Chaitanya R. Divgi

Preoperative characterisation of clear-cell renal carcinoma using iodine-124-labelled antibody chimeric G250 (124I-cG250) and PET in patients with renal masses: a phase I trial

BACKGROUND Preoperative identification of tumour type could have important implications for the choice of treatment for renal cancers. Antibody cG250 reacts against carbonic anhydrase-IX, which is over-expressed in clear-cell renal carcinomas. We aimed to assess whether iodine-124-labelled antibody chimeric G250 ((124)I-cG250) PET predicts clear-cell renal carcinoma, the most common and aggressive renal tumour. METHODS 26 patients with renal masses who were scheduled to undergo surgical resection by laparotomy received a single intravenous infusion of 185 MBq/10 mg of (124)I-cG250 over 20 min in this open-label pilot study. Surgery was scheduled 1 week after (124)I-cG250 infusion. PET and CT scanning of the abdomen, including the kidneys, within 3 h before surgery was planned for all patients. The obtained images were graded as positive (defined as a tumour-to-healthy-kidney ratio >3 to 1) or negative for antibody uptake, and the surgeon was informed of the scan results before surgery. After surgery, resected tumours were histopathologically classified as clear-cell renal carcinoma or otherwise. The trial is registered on the clinical trials site of the National Cancer Institute website http://clinicaltrials.gov/ct/show/NCT00199888. FINDINGS One patient received inactive antibody and was excluded from analysis. 15 of 16 clear-cell carcinomas were identified accurately by antibody PET, and all nine non-clear-cell renal masses were negative for the tracer. The sensitivity of (124)I-cG250 PET for clear-cell kidney carcinoma in this trial was 94% (95% CI 70-100%); the negative predictive value was 90% (55-100%), and specificity and positive predictive accuracy were both 100% (66-100% and 78-100%, respectively). INTERPRETATION PET with (124)I-cG250 can identify accurately clear-cell renal carcinoma; a negative scan is highly predictive of a less aggressive phenotype. Stratification of patients with renal masses by (124)I-cG250 PET can identify aggressive tumours and help decide treatment.

Phase I/II study of iodine 125-labeled monoclonal antibody A33 in patients with advanced colon cancer.

PURPOSE A phase I/II study was designed to determine the maximum-tolerated dose (MTD) of iodine 125-labeled monoclonal antibody A33 (125I-mAb A33), its limiting organ toxicity, and the uptake and retention of radioactivity in tumor lesions. PATIENTS AND METHODS Patients (N = 21) with advanced chemotherapy-resistant colon cancer who had not received prior radiotherapy were treated with a single 125I-mAb A33 dose. 125I doses were escalated from 50 to 350 mCi/m2 in 50-mCi/m2 increments. Radioimmunoscintigrams were performed for up to 6 weeks after 125I-mAb A33 administration. RESULTS All 20 patients with radiologic evidence of disease showed localization of 125I to sites of disease. Twelve of 14 patients, who underwent imaging studies 4 to 6 weeks after antibody administration, had sufficient isotope retention in tumor lesions to make external imaging possible. No major toxicity was observed, except in one patient with prior exposure to mitomycin who developed transient grade 3 thrombocytopenia. Although the isotope showed variable uptake in the normal bowel, gastrointestinal symptoms were mild or absent, and in no case did stools become guaiac-positive. The MTD was not reached at 125I doses up to 350 mCi/m2. However, cytotoxicity assays demonstrated that patients treated with the highest dose had sufficiently high serum levels of 125I-mAb A33 to lyse colon cancer cells in vitro. Among 21 patients, carcinoembryonic antigen (CEA) levels returned to normal in one patient and decreased by 35% and 23%, respectively, in two patients; one additional patient had a mixed response on computed tomography. Additional, significant responses were observed in those patients treated with chemotherapy [carmustine [BCNU], vincristine, flourouracil, and streptozocin [BOF-Strep]) after completion of the 125I-mAb A33 study. CONCLUSION Low-energy emission radioimmunotherapy with doses of up to 350 mCi/m2 of 125I-mAb A33 did not cause bowel or bone marrow toxicity. The modest antitumor activity in these heavily pretreated patients is encouraging because of lack of toxicity at the doses studied. The long radioactivity retention in tumors suggests that isotopes with a long half-life may have a therapeutic advantage, based on calculated dose delivery to tumor versus normal tissue. Due to the low bone marrow dose, further 125I trials with humanized mAb A33 are warranted, and controlled studies must be conducted to evaluate the combination of radioimmunotherapy and chemotherapy.

