Reinfusion of Unprocessed, Granulocyte Colony-stimulating Factor- stimulated Whole Blood Allows Dose Escalation of Relabeled Chimeric Monoclonal Antibody U36 Radioimmunotherapy in a Phase I Dose Escalation Study

Purpose: In an earlier Phase I radioimmunotherapy (RIT) study with rhenium-186-labeled chimeric monoclonal antibody (cMAb) U36 in patients with refractory head and neck squamous cell carcinoma, the maximum tolerated activity was established at 1.0 GBq/m, at which bone marrow doses ranged from 0.7 to 1.1 Gy. In the present study, further dose escalation in RIT was evaluated using a facile method of reinfusion of granulocyte colony-stimulating factor (G-CSF)-stimulated unprocessed whole blood. Experimental Design: Nine patients with recurrent or metastatic head and neck squamous cell carcinoma were treated at radiation dose levels of 1.0, 1.5, and 2.0 GBq/m. Before RIT, G-CSF (10 g/kg/day) was administered s.c. at home during 5 days. On day 6, just before administration of Relabeled cMAb U36, 1 liter of whole blood was harvested and kept unprocessed at 4°C until reinfusion after 72 h. Blood samples were taken for analysis of pharmacokinetics and bone marrow dosimetry. Patients were evaluated for myelotoxicity and tumor response. Results: Blood harvesting, RIT, and reinfusion of whole blood were well tolerated by all patients. G-CSF stimulation resulted in a mean of 0.41 10 CD34 cells/kg (range, 0.15–0.83 10 CD34 cells/kg) and a mean committed colony-forming units granulocyte macrophage count of 5.62 10/kg (range, 0.62–13.37 10/kg). The mean biological half-life of Relabeled cMAb U36 in blood was 72.6 16.0 h, and bone marrow doses ranged from 2.1 to 2.8 Gy at the highest dose level. Myelotoxicity exceeding grade 3 was not observed. Stable disease was observed in five of nine patients, ranging from 3 to 5 months, and was still ongoing in one of these patients. Conclusions: This study indicates that a doubling of the maximum tolerated activity and bone marrow dose of Relabeled cMAb U36 can be achieved using reinfusion of GCSF-stimulated unprocessed whole blood. INTRODUCTION Radiolabeled MAbs can be used for selective delivery of radiation to tumor sites. For selective treatment of HNSCC, RIT might be an interesting approach as an adjuvant therapy because there is still a high failure rate, either locally or at distant sites, after locoregional treatment of HNSCC with surgery and/or radiotherapy. In patients with hematological malignancies, RIT has shown efficacy, resulting in improved remission and response rates (1, 2). In most of the RIT trials conducted thus far, radiogenic damage to the bone marrow has been the dose-limiting toxicity, resulting in thrombocytopenia and granulocytopenia occurring with a nadir of 4 – 6 weeks after RIT. Autologous transplantation of bone marrow or separated growth factor-mobilized blood stem cells can reduce myelotoxicity and allowed dose escalation of RIT (3–5). Stem cell transplantation in patients with relapsed B-cell lymphomas treated with high-dose RIT allowed bone marrow-absorbed doses as high as 6.4 Gy before cardiopulmonary dose-limiting toxicity was observed (6). Both transplantation of bone marrow and filtered blood stem cells require equipment and laboratory facilities for separation and cryopreservation, whereas both techniques are laborious and expensive. In comparison, G-CSF-stimulated unprocessed whole blood might be an alternative source of blood stem cells. Reinfusion of G-CSF-stimulated whole blood is a straightforward and safe procedure, and it can be performed in a routine clinical setting at low cost (7, 8). The G-CSF-stimulated whole blood can be stored for at least 72 h at 4°C without significant loss of viability of the blood stem cells (9, 10). Whereas up to 90% of the CD34 population shows early apoptotic changes after cryopreservation (11), only 5–10% apoptotic changes were Received 12/4/01; revised 8/5/02; accepted 8/6/02. 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 by Dutch Cancer Society Grant VU 96-1313 and Centocor Inc. (Malvern, PA). 2 To whom requests for reprints should be addressed, at Department of Otolaryngology/Head and Neck Surgery, Vrije Universiteit Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands. Phone: 31-20-4443690; Fax: 31-20-4443688; E-mail: gams.vandongen@ vumc.nl. 3 The abbreviations used are: MAb, monoclonal antibody; G-CSF, granulocyte colony-stimulating factor; RIT, radioimmunotherapy; cMAb, chimeric MAb; HNSCC, head and neck squamous cell carcinoma; MTA, maximum tolerated activity; CFU-GM, colony-forming unit(s) granulocyte macrophage. 3401 Vol. 8, 3401–3406, November 2002 Clinical Cancer Research Research. on April 2, 2017. © 2002 American Association for Cancer clincancerres.aacrjournals.org Downloaded from found in the CD34 population in whole blood transplants after 72 h of storage (12). In multicyclic chemotherapy regimens of short duration, this procedure allowed dose intensification in patients with small cell lung cancer (7, 13). Moreover, myeloablative chemotherapy with whole blood rescue for patients with high-risk lymphoma and multiple myeloma was proven to be feasible (8, 14, 15). To our knowledge, this whole blood procedure has never been applied in RIT studies. Because the time interval between RIT and the development of myelotoxicity is 4–6 weeks, reinfusion of G-CSFstimulated whole blood is a realistic option to reduce myelotoxicity of RIT because it allows the reinfused blood stem cells to home and proliferate in the bone marrow before myelotoxicity becomes manifest. A prerequisite for this approach is that most of the radioactivity has disappeared from blood and bone marrow at the time of reinfusion. In an earlier Phase I study, rhenium-186-labeled cMAb U36 was evaluated in patients with refractory HNSCC (16). The MTA (at which a grade 4 hematological or grade 3 nonhematological toxicity developed in not more than one of six patients) was found to be 1.0 GBq/m, with a maximum tolerated bone marrow dose of 0.9 0.2 Gy. Dose-limiting grade 4 myelotoxicity occurred in two of three patients treated with 1.5 GBq/m. The effective half-life of Relabeled cMAb U36 in blood was 37 h, meaning that after 72 h, 25% of the injected radioactivity was still present in the blood. This effective half-life is related to both the biological half-life of the MAb and the physical half-life of the radionuclide, according to the equation 1/T1/2 effective 1/T1/2 biological 1/T1/2 physical. In the current study, we evaluated whether reinfusion of G-CSF-stimulated unprocessed whole blood after 72 h allows dose escalation of Relabeled cMAb U36 RIT. MATERIALS AND METHODS Nine patients (five men and four women; age range, 48–71 years) were included in this study. Their characteristics are listed in Table 1. All patients had clinical evidence of relapsed HNSCC, either locoregionally or at distant sites, for which no curative options were available. A histologically confirmed HNSCC in the past was required for inclusion. Other eligibility criteria were described in an earlier report on a Phase I doseescalation study without blood stem cell support (16). The study was approved by the Institutional Review Board of the Vrije Universiteit Medical Center (Amsterdam, the Netherlands). All patients gave written informed consent after thorough explana-