Platforms and strategies harnessing signaling pathways of multifactorial diseases by multispecific antibodies
Time: Fri 2023-05-26 13.00
Subject area: Biotechnology
Doctoral student: Aman Mebrahtu , Proteinteknologi
Opponent: Doktor Janine Schuurman, The Antibody Society, Lust for Life Science
Supervisor: Professor Johan Rockberg, Proteinteknologi; Adjungerad professor Fredrik Y. Frejd, Uppsala University
Proteins govern a multitude of biological functions vital to sustain life. The ability to withstand diseases development and harboring a defense against foreign pathogens is attributed to the wonders of the immune system and the proteins and cells its comprised of. Antibodies arguably stands as one of the most important protein classes involved in conferring immunity, able to recognize and engage, i.e., bind to pathogenic agents and exert their function. With the rise of engineered antibodies, the last three decades have ushered in an age of targeted therapeutics to address complex diseases with a more favorably efficacy and safety profile. However, an array of these diseases are governed by multifactorial variables often in interplay with each other, demanding a more broadened therapeutic strategy. Hence, significant efforts have been invested in the engineering of antibodies, expanding beyond a single speci- ficity to bi or multispecific molecules able to recognize more than one antigen within one and the same molecule. Naturally, this opens up for a multitude of functions i.e. mode of actions and harnessing of numerous diseases relevant pathways a multispe- cific potential drug compounds could carry out for a therapeutically beneficial out- come. The increased drug design complexity is accompanied with developability chal- lenges related to optimal drug design between the two or more binding specificities to achieve intended effect in a particular diseases’ biology setting. Moreover, the de- velopability profile of multispecific affinity proteins with regards to product yields and quality have long hampered the true translation-ability of these novel drug com- pounds into a clinical and industrial setting. The herein presented thesis aimed at highlighting the importance of a harmonized drug development pipeline taking into account aforementioned challenges and introducing toolboxes, platforms and work- flows to screen and optimize a variety of bispecific drug formats. Furthermore, we exploratively developed four unique bispecific constructs carrying out different mode- of-actions inhabiting partly rationally tailored design with respect to targeted dis- eases setting in the field of autoimmune diseases and oncology.
The first bispecific molecule developed herein presented in paper I, aimed at target- ing the diseases condition in SLE from multiple fronts, with a dual blocking mode of action targeting two related ligands driving diseases progression. A lead bispecific AffiMab format chosen post screening of several candidates in molecular and in vitro systems was evaluated in ex vivo whole blood model assay demonstrating a signifi- cant effect by the dual blocking strategy to actively decrease the levels of the target ligands. The molecule warrants further evaluation in approriate in vivo models and ii ex vivo whole blood assay with patient derived material given the potential beneficial effect of the proposed therapeutic strategy based on the fundmenetal biology of the diseases and clinical observations. In paper II, a novel bispecific format able to de- liver cargo antigens to antigen presenting cells in a modular fashion was developed. Moreover, the bispecific exerts agonistic downstream signaling of targeted cells via CD40 engagement, synergistically priming immune cell activation whilst delivering the cargo antigen simultaneously. The delivery is based on an affinity interaction between a static peptide stretch synthesized with the antigen peptide sequence and a single chain attached to the structure of an anti-CD40 agonistic antibody. Employ- ment of the established adaptable drug affinity conjugate platform (ADAC) enabled the delivery of antigen cargo strictly dependent on the affinity interaction, inducing a significant anti-tumor response by expansion of antigen specific CD8+ T cells demonstrated in vivo.
In paper III, we explore a HER2 and EGFR dual blocking strategy employing bis- pecific AffiMabs. The bispecifics demonstrated a significantly greater effect in an in vitro cell based assay compared to the combination treatment with the two monospe- cific molecules targeting respective antigen, indicating a potential synergistic effect conferred by the format. However, the effect of the molecule and potential benefit versus the monospecific or combination treatment need to be further evaluated in vivo. Paper IV aimed at harnessing the CD40 dendritic cell activation axis by a bispecific immune cell engager AffiMab, governing CD40 mediated activation depen- dent on the engagement with a stroma antigen upregulated in the tumor microenvi- ronment, platelet growth factor receptor B (PDGFRβ). The AffiMab demonstrated the intended mode of action in in vitro cell based model assays, and with isolated antigen presenting cells and B cells from healthy donor blood, albeit room for format optimization should be taken into consideration. The study warrants further investi- gation in appropriate in vivo models for treatment of solid tumors.
In paper V we developed a modular platform to fine tune protein expression in mammalian cells on a translational level utilizing 5’UTR hairpin structure, herein coined as Regulatory elements (RgEs). Hypothesizing that “less is more” wherein a balanced expression of a proteins subunits was demonstrated to be of greater impor- tance than a maximum expression output of each component to apprehend correctly assembled protein product. The developed tool box holds possibility for multifaceted applications, and was extended in paper VI to the use in the establishment of an in vitro culture system to fine tune receptor densities on the cell surface of a defined iii cell line. The applications end-use would be functioning as an integrative part in the high throughput screening pipeline of bispecific immune cell engagers for early eval- uation and ranking of formats and access to target antigens impact on the function- ality of screened constructs.
In summary, the herein presented work exploratively evaluated mode of actions, de- sign, format, and engineering of bispecific molecules to address both challenges in terms of achieving intended effect but equally important considerations and solutions to improve and evaluate product manufacturability early on in the drug development pipeline.