A phase I trial of monoclonal antibody M195 in acute myelogenous leukemia: specific bone marrow targeting and internalization of radionuclide.

Ten patients with myeloid leukemias were treated in a phase I trial with escalating doses of mouse monoclonal antibody (mAb) M195, reactive with CD33, a glycoprotein found on myeloid leukemia blasts and early hematopoietic progenitor cells but not on normal stem cells. M195 was trace-labeled with iodine-131 (131I) to allow detailed pharmacokinetic and dosimetric studies by serial sampling of blood and bone marrow and whole-body gamma-camera imaging. Total doses up to 76 mg were administered safely without immediate adverse effects. Absorption of M195 onto targets in vivo was demonstrated by biopsy, pharmacology, flow cytometry, and imaging; saturation of available sites occurred at doses greater than or equal to 5 mg/m2. The entire bone marrow was specifically and clearly imaged beginning within hours after injection; optimal imaging occurred at the lowest dose. Bone marrow biopsies demonstrated significant dose-related uptake of M195 as early as 1 hour after infusion in all patients, with the majority of the dose found in the marrow. Tumor regressions were not observed. An estimated 0.33 to 1.0 rad/mCi 131I was delivered to the whole body, 1.1 to 6.1 rad/mCi was delivered to the plasma, and up to 34 rad/mCi was delivered to the red marrow compartment. 131I-M195 was rapidly modulated, with a majority of the bound immunoglobulin G (IgG) being internalized into target cells in vivo. These data indicate that whole bone marrow ablative doses of 131I-M195 can be expected. The rapid, specific, and quantitative delivery to the bone marrow and the efficient internalization of M195 into target cells in vivo also suggest that the delivery of other isotopes such as auger or alpha emitters, toxins, or other biologically important molecules into either leukemia cells or normal hematopoietic progenitor cells may be feasible.

Antibody localization in human renal cell carcinoma: a phase I study of monoclonal antibody G250.

PURPOSE To define the imaging and biodistribution characteristics of iodine 131-labeled monoclonal antibody (mAb) G250 (131I-mAbG250), which recognizes a cell-surface antigen expressed by human renal cell carcinoma (RCC). PATIENTS AND METHODS G250 is a cell-surface antigen recognized by mAbG250 expressed by RCC but not detected in normal kidney. Clear-cell RCC, the most frequent form of RCC, shows homogeneous expression of G250, whereas non-clear-cell RCC and cancers derived from other organs generally do not express G250. Expression in normal tissues is highly restricted and limited to large bile ducts and gastric epithelium. 131I-mAbG250 was administered intravenously (IV) to 16 patients with RCC 7 to 8 days before surgery at five dose levels, with at least three patients entered at each dose level. RESULTS Clear tumor images were observed in 12 patients with G250-positive tumors and in one of three patients with G250-negative tumors. Imaged lesions in the peritoneal cavity were confirmed at surgery. The smallest lesion visualized was 8 mm in diameter. The specificity of 131I-mAbG250 localization to tumor tissue was established by radioactivity measurements, autoradiography, and immunohistochemistry of biopsied tissues, and technetium 99-human serum albumin blood-flow studies. The fraction of the injected 131I-mAbG250 dose per gram tumor (%ID/g tumor) localized in G250-positive tumors showed a broad range, but reached levels as high as 0.02% to 0.12%. CONCLUSION 131I-mAbG250 localized specifically to G250 antigen-positive RCC and seems to have considerable potential as an imaging agent in RCC patients. 131I-mAbG250 uptake in the tumors, relative as well as absolute, are among the highest reported for tumor biopsies obtained 8 days after IV mAb administration. Based on the specific localization and high accumulation, mAb G250 may have therapeutic potential.

