Monoclonal Class Research Articles

Antibody–drug conjugates in the treatment of lymphoid neoplasms

SummaryAntibody-drug conjugates (ADCs) are a new class of monoclonal antibodies with the characteritic to specifically target tumor cells and to deliver a cytotoxic drug directly to the target cell thereby minimising side effects and improving the therapeutic index. In recent years, many new ADCs have been approved and are established therapeutic tools in lymphoma treatment.

Abstract 4115: Unleashing the power of MHC associated peptide proteomics: Immunogenicity assessment of oncology drugs

Abstract Bispecifics targeting multiple antigens or epitopes have been showing great promise for treatment of cancer. However, managing unwanted immunogenicity has become a challenge in the development cycle of these promising therapeutics as there is a trend towards higher unwanted immune responses compared with classical monoclonal antibodies. A thorough assessment of their immunogenic potential leads to safe biotherapeutics with high treatment efficacy. MAPPS assays (MHC associated peptide proteomics) enable the precise identification of all the regions of a protein that may evoke an immune response. This information is key for correct risk assessment and for modulating biotherapeutics. High-sensitive MAPPS workflow leads to higher numbers of identified peptides (self + non-self peptides) and gives the deepness of analysis required for confident immunogenicity derisking and modulation. We show the importance of peptides presented by HLA-DP and HLA-DQ (next to the standard HLA-DR presented peptides). Next, we also show the first ever comparison of presented peptides in true immune cells: dendritic cells (as compared to monocyte derived dendritic cells) and B cells. Citation Format: Sofie Pattyn. Unleashing the power of MHC associated peptide proteomics: Immunogenicity assessment of oncology drugs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4115.

A new class of monoclonal Aβ antibodies selectively targets and triggers deposition of Aβ protofibrils.

Aggregation and accumulation of amyloid-β peptide (Aβ) are a critical trigger for the onset of Alzheimer's disease (AD). While the plaques are the most outstanding Aβ pathological feature, much of the recent research emphasis has been on soluble Aβ species because of their diffusible, proinflammatory, and toxic properties. The focus on soluble aggregated Aβ species has also increased the interest in antibodies that are selective for different Aβ conformations. In the current study, we developed and characterized a new class of monoclonal antibodies (referred to as mAbSL) that are selective for Aβ protofibrils. Cloning and sequencing of the heavy and light chain variable regions for multiple antibodies identified sequence characteristics that may impart the conformational selectivity by the antibodies. Transfection of FreeStyle 293F cells with the plasmids permitted in-house expression and purification of mAbSL antibodies along with non-conformation-selective Aβ monoclonal antibodies (Aβ mAbs). Several of the purified mAbSL antibodies demonstrated significant affinity and selectivity for Aβ42 protofibrils compared with Aβ42 monomers and Aβ42 fibrils. Competition ELISA assays assessing the best overall antibody, mAbSL 113, yielded affinity constants of 7 nM for the antibody-Aβ42 protofibril interaction, while the affinity for either Aβ42 monomers or Aβ42 fibrils was roughly 80 times higher. mAbSL 113 significantly inhibited Aβ42 monomer aggregation by a unique mechanism compared with the inhibition displayed by Aβ mAb 513. Aβ42 protofibril dynamics were also markedly altered in the presence of mAbSL 113, whereby insoluble complex formation and protofibril deposition were stimulated by the antibody at low substoichiometric molar ratios. As the field contemplates the therapeutic effectiveness of Aβ conformation-selective antibodies, the findings presented here demonstrate new information on a monoclonal antibody that selectively targets Aβ protofibrils and impacts Aβ dynamics.

Recently approved and emerging monoclonal antibody immune checkpoint inhibitors for the treatment of advanced non-small cell lung cancer

ABSTRACT Introduction CTLA-4/PD-1/PD-L1- directed immune checkpoint inhibitors (ICIs) are one of the standard therapies for the treatment of advanced non-small cell lung cancer (NSCLC). However, some new classes of monoclonal antibodies are emerging as promising therapies for advanced NSCLC. Areas covered Therefore, this paper aims to provide a comprehensive review of the recently approved as well as emerging monoclonal antibody immune checkpoint inhibitors for the treatment of advanced NSCLC. Expert opinion Further and larger studies will be needed to explore the promising emerging data on new ICIs. Future phase III trials could allow us to properly assess the role of each immune checkpoints in the wider context of the tumor microenvironment and thus the best new ICIs to use, the best approach and the most effective subset of patients to select.

