Phase 1/1! Radioimmunotherapy Trial with Iodine-131-labeled Monoclonal Antibody G250 in Metastatic Renal Cell Carcinoma1

This Phase 1111 radioimmunotherapy study was carried out to determine the maximum tolerated dose (MTD) and therapeutic potential of ‘31I-G250. Thirty-three patients with measurable metastatic renal cell carcinoma were treated. Groups of at least three patients received escalating amounts of ‘ ‘I (30, 45, 60, 75, and 90 mCi/m2) labeled to 10 mg of mouse monoclonal antibody G250, administered as a single i.v. infusion. Fifteen patients were studied at the MTD of activity. No patient had received prior significant radiotherapy; one had received prior G250. Whole-body scintigrams and single-photon emission computed tomography images were obtained in all patients. There was targeting of radioactivity to all known tumor sites that were 2 cm. Reversible liver function test abnormalities were observed in the majority of patients (27 of 33 patients). There was no correlation between the amount of 1311 administered or hepatic absorbed radiation dose (median, 0.073 Gy/mCi) Received 5/7/98; revised 8/20/98; accepted 8/24/98. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported in part by National Cancer Institute Grant CA-33049. 2 To whom requests for reprints should be addressed, at Nuclear Mcdicine Service, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021. Phone: (212) 639-2459; Fax: (212) 7173263; E-mail: [email protected]. 3 Present address: Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Austin and Repatriation Medical Centre, Heidelberg, Victoria, 3084, Australia. 4 Present address: Department of Urology, Academic Hospital, 6500 HB, Nijmegen, the Netherlands. and the extent or nature of hepatic toxicity. Two of the first six patients at 90 mCi/m2 had grade 3 thrombocytopenia; the MTD was determined to be 90 mCi/m2 ‘ ‘I. Hematological toxicity was correlated with whole-body absorbed radiation dose. All patients developed human antimouse antibodies within 4 weeks posttherapy; retreatment was, therefore, not possible. Seventeen of 33 evaluable patients had stable disease. There were no major responses. On the basis of external imaging, ‘31I-labeled mouse monoclonal antibody G250 showed excellent localization to all tumors that were 2 cm. Seventeen of 33 patients had stable disease, with tumor shrinkage observed in two patients. Antibody immunogenicity restricted therapy to a single infusion. Studies with a nommmunogemc G250 antibody are warranted. INTRODUCTION RCC5 is the most common renal malignancy in adults, accounting for 3% of all malignancies and 80-90% of all primary kidney neoplasms (1). The prognosis for these patients is poor; -30-40% of all patients present with metastatic disease at the time of diagnosis (2). In the United States, an estimated 28,000 new cases are diagnosed each year, and -11,500 deaths occur per year (3). Despite attempts to develop treatment strategies for RCC, the prognosis for these patients remains unsatisfactory. Fiveyear survival is < 10% (4, 5), and for those with distant metastases or stage IV RCC, the median survival is <2 years. The tumor is resistant to radiation therapy (6) and chemotherapy (7). Biological response modifiers have, thus far, shown only mmimal efficacy in patients with RCC (8-15). The development of technologies to generate mAbs (16) created the possibility of new treatment modalities for cancer. A range of novel cell surface antigens expressed by human cancer have been defined by mAbs, and a number of antibody-based therapies targeting such antigens are being developed (17). The different therapeutic strategies under exploration include: (a) antibody-mediated tumor cell killing via complement activation or antibody-dependent cellular cytotoxicity (18); (b) antibodymediated interference of cell growth by neutralizing growth factors or blocking growth factor receptors (19); and (c) antibody delivery systems targeting radioactive isotopes (20), toxins (2 1), or chemotherapeutic agents (22) to the tumor site. The 5 The abbreviations used are: RCC, renal cell carcinoma; mAb, monoclonal antibody; mG250, mouse mAb G250; IRB, Institutional Review Board; MTD, maximum tolerated dose; MTDA, MTh of activity; CT, computed tomography; NRS, normal rabbit serum; cG250, chimeric G250. Research. on October 2, 2017. © 1998 American Association for Cancer