RE: The drug, considered to be pharmaceutical giant Merck and Co.’s most recent blockbuster product, is only approved to be used for certain advanced kinds of cancers; in addition to advanced melanoma cases like Carter’s
Here's what I'm trying to understand --- why can't it be approved for ALL cancers regardless of stage? Why does one have to go through chemotherapy first, fail and then as a last resort try this cure? What is the FDA's rationale?
Can Anybody who understand the process explain this?
Blocking any metabolic pathway has large and frequently unforeseeable long term side effects, as it's a rare pathway which is used for only one specific thing and nothing else. They are
almost all interconnected. So there is that consideration.
Secondly, cancer is not a single disease, but a class of diseases with similar symptoms but not similar causes. This drug relies on the bodies own immune system as an integral part of the treatment - so any cancer involving the immune system - leukemia, kidney, liver, thyroid, and bone - will not respond to the drug at all.
Finally, in order for the immune system to identify and destroy cancerous cells once the PD-1 pathway is blocked, there has to be sufficent cells present to trigger an immune response. As they are your own cells, just defective, the trigger is a lot higher than for foreign intruders.