Biomedical subjects

R M Sharkey

Publications and source records attributed to R M Sharkey.

At least 55 records · Page 3Linked to original sources

PubMed1996

Clinical evaluation of tumor targeting with the anticarcinoembryonic antigen murine monoclonal antibody fragment, MN-14 F(ab)2.

BACKGROUND: The initial clinical experience with the second-generation, high-affinity, MN-14 immunoglobulin (IgG) anticarcinoembryonic antigen (CEA) monoclonal antibody (MoAb) in patients with CEA-producing tumors was reported previously. A bivalent fragment of this MoAb, MN-14 F(ab)2, was prepared, and its pharmacokinetics, targeting properties, dosimetry, and immunogenicity were investigated. METHODS: MN-14 F(ab)2(0.6-29 mg) was labeled with 131I(7.7-269 millicuries and injected into 28 patients with CEA-producing cancers. External scintigraphy was used to evaluate tumor targeting. Quantitative external scintigraphy methods were used to determine the organ and tumor radiation doses. RESULTS: The overall sensitivity of tumor targeting on a lesion basis was 86%, similar to that reported previously for MN-14 whole IgG. The biologic T1/2's for the fragment in the blood and total body (in hours) were 16.8 +/- 4.1 and 59.4 +/- 9.4, respectively, compared with 27.3 +/- 15.7 and 69.6 +/- 32.2 reported for MN-14 IgG. Depending on the protein dose given, high plasma CEA levels (>100ng/ML) resulted in a significant alteration of MoAb pharmacokinetics and organ dosimetry. Individual tumors received an average dose of 10.7 +/- 7.3 centigray [cGy]/mCi, and the tumor-to-total body, red marrow, lung, liver, and kidney dose ratios were 16.8 +/- 11.1, 5.6 +/- 3.6, 5.1 +/- 3.9, 6.0 +/- 3.8, and 3.1 +/- 2.0, respectively (mean + standard deviation [SD]). Only 9 of 18 patients (50%) injected with >4 mg (range: 4-52.1 mg) of MN-14 F(ab)2 developed significant levels of human antimouse antibodies, suggesting that the F(ab)2 may be less immunogenic than the intact IgG. CONCLUSIONS: MN-14 F(ab)2 exhibits a similar targeting sensitivity and tumor dose as reported previously for the IgG form. The lower red marrow doses combined with lower immunogenicity expected for this agent, may make it a suitable alternative for future imaging and therapeutic applications.

Adolescent↗

PubMed1996

Factors influencing the pharmacokinetics, dosimetry, and diagnostic accuracy of radioimmunodetection and radioimmunotherapy of carcinoembryonic antigen-expressing tumors.

The aim of this study was to examine factors that may influence the pharmacokinetics, diagnostic accuracy, and dosimetry in radioimmunodetection and radioimmunotherapy with anti-carcinoembryonic antigen (CEA) monoclonal antibodies (mAbs). Data from 275 patients with CEA expressing tumors were analyzed retrospectively. Of these, 69 patients devoid of human antimouse antibody (i.e., 31 colorectal, 9 lung, 7 breast, 4 ovarian, 6 pancreatic, 9 medullary thyroid, 1 gallbladder, and 1 salivary gland cancer, and 1 primary tumor of unknown origin) underwent a low-protein-dose diagnostic study (0.3-2.6 mg of protein; 6.8-28.8 mCi 131I-labeled IgG or fragments), followed within 4 weeks by a high-protein-dose therapy injection (4.0-27.5 mg of protein; 29.8-238.9 mCi). The anti-CEA antibodies NP-4 (Ka=10(8)M-1) and MN-14 (ka=10(9)M-1) were used. Plasma clearance, the molecular composition of radioactivity in the plasma, and the cumulated activity in organs and tumors were determined. Radiation doses were derived from the Medical Internal Radiation Dose scheme. At a low-protein dose and over a similar range of plasma CEA, a significantly higher percentage of MN-14 than of NP-4 was complexed with circulating CEA, consistent with its higher affinity. Complexation was reduced with increasing protein doses. However, the targeting sensitivity was not affected. Profound differences were found in the clearance of the antibody between different types of cancer. Colorectal cancer patients cleared the antibody significantly faster from blood (T1/2=17.6+/-12.6 versus 44.2 +/- 23.7 h) and whole body (t1/2= 53.2 +/- 30.1 versus 114.6+/-59.7 h) than all other tumor types (P <0.001). Consequently, significantly lower red marrow (2.1 +/- 1.0 cGy/mCi versus 4.3 +/- 1.6 cGy/mCi) and whole-body doses (0.5 +/- 0.3 cGy/mCi versus 1.0 +/- 0.4 cGy/mCi) were seen in colorectal cancer patients as compared with other tumor types (P < 0.001). This clearance is probably due to hepatic metabolism of the immune complexes. Clearance rates were especially high in patients with colorectal cancer having large liver metastases and elevated liver enzymes (rapid hepatic clearance with liberation of free I-). In contrast, a disease-stage and plasma CEA-matched cohort of colorectal cancer patients, examined with the 131 I-labeled anti-colon-specific antigen p mAb Mu-9, showed normal murine IgG pharmacokinetics (n=22;3 of them compared intraindividually to MN-14). Only in colorectal cancer patients did complexes between mAb and CEA tend to clear rapidly, whereas Mu-9 had normal kinetics in these patients. This suggests that different CEA-expressing cancer types may produce heterogeneous CEA molecules and that the variability in mAb clearance is due to varying clearance rates of these different circulating CEA subspecies. Disease-related alterations in antibody metabolism are unlikely, given that only anti-CEA antibodies exhibit this phenomenon.