Construction of Multi-Specific Antibody by Genetic Engineering and Its Progress in Tumor Therapy

Targeted treatment of cancer with monoclonal antibodies increases the benefit for patients. In order to improve the anti-tumor activity of monoclonal antibodies, multi-specific antibodies have entered the research field. The emergence of various techniques to produce multi-specific recombinant antibody molecules has led to the selection of target combinations in various forms. To date, only a few multi-specific constructs have entered phase III clinical trials, in contrast to classical monoclonal antibodies. Some of the format options are outlined from a technical point of view. We focus on the achievements and prospects of the underlying technologies for generating biand multispecific antibodies.

Late-onset toxicities of monoclonal antibodies in cancer patients.

Cancer therapy duration is variable and may take years, adding a new challenge of maintaining the best life quality for cancer survivors. In cancer patients, late-onset toxicities have been reported with monoclonal antibodies and may involve several body organs or systems. They are defined as an autoimmune illnesses that can happen months to years after treatment discontinuation. Late-onset toxicities have become a focus of clinical care and related research. After cancer therapy is completed, the patient should receive longitudinal follow-up to detect these late effects as early as possible. The current review summarizes the recently reported late-onset toxicities of four classes of monoclonal antibodies (anti-CD52, anti-CTLA-4, anti-PD-1 andanti-CD20) with guidance for the diagnostic tools, appropriate managementand treatment.

3P Targeting pancreatic adenocarcinoma upregulated factor (PAUF) to treat pancreatic cancer (PC): In vivo efficacy and safety of PBP1510, a first in class monoclonal antibody (mAb)

PAUF plays a key role in PC tumour progression and metastasis by inducing cancer cell proliferation, angiogenesis and evasion of immune surveillance. PBP1510 developed by Prestige Biopharma Limited, is a novel humanized IgG1 mAb that binds to and neutralizes PAUF with high specificity and affinity. There are no targeted therapies against PAUF, making PBP1510 the first in this class.

Application of inline variable pathlength technology for rapid determination of dynamic binding capacity in downstream process development of biopharmaceuticals.

Determination of dynamic binding capacity (DBC) for capture purification chromatographic step is usually the first experiment to be performed during downstream process development of biopharmaceuticals. In this work, we investigated the application of inline variable pathlength technology using FlowVPE for rapid determination of DBC on affinity resins for protein capture and proved its comparability with offline titer methods. This work also demonstrated that variable pathlength technology for DBC determination can be successfully applied to different classes of monoclonal antibodies and fusion proteins. This enabled rapid screening of affinity resins and optimization of the capture chromatography step. Hence, use of inline variable pathlength technology eliminated the dependency on offline titer data, traditionally used for DBC determination and accelerated overall process development timelines with less cost.

Safety, tolerability and preliminary efficacy of CAN04, a first in class monoclonal antibody against IL1RAP, in combination with nab-paclitaxel and gemcitabine (NG) in subjects with pancreatic cancer.

