Pharmacokinetics of Polymersomes Composed of Poly(Butadiene-Ethylene Oxide); Healthy versus Tumor-Bearing Mice.

Vesicles composed of block copolymers (i.e., polymersomes) are one of the most versatile nano-carriers for medical purposes due to their tuneable physicochemical properties and the possibility to encapsulate simultaneously hydrophobic and hydrophilic substances, allowing, for instance, the combination of therapy and imaging. In cancer treatment, these vesicles need to remain long enough in the blood stream to be sufficiently taken up by tumors. Here, we have investigated the biodistribution and the pharmacokinetics of polymersomes, composed of poly(butadiene-b-ethylene oxide) having dimensions around 80 nm. The polymersomes have been radiolabeled with ¹¹¹In via the so-called active loading method achieving a loading efficiency of 92.9 ± 0.9% with radionuclide retention in mouse serum of more than 95% at 24 h. The optimized ¹¹¹In containing polymersomes have been intravenously administered in healthy and tumor bearing mice for pharmacokinetic determination using microSPECT (Single Photon Emission Computed Tomography). In healthy mice these polymersomes have been found to exhibit relatively long blood circulation (> 6 h), low liver uptake (6 ± 1.5%ID/g, 48 h p.i.) and elevated spleen uptake (188 ± 30%ID/g). The blood circulation in tumor bearing mice is dramatically reduced (< 1.5 h) most likely due to elevated splenic filtration, clearly indicating the importance of in vivo studies in diseased mice. Finally, the polymersomes have been injected subcutaneously in tumor bearing mice revealing retention of 77% in the mice, primarily accumulated at the site of injection, up to 48 hours after administration.

H2CHXdedpa and H4CHXoctapa-chiral acyclic chelating ligands for (67/68)Ga and (111)In radiopharmaceuticals.

The chiral acyclic ligands H2CHXdedpa (N4O2), H2CHXdedpa-bb (N4O2), and H4CHXoctapa (N4O4) (CHX = cyclohexyl/cyclohexane, H2dedpa = 1,2-[[6-carboxy-pyridin-2-yl]-methylamino]ethane, bb = N,N'-dibenzylated, H4octapa = N,N'-bis(6-carboxy-2-pyridylmethyl)-ethylenediamine-N,N'-diacetic acid) were synthesized, complexed with Ga(III) and/or In(III), and evaluated for their potential as chelating agents in radiopharmaceutical applications. The ligands were compared to the previously studied hexadentate H2dedpa and octadentate H4octapa ligands to determine the effect adding a chiral 1R,2R-trans-cyclohexane to replace the ethylenediamine backbone would have on metal complex stability and radiolabeling kinetics. It was found that [Ga(CHXdedpa)](+) showed very similar properties to those of [Ga(dedpa)](+), with only one isomer in solution observed by NMR spectroscopy, and minimal structural changes in the solid-state X-ray structure. Like [Ga(dedpa)](+), [Ga(CHXdedpa)](+) exhibited exceptionally high thermodynamic stability constants (log KML = 28.11(8)), and the chelate retained the ability to label (67)Ga quantitatively in 10 min at room temperature at ligand concentrations of 1 × 10(-5) M. In vitro kinetic inertness assays demonstrated the [(67)Ga(CHXdedpa)](+) complex to be more stable than [(67)Ga(dedpa)](+) in a human serum competition, with 90.5% and 77.8% of (67)Ga remaining chelate-bound after 2 h, respectively. Preliminary coordination studies of H4CHXoctapa with In(III) demonstrated [In(CHXoctapa)](-) to have an equivalently high thermodynamically stable constant as [In(octapa)](-), with log KML values of 27.16(9) and 26.76(14), respectively. The [(111)In(CHXoctapa)](-) complex showed exceptionally high in vitro kinetic inertness over 120 h in human serum, comparing well with previously reported [(111)In(octapa)](-) values, and an improved stability compared to the current industry "gold standards" 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and diethylenetriaminepentaacetic acid (DTPA). Initial investigations reveal that the chiral acyclic hexadentate H2CHXdedpa and octadentate H4CHXoctapa ligands are ideal candidates for radiopharmaceutical elaboration of gallium or indium isotopes, respectively.

Evaluating abdominal oedema during experimental sepsis using an isotope technique.

