Not sure what the pants are made of but try spray oven cleaner then wash was usual. Got paint out of a pair of jeans that otherwise would have been trash. I figured they were lost, so what did I have to lose. LOL My sister used it occasionally on her greasy work uniforms after I tested it. It is still my go too for heavy grease stains.

This will not get out ink, but I have also had great success with an older bottle of hair spray - SUGAR is my go to for red wine or blood, sucks it all up - then vacuum - amazingly removes it all!!!!!

Grandma's Secret, it comes in either a small squeeze bottle or a larger spray bottle. My DH left an inkpen in his shirt pocket and it got all over some of my light colored clothes. I treated my blouses several times and washed them, eventually all of the ink came out.
Sharon