US FDA flagged issues in critical Tavneos trials, raising Health Canada to advise doctors to stop starting the medication.
The warning issued after the FDA reported data issues.
A medical journal has withdrawn a paper that used the trial data, saying the numbers were unreliable.
The New England Journal of Medicine has also removed pivotal results from studies connected to Tavneos.
Regulators in both countries are examining the drug's safety and efficacy.
Amgen has still commented, keeping the issue unresolved.
The developments raise concerns for patients as of now receiving the treatment.