Mexico performs a very small number of Phase I clinical trials since Mexican regulation forbids paying patients for their participation in clinical trials, something that does not happen in other countries such as the US, England or some countries in Asia. Phase I trials are performed with healthy patients who are sometimes only motivated to participate in the trials due to the economic benefits, but as these are unavailable in Mexico there is little interest from the general public to participate. Phase II to IV studies involve sick patients throughout several stages of the disease who are willing to participate in the trials as it provides a potential cure for their diseases.