PURPOSE: Abdominal oedema is common in sepsis. A technique for the study of such oedema may guide in the fluid regime of these patients. PROCEDURES: We modified a double-isotope technique to evaluate abdominal organ oedema and fluid extravasation in 24 healthy or endotoxin-exposed ('septic') piglets. Two different markers were used: red blood cells (RBC) labelled with Technetium-99m ((99m)Tc) and Transferrin labelled with Indium111 ((111)In). Images were acquired on a dual-head gamma camera. Microscopic evaluation of tissue biopsies was performed to compare data with the isotope technique. RESULTS: No (99m)Tc activity was measured in the plasma fraction in blood sampled after labelling. Similarly, after molecular size gel chromatography, (111)In activity was exclusively found in the high molecular fraction of the plasma. Extravasation of transferrin, indicating the degree of abdominal oedema, was 4·06 times higher in the LPS group compared to the healthy controls (P<0·0001). Abdominal free fluid, studied in 3 animals, had as high (111)In activity as in plasma, but no (99m)Tc activity. Intestinal lymphatic vessel size was higher in LPS (3·7 ± 1·1 µm) compared to control animals (0·6 + 0·2 µm; P<0·001) and oedema correlated to villus diameter (R(2) = 0·918) and lymphatic diameter (R(2) = 0·758). A correlation between a normalized index of oedema formation (NI) and intra-abdominal pressure (IAP) was also found: NI = 0·46*IAP-3·3 (R(2) = 0·56). CONCLUSIONS: The technique enables almost continuous recording of abdominal oedema formation and may be a valuable tool in experimental research, with the potential to be applied in the clinic.

Correlation between radioactivity and chemotherapeutics of the (111)In-VNB-liposome in pharmacokinetics and biodistribution in rats.

BACKGROUND: The combination of a radioisotope with a chemotherapeutic agent in a liposomal carrier (ie, Indium-111-labeled polyethylene glycol pegylated liposomal vinorelbine, [(111)In-VNB-liposome]) has been reported to show better therapeutic efficiency in tumor growth suppression. Nevertheless, the challenge remains as to whether this therapeutic effect is attributable to the combination of a radioisotope with chemotherapeutics. The goal of this study was to investigate the pharmacokinetics, biodistribution, and correlation of Indium-111 radioactivity and vinorelbine concentration in the (111)In-VNB-liposome. METHODS: The VNB-liposome and (111)In-VNB-liposome were administered to rats. Blood, liver, and spleen tissue were collected to determine the distribution profile of the (111)In-VNB-liposome. A liquid chromatography tandem mass spectrometry system and gamma counter were used to analyze the concentration of vinorelbine and radioactivity of Indium-111. RESULTS: High uptake of the (111)In-VNB-liposome in the liver and spleen demonstrated the properties of a nanosized drug delivery system. Linear regression showed a good correlation (r = 0.97) between Indium-111 radioactivity and vinorelbine concentration in the plasma of rats administered the (111)In-VNB-liposome. CONCLUSION: A significant positive correlation between the pharmacokinetics and biodistribution of (111)Indium radioactivity and vinorelbine in blood, spleen, and liver was found following administration of the (111)In-VNB-liposome. The liposome efficiently encapsulated both vinorelbine and Indium-111, and showed a similar concentration-radioactivity time profile, indicating the correlation between chemotherapy and radiotherapy could be identical in the liposomal formulation.

Biodistribution and dosimetry of In-111/Y-90-HuCC49ΔCh2 (IDEC-159) in patients with metastatic colorectal adenocarcinoma.