Intraperitoneal α-Particle Radioimmunotherapy of Ovarian Cancer Patients: Pharmacokinetics and Dosimetry of 211At-MX35 F(ab')2—A Phase I Study

The α-emitter 211At labeled to a monoclonal antibody has proven safe and effective in treating microscopic ovarian cancer in the abdominal cavity of mice. Women in complete clinical remission after second-line chemotherapy for recurrent ovarian carcinoma were enrolled in a phase I study. The aim was to determine the pharmacokinetics for assessing absorbed dose to normal tissues and investigating toxicity. Methods: Nine patients underwent laparoscopy 2–5 d before the therapy; a peritoneal catheter was inserted, and the abdominal cavity was inspected to exclude the presence of macroscopic tumor growth or major adhesions. 211At was labeled to MX35 F(ab′)2 using the reagent N-succinimidyl-3-(trimethylstannyl)-benzoate. Patients were infused with 211At-MX35 F(ab′)2 (22.4–101 MBq/L) in dialysis solution via the peritoneal catheter. γ-camera scans were acquired on 3–5 occasions after infusion, and a SPECT scan was acquired at 6 h. Samples of blood, urine, and peritoneal fluid were collected at 1–48 h. Hematology and renal and thyroid function were followed for a median of 23 mo. Results: Pharmacokinetics and dosimetric results were related to the initial activity concentration (IC) of the infused solution. The decay-corrected activity concentration decreased with time in the peritoneal fluid to 50% IC at 24 h, increased in serum to 6% IC at 45 h, and increased in the thyroid to 127% ± 63% IC at 20 h without blocking and less than 20% IC with blocking. No other organ uptakes could be detected. The cumulative urinary excretion was 40 kBq/(MBq/L) at 24 h. The estimated absorbed dose to the peritoneum was 15.6 ± 1.0 mGy/(MBq/L), to red bone marrow it was 0.14 ± 0.04 mGy/(MBq/L), to the urinary bladder wall it was 0.77 ± 0.19 mGy/(MBq/L), to the unblocked thyroid it was 24.7 ± 11.1 mGy/(MBq/L), and to the blocked thyroid it was 1.4 ± 1.6 mGy/(MBq/L) (mean ± SD). No adverse effects were observed either subjectively or in laboratory parameters. Conclusion: This study indicates that by intraperitoneal administration of 211At-MX35 F(ab′)2 it is possible to achieve therapeutic absorbed doses in microscopic tumor clusters without significant toxicity.

Antibody Targeting in Metastatic Colon Cancer: A Phase I Study of Monoclonal Antibody F19 Against a Cell-Surface Protein of Reactive Tumor Stromal Fibroblasts

PURPOSE To define the toxicity, imaging, and biodistribution characteristics of iodine 131-labeled monoclonal antibody F19 (131I-mAbF19). MAbF19 recognizes the fibroblast activation protein (FAP), a cell-surface glycoprotein not present in most normal tissues, but abundantly expressed by reactive stromal fibroblasts of epithelial cancers, including more than 95% of primary and metastatic colorectal carcinomas. PATIENTS AND METHODS 131I-mAbF19 was administered intravenously to 17 patients with hepatic metastases from colorectal carcinoma who were scheduled for resection of localized metastases or insertion of hepatic artery catheter for regional chemotherapy. Seven to 8 days before surgery, patients received 131I-mAbF19 at three dose levels, with at least four patients entered at each level. RESULTS No toxicity associated with intravenous 131I-mAbF19 administration was observed. Tumor images were obtained on planar and single-photon emission tomography (SPECT) scans in 15 of 17 patients with hepatic metastases, tumor-infiltrated portal lymph nodes, and/or recurrent pelvic disease. The smallest lesion visualized was 1 cm in diameter. The optimal time for tumor imaging was 3 to 5 days after 131I-mAbF19 administration. The use of image registration techniques allowed precise anatomic localization of 131I-mAbF19 accumulation. Immunohistochemical analysis of biopsy tissues showed expression of FAP in the tumor stroma (but not in normal liver) in all patients studied and confirmed that the FAP-positive tumor stromal fibroblasts were interposed between the tumor capillaries and the malignant colon epithelial cells. At the time of surgery, tumor-to-liver ratios up to 21:1 and tumor-to-serum ratios up to 9:1 were obtained. The fraction of the injected 131I-mAbF19 dose per gram tumor (%ID/g tumor) localized to hepatic metastases at the time of surgery ranged from 0.001% to 0.016%. CONCLUSION The FAP tumor fibroblast antigen is highly expressed in primary and metastatic colorectal carcinomas and shows limited expression in normal adult tissues. This highly selective expression pattern allows imaging of colorectal carcinoma lesions as small as 1 cm in diameter on 131I-mAbF19 scans. Because of the consistent presence of FAP in the stroma of epithelial cancers and the accessibility of FAP-positive tumor stromal fibroblasts to circulating monoclonal antibodies (mAbs), this study suggests possible diagnostic and therapeutic applications of humanized mAbF19 and mAbF19 constructs with novel immune and nonimmune effector functions.

