The principal developers of the third approach have stated that whole cell vaccines can stimulate the immune system better than oncolysates, Reviewed in [18,28,29,37,38,43,46,49,50,51] and that cells infected with a nonlytic strain of NDV will remain intact in the body long enough to generate these more effective immune responses. Reviewed in  It should be noted that the cancer cells used in the third approach are treated with enough gamma radiation to prevent further cell division, but not enough to cause cell death, either before or after they are infected with the nonlytic virus.[49,50,52,53,54,55,56,57,58] Reviewed in  This precaution ensures that patients are not given a vaccine that contains actively proliferating cancer cells.
Either a patient's own cancer cells (i.e., autologous cells) or cells from another patient with the same type of cancer (i.e., allogeneic cells) can be used to make oncolysates and whole cell vaccines. It is important to note that immune system responses similar to those obtained with oncolysates and whole cell vaccines may occur in patients infected with a lytic strain of NDV and that these responses would be expected to contribute to any observed anticancer effect.
To conduct human studies with viruses, vaccines, or other biological materials in the United States, researchers must file an Investigational New Drug (IND) application with the U.S. Food and Drug Administration (FDA). Biological materials and drugs have been held to similar safety and effectiveness standards since 1972. In an IND application, researchers must provide safety and toxicity data from laboratory and animal studies to justify the dose, the route, and the schedule of administration to be used in the proposed clinical studies. Among the safety issues to be addressed, researchers must demonstrate an absence of harmful contaminants. Most human studies of NDV as an anticancer agent have taken place outside the United States; therefore, they have not required an IND. At present, at least one group of U.S. investigators has filed an IND application to study NDV as an anticancer treatment. It should be noted that the FDA has not approved the use of NDV to treat any medical condition.
The NDV strains that have been evaluated most widely for the treatment of cancer are 73-T, MTH-68, and Ulster.[1,6,11,42,45,49,50,52,53,54,55,56,57,58,60,61,62,63,64,65,66,67,68,69,70,71,72,73] Reviewed in [22,51,74] Strain 73-T is lytic, and Ulster is nonlytic. Strain MTH-68 has not been classified, but it is assumed to be lytic.[1,6,66,75] Reviewed in [22,76,77] All three strains have shown little or no evidence of neurotropism (i.e., an ability to replicate efficiently in normal nerve cells or normal neural tissue).