Fractionated radioimmunotherapy of intraperitoneally growing ovarian cancer in nude mice with 211At-MX35 F(ab′)2: therapeutic efficacy and myelotoxicity
Introduction
Ovarian cancer frequently recurs through micrometastatic growth on the peritoneal surface, and patients succumb due to advanced peritoneal carcinomatosis including ascites, in spite of debulking surgery and systemic chemotherapy. External abdominal radiotherapy proved to be unsuccessful due to limitations on the absorbed dose to normal tissue. Therefore, adjuvant locoregional treatment with intraperitoneal injections of specific antibodies could be decisive in the treatment of remaining micrometastatic disease. In this study, we used the monoclonal antibody (mAb) MX35 F(ab′)2, which recognizes a cell surface glycoprotein of ∼95 kDa on ovarian tumor cells. The cytotoxicity was mediated by labeling the mAbs with an α-particle-emitting radionuclide, 211At. We used an animal model relevant in clinical oncology, which allows intraperitoneal radioimmunotherapy (RIT). The intraperitoneal approach increases the absorbed dose to the tumor and reduces myelotoxicity as the clearance rate from the peritoneal cavity to the systemic circulation is delayed compared with intravenous injection. Fractionated RIT (FRIT) could possibly alleviate the myelotoxicity and increase tumor nodule sterilization by a gradual peeling away of the outermost cells of larger tumors. Alleviation of myelotoxicity could also provide the possibility of an increase in the therapeutic efficacy, by allowing a larger total amount of activity to be administered.
Some studies have been performed on RIT of ovarian cancer, mostly mAbs labeled with 90Y and 131I, in both animals and humans [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. Studies of FRIT of cancer in general have also been performed [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], to some extent indicating a possibility of increasing the therapeutic index. However, due to the fact that the β-particles emitted have too long a range for the treatment of microscopic tumors, we believe that it is important to investigate the therapeutic efficacy of mAbs labeled with α-particle emitters when treating microscopic disease on the peritoneum. In this study, we used the α-particle emitter 211At, with a half-life of 7.21 h, a mean range in tissue of ∼62 μm and a mean linear energy transfer (LET) of ∼111 keV/μm. The short half-life of this radionuclide makes it ideal for local treatment as the target cells are easily reached and as the transfer of the radioimmunocomplex to the systemic circulation is slow. The short range ensures a significant absorbed dose to very small tumors or even single cells [31]. The high LET, together with a high relative biological effectiveness (RBE), of the α-particles indicates that only a small number of 211At atoms have to be targeted to sterilize the cell. We have previously investigated the therapeutic efficacy of the intact specific IgG1 mAbs MOv18 and MX35 as well as fragmented mAbs [MX35 F(ab′)2 and nonspecific rituximab F(ab′)2] in the treatment of nude mice with ovarian cancer [32], [33], [34], [35], [36], [37]. Those studies showed good therapeutic efficacy with a tumor-free fraction (TFF; i.e., percentage of animals with no macro- and microscopic tumor growth and no ascites) of ∼60% when injecting ∼400 kBq 211At-MX35 3 weeks after cell inoculation, as well as an increasing importance of using a specific mAb compared with a nonspecific mAb when treating larger tumors. An activity of 400 kBq was chosen in the earlier studies based on indications that it should be within the toxic limit [38], [39]. Later studies have shown that the toxic limit is higher, that is, ∼1300 kBq [40]. However, an increase in the injected activity above ∼400 kBq does not improve the therapeutic outcome, probably because an increase in the absorbed dose to the tumors is prevented by restricted diffusion and saturation effects [35].
The aim of the present study was to investigate the therapeutic efficacy and myelotoxicity during FRIT of ovarian cancer in nude mice. The study was performed using the mAb MX35 F(ab′)2 labeled with the α-particle emitter 211At.
Section snippets
Radionuclide
211At was produced by the 209Bi(α,2n)211At reaction in a cyclotron (Scanditronix MC32 at the Positron Emission Tomography and Cyclotron Unit, Rigshospitalet, Copenhagen, Denmark) by irradiating a 209Bi target with 28-MeV α-particles. The 211At was isolated using a dry-distillation procedure [41].
Monoclonal antibodies
MX35 is a murine IgG1-class mAb, developed and characterized at the Memorial Sloan-Kettering Cancer Center (MSKCC), New York, USA. MX35 is directed toward a cell surface glycoprotein of ∼95 kDa on
Labeling and immunoreactivity of antibodies
The radiochemical yields were 30–40%, and the radiochemical purity was more than 95% as determined by methanol precipitation and gel-permeability chromatography. The immunoreactivity measurements of the 211At-MX35 F(ab′)2 and OVCAR-3 cells gave an immunoreactive fraction, r, of 0.98.
