A multivalent antibody assembled from different building blocks using tag/catcher systems: a case study.

The field of therapeutic antibodies and, especially bi- or multispecific antibodies, is growing rapidly. Especially for treating cancers, multispecific antibodies are very promising, as there are multiple pathways involved and multispecific antibodies offer the possibility to interfere at two or more sites. Besides being used as therapeutic, multispecific antibodies can be helpful tools in basic research. However, the design and choice of the most appropriate multispecific antibody format are far from trivial. The generation of multispecific antibodies starts with the generation of antibodies directed against the desired targets and then combining the different antigen-binding sites in one molecule. This is a time-consuming and laborious approach since the most suitable geometry cannot be predicted. The SpyTag technology is based on a split-protein system, where a small peptide of said protein, the SpyTag, can bind to the remaining protein, the SpyCatcher. An irreversible isopeptide bond between the SpyTag and the SpyCatcher is formed. A related Tag-Catcher system is the SnoopTag-SnoopCatcher. These systems offer the opportunity to separately produce proteins fused to the tag-peptides and to the catcher-domains and assemble them in vitro. Our goal was to design and produce different antibody fragments, Fab domains and Fc-containing domains, with different tags and/or catchers as building blocks for the assembly of different multivalent antibodies. We have shown that large multivalent antibodies consisting of up to seven building blocks can be prepared. Binding experiments demonstrated that all binding sites in such a large molecule retained their accessibility to their corresponding antigens.

Trastuzumab in the treatment of elderly patients with early breast cancer: Results from an observational study in Germany.

BACKGROUND: In elderly patients with HER2-positive breast cancer, few data on efficacy and toxicity of adjuvant trastuzumab treatment exists since older patients were in general excluded from large randomized studies. This prospective observational study aimed to confirm the beneficial findings from pivotal trials in age cohorts ≥65 years. MATERIALS AND METHODS: There were no restrictions for recruitment with respect to age or concomitant/sequential adjuvant medication. Long-term relapse/survival status of the patients was assessed once a year. RESULTS: Among the 3940 evaluable patients enrolled between 2006 and 2012 at 339 institutions, 507 were aged between 65 and 69 years, with another 507 patients ≥70 years. Elderly patients suffered from significantly more advanced primary tumors. Preceding or concomitant chemotherapy showed decreasing aggressiveness with patient's age. Trastuzumab treatment was stopped prematurely in only 11% of the elderly, but more often than in younger patients (p=0.0008). With 453 events hitherto reported, elderly patients did not exhibit an inferior relapse-free survival when adjusted for other relevant prognostic factors (hazard ratio: 1.01 per year; p=0.24). Three-year overall survival was significantly lower in the population older than 64 years than in younger patients (94.2% vs. 96.8%, p=0.0011). CONCLUSIONS: To our knowledge, our population of elderly patients treated with adjuvant trastuzumab is the largest analyzed so far. The beneficial long-term results were comparable to those in the younger cohorts. Although the risk of cardiotoxicity increased significantly with age, it also remained manageable in older patients. Thus, chronological age alone should not preclude HER2 antibody treatment.