Adolescent↗

PubMed1996

Thyroid radiation doses during radioimmunotherapy of CEA-expressing tumours with 131I-labelled monoclonal antibodies.

A number of radioimmunotherapy (RAIT) trials with iodinated antibodies have shown a high variability in the radiation doses to the thyroid. Therefore, the aim of this study was to evaluate which factors influence these thyroid doses during RAIT with 131iodinated monoclonal anti-carcinoembryonic antigen (CEA) antibodies. Data from 36 patients with CEA-expressing tumours were analysed. The patients underwent RAIT with the 131I-labelled IgG1 anti-CEA antibody, MN-14 (Ka = 10(9) l mol-1) or its F(ab')2 fragment (activity range 45.8-220.0 mCi). The thyroid was blocked with 120 mg iodine (lugol's orSSKI solution) and 400 mg perchlorate per day, starting 1 day prior to the first study. Blood clearance and molecular composition of labelled plasma compounds were determined by blood sampling and size-exclusion high-performance liquid chromatography analysis. The cumulated activities of tissues were determined from daily imaging and blood clearance data. Doses were derived from the MIRD scheme. Thyroid radiation doses showed a high variability, between 1.2 and 37.7 cGy mCi-1 (mean +/- S.D.: 11.1 +/- 8.3 cGy mCi-1), corresponding to absolute doses between 2.5 and 43.6 Gy. However, the maximal iodine uptake in the thyroid was 2.4 +/- 1.9 microCi mCi-1 (range 0.2-10.0 microCi mCi-1), which was less than 1% of the injected activity, indicating that more than 99% of the thyroid was blocked in all cases. No correlation was found between these thyroid doses and conditions leading to an enhanced exposure to free radioiodine, such as unbound I- in the mAb preparation, rapid metabolic breakdown of the labelled antibody due to human anti-mouse antibodies (HAMA), or immune complex formation with circulating antigen. However, a relationship between the thyroid doses and the patients' compliance in taking their Lugol's and perchlorate blocking medications, as well as to a relatively high variability in the biological half-life of the iodine in the thyroid (range from 31.1 h to virtual infinity), is indicated. No rising TSH titres or other signs of (latent) hypothyroidism were seen in these patients during a 2 year follow-up period. Longer follow-up was not possible because of the terminal condition of most of the patients. These data show that thyroid doses in an appropriately blocked individual given a standard, non-myeloablative dose of RAIT, are generally lower than those assumed to be required to cause late hypothyroidism. Even if higher activities are used, potential hypothyroidism may be overcome easily by hormone replacement. Thyroid doses are independent of parameters leading to an enhanced exposure of the thyroid to free radioiodine, suggesting that patient compliance in taking their blocking medication may be the most crucial factor for reducing thyroid doses in RAIT with 131I-labelled antibodies.

Adenocarcinoma↗

PubMed1996

Improved detection of medullary thyroid cancer with radiolabeled antibodies to carcinoembryonic antigen.