Therapeutic efficacy and myelotoxicity
The TFFs were 56% and 41% (P>.5) when treatment was given with a total of ∼800 kBq MX35 F(ab′)2 as a single dose (Group 1) and via fractionated administration (Group 2: 3× ∼267 kBq), respectively (Table 1). The TFFs
Discussion
Some reasons why FRIT appears promising are the possibility of (a) reducing the systemic toxicity and, hence, increasing the maximum tolerated activity (MTA); (b) achieving a more uniform absorbed dose distribution in the tumor; and (c) increasing the therapeutic index [13].
Regarding systemic toxicity in the clinical case, large, single administrations during RIT sometimes necessitate progenitor cell rescuing bone marrow transplantation (BMT). FRIT could decrease or even eliminate the need for
Conclusion
No advantage was observed in the therapeutic efficacy of a fractionated regimen compared with a single administration, with the same total amount of administered 211At-MX35 F(ab′)2. However, alleviation of myelotoxicity was observed following the fractionated regimen and delayed nadir of the WBC counts. No thrombocytopenia was observed during either the fractionated or the single-administration regimens. The results indicate the possibility of increasing the MTA when a fractionated regimen is
Acknowledgments
This work was supported by grants from the Swedish Cancer Society (No. 3548) and the King Gustaf V Jubilee Clinic Research Foundation in Göteborg, Sweden. We would like to thank Dr. Chaitanya R. Divgi, Director of Targeted Radiotherapy at the MSKCC, for making the mAb MX35 F(ab′)2 available.
References (48)
- et al.
Radioimmunotherapy in advanced ovarian cancer: is there a role for pre-targeting with (90)Y-biotin?
Gynecol Oncol
(2004) - et al.
Intraperitoneal radioimmunotherapy of ovarian cancer with 177Lu-CC49: a phase I/II study
Gyncol Oncol
(1997) - et al.
Administered activity and metastatic cure probability during radioimmunotherapy of ovarian cancer in nude mice with 211At-MX35 F(ab′)2
Int J Radiat Oncol
(2006) - et al.
Radiotoxicity of systemically administered 211At-labeled human/mouse chimeric monoclonal antibody: a long-term survival study with histological analysis
Int J Radiat Oncol Biol Phys
(1999) - et al.
Alpha-particle radiotherapy with 211At-labeled monodisperse polymer particles, 211At-labeled IgG proteins, and free 211At in a murine intraperitoneal tumor model
Gynecol Oncol
(1995) - et al.
Dry-distillation of astatine-211 from irradiated bismuth targets: a time-saving procedure with high recovery yields
Appl Radiat Isot
(2001) - et al.
Initial immunochemical characterization of MX35 ovarian cancer antigen
Gynecol Oncol
(1997) - et al.
Biodistribution and intraoperative evaluation of radiolabeled monoclonal antibody MX35 in patients with epithelial ovarian cancer
Gynecol Oncol
(1993) - et al.
High-efficiency astatination of antibodies using N-iodosuccinimide as the oxidizing agent in labeling of N-succinimidyl 3-(trimethylstannyl)benzoate
Nucl Med Biol
(2001) - et al.
