When will we have a clone? An industry perspective on the typical CLD timeline.

Cell line development (CLD) represents a complex but highly critical process during the development of a biological drug. To shed light on this crucial workflow, a team of BioPhorum members (authors) has developed and executed surveys focused on the activities and effort involved in a typical CLD campaign. An average of 27 members from different companies that participate in the BioPhorum CLD working group answered surveys covering three distinguishable stages of a standard CLD process: (1) Pre-transfection, including vector design and construction; (2) Transfection, spanning the initial introduction of vector into cells and subsequent selection and analysis of the pools; and (3) Single Cell Cloning and Lead Clone Selection, comprising methods of isolating single cells and confirming clonal origin, subsequent expansion and screening processes, and methods for identifying and banking lead clones. The surveys were very extensive, including a total of 341 questions split between antibody and complex molecule CLD processes. In this survey review, the authors interpret and highlight responses for antibody development and, where relevant, contrast complex molecule development challenges to provide a comprehensive industry perspective on the typical time and effort required to develop a CHO production cell line.

A genetic off-target event in a site-specific integration cell line expressing monoclonal antibody has no impact on commercial suitability.

Site-specific integration (SSI) cell line systems are gaining popularity for biotherapeutic development and production. Despite the proven advantages for these expression hosts, the SSI system is still susceptible to rare off-target events and potential vector rearrangements. Here we describe the development process of an SSI cell line for production of an IgG1 monoclonal antibody (mAb-086). During cell line generational studies to assess suitability of clone C10 for commercial purposes, restriction fragment lengths of genomic DNA harboring the light chain (LC) were not in agreement with the predicted size. We first confirmed that the SSI landing-pad achieved occupancy of the desired expression plasmid. Additional investigation revealed that random integration had occurred, resulting in the acquisition of a partial copy of the LC and a full-length copy of the heavy chain (HC) at a different locus in the host genome. This off-target event had no impact on the genotypic consistency and phenotypic stability of the cell line, the production process, or the drug substance product quality. Given the genetic, phenotypic, and process consistency of the cell line, clone C10 was deemed suitable as a manufacturing cell line.

CHOK1SV GS-KO SSI expression system: A combination of the Fer1L4 locus and glutamine synthetase selection.

There are an ever-increasing number of biopharmaceutical candidates in clinical trials fueling an urgent need to streamline the cell line development process. A critical part of the process is the methodology used to generate and screen candidate cell lines compatible with GMP manufacturing processes. The relatively large amount of clone phenotypic variation observed from conventional "random integration" (RI)-based cell line construction is thought to be the result of a combination of the position variegation effect, genome plasticity and clonal variation. Site-specific integration (SSI) has been used by several groups to temper the influence of the position variegation effect and thus reduce variability in expression of biopharmaceutical candidates. Following on from our previous reports on the application of the Fer1L4 locus for SSI in CHOK1SV (10E9), we have combined this locus and a CHOK1SV glutamine synthetase knockout (GS-KO) host to create an improved expression system. The host, CHOK1SV GS-KO SSI (HD7876), was created by homology directed integration of a targetable landing pad flanked with incompatible Frt sequences in the Fer1L4 gene. The targeting vector contains a promoterless GS expression cassette and monoclonal antibody (mAb) expression cassettes, flanked by Frt sites compatible with equivalent sites flanking the landing pad in the host cell line. SSI clones expressing four antibody candidates, selected in a streamlined cell line development process, have mAb titers which rival RI (1.0-4.5 g/L) and robust expression stability (100% of clones stable through the 50 generation "manufacturing window" which supports commercial manufacturing at 12,000 L bioreactor scale).

Recombinase-mediated cassette exchange (RMCE) for monoclonal antibody expression in the commercially relevant CHOK1SV cell line.

To meet product quality and cost parameters for therapeutic monoclonal antibody (mAb) production, cell lines are required to have excellent growth, stability, and productivity characteristics. In particular, cell line generation stability is critical to the success of a program, especially where high cell line generation numbers are required for large in-market supply. However, a typical process for developing such cell lines is laborious, lengthy, and costly. In this study, we applied a FLP/FRT recombinase-mediated cassette exchange (RMCE) system to build a site-specific integration (SSI) system for mAb expression in the commercially relevant CHOK1SV cell line. Using a vector with a FRT-flanked mAb expression cassette, we generated a clonal cell line with good productivity, long-term production stability, and low mAb gene-copy number indicating the vector was located in a 'hot-spot.' A SSI host cell line was made by removing the mAb genes from the 'hot-spot' by RMCE, creating a 'landing pad' containing two recombination cassettes that allow targeting of one or two copies of recombinant genes. Cell lines made from this host exhibited excellent growth and productivity profiles, and stability for at least 100 generations in the absence of selection agents. Importantly, while clones containing two copies had higher productivity than single copy clones, both were stable over many generations. Taken together, this study suggests the use of FLP-based RMCE to develop SSI host cells for mAb production in CHOK1SV offers significant savings in both resources and overall cell line development time, leading to a shortened 'time-to-clinic' for therapeutic mAbs.

