Please don't take any of my comments as legal advice but I have been through this nonsense before. The unfortunate thing about these lawsuits is that if you try to fight/defend them through traditional means, you almost always end up spending more than what you would have spent in an early negotiated settlement (especially when your time and stress are factored in). Unless the defendant has a lawyer friend willing to work at a discounted rate, $35k will not get him very far at all, especially if this goes to trial.

Who is this expert hired by GTX? He appears to be a startup guy himself so it's surprising he would get involved in this. It might be worth reaching out to him to confirm 1) that his signed statement is legitimate and 2) try to reason with him.