I don't understand why pioglitazone was "found useless for Parkinson's" when the results showed a mean change in UPDRS score after 44 weeks of:
15mg dose: 4.42
45mg dose: 5.13
placebo: 6.25
Since for UPDRS low scores are good, both sizes of dose were better than for placebo.

There is the possibility that the results do not show statistical significance, but that is not the same as showing the drug is useless. There is the possibility that the trial had a minimum expected improvement (say a UPDRS difference of 4 points) which was not met. But again that is not the same as proving uselessness.

I think we are in danger of throwing out potentially useful therapies. I'm now 10 years post diagnosis so a therapy that had only slowed down my progression by 10% would have made a big difference for me.

In general, what are the chances that a new therapy would pass a clinical trial which this profile:
x% improvement in y% of people and z% worsening in the rest.

John