BACKGROUND: CC49, an antibody (mAb) reactive to tumor-associated glycoprotein (TAG-72), has been extensively studied for radioimmunotherapy for colon cancer. Myelotoxicity has been dose-limiting because of prolonged circulation time in the plasma, and human anti-mouse antibody responses were observed in the majority of patients. A CH2 domain deleted and humanized CC49 (HuCC49ΔCh2) was developed to ameliorate these problems. This study reports biodistribution and dosimetry of (111)In/(90)Y-HuCC49ΔCh2 (IDEC-159). MATERIALS AND METHODS: Five (5) patients with colon cancer were enrolled. Each patient received intravenous administration of 185 MBq (111)In-HuCC49ΔCh2, followed by sequential gamma camera imaging, and blood counting. Uptakes and clearance half-lives for organs and tumors were quantified from images. Absorbed doses for (90)Y-HuCC49ΔCh2 were derived from (111)In-HuCC49ΔCh2 kinetic data. RESULTS: Compared to reported (111)In/(90)Y-CC49 data in the literature, median blood circulation T(1/2ß) was less at 38 (31-43) hours for (90)Y-HuCC49ΔCh2, than 50 hours for (90)Y-CC49. Median tumor-to-marrow absorbed dose ratio was 18 for (90)Y-HuCC49ΔCh2, and 9.53 for (90)Y-CC49. Median tumor-to-liver absorbed dose ratio was 3.14 for (90)Y-HuCC49ΔCh2, and 1.0 for (90)Y-CC49. Median tumor-to-spleen absorbed dose was 3.19 for (90)Y-HuCC49ΔCh2, and 1.07 for (90)Y-CC49. CONCLUSIONS: A humanized and CH2 domain-deleted CC49 antibody radiolabeled with (111)In/(90)Y showed improved tumor-to-normal dose ratios over those reported from studies with intact CC49.

¹¹¹Indium-labeled ultrafine carbon particles; a novel aerosol for pulmonary deposition and retention studies.

Continuous environmental or occupational exposure to airborne particulate pollution is believed to be a major hazard for human health. A technique to characterize their deposition and clearance from the lungs is fundamental to understand the underlying mechanisms behind their negative health effects. In this work, we describe a method for production and follow up of ultrafine carbon particles labeled with radioactive ¹¹¹Indium (¹¹¹In). The physicochemical and biological properties of the aerosol are described in terms of particle size and concentration, agglomeration rate, chemical bonding stability, and human lung deposition and retention. Preliminary in vivo data from a healthy human pilot exposure and 1-week follow up of the aerosol is presented. More than 98% of the generated aerosol was labeled with Indium and with particle sizes log normally distributed around 79 nm count median diameter. The aerosol showed good generation reproducibility and chemical stability, about 5% leaching 7 days after generation. During human inhalation, the particles were deposited in the alveolar space, with no central airways involvement. Seven days after exposure, the cumulative activity retention was 95.3%. Activity leaching tests from blood and urine samples confirmed that the observed clearance was explained by unbound activity, suggesting that there was no significant elimination of ultrafine particles. Compared to previously presented methods based on Technegas, ¹¹¹In-labelled ultrafine carbon particles allow for extended follow-up assessments of particulate pollution retention in healthy and diseased lungs.

Biodistribution, pharmacokinetics, and nuclear imaging studies of 111In-labeled rGel/BLyS fusion toxin in SCID mice bearing B cell lymphoma.

PURPOSE: We examined the biodistribution and pharmacokinetics of (111)In-labeled rGel/BLyS, a gelonin toxin (rGel)-B lymphocyte stimulator (BLyS) fusion protein. MATERIALS AND METHODS: rGel/BLyS was labeled with In-111 through DTPA with a labeling efficiency >95%. Biodistribution/imaging studies were obtained in severe-combined immunodeficiency mice bearing diffuse large B cell lymphoma OCI-Ly10. Pharmacokinetic studies were performed in BALB/c mice. RESULTS: In vitro, DTPA-conjugated rGel/BLyS displayed selective cytotoxicity against OCI-Ly10 cells and mantle cell lymphoma JeKo cells. In vivo, rGel/BLyS exhibited a tri-exponential disposition with a rapid initial mean distribution followed by an extensive mean distribution and a long terminal elimination phase. At 48 h after injection, uptake of the radiotracer in tumors was 1.25 %ID/g, with a tumor-to-blood ratio of 13. Tumors were clearly visualized at 24-72 h post-injection. Micro-SPECT-CT images and ex vivo analyses confirmed the accumulation of rGel/BLyS in OCI-Ly10 tumors. CONCLUSIONS: (111)In-DTPA-rGel/BLyS are distributed to B cell tumors and induce apoptosis in tumors. Preclinical antitumor studies using rGel/BLyS should use a twice-per-week treatment schedule.

Measuring whole-body neutrophil redistribution using a dedicated whole-body counter and ultra-low doses of 111Indium.

