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1.  A new class of bispecific antibodies to redirect T cells for cancer immunotherapy 
mAbs  2013;6(2):381-391.
Various constructs of bispecific antibodies (bsAbs) to redirect effector T cells for the targeted killing of tumor cells have shown considerable promise in both preclinical and clinical studies. The single-chain variable fragment (scFv)-based formats, including bispecific T-cell engager (BiTE) and dual-affinity re-targeting (DART), which provide monovalent binding to both CD3 on T cells and to the target antigen on tumor cells, can exhibit rapid blood clearance and neurological toxicity due to their small size (~55 kDa). Herein, we describe the generation, by the modular DOCK-AND-LOCKTM (DNLTM) method, of novel T-cell redirecting bispecific antibodies, each comprising a monovalent anti-CD3 scFv covalently conjugated to a stabilized dimer of different anti-tumor Fabs. The potential advantages of this design include bivalent binding to tumor cells, a larger size (~130 kDa) to preclude renal clearance and penetration of the blood-brain barrier, and potent T-cell mediated cytotoxicity. These prototypes were purified to near homogeneity, and representative constructs were shown to provoke the formation of immunological synapses between T cells and their target tumor cells in vitro, resulting in T-cell activation and proliferation, as well as potent T-cell mediated anti-tumor activity. In addition, in vivo studies in NOD/SCID mice bearing Raji Burkitt lymphoma or Capan-1 pancreatic carcinoma indicated statistically significant inhibition of tumor growth compared with untreated controls.
PMCID: PMC3984327  PMID: 24492297
bispecific antibody; T-cell redirected therapy; DOCK-AND-LOCK; Burkitt lymphoma; pancreatic cancer
2.  Identification of PAM4 (clivatuzumab)-reactive epitope on MUC5AC: A promising biomarker and therapeutic target for pancreatic cancer 
Oncotarget  2015;6(6):4274-4285.
PAM4 is a monoclonal antibody showing high specificity for pancreatic ductal adenocarcinoma (PDAC). Humanized PAM4 labeled with 90Y in combination with low-dose gemcitabine has shown promising therapeutic activity, and is being evaluated in a phase III clinical trial. Prior efforts have suggested that PAM4 potentially reacts with MUC5AC, a secretory mucin expressed de novo in early pancreatic neoplasia and retained throughout disease progression. In present study, we provide further evidence validating MUC5AC as the PAM4 antigen, and locate PAM4-reactive epitope within the N-terminal cysteine-rich subdomain 2 (Cys2), thus differentiating PAM4 from most anti-MUC5AC antibodies known to-date. Specifically, we show (i) PAM4-antigen and MUC5AC were co-localized in multiple human cancer cell lines, including Capan-1, BxPC-3, and CFPAC-1; (ii) MUC5AC-specific siRNA prominently reduced the expression of both MUC5AC and PAM4-antigen in CFPAC-1 cells; (iii) PAM4 preferentially binds to the void-volume fractions from Sepharose-CL2B chromatography of Capan-1 culture supernatants, which were revealed by Western blot to display the ladder pattern characteristic of oligomeric MUC5AC; and (iv) the N-terminal Cys2 within several recombinant MUC5AC fragments is essential for binding to PAM4. These findings shed light on the mechanism of PAM4-based diagnosis and treatment for pancreatic cancer, and guide further exploration of its clinical utility.
PMCID: PMC4414189  PMID: 25595893
MUC5AC; epitope mapping; PAM4; pancreatic cancer; cysteine-rich subdomain
3.  Fractionated Radioimmunotherapy With 90Y-Clivatuzumab Tetraxetan and Low-Dose Gemcitabine Is Active in Advanced Pancreatic Cancer 
Cancer  2012;118(22):5497-5506.
It has been demonstrated that the humanized clivatuzumab tetraxetan (hPAM4) antibody targets pancreatic ductal carcinoma selectively. After a trial of radioimmunotherapy that determined the maximum tolerated dose of single-dose yttrium-90-labeled hPAM4 (90Y-hPAM4) and produced objective responses in patients with advanced pancreatic ductal carcinoma, the authors studied fractionated radioimmunotherapy combined with low-dose gemcitabine in this disease.
Thirty-eight previously untreated patients (33 patients with stage IV disease and 5 patients with stage III disease) received gemcitabine 200 mg/m2 weekly for 4 weeks with 90Y-hPAM4 given weekly in Weeks 2, 3, and 4 (cycle 1), and the same cycle was repeated in 13 patients (cycles 2–4). In the first part of the study, 19 patients received escalating weekly 90Y doses of 6.5 mCi/m2, 9.0 mCi/m2, 12.0 mCi/m2, and 15.0 mCi/m2. In the second portion, 19 additional patients received weekly doses of 9.0 mCi/m2 or 12.0 mCi/m2.
Grade 3/4 thrombocytopenia or neutropenia (according to version 3.0 of the National Cancer Institute’s Common Terminology Criteria for Adverse Events) developed in 28 of 38 patients after cycle 1 and in all retreated patients; no grade >3 nonhematologic toxicities occurred. Fractionated dosing of cycle 1 allowed almost twice the radiation dose compared with single-dose radioimmunotherapy. The maximum tolerated dose of 90Y-hPAM4 was 12.0 mCi/m2 weekly for 3 weeks for cycle 1, with ≤9.0 mCi/m2 weekly for 3 weeks for subsequent cycles, and that dose will be used in future trials. Six patients (16%) had partial responses according to computed tomography-based Response Evaluation Criteria in Solid Tumors, and 16 patients (42%) had stabilization as their best response (58% disease control). The median overall survival was 7.7 months for all 38 patients, including 11.8 months for those who received repeated cycles (46% [6 of 13 patients] ≥1 year), with improved efficacy at the higher radioimmunotherapy doses.