e16228 Background: Interleukin-1 Receptor Accessory Protein (IL1RAP) is expressed on cancer and stromal cells in many solid tumors. CAN04 is a fully humanized IgG1 targeting IL1RAP blocking IL-1α and β signaling and triggering ADCC. As monotherapy, CAN04 has been administered without reaching MTD up to 15mg/kg. We report initial data from CAN04 in combination with NG in pts with pancreatic cancer (PDAC). Methods: Primary objective was to determine safety and tolerability of CAN04 in combination with standard NG as first line treatment in pts with locally advanced/metastatic PDAC. Secondary objectives included establishing preliminary efficacy. Tumor responses were evaluated according to RECIST/iRECIST. Results: 36 patients (pts) received at least 1 dose of CAN04: median age 62 yrs (46-87), 47% women, 94% stage IV, 8% had received prior adjuvant therapy; 59% ECOG 0, 41% ECOG 1. Dosing was initiated at 5mg/kg, escalated to 7.5mg/kg (n = 8) which was considered above MTD due to hematological toxicity, followed by expansion at 5mg/kg. Infusion related reactions (IRRs) were seen primarily with CAN04 priming dose of 0.5 mg/kg (25% G1, 25% G2, 3% G3). G3 or higher AEs (all/related) were dominated by hematological toxicity and reported in 89%/72% of pts (see table). SAEs were reported in 67% pts (44% G3/G4), in 33% considered related (19% G3/G4). 33% of pts discontinued due to AEs: 4 deterioration of general condition, 2 IRR, 2 bilirubin elevation, 1 bile duct obstruction, 1 hemolytic uremic syndrome, 1 pancreatitis, 1 asthenia, 1 decreased appetite, 1 pneumonitis. There were 3 on treatment deaths: disease progression, gastrointestinal obstruction and cholangitis. For the mITT efficacy analysis (n = 31), 5 pts were excluded: 3 discontinued before receiving NG (2 consent withdrawals after IRRs, tumor related physical deterioration) and 2 did not complete Cycle 1 due to cholangitis and GI obstruction respectively. 12 pts (39%) had confirmed or unconfirmed PR as best response, 8 (26%) more showed SD and 9 (29%) had PD. Six pts underwent PD confirmation: 3 pts had prolonged immune unconfirmed PD (iUPD) by iRECIST and > 50% decreases in CA19-9 and were on treatment for 4.5 (ongoing), 6 and 8 months, respectively. Clinical benefit rate (PR+SD+prolonged iUPD): 74%. At the time of this analysis, 12 pts (38%) are ongoing. Median duration of response is currently 7.5 months (1.8-13.8 months). Conclusions: The clinical benefit rate of CAN04 in combination with NG is encouraging (74%). The G3/G4 neutropenia and febrile neutropenia rate is higher than expected for NG alone. Expansion cohorts at lower CAN04 doses have been initiated. Clinical trial information: NCT03267316. [Table: see text]

Bovine serum albumin affects N-glycoforms of murine IgG monoclonal antibody purified from hybridoma supernatants.

Immunoglobulin G (IgG) is a class of monoclonal antibodies (mAbs) commonly produced in mammalian cell lines. These cell lines are grown in finely adjusted culture media, which contain components that may impact glycoforms. As variation of N-glycoforms can impact the biological properties of IgGs, medium composition should be controlled. Here, we studied the effects on IgG N-glycoforms of different components in hybridoma culture media, specifically compared bovine serum albumin (BSA) with other small molecules, using a matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight multistage mass spectrometry (MALDI-QIT-TOF MSn)-based approach. We show that small molecular additives caused little change in glycan species, though a number of these reagents, especially glutamine, affected levels of glycosylation. In comparison, the addition of macromolecular protein BSA significantly changed IgG N-glycan patterns, not only in species but also in glycosylation levels. Together, our finding suggests that BSA increases the complexity of IgG N-glycoforms, thus raising the difficulty in maintaining glycoforms consistency during antibody production. Therefore, the effect of BSA on IgG N-glycans should be considered when designing optimal medium formulations for IgG production. KEY POINTS: • Small molecular medium additives only affect glycosylation levels of IgG N-glycans. • BSA significantly changes IgG N-glycoforms as a medium additive. • BSA's skewing of IgG N-glycoforms should be considered in IgG production.

Immune Checkpoint Inhibitors in Melanoma: A Review of Pharmacokinetics and Exposure–Response Relationships

Immune checkpoint inhibitors are a new class of monoclonal antibodies that amplify T-cell-mediated immune responses against cancer cells. The introduction of these new drugs, first anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA4) and then anti-programmed death-1 (anti-PD1), was a major improvement in the treatment of advanced or metastatic melanoma, a highly immunogenic tumour. The development strategy for immune checkpoint immunotherapies differed from that traditionally used for cytotoxic therapies in oncology. The choices of doses at which to conduct clinical trials, and subsequently the choice of doses at which to use these new therapies, were not based on the identification of a maximum tolerated dose from dose-escalation studies; thus, pharmacokinetic and pharmacokinetic-pharmacodynamic modelling was essential. The studies conducted have shown that the pharmacokinetics of ipilimumab were linear and not time-dependent. In addition, there was a correlation between the trough concentrations of ipilimumab and its therapeutic efficacy. On the contrary, the anti-PD1 immunotherapies nivolumab and pembrolizumab had time-dependent pharmacokinetics. Their therapeutic efficacy was not related to their trough concentration, but there was a correlation between the clearance of anti-PD1 and the survival of melanoma patients. This review highlights the complexity of interpreting the exposure-response relationships of these agents. Further studies are needed to assess the value of therapeutic drug monitoring of immune checkpoint inhibitors in the treatment of melanoma.