BACKGROUND: There is increasing interest in the 'homing' of neutrophils to bone marrow. The aim of this study was to measure the whole-body redistribution of (111) In using a whole-body counter following the administration of ultra-small activities of (111) In-labelled neutrophils. METHODS: The detectors of a dedicated whole-body counter were fitted with lead collimators. Whole-body (111) In distribution was recorded at 45 min, 24 h, and 2, 4, 7 and 10 days after administration of (111) In-labelled neutrophils (0·29-0·74 MBq) in eight healthy non-smokers, five healthy smokers, eight patients with inactive bronchiectasis, three with asthma and nine with chronic obstructive pulmonary disease (COPD). RESULTS: Intravascular 45-min (111) In-labelled neutrophil recovery was not significantly different between groups, ranging from 33 (SD 8%) in healthy smokers to 45 (14%) in healthy non-smokers (P > 0·05). Peaks were identified on the whole body count profile corresponding to the chest, upper abdomen (liver/spleen) and pelvis (bone marrow). (111) In distribution changed between 45 min and 24 h and then remained stable thereafter. Peak chest counts increased ∼ 1·5-fold between 45 min and 24 h, whereas upper abdominal peak counts decreased by ∼ 25% with no significant inter-group differences. The increment in pelvic counts (∼ 2·7-fold) was similar between groups, except COPD patients, in whom it was 2·04 (0·35; P < 0·02 vs. healthy participants). CONCLUSIONS: Assuming neutrophils are distributed only between blood, liver, spleen and bone marrow, the data suggest that marrow pools 25% and destroys 67% of circulating neutrophils, rising in COPD to 40% and 80%, respectively, possibly as a result of the effects on marrow of chronic hypoxaemia.

A pretherapy biodistribution and dosimetry study of indium-111-radiolabeled trastuzumab in patients with human epidermal growth factor receptor 2-overexpressing breast cancer.

PURPOSE: The purposes of this study were to evaluate the organ biodistribution, pharmacokinetics, immunogenicity, and tumor uptake of (111)Indium ((111)In)-MxDTPA-trastuzumab in patients with human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancers and to determine whether (90)Y-MxDTPA-trastuzumab should be evaluated in subsequent clinical therapy trials. EXPERIMENTAL DESIGN: Patients with HER2-overexpressing breast cancers who were to undergo planned trastuzumab therapy first received unlabeled trastuzumab (4-8 mg/kg IV), followed 4 hours later by 5 mCi (111)In-MxDTPA-trastuzumab (10 mg antibody). Serial blood samples, 24-hour urine collections, and nuclear scans were performed at defined time points for 7 days. RESULTS: Eight (8) patients received (111)In-MxDTPA-trastuzumab, which was well tolerated with no adverse side-effects. Three (3) of 7 patients with known lesions demonstrated positive imaging on nuclear scans. No antiantibody responses were observed for 2 months postinfusion. Organ doses (cGy/mCi) assuming radiolabeling with (90)Y were 19.9 for heart wall, 17.6 for liver, 4.6 for red marrow, and 2.8 for the whole body. Tumor doses ranged from 24 to 172 cGy/mCi. CONCLUSIONS: In summary, results from this study indicate that (90)Y-MxDTPA-trastuzumab is an appropriate agent to evaluate in therapy trials. No evidence of an immune response to (111)In-MxDTPA-trastuzumab was detected, predicting for the ability to administer multiple cycles. With the exception of cardiac uptake, pharmacokinetics and organ biodistribution were comparable to other (90)Y-labeled monoclonal antibodies previously evaluated in the clinic. Cardiac uptake was comparable to hepatic uptake and therefore predicted to not be prohibitively high as to result in dose-limiting cardiotoxicity.

Stabilities of 67ga- and 111In-labeled transferrin in vitro.

We attempted to develop a stable radiolabeled transferrin (Tf) useful in experimental studies related to Tf receptor. 67Ga and 111In were used as labeling radioisotopes. The results from gel chromatography, dialysis, and electrophoresis showed that 111In-DTPA-Tf was the most stable among the radiolabeled Tfs examined in the present study. 111In-DTPA-Tf was also the most stable radiolabeled transferrin in the blood.

A comparison of biodistribution between 111In-DTPA octreotide and 111In-DOTATOC in rats bearing pancreatic tumors.