Sequential Cytarabine and α-Particle Immunotherapy with Bismuth-213-Lintuzumab (HuM195) for Acute Myeloid Leukemia

Purpose: Lintuzumab (HuM195), a humanized anti-CD33 antibody, targets myeloid leukemia cells and has modest single-agent activity against acute myeloid leukemia (AML). To increase the potency of the antibody without the nonspecific cytotoxicity associated with β-emitters, the α-particle–emitting radionuclide bismuth-213 (213Bi) was conjugated to lintuzumab. This phase I/II trial was conducted to determine the maximum tolerated dose (MTD) and antileukemic effects of 213Bi-lintuzumab, the first targeted α-emitter, after partially cytoreductive chemotherapy. Experimental Design: Thirty-one patients with newly diagnosed (n = 13) or relapsed/refractory (n = 18) AML (median age, 67 years; range, 37-80) were treated with cytarabine (200 mg/m2/d) for 5 days followed by 213Bi-lintuzumab (18.5-46.25 MBq/kg). Results: The MTD of 213Bi-lintuzumab was 37 MB/kg; myelosuppression lasting >35 days was dose limiting. Extramedullary toxicities were primarily limited to grade ≤2 events, including infusion-related reactions. Transient grade 3/4 liver function abnormalities were seen in five patients (16%). Treatment-related deaths occurred in 2 of 21 (10%) patients who received the MTD. Significant reductions in marrow blasts were seen at all dose levels. The median response duration was 6 months (range, 2-12). Biodistribution and pharmacokinetic studies suggested that saturation of available CD33 sites by 213Bi-lintuzumab was achieved after partial cytoreduction with cytarabine. Conclusions: Sequential administration of cytarabine and 213Bi-lintuzumab is tolerable and can produce remissions in patients with AML. Clin Cancer Res; 16(21); 5303–11. ©2010 AACR.

Pilot Trial of Unlabeled and Indium-111–Labeled Anti–Prostate-Specific Membrane Antigen Antibody J591 for Castrate Metastatic Prostate Cancer

Background: Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein primarily expressed on benign and malignant prostatic epithelial cells. J591 is an IgG1 monoclonal antibody that targets the external domain of the PSMA. The relationship among dose, safety, pharmacokinetics, and antibody-dependent cellular cytotoxicity (ADCC) activation for unlabeled J591 has not been explored. Patients and Methods: Patients with progressive metastatic prostate cancer despite androgen deprivation were eligible. Each patient received 10, 25, 50, and 100 mg of J591. Two milligrams of antibody, conjugated with the chelate 1,4,7,10-tetraazacyclododecane-N, N′,N″,N‴-tetraacetic acid, were labeled with 5 mCi indium-111 (111In) as a tracer. One group of patients received unlabeled J591 before the labeled antibody; the other received both together. Toxicities, pharmacokinetic properties, biodistribution, ADCC induction, immunogenicity, and clinical antitumor effects were assessed. Results: Fourteen patients were treated (seven in each group). Treatment was well tolerated. Biodistribution of 111In-labeled J591 was comparable in both groups. The mean T1/2 was .96, 1.9, 2.75, and 3.47 days for the 10, 25, 50, and 100 mg doses, respectively. Selective targeting of 111In-labeled J591 to tumor was seen. Hepatic saturation occurred by the 25-mg dose. ADCC activity was proportional to dose. One patient showed a >50% prostate-specific antigen decline. Conclusions: J591 is well tolerated in repetitive dose-escalating administrations. The rate of serum clearance decreases with increasing antibody mass. ADCC activation is proportional to antibody mass. The optimal dose is 25 mg for radioimmunotherapy and 100 mg for immunotherapy. Phase II studies using J591 as a radioconjugate are under way.