clincancerres.aacrjournals.org Downloaded from 2730 Radioimmunotherapy with ‘31I-G250 mAb in RCC many technical challenges confronting successful application of antibody therapies, e.g. , immunogenicity of mouse antibodies, antigen expression by normal tissues, low levels of antibody uptake by tumors, and heterogeneity in antigen expression by tumor cells, have become clear from initial clinical trials, and progress is being made in overcoming these limiting features. Efforts to identify and select antigens expressed in renal carcinomas led to the development of mG250. G250 detects an antigen that is expressed in virtually all clear cell carcinomas of the kidney but does not react with normal kidney tissue. G250 reactivity in normal tissues was found to be restricted to the gastric epithelium, the large biliary ducts in the liver, and some pancreatic acini (22-24). The G250 antigen has recently been characterized by cxpression cloning, and the complete G250 sequence and organization of the coding gene have been characterized (25). The G250 antigen is closely related or identical to the MN antigen, an antigen originally detected by a mouse antibody against HeLa cells and extensively analyzed as a marker for cervical dysplasia and carcinoma (26). The G25OIMN sequence has a domain that is homologous to carbonic anhydrase and a putative helix-loop-helix DNA-binding sequence (26). A presurgical clinical study was conducted using 1311 labeled to escalating mass amounts of rnG250 to determine tumor uptake and biodistribution (24). Tumor biopsy samples showed a high level of rnG250 localization, with levels up to 0. 1% of the injected dose per gram of tumor 7 days postinfusion. As cxpected from the expression of G250 in bile ducts, there was liver uptake of ‘ ‘I-mG250, which decreased with higher doses, suggesting saturation of G250 sites by antibody. On the basis of these cx vivo observations, the optimal protein dose was estimated to be 10 mg of rnG250 per infusion. Here, we present the results of a Phase I/Il radioimmunotherapy study in patients with measurable metastatic RCC, designed to determine the maximum dose of iv. administered 1311 labeled to mG250, radioisotope retention in tumors, quality of imaging, and assessment of organ toxicity. PATIENTS, MATERIALS, AND METHODS Study Design Prior to antibody iv. infusion, a physical examination was performed and the medical history of each patient reviewed, including histopathological confirmation of RCC. Starting before administration of the radiolabeled antibody, patients received 10 drops of a saturated potassium iodide solution three times daily for 2 weeks to block 131j uptake in the thyroid. Five levels (30, 45, 60, 75, and 90 mCi/rn2) of ‘ ‘I labeled to 10 mg of mG250 were investigated. Radiolabeled antibodies were administered iv. over 60 mm using a Pancretec 5000 pump (Pancretec, San Diego, CA). A minimum of three patients formed the cohort for treatment at each dose level. Patients occupied single rooms under strict radiation isolation procedures and were monitored by the Radiation Protection Service of Memorial Hospital until discharge from the hospital when their measured radiation exposure rates decreased to <5 mR/h at 1 rn. Additional measurements were taken 1 week later. Patients were not retreated. Escalating activities of ‘ ‘ ‘I-mG250 were prepared with a constant mass amount of mG250, until the MTDA had been established. An additional nine patients were studied at the MTDA to monitor any possible therapeutic effects. Vital signs were measured before and at the end of the infusion. Hematological and serum hepatic function parameters were measured at least weekly for 6 weeks or until recovery from toxicity. For determination of serum ‘ ‘ ‘I content, blood samples were drawn just before antibody administration, at the end of the infusion, daily until hospital discharge, and 1 and 2 weeks postinjection. Serum samples were analyzed for radioactivity in a gamma counter (LKB Wallac, Piscataway, NJ). Patient Eligibility The Phase I/lI radioimmunotherapy study was conducted under an Investigational New Drug Application (BB-IND-3 154) with a protocol and consent form approved by the IRB at Memorial Sloan-Kettering Cancer Center (92-71), according to the principles of the Declaration of Helsinki. Before participation, the patients provided written informed consent. Patients