Functionalized nanobodies for cancer therapy

Cancer treatment is complicated by the high similarity between cancerous and healthy tissue. New anti-cancer drugs, the monoclonal antibodies, act on one specific molecule/process and thereby minimize side effects. Despite that these monoclonal antibodies are highly specific and harbor multiple modes of action, their effectiveness is hampered by limited tumor penetration. This led to the development of antibody fragments that are smaller in size, but with similar specificity. One promising set of antibody fragments with favorable biochemical and physical properties are derived from heavy-chain-only antibodies in camelids and known as nanobodies. This thesis focuses on the therapeutic applications of nanobodies for cancer treatment. Towards this end, two methods were developed for the site-specific functionalization of nanobodies. These approaches enable the conjugation of (small) biomolecules including fluorescent markers and toxic drugs, or onto drug delivery platforms. In addition, two nanobody-based medicines were evaluated as anti-cancer therapy. The potential of nanobodies for cancer treatment was exemplified for the epidermal growth factor receptor (EGFR) because its role has been well established and is associated with a number of cancers. EGFR-targeted liposomes with zinc phthalocyanine were employed for photodynamic therapy and demonstrated increased efficacy in vitro compared to their non-targeted counterparts. Another approach involved the delivery of immunotoxins towards EGFRvIII-positive glioblastoma’s and showed efficient cell death after treatment. Next to EGFR-positive cancers, this methodology can also be applied for other surface proteins which provide selective tumor targeting. Numerous of applications are therefore imaginable where site-specifically functionalized nanobodies could contribute to the treatment of cancer