111In-DTPA octreotide (DTPAOC) has been used for detecting somatostatin receptor positive tumor for years. In-111 DOTA-Tyr3-octreotide (DOTATOC) is newly developed for diagnostic and therapeutic purposes. In this study, we compared the biodistribution and tumor uptake ratio after injection of In-111 DTPAOC and In-111 DOTATOC in rats. Twelve rats bearing pancreatic tumors were divided into two groups: six rats were sacrificed at 4 hr after injection of 3.7 MBq of In-111 DTPAOC and another 6 rats were sacrificed at the same time after injection of 3.7 MBq of In-111 DOTATOC. Samples of various organs were obtained and counted to calculate the tissue concentration. In addition, 12 rats bearing pancreatic tumors were scanned at 4, 24, and 48 hr after injection of 37 MBq of In-111 DTPAOC or In-111 DOTATOC. The tumor uptake ratios (T/N ratio) were calculated. The biodistribution data showed that the activity in the tumor as well as in the kidney was significantly higher in the In-111 DOTATOC group than in the In-111 DTPAOC group, although both radiopharmaceuticals had the expected high affinity to the tumor. The T/N ratios in the In-111 DOTATOC group were also significantly higher than those in the In-111 DTPAOC group at 24 hr after injection. We conclude that In-111 DOTATOC showed lower clearance than In-111 DTPAOC in the rats bearing pancreatic tumors, although both of these radiopharmaceuticals showed expected high tumor uptake.

In vivo evaluation of 111In-labeled T-lymphocyte homing in experimental colitis.

UNLABELLED: Blockade of lymphocyte recruitment to the intestinal mucosa is considered a useful therapy for inflammatory bowel disease (IBD) and anti-alpha4 antibodies have clinical benefit in patients with active Crohn's disease. The aim of this study was to evaluate a scintigraphic technique to assess lymphocyte homing to the colon in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced experimental colitis (TNBS colitis) in vivo. METHODS: TNBS-sensitized and nonsensitized murine total lymphocytes or CD4+ lymphocytes were radiolabeled with 111In-oxinate. Cells were injected into control mice (n = 5) or mice with TNBS colitis (n = 5). Specific abdominal radioactive uptake was determined by SPECT using a dedicated pinhole system 48 h after cell transfer. Radioactive colon uptake was correlated with histology and colon weight as parameters of inflammation. RESULTS: The radioactive colon uptake was most evident in mice with TNBS colitis that received sensitized lymphocytes (uptake ratio [mean +/- SEM], 0.51 +/- 0.03 vs. 0.22 +/- 0.04; P = 0.004). The sensitized 111In-labeled lymphocytes exacerbated colitis compared with nonsensitized lymphocytes. The colon uptake correlated well with both colon weight and histologic score (R2 = 0.836 and 0.933, respectively). The use of purified 111In labeled CD4+ lymphocytes resulted in a similar scintigraphic pattern. Administration of an anti-alpha4 antibody decreased radioactivity colon uptake of the (111)In-labeled cells compared with the control antibody in mice with TNBS colitis (uptake ratio, 0.72 +/- 0.14 to 0.33 +/- 0.03; P = 0.012). CONCLUSION: Animal pinhole SPECT can be applied for temporal and spatial analysis of the lymphocyte homing process in experimental colitis. This technique makes possible the in vivo evaluation of therapeutic efficacy of new drugs that interfere with lymphocyte migration. Moreover, colon uptake of radioactivity can be used as a parameter of disease activity in experimental colitis.

Evaluation of a cathepsin-cleavable peptide linked radioimmunoconjugate of a panadenocarcinoma MAb, m170, in mice and patients.

