If Pbt2 is/were placebo, the probability of the Huntington trial "succeeding" is 41%.
I can visualize the first paragraph of the PR announcing the results of the trial: Either
a) [>41% probability] The primary outcome (safety and tolerability) met. Also, even though the trial was not powered to show efficacy, <insert a secondary endpoint> reached statistical significance (insert the p value) for <100mg or 250mg arm or "when both arms combined">. Furthermore, <insert 3-4 secondary endpoints> were close to reaching statistical significance (or also reached statistical significance) for <insert arms> (insert the p values less than 0.2). We are very excited. These results show that Pbt2 is an amazing drug.
b) [<59% probability] The primary outcome met. Also, even though the trial was not powered to show efficacy, <insert 2-3 secondary endpoints> were close to reaching statistical significance for <insert arms> (insert the p values less than 0.2). Furthermore, for subgroup of patients, <insert subgroup such as those younger than than 70yrs>, <insert a secondary endpoint> reached statistical significance (insert the p value) for <insert arm>. We are very excited. This result shows that Pbt2 is an amazing drug. However, we wish we had more more secondary endpoints and/or arms so that we could issue a PR like the first.
In my limited experience, Phase 2 trials from single drug companies very seldom fail.
PS. My estimate of 41% is based on 21 independent trials (7 x 3) assuming placebo vs placebo each with 2.5% chance of success. In actuality, it is slightly less as "both arms combined" is somewhat dependent to the chance of success in each arm.