Fractionated radioimmunotherapy with 90Y-hPAM4 and low-dose gemcitabine demonstrated promising therapeutic activity and manageable myelosuppression in patients with advanced pancreatic ductal carcinoma.
PMCID: PMC4215160  PMID: 22569804
combination therapy; gemcitabine; ductal pancreatic cancer; radioimmunotherapy; clivatuzumab tetraxetan; 90Y
4.  Treatment of Advanced Pancreatic Carcinoma with 90Y-Clivatuzumab Tetraxetan: A Phase I Single-Dose Escalation Trial 
Humanized antibody hPAM4 specifically binds a mucin glycoprotein expressed in pancreatic adenocarcinomas. This phase I study evaluated a single dose of 90Y-clivatuzumab tetraxetan (90Y-labeled hPAM4) in patients with advanced pancreatic cancer.
Experimental Design
Twenty-one patients (4 stage III; 17 stage IV) received 111In-hPAM4 for imaging and serum sampling before 90Y-hPAM4. Study procedures evaluated adverse events, safety laboratories, computed tomography (CT) scans, biomarkers, pharmacokinetics, radiation dosimetry, and immunogenicity (HAHA).
111In-hPAM4 showed normal biodistribution with radiation dose estimates to red marrow and solid organs acceptable for radioimmunotherapy and with tumor targeting in 12 patients. One patient withdrew before 90Y-hPAM4; otherwise, 20 patients received 90Y doses of 15 (n = 7), 20 (n = 9), and 25 mCi/m2 (n = 4). Treatment was well tolerated; the only significant drug-related toxicities were (NCI CTC v.3) grade 3 to 4 neutropenia and thrombocytopenia increasing with 90Y dose. There were no bleeding events or serious infections, and most cytopenias recovered to grade 1 within 12 weeks. Three patients at 25 mCi/m2 encountered dose-limiting toxicity with grade 4 cytopenias more than 7 days, establishing 20 mCi/m2 as the maximal tolerated 90Y dose. Two patients developed HAHA of uncertain clinical significance. Most patients progressed rapidly and with CA19-9 levels increasing within 1 month of therapy, but 7 remained progression-free by CT for 1.5 to 5.6 months, including 3 achieving transient partial responses (32%–52% tumor diameter shrinkage).
90Y-Clivatuzumab tetraxetan was well tolerated with manageable hematologic toxicity at the maximal tolerated 90Y dose, and is a potential new therapeutic for advanced pancreatic cancer.
PMCID: PMC4048986  PMID: 21527562
5.  A pretargeting system for tumor PET imaging and radioimmunotherapy 
Labeled antibodies, as well as their fragments and antibody-derived recombinant constructs, have long been proposed as general vectors to target radionuclides to tumor lesions for imaging and therapy. They have indeed shown promise in both imaging and therapeutic applications, but they have not fulfilled the original expectations of achieving sufficient image contrast for tumor detection or sufficient radiation dose delivered to tumors for therapy. Pretargeting was originally developed for tumor immunoscintigraphy. It was assumed that directly-radiolabled antibodies could be replaced by an unlabeled immunoconjugate capable of binding both a tumor-specific antigen and a small molecular weight molecule. The small molecular weight molecule would carry the radioactive payload and would be injected after the bispecific immunoconjugate. It has been demonstrated that this approach does allow for both antibody-specific recognition and fast clearance of the radioactive molecule, thus resulting in improved tumor-to-normal tissue contrast ratios. It was subsequently shown that pretargeting also held promise for tumor therapy, translating improved tumor-to-normal tissue contrast ratios into more specific delivery of absorbed radiation doses. Many technical approaches have been proposed to implement pretargeting, and two have been extensively documented. One is based on the avidin-biotin system, and the other on bispecific antibodies binding a tumor-specific antigen and a hapten. Both have been studied in preclinical models, as well as in several clinical studies, and have shown improved targeting efficiency. This article reviews the historical and recent preclinical and clinical advances in the use of bispecific-antibody-based pretargeting for radioimmunodetection and radioimmunotherapy of cancer. The results of recent evaluation of pretargeting in PET imaging also are discussed.
PMCID: PMC4379897  PMID: 25873896
pretargeting; immunoscintigraphy; immuno-PET; radioimmunotherapy; bispecific antibody
6.  Horizontal Transmission and Retention of Malignancy, as well as Functional Human Genes, After Spontaneous Fusion of Human Glioblastoma and Hamster Host Cells In Vivo 
Cell fusion in vitro has been used to study cancer, gene mapping and regulation, and the production of antibodies via hybridomas. However, in-vivo heterosynkaryon formation by cell-cell fusion has received less attention. This investigation describes the spontaneous fusion of a human glioblastoma with normal hamster cells after xenogeneic transplantation, resulting in malignant cells that express both human and hamster genes and gene products, and retention of glioblastoma traits with an enhanced ability to metastasize. Three of 7 human genes found showed translation of their proteins during serial propagation in vivo or in vitro for years; namely, CD74, CXCR4, and PLAGL2, each implicated with malignancy or glioblastoma. This supports the thesis that genetic hybridization of cancer and normal cells can transmit malignancy and also, as first described herein, regulatory genes involved in the tumor’s organotypic morphology. Evidence also is increasing that even cell-free human cancer DNA can induce malignancy and transfer genetic information to normal cells. Hence, we posit that the transfer of genetic information between tumor and stromal cells, whether by cell-cell fusion or other mechanisms, is implicated in the progression of malignancy, and may further define the crosstalk between cancer cells and their stromal neighbors.
