Selective High-Affinity Ligand Antibody Mimics for Cancer Diagnosis and Therapy: Initial Application to Lymphoma/Leukemia

The small molecule antibody mimic SH7139 targets a family of HLA-DRs expressed by B-cell lymphomas and other solid cancers

Selective high-affinity ligands (SHALs) belong to a novel class of small-molecule cancer therapeutics that function as targeted prodrugs. SH7139, the most advanced of the SHAL drugs designed to bind to a unique β-subunit structural epitope located on HLA-DR10, has exhibited exceptional preclinical efficacy and safety profiles. A comparison of SH7139 and SH7129, a biotin derivative of the drug developed for use as a diagnostic, showed the incorporation of a biotin tag did not alter the SHALs ability to target or kill HLA-DR10 expressing Raji cells. The use of SH7129 in an immuno-histochemical type assay to stain peripheral blood mononuclear cells (PBMCs) obtained from individuals expressing specific HLA-DRB1 alleles has also revealed that in addition to HLA-DR10, seven other more commonly expressed HLA-DRs are targeted by the drug. Computational dockings of the SHAL's recognition ligands to a number of HLA-DR structures explain, in part, why the targeting domains of SH7129 and SH7139 bind to some HLA-DRs but not others. The results also substantiate the selectivity of SH7129 and suggest it may prove useful as a companion diagnostic for pre-screening biopsy samples to identify those patients whose tumours should respond to SH7139 therapy.

Novel Methods to Improve the Efficiency of Radioimmunotherapy for Non-Hodgkin Lymphoma

Radioimmunotherapy (RIT) is a novel strategy for treating non-Hodgkin lymphoma (NHL). Several studies have shown the promising results of using RIT in NHL, which have led to FDA approval for two RIT agents in treating low grade NHL. In spite of these favorable results in low-grade NHL, most of the aggressive or relapsed/refractory NHL subjects experience relapses following RIT. Although more aggressive treatments such as myeloablative doses of RIT followed by stem cell transplantation appear to be able to provide a longer survival for some patients these approaches are associated with significant treatment-related adverse events and challenging to deliver in most centers. Therefore, it seems reasonable to develop treatment approaches that enhance the efficiency of RIT, while reducing its toxicity. In this paper, novel methods that improve the efficiency of RIT and reduce its toxicity through various mechanisms are reviewed. Further clinical development of these methods could expand the NHL patient groups eligible for receiving RIT, and even extend the use of RIT to new indications and disease groups in future.

High-Performance Concurrent Chemo-Immuno-Radiotherapy for the Treatment of Hematologic Cancer through Selective High-Affinity Ligand Antibody Mimic-Functionalized Doxorubicin-Encapsulated Nanoparticles

Non-Hodgkin lymphoma is one of the most common types of cancer. Relapsed and refractory diseases are still common and remain significant challenges as the majority of these patients eventually succumb to the disease. Herein, we report a translatable concurrent chemo-immuno-radiotherapy (CIRT) strategy that utilizes fully synthetic antibody mimic Selective High-Affinity Ligand (SHAL)-functionalized doxorubicin-encapsulated nanoparticles (Dox NPs) for the treatment of human leukocyte antigen-D related (HLA-DR) antigen-overexpressed tumors. We demonstrated that our tailor-made antibody mimic-functionalized NPs bound selectively to different HLA-DR-overexpressed human lymphoma cells, cross-linked the cell surface HLA-DR, and triggered the internalization of NPs. In addition to the direct cytotoxic effect by Dox, the internalized NPs then released the encapsulated Dox and upregulated the HLA-DR expression of the surviving cells, which further augmented immunogenic cell death (ICD). The released Dox not only promotes ICD but also sensitizes the cancer cells to irradiation by inducing cell cycle arrest and preventing the repair of DNA damage. In vivo biodistribution and toxicity studies confirm that the targeted NPs enhanced tumor uptake and reduced systemic toxicities of Dox. Our comprehensive in vivo anticancer efficacy studies using lymphoma xenograft tumor models show that the antibody-mimic functional NPs effectively inhibit tumor growth and sensitize the cancer cells for concurrent CIRT treatment without incurring significant side effects. With an appropriate treatment schedule, the SHAL-functionalized Dox NPs enhanced the cell killing efficiency of radiotherapy by more than 100% and eradicated more than 80% of the lymphoma tumors.

