Systemic targeted radionuclide therapy: potential new areas

Autophagy inhibition improves the targeted radionuclide therapy efficacy of 131I-FAP-2286 in pancreatic cancer xenografts

PURPOSES

Radiotherapy can induce tumor cell autophagy, which might impair the antitumoral effect. This study aims to investigate the effect of autophagy inhibition on the targeted radionuclide therapy (TRT) efficacy of 131I-FAP-2286 in pancreatic cancer.

METHODS

Human pancreatic cancer PANC-1 cells were exposed to 131I-FAP-2286 radiotherapy alone or with the autophagy inhibitor 3-MA. The autophagy level and proliferative activity of PANC-1 cells were analyzed. The pancreatic cancer xenograft-bearing nude mice were established by the co-injection of PANC-1 cells and pancreatic cancer-associated fibroblasts (CAFs), and then were randomly divided into four groups and treated with saline (control group), 3-MA, 131I-FAP-2286 and 131I-FAP-2286 + 3-MA, respectively. SPECT/CT imaging was performed to evaluate the bio-distribution of 131I-FAP-2286 in pancreatic cancer-bearing mice. The therapeutic effect of tumor was evaluated by 18F-FDG PET/CT imaging, tumor volume measurements, and the hematoxylin and eosin (H&E) staining, and immunohistochemical staining assay of tumor tissues.

RESULTS

131I-FAP-2286 inhibited proliferation and increased the autophagy level of PANC-1 cells in a dose-dependent manner. 3-MA promoted 131I-FAP-2286-induced apoptosis of PANC-1 cells via suppressing autophagy. SPECT/CT imaging of pancreatic cancer xenograft-bearing nude mice showed that 131I-FAP-2286 can target the tumor effectively. According to 18F-FDG PET/CT imaging, the tumor growth curves and immunohistochemical analysis, 131I-FAP-2286 TRT was capable of suppressing the growth of pancreatic tumor accompanying with autophagy induction, but the addition of 3-MA enabled 131I-FAP-2286 to achieve a better therapeutic effect along with the autophagy inhibition. In addition, 3-MA alone did not inhibit tumor growth.

CONCLUSIONS

131I-FAP-2286 exposure induces the protective autophagy of pancreatic cancer cells, and the application of autophagy inhibitor is capable of enhancing the TRT therapeutic effect.

Recent Advances in Radiometals for Combined Imaging and Therapy in Cancer

Nuclear medicine is defined as the use of radionuclides for diagnostic and therapeutic applications. The imaging modalities positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are based on γ-emissions of specific energies. The therapeutic technologies are based on β^- -particle-, α-particle-, and Auger electron emitters. In oncology, PET and SPECT are used to detect cancer lesions, to determine dosimetry, and to monitor therapy effectiveness. In contrast, radiotherapy is designed to irreparably damage tumor cells in order to eradicate or control the disease's progression. Radiometals are being explored for the development of diagnostic and therapeutic radiopharmaceuticals. Strategies that combine both modalities (diagnostic and therapeutic), referred to as theranostics, are promising candidates for clinical applications. This review provides an overview of the basic concepts behind therapeutic and diagnostic radiopharmaceuticals and their significance in contemporary oncology. Select radiometals that significantly impact current and upcoming cancer treatment strategies are grouped as clinically suitable theranostics pairs. The most important physical and chemical properties are discussed. Standard production methods and current radionuclide availability are provided to indicate whether a cost-efficient use in a clinical routine is feasible. Recent preclinical and clinical developments and outline perspectives for the radiometals are highlighted in each section.