PMCID: PMC3307948  PMID: 21796629
cell fusion; cancer stroma; metastasis; gene transfer; glioblastoma
7.  Interferon-λ1 Linked to a Stabilized Dimer of Fab Potently Enhances both Antitumor and Antiviral Activities in Targeted Cells 
PLoS ONE  2013;8(5):e63940.
The type III interferons (IFNs), comprising IFN-λ1, IFN-λ2, and IFN-λ3, behave similarly to IFN-α in eliciting antiviral, antitumor, and immune-modulating activities. Due to their more restricted cellular targets, IFN-λs are attractive as potential alternatives to existing therapeutic regimens based on IFN-αs. We have applied the DOCK-AND-LOCK™ method to improve the anti-proliferative potency of IFN-λ1 up to 1,000-fold in targeted cancer cell lines by tethering stabilized Fab dimers, derived from hRS7 (humanized anti-Trop-2), hMN-15 (humanized anti-CEACAM6), hL243 (humanized anti-HLA-DR), and c225 (chimeric anti-EGFR), to IFN-λ1 site-specifically, resulting in novel immunocytokines designated (E1)-λ1, (15)-λ1, (C2)-λ1, and (c225)-λ1, respectively. Targeted delivery of IFN-λ1 via (15)-λ1 or (c225)-λ1 to respective antigen-expressing cells also significantly increased antiviral activity when compared with non-targeting (C2)-λ1, as demonstrated in human lung adenocarcinoma cell line A549 by (15)-λ1 against encephalomyocarditis virus (EC50 = 22.2 pM versus 223 pM), and in human hepatocarcinoma cell line Huh-7 by (c225)-λ1 against hepatitis C virus (EC50 = 0.56 pM versus 91.2 pM). These promising results, which are attributed to better localization and stronger binding of IFN-λ1 to antibody-targeted cells, together with the favorable pharmacokinetic profile of (E1)-λ1 in mice (T1/2 = 8.6 h), support further investigation of selective prototypes as potential antiviral and antitumor therapeutic agents.
PMCID: PMC3655979  PMID: 23696859
8.  A New Lyophilized Kit for Rapid Radiofluorination of Peptides 
Bioconjugate Chemistry  2012;23(3):538-547.
Radiolabeling compounds with positron-emitting radionuclides often involves a time-consuming, customized process. Herein, we report a simple lyophilized kit formulation for labeling peptides with 18F, based on the aluminum-fluoride procedure. The prototype kit contains IMP485, a NODA (1,4,7-triazacyclononane-1,4-diacetate)-MPAA (methyl phenylacetic acid)-di-HSG (histamine-succinyl-glycine) hapten-peptide, [NODA-MPAA-D-Lys(HSG)-D-Tyr-D-Lys(HSG)-NH2], used for pretargeting, but we also examined a similar kit formulation for a somatostatin-binding peptide [IMP466, NOTA-D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Throl] bearing a NOTA ligand to determine if the benefits of using a kit can be extended to other AlF-binding peptides. The NODA-MPAA ligand forms a single stable complex with (AlF)2+ in high yields. In order to establish suitable conditions for a facile kit, the formulation was optimized for pH, peptide to Al3+ ratio, bulking agent, radioprotectant, and the buffer. For optimal labeling, the kit was reconstituted with an aqueous solution of 18F− and ethanol (1:1), heated at 100–110 °C for 15 min, and then simply and rapidly purified using one of two equally effective solid-phase extraction (SPE) methods. Al18F-IMP485 was isolated as a single isomer complex, in high yield (45–97%) and high specific activity (up to 223 GBq/μmol), within 20 min. The labeled product was stable in human serum at 37 °C for 4 h and in vivo, urine samples showed the intact product was eliminated. Tumor targeting of the Al18F-IMP485 in nude mice bearing human colon cancer xenografts pretargeted with an anti-CEACAM5 bispecific antibody showed very low uptake (0.06% ± 0.02 ID/g) in bone, further illustrating its stability. At 1 h, pretargeted animals had high Al18F-IMP485 tumor uptake (28.1% ± 4.5 ID/g), with ratios of 9 ± 4, 123 ± 38, 110 ± 43 and 120 ± 108 for kidney, liver, blood and bone, respectively. Tumor uptake remained high at 3 h post-injection, with increased tumor/nontumor ratios. The NOTA-somatostatin-binding peptide also was fluorinated with good yield and high specific activity in the same kit formulation. However, yields were somewhat lower than those achieved with IMP485 containing the NODA-MPAA ligand, likely reflecting this ligand's superior binding properties over the simple NOTA. These studies indicate that 18F-labeled peptides can be reproducibly prepared as stable Al-F complexes with good radiochemical yield and high specific activity using a simple, one-step, lyophilized kit followed by a rapid purification by SPE that provides the 18F-peptide, ready for patient injection within 30 min.
PMCID: PMC3310340  PMID: 22273147
bispecific antibody; fluorine-18; pretargeting; peptides; antibodies; molecular imaging; PET; somatostatin
9.  CD74 interferes with the expression of fas receptor on the surface of lymphoma cells 
Resistance to Fas-mediated apoptosis limits the efficacy of currently available chemotherapy regimens. We identified CD74, which is known to be overexpressed in hematological malignancies, as one of the factors interfering with Fas-mediated apoptosis.
