[Show abstract][Hide abstract] ABSTRACT: The adoptive transfer of autologous T cells engineered to express a chimeric antigen receptor (CAR) has emerged as a promising cancer therapy. Despite impressive clinical efficacy, the general application of current CAR-T-cell therapy is limited by serious treatment-related toxicities. One approach to improve the safety of CAR-T cells involves making their activation and proliferation dependent upon adaptor molecules that mediate formation of the immunological synapse between the target cancer cell and T-cell. Here, we describe the design and synthesis of structurally defined semisynthetic adaptors we refer to as "switch" molecules, in which anti-CD19 and anti-CD22 antibody fragments are site-specifically modified with FITC using genetically encoded noncanonical amino acids. This approach allows the precise control over the geometry and stoichiometry of complex formation between CD19- or CD22-expressing cancer cells and a "universal" anti-FITC-directed CAR-T cell. Optimization of this CAR-switch combination results in potent, dose-dependent in vivo antitumor activity in xenograft models. The advantage of being able to titrate CAR-T-cell in vivo activity was further evidenced by reduced in vivo toxicity and the elimination of persistent B-cell aplasia in immune-competent mice. The ability to control CAR-T cell and cancer cell interactions using intermediate switch molecules may expand the scope of engineered T-cell therapy to solid tumors, as well as indications beyond cancer therapy.
Full-text · Article · Jan 2016 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Chimeric antigen receptor T (CAR-T) cell therapy has produced impressive results in clinical trials for B-cell malignancies. However, safety concerns related to the inability to control CAR-T cells once infused into the patient remain a significant challenge. Here we report the engineering of recombinant antibody-based bifunctional switches that consist of a tumor antigen-specific Fab molecule engrafted with a peptide neo-epitope, which is bound exclusively by a peptide-specific switchable CAR-T cell (sCAR-T). The switch redirects the activity of the bio-orthogonal sCAR-T cells through the selective formation of immunological synapses, in which the sCAR-T cell, switch, and target cell interact in a structurally defined and temporally controlled manner. Optimized switches specific for CD19 controlled the activity, tissue-homing, cytokine release, and phenotype of sCAR-T cells in a dose-titratable manner in a Nalm-6 xenograft rodent model of B-cell leukemia. The sCAR-T-cell dosing regimen could be tuned to provide efficacy comparable to the corresponding conventional CART-19, but with lower cytokine levels, thereby offering a method of mitigating cytokine release syndrome in clinical translation. Furthermore, we demonstrate that this methodology is readily adaptable to targeting CD20 on cancer cells using the same sCAR-T cell, suggesting that this approach may be broadly applicable to heterogeneous and resistant tumor populations, as well as other liquid and solid tumor antigens.
Full-text · Article · Jan 2016 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: As part of an effort to examine the utility of antibody-drug conjugates (ADCs) beyond oncology indications, a novel pyrophosphate-ester linker was discovered to enable the targeted delivery of glucocorticoids. As small molecules, these highly-soluble phosphate-ester drug-linkers were found to have ideal orthogonal properties: robust plasma stability coupled with rapid release of payload in a lysosomal environment. Building upon these findings, site-specific ADCs were made between this drug-linker combination and an antibody against human CD70, a receptor specifically expressed in immune cells but also found aberrantly expressed in multiple human carcinomas. Full characterization of these ADCs enabled procession to in vitro proof of concept, wherein ADCs 1-22 and 1-37 were demonstrated to afford potent, targeted delivery of glucocorticoids to a representative cell line as measured by changes in glucocorticoid receptor (GR) mediated gene mRNA levels. These activities were found to be antibody, linker and payload dependent. Preliminary mechanistic studies support the notion that lysosomal trafficking and enzymatic linker-cleavage is required for activity, and that the utility for the pyrophosphate linker may be general for internalizing ADCs as well as other targeted delivery platforms.
