III. Inhibiting EV uptake.

Several uptake mechanisms have been suggested for EVs, but there is insufficient information about the fundamental phases in EV trafficking and target specification. However, some studies showed that the uptake of EVs released from tumour cells can be reduced by diannexin, which can block phosphatidylserine, an important cell adhesion protein [76]. On the other hand, this concept can also be used in diseases other than cancer. For example, diffusion of HIV-1 to T cells could be reduced by targeting intercellular adhesion molecule 1 (ICAM1), which is exposed on EV-encapsulated viruses, thus preventing binding specifically to β2 integrin [77]. Moreover, another suggested mechanism of HIV-1 diffusion to non-haemato‐ poietic cells is by the horizontal transfer of chemokine receptors through EVs, which makes these vesicles valued targets for investigation [34].

IV. Blocking specific EV components.

Blocking specific signalling components of EVs was shown to have therapeutic significance. It was demonstrated that FASL-specific monoclonal antibodies targeting FASL1 displayed on EVs reduced tumour growth in a melanoma model [78]. However, this method may lack specificity and has negative impact on immune function. In the same way, the targeting of MET oncoprotein by RNAi to inhibit its active involvement into EVs was shown to be useful in reducing metastasis in late-stage melanoma [31].

All the above approaches highlight promising targets to develop small molecule therapeutics. Nevertheless, it is important to note that interfering with EV biogenesis could result in unwanted off-target effects, given that EVs are important for the regulation of normal core cellular processes and of course such approaches will need to be translated into a drug delivery system (DDS) that is capable of targeting specific EVs.
