One of Pfizer's (PFE 0.62%) blockbuster drugs has effectively flopped in a late-stage combination therapy trial. The company announced on Friday that the results of a Phase 3 trial for its Ibrance (Palbociclib) breast cancer drug in the treatment of early stage breast cancer were disappointing.

The results of the study indicate that, when used in combination with post-surgery endocrine therapy, it "is unlikely to show a statistically significant improvement in the primary endpoint of invasive disease-free survival (iDFS)."

The trial was conducted on male and female patients with HR-positive, HER2-negative early stage breast cancer.

Cancer attacking an organism.

Image source: Getty Images.

This is a quite a setback for Pfizer, which had hoped to unlock even greater commercial potential for the successful Ibrance in early stage breast cancer treatment. It said it was "disappointed" in the study's results.

In spite of that, the pharmaceutical giant insists that the Ibrance setback won't divert it from its growth path. In its pres release announcing the news, the company wrote that "[g]iven the continued breadth of our marketed portfolio and strength of our pipeline, our growth projections are not reliant upon any individual marketed medicine or pipeline opportunity."

Pfizer added that it still believes it will be able to produce a compound annual growth rate of 6%, at a minimum, through 2025. Ibrance should continue to be a significant factor in that; in the company's first quarter of fiscal 2020, revenue for the drug in the U.S. and emerging markets grew by 17% on a year-over-year basis. 

Investors weren't taking the latest news on Ibrance well, however. At one point, Pfizer's shares sank by 6% in after-hours trading following the announcement on Friday; this was a steeper fall than that suffered by the broader stock market during the day.