In Vitro Assessment of Binding Affinity, Selectivity, Uptake, Intracellular Degradation, and Toxicity of Nanobody-Photosensitizer Conjugates.

Photosensitizers have recently been conjugated to nanobodies for targeted photodynamic therapy (PDT) to selectively kill cancer cells. The success of this approach relies on nanobody-photosensitizer conjugates that bind specifically to their targets with very high affinities (kD in low nM range). Subsequently, upon illumination, these conjugates are very toxic and selective to cells overexpressing the target of interest (EC50 in low nM range). In this chapter, protocols are described to determine the binding affinity of the nanobody-photosensitizer conjugates and assess the toxicity and selectivity of the conjugates when performing in vitro PDT studies. In addition, and because the efficacy of PDT also depends on the (subcellular) localization of the conjugates at the time of illumination, assays are described to investigate the uptake and the intracellular degradation of the nanobody-photosensitizer conjugates.

Assessment of the In Vivo Response to Nanobody-Targeted PDT Through Intravital Microscopy.

Methods that allow real-time, longitudinal, intravital detection of the fluorescence distribution and the cellular and vascular responses within tumor and normal tissue are important tools to obtain valuable information when investigating new photosensitizers and photodynamic therapy (PDT) responses. Intravital confocal microscopy using the dorsal skinfold chamber model gives the opportunity to visualize and determine the distribution of photosensitizers within tumor and normal tissue. Next to that, it also allows the visualization of the effect of treatment with respect to changes in vascular diameter and blood flow, vascular leakage, and tissue necrosis, in the first days post-illumination. Here, we describe the preparation of the skinfold chamber model and the intravital microscopy techniques involved, for a strategy we recently introduced, that is, the nanobody-targeted PDT. In this particular approach, photosensitizers are conjugated to nanobodies to target these specifically to cancer cells.

Development and assessment of the efficacy and safety of human lung-targeting liposomal methylprednisolone crosslinked with nanobody.

Glucocorticoid (GC) hormone has been commonly used to treat systemic inflammation and immune disorders. However, the side effects associated with long-term use of high-dose GC hormone limit its clinical application seriously. GC hormone that can specifically target the lung might decrease the effective dosage and thus reduce GC-associated side effects. In this study, we successfully prepared human lung-targeting liposomal methylprednisolone crosslinked with nanobody (MPS-NSSLs-SPANb). Our findings indicate that MPS-NSSLs-SPANb may reduce the effective therapeutic dosage of MPS, achieve better efficacy, and reduce GC-associated side effects. In addition, MPS-NSSLs-SPANb showed higher efficacy and lower toxicity than conventional MPS.

Role of caplacizumab in the treatment of acquired thrombotic thrombocytopenic purpura.

Acquired thrombotic thrombocytopenic purpura is a rare blood disorder with a high early mortality rate, if untreated. Standard of care plasma exchange and glucocorticoids have dramatically improved survival. However, additional advancements are necessary to further decrease mortality. Caplacizumab-yhdp (Cablivi®) is the first Food and Drug Administration-approved treatment indicated for adult patients with acquired thrombotic thrombocytopenic purpura, in combination with plasma exchange and immunosuppressive therapy. However, there are considerable risks associated with the use of caplacizumab and they must be weighed against the benefits of the medication.