PURPOSE: This investigation was undertaken to assess the targeting of established and occult medullary thyroid cancer (MTC) with radiolabeled monoclonal antibodies (MAbs) reactive with carcinoembryonic antigen (CEA). PATIENTS AND METHODS: Twenty-six assessable patients with known (n = 17) or occult (n = 9) MTC were studied with radiolabeled anti-CEA MAbs. Scintigraphic images were collected to determine targeting of tumor lesions. RESULTS: The targeting results of technetium 99m (99mTc)-,iodine 123 (123I)-, and iodine 131 (131I)-labeled anti-CEA antibodies (all directed against the same epitope of CEA) indicated that all these reagents were capable of detecting established and occult MTC. The sensitivity for detection of known sites of disease ranged from 76% to 100% for the various anti-CEA MAbs used, when compared with computed tomography (CT), magnetic resonance imaging (MRI), bone scan, or other imaging modalities. Moreover, the antibody scan was positive in seven of nine patients with occult disease (patients with negative conventional imaging studies, but who had elevated calcitonin and/or CEA levels). Three of seven patients underwent surgery and the disease was confirmed by histopathology in all three. CONCLUSION: Anti-CEA MAbs are excellent agents for imaging recurrent, residual, or metastatic MTC. The high lesion sensitivity in patients with known lesions, combined with the ability to detect disease, may make these agents ideal for staging patients, monitoring disease pretherapy or posttherapy, and especially for evaluating patients with recurrent or persistent hypercalcitonemia or CEA elevations after primary surgery. Analogous to radioiodine in the evaluation of patients with differentiated thyroid cancer, radiolabeled anti-CEA MAbs may achieve a similar role in diagnosing and monitoring patients with MTC.

Carcinoembryonic Antigen↗

PubMed1996

Radioimmunotherapy of medullary thyroid cancer with iodine-131-labeled anti-CEA antibodies.

UNLABELLED: This study evaluates the pharmacokinetics, dosimetry, toxicity and therapeutic potential of radiolabeled NP-4 and MN-14 anti-CEA antibodies in medullary thyroid cancer (MTC). METHODS: Eighteen patients with advanced MTC entered exploratory clinical studies with therapeutic doses of 131I-labeled NP-4 and MN-14 murine monoclonal antibodies (MAbs) reactive with carcinoembryonic antigen (CEA). Doses administered ranged from 46 mCi for 131I-MN-14 lgG to 195 mCi for 131I-MN-14 F(ab)2 in patients negative for human anti-mouse antibodies (HAMA). RESULTS: The radioconjugate blood half-life (T1/2) for the whole lgG was 42.5+/-5.0 hr compared to 18.8+/- 4.1 hr for the bivalent fragments. Tumor doses of 17.5+/-11.0 and 11.4+/-6.3 cGy/mCi were estimated for 131I-MN-14 lgG and F(ab)2, respectively. Tumor/red marrow dose ratios exceeded 3:1 for most lesions. Red marrow doses of up to 350 cGy generally could be delivered with < grade 4 toxicity. Seven of 14 evaluable patients showed evidence of anti-tumor effects lasting up to 26 months, based on physical exam, tumor markers or computed tomography. CONCLUSION: This study demonstrates that anti-CEA MAbs may be suitable for radioimmunotherapy of metastatic or recurrent MTC.

Adolescent↗

PubMed1996

Radioimmunotherapy of patients with small-volume tumors using iodine-131-labeled anti-CEA monoclonal antibody NP-4 F(ab')2.

UNLABELLED: The clinical feasibility of radioimmunotherapy (RIAIT) was assessed in patients with metastatic, carcinoembryonic antigen (CEA)-producing cancers who had minimal residual or small-volume disease (tumor lesions < or = 3 cm in diameter). METHODS: Thirteen cancer patients (8 colorectal, 3 lung, 1 pancreatic and 1 medullary thyroid cancer) received RAIT with 131I-NP-4 F(ab')2 anti-CEA antibody. The radioactive dose given was based on a prescribed radiation dose to the red marrow. Ten of the 13 patients received initial therapeutic doses delivering 150-450 cGy to the red marrow (70-296 mCi) and six patients had more than one therapy infusion. RESULTS: Targeting of all known tumor lesions < 0.5 cm [corrected] in diameter was possible in nine patients and at least one tumor lesion was evident in all patients. Disease stabilization ranging from 3.5 to 7 mo was seen in 6 of the 13 patients who previously had clear evidence of progressive disease. Four of the six patients with disease stabilization received the presumed maximum tolerated dose of 450 cGy to the red marrow. Red marrow suppression was the only observed toxicity and there was a good correlation between the red marrow dose and myelotoxicity. Red marrow doses < or = 250 cGy resulted in < or = grade 2 myelotoxicity and a red marrow dose of 450 cGy resulted in reversible grade 3 or 4 myelotoxicity in 3 of 6 patients. Human anti-mouse antibodies (HAMA) developed in all but one of the six patients who received multiple therapeutic infusions of the antibody. CONCLUSION: RAIT of patients with small-volume disease is feasible and these patients should be considered for future dose-intensification trials because of their generally poor prognosis.

Adult↗

PubMed1996

Reduction of renal uptake of monoclonal antibody fragments by amino acid infusion.