The clinical potential of circulating tumor cells; the need to incorporate a modern "immunological cocktail" in the assay

The accepted clinical assay, CellSearch^®, and lab-on-a-chip tests for capturing circulating tumor cells are antibody-mediated. Attempts to improve their sensitivity have relied upon physical changes in the instruments. There have been no significant advances in improving the antibody-mediated portion of the capture. Modern immunologic engineering offers major possibilities for improving the sensitivity and other features of the assay. These include obtaining univalent antibody fragments such as scFvs with picomolar binding affinity and sufficient specificity; altering them to enhance their range of potential contact with target antigens; using antibodies directed against different epitopes on epithelial, mesenchymal or organ-specific cell surface markers to allow simultaneous binding and investigating non-antibody binding molecules as substitutes for antibody. These maneuvers could markedly improve the ability of current assays to improve patient care and might result in an acceptable test for detecting cancer earlier in high risk patients.

Quantitation of nanoparticle accumulation in flow using optimized microfluidic chambers

BACKGROUND

The vascular cell adhesion molecule-1 (VCAM-1) targeting peptide sequence, VHPKQHR, is a promising moiety for targeting atherosclerosis through incorporation into nanoparticles such as dendrimers and liposomes.

PURPOSE

We aim to develop VCAM-1-targeted nanoparticles that effectively accumulate on the endothelium under shear conditions and to develop robust microfluidic chambers able to house sufficient cells for flow cytometric measurements.

METHODS

Carboxyfluorescein-labeled monomeric VHP-peptide, tetrameric VHP-dendrimers (bisbidentate or radial architecture, with or without N-terminal acetylation) and VHP-peptide liposomes were prepared. Human umbilical vein endothelial cells were treated with nanoparticles under 0 or 2.9 dyne/cm(2) shear, and particle binding was quantified. Flow chambers cured at various temperatures, with or without glass backings were fabricated, characterized for deformation and applied in experiments.

RESULTS

Although liposomes accumulated with highest efficiency, dendrimers also demonstrated specific binding. N-terminal acetylation significantly reduced dendrimer binding, and despite shorter movement range, bisbidentate dendrimers outperformed radial dendrimers, suggesting multiple epitope presence within its estimated arm-span of 57 Å. Under shear, while liposome binding increased 300%, dendrimer binding to cells decreased 65%. Through higher temperature curing and glass backing insertion, polydimethylsiloxane flow chambers maintaining rectangular cross-section with aspect-ratio as low as 1:111 were achieved.

CONCLUSION

Optimized dendrimers and liposomal nanocarriers specifically accumulated onto cells within microfluidic chambers.

Preparation of human scFv antibody against nasopharyngeal carcinoma and identification of its specificity

Abstract Conclusion: The selected scFv antibody could specifically recognize and target nasopharyngeal carcinoma (NPC), and could be applied to clinical diagnosis and therapy.

OBJECTIVE

The aim was to construct and screen fully human anti-NPC single chain Fv fusion phage libraries, and to identify the specificity of the scFv antibody.

METHODS

Peripheral blood mononuclear cells of patients with NPC were immunized in vitro by NPC cells and transformed by Epstein-Barr virus. The total RNAwas used to construct the scFv libraries. By means of ELISA and immunochemistry, the positively bound scFv was selected and identified. The positive scFv was fused to EGFP, and was then expressed in E. coli strain BL21 (DE3) and purified. Furthermore, we observed the binding bioactivity.

RESULTS

The fusion protein has the biological activity of binding the NPC cells and emitting green fluorescence. In targeting experiments in vivo, the results showed that the fusion protein can successfully target the NPC.

Synthesis and biological analysis of prostate-specific membrane antigen-targeted anticancer prodrugs

Ligand-targeted therapeutics have increased in prominence because of their potential for improved potency and reduced toxicity. However, with the advent of personalized medicine, a need for greater versatility in ligand-targeted drug design has emerged, where each tumor-targeting ligand should be capable of delivering a variety of therapeutic agents to the same tumor, each therapeutic agent being selected for its activity on a specific patient's cancer. In this report, we describe the use of a prostate-specific membrane antigen (PSMA)-targeting ligand to deliver multiple unrelated cytotoxic drugs to human prostate cancer (LNCaP) cells. We demonstrate that the PSMA-specific ligand, 2-[3-(1, 3-dicarboxy propyl)ureido] pentanedioic acid, is capable of mediating the targeted killing of LNCaP cells with many different therapeutic warheads. These results suggest that flexibility can be designed into ligand-targeted therapeutics, enabling adaptation of a single targeting ligand for the treatment of patients with different sensitivities to different chemotherapies.

