An effort by Amgen ($AMGN) to extend the use of its kidney drug Sensipar did not pan out. The company said it did not get the results it sought in the late-state trials, Reuters reports. The study was established to determine if Sensipar would reduce the risk of death and cardiovascular problems in patients with chronic kidney disease and receiving dialysis. The company said that while there were fewer heart issues, the results were not statistically significant. If the results had been relevant, it could have extended the value of a drug that has already faced patent challenges. Story