UNLABELLED: The renal uptake of radiolabeled antibody fragments and peptides presents a problem in radioimmunodetection and therapy, compromising lesion sensitivity, especially with intracellularly-retained isotopes. Previously, we showed that cationic amino acids and their derivatives are capable of significantly reducing kidney uptake in animals. We report our initial clinical results of successful renal uptake reduction in five patients who underwent cancer radioimmunodetection with 99mTc-anti-CEA Fab' fragments. METHODS: The patients were infused with two liters of a commercially-available nutritive amino acid solution (containing approximately 2.25 g/liter lysine-glutamate and 2.50 g/liter arginine), whereas 75 control patients received the same volume of saline (quantification of organ and tumor kinetics from conjugate whole-body views by ROI technique). RESULTS: The renal uptake in the amino acid group was significantly lower (p<0.05) than in the control group (11.1 +/- 2.0% injected dose versus 17.7 +/- 7.0% injected dose at 24 hr postinjection), whereas the uptake of all other organs remained unaffected. Gel filtration chromatography of the urine taken from amino-acid-treated patients showed that a significantly higher amount of excreted activity was bound to intact Fab' (53% of excreted activity) in contrast to only less than 10% in the control group. CONCLUSION: The renal uptake of monoclonal antibody fragments in patients can be reduced significantly by amino acid infusion, even at considerably lower doses than those that were safe and effective in animals. As was found in animals, the mechanism seems to rely on an inhibition of the re-absorption of tubularly-filtered proteins by the proximal tubule cells. These results encourage further clinical trials to lower the renal uptake experienced in radioimmunodetection, as well as in therapeutic trials with antibody fragments and peptides.

Aged↗

PubMed1995

Estimates of red marrow dose by sacral scintigraphy in radioimmunotherapy patients having non-Hodgkin's lymphoma and diffuse bone marrow uptake.

According to the recommendations of the Dosimetry Task Group of the American Association of Physicists in Medicine, blood-derived estimates of the red marrow (RM) dose from radiolabeled monoclonal antibodies (MAbs) are valid only if the RM is devoid of any specific uptake. There is, therefore, a clear need for an alternative method for estimating the RM dose in patients receiving MAbs that target normal or abnormal (malignant) bone marrow elements. Radiolabeled LL2, an anti-B-cell murine MAb, targets normal B cells and malignant lymphoma cells in the RM. This may result in an increased radiation dose to the RM through neighboring targeted activity. We investigated whether imaging-based estimates of the RM dose, particularly using sacral scintigraphy, correlate with myelotoxicity in non-Hodgkin's lymphoma patients who received 131I-LL2. The sacrum-based RM dose (RMs) was estimated from sacral activity by assuming that 9.9% of the total adult RM is contained in the sacrum. The sacrum was not used if there was focally increased or decreased sacral uptake. Myelotoxicity was assessed based on Radiation Therapy Oncology Group criteria. Twelve of 21 non-Hodgkin's lymphoma patients treated had adequate imaging, dosimetry, and follow-up to evaluate myelotoxicity. Eight of these patients had diffusely increased RM uptake on their MAb scans. The average estimated RMs in the eight patients was 168 +/- 62 cGy (mean +/- SD) with only 50 mCi 131I-LL2. Six of these patients (75%) developed grade 3 or 4 myelotoxicity. In contrast, the average RMs in the four patients who did not have any enhanced uptake on their scans was 71 +/- 30 cGy (P < 0.02). None of these patients developed grade 3 or 4 toxicity. These results suggest that image-based estimates of the RM dose may be predictive of myelotoxicity and should be used in patients with diffuse RM uptake on their scans.

Antibodies, Monoclonal↗

PubMed1995

Treatment of non-Hodgkin's lymphoma with radiolabeled murine, chimeric, or humanized LL2, an anti-CD22 monoclonal antibody.

LL2 is a murine IgG2a anti-CD22 monoclonal antibody found to react with virtually all non-Hodgkin's lymphomas (NHLs). Twenty-one patients with chemotherapy-resistant NHL received nonmyeloablative doses of 131I-labeled LL2 IgG and F(ab')2 ranging from 15 to 343 mCi given in cycles of 15-50 mCi, for up to seven treatment cycles. The cumulative protein dose ranged from 1.1 mg IgG to 157 mg F(ab')2. Seventeen patients were assessable for treatment response, and antitumor effects were seen in five (one complete remission, two partial remissions, and two minor or mixed responses). In addition, one complete response was seen in a patient who received only "diagnostic" doses of 131I-LL2 IgG. Thus, a total of six patients had responses according to the defined response criteria. Three additional patients have been treated with potentially myeloablative doses of 131I-LL2 IgG at a starting dose level of 90 mCi/m2 (100 mg). Two patients were evaluable, and both had partial remissions lasting 8 and 3 months, respectively. Chimeric and complementarity-determining region-grafted LL2 have been developed. Initial clinical studies have shown that these agents have targeting properties similar to the murine LL2 and, therefore, may be suitable alternatives to murine LL2 in the treatment of NHL. LL2 is a promising agent for the treatment of lymphoma, particularly when the maximum tolerated dose is given either with or without autologous bone marrow transplantation.

