Leela P. Kasi

Phase I trial of murine monoclonal antibody 14G2a administered by prolonged intravenous infusion in patients with neuroectodermal tumors.

PURPOSE The purpose of this phase I trial was to determine the toxicity and maximum-tolerated dose (MTD) of murine monoclonal antibody (Mab) 14G2a (anti-GD2) in cancer patients. PATIENTS AND METHODS Following tracer doses of iodine-131-labeled 14G2a to determine tumor uptake, 18 patients with refractory melanoma, neuroblastoma, or osteosarcoma received unlabeled 14G2a at total concentrations of 50, 100, and 200 mg/m2 administered as daily 24-hour infusions for 5 days. RESULTS The overall sensitivity of external immunoscintigraphy was 64 of 74 known metastases (86%). Toxicity from prolonged infusion of 14G2a consisted of severe generalized pain, hyponatremia, fever, rash, paresthesias, weakness, and chronic refractory postural hypotension (two patients). Toxicity was less severe in pediatric patients. The MTD of Mab was 100 mg/m2. Sixteen of 18 patients developed human antimouse antibodies (HAMA) to 14G2a. Terminal-phase half-life (T1/2) of unlabeled Mab was 6.6 +/- 1.8 hours for patients receiving 50 mg/m2 and 39.5 +/- 13.3 hours at the 100-mg/m2 level. Tumor biopsies from six melanoma patients were positive for GD2 antigen, but only two of six had trace amounts of 14G2a present. Three mixed responses (two melanoma, one osteosarcoma) and two partial responses (PRs; neuroblastoma) were observed. CONCLUSION Mab 14G2a has modest antitumor activity at the expense of significant toxicity. Dose-limiting neurologic sequelae may significantly limit phase II studies other than in pediatric patients with neuroblastoma.

Technetium 99m-labeled IMMU-4, a monoclonal antibody against carcinoembryonic antigen, for imaging of occult recurrent colorectal cancer in patients with rising serum carcinoembryonic antigen levels.

PURPOSE We tested whether nuclear imaging with technetium 99m-labeled murine monoclonal antibody (MoAb) against carcinoembryonic antigen (CEA) IMMU-4 will detect recurrent colorectal disease in patients with a rising serum CEA level but negative abdominal and pelvic computed tomographic (CT) scan, chest radiograph, and colonoscopy, or barium enema. PATIENTS AND METHODS Sixteen patients with completely resected, CEA-producing colorectal cancer were given 1 mg of 99mTc-labeled IMMU-4 intravenously with no toxic side effects. Planar and single-photon emission CT (SPECT) scans were acquired at 6 hours. Fifteen patients underwent an exploratory laparotomy at 24 hours. Results of the scintigraphy were correlated with surgical findings. RESULTS Twelve of 15 patients (80%) had true-positive (TP) scans when correlated with surgery. Two of 15 (13%) had true-negative (TN) scans inasmuch as exploratory laparotomy failed to detect recurrent disease. A false-positive (FP) scan was obtained in one of 15 (7%). There were no false-negative (FN) scans. Sensitivity, specificity, accuracy, and the positive predictive value (PPV) were 100%, 67%, 93%, and 92%, respectively. Twenty-six histologically confirmed areas of malignancy were found and correlated with areas of increased activity seen on IMMU-4 scintigraphy. Twenty-one were TP; five were not detected by scintigraphy and were thus considered to be FN. There were five FP lesions and 25 TN regions. Sensitivity, specificity, accuracy, and the PPV in these 26 cancer tissues were 81%, 83%, 82%, and 81%, respectively. The median radioactivity ratio of tumorous tissue to normal tissue was 3.33, with a range of 0.89 to 17.16. CONCLUSIONS These results suggest that 99mTc IMMU-4 scintigraphy is an important addition to the armamentarium available for diagnostic imaging and may help detect occult metastatic cancer missed by abdominal and pelvic CT in patients with rising CEA levels.

Preliminary experimental evaluation of temporary segmental hepatic venous occlusion: angiographic, pathologic, and scintigraphic findings.

