Pfizer (NYSE:PFE) stock was on the decline to start off the week as the company unveiled promising results from a clinical trial of one if its latest drugs, but the results weren’t good enough to ward off competition within the industry.

The drug manufacturer and distributer posted the results of its drug tafamidis, which is a drug that’s being developed to treat the rare illness transthyretin amyloid cardiomyopathy. The disease can be caused by old age or due to genetic reasons.

The results were generally positive and they show a lot of promise in helping to treat the cardiac illness in the short term. However, Wall Street analysts such as Stifel analyst Paul Matteis believe that there’s still “some room for improvement from TTR knockdown drugs, which we still think have a reasonable shot at being best-in-class over the long term,” he said.

The illness in question is caused as the protein transthyretin can come undone and result in amyloid deposits in a person’s heart. This disease can have negative repercussions on a person’s heart muscle, leading to heart failure.

Pfizer’s medication is geared to help stabilize the protein in order to thwart amyloid formations from occurring.

PFE stock fell about 1.9% during regular trading hours on Monday following the news. Shares were up a smidge after the bell.