Adult↗

PubMed1995

Evaluation of a complementarity-determining region-grafted (humanized) anti-carcinoembryonic antigen monoclonal antibody in preclinical and clinical studies.

A complementarity-determining region-grafted (humanized) version of MN-14 (hMN-14), a high-affinity, anti-carcinoembryonic antigen (CEA) murine monoclonal antibody (mMAb), was selected from several clones that differed slightly in their framework composition. One clone was selected based on its similar binding affinity to CEA as that observed with mMN-14 MAb and its production yields. Targeting studies, using 131I-labeled humanized MN-14 (hMN-14)/125I-labeled mMN-14 IgG in GW-39 tumor-bearing nude mice, showed excellent tumor uptake and tumor: nontumor ratios, similar to the mMN-14. A pilot clinical imaging trial was initiated to determine the targeting, pharmacokinetics, and dosimetry for 131I-labeled hMN-14 IgG. Nineteen patients with advanced CEA-producing tumors were given 8 to 30 mCi (0.5 to 20.0 mg). Eleven patients also received 131I-labeled mMN-14 IgG for comparison. The biodistribution, tumor targeting, and pharmacokinetic behavior of the hMN-14 was similar to that seen with the mMN-14. The average time required to clear 50% of the radiolabeled hMN-14 from the blood and total body was 32.9 +/- 25.6 h and 109 +/- 73 h, respectively. Patients with elevated plasma CEA (i.e., > 200 ng/ml) had more than 30% of the labeled antibody complexed within 1 h after injection. In some of these patients, increased complexation resulted in enhanced metabolism of the antibody with more rapid clearance from the blood than that seen in patients with lower plasma CEA. The average radiation absorbed dose measured in 20 tumors (average weight, 204 +/- 205 g) in 14 patients was 7.6 +/- 5.3 cGy/mCi. Tumor: nontumor dose ratios were 2.5 +/- 1.6, 9.5 +/- 5.8, and 2.6 +/- 1.8 for the red marrow, total body, and liver, respectively. One patient, with a highly elevated human anti-mouse antibody response from a prior OncoScint study (murine B72.3 IgG), received 3 injections of the hMN-14 without an adverse experience, and showed no evidence of altered biodistribution characteristic of mMAb-human anti-mouse antibody interactions. An antibody response to hMN-14 (HAhMN14) was not detected in patients who received only the hMN-14 (as many as three injections), but in three patients who received two injections of the mMN-14, a HAhMN14 response was detected. With similar, excellent targeting properties as the mMN-14 and the potential for reduced immunogenicity, hMN-14 is an attractive candidate for further clinical imaging and therapy applications.

Adult↗

PubMed1995

Targeting and initial radioimmunotherapy of medullary thyroid carcinoma with 131I-labeled monoclonal antibodies to carcinoembryonic antigen.

The targeting potential of 131I-labeled NP-4 and MN-14 anti-CEA (carcinoembryonic antigen) monoclonal antibodies (MAbs) was assessed in 19 patients with metastatic medullary thyroid cancer (MTC). Seventeen of these patients also entered pilot radioimmunotherapy studies with nonmyeloablative doses of 131I-anti-CEA MAbs. Tumor targeting was possible in all 19 patients, with an overall lesion sensitivity of 91%. Tumor dosimetry with 131I-MN-14 IgG or F(ab)2 was very favorable, with tumor doses of 14.3 +/- 8.3 cGy/mCi and tumor:red marrow dose ratios exceeding 3:1 for most lesions. Limited antitumor effects lasting up to 26+ months, based on physical exam, tumor markers, computed tomography, or a followup MAb scan, were seen in 5 of 11 assessable patients given relatively low doses of 131I-labeled anti-CEA MAbs. We conclude that anti-CEA MAbs are excellent agents for targeting metastatic MTC. The high tumor uptake of the 131I-anti-CEA antibodies and evidence of tumor response in some patients suggest that radioimmunotherapy with radioiodinated anti-CEA MAbs may be an effective treatment for MTC, particularly when the maximum tolerated dose is given alone or in combination with autologous red marrow or peripheral stem cell support.

Animals↗

PubMed1995

Reduction of the renal uptake of radiolabeled monoclonal antibody fragments by cationic amino acids and their derivatives.

