Biomedical subjects

Ruby F Meredith

Publications and source records attributed to Ruby F Meredith.

24 records · Page 2Linked to original sources

PubMed2003

A novel monoclonal antibody design for radioimmunotherapy.

The generation of chimeric and complementary-determining region (CDR) grafted monoclonal antibodies (MAb) have reduced the immunogenicity problem in the clinical application of radioimmunotherapy with monoclonal antibodies. However, humanization (Hu) has prolonged the circulation (plasma T1/2) of radiolabeled antibodies, resulting in an increased normal tissue exposure to radioactivity and greater dose-limiting bone marrow suppression. To overcome this problem, a tumor-associated glycoprotein (TAG)-72-specific CDR grafted MAb with C(H)2 domain deletion (DeltaC(H)2) was developed from the MAb CC49. Preclinical studies have demonstrated that HuCC49 DeltaC(H)2 clears more rapidly from the plasma of mice than HuCC49. This preliminary report describes the initial human experience with HuCC49 DeltaC(H)2 radiolabeled with 131I and administered to patients with metastatic colorectal carcinoma. In this pilot study we enrolled four patients who received a single infusion of 20 mg of HuCC49 DeltaC(H)2 (total protein dose) labeled with 10 mCi of 131I. Pharmacokinetics, biodistribution, dosimetry, and immune response were evaluated over 2-6 weeks. No toxicity was observed in this group of patients. A one-compartment bolus model using the non-linear (NLIN) procedures in Statistical Analysis Software (SAS; SAS, Incorporated, Cary, NC) best describes the pharmacokinetics of the 131I-HuCC49 DeltaC(H)2 with a plasma mean T1/2 of 20 +/- 3 hours, a mean residence time (MRT) of 29 +/- 4 hours and a clearance rate (Cl) of 1.5 +/- 0.1 mL/hours/kg. The whole body and marrow radiation dose estimates were 0.55 +/- 0.06 rad/mCi and 1.00 +/- 0.14 rad/mCi, respectively. All patients had positive localization of antibody to metastatic tumor sites. The 131I-HuCC49 DeltaC(H)2 biodistribution was similar to murine CC49. Three patients had no evidence of antibody response to HuCC49 DeltaC(H)2 over 6 weeks of observation, and one patient had a marginal response by week 6. Intravenous administration of HuCC49 DeltaC(H)2 is safe and well tolerated. The deleted C(H)2 construct has a shorter half-life compared with prior studies of murine CC49 but with similar biodistribution and low immunogenicity. These studies support the further clinical investigation of this agent in phase I trials by intravenous and intraperitoneal routes.

Adult↗

PubMed2002

Model prediction of treatment planning for dose-fractionated radioimmunotherapy.

BACKGROUND: Clinical trials of radioimmunotherapy (RIT) often use dose fractionation to reduce marrow toxicity. The dosing scheme can be optimized if marrow and tumor cell kinetics following radiation exposure are known. METHODS: A mathematic model of tumor clonogenic cell kinetics was combined with a previously reported marrow cell kinetics model that included marrow stromal cells, progenitor cells, megakaryocytes, and platelets. Reported values for murine tumor and marrow cellular turnover rates and radiosensitivity were used in the model calculation. RESULTS: Given a tolerated level of thrombocytopenia, there is a fractionation scheme in which total radioactive dose administration can be maximized. Isoeffect doses that had different numbers of fractions and total radioactivity, but induced identical platelet nadirs of 20%, were determined. Assuming identical tumor uptake for all dose fractions, six tumor types were examined: early-responding tumors, late-responding tumors, and tumors that lacked a late-responding effect, with either constant or accelerated doubling time. For most tumor types, better tumor control (tumor growth delay and nadir of survival fraction) was predicted for a dosing scheme in which total radioactive dose was maximized. For late-responding tumors with accelerated doubling time, tumor growth delay increased, but the nadir of survival fraction became shallower as the number of fractions increased. CONCLUSIONS: A mathematic model has been developed that allows prediction of the nadir and duration of thrombocytopenia as well as tumor clonogenic cell response to various RIT doses and fractionation schemes. Given a maximum tolerated level of thrombocytopenia, the model can be used to determine a dosing scheme for optimal tumor response.