Clinical radioimmunotherapy--the role of radiobiology

Conventional external-beam radiation therapy is dedicated to the treatment of localized disease, whereas radioimmunotherapy represents an innovative tool for the treatment of local or diffuse tumors. Radioimmunotherapy involves the administration of radiolabeled monoclonal antibodies that are directed specifically against tumor-associated antigens or against the tumor microenvironment. Although many tumor-associated antigens have been identified as possible targets for radioimmunotherapy of patients with hematological or solid tumors, clinical success has so far been achieved mostly with radiolabeled antibodies against CD20 ((131)I-tositumomab and (90)Y-ibritumomab tiuxetan) for the treatment of lymphoma. In this Review, we provide an update on the current challenges aimed to improve the efficacy of radioimmunotherapy and discuss the main radiobiological issues associated with clinical radioimmunotherapy.

A pretherapy biodistribution and dosimetry study of indium-111-radiolabeled trastuzumab in patients with human epidermal growth factor receptor 2-overexpressing breast cancer

PURPOSE

The purposes of this study were to evaluate the organ biodistribution, pharmacokinetics, immunogenicity, and tumor uptake of (111)Indium ((111)In)-MxDTPA-trastuzumab in patients with human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancers and to determine whether (90)Y-MxDTPA-trastuzumab should be evaluated in subsequent clinical therapy trials.

EXPERIMENTAL DESIGN

Patients with HER2-overexpressing breast cancers who were to undergo planned trastuzumab therapy first received unlabeled trastuzumab (4-8 mg/kg IV), followed 4 hours later by 5 mCi (111)In-MxDTPA-trastuzumab (10 mg antibody). Serial blood samples, 24-hour urine collections, and nuclear scans were performed at defined time points for 7 days.

RESULTS

Eight (8) patients received (111)In-MxDTPA-trastuzumab, which was well tolerated with no adverse side-effects. Three (3) of 7 patients with known lesions demonstrated positive imaging on nuclear scans. No antiantibody responses were observed for 2 months postinfusion. Organ doses (cGy/mCi) assuming radiolabeling with (90)Y were 19.9 for heart wall, 17.6 for liver, 4.6 for red marrow, and 2.8 for the whole body. Tumor doses ranged from 24 to 172 cGy/mCi.

CONCLUSIONS

In summary, results from this study indicate that (90)Y-MxDTPA-trastuzumab is an appropriate agent to evaluate in therapy trials. No evidence of an immune response to (111)In-MxDTPA-trastuzumab was detected, predicting for the ability to administer multiple cycles. With the exception of cardiac uptake, pharmacokinetics and organ biodistribution were comparable to other (90)Y-labeled monoclonal antibodies previously evaluated in the clinic. Cardiac uptake was comparable to hepatic uptake and therefore predicted to not be prohibitively high as to result in dose-limiting cardiotoxicity.

Nanotargeted radionuclides for cancer nuclear imaging and internal radiotherapy

Current progress in nanomedicine has exploited the possibility of designing tumor-targeted nanocarriers being able to deliver radionuclide payloads in a site or molecular selective manner to improve the efficacy and safety of cancer imaging and therapy. Radionuclides of auger electron-, α-, β-, and γ-radiation emitters have been surface-bioconjugated or after-loaded in nanoparticles to improve the efficacy and reduce the toxicity of cancer imaging and therapy in preclinical and clinical studies. This article provides a brief overview of current status of applications, advantages, problems, up-to-date research and development, and future prospects of nanotargeted radionuclides in cancer nuclear imaging and radiotherapy. Passive and active nanotargeting delivery of radionuclides with illustrating examples for tumor imaging and therapy are reviewed and summarized. Research on combing different modes of selective delivery of radionuclides through nanocarriers targeted delivery for tumor imaging and therapy offers the new possibility of large increases in cancer diagnostic efficacy and therapeutic index. However, further efforts and challenges in preclinical and clinical efficacy and toxicity studies are required to translate those advanced technologies to the clinical applications for cancer patients.

