US FDA flagged problems in major Tavneos trials, leading to Health Canada to advise doctors to stop starting the medication.
The warning issued after the FDA found data problems.
A medical journal has withdrawn a paper that used the trial data, noting the numbers were conflicting.
The New England Journal of Medicine has also withdrawn pivotal results from studies connected to Tavneos.
Regulators in both countries are reviewing the drug's safety and efficacy.
Amgen has not yet commented, leaving the issue unresolved.
The developments spark concerns for patients as of now receiving the treatment.