Improved cancer therapy and molecular imaging with multivalent, multispecific antibodies

Antibodies are highly versatile proteins with the ability to be used to target diverse compounds, such as radionuclides for imaging and therapy, or drugs and toxins for therapy, but also can be used unconjugated to elicit therapeutically beneficial responses, usually with minimal toxicity. This update describes a new procedure for forming multivalent and/or multispecific proteins, known as the dock-and-lock (DNL) technique. Developed as a procedure for preparing bispecific antibodies capable of binding divalently to a tumor antigen and monovalently to a radiolabeled hapten-peptide for pretargeted imaging and therapy, this methodology has the flexibility to create a number of other biologic agents of therapeutic interest. A variety of constructs, based on anti-CD20 and CD22 antibodies, have been made, with results showing that multispecific antibodies have very different properties from the respective parental monospecific antibodies. The technique is not restricted to antibody combination, but other biologics, such as interferon-alpha2b, have been prepared. These types of constructs not only allow small biologics to be sustained in the blood longer, but also to be selectively targeted. Thus, DNL technology is a highly flexible platform that can be used to prepare many different types of agents that could further improve cancer detection and therapy.

Nanomolecular HLA-DR10 antibody mimics: A potent system for molecular targeted therapy and imaging

To mimic the molecular specificity and cell selectivity of monoclonal antibody (mAb) binding while decreasing size, nanomolecules (selective high-affinity ligands; SHALs), based on in silico modeling, have been created to bind to human leukocyte antigen-DR (HLA-DR10), a signaling receptor protein upregulated on the malignant B-lymphocytes of non-Hodgkin's lymphoma and chronic lymphocytic leukemia. SHALs were synthesized with a biotin or DOTA chelate (1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid), using a solid-phase lysine-polyethyleneglycol backbone to link sets of ligands shown previously to bind to HLA-DR10. Using cell-binding and death assays and confocal microscopy, SHAL uptake, residualization, and cytocidal activity were evaluated in HLA-DR10 expressing and nonexpressing live, human lymphoma cell lines. All of the SHALs tested were selective for, and accumulated in, expressing cells. Reflecting binding to HLA-DR10 inside the cells, SHALs having the Ct ligand (3-(2-([3-chloro-5-trifluoromethyl)-2-pyridinyl]oxy)-anilino)-3-oxopropanionic acid) residualized in expressing cells greater than 179 times more than accountable by cell-surface membrane HLA-DR10. Confocal microscopy confirmed the intracellular residualization of these SHALs. Importantly, SHALs with a Ct ligand had direct cytocidal activity, similar in potency to that of Lym-1 mAb and rituximab, selectively for HLA-DR10 expressing lymphoma cells and xenografts. The results show that SHALs containing the Ct ligand residualize intracellularly and have cytocidal effects mediated by HLA-DR10. These SHALs have extraordinary potential as novel molecules for the selective targeting of lymphoma and leukemia for molecular therapy and imaging. Further, these SHALs can be used to transport and residualize cytotoxic agents near critical sites inside these malignant cells.

Dose intensified molecular targeted radiotherapy for cancer-lymphoma as a paradigm