The renal uptake of radiolabeled antibody fragments and peptides is a problem in radioimmunodetection and radioimmunotherapy, especially with intracellular retained radiometals. The aim of this study was to develop suitable methods to reduce this kidney uptake. BALB/c mice or nude mice bearing the human GW-39 colon carcinoma xenograft were given i.p. injections of basic amino acids or a range of different basic amino acid derivatives, amino sugars, as well as cationic peptides. The effect of these agents on the biodistribution of Fab' and F(ab')2 fragments of different mAbs radiolabeled with 99mTc, 188Re, 111In, 88Y, or 125I was studied. Tumor and organ uptake was determined and compared to untreated mice. The kidney uptake of Fab' fragments was reduced 5-6-fold in a dose-dependent manner as compared to untreated controls. The uptake in all other organs, as well as the tumor, was unaffected. A similar reduction in renal retention was seen for all other intracellularly retained isotopes, as well as for F(ab')2 fragments. D- and L-isomers of lysine were equally effective whether given i.p. or p.o. D-glucosamine was effective, but its N-acetyl derivative was not. Basic polypeptides (e.g., poly-L-lysine) were also effective; their potency increased with increasing molecular weight. HPLC of the urine taken from treated animals showed the excretion of intact Fab', in contrast to mostly low-molecular-weight metabolites in the control group. These studies indicate that a variety of basic compounds is capable of inhibiting the tubular reabsorption of peptides and proteins, thus lowering the kidney uptake of antibody fragments significantly. On a molecular basis, the effect seems to essentially rely on the presence of a positively charged amino group. By reducing renal retention of antibody fragments, their role as imaging and therapeutic agents may be expanded.

Animals↗

PubMed1995

Quantitative and qualitative effects of experimental radioimmunotherapy on tumor vascular permeability.

Localization of radiolabeled antibodies in the perivascular space of tumors resulted in morphological changes in blood vessel structure and physiological changes in tumor vessel function. Vessel diameter decreased by day 14 and was associated with a significant decline in vascular volume (VV). Upon recovery of VV, the basement membrane surrounding the endothelium had thickened. Tumor vascular permeability (VP) decreased within 7 days of treatment and remained suppressed throughout the 42-day observation period of our study. The decline in VP, which could be visualized by fluorescent microscopy of FITC-dextran extravasation, was dose-related and could be quantified at doses as low as 800 cGy. The radioantibody-induced 50-80% decline in tumor VP was observed in 3 human colonic xenografts (GW-39, LSI74T and MOSER). Decreases in VP have been observed for proteins ranging in size from 20 to 150 kDa. Similar effects on VP were noted when low protein doses (10-30 micrograms), which resulted in heterogeneous antibody distribution, were used or with high protein doses (400-750 micrograms), which resulted in more uniform penetration of antibody. If 188Re or 90Y, radiometals with higher beta-energy and longer path lengths, were substituted for 131I, a similar decrease in VP was observed. The radioimmunotherapy (RAIT)-induced decrease in tumor VP resulted in a 90% decline in accretion of a second dose of radioantibody. The 10% of the second dose that was taken up by the tumor targeted many already non-viable tumor regions and some, but not all, viable tumor cell clusters.

Adenocarcinoma↗

PubMed1995

Targeting of xenografted pancreatic cancer with a new monoclonal antibody, PAM4.

We have examined the ability of murine monoclonal antibody PAM4, directed against a pancreatic cancer-derived mucin, to target human pancreatic cancers carried as xenografts in athymic nude mice. Four tumor lines were used representing the range of expected differentiation; CaPan1, AsPc1, Hs766T, and BxPc3. In each case tumor uptake of PAM4 (range, 21-48% injected dose/g on day 3) was significantly higher than concomitantly administered, nonspecific, isotype-matched Ag8 antibody (range, 3.6-9.3% injected dose/g on day 3). Based upon the biodistribution data the estimated potential radiation dose delivered to the tumors when normalized to the blood dose as an estimate of dose-limiting myelotoxicity would be 13.1-, 2.2-, 3.4-, and 3.3-fold higher than to blood, respectively. PAM4 showed no evidence of targeting to normal tissues, except within the CaPan1 tumor model, where a small but consistent splenic uptake was observed. Splenic targeting was abolished by use of an increased PAM4 protein dose. Targeting of PAM4 to other normal tissues was not affected by the increased protein dose; however, tumor uptake of PAM4 (percentage of injected dose/g) was significantly increased by as much as 3-fold. The ability of PAM4 to target the CaPan1 tumor compared favorably to that of MN14, an anti-carcinoembryonic antigen murine monoclonal antibody. Tumor uptake of PAM4 was much greater than that for MN14 at days 1 and 3, whereas at later time points equivalent accumulations of activity were noted. Estimates of potential radiation doses to the tumor when normalized to the blood dose were 3.0 for MN14 and 9.6 for PAM4. These studies have shown that PAM4 is able to target pancreatic cancer with high specificity, achieving high concentrations at the tumor site. A rationale exists, then, for the performance of a clinical trial of radiolabeled PAM4 in the detection and localization of pancreatic cancer.

