US FDA flagged issues in major Tavneos trials, causing Health Canada to advise doctors to stop starting the medication.
The warning issued after the FDA found data issues.
A medical journal has withdrawn a paper that used the trial data, noting the numbers were inconsistent.
The New England Journal of Medicine has also withdrawn pivotal data from studies linked to Tavneos.
Regulators in both countries are assessing the drug's safety and efficacy.
Amgen has still commented, leaving the issue unresolved.
The developments trigger concerns for patients still receiving the treatment.