Cancer immunotherapy has already shown significant improvements by combining different antibodies specific for distinct immune checkpoints, such as Ipilimumab and Nivolumab. Here, we tested combinatorial treatments of immunomodulatory antibodies, previously generated in our laboratory, for their effects on hPBMC activation, either upon stimulation with SEB or in co-cultures with tumor cells by cytokine secretion assays. We found that some of them showed additive or synergistic effects, and on the basis of these observations, we constructed, for the first time, four novel bispecific tribodies (TR), made up of a Fab derived from one anti-IC mAb and two scFvs derived from another mAb targeting a different IC. All four TRs cotargeting either programmed cell death protein 1 (PD-1) and Lymphocyte Activating 3 (LAG-3) or programmed death-ligand 1 (PD-L1) and LAG-3 retained binding affinity for their targets and the antagonistic effects of their parental mAbs, but some of them also showed an increased ability to induce lymphocyte activation and increased in vitro cytotoxicity against tumor cells compared to parental antibodies used either alone or in combinatorial treatments. Furthermore, none of the tribodies showed significant increased cytotoxicity on human cardiomyocytes. Considering that the tribody format reduces production costs (as only one construct provides the inhibitory effects of two antibodies), has an intermediate molecular size (100 kDa) which is well suited for both tumor penetration and an acceptable half-life, we think that these novel immunomodulatory TRBs have the potential to become precious tools for therapeutic applications, particularly in monotherapy-resistant cancer patients.

Many advances in antitumor therapies have been achieved with antagonistic antibodies targeting the programmed cell death protein 1 (PD-1) or its ligand (PD-L1); however, many cancer patients still develop resistance to anti–PD-1/PD-L1 treatments often associated with the upregulation of other immune checkpoints such as Lymphocyte Activation Gene-3 (LAG-3). In order to verify whether it is possible to overcome these limits, we analyzed and compared the effects of combinations of the clinically validated anti-LAG-3 mAb (Relatlimab) with anti-PD-1 (Pembrolizumab) or anti-PD-L1 (Atezolizumab) monoclonal antibodies (mAbs) with those of novel bispecific tribodies (TRs), called TR0304 and TR0506, previously generated in our lab by combining the binding moieties of novel human antibodies targeting the same ICs of the mentioned mAbs. In particular, TR0304, made up of a Fab derived from an anti-PD-L1 mAb and two single-chain variable fragments (scFvs) derived from an anti-LAG-3 mAb, was tested in comparison with Relatlimab plus Atezolizumab, and TR0506, made up of an antigen-binding fragment (Fab) derived from the same anti-LAG-3 mAb and two scFvs derived from an anti-PD-1 mAb, was tested in comparison with Relatlimab and Pembrolizumab. We found that the two novel TRs showed similar binding affinity to the targets with respect to validated mAbs, even though they recognized distinct or only partially overlapping epitopes. When tested for their functional properties, they showed an increased ability to induce lymphocyte activation and stronger in vitro cytotoxicity against tumor cells compared to combinatorial treatments of clinically validated mAbs. Considering that tribodies also have other advantages with respect to combinatorial treatments, such as reduced production costs and lower dose requirements, we think that these novel immunomodulatory TRs could be used for therapeutic applications, particularly in monotherapy-resistant cancer patients.

The dramatic experience with SARS-CoV-2 has alerted the scientific community to be ready to face new epidemics/pandemics caused by new variants. Among the therapies against the pandemic SARS-CoV-2 virus, monoclonal Antibodies (mAbs) targeting the Spike glycoprotein have represented good drugs to interfere in the Spike/ Angiotensin Converting Enzyme-2 (ACE-2) interaction, preventing virus cell entry and subsequent infection, especially in patients with a defective immune system. We obtained, by an innovative phage display selection strategy, specific binders recognizing different epitopes of Spike. The novel human antibodies specifically bind to Spike-Receptor Binding Domain (RBD) in a nanomolar range and interfere in the interaction of Spike with the ACE-2 receptor. We report here that one of these mAbs, named D3, shows neutralizing activity for virus infection in cell cultures by different SARS-CoV-2 variants and retains the ability to recognize the Omicron-derived recombinant RBD differently from the antibodies Casirivimab or Imdevimab. Since anti-Spike mAbs, used individually, might be unable to block the virus cell entry especially in the case of resistant variants, we investigated the possibility to combine D3 with the antibody in clinical use Sotrovimab, and we found that they recognize distinct epitopes and show additive inhibitory effects on the interaction of Omicron-RBD with ACE-2 receptor. Thus, we propose to exploit these mAbs in combinatorial treatments to enhance their potential for both diagnostic and therapeutic applications in the current and future pandemic waves of coronavirus.

The recent pandemic years have prompted the scientific community to increasingly search for and adopt new and more efficient therapeutic and diagnostic approaches to deal with a new infection. In addition to the development of vaccines, which has played a leading role in fighting the pandemic, the development of monoclonal antibodies has also represented a valid approach in the prevention and treatment of many cases of CoronaVirus Disease 2019 (COVID-19). Recently, we reported the development of a human antibody, named D3, showing neutralizing activity against different SARS-CoV-2 variants, wild-type, UK, Delta and Gamma variants. Here, we have further characterized with different methods D3’s ability to bind the Omicron-derived recombinant RBD by comparing it with the antibodies Cilgavimab and Tixagevimab, recently approved for prophylactic use of COVID-19. We demonstrate here that D3 binds to a distinct epitope from that recognized by Cilgavimab and shows a different binding kinetic behavior. Furthermore, we report that the ability of D3 to bind the recombinant Omicron RBD domain in vitro results in a good ability to also neutralize Omicron-pseudotyped virus infection in ACE2-expressing cell cultures. We point out here that D3 mAb maintains a good ability to recognize both the wild-type and Omicron Spike proteins, either when used as recombinant purified proteins or when expressed on pseudoviral particles despite the different variants, making it particularly useful both from a therapeutic and diagnostic point of view. On the basis of these results, we propose to exploit this mAb for combinatorial treatments with other neutralizing mAbs to increase their therapeutic efficacy and for diagnostic use to measure the viral load in biological samples in the current and future pandemic waves of coronaviruses.

Cardiovascular diseases, including thrombosis, are the leading cause of mortality worldwide. The generation of monoclonal antibodies (mAb) targeting specific coagulation factors could provide more targeted and safer anticoagulant therapies. Factor V (FV) is a critical cofactor in the prothrombinase complex, which catalyzes the conversion of prothrombin to thrombin, a key enzyme in the coagulation cascade. We isolated a novel human antibody specific to FV by using phage display technology. The selection occurred by panning a large repertoire of phages expressing human antibody fragments (scFv) in parallel on the purified recombinant protein in its native form (FV) or activated by proteolytic maturation (Factor Va (FVa)). Through ELISA screening, we identified the clone with the highest binding affinity for both targets, and it was successfully converted into IgG1. The novel human mAb, called D9, was found capable of binding to Factor V with a low nM affinity both by ELISA and BLI assays, whereas its cross-reactivity with some other coagulation factors was found null or very poor. Furthermore, when tested in blood clotting tests, it was found able to prolong activated partial thromboplastin time (aPTT). Thus, D9 could become not only a potential therapeutic agent as a specific anticoagulant but also a precious tool for diagnostic and research applications.