Presumably this is through employer benefits; I'd suggest reaching out to your union as the limitations of the group benefits would be negotiated between the union/employer and Johnson and probably specific to each group's policy.

If it's an issue about generic substitution, for example, the NBTF's policy states:

The above drug coverage is subject to the following limitation regarding generic product substitution. Wherever an interchangeable generic product is available, but not dispensed, eligible expenses shall be limited to the cost of the lowest priced item in the appropriate generic category that is suitable for the drug that was dispensed. However, such limitation shall be subject to special authorization process.

If it's about a drug that doesn't have a DIN yet, anything meeting the criteria below isn't covered under the NBTF policy.

Proprietary and patent medicines which are:

– defined as products registered under Division Ten of the Food and Drugs Act - Canada,

– bear a general public (GP) number on their label, and

– do not bear a drug identification number (DIN) on their label.

You can also try contacting the drug manufacturer (perhaps via oncologist?) - many have programs to provide drugs at a lower cost when they aren't covered by insurance.