No preview · Article · Jan 2016 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: Incretin-based peptides are effective therapeutics for treating type 2 diabetes mellitus (T2DM). Oxyntomodulin (OXM), a dual agonist of GLP-1R and GCGR, has shown superior weight loss and glucose lowering effects, compared to single GLP-1R agonists. To overcome the short half-life and rapid renal clearance of OXM, which limit its therapeutic potential, both lipid and PEG modified OXM analogs have been reported. However, these approaches often result in reduced potency or PEG-associated toxicity. Herein, we report a new class of cross-linked OXM analogs that show increased plasma stability and higher potency in activating both GLP-1R and GCGR. Moreover, the extended in vivo half-life results in superior antihyperglycemic activity in mice compared to the wild-type OXM.
No preview · Article · Jan 2016 · ACS Chemical Biology
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in children. We have generated an epitope-specific RSV vaccine by grafting a neutralizing epitope (F-epitope) in its native conformation into an immunoglobulin scaffold. The resulting antibody fusion exhibited strong binding affinity to Motavizumab, an RSV neutralizing antibody, and effectively induced potent neutralizing antibodies in mice. This work illustrates the potential of the immunoglobulin molecule as a scaffold to present conformationally constrained B-cell epitopes.
No preview · Article · Oct 2015 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: NRF2 serves as the master regulator of oxidative stress resistance in mammalian cells. Although NRF2 activation decreases tumorigenic events in normal cells, accumulating evidence suggests that cancers have broadly selected for NRF2-activating mutations to promote anabolic growth and chemoresistance. Small molecules which inhibit NRF2 activity may therefore offer promise as an alternative anticancer treatment in NRF2 dependent cancers. We have used a high throughput screen to identify small molecules which decrease NRF2 transcriptional activity at antioxidant response element sites. One such molecule, termed AEM1, is capable of broadly decreasing the expression of NRF2 controlled genes, sensitizing A549 cells to various chemotherapeutic agents, and inhibiting the growth of A549 cells in vitro and in vivo. Profiling of multiple cell lines for their responsiveness to AEM1 revealed that AEM1's activities are restricted to cell lines harboring mutations which render NRF2 constitutively active.
No preview · Article · Aug 2015 · ACS Chemical Biology
[Show abstract][Hide abstract] ABSTRACT: With few exceptions, all living organisms encode the same 20 canonical amino acids; however, it remains an open question whether organisms with additional amino acids beyond the common 20 might have an evolutionary advantage. Here, we begin to test that notion by making a large library of mutant enzymes in which 10 structurally distinct noncanonical amino acids were substituted at single sites randomly throughout TEM-1 β-lactamase. A screen for growth on the β-lactam antibiotic cephalexin afforded a unique p-acrylamido-phenylalanine (AcrF) mutation at Val-216 that leads to an increase in catalytic efficiency by increasing kcat, but not significantly affecting KM. To understand the structural basis for this enhanced activity, we solved the X-ray crystal structures of the ligand-free mutant enzyme and of the deacylation-defective wild-type and mutant cephalexin acyl-enzyme intermediates. These structures show that the Val-216-AcrF mutation leads to conformational changes in key active site residues-both in the free enzyme and upon formation of the acyl-enzyme intermediate-that lower the free energy of activation of the substrate transacylation reaction. The functional changes induced by this mutation could not be reproduced by substitution of any of the 20 canonical amino acids for Val-216, indicating that an expanded genetic code may offer novel solutions to proteins as they evolve new activities.
No preview · Article · Jun 2015 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Liver X receptor (LXR) agonists have been explored as potential treatments for atherosclerosis and other diseases based on their ability to induce reverse cholesterol transport and suppress inflammation. However, this therapeutic potential has been hindered by on-target adverse effects in the liver mediated by excessive lipogenesis. Herein, we report a novel site-specific antibody-drug conjugate (ADC) that selectively delivers a LXR agonist to monocytes/macrophages while sparing hepatocytes. The unnatural amino acid para-acetylphenylalanine (pAcF) was site-specifically incorporated into anti-CD11a IgG, which binds the α-chain component of the lymphocyte function-associated antigen 1 (LFA-1) expressed on nearly all monocytes and macrophages. An aminooxy-modified LXR agonist was conjugated to anti-CD11a IgG through a stable, cathepsin B cleavable oxime linkage to afford a chemically-defined ADC. The anti-CD11a IgG-LXR agonist ADC induced LXR activation specifically in human THP-1 monocyte/macrophage cells in vitro (EC50 ~ 27 nM), but had no effect in hepatocytes, indicating that payload delivery is CD11a-mediated. Moreover, the ADC exhibited higher fold activation compared to a conventional synthetic LXR agonist T0901317 (Tularik) (3 fold). This novel ADC represents a fundamentally different strategy that uses tissue targeting to overcome the limitations of LXR agonists for potential use in treating atherosclerosis.
