Nearly five months after Lance Armstrong announced with great fanfare that he was returning to cycling and would subject himself to a strict and transparent individual antidoping program, that program has been abandoned without ever beginning.

Don Catlin, the prominent antidoping scientist who was supposed to run Armstrong’s program, said Wednesday that they had decided earlier in the day to part ways, without Catlin’s analyzing a single blood or urine sample from Armstrong. The program was too complex and too costly, Catlin said, and the decision to terminate it was mutual.

“In the real world, when you try to implement a program as grandiose as what you had in mind, it just becomes so complicated that it’s better not to try,” Catlin said, adding that a contract with Armstrong had never been signed. “We’re all disappointed, but it’s just not going to be possible.”

Armstrong’s agent, Bill Stapleton, said that Armstrong would continue to be tested by the internal antidoping program of his professional cycling team, Astana. That program is run by Rasmus Damsgaard, a Danish antidoping research scientist. Stapleton said that Damsgaard had tested Armstrong, a seven-time Tour de France winner, about two or three times since December.