Houston, Texas, USA : Scientists at The Wistar Institute and collaborators have successfully engineered novel DNA-encoded monoclonal antibodies (DMAbs) targeting Zaire Ebolavirus that were effective in preclinical models. Study results, published online in Cell Reports, showed that DMAbs were expressed over a wide window of time and offered complete and long-term protection against lethal virus challenges. DMAbs may also provide a novel powerful platform for rapid screening of monoclonal antibodies enhancing preclinical development.
Ebola virus infection causes a devastating disease, known as Ebola virus disease, for which no licensed vaccine or treatment are available. The 2014-2016 Zaire Ebola virus epidemic in West Africa was the most severe reported to date, with more than 28,600 cases and 11,325 deaths according to the Center for Disease Control. A new outbreak is ongoing in the Democratic Republic of Congo, with a death toll of more than 200 people since August. One of the experimental avenues scientists are pursuing is evaluating the safety and efficacy of monoclonal antibodies isolated from survivors as promising candidates for further development as therapeutics against Ebola virus infection. However, this approach requires high doses and repeated administration of recombinant monoclonal antibodies that are complex and expensive to manufacture, so meeting the global demand while keeping the cost affordable is challenging.
“Our studies show deployment of a novel platform that rapidly combines aspects of monoclonal antibody discovery and development technology with the revolutionary properties of synthetic DNA technology,” said lead researcher David B. Weiner, Ph.D., executive vice president and director of Wistar’s Vaccine & Immunotherapy Center, and W.W. Smith Charitable Trust Professor in Cancer Research.
The team designed and enhanced optimized DMAbs that, when injected locally, provide the genetic blueprint for the body to make functional and protective Ebola virus-specific antibodies, circumventing multiple steps in the antibody development and manufacturing process. Dozens of DMAbs were tested in mice and the best-performing ones were selected for further studies. These proved to be highly effective for providing complete protection from disease in challenge studies.
“Due to intrinsic biochemical properties, some monoclonal antibodies might be difficult and slow to develop or even impossible to manufacture, falling out of the development process and causing loss of potentially effective molecules,” added Weiner. “The DMAb platform allows us to collect protective antibodies from protected persons and engineer and compare them rapidly and then deliver them in vivo to protect against infectious challenge. Such an approach could be important during an outbreak, when we need to design, evaluate and deliver life-saving therapeutics in a time-sensitive manner.”
“We started with antibodies isolated from survivors and compared the activity of anti-Ebola virus DMAbs and recombinant monoclonal antibodies over time,” said Ami Patel, Ph.D., first author on the study and associate staff scientist in the Wistar Vaccine and Immunotherapy Center. “We showed that in vivo expression of DMAbs supports extended protection over traditional antibody approaches.”
The researchers also looked at how DMAbs physically interact with their Ebola virus targets, called epitopes, and confirmed that DMAbs bind to identical epitopes as the corresponding recombinant monoclonal antibodies made in traditional bioprocess facilities.
The Weiner Laboratory is also developing an anti-Ebola virus DNA vaccine. Preclinical results from this efforts were published recently in the Journal of Infectious Diseases.
Citation: Ami Patel et al, In Vivo Delivery of Synthetic Human DNA-Encoded Monoclonal Antibodies Protect against Ebolavirus Infection in a Mouse Model, Cell Reports. DOI: 10.1016/j.celrep.2018.10.062
Image : Ebola virus particles (red) on a larger cell.
Image credit : NIAID
Wistar scientists also reported that synthetic DNA-encoded checkpoint inhibitor antibodies advance cancer immunotherapy
Synthetic DNA-encoded checkpoint inhibitor antibodies advance cancer immunotherapy
Wistar scientists and collaborators demonstrate for the first time that through engineering constructs, they can express DNA-encoded monoclonal antibodies (DMAbs) targeting CTLA-4, an important cancer checkpoint molecule that blocks anti-cancer immunity. Using a synthetic DNA platform, they built versions of the anti-CTLA-4 molecule and were able to then deliver the DMAbs and have them generate fully functional anti-CTLA4 molecules in vivo. This proof-of-principle study opens new avenues for the design and delivery of therapeutic checkpoint inhibitors and suggests potentially novel applications of this technology in cancer treatment. Study results were published online in Cancer Research.
Treatment of cancer with checkpoint inhibitors has recently revolutionized cancer immunotherapy. Since the discovery of immune checkpoints, which was recognized as a groundbreaking development for cancer therapy and awarded the Nobel Prize in physiology or medicine this week, checkpoint inhibitors are becoming standard of care for various malignancies, showing unprecedented impact for patients.
Despite the tremendous advancement in cancer therapy brought by monoclonal antibodies targeting checkpoint molecules, manufacturing complexity and repeated dosing may limit a broader use of this technology.
