GSK's daprodustat, given as a pill, is designed to displace injectable EPO products that are used widely in patients with chronic kidney disease. EPO, which boosts red blood cells, is also infamous as a doping agent in sport.
The new drugs work by copying the body's response to hypoxia, or low oxygen levels, by increasing the natural production of EPO in the kidneys.
GSK said on Thursday its two Phase III clinical studies would enrol a combined total of 7,500 patients with kidney disease.
The trials will look at daprodustat's effect on anaemia and also assess cardiovascular safety, given the heart risks associated with current injectable EPO.
AstraZeneca's roxadustat pill, which is being developed with FibroGen and Astellas, is already in a Phase III testing programme involving more than 8,000 patients.
In China, the trials have been completed and roxadustat is now set for regulatory submission.