Animals↗

PubMed1995

Improved experimental cancer therapy by radioantibody dose intensification as a result of syngeneic bone marrow transplantation.

Myelosuppressive toxicity is dose-limiting for radioimmunotherapy. We have reported on the use of cytokine intervention (rhIL-1 and rmGM-CSF) to stimulate differentiation of progenitor cells and reduce radioantibody-induced leukopenia and thrombocytopenia (J. Natl. Cancer Inst. 84:399, 1992; Cancer 73:1073, 1994). As an alternative to the use of cytokines, we investigated the effect of syngeneic bone marrow transplantation on the ability to dose-escalate radioantibody. Injection of 10(7) bone marrow cells from a donor mouse 6 to 8 days after a 340- to 360-microCi dose of radioantibody (LD100/28)--a 25 to 30% increase above the maximal tolerated dose--resulted in 100% survival. This observation is associated with a recovery in neutrophil and thrombocyte counts within 21 days of therapy (normal recovery after 275 microCi takes 42 days). None of the mice survived when BMT was done at either 4 or 11 days after radioantibody. Marrow from normal donor mice was more effective than that from cytokine-primed mice whose marrow cells were actively cycling after a 5-day course of IL-1/GM-CSF. The combination of the two myeloprotective approaches, BMT plus a 14-day schedule of IL-1 (2 x 10(3) U/d) and GM-CSF (1 microgram/d) intervention, provided a greater stimulation of peripheral WBC counts than either approach alone; however, further dose escalation under these conditions was not feasible. The 30% intensification in radioantibody dose offers a therapeutic advantage for both bulky disease (GW-39 subcutaneous nude mouse model) and micrometastatic disease (GW-39 intrapulmonary model). In the bulky tumor model, the increase in administered dose resulting from BMT extends the 8-week growth delay observed at 275 microCi 131I-MN-14 IgG by an additional 7 weeks. In the metastatic model, dose intensification increased median animal survival from 15 to 23 weeks. Therefore, by optimizing the use of BMT, a greater therapeutic benefit can be derived from radioantibody therapy in a solid tumor model. This study represents a proof of principle, that BMT can be effective for low-dose-rate therapy as it has been for short-duration intense chemotherapy and radiation therapy. It also highlights several important issues to consider when attempting to apply the method in the clinic.

Animals↗

PubMed1995

Rat adjuvant arthritis: imaging with technetium-99m-anti-CD4 Fab' fragments.

UNLABELLED: The abundance of CD4 molecules on inflammatory cells in the synovial membrane renders anti-CD4 monoclonal antibodies (MAbs) or their fragments very promising for specific imaging of arthritic joints. METHODS: Joint uptake and body distribution of a 99mTc-labeled Fab', derived from the anti-rat CD4 MAb W3/25 (IgG1), were investigated following intravenous injection in normal and adjuvant arthritic rats. An isotype-matched Fab' (anti-human nonspecific crossreacting antigen-90) was used as control. RESULTS: A 14-hr sequential pinhole scan of the ankle joints revealed that both the anti-CD4 and the control Fab' accumulated to a higher degree in arthritic than in normal ankle joints; however, accumulation of the anti-CD4 Fab' in arthritic joints exceeded that of the control Fab' (approximate to 1.6 fold). Preferential joint accumulation of anti-CD4 Fab' was confirmed by whole-body scans at 14 hr and by direct well counter measurements of tissue samples at 16 hr following injection. Unlike the control Fab', the anti-CD4 Fab' preferentially accumulated in the liver and lymph nodes, organs rich in CD4-positive cells, as observed by direct tissue measurements. CONCLUSION: Despite its monovalency, the anti-CD4 Fab' retains the in vivo selectivity for CD4-positive cell-rich tissues, previously reported for the complete anti-CD4 MAb, and improves imaging of inflamed joints in experimental adjuvant arthritis.

Animals↗

PubMed1994

Cytokine intervention permits dose escalation of radioantibody. An analysis of myelostimulation by bolus versus continuous infusion of IL-1/GM-CSF.