Abnormalities, Radiation-Induced↗

PubMed2002

Rationales, evidence, and design considerations for fractionated radioimmunotherapy.

Although fractionation can be used in a discrete radiobiologic sense, herein it is generally used in the broader context of administration of multiple, rather than single, doses of radionuclide for radioimmunotherapy (RIT) or other targeted radionuclide therapies. Fractionation is a strategy for overcoming heterogeneity of monoclonal antibody (MAb) distribution in the tumor and the consequent nonuniformity of tumor radiation doses. Additional advantages of fractionated RIT are the ability to 1) provide patient-specific radionuclide and radiation dosing, 2) control toxicity by titration of the individual patient, 3) reduce toxicity, 4) increase the maximum tolerated dose (MTD) for many patients, 5) increase tumor radiation dose and efficacy, and 6) prolong tumor response by permitting treatment over time. However, fractionated RIT has logistic and economic implications. Preclinical and clinical data substantiate the advantages of fractionated RIT, although the radiobiology for conventional external beam radiotherapy does not provide a straightforward rationale for RIT unless fractionation leads to more uniform distribution of radiation dose throughout the tumor. Preclinical data have shown that toxicity and mortality can be reduced while efficacy is increased, thereby providing inferential evidence of greater uniformity of radiation dose. Direct evidence of superior dosimetry and tumor activity distribution has also been found. Clinical data have shown that toxicity can be better controlled and reduced and the MTD extended for many patients. It is clear that fractionated RIT can only fulfill its potential if the effects of critical issues, such as the number and amount of radionuclide doses, the radionuclide physical and effective half-life, and the dose interval, are better characterized.

Animals↗

PubMed2002

Concurrent chemoradiation therapy with cisplatin and paclitaxel for locally advanced non-small cell lung cancer: long-term follow-up of a phase I trial.

The purpose of this trial was to evaluate the feasibility of concurrent paclitaxel/cisplatin and conventional thoracic irradiation in locally advanced non-small cell lung cancer (NSCLC). Ambulatory patients with medically inoperable or unresectable stage II-III NSCLC, and performance status 0-2 were eligible. Patients were not excluded from this trial if they had lost more than 5% of their body weight during the preceding 3 months, and/or if they had small ipsilateral pleural effusion. The initial dose of paclitaxel/cisplatin was 110 and 50 mg/m(2), and was escalated through five dose levels. Four cycles of chemotherapy were planned; the first two cycles were given concurrently with radiotherapy (4 weeks apart), followed by two additional cycles (every 3 weeks). Conventional chest radiotherapy to a total dose of 60 Gy (2 Gy per day) was delivered in 6 weeks. Forty-three patients were enrolled of which 38 were evaluable for response. Dose-limiting toxicities were grade 4 neutropenia (43% of patients) and grade 3 esophagitis (26% of patients) during the chemoradiotherapy phase. Grade > or = 2 acute and late pulmonary toxicity occurred in 10 and 68% of the patients, respectively. In most patients, prompt symptomatic and radiologic improvement was observed with early steroid administration. The volume of lung receiving 15-30 Gy was correlated with late pulmonary toxicity. The overall response was 84% with ten complete and 22 partial responses. The median survival was 16.5 months (95% confidence interval, 9.5 to 25) for those patients evaluable for response. After a median follow-up of 70 months, 5 (13%) patients are alive without evidence of disease. The maximum tolerated dose (MTD) of paclitaxel and cisplatin with concurrent radiotherapy is at dose level 3 paclitaxel (135 mg/m(2)) and cisplatin (75 mg/m(2)). Toxicity, although significant, was manageable in the great majority of the patients. The activity observed with this regimen is particularly noteworthy when considering the advanced nature of these patients, and the fact that patients (N=18) with poor risk factors were included in the study.

Adolescent↗

PubMed2002

Improved prediction of myelotoxicity using a patient-specific imaging dose estimate for non-marrow-targeting (90)Y-antibody therapy.

