

PURPOSE: To investigate the regional absorption characteristics of the distal gut using two markers of permeability, quinine (a transcellular probe) and 51CrEDTA (a paracellular probe). METHODS: The permeability markers were delivered to the undisturbed gastrointestinal tract in 39 healthy volunteers using an oral timed-release delivery vehicle which allowed pulsed release within a particular site of the gut. Site of release was identified using gamma scintigraphy. Absorption of quinine and 51CrEDTA was assessed by measuring the percent excretion in the urine using HPLC and gamma counting respectively. Serial plasma samples allowed time-concentration curves for quinine to be plotted. RESULTS: There was a significant trend for diminished absorption with more distal delivery of the transcellular probe, quinine, which was: 6.26 +/- 0.87% (small intestine, n = 10); 4.65 +/- 0.93% (ascending colon, n = 16); and 2.59 +/- 0.52% (transverse colon, n = 10) of the ingested dose excreted respectively (p < 0.001). No such gradient was seen with the paracellular marker, 51CrEDTA. CONCLUSIONS: These results suggest that delayed release formulations should aim for release in the distal small bowel and proximal colon if absorption is to be maximised. Absorption by the transcellular route diminishes in the more distal colon, a fact which has implications for delayed or sustained release formulations.

An immunoscintigraphic evaluation of the engineered human monoclonal antibody (hCTMO1) for use in the treatment of ovarian carcinoma.

OBJECTIVE: To assess the safety and targeting ability of the engineered human antibody (hCTMO1) in women with ovarian carcinoma. DESIGN: The monoclonal antibody labelled with Indium-111 was administered to women with suspected primary or recurrent ovarian carcinoma six days pre-operatively. The first group of women was given a dose of 0.1 mg per kg body weight of radiolabelled antibody. A second group of women received 1 mg per kg body weight and finally a third group was given 1 mg per kg body weight of unlabelled antibody followed one hour later by 0.1 mg per kg body weight of radiolabelled antibody. All the women were then imaged using a gamma camera one hour and up to 96 hours after injection. PARTICIPANTS: Fourty-four women in whom there was a high suspicion of primary ovarian carcinoma on the basis of ultrasound or CT imaging and serum CA125 and those in whom there was a suspicion of recurrent ovarian carcinoma after being treated for histologically confirmed carcinoma. SETTING: The Queen's Medical Centre, Nottingham and University Hospital Vrije Universiteit, Amsterdam, The Netherlands. RESULTS: At the low dose of antibody the sensitivity for detection of ovarian carcinoma was 70%. After increasing the dose of antibody and also after pre-dosing with unlabelled antibody the sensitivity increased to 100%, but there was a large number of false positive results at the higher dose, and therefore the specificity was low. The liver and bone marrow were the organs with the highest activities. CONCLUSION: The genetically engineered antibody hCTMO1 is safe for use in women. This antibody effectively targets ovarian carcinoma and has greater potential as a vector for therapeutic use than as a diagnostic agent.

Gastric emptying and intestinal transit of pancreatic enzyme supplements in cystic fibrosis.

OBJECTIVE: To investigate gastric emptying and intestinal transit of pelleted pancreatin in relation to food boluses. METHODS: Dual isotope scintigraphy combined with breath hydrogen sampling was used to track the concurrent gastric emptying and intestinal transit of 111indium labelled microspheres and a 99mtechnetium labelled tin colloid test meal. Twelve pancreatic insufficient cystic fibrosis patients aged 5 to 38 years performed the study. RESULTS: 50% gastric emptying times showed patient to patient variation. The mean discrepancy in 50% gastric emptying times between the two labels was > 67 minutes. Mean small bowel transit time for the food bolus was prolonged at 3.6 minutes. A significant correlation was seen between weight standard deviation score and 50% emptying time for pancreatin (r = +0.73). CONCLUSION: Gastric mixing of food and pancreatin may be limited by rapid emptying of microspheres. Patients with high dosage requirements could benefit from changing the pattern of their pancreatin supplementation.

Evaluation of the clearance characteristics of bioadhesive systems in humans.

This paper describes the characterisation, radiolabelling and clearance characteristics of three bioadhesive nasal delivery systems; starch microspheres, chitosan microspheres and chitosan solution. The time taken for 50% of these bioadhesive materials and a control to be cleared from the nasal cavity, after nasal administration to human volunteers, was evaluated using gamma scintigraphy. The data show that the control was cleared rapidly, with a half life of 21 min, whereas the bioadhesive delivery systems had much longer half lives. The clearance of the chitosan solution almost doubled to 41 min, whilst the half life of clearance for the starch microspheres more than tripled to 68 min and for the chitosan microspheres the half life of clearance quadrupled to 84 min. From the results reported in this study it is possible to determine that both chitosan systems and the starch microspheres have good bioadhesive characteristics. The results have supported the hypothesis that chitosan delivery systems can reduce the rate of clearance from the nasal cavity, thereby increasing the contact time of the delivery system with the nasal mucosa, providing the potential for increasing the bioavailability of drugs incorporated into these systems.

Night-time quiescence and morning activation in the human colon: effect on transit of dispersed and large single unit formulations.