Production study of high specific activity NCA Re-186g by proton and deuteron cyclotron irradiation

Very high specific activity (A(S)) (186g)Re could be produced by either proton or deuteron cyclotron irradiation on highly enriched (186)W target in no-carrier-added (NCA) form, leading to a A(S) very close to the theoretical carrier free (CF) value of 6.88GBqmicrog(-1). Thick target yields (TTYs), obtained irradiating both thick metal W targets of natural isotopic composition and highly enriched pressed powdered (186)W targets, were measured at different particles energies taking into account high accuracy and precision on both yield and beam energy. The measurement of radionuclidic purity of (186g)Re obtained activating highly enriched (186)W by both p and d beams were also carried out and accurately compared. The excitation function as thin-target yields (tty, i.e. proportional to the reaction cross-sections) and the integrated TTYs for all Re (A=181, 182, 183, 184, 186 and their metastable levels), W and Ta co-produced radionuclides will be presented elsewhere in deep details.

The protein kinase C agonist PEP005 (ingenol 3-angelate) in the treatment of human cancer: a balance between efficacy and toxicity

The diterpene ester ingenol-3-angelate (referred to as PEP005) is derived from the plant Euphorbia peplus. Crude euphorbia extract causes local toxicity and transient inflammation when applied topically and has been used in the treatment of warts, skin keratoses and skin cancer. PEP005 is a broad range activator of the classical (α, β, γ) and novel (δ, ε, η, θ) protein kinase C isoenzymes. Direct pro-apoptotic effects of this drug have been demonstrated in several malignant cells, including melanoma cell lines and primary human acute myelogenous leukemia cells. At micromolar concentrations required to kill melanoma cells this agent causes PKC-independent secondary necrosis. In contrast, the killing of leukemic cells occurs in the nanomolar range, requires activation of protein kinase C δ (PKCδ) and is specifically associated with translocation of PKCδ from the cytoplasm to the nuclear membrane. However, in addition to this pro-apoptotic effect the agent seems to have immunostimulatory effects, including: (i) increased chemokine release by malignant cells; (ii) a general increase in proliferation and cytokine release by activated T cells, including T cells derived from patients with chemotherapy-induced lymphopenia; (iii) local infiltration of neutrophils after topical application with increased antibody-dependent cytotoxicity; and (iv) development of specific anti-cancer immune responses by CD8(+) T cells in animal models. Published studies mainly describe effects from in vitro investigations or after topical application of the agent, and careful evaluation of the toxicity after systemic administration is required before the possible use of this agent in the treatment of malignancies other than skin cancers.

A phase I study of a combination of yttrium-90-labeled anti-carcinoembryonic antigen (CEA) antibody and gemcitabine in patients with CEA-producing advanced malignancies

PURPOSE

To determine the maximum tolerated dose of combined therapy using an yttrium-90-labeled anti-carcinoembryonic antigen (CEA) antibody with gemcitabine in patients with advanced CEA-producing solid tumors.

EXPERIMENTAL DESIGN

The chimeric human/murine cT84.66 is an anti-CEA intact IgG1, with high affinity and specificity to CEA. This was given at a fixed yttrium-90-labeled dose of 16.6 mCi/m(2) to subjects who had and an elevated CEA in serum or in tumor by immunohistochemistry. Also required was a tumor that imaged with an (111)In-labeled cT84.66 antibody. Patients were treated with escalating doses of gemcitabine given i.v. over 30 minutes on day 1 and 3 after the infusion of the yttrium-90-labeled antibody. Patients were treated in cohorts of 3. The maximum tolerated dose was determined as the highest level at which no >1 of 6 patients experienced a dose limiting toxicity.

RESULTS

A total of 36 patients were enrolled, and all but one had prior systemic therapy. The maximum tolerated dose of gemcitabine in this combination was 150 mg/m(2). Dose limiting toxicities at a gemcitabine dose of 165 mg/m(2) included a grade 3 rash and grade 4 neutropenia. One partial response was seen in a patient with colorectal cancer, and 4 patients had a >50% decrease in baseline CEA levels associated with stable disease. Human antichimeric antibody responses were the primary reason for stopping treatment in 12 patients.