“Our work provides the first demonstration that we can use synthetic DNA technology to produce checkpoint inhibitor molecules in vivo to impact tumor growth in a preclinical setting,” said lead researcher David B. Weiner, Ph.D., executive vice president and director of the Vaccine & Immunotherapy Center at The Wistar Institute, and W.W. Smith Charitable Trust Professor in Cancer Research. “We showed that DMAbs may represent a valuable addition to the cancer immunotherapy toolbox: In our preclinical studies, DMAbs achieved antitumor activity comparable to that of traditional monoclonal antibodies, while being delivered through a simpler formulation that may provide a bridge to expand target populations for checkpoint inhibitors.”
The team developed a synthetic, sequence-optimized DNA plasmid designed to encode anti-mouse CTLA-4 monoclonal antibodies. When injected in the muscle of mice with the aid of an electroporation device to enhance uptake, the anti-CTLA-4 DMAbs resulted in significant and prolonged antibody expression with even a single dose. Importantly, this approach stimulated robust CD8+ T-cell infiltration, achieving tumor clearance across multiple mouse tumor models. The researchers then went on to develop human checkpoint inhibitor molecules and demonstrated their production in mice and their ability to stimulate human T-cell responses associated with antitumor activity.
“Our results open the door for further applications of DMAbs in cancer immunotherapy,” said Elizabeth K. Duperret, Ph.D., postdoctoral fellow in the Weiner Lab and first author on the study. “This platform is rapid and flexible, allowing for further optimization of antibody sequences, including development of novel therapeutic approaches for which conventional monoclonal antibodies are not suitable.”
Enhancing immune checkpoint inhibitor therapy using treatment combination
A combination of a novel inhibitor of the protein CK2 (Casein kinase 2) and an immune checkpoint inhibitor has dramatically greater antitumor activity than either inhibitor alone, according to research from The Wistar Institute that was published online in Cancer Research.
Immune checkpoint inhibitors have been approved to treat several types of cancer, including some types of lung cancer and colon cancer, but not all patients who receive these immunotherapeutics gain benefit from them. A better understanding of the molecular reasons why some patients do not respond to immune checkpoint inhibitors could identify new therapeutic targets for combination treatments that may improve clinical outcomes.
“A population of immune cells called myeloid-derived suppressor cells (MDSC) has been implicated in tumor resistance to various types of cancer treatment, including immune checkpoint inhibitors,” said lead researcher Dmitry I. Gabrilovich, M.D., Ph.D., Christopher M. Davis Professor and program leader of the Immunology, Microenvironment & Metastasis Program at Wistar. “We have previously shown that accumulation of the most abundant type of MDSC, polymorphonuclear MDSC (PMN-MDSC), is caused by downregulation of Notch signaling, in part as a result of CK2 activity.”
Based on these previous results, Gabrilovich and collaborators set out to investigate whether combining inhibitors of CK2 with immune checkpoint inhibitors could improve immune responses in mouse models of cancer and to determine what mechanisms of action caused the results they obtained.
“Our new data suggest that using a CK2 inhibitor to manipulate the tumor microenvironment may sensitize patients to the effect of an immune checkpoint inhibitor and thereby improve clinical outcomes, although this needs to be tested in clinical trials,” said Ayumi Hashimoto, a postdoctoral fellow in the Gabrilovich Lab and first author on the paper.
The researchers found that a combination of the CK2 inhibitor BMS-595 and the immune checkpoint inhibitor anti-CTLA-4-mIgG2a had antitumor activity in three different mouse models of cancer: a lung cancer, a colon cancer, and a lymphoma model. More than 60 percent of mice who received the combination treatment completely eliminated the tumor while none of the mice that received either single agent alone completely eliminated the tumor.
The mechanism of the effect of BMS-595 was analyzed, and in-depth studies showed that two of the main types of immune cells affected by the CK2 inhibitor in tumor-bearing mice were PMN-MDSCs and another type of myeloid cell called tumor-associated macrophages (TAMs). The frequency of PMN-MDSCs was not significantly altered in tumors, but it was substantially decreased in the spleen, an organ that is a part of the immune system. TAMs were decreased in the tumor.
“Our study shows that CK2 inhibition blocks the differentiation of PMN-MDSCs and TAMs, meaning that it blocked the generation of these cells from their precursors. This led to a decrease in immunosuppressive PMN-MDSCs and tumor-promoting TAMs and thus to a substantial augmentation of the antitumor activity of immune checkpoint blockade,” added Gabrilovich.
Citation for third study : Ayumi Hashimoto et al, Inhibition of casein kinase 2 disrupts differentiation of myeloid cells in cancer and enhances the efficacy of immunotherapy in mice, Cancer Research. DOI: 10.1158/0008-5472.CAN-18-1229