Massive parallel screening of phage libraries for the generation of repertoires of human immunomodulatory monoclonal antibodies.

Immune checkpoints are emerging as novel targets for cancer therapy, and antibodies against them have shown remarkable clinical efficacy with potential for combination treatments to achieve high therapeutic index. This work aims at providing a novel approach for the generation of several novel human immunomodulatory antibodies capable of binding their targets in their native conformation and useful for therapeutic applications. We performed a massive parallel screening of phage libraries by using for the first time activated human lymphocytes to generate large collections of single-chain variable fragments (scFvs) against 10 different immune checkpoints: LAG-3, PD-L1, PD-1, TIM3, BTLA, TIGIT, OX40, 4-1BB, CD27 and ICOS. By next-generation sequencing and bioinformatics analysis we ranked individual scFvs in each collection and identified those with the highest level of enrichment. As a proof of concept of the quality/potency of the binders identified by this approach, human IgGs from three of these collections (i.e., PD-1, PD-L1 and LAG-3) were generated and shown to have comparable or better binding affinity and biological activity than the clinically validated anti-PD-1 mAb nivolumab. The repertoires generated in this work represent a convenient source of agonistic or antagonistic antibodies against the 'Checkpoint Immunome' for preclinical screening and clinical implementation of optimized treatments.

Ranolazine Attenuates Trastuzumab-Induced Heart Dysfunction by Modulating ROS Production.

The ErbB2 blocker trastuzumab improves survival in oncologic patients, but can cause cardiotoxicity. The late Na+ current inhibitor ranolazine has been shown to counter experimental HF, including doxorubicin cardiotoxicity (a condition characterized by derangements in redox balance), by lowering the levels of reactive oxygen species (ROS). Since ErbB2 can modulate ROS signaling, we tested whether trastuzumab cardiotoxicity could be blunted by ranolazine via redox-mediated mechanisms. Trastuzumab decreased fractional shortening and ejection fraction in mice, but ranolazine prevented heart dysfunction when co-administered with trastuzumab. Trastuzumab cardiotoxicity was accompanied by elevations in natriuretic peptides and matrix metalloproteinase 2 (MMP2) mRNAs, which were not elevated with co-treatment with ranolazine. Trastuzumab also increased cleavage of caspase-3, indicating activation of the proapoptotic machinery. Again, ranolazine prevented this activation. Interestingly, Neonatal Rat Ventricular Myocytes (NRVMs), labeled with MitoTracker Red and treated with trastuzumab, showed only a small increase in ROS compared to baseline conditions. We then stressed trastuzumab-treated cells with the beta-agonist isoproterenol to increase workload, and we observed a significant increase of probe fluorescence, compared with cells treated with isoproterenol alone, reflecting induction of oxidative stress. These effects were blunted by ranolazine, supporting a role for INa inhibition in the regulation of redox balance also in trastuzumab cardiotoxicity.

A novel fully human anti-NCL immunoRNase for triple-negative breast cancer therapy.

Breast cancer is the most common cancer in women worldwide. A new promising anti-cancer therapy involves the use of monoclonal antibodies specific for target tumor-associated antigens (TAAs). A TAA of interest for immunotherapy of Triple Negative Breast Cancer (TNBC) is nucleolin (NCL), a multifunctional protein, selectively expressed on the surface of cancer cells, which regulates the biogenesis of specific microRNAs (miRNAs) involved in tumor development and drug-resistance. We previously isolated a novel human anti-NCL scFv, called 4LB5, that is endowed with selective anti-tumor effects. Here we report the construction and characterization of a novel immunoRNase constituted by 4LB5 and a human pancreatic RNase (HP-RNase) called "4LB5-HP-RNase". This immunoRNase retains both the enzymatic activity of human pancreatic RNase and the specific binding of the parental scFv to a panel of surface NCL-positive breast cancer cells. Notably, 4LB5-HP-RNase dramatically and selectively reduced the viability and proliferation of NCL-positive tumor cells in vitro and in vivo. Specifically, it induced apoptosis and reduced the levels of the tumorigenic miRNAs miR-21, -221 and -222. Thus, this novel immunoagent could be a valuable tool for the treatment of TNBC patients ineligible for currently available targeted treatments.

Effects of a second-generation human anti-ErbB2 ImmunoRNase on trastuzumab-resistant tumors and cardiac cells.

The inhibition of ErbB2 by the use of human antibodies can be a valuable strategy for the treatment of breast and gastric cancer. Trastuzumab, a humanized anti-ErbB2 antibody in clinical use, is effective but can engender resistance as well as cardiotoxicity. ImmunoRNases, made up of a human anti-ErbB2 scFv and human pancreatic ribonucleases (HP-RNases), have been engineered to overcome the limits of other immunotoxins, such as immunogenicity and nonspecific toxicity. Here, we report that a novel anti-ErbB2 immunoRNase, called Erb-HPDDADD-RNase, obtained by fusing Erbicin, a human ErbB2-directed scFv, with an HP-RNase variant that resists the cytosolic inhibitor protein, binds with high affinity to a panel of ErbB2-positive gastric tumor cells and inhibits their growth more than does the parental immunoRNase, which is not resistant to the inhibitor. Moreover, Erb-HP-DDADD-RNase is endowed with antiproliferative activity for trastuzumab-resistant cancer cells both in vitro and in vivo that is more potent than that of the parental immunoRNase. Importantly, Erb-HP-DDADD-RNase does not show cardiotoxic effects in vitro on human cardiomyocytes and does not impair cardiac function in a mouse model. Thus, Erb-HP-DDADD-RNase could fulfil the therapeutic need of cancer patients ineligible for trastuzumab treatment due to primary or acquired trastuzumab resistance or to cardiac dysfunction.

A novel fully human antitumor immunoRNase resistant to the RNase inhibitor.

The ErbB2 tyrosine kinase receptor is an attractive target for immunotherapy, as it is overexpressed in many carcinomas. ImmunoRNases, made up of a human anti-ErbB2 scFv (single chain antibody fragment) and human RNases, have been engineered to overcome the limits of immunotoxins, made up of mouse antibodies and plant or bacterial toxins, such as immunogenicity and non-specific toxicity. Here we describe the construction and characterization of a second-generation anti-ErbB2 immunoRNase, called ERB-HP-DDADD-RNase, obtained by fusing Erbicin, a human ErbB2-directed scFv, with an inhibitor-resistant variant of human pancreatic RNase (HP-DDADD-RNase). This novel immunoRNase retains both the enzymatic activity of human pancreatic RNase and the specific binding of the parental scFv to ErbB2-positive cells, showing an affinity comparable with that of the previously reported parental immunoRNase (ERB-HP-RNase). Moreover, the novel immunoRNase is endowed with an effective and selective in vitro antiproliferative action for ErbB2-positive tumor cells, which is more potent than that of the parental immunoRNase on tumor cells expressing low levels of ErbB2, due to its resistance to the RNase inhibitor. Thus, the novel immunoRNase could represent a valuable tool for ErbB2-positive cancer therapy.