International people are not specifically excluded, however it is a small trial that will probably enroll fully locally in Washington DC and Maryland, so it will be difficult for people outside that area to get a slot before it is filled.
The trial sites are solely responsible for recruiting patients that qualify for the study, so AGT is not involved in the patient selection process. Please refer to ClinicalTrials.gov for information on these trial sites. I don't think there is a restriction on patients being U.S. citizens, but it would be difficult to participate in the study if you are not located in the DC/Baltimore area, and if you are not a patient of one of those hospitals. Also, please consider that the trial sites may have their own patients already.
The Phase 2 (assuming it is approved but the FDA) will probably be in more locations throughout the U.S. Depending on results, future human trials may open up internationally as well.