Management of Thrombocytopenia in Patients with Chronic Liver Disease.

Thrombocytopenia is the most common hematologic complication associated with chronic liver disease (CLD) with important clinical implications. While the mechanisms for thrombocytopenia are multifactorial, platelet sequestration in the spleen and decreased thrombopoietin (TPO) production are the main mechanisms in patients with CLD. This review outlines the current treatment options for thrombocytopenia in patients with CLD, explores their limitations, and proposes a revised treatment algorithm for the management of thrombocytopenia in this patient group. A PubMed search of the literature was undertaken with search terms focused on CLD and thrombocytopenia. Until now, the standard-of-care treatment in these patients has been the use of platelet transfusions either prophylactically or periprocedurally to control bleeding. Treatment options, such as splenic artery embolization and splenectomy, are invasive, and their utility is limited by significant complications. The US Food and Drug Administration recently approved 2s-generation TPO-receptor agonists, avatrombopag and lusutrombopag, as safe and effective therapies for the treatment of thrombocytopenia in patients with CLD scheduled to undergo a procedure. The addition of avatrombopag and lusutrombopag offers physicians an alternative to platelet transfusions in patients with CLD who have to undergo medical/dental procedures that could potentially put them at an increased risk of bleeding. There are several other drugs in the research pipeline at various stages of development, including a new class of monoclonal antibodies that can bind to and activate TPO-receptor agonists. The outlook for treatment choices for thrombocytopenia in patients with liver disease is promising.

Tomato endo beta-mannanase: A candidate of potential tomato allergen protein detected with human monoclonal antibody established from a patient suffered from Japanese cedar pollinosis.

Peripheral blood lymphocytes from a patient allergic to Japanese cedar pollens were transformed by Epstein-Barr virus infection. Some transformed B-lymphoblastoid cells (BLCs) secreted IgM class antibodies to cedar pollen extracts and tomato fruit extracts. One stable human-mouse hybridoma clone Y-22-3-3 secreting IgM class monoclonal antibody to tomato fruit extracts was established by cell fusion of BLCs with mouse myeloma cells. Western blot analysis of tomato extracts showed Y-22-3-3 monoclonal antibody recognized a tomato protein with a molecular weight of 40 kDa. The CBB-stained 40 kDa protein from antibody-affinity chromatography was analyzed by MALDI-TOF/TOF, and identified as tomato endo-beta-mannanase, which was previously reported as one of the potential candidates for tomato allergens.

Generation of site-distinct N-glycan variants for in vitro bioactivity testing.

Glycosylation, a critical product quality attribute, may affect the efficacy and safety of therapeutic proteins in vivo. Chinese hamster ovary fed-batch cell culture batches yielded consistent glycoprofiles of a Fc-fusion antibody comprizing three different N-glycosylation sites. By adding media supplements at specific concentrations in cell culture and applying enzymatic glycoengineering, a diverse N-glycan variant population was generated, including high mannose, afucosylated, fucosylated, agalactosylated, galactosylated, asialylated, and sialylated forms. Site-specific glycosylation profiles were elucidated by glycopeptide mapping and the effect of the glycosylation variants on the FcγRIIIa receptor binding affinity and the biological activity (cell-based and surface plasmon resonance) was assessed. The two fusion body glycosylation sites were characterized by a high degree of sialic acid, more complex N-glycan structures, a higher degree of antennarity, and a site-specific behavior in the presence of a media supplement. On the other hand, the media supplements affected the Fc-site glycosylation heterogeneity similarly to the various studies described in the literature with classical monoclonal antibodies. Enzymatic glycoengineering solely managed to generate high levels of galactosylation at the fusion body sites. Variants with low core fucosylation, and to a lower extent, high mannose glycans exhibited increased FcγRIIIa receptor binding affinity. All N-glycan variants exhibited weak effects on the biological activity of the fusion body. Both media supplementation and enzymatic glycoengineering are suitable to generate sufficient diversity to assess the effect of glycostructures on the biological activity.

Monoclonal Antibodies for the Treatment of Melanoma: Present and Future Strategies.