Although most patients with locoregional cancer are cured by surgery, radiotherapy, chemotherapy, and combinations thereof, those with distant metastases are not despite systemic chemotherapy. These patients respond to local radiotherapy but generally need systemic therapy. Non-Hodgkin's lymphoma (NHL) provides a paradigm for the role of molecular targeted radiotherapy (MTRT) because these patients have multifocal disease in most cases. Although patients with NHL achieve remissions after multiple cycles of chemotherapy, less than one half of those with aggressive NHL are cured and almost none of those with low grade NHL. Furthermore, NHL, like other cancers, becomes chemoresistant, yet remains responsive to radiotherapy. MTRT, radiation targeted by molecules, is a good strategy for the treatment of multifocal and radiosensitive cancers. Radioimmunotherapy (RIT) is an MTRT approach using MAbs, or parts thereof, to target the radionuclide that delivers radiation. Two anti-CD20 monoclonal antibodies (MAbs), one labeled with (111)In for imaging or (90)Y for therapy and a second labeled with (131)I for imaging and therapy, have proven effective and safe for MTRT for NHL patients. The importance of the radiation is demonstrated in the data from the randomized pivotal trial of (90)Y-ibritumomab; response rates were distinctly better in the (90)Y-ibritumomab arm than in the rituximab arm. Furthermore, the efficacy of (131)I-tositumomab was greater than that of the same MAb alone in another pivotal trial. Although hematologic toxicity is dose limiting for MTRT, febrile neutropenia is uncommon. MTRT is also not associated with mucositis, hair loss, or persistent nausea or vomiting, unlike chemotherapy. Randomized trials of MTRT in different strategies have not been conducted, but there is evidence of better outcomes, particularly for strategies that provide dose intensification, such as pretargeted MTRT, multiple dosing ("fractionation"), and MTRT with stem cell transplantation (SCT). Pretargeted RIT separates delivery of the targeting molecule from radionuclide delivery, provides dose escalation, and is more effective than direct one-step RIT, although more complicated to implement. Improved drugs and strategies for MTRT have documented potential for better patient outcomes. Smaller radionuclide carriers, such as those used for pretargeted MTRT, should be incorporated into the management of patients with NHL and other cancers soon after the patients have proven incurable. Expected improvements using better drugs, strategies, and combinations with other drugs seem likely to make MTRT integral in the management of many patients with cancer and likely to lead to cures of NHL.

A selective high affinity ligand (SHAL) designed to bind to an over-expressed human antigen on non-Hodgkin's lymphoma also binds to canine B-cell lymphomas

Therapies using antibodies directed against cell surface proteins have improved survival for human patients with non-Hodgkin's lymphoma (NHL). It is possible that similar immuno-therapeutic approaches may also benefit canine NHL patients. Unfortunately, variability between human and canine epitopes often limits the usefulness of such therapies in pet dogs. The Lym-1 antibody recognizes a unique epitope on HLA-DR10 that is expressed on the majority of human B-cell malignancies. The Lym-1 antibody has now been observed to bind to dog lymphocytes and B-cell NHL. Sequence comparisons and computer modeling of a human and three canine DRB1 proteins identified several orthologs of human HLA-DR10 expressed by dog lymphocytes. Immuno-staining confirmed the presence of proteins containing the Lym-1 epitope on dog lymphocytes and B-cell NHL. In addition, a selective high affinity ligand (SHAL) SH-7139 designed to bind within the Lym-1 epitope of HLA-DR10 was also observed to bind to canine B-cell NHL tissue. This SHAL, which is selectively cytotoxic to cells expressing HLA-DR10 and has been shown to cure mice bearing human B-cell lymphoma xenografts, may prove useful in treating B-cell malignancies in pet dogs.

Construction and selection of human Fab antibody phage display library of liver cancer

The aim of this study was to construct the fully humanized anti-hepatoma Fab fragment phage libraries and select antibodies against hepatoma specifically. PBMCs of liver cancer patients were immunized in vitro with HpeG(2) cells and were then transformed by Epstein-Barr virus (EBV). After total RNA was extracted, the heavy chain Fd and kappa/lambda light chain were amplified by RT-PCR and cloned into the vector pComb3 to construct the libraries of Fab fragments. The libraries were then panned by HpeG(2) cells. By means of ELISA and immunochemistry, the Fab phage antibodies binding with hepatoma were selected and identified. The Fd and light chain PCR products were subsequently inserted into pComb3, and the volume of Fab libraries reached 1.7 x 10(7). The libraries were enriched about 138-fold by three cycles of panning. 540 phage clones were picked randomly. Using cell ELISA and immunohistochemistry with cultured cells, one clone Fab phage antibody, which had binding activity with hepatoma, was picked out. Fully humanized anti-hepatoma Fab antibody phage display libraries were constructed. One phage clone was selected and confirmed to specifically bind to hepatoma cells. The selected Fab antibody may be further developed and applied to clinical diagnosis and therapy.

