William Blair analyst John Kreger downgraded Aratana Therapeutics to Market Perform from Outperform. In the last month the company disclosed two senior leadership departures while its activist investor disclosed a significant reduction in ownership, Kreger tells investors in a research note. The analyst says these events lower his conviction in both the ongoing commercial progress of Entyce and in the steps to find a strategic partner. The stock could be range bound as investors weigh the positives of gradual sales gains for Entyce and Nocita with the negatives of gradual dilution from new capital needs, contends the analyst.