OBJECTIVES: Controlling the delivery of drugs to different regions of the colon remains an elusive goal. The aim of this study was to define the diurnal variation in colonic transit and show how this influences the colonic distribution and residence time of different formulations given either in the morning or evening. METHODS: Colonic transit of small particulates and a large capsule was measured during nocturnal sleep and daytime wakefulness. Eighteen healthy volunteers participated in a randomised crossover study. 111In-labelled resin (150-300 microm) and a large 99mTc-labelled non-disintegrating capsule (22 x 8 mm) were swallowed at either 0800h or 1700h. MAIN OUTCOME MEASURES: The geometric centre of isotope (range 1-9) was calculated from serial scintiscans allowing comparison of overnight and daytime transit. RESULTS: Transit of resin was delayed in the overnight compared to daytime 8 h periods (change in geometric centres (GCs), mean +/- SEM, 0.59 +/- 0.14 vs 1.46 +/- 0.39 respectively, P < 0.02). Maximal resin movement occurred immediately after awakening, prior to breakfast, in 9/18 studies (P < 0.05). The capsule was more distal than the resin at the end of the study 15 h after dosing (P < 0.001). There was marked inter-individual variability in distribution of both resin and capsule at 15 h, the range of GCs being 2.8-9 and 2.2-9, respectively. CONCLUSION: Sleep delays colonic transit and large capsules travel faster than dispersed small particles. However, substantial inter-individual variability in transit makes targeting specific regions of the human colon unreliable with either dispersed or single unit formulations.

Biodistribution of 111In-labelled engineered human antibody CTM01 (hCTM01) in ovarian cancer patients: influence of prior administration of unlabelled hCTM01.

mAb hCTM01 binds a carcinoma-associated antigen, the MUC1 gene product. The antigen is also present in the circulation, and administration of 111In-labelled hCTM01 results in the formation of immune complexes with enhanced accumulation in the liver. To avoid the unwanted effect of circulating radioactive immune complexes, a strategy to remove the circulating antigen was investigated using a split-dosage schedule. Eleven patients suspected of having ovarian carcinoma were injected with 1 mg/kg unlabelled hCTM01, 1 h before receiving 0.1 mg/kg 111In-labelled hCTM01 (100 M Bq). The amount of radioactivity was determined in resected tumour tissue, various normal tissues and blood samples obtained at laparotomy 6 days postinjection (p.i.). In all patients, the circulating antigen decreased to its nadir after the unlabelled antibody infusion and immune complex formation was demonstrated. Uptake in tumour deposits 6 days p.i. was 11.1 times higher than in normal tissues (P < 0.0001) and 5.9 times higher than in blood (P < 0.0001). 111In activity in liver tissue was comparable to 111In uptake in tumour tissue, and considerably lower than previously reported in patients not pretreated with unlabelled antibody. The split-dosing strategy would appear to be advantageous for use of hCTM01 as a specific carrier for the delivery of cytotoxic agents to patients with ovarian cancer.

The use of dual-isotope imaging to compare the gastrointestinal transit of food and pancreatic enzyme pellets in cystic fibrosis patients.

Cystic fibrosis patients require pancreatic enzyme supplements to aid food digestion. It is suspected that incorrect delivery of this enzyme may result in both significant malabsorption and the development of strictures in the proximal colon caused by the high-dose supplement reaching this region before the food. Investigations into the drug's delivery were performed using dual-isotope imaging; a method was developed to directly label the enteric-coated enzyme pellets with 111In, re-applying the enteric coating afterwards, and this was then ingested with a pancake meal labelled with 99Tcm-tin colloid. Consecutive image data, acquired over a period of > or = 4 h using a dual-headed gamma camera, were analysed to assess intestinal transit. In-vitro stability checks on these labelling techniques were encouraging, showing < 2% 99Tcm and < 7% 111In elution over 90 min in hydrochloric acid. In 5 of the 12 patients studied to date, the pellets were seen to pass through significantly faster than the food, with a mean difference in 50% gastric emptying time of greater than 93 min. The mean absolute difference in emptying time for all 12 patients was > 67 min. Thus, a technique has been developed to effectively radiolabel pancreatic enzyme pellets, and analysis of dual-isotope images using this preparation, together with radiolabelled solid food, has demonstrated significant differences in the transit of these two substances through the gastrointestinal tract of some cystic fibrosis patients.

Ocular contact time of a carbomer gel (GelTears) in humans.

BACKGROUND/AIMS: Carbomers are widely used in products for the treatment of dry eye; however, the polymer gel thins on addition of probes (for example, fluorescein salt) confounding the comparison of products by objective clinical tests such as spectrophotofluorimetry or scintigraphy. A novel method of radiolabelling carbomer gels, with minimum change to their rheology, has permitted the non-invasive evaluation of precorneal residence of the gel in volunteers using gamma scintigraphy. The technique was used to evaluate the precorneal clearance of the liquid phase and of a suspended particulate in GelTears. METHODS: Low sodium technetium-99m labelled diethylenetriaminepentacetic acid (99mTc-DTPA) was used to label carbomer 940 gel, either adsorbed onto sterile charcoal to model an entrapped drug, or added directly to the gel to a final activity of 1 MBq per 25 microliters dose. The clearance of the labelled gels was then compared with 99mTc-DTPA labelled saline in 12 volunteers. RESULTS: The addition of the low sodium radiopharmaceutical produced insignificant rheological changes in the gel compared with conventional 99mTc-DTPA labelling. The residence times on the eye of the gel formulations were significantly greater than that of the saline control. At 8 minutes postdosing, the label levels retained (mean (SD)) on the ocular surface were: saline, 7% (7%); 99mTc-DTPA gel, 42% (27%); and 99mTc-carbon gel, 42% (20%) of administered dose. There was no difference observed in the precorneal distribution between 99mTc-DTPA solution and particulate markers. CONCLUSIONS: These data demonstrate that carbomer based gels significantly extend contact of solutes or suspended solids with the corneal surface. The method of labelling does not significantly change the initial viscosity and is superior to previous methods which have used sodium salts (for example, sodium fluorescein) and therefore underestimate contact time.