Full-text · Article · May 2015 · Bioconjugate Chemistry
[Show abstract][Hide abstract] ABSTRACT: Here we report the evolution of an orthogonal amber suppressor pyrrolysyl-tRNA synthetase (PylRS)/tRNACUAPyl pair that genetically encodes the post-translationally modified amino acid, ε-N-2-hydroxyisobutyryl-lysine (HibK), in bacteria and mammalian cells. HibK is a new type of histone mark that is widely distributed in histone proteins. The ability to site-specifically incorporate HibK into proteins provides a useful tool to probe the biological function of this newly identified post-translational modification.
No preview · Article · Apr 2015 · ACS Chemical Biology
[Show abstract][Hide abstract] ABSTRACT: Infections caused by antibiotic-resistant bacteria are a rising public health threat and make the identification of new antibiotics a priority. From a cell-based screen for bactericidal compounds against Mycobacterium tuberculosis under nutrient-deprivation conditions we identified auranofin, an orally bioavailable FDA-approved antirheumatic drug, as having potent bactericidal activities against both replicating and nonreplicating M. tuberculosis. We also found that auranofin is active against other Gram-positive bacteria, including Bacillus subtilis and Enterococcus faecalis, and drug-sensitive and drug-resistant strains of Enterococcus faecium and Staphylococcus aureus. Our biochemical studies showed that auranofin inhibits the bacterial thioredoxin reductase, a protein essential in many Gram-positive bacteria for maintaining the thiol-redox balance and protecting against reactive oxidative species. Auranofin decreases the reducing capacity of target bacteria, thereby sensitizing them to oxidative stress. Finally, auranofin was efficacious in a murine model of methicillin-resistant S. aureus infection. These results suggest that the thioredoxin-mediated redox cascade of Gram-positive pathogens is a valid target for the development of antibacterial drugs, and that the existing clinical agent auranofin may be repurposed to aid in the treatment of several important antibiotic-resistant pathogens.
Full-text · Article · Apr 2015 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The bovine antibody (BLV1H12) which has an ultralong CDR3H provides a novel scaffold for engineering new func-tions into the antibody variable region. By modifying the β-strand "stalk" of BLV1H12 with sequences derived from natu-ral or synthetic protease inhibitors, we have generated anti-bodies that inhibit bovine trypsin and human neutrophil elastase (HNE) with low nanomolar affinities. We were also able to generate a humanized variant using a human immu-noglobulin scaffold that shares a high degree of homology with BLV1H12. Further optimization yielded a highly selec-tive humanized anti-HNE antibody with sub-nanomolar affinity. This work demonstrates a novel strategy for gener-ating antibodies with potent and selective inhibitory activi-ties against extracellular proteases involved in human dis-ease.
No preview · Article · Mar 2015 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: We have developed a novel antibody drug-conjugate (ADC) which can selectively deliver the Lck inhibitor dasatinib to human T lym-phocytes. This ADC is based on a humanized antibody which se-lectively binds with high affinity to CXCR4, an antigen that is se-lectively expressed on hematopoietic cells. The resulting dasatinib-antibody conjugate suppresses T-cell-receptor (TCR)-mediated T cell activation and cytokine expression with low nM EC50 and has minimal effects on cell viability. This ADC may lead to a new class of selective immunosuppressive drugs with improved safety, and extends the antibody-drug conjugate strategy to the targeted deliv-ery of kinase inhibitors for indications beyond oncology.