Determination of the immunoreactive fraction of radiolabeled monoclonal antibodies by linear extrapolation to binding at infinite antigen excess
J Immunol Methods
(1984)
Preliminary results of nanopharmaceuticals used in the radioimmunotherapy of ovarian cancer
J Pharm Pharm Sci
Intraperitoneal radioimmunotherapy in an ovarian carcinoma mouse model: effect of the radionuclide
Int J Gynecol Cancer
Intraperitoneal radioimmunotherapy with human monoclonal IGM in nude mice with peritoneal carcinomatosis
Cancer Biother Radiopharm
Intraperitoneal radioimmunochemotherapy of ovarian cancer: a phase I study
Cancer Biother Radiopharm
A phase II study of intraperitoneal radioimmunotherapy with iodine-131-labeled monoclonal antibody OC-125 in patients with residual ovarian carcinoma
Clin Cancer Res
Long term survival of patients with advanced ovarian cancer treated with intraperitoneal radioimmunotherapy
Int J Gynecol Cancer
A phase I study of combined modality 90yttrium-CC49 intraperitoneal radioimmunotherapy for ovarian cancer
Clin Cancer Res
Intraperitoneal yttrium-90-labeled monoclonal antibody in ovarian cancer
J Clin Oncol
A pivotal phase III trial to evaluate the efficacy and safety of adjuvant treatment with R1549 (yttrium-90-labeled HMFG1 murine monoclonal antibody) in epithelial ovarian cancer (EOC)
Proc Am Soc Clin Oncol
Single-dose versus fractionated radioimmunotherapy of human colon carcinoma xenografts using 131I-labeled multivalent CC49 single-chain fvs
Clin Cancer Res
Rationales, evidence, and design considerations for fractionated radioimmunotherapy
Cancer
Fractionated radioimmunotherapy using low doses of iodine-131 labeled anti-CEA monoclonal antibody after tumor volume reduction
Chin Med J (Engl)
Maximum tolerated dose and large tumor radioimmunotherapy studies of 64Cu-labeled monoclonal antibody 1A3 in a colon cancer model
Clin Cancer Res
Myelosuppressive changes from single or repeated doses of radioantibody therapy: effect of bone marrow transplantation, cytokines, and hematopoietic suppression
Exp Hematol
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Recent progress of astatine-211 in endoradiotherapy: Great advances from fundamental properties to targeted radiopharmaceuticals
2022, Chinese Chemical LettersCitation Excerpt :The minimum required activity of 211At-labelled MX35 F(ab')2 for the treatment of ovarian cancer models was suggested to be 100 kBq, since TFF was higher than 50% when further increasing the dosage. A series of researches suggested that a variety of factors, including initial tumor volume [217–219], injection method [220,221] and specific activity of radiopharmaceuticals [222,223] had important impacts on the therapeutic effect of 211At-labelled MX35 F(ab')2 ovarian cancer models. Briefly, high specific activity of 211At-labelled MX35 F(ab')2 tends to exhibit better therapeutic effect on small-size tumors, and biotoxicity could be obviously diminished when fractionated-injection is adopted.
Radioimmunotherapy of cancer with high linear energy transfer (LET) radiation delivered by radionuclides emitting α-particles or Auger electrons
2017, Advanced Drug Delivery ReviewsCitation Excerpt :However, short-lived Auger electron-emitting radionuclides may be used with intact IgG forms for targeting micrometastatic disease in the BM since localization occurs rapidly following i.v. injection. All studies of Auger electron RIT to date have employed intact IgG, but F(ab′)2 fragments have been used for RIT with β-emitters or α-emitters [43,106–108]. Smaller engineered antibody fragments (e.g. recombinant Fab or single chain Fv) that are eliminated very rapidly from the blood have been studied mainly in pre-targeting approaches to RIT in which a bispecific antibody fragment is administered first to target the tumor followed by the radionuclide bound to a small molecule that recognizes the antibody in a second step [109,110].
Absorbed Doses and Risk Estimates of <sup>211</sup>At-MX35 F(ab')<inf>2</inf> in Intraperitoneal Therapy of Ovarian Cancer Patients
2015, International Journal of Radiation Oncology Biology PhysicsCitation Excerpt :Targeting vectors labeled with α-particle–emitting radionuclides have attractive properties for the treatment of minimal residual disease, including short range, high energy, and high linear energy transfer (1). Preclinical studies have shown the therapeutic efficacy of TAT against peritoneal ovarian cancer (2-4). Specifically, treatment with the monoclonal antibody fragment MX35 F(ab')2, labeled with the α-particle emitter astatine-211 (211At, t½ = 7.2 h) was shown to be sterilizing for tumors less than approximately 0.5 mm in diameter, without bringing about absorbed doses that were critical to normal tissues (5).
Comparison of therapeutic efficacy and biodistribution of <sup>213</sup>Bi- and <sup>211</sup>At-labeled monoclonal antibody MX35 in an ovarian cancer model
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Therapeutic Efficacy of Astatine-211-Labeled Trastuzumab on Radioresistant SKOV-3 Tumors in Nude Mice
2007, International Journal of Radiation Oncology Biology PhysicsCitation Excerpt :Assuming rapid (a few hours) targeting of cancer cells after intraperitoneal injection of 211At-labeled antibodies, such treatment should result in a high therapeutic efficacy. We have previously described the effects of [211At]α-RIT on an ovarian cancer model (3–7). In those studies, we achieved a high tumor-free fraction of mice inoculated with the cell line NIH:OVCAR-3.
Astatine-211 based radionuclide therapy: Current clinical trial landscape
2023, Frontiers in Medicine