who had prior radiotherapy to the entire pelvis or lumbosacral spine were excluded from the study, as were patients with clinically significant heart disease (New York Heart Association Class III/IV), evidence of central nervous system tumor involvement, any infection requiring antibiotics, or illness requiring steroids. Pregnant or lactating women were not eligible for the study. Histological slides from all patients were reviewed in the Department of Pathology, Memorial Hospital Sloan-Kettering Cancer Center, for confirmation of RCC. Male and female patients were eligible for the study if they had measurable metastatic clear cell renal carcinoma, had a survival expectancy of 6 weeks, and were ambulatory with an adequate performance status (Karnofsky score, 70%). Clinical laboratory measurements required: a WBC count of 3500/mm3; a platelet count of 100,000/mm3; a prothrombin time 1.3 times that of control; a serum creatinine level of 2 mg/dl; a serum bilirubin level of 2 mg/dl; and a serum calcium level of 12.5 mg/dl. mAb: Preparation and Radiolabeling The generation, characteristics, and reactivity of mG2SO have been described (23, 24). For each individual patient, 10 mg of mG250 were labeled with an appropriate amount of (New England Nuclear, Boston, MA) to prepare the requisite therapeutic administration (in mCi/rn2) using the chloramine T method (27). ‘31I-mG250 was chromatographed over Sephadex G25 (Pharmacia LKB, Piscataway, NJ) and fractions with peak radioactivity were pooled and passed through a 0.22-p.m sterile filter. These freshly prepared clinical samples of ‘311-mG250 had a median immunoreactivity of 68% (range, 53-89%) with >95% of ‘ ‘I precipitable in 10% trichloroacetic acid. Radioimmunoscintigraphy and Pharmacokinetics Tumor typing was not performed for G250 antigen because the majority of RCCs express the antigen (23, 24). Indirect evidence for G250 antigen expression was obtained by correlation of ‘ 31I-mG250 targeting, assessed by imaging, with known tumor sites. Patients remained in the hospital between 1 and 4 days. The Research. on October 2, 2017. © 1998 American Association for Cancer clincancerres.aacrjournals.org Downloaded from Clinical Cancer Research 2731 number of days in hospital varied depending on the activity administered. Anterior and posterior whole-body I images (General Electric, Milwaukee, WI; ADAC Laboratories, Milpitas, CA) were obtained prior to discharge from the hospital and 1 and 2 weeks after infusion. Single-photon emission CT images of relevant areas were obtained at 1 and, if possible, at 2 weeks postinfusion. Determination of Human Antimouse IgG Antibodies Terasaki plates (VWR Scientific, West Chester, PA) were coated with mG250 (250 xg/ml in 1% NRS-0.05 M carbonate buffer, pH 9.5) and allowed to adhere overnight at 37#{176}C. Negative control wells were similarly coated with 1% NRS-carbonate without mG250, and positive control wells were coated with 1 % normal human serum in 1 % NRS/carbonate buffer. To block nonspecific binding, 10% NRS in PBS was added to the wells. Serial dilutions of patient sera, starting at dilutions of 1: 10, were then added to the wells and incubated for 1 h at room temperature. Afterward, plates were washed and incubated with rabbit antihuman immunoglobulin-alkaline phosphatase (1:100; DAKO, Carpenteria, CA) in 1% NRS-PBS. Substrate (p-nitrophenyl phosphate; Sigma Chemical Co., St. Louis, MO) at 1 mg/ml was added to the wells, and plates were incubated at 37#{176}C for 30 mm. Absorbance was read at 405 nm. Pretreatment patient sera were used as an internal negative control. A positive result was defined as posttreatment serum that gave an absorbance reading at 405 nm above the reading obtained for the pretreatment sample at the same dilution. Radiation Dosimetry Whole Body. Serum clearance was derived from blood samples and expressed as the decay-corrected percentage of the administered activity per liter. The derivation of whole-body clearance kinetics has been described elsewhere (28). Briefly, clearance curves were obtamed by combining survey meter measurements, taken during patient isolation, with planar imaging data collected subsequently. A monoexponential clearance function was fitted to whole body activity and an effective half-time calculated. Cumulated whole-body activity was derived from the area under the clearance curve. Mean