There is a apparently a little confusion about what a patent does and what it does not.

What a patent does:

A patent gives you the right to prevent others from practising your invention.

What a patent does not:

A patent does not give you the right to practise the invention in your patent.

The above statements are not conflicting.

In the case of Pfizer's patent (application), if the patent ends up being granted, Pfizer then has the right to prevent Resverlogix from selling RVX-208 as a treatment for Friedrichs's ataxia. However, should Pfizer decide to pursue this rather rare indication using RVX-208, they would need a license from Resverlogix, as Resverlogix has a (matter of composition) patent on RVX-208. Thus, if anyone wants to sell RVX-208 - no matter which indication you might come up with - they would need to have a license from Resverlogix - and if Resverlogix would want to pursue Friedreich's ataxia using RVX-208, Resverlogix would need a license from Pfizer (provided the patent is granted).

Does that make sense?