Human Mu Opioid Receptor (OPRM1 A118G) polymorphism is associated with brain mu-opioid receptor binding potential in smokers

Evidence points to the endogenous opioid system, and the mu-opioid receptor (MOR) in particular, in mediating the rewarding effects of drugs of abuse, including nicotine. A single nucleotide polymorphism (SNP) in the human MOR gene (OPRM1 A118G) has been shown to alter receptor protein level in preclinical models and smoking behavior in humans. To clarify the underlying mechanisms for these associations, we conducted an in vivo investigation of the effects of OPRM1 A118G genotype on MOR binding potential (BPND or receptor availability). Twenty-two smokers prescreened for genotype (12 A/A, 10 */G) completed two [11C]carfentanil positron emission tomography (PET) imaging sessions following overnight abstinence and exposure to a nicotine-containing cigarette and a denicotinized cigarette. Independent of session, smokers homozygous for the wild-type OPRM1 A allele exhibited significantly higher levels of MOR BPND than smokers carrying the G allele in bilateral amygdala, left thalamus, and left anterior cingulate cortex. Among G allele carriers, the extent of subjective reward difference (denicotinized versus nicotine cigarette) was associated significantly with MOR BPND difference in right amygdala, caudate, anterior cingulate cortex, and thalamus. Future translational investigations can elucidate the role of MORs in nicotine addiction, which may lead to development of novel therapeutics.

A phase I toxicity, pharmacology, and dosimetry trial of monoclonal antibody OKB7 in patients with non-Hodgkin's lymphoma: effects of tumor burden and antigen expression.

Eighteen patients with relapsed non-Hodgkins lymphoma (NHL) were infused with escalating doses of monoclonal antibody (mAb) OKB7, trace-labeled with iodine-131 (131I), in order to study toxicity, pharmacology, antibody localization, and dosimetry of radioiodine. OKB7 is a noncytotoxic mouse immunoglobulin G2b (IgG2b) mAb reactive with B cells and most B-cell NHL. Three patients each were treated at six dose levels ranging from 0.1 mg to 40 mg. All patients had radionuclide imaging and counting daily, had serial blood sampling to study pharmacokinetics, human antimouse antibody (HAMA), and circulating antigen, and had a biopsy of accessible lymphoma to determine delivery of isotope to tumors and assess the effect of tumor antigen expression on mAb delivery. Bone marrow biopsies were also done in the majority of patients. There was no toxicity. Serum clearance showed a median early phase half-life of 1.9 hours and a later phase half-life of 21.7 hours. Median total body clearance half-life was 22 hours. Pharmacokinetics were not dose-related. HAMA was detected in five patients. Circulating blocking antigen was detected in the serum of four patients, but at levels that were of pharmacologic consequence only in one. Biopsied tumor tissue from five patients did not express OKB7 antigen. No significant uptake of antibody was seen in these tumor sites. Mean total uptake of isotope into lymphoma measured in biopsies correlated linearly over the 400-fold increase in injected mAb dose. However, the percent of injected dose found per gram of tumor was unrelated to dose, but correlated inversely with tumor burden. In two patients with minimal tumor burden, 1.0 mg and 5.0 mg doses of OKB7 resulted in tumor to body radioisotope dose ratios of 22 and 7, which would theoretically permit tolerable delivery of 4,400 and 1,400 rads to these tumors, respectively, if OKB7 were conjugated with higher doses of 131I.