Would a therapy that slowed progression by x% in y% of PwP pass clinical trials?

My worry is that potential therapies to slow the progression of PD may be being ignored. Let me explain why.

If you had a therapy that stopped progression for everyone, it would be easy to see that it was effective: after 6 months, or whatever, almost everyone in the control group would have declined, whereas all those taking the treatment would be no worse.

But what about a therapy that slowed progression by 10% for 50% of people and had no difference for the remaining 50%? Or one that slowed progression for women by 5%, but increased progression rates for men by 5%?

Not only do the latter cases have lower net benefit, but they increase the variance of the sample, making it harder to show statistical significance.

A better approach is, I believe, patient centred trials with high frequency testing.

John