PURPOSE: Radioimmunotherapy (RIT) delivered by radiometal immunoconjugates (RICs) is dose limited by deposition and retention of radioactivity in normal tissues. In order to increase elimination of radioactivity from the liver and body, a peptide having a specific cathepsin B cleavage site was placed between the radiometal chelate, 111In-DOTA, and the panadenocarcinoma monoclonal antibody (MAb), m170. EXPERIMENTAL DESIGN: Indium-111 (111In)-1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA)-2-iminothiolane (2IT)-m170 and 111In-DOTA-peptide-m170, representing the same MAb and chelate without and with a cleavable linkage, were studied in athymic mice and patients with breast or prostate cancer. Pharmacokinetics, cumulated activities and therapeutic indices (TI), were evaluated. Cumulated activities in the liver and tumors were calculated and used as a surrogate for radiation dose. RESULTS: Except for liver, the pharmacokinetics of 111In-DOTA-peptide-m170 were similar to those of the 111In-2IT-2-[p(bromoacetamido)benzyl]-1,4,7,10-tetraazocyclododecane-N,N',N",N"'-tetraacetic acid-m170 (111In-2IT-BAD-m170) in mice and patients. Liver cumulated activities for 111In-DOTA-peptide-m170 were consistently decreased when compared to those for 111In-2IT-BAD-m170, reductions varying between 22-30%. Cumulated activities for 111In-DOTA-peptide-m170 in the malignant tumors of the patients were as great as those for 111In-2IT-BAD-m170, so that the tumor-to-liver cumulated activity ratios (therapeutic indices) were better for 111In-DOTA-peptide-m170. CONCLUSIONS: A cathepsin-B-cleavable peptide used to link chelated 111In to MAb, m170, reduced liver cumulated activity (radiation dose) and improved the TI. This novel linker illustrates the importance of linker technology in the development of safer RICs for cancer therapy.

Tissue-to-blood transport of radiolabelled immunoglobulin injected into the web spaces of the hands of normal subjects and patients with breast cancer-related lymphoedema.

AIM: The ability to return interstitial protein to central blood is key to the defence against oedema. The aim of this study was to quantify this ability by measuring the rate at which radiolabelled human immunoglobulin (HIgG) accumulated in blood following injection into the subcutis of the hand in normal volunteers and in patients with breast cancer-related lymphoedema (BCRL). METHODS: A total of 37 control subjects (healthy normal volunteers or breast cancer patients prior to treatment) and 18 women with BCRL were studied with dual-isotope lymphoscintigraphy. Each received bilateral subcutaneous depot injection in the dorsal web space of HIgG labelled with Tc-99m on one side and In-111 on the other. Activities remaining at the depot and accumulating in blood were measured at regular intervals for 3 h. Clearance from the depot was exponential and expressed as the rate constant k(depot) (min(-1)). Accumulation in blood was essentially linear and, using an estimate of blood volume based on height and weight, was expressed as the linear constant b(blood) (% administered activity x min(-1)). The time axis intercept of this linear fit was recorded as an index of the minimum time to arrival of radioprotein in blood. The efficiency with which radioprotein that has left the depot (extra-depot activity) is transported into blood [tissue-to-blood (T-B) transport] was quantified (1) as the quotient b(blood)/k(depot), and (2) as a function of time after injection by comparing the total amount of radioprotein in blood at any time with the total amount of radioprotein that was no longer in the depot at the same time. RESULTS: Tc-99m-HIgG and In-111-HIgG behaved similarly and are interchangeable. At all times between 60 and 180 min in controls, about 50% of protein that had left the depot was present in blood. T-B transport was reduced to about 20% in BCRL arms in which the hand was involved in swelling (p < 0.001 versus controls), but remained unchanged in patients in whom the hand was spared. The minimum time to arrival of radioprotein in blood was not reduced in BCRL; on the contrary, there appeared to be a small proportion of injected activity that arrived rapidly in blood in BCRL patients but not in controls. CONCLUSION: We conclude that T-B transport is only impaired in BCRL when radioprotein is injected into swollen tissue. Significant quantities of radioprotein may escape from the arm via local access to blood. Individual variation in this capacity may explain the regional sparing observed in BCRL.

A bivalent leukotriene B(4) antagonist for scintigraphic imaging of infectious foci.