CD74 expression was suppressed in human B-lymphoma cell lines, BJAB and Raji, by either transduction with lentivirus particles or transfection with episomal vector, both encoding CD74-specific shRNAs or non-target shRNA. Effect of CD74 expression on Fas signaling was evaluated by comparing survival of mice hydrodynamically transfected with vector encoding full-length CD74 or empty vector. Sensitivity of cells with suppressed CD74 expression to FasL, edelfosine, doxorubicin, and a humanized CD74-specific antibody, milatuzumab, was evaluated by flow cytometry and compared to control cells. Fas signaling in response to FasL stimulation and the expression of Fas signaling components were evaluated by Western blot. Surface expression of Fas was detected by flow cytometry.
We determined that cells with suppressed CD74 are more sensitive to FasL-induced apoptosis and Fas signaling-dependent chemotherapies, edelfosine and doxorubicin, than control CD74-expressing cells. On the other hand, expression of full-length CD74 in livers protected the mice from a lethal challenge with agonistic anti-Fas antibody Jo2. A detailed analysis of Fas signaling in cells lacking CD74 and control cells revealed increased cleavage/activation of pro-caspase-8 and corresponding enhancement of caspase-3 activation in the absence of CD74, suggesting that CD74 affects the immediate early steps in Fas signaling at the plasma membrane. Cells with suppressed CD74 expression showed increased staining of Fas receptor on their surface. Pre-treatment with milatuzumab sensitized BJAB cells to Fas-mediated apoptosis.
We anticipate that specific targeting of the CD74 on the cell surface will sensitize CD74-expressing cancer cells to Fas-mediated apoptosis, and thus will increase effectiveness of chemotherapy regimens for hematological malignancies.
PMCID: PMC4210479  PMID: 25304249
10.  Monoclonal antibodies targeting CD20 
mAbs  2013;5(3):335-336.
PMCID: PMC4169026  PMID: 23493149
11.  In-Vivo Fusion of Human Cancer and Hamster Stromal Cells Permanently Transduces and Transcribes Human DNA 
PLoS ONE  2014;9(9):e107927.
After demonstrating, with karyotyping, polymerase chain reaction (PCR) and fluorescence in-situ hybridization, the retention of certain human chromosomes and genes following the spontaneous fusion of human tumor and hamster cells in-vivo, it was postulated that cell fusion causes the horizontal transmission of malignancy and donor genes. Here, we analyzed gene expression profiles of 3 different hybrid tumors first generated in the hamster cheek pouch after human tumor grafting, and then propagated in hamsters and in cell cultures for years: two Hodgkin lymphomas (GW-532, GW-584) and a glioblastoma multiforme (GB-749). Based on the criteria of MAS 5.0 detection P-values ≤0.065 and at least a 2-fold greater signal expression value than a hamster melanoma control, we identified 3,759 probe sets (ranging from 1,040 to 1,303 in each transplant) from formalin-fixed, paraffin-embedded sections of the 3 hybrid tumors, which unambiguously mapped to 3,107 unique Entrez Gene IDs, representative of all human chromosomes; however, by karyology, one of the hybrid tumors (GB-749) had a total of 15 human chromosomes in its cells. Among the genes mapped, 39 probe sets, representing 33 unique Entrez Gene IDs, complied with the detection criteria in all hybrid tumor samples. Five of these 33 genes encode transcription factors that are known to regulate cell growth and differentiation; five encode cell adhesion- and transmigration-associated proteins that participate in oncogenesis and/or metastasis and invasion; and additional genes encode proteins involved in signaling pathways, regulation of apoptosis, DNA repair, and multidrug resistance. These findings were corroborated by PCR and reverse transcription PCR, showing the presence of human alphoid (α)-satellite DNA and the F11R transcripts in additional tumor transplant generations. We posit that in-vivo fusion discloses genes implicated in tumor progression, and gene families coding for the organoid phenotype. Thus, cancer cells can transduce adjacent stromal cells, with the resulting progeny having permanently transcribed genes with malignant and other gene functions of the donor DNA. Using heterospecific in-vivo cell fusion, genes encoding oncogenic and organogenic traits may be identified.
PMCID: PMC4178054  PMID: 25259521
12.  High-Yielding Aqueous 18F-Labeling of Peptides via Al18F chelation 
Bioconjugate chemistry  2011;22(9):1793-1803.
The coordination chemistry of a new pentadentate bifunctional chelator (BFC), NODA-MPAA 1, containing the 1,4,7-triazacyclononane-1,4-diacetate (NODA) motif with a methyl phenyl acetic acid (MPAA) backbone, and its ability to form stable Al18F-chelates, was investigated. The organofluoroaluminates were easily accessible from the reaction of 1 and AlF3. X-ray diffraction studies revealed aluminum at the center of a slightly distorted octahedron, with fluorine occupying one of the axial positions. The tert-butyl protected prochelator 7, which can be synthesized in one step, is useful for coupling to biomolecules on solid phase or in solution. High yield (55–89%) aqueous 18F-labeling was achieved in 10–15 minutes with a tumor-targeting peptide 4 covalently linked to 1. Defluorination was not observed for at least 4 h in human serum at 37 °C. These results demonstrate the facile application of Al18F chelation using BFC 1 as a versatile labeling method for radiofluorinating other heat-stable peptides for positron emission imaging.
