Repoxygen
Clinical purposes
Repoxygen is the tradename for a type of gene therapy that induces controlled release of erythropoietin (EPO) in response to low oxygen concentration in mice. It is has been developed by Oxford Biomedica to treat anaemia. It is still in preclinical development and has not been extensively tested in humans.
It is constructed as a viral gene delivery vector carrying the human EPO gene under the control of a so-called "hypoxia control element" (“HRE”). The HRE is claimed to sense low oxygen concentrations and to switch a gene on in response. Repoxygen is designed to be delivered by injection into muscle and therefore to induce syntheses of EPO in the muscle tissue. Normally, EPO is synthesized in the kidneys.
Doping
Athletes could consider using Repoxygen as a means of increasing their number of red blood cells. Due to its alleged self-regulating properties it may be impossible to detect Repoxygen currently. Repoxygen is prohibited both in and out of competition under the World Anti-Doping Code 2006 Prohibited List.
The German track and field coach Thomas Springstein and Rashid Ramzi are currently suspected to have used Repoxygen.
Repoxygen's delivery vector has triggered immune response in several cases and resulted in at least one confirmed death directly related to the body's immune response to the viral protein delivery vehicle.
The self-regulating properties of EPO are highly touted in cases of defficit, however such a property actually makes it less effective to suppliment natural EPO levels in athletes, so there may be fewer gains but this can in theory keep EPO levels under the acceptable range in testing. Gains from traditional EPO doping is detectable in blood samples for a few weeks after injection, eventually dissipating; Repoxygen's prolonged effect (permanent DNA insertion) would not let an athlete "test clean" without gene down-regulation (not currently possible by drug injection, though DNMT studies are making man-made control of genes just over the horizon). A doping athlete using repoxygen is either cheating and will test out of range for EPO, or they're "trying" to cheat and don't get any benefit beyond natural varience and acceptable EPO testing levels.
Sports without doping tests or regulation hold the most allure for this product. EPO is up-regulated in anoxic environments such as high-altitude climbing; Repoxygen and other gene therapies may find "legal doping" applications in such sports. High-altitude mountain climbing (i.e. attempting to summit Death Zone mountain peaks without supplimental oxygen), or extreme deep diving (requiring one to hold their breath for several minutes while diving 100+ feet) are but two examples.