US FDA flagged problems in critical Tavneos trials, leading to Health Canada to advise doctors to halt starting the medication.
The warning issued after the FDA identified data problems.
A medical journal has withdrawn a paper that used the trial data, stating the numbers were conflicting.
The New England Journal of Medicine has also retracted pivotal findings from studies connected to Tavneos.
Regulators in both countries are reviewing the drug's safety and efficacy.
Amgen has still commented, keeping the issue unresolved.
The developments spark concerns for patients as of now receiving the treatment.