absorbed radiation doses to the whole body were calculated using standard MIRD (29) methods by multiplying the cumulated activity in the whole body by a mass-adjusted S factor for 131j, Liver. The modified conjugate view method (30) was used on planar whole-body images to quantitate ‘ ‘I-rnG250 uptake in the liver. Briefly, gamma camera sensitivity was derived from ‘ ‘ ‘I standards of known activity that were imaged simultaneously with the patients. Regions of interest were drawn around the liver at each time point, and the total activity was determined. Liver volumes were obtained from baseline CT scans. Monoexponential clearance functions were fitted to activity (mCi/g) in the liver, and cumulated activities were derived. Absorbed doses to liver were calculated using values of 4.1 gGy/mCih for the mean 3 energy emitted per unit cumulated activity (absorbed fraction = 1.0) and 6.3 gGy/mCih for the mean photon energy emitted per unit cumulated activity. Absorbed fractions for photons were derived by interpolation, on the basis of liver mass, from the data presented in MIRD pamphlet 3 (31) for monoenergetic 364-keV photons. Safety and Toxicity Weekly blood samples, obtained from all patients, were analyzed for complete blood counts and laboratory values until all values returned to baseline. Thyroid function tests (serum tri-iodothyronine, total thyroxine, and thyroid-stimulating hormone) were also obtained at baseline and at 6-week intervals until the end of the study. The National Cancer Institute Cornmon Toxicity Criteria were used to grade the severity of toxicity and abnormal laboratory values. All grade 4 toxicities were reported in writing within 24 h to the IRB. The MTDA was defined as the activity per m2 at which not more than one-third of the total number of patients had grade 3 or 4 toxicity. The response proportions for combination chemotherapy in this patient population ranges from 10 to 20%. Hence, it was decided that, for the Phase II portion of the study, efficacy of < 15% would not be worthy of further consideration. We, therefore, decided to accrue 15 patients at the MTDA and to study 15 more patients only if two or more major responses were seen in the initial cohort of 15 patients. Estimation of the response rate within ± 17% with 95% confidence was expected. CT scans of the chest, abdomen, and pelvis were obtained for evaluation of disease at baseline and for determination of possible response. Scans were obtained 2 weeks prior to radioimmunotherapy and between 6 and 8 weeks after therapy. All preand postradioimmunotherapy CT scans were evaluated by a radiologist. Responses were graded as follows. Cornplete response was defined as disappearance of all clinical evidence of active disease (tumor and symptoms) for a minimum of 1 month. Partial response was defined as a decrease of 50% in the sum of the products of the diameters of all measurable lesions for a minimum of 1 month. Also, there could be no simultaneous increase in size of any lesion or any new lesions. Stable disease was defined as a <50% decrease or no objective change in any disease parameter throughout treatment. Also, there could be no new lesions or worsening of symptoms, and this state had to persist for a minimum of 3 months. Progression was defined as an unequivocal increase in size (>25%) of any lesion(s) or the appearance of any new lesion. RESULTS Thirty-three patients (24 men and 9 women) with a mean age of 59 years (range, 29-79 years) were entered. Patient characteristics are shown in Table 1 . All patients had RCC, confirmed by histopathology, with measurable metastatic disease. Hematopoietic Toxicity Hematopoietic toxicity (Tables 2 and 3) was not seen in the three patients at the lowest dose (30 mCi/rn2). Three (patients 6, 8, and 9) of six patients at 45 mCi/rn2 and one (patient 1 1) of three at 60 mCi/rn2 had grade 1 thrombocytopenia, which occurred 28-35 days after infusion. At 75 mCi/m2, one (patient 15) of six patients had grade 4 thrombocytopenia 35 days after infusion, and two (patients 16 and 18) had grade 2 thrombocyResearch. on October 2, 2017. © 1998 American Association for Cancer clincancerres.aacrjournals.org Downloaded from ‘ ‘I Table I Patient characteristics and distribution within dosage groups” Age -(yr) Sexarea Body surface (m2) Primary cancer Prior therapy5 Extent of metastatic disease Patient no.