On 2015 Aug 15, John Tucker commented:

A major shortcoming of the paper is a lack of detailed comparison of the characteristics of published and non-published trials. Although the authors speculate that non-publication of large studies may result from a "discrepancy between observed and desired results" or the desire to protect intellectual property, a quick survey of the unpublished trials listed in the supplementary material shows that most involved drugs that never received regulatory approval for marketing. Thus the leading cause of non-publication appears to be simple irrelevance.

On 2015 Aug 15, John Tucker commented:

A major shortcoming of the paper is a lack of detailed comparison of the characteristics of published and non-published trials. Although the authors speculate that non-publication of large studies may result from a "discrepancy between observed and desired results" or the desire to protect intellectual property, a quick survey of the unpublished trials listed in the supplementary material shows that most involved drugs that never received regulatory approval for marketing. Thus the leading cause of non-publication appears to be simple irrelevance.