SARS coronavirus continues to cause sporadic cases of severe acute respiratory syndrome (SARS) in China. No active or passive immunoprophylaxis for disease induced by SARS coronavirus is available. We investigated prophylaxis of SARS coronavirus infection with a neutralising human monoclonal antibody in ferrets, which can be readily infected with the virus. Prophylactic administration of the monoclonal antibody at 10 mg/kg reduced replication of SARS coronavirus in the lungs of infected ferrets by 3·3 logs (95% Cl 2·6–4·0 logs; p<0·001), completely prevented the development of SARS coronavirus-induced macroscopic lung pathology (p=0·013), and abolished shedding of virus in pharyngeal secretions. The data generated in this animal model show that administration of a human monoclonal antibody might offer a feasible and effective prophylaxis for the control of human SARS coronavirus infection.
<div>Abstract<p>Checkpoint inhibitors (CPI) have revolutionized the treatment paradigm for advanced solid tumors; however, there remains an opportunity to improve response rates and outcomes. In preclinical models, 4-1BB costimulation synergizes with CPIs targeting the programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) axis by activating cytotoxic T-cell–mediated antitumor immunity. DuoBody-PD-L1×4-1BB (GEN1046) is an investigational, first-in-class bispecific immunotherapy agent designed to act on both pathways by combining simultaneous and complementary PD-L1 blockade and conditional 4-1BB stimulation in one molecule. GEN1046 induced T-cell proliferation, cytokine production, and antigen-specific T-cell–mediated cytotoxicity superior to clinically approved PD-(L)1 antibodies in human T-cell cultures and exerted potent antitumor activity in transplantable mouse tumor models. In dose escalation of the ongoing first-in-human study in heavily pretreated patients with advanced refractory solid tumors (NCT03917381), GEN1046 demonstrated pharmacodynamic immune effects in peripheral blood consistent with its mechanism of action, manageable safety, and early clinical activity [disease control rate: 65.6% (40/61)], including patients resistant to prior PD-(L)1 immunotherapy.</p>Significance:<p>DuoBody-PD-L1×4-1BB (GEN1046) is a first-in-class bispecific immunotherapy with a manageable safety profile and encouraging preclinical and early clinical activity. With its ability to confer clinical benefit in tumors typically less sensitive to CPIs, GEN1046 may fill a clinical gap in CPI-relapsed or refractory disease or as a combination therapy with CPIs.</p><p><i>See related commentary by Li et al., p. 1184.</i></p><p><i>This article is highlighted in the In This Issue feature, p. 1171</i></p></div>
Abstract Axl is a receptor tyrosine kinase of the TAM family, which is structurally characterized by the presence of two extracellular immunoglobulin-like domains and two fibronectin type III domains, a single-pass transmembrane region and an intracellular tyrosine kinase domain. Axl is aberrantly expressed and activated in both solid and hematological malignancies and has been associated with poor clinical prognosis in a number of cancers, including non-small cell lung cancer, breast cancer, pancreatic cancer and acute myeloid lymphoma. Functionally, Axl has been implicated in multiple pathological processes, such as tumor cell motility, adherence and migration, epithelial-to-mesenchymal transition, metastasis, angiogenesis and resistance to tyrosine kinase inhibitors. With the aim to target Axl expressing cancers, a panel of Axl-specific antibody-drug conjugates (ADC) was generated. First, high affinity human Axl antibodies were generated in HuMAb mice. Binding studies using Axl mutants, in which specific human Axl domains had been replaced with their murine analogs, demonstrated that the Axl antibody panel consisted of antibodies against different Axl extracellular domains. Second, the Axl antibodies were conjugated with the microtubule disrupting agent monomethyl auristatin E (MMAE) using the protease cleavable valine citrulline linker. Axl ADCs showed cytotoxic activity in vitro, which was dependent on target expression and on conjugation with cytotoxic payload. The anti-tumor activity of Axl ADCs was confirmed in vivo. Axl ADCs induced tumor regression in cell line derived xenograft models for lung cancer and epidermoid carcinoma. Anti-tumor activity was especially efficient in the lung cancer xenograft model, in which inhibition of tumor growth was observed upon treatment with a single dose of 0.5 mg/kg Axl ADC. In the same model, 1 mg/kg Axl ADC was sufficient to induce complete tumor regression. Importantly, Axl ADCs also showed efficient anti-tumor activity in patient-derived xenograft (PDX) models that showed heterogeneous target expression. In summary, Axl is a novel target for antibody-mediated delivery of cytotoxic agents into tumor cells. The promising results obtained in preclinical tumor models support further development of Axl-specific ADCs. Citation Format: Esther C.W. Breij, Sandra Verploegen, Andreas Lingnau, Edward N. van den Brink, Maarten Janmaat, Mischa Houtkamp, Wim K. Bleeker, David Satijn, Paul W.H.I. Parren. Novel antibody-drug conjugates targeting Axl show anti-tumor activity in solid cancer xenograft models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 634. doi:10.1158/1538-7445.AM2015-634
Supplementary Figure from Preclinical Characterization and Phase I Trial Results of a Bispecific Antibody Targeting PD-L1 and 4-1BB (GEN1046) in Patients with Advanced Refractory Solid Tumors
Human monoclonal antibodies (MAbs) were selected from semisynthetic antibody phage display libraries by using whole irradiated severe acute respiratory syndrome (SARS) coronavirus (CoV) virions as target. We identified eight human MAbs binding to virus and infected cells, six of which could be mapped to two SARS-CoV structural proteins: the nucleocapsid (N) and spike (S) proteins. Two MAbs reacted with N protein. One of the N protein MAbs recognized a linear epitope conserved between all published human and animal SARS-CoV isolates, and the other bound to a nonlinear N epitope. These two N MAbs did not compete for binding to SARS-CoV. Four MAbs reacted with the S glycoprotein, and three of these MAbs neutralized SARS-CoV in vitro. All three neutralizing anti-S MAbs bound a recombinant S1 fragment comprising residues 318 to 510, a region previously identified as the SARS-CoV S receptor binding domain; the nonneutralizing MAb did not. Two strongly neutralizing anti-S1 MAbs blocked the binding of a recombinant S fragment (residues 1 to 565) to SARS-CoV-susceptible Vero cells completely, whereas a poorly neutralizing S1 MAb blocked binding only partially. The MAb ability to block S1-receptor binding and the level of neutralization of the two strongly neutralizing S1 MAbs correlated with the binding affinity to the S1 domain. Finally, epitope mapping, using recombinant S fragments (residues 318 to 510) containing naturally occurring mutations, revealed the importance of residue N479 for the binding of the most potent neutralizing MAb, CR3014. The complete set of SARS-CoV MAbs described here may be useful for diagnosis, chemoprophylaxis, and therapy of SARS-CoV infection and disease.
Hemophilia A is a X-linked bleeding disorder that is caused by the functional absence of blood coagulation factor VIII. The bleeding tendency in hemophilia A patients can be corrected by the administration of plasma-derived or recombinant factor VIII concentrates. A serious complication in hemophilia care is the development of factor VIII neutralizing antibodies (inhibitors) that arise as a consequence of factor VIII replacement therapy. The majority of factor VIII inhibitors are directed toward epitopes located within the A2, A3, and C2 domains of factor VIII. In this article, we summarize current knowledge on the epitope specificity of factor VIII inhibitors. In addition, we will discuss recent information on the molecular characteristics of human anti-factor VIII antibodies generated by phage display technology.