CONCLUSIONS

Feasibility of combining gemcitabine with an yttrium-90-labeled anti-CEA antibody is shown with preliminary evidence of clinical response.

Pharmacokinetics, micro-SPECT/CT imaging and therapeutic efficacy of (188)Re-DXR-liposome in C26 colon carcinoma ascites mice model

The pharmacokinetics and internal radionuclide therapy of intraperitoneally administrated (188)Re-N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA)-labeled pegylated liposomal doxorubicin ((188)Re-DXR-liposome) were investigated in the C26 murine colon carcinoma ascites mouse model. After intraperitoneal administration of the nanotargeted bimodality (188)Re-DXR-liposome, the ascites and tumor accumulation of the radioactivity were observed, the levels of radioactivity within the ascites were maintained at relatively higher levels before 48 h and the levels of radioactivity in the tumor were maintained at steady levels after 4 h. The AUC((o-->infinity)) of (188)Re-DXR-liposome in blood, ascites and tumor was 9.3-, 4.2- and 4.7-fold larger than that of (188)Re-BMEDA, respectively. The maximum tolerated dose of intraperitoneally administrated (188)Re-DXR-liposome was determined in normal BALB/c mice. The survival, tumor and ascites inhibition of mice after (188)Re-DXR-liposome (22.2 MBq of (188)Re, 5 mg/kg of DXR) treatment were evaluated. Consequently, radiochemotherapeutics of (188)Re-DXR-liposome attained better survival time, tumor and ascites inhibition (decreased by 49% and 91% at 4 days after treatment; P<.05) in mice than radiotherapeutics of (188)Re-liposome or chemotherapeutics of Lipo-Dox did. Therefore, intraperitoneal administration of novel (188)Re-DXR-liposome could provide a benefit and promising strategy for delivery of passive nanotargeted bimodality radiochemotherapeutics in oncology applications.

Therapeutic efficacy of 177Lu-CHX-A''-DTPA-hu3S193 radioimmunotherapy in prostate cancer is enhanced by EGFR inhibition or docetaxel chemotherapy

BACKGROUND

This study investigated the biodistribution and therapeutic efficacy of Lutetium-177 (177Lu) radiolabeled anti-Lewis Y monoclonal antibody hu3S193 radioimmunotherapy (RIT) in mice bearing prostate cancer xenografts. The ability of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478 and docetaxel chemotherapy to enhance the efficacy of RIT was also assessed in vivo.

METHODS

The in vitro cytotoxicity of 177Lu labeled hu3S193 on Le(y) positive DU145 prostate cancer cells was assessed using proliferation assays, with induction of apoptosis measured by ELISA. The in vivo biodistribution and tumor localization of 177Lu-hu3S193 was assessed in mice bearing established DU145 tumor xenografts. The efficacy and maximum tolerated dose of 177Lu-hu3S193 RIT in vivo was determined by a dose escalation study. EGFR inhibitor AG1478 or docetaxel chemotherapy was administered at sub-therapeutic doses in conjunction with RIT in vivo.

RESULTS

177Lu-hu3S193 mediated significant induction of cytotoxicity and apoptosis in vitro. In vivo analysis of 177Lu-hu3S193 biodistribution demonstrated specific targeting of DU145 prostate cancer xenografts, with maximal tumor uptake of 33.2 +/- 3.9%ID/g observed at 120 hr post-injection. In RIT studies, 177Lu-hu3S193 caused specific and dose-dependent inhibition of prostate cancer tumor growth. A maximum tolerated dose of 350 microCi was determined for 177Lu-hu3S193. Combination of 177Lu-hu3S193 RIT with EGFR inhibitor AG1478 or docetaxel chemotherapy both significantly improved efficacy.

CONCLUSIONS

177Lu-hu3S193 RIT is effective as a single agent in the treatment of Le(y) positive prostate cancer models. The enhancement of RIT by AG1478 or docetaxel indicates the promise of combined modality strategies.