UNLABELLED: Several radiolabeled chemotactic peptides have been tested for their suitability to show infection and inflammation. Leukotriene B(4) (LTB(4)) receptor-binding ligands could be useful agents for revealing neutrophilic infiltrations because the LTB(4) receptor is abundantly expressed on neutrophils after an inflammatory stimulus. In this study, we investigated the in vivo and in vitro characteristics of a new hydrophilic (111)In-labeled LTB(4) antagonist. METHODS: The LTB(4) antagonist DPC11870-11 was labeled with (111)In and intravenously injected into New Zealand White rabbits with Escherichia coli infection in the left thigh muscle. The pharmacokinetics and biodistribution were studied by serial scintigraphic imaging (0-24 h after injection) and by ex vivo counting of dissected tissues (6 and 24 h after injection). The receptor-mediated in vivo localization of the compound was investigated in 3 rabbits that received an excess of nonradioactive indium-labeled agent 2 min before the administration of the (111)In-labeled LTB(4) antagonist. RESULTS: In rabbits with intramuscular E. coli infection, the abscess was visualized as early as 2 h after injection. Accumulation in the abscess increased with time, resulting in excellent images at 6 h after injection. Blood clearance was rapid in the first hours after injection (alpha-half-life = 30 +/- 6 min, 85%; beta-half-life = 25.7 +/- 0.8 h, 15%). Abscess-to-background ratios, as derived from the region-of-interest analysis, increased to 34 +/- 7 at 24 h after injection. The images of both groups showed moderate uptake in the liver, spleen, kidneys, and bone marrow. No activity was seen in the bladder, indicating almost complete retention in the kidneys. The uptake in the abscess could be blocked completely by injection of an excess of nonradioactive agent, indicating a specific receptor-ligand interaction of the radiolabeled agent in the infected tissue. Biodistribution data showed that after saturation of the LTB(4) receptor, the abscess uptake, in percentage injected dose per gram, was significantly reduced (0.03 +/- 0.02 vs. 0.24 +/- 0.06, P = 0.008). CONCLUSION: The modified LTB(4) antagonist showed infectious foci rapidly after injection because of specific receptor-ligand interaction. Because of the high abscess-to-background ratios that were obtained and the fact that no accumulation of radioactivity was observed in the gastrointestinal tract, this compound has excellent characteristics for revealing infectious and inflammatory foci.

Biodistribution and pharmacokinetics of 111In-dTPA-labelled pegylated liposomes after intraperitoneal injection.

The biodistribution and pharmacokinetics of 111In-DTPA-labelled pegylated liposomes (IDLPL) and unencapsulated 111In-DTPA administered by the intraperitoneal (i.p.) and i.v. routes in non-tumour-bearing mice were compared. Mice received i.p. or i.v. injections of 0.37 MBq 111In-DTPA either encapsulated in liposomes or as an unencapsulated agent. A variety of tissues were dissected from 5 min to 192 h to determine the biodistribution and pharmacokinetics. Injection of IDLPL via the i.p. route caused a 74-fold increase in the area under the concentration (AUC) versus time curve in the peritoneum compared to unencapsulated 111In-DTPA. Similarly, the AUC for all the intra-abdominal tissues was increased significantly (20-427-fold). When i.p. IDLPLs were compared directly with i.v. IDLPLs, more modest changes were seen. There were increases in AUC for peritoneum (1.4-fold), ovary (1.3-fold), stomach (2.9-fold), pancreas (3.6-fold). small intestine (1.5-fold). colon (1.2-fold), gallbladder (5.1-fold) and adrenal gland (2.1-fold). These data support the development of i.p. liposomal chemotherapy for the treatment of intraperitoneal malignant disease.

Radiolabeled monoclonal antibodies specific to the extracellular domain of prostate-specific membrane antigen: preclinical studies in nude mice bearing LNCaP human prostate tumor.