Hexa-arginine enhanced uptake and residualization of selective high affinity ligands by Raji lymphoma cells

Background

A variety of arginine-rich peptide sequences similar to those found in viral proteins have been conjugated to other molecules to facilitate their transport into the cytoplasm and nucleus of targeted cells. The selective high affinity ligand (SHAL) (DvLPBaPPP)₂LLDo, which was developed to bind only to cells expressing HLA-DR10, has been conjugated to one of these peptide transduction domains, hexa-arginine, to assess the impact of the peptide on SHAL uptake and internalization by Raji cells, a B-cell lymphoma.

Results

An analog of the SHAL (DvLPBaPPP)₂LLDo containing a hexa-arginine peptide was created by adding six D-arginine residues sequentially to a lysine inserted in the SHAL's linker. SHAL binding, internalization and residualization by Raji cells expressing HLA-DR10 were examined using whole cell binding assays and confocal microscopy. Raji cells were observed to bind two fold more ¹¹¹In-labeled hexa-arginine SHAL analog than Raji cells treated with the parent SHAL. Three fold more hexa-arginine SHAL remained associated with the Raji cells after washing, suggesting that the peptide also enhanced residualization of the ¹¹¹In transported into cells. Confocal microscopy showed both SHALs localized in the cytoplasm of Raji cells, whereas a fraction of the hexa-arginine SHAL localized in the nucleus.

Conclusion

The incorporation of a hexa-D-arginine peptide into the linker of the SHAL (DvLPBaPPP)₂LLDo enhanced both the uptake and residualization of the SHAL analog by Raji cells. In contrast to the abundant cell surface binding observed with Lym-1 antibody, the majority of (DvLPBaPPP)₂LArg6AcLLDo and the parent SHAL were internalized. Some of the internalized hexa-arginine SHAL analog was also associated with the nucleus. These results demonstrate that several important SHAL properties, including uptake, internalization, retention and possibly intracellular distribution, can be enhanced or modified by conjugating the SHALs to a short polypeptide.

What can be expected from nuclear medicine tomorrow?

Imaging can take advantage of developments in "omics" approaches and go from routine individual biomarkers to multiple-scale biomarker profiles. Imaging structural, functional, metabolic, cellular, and molecular changes will be made possible by multimodality hybrid techniques, such as positron emission tomography-magnetic resonance imaging. Imaging should predict treatment response, look at stratification for specific treatment modalities, and look at the "omic" characterization of an individual patient or a specific tumor. This should lead to the development of "personalized" medicine. In cancer radiotherapy, patient responses should be accurately predicted. In specific cases, proton and hadrontherapy will be further enhanced by the irradiation dose delivered to the tumors. For disseminated or metastatic disease, targeted radionuclide therapy is an effective addition to the arsenal against cancer. The clinical efficacy of radiolabeled antibodies has been clearly demonstrated in lymphoma as well as that of radiolabeled peptides derived from somatostatin in the treatment of neuroendocrine tumors. Preliminary studies now show interesting results in solid tumors, too. Even if the number of objective clinical responses based on tumor shrinkage is small, targeted radionuclide therapy increases progression-free survival or overall survival in some specific cases where tumor burden is small. Avenues for further improvement are multiple and include combination with other therapeutic modalities, development of new approaches (e.g., small molecules, pretargeting, and antibody alternatives). Using alpha-emitting radionuclides is another possibility for specific diseases, such as leukemias, multiple myeloma, or brain tumor remnants.

Systemic radiotherapy can cure lymphoma: a paradigm for other malignancies?

The cytocidal potency of a molecule can be augmented by conjugating a radionuclide for molecular targeted radionuclide therapy (MTRT) for cancer. Radioimmunotherapy (RIT) should be incorporated into the management of patients with B-cell non-Hodgkin's lymphoma (NHL) soon after the patients have proven incurable. Better drugs, strategies, and combinations with other drugs seem certain to make RIT integral to the management of patients with NHL and likely to lead to a cure of the currently incurable NHL. These improved drugs, strategies, and combinations thereof also offer opportunities for RIT to become part of the management of solid malignancies, including epithelial cancers. Smaller radionuclide carriers, such as those used for pretargeted strategies, provide dose intensification. The potential of pretargeted RIT to improve patient outcomes is striking.