PMCID: PMC3178738  PMID: 21805975
13.  Imaging integrin alpha-v-beta-3 expression in tumors with an 18F-labeled dimeric RGD peptide 
Integrin αvβ3 receptors are expressed on activated endothelial cells during neovascularization to maintain tumor growth. Many radiolabeled probes utilize the tight and specific association between the arginine-glycine-aspartatic acid (RGD) peptide and integrin αvβ3, but one main obstacle for any clinical application of these probes is the laborious multistep radiosynthesis of 18F. In this study, the dimeric RGD peptide, E-[c(RGDfK)]2, was conjugated with NODAGA and radiolabeled with 18F in a simple one-pot process with a radiolabeling yield of 20%; the whole process lasting only 45 min. NODAGA-E-[c(RGDfK)]2 labeled with 18F at a specific activity of 1.8 MBq/nmol and a radiochemical purity of 100% could be achieved. Log P value of 18F-labeled NODAGA-E-[c(RGDfK)]2 was −4.26 ± 0.02. In biodistribution studies, 18F-NODAGA-E-[c(RGDfK)]2 cleared rapidly from the blood with 0.03 ± 0.01 %ID/g in the blood at 2 h p.i., mainly via the kidneys and showed good in vivo stability. Tumor uptake of 18F-NODAGA-E-[c(RGDfK)]2 (3.44 ± 0.20 %ID/g, 2 h p.i.) was significantly lower than that of reference compounds 68Ga-labeled NODAGA-E-[c(RGDfK)]2 (6.26 ± 0.76 %ID/g; P <0.001) and 111In-labeled NODAGA-E-[c(RGDfK)]2 (4.99 ± 0.64 %ID/g; P < 0.01). Co-injection of an excess of unlabeled NODAGA-E-[c(RGDfK)]2 along with 18F-NODAGA-E-[c(RGDfK)]2 resulted in significantly reduced radioactivity concentrations in the tumor (0.85 ± 0.13 %ID/g). The αvβ3 integrin-expressing SK-RC-52 tumor could be successfully visualized by microPET with 18F-labeled NODAGA-E-[c(RGDfK)]2. In conclusion, NODAGA-E-[c(RGDfK)]2 could be labeled rapidly with 18F using a direct aqueous, one-pot method and it accumulated specifically in αvβ3 integrin-expressing SK-RC-52 tumors, allowing for visualization by microPET.
PMCID: PMC4034708  PMID: 23606427
Integrin alpha-v-beta-3; PET; radiofluorination; aluminum fluoride; RGD; NODAGA
14.  Anti-CD22/CD20 Bispecific Antibody with Enhanced Trogocytosis for Treatment of Lupus 
PLoS ONE  2014;9(5):e98315.
The humanized anti-CD22 antibody, epratuzumab, has demonstrated therapeutic activity in clinical trials of lymphoma, leukemia and autoimmune diseases, treating currently over 1500 cases of non-Hodgkin lymphoma, acute lymphoblastic leukemias, Waldenström’s macroglobulinemia, Sjögren’s syndrome, and systemic lupus erythematosus. Because epratuzumab reduces on average only 35% of circulating B cells in patients, and has minimal antibody-dependent cellular cytotoxicity and negligible complement-dependent cytotoxicity when evaluated in vitro, its therapeutic activity may not result completely from B-cell depletion. We reported recently that epratuzumab mediates Fc/FcR-dependent membrane transfer from B cells to effector cells via trogocytosis, resulting in a substantial reduction of multiple BCR modulators, including CD22, CD19, CD21, and CD79b, as well as key cell adhesion molecules, including CD44, CD62L, and β7 integrin, on the surface of B cells in peripheral blood mononuclear cells obtained from normal donors or SLE patients. Rituximab has clinical activity in lupus, but failed to achieve primary endpoints in a Phase III trial. This is the first study of trogocytosis mediated by bispecific antibodies targeting neighboring cell-surface proteins, CD22, CD20, and CD19, as demonstrated by flow cytometry and immunofluorescence microscopy. We show that, compared to epratuzumab, a bispecific hexavalent antibody comprising epratuzumab and veltuzumab (humanized anti-CD20 mAb) exhibits enhanced trogocytosis resulting in major reductions in B-cell surface levels of CD19, CD20, CD21, CD22, CD79b, CD44, CD62L and β7-integrin, and with considerably less immunocompromising B-cell depletion that would result with anti-CD20 mAbs such as veltuzumab or rituximab, given either alone or in combination with epratuzumab. A CD22/CD19 bispecific hexavalent antibody, which exhibited enhanced trogocytosis of some antigens and minimal B-cell depletion, may also be therapeutically useful. The bispecific antibody is a candidate for improved treatment of lupus and other autoimmune diseases, offering advantages over administration of the two parental antibodies in combination.
PMCID: PMC4026529  PMID: 24841238
15.  Trop-2-targeting tetrakis-ranpirnase has potent antitumor activity against triple-negative breast cancer 
Molecular Cancer  2014;13:53.
Ranpirnase (Rap) is an amphibian ribonuclease with reported antitumor activity, minimal toxicity, and negligible immunogenicity in clinical studies, but the unfavorable pharmacokinetics and suboptimal efficacy hampered its further clinical development. To improve the potential of Rap-based therapeutics, we have used the DOCK-AND-LOCK™ (DNL™) method to construct a class of novel IgG-Rap immunoRNases. In the present study, a pair of these constructs, (Rap)2-E1-(Rap)2 and (Rap)2-E1*-(Rap)2, comprising four copies of Rap linked to the CH3 and CK termini of hRS7 (humanized anti-Trop-2), respectively, were evaluated as potential therapeutics for triple-negative breast cancer (TNBC).