UNLABELLED: Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein, is highly expressed by virtually all prostate cancers. PSMA is also expressed on the tumor vascular endothelium of virtually all solid carcinomas and sarcomas but not on normal vascular endothelium. PSMA is currently the focus of several diagnostic and therapeutic strategies. We have previously reported on the radiolabeling and in vitro binding properties of monoclonal antibodies (mAbs) (J415, J533, and J591) that recognize and bind with high affinity to the extracellular domain of PSMA (PSMA(ext)). This article reports on the in vivo behavior and tumor uptake of (131)I- and (111)In-labeled antiPSMA(ext) mAbs (J415, J533, and J591) and their potential utility for radioimmunotherapy. METHODS: In nude mice bearing PSMA-positive human LNCaP tumors, the pharmacokinetics, biodistribution, and tumor uptake of these antibodies was compared with (111)In-7E11 mAb, specific to the intracellular domain of PSMA (PSMA(int)). Autoradiographic studies were done to identify intratumoral distribution of radiolabeled mAbs. RESULTS: With (131)I-labeled antibodies, the net tumor retention of radioactivity by day 6 was significantly higher with J415 (15.4% +/- 1.1%) and 7E11 (14.5% +/- 1.7%) than with J591 (9.58% +/- 1.1%). By contrast, the tumor uptake of (111)In-1,4,7,10-tetraazacyclododecane-N,N',N", N"'-tetraacetic acid-labeled J415 and J591 gradually increased with time and was quite similar to that of 7E11. In addition, the blood clearance of (111)In-labeled J415 and J591 antibodies was relatively faster than that of radiolabeled 7E11. As a consequence, the tumor-to-blood ratios with J415 and J591 were higher than that of 7E11. The localization of radiolabeled anti-PSMA(ext) antibodies in PSMA-positive LNCaP tumors was highly specific because the tumor uptake of (131)I-labeled J415 and J591 was more than twice that of a nonspecific antibody. Furthermore, the tumor uptake of (131)I-J591 was almost 20 times higher in PSMA-positive LNCaP tumors than in PSMA-negative PC3 and DU145 tumor xenografts. Autoradiographic studies suggested that 7E11 (anti-PSMA(int)) distinctly favors localization to areas of necrosis whereas J415 and J591 (anti-PSMA(ext)) demonstrated a distinct preferential accumulation in areas of viable tumor. CONCLUSION: These results clearly demonstrate that PSMA-specific internalizing antibodies such as J415 and J591 may be the ideal mAbs for the development of novel therapeutic methods to target the delivery of beta-emitting radionuclides ((131)I, (90)Y, and (177)Lu) for the treatment of PSMA-positive tumors. In addition, because J591 and J415 mAbs are specific to PSMA(ext), thus targeting viable tumor, these immunoconjugates are better candidates for targeted radioimmunotherapy than are antibodies targeting PSMA(int).

Side-to-side symmetry of radioprotein transfer from tissue space to systemic vasculature following subcutaneous injection in normal subjects and patients with breast cancer.

Quantitative lymphoscintigraphy can be used for investigation of unilateral lymphatic disease of the limbs, such as breast cancer-related lymphoedema (BCRL). Previous studies have compared lymphatic function in the affected limb with that in the unaffected contralateral limb. This study aims to confirm that the assumption of pre-morbid symmetry, never previously demonstrated, is valid. A dual-isotope technique, with bilateral subcutaneous hand injection of polyclonal human immunoglobulin G (HIgG) labelled with either technetium-99m or indium-111, was performed on a total of 37 subjects. The use of two different labels, one for each limb, enabled comparison not only of the rate of clearance from the injection depot, but also of the rate of appearance in venous blood. Results demonstrate clear symmetry between the two arms with respect to both depot clearance and blood appearance rates, as well as the coupling between these two variables. In unilateral lymphatic disease, results of quantitative lymphoscintigraphy should be expressed in relation to the normal arm rather than to an independent control population.

Single-fraction irradiation has no effect on uptake of radiolabeled pegylated liposomes in a tumor xenograft model.

PURPOSE: These studies were performed with the intention of examining the effect of single-fraction doses of radiotherapy (RT) on the tumor deposition of radiolabeled pegylated liposomes in an animal xenograft tumor model. METHODS AND MATERIALS: Human KB head-and-neck xenograft tumors were established in female nude mice. The effect of single fraction tumor RT doses (5, 10, 15, and 20 Gy) on the tumor uptake of intravenously administered (111)In-DTPA-labeled pegylated liposomes (IDLPL) was examined using two protocols: (1) to test the effect of RT delivered 30 min before liposome injection on the time course of tumor uptake over a 96-h period; (2) to test the effect of RT at times ranging from 72-h to 1-h before liposome injection on the levels of liposome uptake at 24 h. Tumor and normal tissue/organ (blood, liver, spleen, lung, and kidney) liposome uptake was determined by dissection and quantitation in a gamma counter. RESULTS: There was no demonstrable effect of RT on tumor uptake of IDLPL (p > 0.1 for all comparisons). Reassuringly, neither was there an effect of RT on the pharmacokinetics and biodistribution of radiolabeled liposomes to normal tissues. CONCLUSIONS: Single fraction doses of RT appear to have no effect on tumor or normal tissue biodistribution and pharmacokinetics of radiolabeled pegylated liposomes in this animal model.