Characterization of novel bispecific ADAPTs selected for cancer-related targets

Sammanfattning: Cancer is still one of the most common causes of death world-wide and in parallel there is a need to update the repertoire of therapies that withstand resistance of recurrent cancers. Since the introduction of antibody therapies as anti-cancer pharmaceuticals, recognized as immunotherapy in health care, it has been an increasing field in cancer therapy, as a more targeted treatment compared to chemotherapy. Despite the great success, immunotherapy rely on parenteral administration, partly due to poor tissue penetration. If the treatment is administered intravenously, specialized personnel is required, in addition to that it can be inconvenient for the patient. Also, pharmaceuticals based on antibodies often require costly production steps which yields a high-priced treatment. To approach this problem, researchers have developed small affinity domains with the aim to increase tissue penetration while keeping a high specificity to its target. Albumin Binding Domain Derived Affinity Protein (ADAPT) is an example of a small affinity domain of only 7 kDa, which is based on albumin binding domain (ABD) from the streptococcal protein G. Recently, it was shown that the ADAPTs can be further engineered to bind albumin and another relevant target protein of interest simultaneously, which suggests a tolerable half-life in patient serum, alternative administration routes and lower production costs compared to antibody treatments. Furthermore, less side effects are expected due to higher specificity compared to chemotherapy. This work presents the characterization of novel ADAPT proteins that the target the cancer relatedproteins C-C motif ligand 7 (CCL7), vascular endothelial growth factor A (VEGF-A) and carcinoembryonic antigen related cell adhesion molecule 5 (CEACAM5). The new constructs were produced recombinantly in Escherichia coli (E. coli) and purified using affinity chromatography. Moreover, the results demonstrate bispecific binding with high affinity towards serum albumin and CCL7 and CEACAM5 respectively, while the ADAPT variants targeting VEGF-A remain to be further developed. Lastly, the importance of different amino acids for structural and binding properties of one CEACAM5 binder are stated. It reveals that the target binding relies on hydrophobic interactions which also can be connected to its poor structural attributes. Accordingly, this project adds new insights about the ADAPTs which can be useful in research towards future clinical applications aimed to improve cancer treatments.