The DNL-based immunoRNases, (Rap)2-E1-(Rap)2 and (Rap)2-E1*-(Rap)2, were characterized and tested for biological activities in vitro on a panel of breast cancer cell lines and in vivo in a MDA-MB-468 xenograft model.
(Rap)2-E1-(Rap)2 was highly purified (>95%), exhibited specific cell binding and rapid internalization in MDA-MB-468, a Trop-2-expressing TNBC line, and displayed potent in vitro cytotoxicity (EC50 ≤ 1 nM) against diverse breast cancer cell lines with moderate to high expression of Trop-2, including MDA-MB-468, BT-20, HCC1806, SKBR-3, and MCF-7. In comparison, structural counterparts of (Rap)2-E1-(Rap)2, generated by substituting hRS7 with selective non-Trop-2-binding antibodies, such as epratuzumab (anti-CD22), were at least 50-fold less potent than (Rap)2-E1-(Rap)2 in MDA-MB-468 and BT-20 cells, both lacking the expression of the cognate antigen. Moreover, (Rap)2-E1-(Rap)2 was less effective (EC50 > 50 nM) in MDA-MB-231 (low Trop-2) or HCC1395 (no Trop-2), and did not show any toxicity to human peripheral blood mononuclear cells. In a mouse TNBC model, a significant survival benefit was achieved with (Rap)2-E1*-(Rap)2 when given the maximal tolerated dose.
A new class of immunoRNases was generated with enhanced potency for targeted therapy of cancer. The promising results from (Rap)2-E1-(Rap)2 and (Rap)2-E1*-(Rap)2 support their further investigation as a potential treatment option for TNBC and other Trop-2-expressing cancers.
PMCID: PMC4015355  PMID: 24606732
Ranpirnase; Trop-2; DOCK-AND-LOCK™; ImmunoRNase; Breast cancer
16.  CD84 is a survival receptor for CLL cells 
Oncogene  2013;33(8):1006-1016.
Chronic lymphocytic leukemia (CLL) is a malignancy of mature lymphocytes that is manifest by the progressive accumulation of transformed cells, mostly due to their decreased apoptosis. CD84 belongs to the Signaling Lymphocyte Activating Molecule (SLAM) family of immunoreceptors and has an as yet unknown function in normal B cells and CLL lymphocytes. We show that CD84 is over-expressed in CLL cells. Activation of cell surface CD84 initiates a signaling cascade, which enhances cell survival. Both immunoneutralization or blockade of CD84 induce cell death in vitro and in vivo. Thus, overexpression of CD84 from an early stage may be critical for the survival of CLL. These findings suggest novel therapeutic strategies based on the blockade of a CD84 dependent survival pathway.
PMCID: PMC3796123  PMID: 23435417
18.  PAM4 Immunoassay Alone and in Combination with CA19-9 for the Detection of Pancreatic Adenocarcinoma 
Cancer  2012;119(3):522-528.
Monoclonal antibody PAM4 has high specificity for pancreatic ductal adenocarcinoma (PDAC), as well as its precursor lesions, but is not reactive with normal and benign pancreatic tissues. Our purpose was to evaluate a PAM4-based serum-immunoassay alone, and in combination with the CA19-9 assay, for the detection of PDAC with particular attention to early-stage disease.
Sera from patients with confirmed PDAC (N=298), other cancers (N=99), benign disease of the pancreas (N=120), and healthy adults (N=79) were evaluated by specific enzyme-immunoassay for concentration of PAM4 and CA19-9 antigen levels by blinded analyses. All tests for statistical significance were two-sided.
Overall sensitivity for PAM4 detection of PDAC was 76%, with 64% of stage-1 patients also identified. The detection rate was considerably higher (85%) for advanced disease. The assay showed high specificity compared to benign pancreatic disease (85%), with a positive likelihood ratio (+LR) of 4.93. CA19-9 provided an overall sensitivity of 77%, and was positive in 58% of patients with stage-1 disease; however, specificity was significantly lower for CA19-9 (68%) with a +LR=2.85 (P=0.026 compared to PAM4). Importantly, a combined PAM4/CA19-9 assay demonstrated an improved sensitivity (84%) for overall detection of PDAC without significant loss of specificity (82%), as compared to either arm alone.
The PAM4-immunoassay identified approximately two-thirds of stage-1 PDAC patients with high discriminatory power with respect to benign, non-neoplastic pancreatic disease. These results provide a rationale for testing patient groups considered at high-risk for PDAC with a combined PAM4/CA19-9 biomarker assay for detection of early-stage PDAC.
PMCID: PMC3502643  PMID: 22898932
pancreatic cancer; pancreatitis; diagnosis; early detection; PAM4; CA19-9
19.  Milatuzumab-Conjugated Liposomes as Targeted Dexamethasone Carriers for Therapeutic Delivery in CD74+ B-cell Malignancies 
Corticosteroids are widely used for the treatment of B-cell malignancies, including non-Hodgkin lymphoma, chronic lymphocytic leukemia (CLL), and acute lymphoblastic leukemia; however, this class of drug is associated with undesirable off-target effects. Herein, we developed novel milatuzumab-conjugated liposomes as a targeted dexamethasone carrier for therapeutic delivery in CD74+ B-cell malignancies and explored its effect against the disease.
Experimental Design:
The targeting efficiency of milatuzumab-targeted liposomes to CD74+ cells was evaluated in vitro. The effect of CD74-targeted liposomal dexamethasone was compared with free dexa-methasone in primary CLL cells and cell lines in vitro. The therapeutic efficacy of CD74-targeted liposomal dexamethasone was evaluated in a Raji-severe combined immunodeficient (SCID) xenograft model in vivo.