Metastatic melanoma is a dreadful type of skin cancer arising due to uncontrolled proliferation of melanocytes. It has very poor prognosis, low 5-year survival rates and until recently there were only handful of treatment options for metastatic melanoma patients. The drugs that were approved for the treatment had low response rates and were associated with severe adverse events. With the introduction of monoclonal antibodies against inhibitory immune checkpoints the treatment landscape for metastatic melanoma has changed dramatically. Ipilimumab, the first monoclonal antibody to be approved for the treatment of metastatic melanoma, showed significant improvements in durable response rates in patients and paved the way for next class of monoclonal antibodies. Nivolumab and pembrolizumab, the anti-PD-1 antibodies that were approved 3-years after the approval of ipilimumab, had decent response rates, low relapse rates and showed manageable safety profile. Antibodies against ligands for PD-1 receptors were then developed to overcome the adverse effects of anti-PD-1 antibodies and combination of monoclonal antibodies (ipilimumab plus nivolumab) was tested to increase the response rates. Additional target receptors that regulate Tcell activity were identified on T cells and monoclonal antibodies against potential targets such as TIGIT, TIM-3, and LAG-3 were developed. This chapter discusses the details of monoclonal antibodies used for the treatment of melanoma along with the ones that could be introduced in the near future with emphasis on mechanisms by which antibodies stimulate anti-tumor immune response and the specifics of target molecules of the antibodies.

CD16A-Specific Tetravalent Bispecific Immune Cell Engagers Potently Induce Antibody-Dependent Cellular Phagocytosis (ADCP) on Macrophages

IntroductionAffimed has developed high affinity tetravalent bispecific immune cell engagers for redirected optimized cell killing (ROCK platform). Using anti-CD16A and anti-tumor target-specific antibody domains, the engagers activate NK cells to efficiently kill target cells. The most advanced ROCK-based immune cell engager, AFM13, targeting CD30 on tumor cells and CD16A on immune effectors, is currently being evaluated in several clinical trials to treat CD30-positive malignancies.Based on the fact that CD16A is not exclusively expressed on NK cells, but also on macrophages, we hypothesized that CD16A-specific immune cell engagers would also be able to activate CD16A expressing macrophages through antibody-dependent cellular phagocytosis (ADCP) contributing to anti-tumor response.Macrophages are an essential component of the innate immune system and are a major constituent of normal tissues. They can be broadly classified into different subtypes including M1 (classically activated, generally characterized as pro-inflammatory and immuno-supportive) and M2 (alternatively activated, primarily of an anti-inflammatory profile) subtypes. Those subtypes greatly differ in their phenotype and function and appear to be highly plastic. While M1 macrophages are generally considered to be tumoricidal, M2 macrophages are mostly tumorigenic, depending on their context within the tumor microenvironment. Therapeutic agents focusing on macrophages such as the CD47/SIRPa axis, CSF-1R antibodies and elimination of tumor-associated macrophages (TAMs) have recently come into focus in immuno-oncology.MethodsPeripheral monocytes derived from primary human hematopoietic cells of healthy donors were used to generate various macrophage subtypes (unpolarized macrophages, M1, M2a, M2c) in vitro using well-defined cytokine cocktails. These subtypes were characterized phenotypically for their CD16A expression and a wide number of additional markers. Subsequently, they were used to investigate the ability of a number of different CD16A-specific immune cell engagers derived from Affimed´s ROCK platform and control antibodies in vitro to activate and induce ADCP of target cells by flow cytometry and microscopy.ResultsWe demonstrated that all of the macrophage subtypes generated in this study expressed CD16A and mediated ADCP of tumor cells. In addition, we showed that ADCP of tumor cells by several CD16A-specific engagers was both fast and robust for all investigated macrophage subtypes. Specifically, ADCP was detected as early as 2 hours after co-incubation of tumor cells with M1 or M2 macrophages and CD16A-specific immune cell engagers. Using appropriate control antibodies, it was demonstrated that ADCP mediated by CD16A-specific immune cell engagers was selective and at least as potent as ADCP mediated by classical monoclonal antibodies pan-specific for Fc-gamma receptors.Summary and conclusion:We have demonstrated a new mechanism whereby Affimed´s CD16A-specific immune cell engaging antibodies eliminate tumor cells by ADCP, mediated by different subsets of macrophages. Our data suggest that these antibodies may have the potential to boost tumoricidal function within the tumor microenvironment. Future directions of leveraging innate immunity as a therapeutic option in immuno-oncology will be presented. DisclosuresWingert:Affimed: Employment. Reusch:Affimed: Employment. Beez:Affimed: Employment. Pahl:Affimed: Research Funding. Cerwenka:Affimed: Research Funding; Dragonfly Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Koch:Affimed GmbH: Employment. Treder:Affimed GmbH: Employment.

