Otsuka Pharmaceutical said it is ending a collaboration with Akebia Therapeutics over the investigational chronic kidney disease-associated anemia drug vadadustat.

Otsuka said it pulled out of the partnership because Cambridge, Mass.-based Akebia received a Complete Response Letter from the FDA in March regarding the New Drug Application. The FDA said that the data did not support a favorable benefit-risk assessment for vadadustat in dialysis and non-dialysis patients. The agency also flagged safety issues, including the risk of drug-induced liver injury.

The two companies entered into their partnership in December 2016 for the U.S. market and expanded it in April 2017 to include other parts of the world.