Milatuzumab-targeted liposomes promoted selective incorporation of carrier molecules into transformed CD74-positive B cells as compared with CD74-negative T-cells. The CD74-dexamethasone-targeted liposomes (CD74-IL-DEX) promoted and increased killing in CD74-positive tumor cells and primary CLL cells. Furthermore, the targeted drug liposomes showed enhanced therapeutic efficacy against a CD74-positive B-cell model as compared with free, or non-targeted, liposomal dexamethasone in SCID mice engrafted with Raji cells in vivo.
These studies provide evidence and support for a potential use of CD74-targeted liposomal dexamethasone as a new therapy for B-cell malignancies.
PMCID: PMC3793126  PMID: 23209030
20.  Epratuzumab for patients with moderate to severe flaring SLE: health-related quality of life outcomes and corticosteroid use in the randomized controlled ALLEVIATE trials and extension study SL0006 
Rheumatology (Oxford, England)  2013;53(3):502-511.
Objective. To evaluate health-related quality of life (HRQOL) and corticosteroid use in patients with moderate to severely active SLE enrolled in two international, multicentre, randomized controlled trials of epratuzumab (ALLEVIATE-1 and -2) and a long-term extension study (SL0006).
Methods. Ninety ALLEVIATE patients (43% BILAG A, mean BILAG score 13.2) were randomized to receive 360 mg/m2 (n = 42) or 720 mg/m2 (n = 11) epratuzumab or placebo (n = 37), plus standard of care, in 12-week cycles. Corticosteroid use, patient and physician global assessments of disease activity (PtGA and PGA) and 36-item Medical Outcomes Survey Short Form (SF-36) results were recorded at baseline and every 4 weeks. Both trials were prematurely discontinued due to a drug supply interruption; patients followed for ≥6 months were analysed. Twenty-nine patients continued in SL0006, with interim analysis at a median exposure of 120 (range 13–184) weeks.
Results. At week 12, proportions of patients with a PGA ≥20% above baseline or with a PtGA improvement greater than or equal to the minimum clinically important difference were higher in the epratuzumab arms than the placebo arm. PGA and PtGA improvements were sustained but did not reach statistical significance. At week 24, mean cumulative corticosteroid doses with epratuzumab 360 and 720 mg/m2 were 1051 and 1973 mg less than placebo (P = 0.034 and 0.081, respectively). At week 48, SF-36 scores approached or exceeded US age- and gender-matched norms in five domains with the 360 mg/m2 treatment. Improvements were maintained in SL0006 over ∼2 years.
Conclusion. Epratuzumab treatment produced clinically meaningful and sustained improvements in PGA, PtGA and HRQOL and reductions in corticosteroid doses.
PMCID: PMC3930886  PMID: 24273022
epratuzumab; CD22; ALLEVIATE; lupus; SLE; HRQOL; SF-36; corticosteroids; clinical trial; monoclonal antibody
21.  Mapping PAM4 (clivatuzumab), a monoclonal antibody in clinical trials for early detection and therapy of pancreatic ductal adenocarcinoma, to MUC5AC mucin 
Molecular Cancer  2013;12:143.
PAM4, an antibody that has high specificity for pancreatic ductal adenocarcinoma (PDAC), compared to normal pancreas, benign lesions of the pancreas, and cancers originating from other tissues, is being investigated as a biomarker for early detection, as well as antibody-targeted imaging and therapy. Therefore, the identity of the antigen bound by this monoclonal antibody (MAb) can provide information leading to improved use of the antibody. Prior results suggested the antigen is a mucin-type glycoprotein rich in cysteine disulfide bridges that provide stable conformation for the PAM4-epitope.
Indirect and sandwich enzyme immunoassays (EIA) were performed to compare and contrast the reactivity of PAM4 with several anti-mucin antibodies having known reactivity to specific mucin species (e.g., MUC1, MUC4, MUC5AC, etc.). Studies designed to block reactivity of PAM4 with its specific antigen also were performed.
We demonstrate that MAbs 2-11 M1 and 45 M1, each reactive with MUC5AC, are able to provide signal in a heterologous sandwich immunoassay where PAM4 is the capture antibody. Further, we identify MAbs 21 M1, 62 M1, and 463 M1, each reactive with MUC5AC, as inhibiting the reaction of PAM4 with its specific epitope. MAbs directed to MUC1, MUC3, MUC4, MUC16 and CEACAM6 are not reactive with PAM4-captured antigen, nor are they able to block the reaction of PAM4 with its antigen.
These data implicate MUC5AC as a specific mucin species to which PAM4 is reactive. Furthermore, this realization may allow for the improvement of the current PAM4 serum-based immunoassay for detection of early-stage PDAC by the application of anti-MUC5AC MAbs as probes in this sandwich EIA.
PMCID: PMC4015478  PMID: 24257318
Pancreatic cancer; Early detection; PAM4; MUC5AC; Clivatuzumab; Enzyme immunoassay
22.  Radiofluorination using aluminum-fluoride (Al18F) 
EJNMMI Research  2013;3:36.
Targeted agents are increasingly used for treating cancer and other diseases, but patients may need to be carefully selected to maximize the potential for therapeutic benefit. One way to select patients is to bind an imaging radionuclide to a targeting agent of interest, so that its uptake in specific sites of disease can be visualized by positron-emission tomography (PET) or single-photon emission computed tomography.