PURPOSE Pigs were used to evaluate temporary segmental hepatic venous occlusion as a means of improving the selective delivery of therapeutic agents within the liver. MATERIALS AND METHODS Hepatic angiography and scintigraphy were performed alone and in combination with hepatic venous occlusion. RESULTS Arteriograms obtained during venous obstruction demonstrated a greater number of peripheral arterial branches in the occluded area compared with the nonoccluded areas. A prolonged hepatogram showing hepatofugal opacification of the portal branches was observed in the occluded area. Microscopically, mild congestion of the sinusoids and central veins was seen immediately after 60-minute occlusion, but these changes were not evident 2 hours after balloon deflation. Severe congestion and focal hemorrhage were found in the occluded segment of the liver 2 hours after 90-minute venous occlusion. When the right or left hepatic vein was occluded during hepatic arterial infusion of technetium-99m macroaggregated albumin, there was a significant (P < or = .05) increase in the amount of radioactivity measured in the obstructed segment and a significant (P < or = .05) decrease in that found in the nonoccluded regions. CONCLUSION These results indicate that temporary segmental hepatic vein occlusion is safe for up to 60 minutes and may be clinically applicable as a means of improving the therapeutic index of agents within the liver when they are administered via concomitant hepatic arterial infusion.

Distribution and pharmacology of intravenous 99mTc-labeled multilamellar liposomes in rats and mice

Abstract The use of liposomes for the delivery of macrophage activators offers a new approach for the selective targeting of antitumor therapy. We have investigated the distribution, retention, and pharmacology of multilamellar liposomes (phosphatidylserine (PS): phosphatidylcholine (PC) 3:7) on i.v. injection in normal rats. Sprague-Dawley rats were injected with doses varying from 300 to 1000 mg/kg of 99m Tc-liposomes. The organ distribution of doses ranging from 300 to 500 mg/kg showed 45% mean uptake by liver, 25% by spleen, and 4% by lung. At higher doses of 800–1000 mg/kg, uptake in the lung increased significantly to 9 ± 3%. Whole body retention at 24 h after i.v. injection in Hale Stoner mice was 70%. The blood disappearance curve was biphasic and compared with the free isotope, a decrease was observed in the initial a phase t12 while the terminal phase t12 increased by 100%. These data suggest that encapsulation prolongs the initial distribution to the peripheral compartments and that higher doses may increase uptake by organs other than the liver.

Distribution of radiolabeled multilamellar liposomes injected intralymphatically and subcutaneously

The distribution of negatively charged multilamellar vesicles (MLV) composed of dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol administered subcutaneously (s.c.) and intralymphatically (i.l.) was studied in rats and dogs. In rats, the drainage of 99mTc-MLV from the s.c. space was slow, with 35% of the activity still remaining at the site of injection after 48 h and minimal systemic distribution (less than 5% at any time point). In the dog, 99mTc-MLV and 111In-MLV injected s.c. on the dorsal surface of a hindpaw were drained both by the lymphatic system and the systemic circulation; at 24 and 72 h, significant activity still remained at the site of injection. Lymphatic uptake was almost limited to the popliteal nodes and was enhanced by dividing the dose in several s.c. injections. Liver and kidney uptake was also observed, most likely as a result of direct liposome absorption into the systemic circulation. The i.l. administration (via left hindpaw) of 99mTc-MLV to a dog resulted in an immediate uptake in the abdominal and mediastinal lymph nodes, and in the liver and spleen. Compared with small unilamellar vesicles, MLV injected s.c. can provide a slower and more prolonged delivery of drugs to the regional lymph nodes.

Phase II radioimmunotherapy trial with131I-CC49 in colorectal cancer

Background. Radiolabeled CC49, a second generation high affinity monoclonal antibody (MoAb) reactive with tumor‐associated glycoprotein 72 (TAG72) has undergone previous Phase I testing in patients with colon cancer. Based on this report, the authors treated 15 refractory metastatic colon cancer patients with 131I‐CC49 to determine its overall toxicity and the response to therapy of patients treated with it.

Radioimmunodetection of residual, recurrent or metastatic germ cell tumors using technetium-99 anti-(α-fetoprotein) Fab′ fragment

