One thing that could be done, even prior to having a real understanding of the number and nature of the various subtypes of the disease that may exist, is to use "adaptive trial design," in which the investigator keeps tabs on the clinical trial data as it comes in during the various phases. Adaptive trial design would allow, for example, the investigator to divide the clinical trial population for a particular therapy in two patient populations, such as responders and nonresponders. After the division, the clinical trials could continue with the responders. If, further clinical trial data confirms that the responders continue to show statistically significant improvement, the sponsoring company could then make a decision as to whether this subgroup was sufficiently large to continue to develop the product with the expectation of ending up with a profitable therapy.

Adaptive clinical trial design is being actively discussed by researchers and the scientific community. It is, perhaps, one way out of the box that current clinical trial design protocol for Parkinson's has created.