Case reports of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition nonresponse

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, a novel class of monoclonal antibodies, reduces low-density lipoprotein cholesterol levels and improves cardiovascular outcomes. Given the short time frame, these agents have been available for use; reports of nonresponse to the PCSK9 inhibitor therapy are scarce in literature. We describe 2 cases with substantially lesser than expected low-density lipoprotein cholesterol lowering on PCSK9 therapy. Nonresponse to PCSK9 inhibition was attributed to autosomal recessive hypercholesterolemia (secondary to low-density lipoprotein receptor adaptor protein 1 mutation) and plasmapheresis after PCSK9 inhibitor drug injections. Additional PCSK9 inhibitor nonresponders are likely to emerge as the use of these agents increases overtime.

Structural characterization of broadly neutralizing alphavirus antibodies

Abstract Mayaro is a mosquito-borne single-stranded positive RNA alphavirus endemic to tropical regions of South America. It is closely related to other arthritogenic alphaviruses, such as Chikungunya, Semliki Forest, Ross River, and Sindbis viruses. Although there are currently no available vaccines or therapies for alphaviruses, previous studies demonstrate that cross-protection between different alphaviruses could be mediated by antibodies that map to conserved epitopes. For example, a class of monoclonal antibodies against Chikungunya were recently shown to neutralize other alphaviruses by blocking viral entry and egress, all with epitopes on the surface E2 glycoprotein. A panel of antibodies generated against Mayaro infection and boosted with recombinate E2 protein were also found to be cross-neutralizing against other alphaviruses. Currently, epitope mapping and structural studies are being performed on these antibodies in order to determine the vital residues for binding, as well as to determine the mechanism of cross-neutralization.

Abatacept for Treatment of Rheumatoid Arthritis: Special Focus on the Elderly.

Targeted therapies have been developed for patients with rheumatoid arthritis (RA) for whom prior treatment with traditional disease-modifying anti-rheumatic drugs has failed. The numerous different signaling pathways now targeted by various classes of monoclonal antibodies and small molecule inhibitors may complicate treatment decisions. Abatacept selectively modulates a co-stimulatory signal necessary for T-cell activation. Thus, abatacept is effective in biologic-naive patients and in those for whom biologic therapy has failed. Emerging evidence indicates different benefits depending on patient and disease characteristics. In RA, the clinical goal should be clinical and radiographic remission to prevent structural damage and functional impairment. Nevertheless, the management of elderly patients with RA is often less aggressive, and the treat-to-target strategy is less respected in this age category than in the treatment of RA in younger patients. However, abatacept treatment in elderly patients is as effective and well-tolerated as in younger patients. This review summarizes recently published data on pharmacological properties; clinical and biological data on efficacy, drug retention, and safety, focusing on age; and evidence-based criteria for choosing abatacept or an alternative targeted therapy.

MiR-143 targets MAPK7 in CHO cells and induces a hyperproductive phenotype to enhance production of difficult-to-express proteins.

In recent years, the number of complex but clinically effective biologicals such as multi-specific antibody formats and fusion proteins has increased dramatically. However, compared to classical monoclonal antibodies (mAbs), these rather artificially designed therapeutic proteins have never undergone millions of years of evolution and thus often turn out to be difficult-to-express using mammalian expression systems such as Chinese hamster ovary (CHO) cells. To provide access to these sophisticated but effective drugs, host cell engineering of CHO production cell lines represents a promising approach to overcome low production yields. MicroRNAs (miRNAs) have recently gained much attention as next-generation cell engineering tools. However, only very little is known about the capability of miRNAs to specifically increase production of difficult-to-express proteins. In a previous study we identified miR-143 amongst others to improve protein production in CHO cells. Thus, the aim of the present study was to examine if miR-143 might be suitable to improve production of low yield protein candidates. Both transient and stable overexpression of miR-143 significantly improved protein production without negatively affecting cell growth and viability of different recombinant CHO cells. In addition, mitogen-activated protein kinase 7 (MAPK7) was identified as a putative target gene of miR-143-3p in CHO cells. Finally, siRNA-mediated knock-down of MAPK7 could be demonstrated to phenocopy pro-productive effects of miR-143. In summary, our data suggest that miR-143 might represent a novel genetic element to enhance production of difficult-to-express proteins in CHO cells which may be partly mediated by down-regulation of MAPK7. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1046-1058, 2017.