18F is the most commonly used radionuclide for PET imaging. Its half-life of approximately 2 h is suited for same-day imaging of many compounds that clear quickly from the body to allow visualization of uptake in the intended target. A significant impediment to its use, however, is the challenging coupling of 18F to a carbon atom of the targeting agent. Because fluorine binds to aluminum, we developed a procedure where the Al18F complex could be captured by a chelate, thereby greatly simplifying the way that imaging agents can be fluorinated for PET imaging. This article reviews our experience with this technology.
PMCID: PMC3665500  PMID: 23651690
Radiofluorination; Fluorine-18; Peptides; PET; Molecular imaging; Review
23.  Targeting both IGF-1R and mTOR synergistically inhibits growth of renal cell carcinoma in vitro 
BMC Cancer  2013;13:170.
Advanced or metastatic renal cell carcinoma (RCC) has a poor prognosis, because it is relatively resistant to conventional chemotherapy or radiotherapy. Treatments with human interferon-α2b alone or in combination with mammalian target of rapamycin (mTOR) inhibitors have led to only a modest improvement in clinical outcome. One observation made with mTOR inhibitors is that carcinomas can overcome these inhibitory effects by activating the insulin-like growth factor-I (IGF-I) signaling pathway. Clinically, there is an association of IGF-I receptor (IGF-IR) expression in RCC and poor long-term patient survival. We have developed a humanized anti-IGF-IR monoclonal antibody, hR1, which binds to RCC, resulting in effective down-regulation of IGF-IR and moderate inhibition of cell proliferation in vitro. In this work, we evaluate the anti-tumor activity of two novel IGF-1R-targeting agents against renal cell carcinoma given alone or in combination with an mTOR inhibitor.
hR1 was linked by the DOCK-AND-LOCK™ (DNL™) method to four Fabs of hR1, generating Hex-hR1, or to four molecules of interferon-α2b, generating 1R-2b. Eight human RCC cell lines were screened for IGF-1R expression and sensitivity to treatment with hR1 in vitro. Synergy with an mTOR inhibitor, temsirolimus, was tested in a cell line (ACHN) with low sensitivity to hR1.
Hex-hR1 induced the down-regulation of IGF-IR at 10-fold lower concentrations compared to the parental hR1. Sensitivity to growth inhibition mediated by hR1 and Hex-hR1 treatments correlated with IGF-1R expression (higher expression was more sensitive). The potency of 1R-2b to inhibit the in vitro growth of RCC was also demonstrated in two human cell lines, ACHN and 786-O, with EC50–values of 63 and 48 pM, respectively. When combined with temsirolimus, a synergistic growth-inhibition with hR1, Hex-hR1, and 1R-2b was observed in ACHN cells at concentrations as low as 10 nM for hR1, 1 nM for Hex-hR1, and 2.6 nM for 1R-2b.
Both Hex-hR1 and 1R-2b proved to be more potent than parental hR1 in inhibiting growth of RCC in vitro. Synergy was achieved when each of the three hR1-based agents was combined with temsirolimus, suggesting a new approach for treating RCC.
PMCID: PMC3623828  PMID: 23548153
Dock-and-Lock; Renal cell carcinoma; Insulin-like growth factor-I receptor; Hex-hR1; 1R-2b; mTOR inhibitors
24.  Horizontal Transmission of Malignancy: In-Vivo Fusion of Human Lymphomas with Hamster Stroma Produces Tumors Retaining Human Genes and Lymphoid Pathology 
PLoS ONE  2013;8(2):e55324.
We report the in-vivo fusion of two Hodgkin lymphomas with golden hamster cheek pouch cells, resulting in serially-transplanted (over 5–6 years) GW-532 and GW-584 heterosynkaryon tumor cells displaying both human and hamster DNA (by FISH), lymphoma-like morphology, aggressive metastasis, and retention of 7 human genes (CD74, CXCR4, CD19, CD20, CD71, CD79b, and VIM) out of 24 tested by PCR. The prevalence of B-cell restricted genes (CD19, CD20, and CD79b) suggests that this uniform population may be the clonal initiating (malignant) cells of Hodgkin lymphoma, despite their not showing translation to their respective proteins by immunohistochemical analysis. This is believed to be the first report of in-vivo cell-cell fusion of human lymphoma and rodent host cells, and may be a method to disclose genes regulating both organoid and metastasis signatures, suggesting that the horizontal transfer of tumor DNA to adjacent stromal cells may be implicated in tumor heterogeneity and progression. The B-cell gene signature of the hybrid xenografts suggests that Hodgkin lymphoma, or its initiating cells, is a B-cell malignancy.
PMCID: PMC3566191  PMID: 23405135
25.  The radiolabeling of proteins by the [18F]AlF method 
A new ([18F]AlF)2+-binding ligand that contains 1,4,7-triazacyclononane-1,4-diacetate (NODA) attached to a methyl phenylacetic acid group (MPA) was conjugated to N-(2-aminoethyl)maleimide (EM) to form NODA-MPAEM. The NODA-MPAEM was labeled with ([18F]AlF)2+ at 105 °C in 49–82% yield and conjugated at room temperature to an antibody Fab’ fragment in 69–80% yield (total time ~ 50 min) and with retention of immunoreactivity. These data indicate that the rapid and simple [18F]AlF-labeling method can be easily adapted for preparing heat-sensitive compounds with 18F quickly and in high yields.
PMCID: PMC3215893  PMID: 21890371
aluminum fluoride; antibody; CEA; 18fluorine; radiolabeling; PET

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