Anti-PDGF-B monoclonal antibody reduces liver fibrosis development.

AIM: To evaluate the usefulness of a platelet-derived growth factor (PDGF)-B specific monoclonal antibody (mAb) as a therapeutic agent to treat chronic liver fibrosis. METHODS: Liver fibrosis was induced in ICR mice by bile duct ligation (BDL) or BALB/c mice by weekly injection of concanavalin A (ConA) for 4 or 8 weeks. A mAb specific for mouse and human PDGF-B chain, AbyD3263, was generated, tested in vitro and administered twice a week throughout the experimental period. RESULTS: AbyD3263 showed neutralizing activity against mouse and human PDGF-B chain in cell-based assays, as measured in vitro by inhibition of phosphorylation of PDGF receptor ß and proliferation of hepatic stellate cells induced by PDGF-BB. The half life of AbyD3263 in mice exceeded 7 days and dosing of animals twice a week resulted in constant plasma levels of the mAb. Induction of liver fibrosis by BDL and ConA resulted in elevated levels of alanine aminotransferase (ALT) in plasma and hydroxyproline in the liver. Treatment with AbyD3263 did not modify ALT levels, but significantly reduced hydroxyproline content in the liver with a maximum reduction of 39% and 54% in the BDL and ConA models, respectively, compared to controls. Conclusios: Consistent with the notion that PDGF-BB plays an important role in the progression of liver fibrosis, AbyD3263 exhibits efficacy in pre-clinical disease models suggesting that pharmacological inhibition of PDGF-B chain may be a therapeutic approach to treat liver fibrosis.

Human monoclonal antibodies to the insulin-like growth factor 1 receptor inhibit receptor activation and tumor growth in preclinical studies.

INTRODUCTION: The insulin-like growth factor type 1 (IGF-1) receptor contributes importantly to transformation and survival of tumor cells both in vitro and in vivo, and selective antagonists of the IGF-1 receptor (IGF-1R) activity represent an attractive experimental approach for human cancer therapy. METHODS: Using a phage display library, we identified several high-affinity fully human monoclonal antibodies with inhibitory activity against both human and rodent IGF.1Rs. RESULTS: These candidate therapeutic antibodies recognized several distinct epitopes and effectively blocked ligand-mediated receptor signal transduction and cellular proliferation in vitro. They also induced IGF-1R downregulation and catabolism following antibody-mediated endocytosis. These antibodies exhibited activity against human, primate, and rodent IGF-1Rs, and dose-dependently inhibited the growth of established human tumors in nude mice. CONCLUSION: These fully human antibodies therefore have the potential to provide an effective anti-tumor biological therapy in the human clinical setting.

The generation of stable, high MAb expressing CHO cell lines based on the artificial chromosome expression (ACE) technology.

The manufacture of recombinant proteins at industrially relevant levels requires technologies that can engineer stable, high expressing cell lines rapidly, reproducibly and with relative ease. Commonly used methods incorporate transfection of mammalian cell lines with plasmid DNA containing the gene of interest. Identifying stable high expressing transfectants is normally laborious and time consuming. To improve this process, the ACE System has been developed based on pre-engineered artificial chromosomes with multiple recombination acceptor sites. This system allows for the targeted transfection of single or multiple genes and eliminates the need for random integration into native host chromosomes. To illustrate the utility of the ACE System in generating stable, high expressing cell lines, CHO based candidate cell lines were generated to express a human monoclonal IgG1 antibody. Candidate cell lines were generated in under 6 months and expressed over 1 g/L and with specific productivities of up to 45 pg/cell/day under non-fed, non-optimized shake flask conditions. These candidate cell lines were shown to have stable expression of the monoclonal antibody for up to 70 days of continuous culture. The results of this study demonstrate that clonal, stable monoclonal antibody expressing CHO based cell lines can be generated by the ACE System rapidly and perform competitively with those cell lines generated by existing technologies. The ACE System, therefore, provides an attractive and practical alternative to conventional methods of cell line generation.