Image-guided total-marrow irradiation using helical tomotherapy in patients with multiple myeloma and acute leukemia undergoing hematopoietic cell transplantation

PURPOSE

Total-body irradiation (TBI) has an important role in patients undergoing hematopoietic cell transplantation (HCT), but is associated with significant toxicities. Targeted TBI using helical tomotherapy results in reduced doses to normal organs, which predicts for reduced toxicities compared with standard TBI.

METHODS AND MATERIALS

Thirteen patients with multiple myeloma were treated in an autologous tandem transplantation Phase I trial with high-dose melphalan, followed 6 weeks later by total-marrow irradiation (TMI) to skeletal bone. Dose levels were 10, 12, 14, and 16 Gy at 2 Gy daily/twice daily. In a separate allogeneic HCT trial, 8 patients (5 with acute myelogenous leukemia, 1 with acute lymphoblastic leukemia, 1 with non-Hodgkin's lymphoma, and 1 with multiple myeloma) were treated with TMI plus total lymphoid irradiation plus splenic radiotherapy to 12 Gy (1.5 Gy twice daily) combined with fludarabine/melphalan.

RESULTS

For the 13 patients in the tandem autologous HCT trial, median age was 54 years (range, 42-66 years). Median organ doses were 15-65% that of the gross target volume dose. Primarily Grades 1-2 acute toxicities were observed. Six patients reported no vomiting; 9 patients, no mucositis; 6 patients, no fatigue; and 8 patients, no diarrhea. For the 8 patients in the allogeneic HCT trial, median age was 52 years (range, 24-61 years). Grades 2-3 nausea, vomiting, mucositis, and diarrhea were observed. In both trials, no Grade 4 nonhematologic toxicity was observed, and all patients underwent successful engraftment.

CONCLUSIONS

This study shows that TMI using helical tomotherapy is clinically feasible. The reduced acute toxicities observed compare favorably with those seen with standard TBI. Initial results are encouraging and warrant further evaluation as a method to dose escalate with acceptable toxicity or to offer TBI-containing regimens to patients unable to tolerate standard approaches.

Radionuclide carriers for targeting of cancer

This review describes strategies for the delivery of therapeutic radionuclides to tumor sites. Therapeutic approaches are summarized in terms of tumor location in the body, and tumor morphology. These determine the radionuclides of choice for suggested targeting ligands, and the type of delivery carriers. This review is not exhaustive in examples of radionuclide carriers for targeted cancer therapy. Our purpose is two-fold: to give an integrated picture of the general strategies and molecular constructs currently explored for the delivery of therapeutic radionuclides, and to identify challenges that need to be addressed. Internal radiotherapies for targeting of cancer are at a very exciting and creative stage. It is expected that the current emphasis on multidisciplinary approaches for exploring such therapeutic directions should enable internal radiotherapy to reach its full potential.

Novel radiolabeled antibody conjugates

This article reviews the development of radioimmunoconjugates as a new class of cancer therapeutics. Numerous conjugates involving different antigen targets, antibody forms, radionuclides and methods of radiochemistry have been studied in the half-century since radioactive antibodies were first used in model systems to selectively target radiation to tumors. Whereas directly conjugated antibodies, fragments and subfragments have shown promise preclinically, the same approaches have not gained success in patients except in radiosensitive hematological neoplasms, or in settings involving minimal or locoregional disease. The separation of tumor targeting from the delivery of the therapeutic radionuclide in a multistep process called pretargeting has the potential to overcome many of the limitations of conventional, or one-step, radioimmunotherapy, with initial preclinical and clinical data showing increased sensitivity, specificity and higher radiation doses delivered. Our particular focus in pretargeting is the use of bispecific, trimeric (three Fab's) constructs made by a new antibody engineering method termed 'dock-and-lock.