Very nice and useful interpretation and Implications discussed by one of the senior medical Oncologist - as follows:
We need understand the reasons why dose was changed from 2 mg per kg to 200 mg fixed dose
Initially 50 mg vial was there but later it was withdrawn
For obvious reasons
Now if u have 2 mg per kg dose for 75 kg man, it comes 150 mg
With 50 mg and 100 mg vial , it was easy to give
Now that 50 mg vial is withdrawn, for 150 mg dose , one has to use 2 vials of 100 mg and that will lead to wastage of 50 mg
As drug is covered by insurance in America, hospital do not want to use the 50 mg remained from 100 mg vial ,for the other patient, as they have no profit from it
So 50 mg has to be thrown off .
Now to get rid of this problem ,merc got rid of 50 mg vial and 2 mg per kg dose schedule
They keep fixed dose of 200 mg 3 weekly so that 100 mg 2 vials can be used for all pts and more vials are sold per patient
Now another intresting point is , there is another schedule of 400 mg every 6 weeks
Half life of drug is 3 weeks
So 6 weeks schedule would be enough
And if that is made 4 mg per kg 6 weekly , which means 300 mg for 75 kg man , one cycle will need 3 vials of 100 mg and hence inspite of having only 100 mg vial , one vial less will be needed per cycle and that wil save lots of money.
Also this will negate need of 50 mg vial .
The pharmacokinetic studies have already shown that 2 mg per kg is equal to 200 mg 3 weekly for receptors occupation
And 4 mg per kg is equal to 400 mg 6 weekly for receptor occupation
So the best solution for dosing problem without getting 50 mg vials, and subsequent drug wastage , is to have
4 mg per kg 6 weekly dose
Thats the best for pharmacy economics as well as pharmaco kinetics of pembro .
And for patients too .