Pfizer said on Tuesday its cancer drug Padcev, in combination with Merck's Keytruda, significantly improved survival rates in patients with muscle-invasive bladder cancer when administered before and after surgery.

The interim results from an ongoing late-stage trial of the combination therapy showed significant improvement in event-free survival – which measures how long a patient remains free from disease recurrence – and overall survival when compared to surgery alone, the company said.

"These latest results underscore the practice-changing potential of this combination in earlier stages of bladder cancer, where it has the potential to improve outcomes for even more patients," said Johanna Bendell, Pfizer's oncology chief development officer.

In muscle-invasive bladder cancer, the tumor extends beyond the inner lining and penetrates the muscular wall of the organ. It accounts for about 25% of all newly diagnosed bladder cancers and is a particularly aggressive form with a high risk of spreading, according to the National Institutes of Health.

Pfizer said it plans to discuss the trial results with global health authorities for potential regulatory filings.

The combination therapy leverages anti-PD-1 treatments that block the PD-1 protein to help the immune system combat cancer, where Padcev, an antibody-drug conjugate, targets specific cancer cells without damaging healthy ones.

Padcev, co-developed with Japan's Astellas, was approved by the U.S. Food and Drug Administration in 2019 to treat patients with a form of bladder cancer called metastatic urothelial cancer.

The drug brought $1.59 billion in sales last year, contributing about 2% of Pfizer's total revenue.