UNLABELLED: For calculation of radiation dose to the marrow, standard dosimetry for radiopharmaceuticals that do not bind to the marrow includes dose contributions from radioactivity in blood and the remainder of the body. For a pure beta -emitter such as (90)Y, marrow dose is usually determined by the blood contribution. However, myelotoxicity from (90)Y-antibody therapy often correlates poorly with marrow dose estimated using the blood method. This study proposes a method to address 2 possible factors affecting marrow dose estimates. These include (a) recycled (90)Y in bone/marrow space after (90)Y-antibody has been processed in the liver and (b) use of the marrow mass of Reference Man for individual patients. METHODS: Thirty-three patients with advanced non-small cell lung cancer were treated with (90)Y-anti-TAG-72 murine antibody (CC49). TAG-72 is often expressed in epithelial-derived tumors but not in normal marrow. (111)In-CC49 was used as a tracer. The marrow doses from blood were calculated on the basis of radioactivity concentrations in blood. Marrow dose in the lumbar vertebrae was estimated from images for (111)In-CC49 uptake in L2-L4. In 20 patients who had CT images, trabecular bone volumes of L2-L4 were measured from CT images to estimate patient-specific marrow mass in L2-L4. The fraction of baseline platelet counts at nadir was used as an indicator of myelotoxicity. RESULTS: Marrow dose per unit injected radioactivity estimated from blood was lower than that from L2-L4 uptake values. Prediction of myelotoxicity using marrow dose estimated from blood was poorer than that using injected dose per body surface area (GBq/m(2)) (r = 0.31 vs. 0.51). Prediction was improved using marrow dose estimated from L2-L4 uptake, assuming the marrow mass of Reference Man (r = 0.67 for n = 33; r = 0.70 for n = 20). Prediction was worse if reference marrow mass was adjusted by body weight (r = 0.56 for n = 33; r = 0.63 for n = 20). Prediction was not improved if adjusted by body surface area or lean body mass but was improved if adjusted by height (r = 0.72 for n = 33; r = 0.78 for n = 20). The best prediction was obtained (r = 0.85 for n = 20) using patient-specific L2-L4 marrow mass estimated from CT. CONCLUSION: Marrow dose estimated from the blood radioactivity method was not a good predictor of myelotoxicity for non-marrow-targeting (90)Y-antibody therapy. Thrombocytopenia in this group of patients correlated much better with dose estimated from lumbar vertebrae imaging and patient-specific marrow mass than with that estimated from GBq/m(2) or standard marrow dose based on blood.

Adult↗

PubMed2002

A Phase I study of combined modality (90)Yttrium-CC49 intraperitoneal radioimmunotherapy for ovarian cancer.

PURPOSE: The purpose of this study was to determine the feasibility and maximum tolerated dose of (90)Yttrium-CC49 ((90)Y-CC49) as the radioimmunotherapy (RIT) component of an i.p. combined modality treatment for recurrent ovarian cancer. EXPERIMENTAL DESIGN: A Phase I trial of (90)Y-CC49 RIT was conducted in ovarian cancer patients who had persistent or recurrent intra-abdominal disease, had failed one or two prior chemotherapy regimens, and demonstrated TAG-72 expression. Patients were treated with a previously established combined modality treatment protocol of s.c. IFN alpha2b, i.p. paclitaxel, and increasing dosages of i.p. (90)Y-CC49. Patients were monitored for toxicity, generation of human antimouse antibody response, and clinical efficacy. RESULTS: Twenty eligible patients were treated per study specifications. All patients had been treated with debulking and paclitaxel/carboplatin-based chemotherapy at initial diagnosis. The patients included 11 patients with persistent disease at the time of second look laparotomy and 9 patients with delayed recurrence. Patients were treated with i.p. (90)Y-CC49 given in combination with s.c. IFN alpha2b (dose of 3 x 10(6) units for a total of four doses) and i.p. paclitaxel (dose of 100 mg/m(2)). RIT treatment was associated with primarily hematological toxicity. The maximum tolerated dose of i.p. (90)Y-CC49 was established at 24.2 mCi/m(2) in this combined regimen. Of nine patients with measurable disease, two had partial responses lasting 2 and 4 months. Of 11 patients with nonmeasurable disease, median time to progression was 6 months in 7 patients who recurred; 4 of these patients remain no evidence of disease at 9+, 18+, 19+, and 23+ months. CONCLUSIONS: (90)Yttrium-CC49-based RIT in combination with IFN alpha2b and i.p. paclitaxel is feasible and well tolerated at a dose of < or =24.2 mCi/m(2).

Adenocarcinoma↗