Xcellerex, Inc. has initiated a Phase I trial of XRX-001, a prophylactic vaccine against yellow fever, a tropical virus disease that is often fatal. The vaccine is being developed to prevent yellow fever in people traveling to tropical countries where yellow fever is prevalent.

The currently available yellow fever vaccine is an attenuated, live vaccine with rare but potentially serious adverse effects. XRX-001 is an inactivated virus vaccine adsorbed to alum adjuvant, which is expected to significantly reduce the risks of serious and fatal adverse events that are associated with the live yellow fever vaccine. Also, according to the company, XRX-001 vaccine should not be subject to the precautions and contraindications of the currently marketed live vaccine, which includes immune suppression due to thymectomy, HIV/AIDS, cancer, treatment with immunosuppressive medications or radiation, and pregnancy.

The double-blind, controlled Phase I trial will enroll 60 healthy subjects divided into three groups. Two groups will receive two different dose levels of XRX-001 and the third will receive placebo. The primary objective of the trial is to evaluate the safety and tolerability of XRX-001 vaccine, and secondary objectives will assess the neutralizing antibody response. Also, a second parallel trial will compare the antibody response in those receiving XRX-001 to the currently-marketed vaccine.