BACKGROUND: The authors recently reported that a 12-day schedule (beginning 3 days before radioantibody treatment) of twice-daily dosing of rH-IL-1 (1 x 10(3) U/dose) and rM-GM-CSF (0.5 micrograms/dose) can reduce the magnitude and duration of radioantibody-induced myelosuppression, thereby permitting a 25-30% increase in the dose of radioantibody that can be administered without the dose proving lethal. In an effort to further reduce toxicity and escalate the tolerated dose, the authors altered the method of administration of cytokines from daily bolus dosing to continuous infusion by implantable osmotic pumps. METHODS: A control group of mice was compared to five groups of mice that either did or did not receive a 340 microCi dose of radioantibody, and received no cytokines, cytokines by bolus dosing, or cytokines by continuous infusion. For 4 weeks, peripheral white blood cell and thrombocyte counts and thymus and spleen weights were taken, marrow cell number was monitored, and marrow colony-forming unit activity was evaluated weekly in the untreated control mice and the treated mice. RESULTS: These studies demonstrated that after a dose of radioantibody, continuous dosing of cytokines resulted in higher white blood cell (WBC) and platelet values than if bolus delivery was used (day 7, WBC: 110% vs. 59%; day 14, WBC: 85% vs. 62%; day 21, WBC: 98% vs. 42%; day 7, platelets: 122% vs. 51%; day 14, platelets: 159% vs. 72%; day 21, platelets: 239% vs. 171%). A comparison of bolus versus continuous dosing in the absence of radioantibody indicated that spleen weight increased by 40-60% after continuous infusion of cytokines and by 20-25% after bolus dosing. The 20-30% decrease in thymus weight was similar with both dosing regimens. Colony-forming units (CFUs) in marrow increased from 30-35 in untreated mice to 50-55 in mice given cytokines by bolus injection, and to 150-180 in mice given continuous infusion of cytokines. Spleen CFUs exhibited an insignificant increase after bolus dosing of cytokines but increased almost fourfold after continuous dosing. Peak stimulation of marrow and spleen CFUs occurred 28 days after initiation of cytokine administration (2 weeks after cytokines administration was stopped). The probability of survival for 6 weeks after further dose escalation to 360 microCi I-131-MN-14 immunoglobulin G was 16.4% +/- 8.6% after bolus dosing and 58.1% +/- 11.3% after continuous infusion of cytokines. CONCLUSIONS: Although continuous infusion of cytokines proved to be a better method of reducing hematopoietic toxicity, further dose escalation of radioimmunotherapy using the "pump" method of cytokine delivery was not possible. Cytokine intervention by either mode of delivery permits a 25% dose intensification without the dose becoming lethal. Further escalation is not feasible, possibly because of other end organ toxicity.

Animals↗

PubMed1994

Comparative biodistribution and radioimmunotherapy of monoclonal antibody RS7 and its F(ab')2 in nude mice bearing human tumor xenografts.

BACKGROUND: RS7 is a murine monoclonal antibody immunoglobulin G1 with pan-carcinoma reactivity, which was raised against human squamous cell carcinoma of the lung. To optimize the use of monoclonal antibody RS7 as a carrier of radionuclides for tumor targeting and therapeutic applications, whole RS7 immunoglobulin G and its F(ab')2 fragment were radiolabeled, and their biodistribution and effectiveness as radioimmunotherapeutic agents in nude mice bearing established human tumor xenografts were evaluated. The contributions of the tumor model, monoclonal antibody form (fragment vs. intact), radioisotope (131I, 111In, 90Y, and 188Re), and antigen target were evaluated. METHODS: Cumulative absorbed radiation doses were calculated from biodistribution data, and doses were normalized to blood to estimate expected relative toxicities. Two tumor models expressing different levels of RS7-antigen were studied: ME180, a cervical carcinoma cell line, and Calu-3, an adenocarcinoma of the lung cell line. In addition, the therapeutic effectiveness of 131I-RS7-F(ab')2 was compared to that of 131I-RS7-IgG. RESULTS AND CONCLUSIONS: Doses delivered to tumor (normalized to blood) calculated for 131I-RS7-F(ab')2 and 90Y-RS7-IgG were 4.7 times and 1.8 times greater, respectively, than 131I-RS7-IgG, and therefore would be expected to yield greater therapeutic efficacy when equitoxic doses are administered. This expectation was confirmed in the radioimmunotherapy study with 131I-RS7-F(ab')2. At equivalent absorbed dose to tumor, 131I-RS7-F(ab')2 was found to effect a slightly longer suppression of tumor growth than the intact 131I-RS7 IgG, and a 50% dose escalation yielded tumor regression for a prolonged period with the fragment, whereas a similar 50% dose escalation with 131I-RS7-IgG could not be tolerated.

Adenocarcinoma↗