Full-text · Article · Feb 2015 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: Chimeric antigen receptor (CAR)-engineered T cells (CAR-Ts) provide a potent anti-tumor response and have become a promising treatment option for cancer. However, despite their efficacy, CAR-T cells are associated with significant safety challenges related to the inability to control their activation and expansion, and terminate their response. Herein, we demonstrate that a bifunctional small molecule "switch" consisting of folate conjugated to fluorescein isothiocyanate (folate-FITC) can redirect and regulate FITC-specific CAR-T cell activity towards folate receptor (FR)-overexpressing tumor cells. This system was shown to be highly cytotoxic to FR-positive cells with no activity against FR-negative cells, demonstrating the specificity of redirec-tion by folate-FITC. FITC-CAR-T cell activation and prolifer-ation was strictly dependent on the presence of both folate-FITC and FR-positive cells and was dose titratable with folate-FITC switch. This novel treatment paradigm may ul-timately lead to increased safety for CAR-T cell immunotherpy.
Full-text · Article · Feb 2015 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: On the basis of the 3D structure of a bovine antibody with a well-folded, ultralong complementarity-determining region (CDR), we have developed a versatile approach for generating human or humanized antibody agonists with excellent pharmacological properties. Using human growth hormone (hGH) and human leptin (hLeptin) as model proteins, we have demonstrated that functional human antibody CDR fusions can be efficiently engineered by grafting the native hormones into different CDRs of the humanized antibody Herceptin. The resulting Herceptin CDR fusion proteins were expressed in good yields in mammalian cells and retain comparable in vitro biological activity to the native hormones. Pharmacological studies in rodents indicated a 20- to 100-fold increase in plasma circulating half-life for these antibody agonists and significantly extended in vivo activities in the GH-deficient rat model and leptin-deficient obese mouse model for the hGH and hLeptin antibody fusions, respectively. These results illustrate the utility of antibody CDR fusions as a general and versatile strategy for generating long-acting protein therapeutics.
No preview · Article · Feb 2015 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Bovine antibody BLV1H12 possesses a unique “stalk–knob” architecture in its ultralong heavy chain CDR3, allowing substitutions of the “knob” domain with protein agonists to generate functional antibody chimeras. We have generated a humanized glucagon-like peptide-1 (GLP-1) receptor agonist antibody by first introducing a coiled-coil “stalk” into CDR3H of the antibody herceptin. Exendin-4 (Ex-4), a GLP-1 receptor agonist, was then fused to the engineered stalk with flexible linkers, and a Factor Xa cleavage site was inserted immediately in front of Ex-4 to allow release of the N-terminus of the fused peptide. The resulting clipped herceptin–Ex-4 fusion protein is more potent in vitro in activating GLP-1 receptors than the Ex-4 peptide. The clipped herceptin–Ex-4 has an extended plasma half-life of approximately four days and sustained control of blood glucose levels for more than a week in mice. This work provides a novel approach to the development of human or humanized agonist antibodies as therapeutics.
No preview · Article · Dec 2014 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: The ultralong heavy chain complementarity determining region 3 (CDR3H) of bovine antibody BLV1H12 folds into a novel "stalk-knob" structural motif and has been exploited to generate novel agonist antibodies through replacement of the "knob" domain with cytokines and growth factors. By translating this unique "stalk-knob" architecture to the humanized antibody Herceptin, we have developed a versatile approach to the generation of human antibody agonists. Human erythropoietin (hEPO) or granulocyte colony-stimulating factor (hGCSF) was independently fused into CDR3H, CDR2H, or CDR3L of Herceptin using an engineered "stalk" mo-tif. The fusion proteins express in mammalian cells in good yields and have similar in vitro biological activities compared to hEPO and hGCSF. On the basis of these results we then generated a bi-functional Herceptin-CDR fusion protein in which both hEPO and hGCSF were grafted into the heavy and light chain CDR3 loops, respectively. This bi-functional antibody fusion exhibited potent EPO and GCSF agonist activities. This work demonstrates the versatility of the CDR-fusion strategy for generating functional human antibody chimeras and provides a novel approach to the development of multi-functional antibody-based therapeutics.
No preview · Article · Dec 2014 · Journal of the American Chemical Society