Purpose: The majority of patients with germ cell tumors are cured by multimodality therapy that consists of cisplatin-based chemotherapy and/or surgical resection. Serum tumor markers and conventional radiographs are utilized to stratify patients into treatment categories. Efforts to individualize chemotherapy or minimize surgical interventions without compromising outcome are important. Immunomedics (Morris Plains, New Jersey) developed an anti-(α-fetoprotein) (anti-AFP) monoclonal antibody IMMU-30 labeled with 15–20 mCi technetium-99, and the purpose of this study is to determine the sensitivity and specificity of radio-immunoscintigraphy using 99mTc anti-AFP antibody for the diagnosis of active germ cell tumors. Methods: A group of patients with germ cell tumors were enrolled in a non-prospective fashion and 48 AFP scans using 99Tc anti-AFP Fab′ fragment were obtained. At the time of the AFP scan, serum AFP was elevated in 40 measurements with a median level of 21 ng/ml (1.6–66, 210.0 ng/ml). AFP scans were obtained at the initial staging, during treatment, at relapse or at long-term follow-up and compared with conventional radiographs done within 4 weeks of the AFP scans. Results: An overall diagnostic sensitivity of 89% and specificity of 58% were obtained. Conclusions: AFP scanning appears useful and to be sufficiently sensitive to justify prospective studies comparing the procedure with conventional imaging.

Analysis of urine samples from metastatic bone cancer patients administered 153Sm-EDTMP

153Sm-EDTMP is currently undergoing clinical evaluation as a radiotherapeutic agent for the relief of pain associated with cancer metastatic to bone. These clinical studies have demonstrated biodistributions similar to those seen earlier in animals, namely, rapid clearance from blood, selective uptake in bone and in particular metastatic bone lesions. The radioactivity not deposited in bone is cleared through the kidneys into the urine. In this study, urine samples collected from 9 patients injected with 153Sm-EDTMP underwent complexation analysis via Pharmacia SP-Sephadex C25 cation exchange chromatography. The results showed 96.9 +/- 1.7% of the radioactivity in the urine to be present as a complex of 153Sm. An HPLC method was developed and it was demonstrated that different complexes of 153Sm could be separated. A non-radioactive analytical standard of the Sm-EDTMP chelate was synthesized, characterized and shown to have the same HPLC retention profile as the 153Sm-EDTMP drug product. HPLC analysis was performed on six urine samples and in each case a single radioactivity peak with an elution profile the same as that of a 153Sm-EDTMP standard was observed. These results indicate that the 153Sm-EDTMP chelate is excreted intact in the urine of patients.

Selective in vitro labeling of white blood cells using 99mTc-labeled liposomes

We describe a method by which endocytosis-based radiolabeling of WBC is achieved using 99mTc-liposomes of optimal size and charge, and of a composition that assures both in vitro (whole blood) and intracellular stability of the radiopharmaceutical. In our study, excellent in vitro stability of 99mTc-liposomes with 95% labeling efficiency was observed with >90% stability up to 6 h and a minimum of 85% after 24 h of incubation either in normal saline or serum. Total WBC labeling efficiency using 99mTc-liposomes determined by radio-thin layer chromatographic analysis was 30.6 +/- 2.21%, 20.89 +/- 1.31% for monocytes and 9.7 +/- 1.74% for polymorphonuclears. Negligible activity was bound to red blood cells. The procedure did not affect the cell viability and the separation of the free 99mTc-liposomes from the cells was done by centrifugation.

Detection of acute postoperative mediastinitis in mice using 99mTc-Liposomes

Andreopouos D, Kasi LP, Kim EE, et al. Detection of acute postoperative mediastinitis in mice using 99mTc-liposomes. Invest Radiol 2002;37:435–439. Rationale and Objectives. To evaluate the usefulness of size-modified 99mTc-labeled liposomes for the detection of acute postoperative mediastinitis in a mouse model. methods. Fourteen mice underwent low-neck collar incision and had sterile abscesses induced in mediastinum with turpentine. Ten of these animals were injected intravenously with anionic liposomes of 516 ± 20 nm containing poly(ethylene)glycol labeled with 99mTc; the remaining four mice were injected with 67Ga citrate and used as positive controls. In addition, eight mice either underwent the same surgical procedure but without turpentine (n = 4) or were not operated (n = 4). These were used as negative controls. Therefore, scintigraphy using 99mTc-liposomes was performed in eighteen and 67Ga citrate in four mice. Target area of interest was outlined, and target to background count density ratio and percentage-injected dose were measured. results. Significant accumulation of radiolabeled liposomes was observed at sites of inflammation within 1 hour in abscess-bearing animals. This correlated well with the findings of the lower quality (contrast) of 67Ga images at 24 and 48 hours. The radiopharmaceutical did not significantly accumulate in the mediastinum of negative control animals. conclusion. 99mTc-liposomes (size modified) may prove useful nonspecific agent for the early diagnosis of postoperativemediastinitis.